Etching and Other Terms

Abrasive Clean

Dry or wet abrasive powders used as a method of cleaning material surfaces. Applied as dry powder uder gas pressure. SiC is a major compound for general processing.

Abrasive

The abrasive used for grinding and polishing.

Acid Etch

Controlled preferential attack by acid on a metal surface for the propose of revealing structural details.

Acid Slurry Etch

A form of mechanical polish lapping where an acid is mixed an abrasive.

Adhesion Etch

Etching of thin films to relieve stress and evaluate the film failure, as lifting, peeling crazing, etc.

Aged Etch

Has two meanings: 1.) any solution mixed and allowed to stand for a specified period of time, 2.) any solution used more than on time may be called an aged or used solution.

Agitation Etch

Any solution used with some form of physical movement, for example: rod in solution, hand or electrically operated (rotational stirring).

Alcohol Etch

Alcohols are normally considered cleaning or rinsing solutions rather than etchants, but they will attack certain alcohol soluble materials.

Alkali Etch

Alkaline solutions are greater than pH 7, are base or basic chemical solutions according to Sorenson scale. They mey be in liquid form or in solid form. Alkalies also are used as molten fluxes for preferential etching, such as on silicon, or as growth for high temperature type single crystals, such as garnets and ferrites.

Alloy Etch

Any solution used to clean an alloyed joint or structure, such as water for flux removal. The use of an alloy material acting as the etching agent, such as an AlSi (5%) for froming a pit in a single crystal wafer.

Air Etch

Alternative therm for atmospheric atch. Actual ecthing is due oxygen, salt (chlorine), water moisture, or other contaminants in the air such sulfur, acids, smog.

Angle Etch

There are two meanings: 1.) specimen: the part is lapped at a secified angle an then etched. Used to measure diffusion depths, or 2.) containers: the etch conatiner is placed on a rotating spindle. Specimen is mounted on discs of Teflon, placed face-up on container bottom, wuth ething done at rotation speeds of between 130 to 300 rpm.

Anisotropic Etch

Another term for preferential etch. Any etch that attacks crystallographic planes at different rates.

Anodic Etch

Electrolytic etching with the specimen as the anode for cleaning, removal, polishing, structuring and may include switching from anode-to-cathode. Development of microstructure by selective dissolution of the polished surface under application of a direct current.

Argon Etch

Primary used to: 1.) Argon ion, Ar+, cleaning or etching of surfaces, secondary for etching of single crystal argon.

Artifact

A false microstructural feature that is not an actual characteristic of the specimen; it may be present as a result of improper or inadequate preparation, handling methods, or optical condition for viewing.

Atmosphere Etch

Air, nominally 24% oxygen and 75% nitrogen with water vapor, contaminating gases will attack all known inorganic materials with time.

Attack-Polishing

Simultaneous etching and mechanical polishing.

Atomizer Etch

Use of an atomizer to apply a fine mist/spray to etch or clean a surface.

Autoclave Etch

A closed metal container capable of handling high pressure (low pressure, medium pressure, high pressure, cryogenic).

Barrel Etch

A barrel-like container or bottle for cleaning and etching, used closed and rotated horizontally on roller bars, open-topped and mounted on a rotationg spindle similar to an angle ecth beaker, or close-topped on a shaker table.

Base Etch

Therm used in three ways: 1.) Any chemical solution with pH greater than pH 7 is chemical base. 2.) The first etch solution used in a clean/etch sequence or the primary solution in such sequence. 3.) A specific etch mixture with established characteristics against which other solutions are evaluated.

Basic Etch

Any solution with pH > 7 as established hydroxyl-ion concentration. The chemical compound is a base as against an acid.

Basket Etch

The etching of wafers, dice or other parts in some form of a basket holder that is submerged in an etch solution; passed through an etch solution; held in hot vapor, or held for spraying.

Batch Etch

The etching or cleaning of any two or more wafers, specimens or parts in a solution at one time.

Beaker Etch

Any open-topped conatiner used to hold an etch or cleaning solution. Quartz, Pyrec, polyethylene, or Telflon beaker from 200 to 1000 ml are common.

Blank Etch

Any etch solution used on a relatively small flat part, such as 1 x 1 x 0.010 inch ceramic or metal substrate. Also called a flat or coupon.

Boiling Bead Etch

Ceramics, glass, or metal beads of various sizes placed in the bottom of an etch beaker to introduce and control a boble/agitation action of a hot to boiling solution.

Bomb Etch

A metal conatiner capable of holding higher pressurem, and used to hold an etching or cleaning solution/gas.

Bottle Etch

Use as a closed bottle for etching.

Bright Field Illumination

Bright Field (BF) illumination is the most common illumination technique for metallographic analysis. The light path for BF illumination is from the source, through the objective, reflected off the surface and returning through the objective and back to the eyepiece or camera. This type of illumination produces a bright background for flat surfaces with the non-flat features (pores, edges, etched grain boundaries) being darker as light is reflected back at an angle.

Brine Etch

Natural or artificial salt water used as an ecth solution. Not common; some test evaluation on metals and compunds in corrosion study.

Brush Etch

To use of a brush to apply an etch solution to a material surface.

Bulk Etch

After mechanical lap and polish of a material surface, the surface is etched to remove the residual subsurface damage down to the undamaged bulk metal.

Cap Etch

Special terms spplied to Solid State processing and etching single crystals with thin films.

Cascade Etch

Though often called etching, more commonly a method of dinal water quenching and washing following ann etch period, with reference to the container structure used: a rectangular trough divided into three or four progressively lower sections, usually fabricated from polyethylene sheet or simular high purity plastic.

Cathodic Etch

Electrolytic etching is normaly anodic, but switching from anode to cathode as a deplating and removal system, not an actual method of etching. In metallography is cathodic etching: Surface removal by bombarding with accelerated ions (1-10 kV) in vacuum.

Caustic Etch

An alkali or hydroxide solution with pH > 7.

Centrifuge Etch

Rapid spinning motion of a part during etching or cleanning. A photo resist spinner has been used for acetone cleaning during photo resist application and etching of semiconductor wafers with the holder platen rotating at about 3500 rpm.

Chemical Etch

General expression for all developments of microstructure through reduction and oxidation process (redox reactions).

Chem/Mech Etch

Chemical/Mechanical etching is being more and more widely used in a single crystal wafer processing to remove residual subsurface damage introduced by previous cutting, lapping or polishing steps.

Channel Etch

The etching of a groove into surface. Used in selective structuring of a single crystal devices.

Cleave Etch

The etch polishing or cleaved single crystal wafer surface to remove residual cleavage steps.

Cleaning Etch

Any solution or gas used to clean a surface with minimum etch removal of the material.

Cold Etch

Any solution used between about 2-10 oC. Development of microstructure at room temperature and below.

Conditioning Etch

Any solution used to prepare a surface for subsequent processing. Very common in the plating of metals, such as zincating aluminium before metal deposition.

Contamination Removal Etch

Any solution used to clean a surface of unwanted solid material, such as dirt, oil, or grease, etc.

Control Etch

Any etching for specified time period or at a particular temperature.

Controlled Etch

Electrolytic etching with selection of suitable etchant and voltage resulting in a balance between current and dissolved metal ions.

Cool Etch

Any solution used between about 10-20 oC.

Corrosion Etch

The attack or alteration of any material surface from the action of a solid, liquid or gas.

Coupon Etch

Etching of a specimen cut as a flat form from sheet material.

Cover Etch

The part to be etched is slowly lowered into the BRM (bromine-methanol) solution, etched, then slowely withdrawn through the pure methanol "cover" to quench etching action without exposure to air.

Crucible Etch

The use of graphite, ceramic, or high temperature metals, such as platinum, as a cup to hold an etching solution.

Cryogenic Etch

The use of cryogenic liquids as an etching medium, such as liquid chlorine, at - 102 C. Also refers to the use of cryogenic liquid as a chilling agent for other acid solutions, such as liquid nitrogen.

Crystal-Figure Etch

Discontinuity in etching depending on crystal orientation. Distinctive sectional figures form at polished surface. Closely related to dislocation etching.

Crystallographic Etch

Any solution that will develop single crystal plane structure by preferential attack. Specific solutions have been developed on most metals and metallic compounds during evaluation development, and include etching spheres (convex), and pits (concave) surfaces.

Cup Etch

Any open container when used to hold an etching solution may be referred to as a cup. Usually a small ceramic, graphite, or high temperature metal (Pt, Mo, Ti, Ta) used as a crucible for either an etch solution or solid molten metal, and may include a cap or cover.

Cutting Etch

The use of an etch solution, alone, or a wire soaked in the etch to cut material.

Cutting Force

The specific pressure between sample surface and abrasive grain surface.

Cyclic Etch

Etching with sequential periods of time. May include water or alcohol quenching between etch cycles, or the removal to air and return to etch without quenching.

Damage Removal Etch

Any etch solution used to remove either the surface or subsurface damage present or induced by previous abrasive lapping, etc. It is usually a slow polish type etch, such as bromine: methanol that both remove the damaged zone and polish simultaneously.

Decoration Etch

The use of a metal thin film diffused or alloyed into a single crystal surface to enhance defect structure for observation.

Defect Etch

A general term denoting the etch development of any bulk or surface anomaly in a material whether or not it is single crystal, colloidal, amorphous or crystalline in structure.

Definition Etch

Term used in two ways: (1) an etch used to develop a particular structure, such as fine-line definition, and (2) a solution developed for a particular purpose - a definitive etch.

Degreasing Etch

Usually a solvent for removal of oils or greases, rather than etch solution, although an etch may be used. Laboratory glass is etch cleaned in a solution of H2SO4:K2Cr2O7, and soda-lime glass plates used for chrome photo resist masks are scrub cleaned with soap.

Deep Etch

Macroetching; etching preliminary to macro examination, intended to develop gross features such as segregation, grain flow, cracks and porosity.

Descaling Etch

An etch used to remove heavy contamination from metal surfaces. Term widely used in metal processing, but not in Solid State development where most materials are supplied as nominally clean parts.

Dicing Etch

Any etch solution used to cut and separate discrete devices or units from a semiconductor or other type material in wafer or thin sheet form.

Differential Interferance Contract

Differential Interferance Contract (DIC) - is a very useful illumination technique for providing enhanced specimen features. DIC uses a Normarski prism along with a polarizer in the 90 degrees crossed positions. The two light beams are made to conincide at the focal plane of the objective, thus rendering height differences visible as variations in color.

Dip Etch

The etching or cleaning of a specimen for a very short period of time - the "time" is difficult to define but can be arbitrarily said to be between 1-3 sec.

Dislocation Etch

The preferential etch development of structure in a single crystal material that can be related to crystallographically oriented defects associated with bulk structure or surface defects. Dislocations can be introduced during ingot growth; by heat treatment, alone, or in conjunction with alloying, diffusion, epitaxy, cutting, and lapping; by controlled bending or striking of a surface in defect studies; or inadvertent damaging from process handling, etc. Etching of exit points of dislocations on a surface. Depends on the strain field ranging over a distance of several atoms. Crystal figures (etch pits) are formed at exit points. For example, etch pits for cubic materials are cube faces.

Dissolutionment Etch

In the broadest context the term dissolution or dissolutionment etch refers to any solution that will dissolve a material. In the study of single crystals, it is used with specific reference to the etching of spheres to finite crystal form with development of crystal facets (planes) on convex surfaces.

Double Etching

Use of two etching solutions in sequence. The second etchant stresses a particular microstructural feature.

Drip Etch

To apply a single, or series of droplets on a surface. Usually applied to a limited area.

Drop Etch

Term has been used in three ways: (1) the free etching or cleaning of a part by physically dropping free into the solution; (2) placing of a drop of solution on a surface to etch and/ or plate a semiconductor p-n junction; develop pinholes in oxide/nitride thin films, etc., and (3) dropping of a part down through a column of solution with distance, time, and temperature used to control fabrication, e.g., the shot tower technique used in sphere forming.

Drop Etch

Placing of a drop of etchant on the polished surface. Suitable for precious etchants.

Dry Chemical Etch

The use of an ionized gas for cleaning or etching surfaces. Ar+ ion cleaning of single crystal wafer surfaces has become a standard technique in processing.

Dry Etch

Not considered a true form of etching, yet drying can affect the surface or bulk of a specimen. Water removal from a surface can cause crazing, cracking or leave stains. Bulk removal can alter both chemical formula and crystal structure. Heat treatment or annealing and hydrogen firing are two methods. The latter a method of surface cleaning in a reducing atmosphere.

Dry Ice Etch

Solid CO2 used as a direct etching medium. Also used as a mixture with alcohols or acetone for chilling another etch solution, or for removal of water vapor from process gases.

Electrolytic Etch

The use of electric current applied to any etching or cleaning solution. he specimen being etched in the anode and a metal (such as Cu, Pb, Fe) as the cathode. Development of microstructure by selective dissolution of the polished surface under application of a direct current. Variation with layer formation: anodizing.

Electron Beam Etch

E-beam or EB vacuum systems are used for metal evaporation from a rotatable copper hearth containing from one to four crucibles. The beam is magnetically bent up and around into the crucible, a 270 o beam being a standard, today. The E-beam can be used to etch remove and vaporize metals on a specimen surface at controlled rates by varying power input. Also used to anneal a specimen (heat treatment), in addition to being a method of metal evaporation.

Etching

Controlled preferential attack on a metal surface for the propose of revealing structural details.

Electrolytic Polishing

A metallographic preparation procedure where metal is preferentially dissolved from high points on an anodic surface by passage of an electric current through a conductive bath, to produce highly reflecting surface.

Etch Figures

Markings formed on a crystal surface by etching or chemical solution and usually related geometrically to the crystal structure.

Etch Rising

Pouring etchant over tilted surface until desired degree of attack is achieved. Used for etchants with severe gas formation.

Eutectic-Cell Etching

Development of eutectic cells (grains).

Evaporation

The vaporization of a material by heating it, usually in a vacuum. In electron microscopy this process is used for shadowing or the produce thin support films by condensation of the vapors of metals or salts.

Extraction

A general term concerning chemical methods of isolating phases from the metal matrix: 1.) acid extraction-removal of phases by dissolution of the matrix metal in an acid. 2.) chlorine extraction-removal by formation of a volatile chloride, 3.) electrolytic extraction-removal by using an electrolytic cell containing an elctrolyte which preferentially dissolves the metal matrix.

Etch/Clean Sequences

See clean/etch sequences under composition.

Etch-Stop

An etch solution that will attack one material but not another in a multilayer thin film structure. Hot H3PO4 will etch remove Si3N4 much more rapidly than SiO2, such that the oxide can work as an etch-stop mechanism. The method is used in structuring devices, and in the removal and thinning of layers for TEM study.

Failure Etch

Any solution use in the study of device failure, and used to etch develop, surface stain or otherwise expose the causes of failure.

Fatigue Etch

Specific solutions used on metals and their alloys in the study of material failure due to fatigue, such as cracking from bending or crazing from atmospheric corrosion. This is a major test evaluation method of study applied to metals and alloys with specimens prepared by metallographic techniques for observation after the test period.

Figure Etch

Any form of defect or structure developed in a surface by etching, regardless of the type etchant, e.g., gas, liquid, solid. Figures also can be formed by temperature, pressure, or direct flame. As a pressure formed figure, called a "percussion figure" on mica, (0001) surfaces developing as a six-rayed star. Star line pattern representative of bulk prism plane directions and used for orienting the micas.

Finish Etch

The final etch used on a material surface. Term primarily used in the metals industries, and can apply generally or to a specific etch or technique developed to produce a particular surface finish.

Finite Form Etch

Preferential etching of single crystal spheres of any metal or metallic compound to produce a solid with crystallographically oriented exterior planes that are the fast etching planes of a convex surface. Planes developed vary with solution mixture, as cube, (100); octahedron, (111); dodecahedron, (110); or tetrahexahedron, (hkO) as most common forms, e.g., also called finite crystal form etching, and primarily applies to materials that form in the isometric (cubic) system.

Flame Etch

Use of a propane torch or similar gas torch to produce etching action on a surface. Has been used to develop surface etch figures on high melting point temperature metals and alloys. Also used for surface cleaning of metals and their alloys during brazing operations.

Flash Etch

Any very rapid etch applied for a short period of time. It can be a liquid solution or an electrical spark. The latter used in spectrographic analysis.

Force

The total force with, which the specimen holder is pressed against the grinding/polishing disc in unit Newton (N).

Flat Etch

Either to etch a surface to be planar and flat, or etching of a material sheet in the form of a "flat".

Float-Off Etch

The removal of thin film layers from a surface for microscope study by TEM, SEM, etc. Etch solution attacks the substrate, but not the film.

Flood Etch

To rapidly cover a specimen surface with an etching or cleaning solution, usually with reference to washing or quenching acid reaction, rather than etching. An etching container is flooded with water to stop etch action.

Flush Etch

To cover a surface with a moving liquid etch solution. Used as a light surface cleaner, or to produce an etch-washed pattern for a decorative effect.

Flux Etch

Use of a molten metal or solid chemical compound for etching. May also refer to the use of a flux, such as borax, in metal alloying and brazing, and solutions used to clean and remove residual borax after joint fabrication.

Form Etch

Either etching a material to a specific shape, or etching of a particular shape. Spheres me etched to finite crystal form; rectangular bars are control-thinned as electronic reeds; silicon is via hole pattern etched as an inking mask; many metal shim stocks are electro formed or pattern etched as evaporation masks; tantalum is etch formed as an antenna, etc.

Forming Etch

Preferential, selective, or electrolytic etching of a specimen to a bulk shape, or structuring a surface by etching pits, via holes, channels. Diamond is etched with a saw-tooth structure as a filter element.

Free Etch

The etching of specimens by dropping them loose into a solution without being held in any manner.

Freeze Etch

The use of a solution below OC to effect etching action, or, the quenching of a material from an elevated temperature into a liquid bath solution.

Fume Etch

Use of hot acid or solvent vapors for etching or cleaning action, hot HCl/H2 vapors are used in epitaxy systems for general cleaning of quartz tubes, graphite susceptors and specimens.

Gas Etch

The use of a gas to produce etching action in its molecular form, such as argon, hydrogen, nitrogen, etc. It usually includes heat and/or pressure.

Gate Etch

Specialized term denoting channel etching for the active area of a Schottky Barrier device, such as a field effect transistor (FET). The channels are either wet chemically etched or electron photolithographically etched on the submicron width scale.

General Etch

Any etch solution can be so called when used without other specific definition, such as a general removal etch; and there is an etch solution with the name General Etch.

Graphic Etch

A repetitive pattern of figures etched onto a surface. Such patterns can be controllably produced for decorative effects or developed in nature - meteorites have a distinctive etched structure called Widmanstatten.

Gravity Etch

A highly specialized method of etching where the specimen is subjected to either a positive (+) or negative (-) gravitational force by centrifugal action during preferential etching to form controlled structures. Brass and gallium arsenide have been via hole and pit patterned in this manner. A specimen may be dropped down through an etch solution column for a controlled distance for forming or cleaning.

Grinding

The removal of material from the surface of a specimen by abrasion through the use of randomly oriented hard-abrasive particles bonded to a suitable substrate, such as paper or cloth, where the abrasive particle size is generally in the range of 60 to 600 grit (approximately 150 to 15 microns) but may be finer.

Grit/Grain Size

The grit or grain size (microns), of the abrasive used.

Grain-Boundary Etch

Development of intersections of grain faces with the polished surface. Because of severe, localized crystal deformation, grain boundaries have higher dissolution potential than grains themselves. Accumulation of impurities in grain boundaries increases this effect.

Grain Contrast Etch

Development of grain surfaces lying in the polished surface of the microsection. These become visible through differences in reflectivity caused by reaction products on the surface or by grain differences in roughness.

Groove Etch

In single crystal wafer structuring of devices, the etching of a channel in surfaces. It may be as a "V" groove, have a bottom curvature of known radius; as a saw-tooth series of ridges; have vertical side walls with a flat bottom, and side walls may be specific crystal planes.

Halogen Etch

Refers to a chemical class of elements as etching agents: fluorine, chlorine, bromine, and iodine.

Heat Etch

The use of heat only, to effect an etching or cleaning action. Used under vacuum conditions to flash clean specimen surfaces. Used in air to oxidize a specimen surface.

Heat Tinting

Formation of colors (interference colors) in air or other gases, mostly at elevated temperature. Heating of a specimen on a hot plate in air to produce oxide colors. Used in the study of metallographic specimens. A crystalline material varies in color by rate of oxidation of individual crystallite grains according to their crystallographic plane orientation. A single crystal material or alloy can be differentiated by phase structure or internal crystallographic plane directions by similar color variation. In an alloy mixture or similar specimen, different metal or compounds can be determined by their characteristic oxide color when he'at tinted for a specific time. Single crystal spheres of metals and compounds have been widely studied by controlled furnace oxidation in the study of oxidation kinetics and growth rates related to internal crystal plane location and orientation.

Heavy Etch

Any etch solution used to remove a large volume of material. Measuremcnt is done by mils of surface removal, or by total specimen gram-weight loss.

Hot Etch

Any solution used for etching or cleaning above room temperature as either a liquid or gas, and may be shown in F, C, or K. Also shown as warm, hot, or boiling. Development and stabilization of the microstructure at elevated temperature in etchants or gases.

Ice Etch

Solid ice has been used as an etching medium in the sense of the freeze-out of a hot, liquid metal poured on the ice surface. Mixed with water or alcohol it is used to cool other etch solutions and, along with snow, has been used as a constituent in formulating a series of "cold etches" for specific temperature levels. Also can refer to the etching of single crystal ice specimens grown under cryogenic conditions in cold cryostats.

Identification Etching

Etching to expose particular microconstituents; all others remain unaffected.

Immersion Etch

Complete submersion of a specimen in a liquid etch solution, or in a molten flux solid rhemical solute. It is the most common form of etching as wet chemical etching (WCE) or electrolytic etching (EE), which are two of the Etchant Formats used in the next section. (Dry chemical etching (DCE) is the third format.) Method in which a microsection is dipped into etching solution face up and is moved around during etching. This is the most common etching method.

Immersion Etching, Cyclic

Alternate immersion into two etchants: (1) actual etchant; (2) solution used to dissolve layer formed during process 1.

Inclusion

Foreign material held mechanically, usually referring to non-metallic particles, such as oxides, sulfides, silicates, etc.

Interference

The effect of a combination of wave trains of varous phases and amplitudes.

Induced Damage Etch

Preferential etching to develop deferts or structure in a surface that has been subjected to some form of damage. Such damage may be a controlled scratch or a point of damage introduce by a diamond-type stylus to develop specific defects, or to initiate the etch forming of a pit, via hole, channel, etc. Also has been used with reference to residual subsurface damage remaining after cutting or mechanical lap and polish. Such damage being removed by chem/mech polishing or straigbt chemical etching in Solid State device fabrication.

Initial Etch

Any solution that is the first in a series, or the first etch applied irl a specific material process.

Ion Etch

A gas in its ionized rather than molecular state used to clean or etch a surface. RF plasma N2 or 02 cleaning systems are widely used in Solid State material processing. Argon, as ionic Ar, also is widely used in Solid State processing to final clean surfaces under vacuum immediately prior to metallization and compound growth or deposition, and can introduce subsurface damage. Other ionic gases, such as helium (He), xenon (Xe), etc., are used in material irradiation damage and thin film adhesion studies. Electron irra-diation from a TEM microscope or an electron-beam in vacuum system; lasers, for annealing or alternating materials; and nuclear particles have all been used as forms of ion etching.

Ion Etching

Surface removal by bombarding with accelerated ions (1-10 kV) in vacuum.

Irradiation Etch

The use of ionized gases or radiation particles to affect etching action. May also be used to induce damage into surfaces in the broader study of irradiation effects. Note that a single crystal, when irradiated, will revert toward the noncrystalline, amorphous state, and the reverse - an amorphous material will tend toward single crystal or the crystalline state.

Isotropic Etch

Another name for a polish etch solution. The etch attacks all crystal planes at an equal rate, producing a flat, planar surface. The opposite is anisotropic (preferential) etching. The terms anisotropic and isotropic originally applied to the propagation of light through a solid mineral. They also are now used in dry chemical etching (DCE) with regard to shaping a pit, channel or via hole with ionized gases without reference to the polish (isotropic) or preferential (anisotropic) nature of a liquid etch solution.

Jar Etch

The use of any closed vessel for etching in which parts or specimens are immersed.

Jet Etch

A fine stream of liquid under pressure applied as an etchant, and most often for shaping the exterior of a solid specimen, structuring a material surface, etch cutting a hole through a wafer, etc. May be a single or multiple jr.t system with or without electric current. There are jet systems combining etch/cut action for slicing or dicing material with high velocity gas, steam, water, or an acid.

Junction Etch

As a semiconductor term, the development of a p-n junction by staining, etching or selective plating. In the heavy metals industry, weld joints can be developed or cleaned by etching or light sandblasting. In the plating and cladding industries, etching to develop interface joints between layers can be done with a jet.

Key Etch

A primary etch solutinn within a clean/etch sequence, or any solution applied in a processing step that is considered a fundamental solution.

Krypton Etch

The use of ionized Krypton, Kr+, as ail etch or material damaging agent by irradiation. The use of uapor pressure change to etch single crystal Krypton grown under pressure and cryogenic vacuum conditions.

Lapping

The abrasive removal of material using graded abrasive particles in a loose form as in liquid slurry on a platen.

Laser Etch

Use of electrons propagated by light at a controlled frequency and power level to effect an etching action. Several types of lasers are used to etch channels and other structures for operational Solid State devices; for material cutting, such as preparing circuit substrates; as annealing to increase crystallitc size on dendritic crystals, or in conversion of carbon to a diamond-like-compound (DLC).

Layer Etch

As applied in Solid State processing, the etch development of epitaxy multilayer structures in device fabrication or in material studies. As a more general term, the etch removal of a specific layer of material from a dissimilar material. It may be total removal as in oxide or nitride stripping from a semiconductor surface, or selective removal through a photo resist or similar surface coating to develop patterns for subsequent device fabrication.

Lift-Off Etch

A specific technique developed to remove thin film metallization from a photo-lithographically prepared wafer surface. Wafers are soaked, sprayed and/or lightly scrubbed with a plastic foam Q-tip in acetone. The acetone dissolves the photo resist layer used for patterning which loosens excess metal by lift-off, and exposes the metallized pattern for further device processing. This is a separate and distinct operation, though similar to the float-off technique.

Light Etch

The term has been used in two contexts: (1) as a physical term to differentiate between light-medium-heavy etching; or in the sense of a slow, minimum removal etch, and (2) the use of light alone, or in conjunction with solutions to enhance etching reaction or for selective plating action. White light most widely used, such as a strobe light for semiconductor p-n junction plating with copper.

Light Figure Etch

The use of preferential etchants to develop surface etch pit and dislocations on the surface of a cut single crystal ingot face or wafer and used to crystallographically orient the surface by reflected light. This is standard practice in the processing of smgle crystal ingots of all materials. It should be noted that many single crystal ingots can be cleaved into wafers on preferred fracture planes, which does not always require etching to obtained surface figures for light figure orientation (LFO), After etching face-cut silicon ingots in boiling KOH, 5 min, as an example, the ingot is mounted on a ceramic block, then on an x-y-z positioner and a pinhole light is reflected off of the surface back into a black box.

Light Figure Orientation Etch

The same as the upper item. As initially developed in Solid State semiconductor ingot processing, the etching of silicon in hot KOH solutions; germanium in KOH:I2, or acid solutions, such as CP4. The reflected surface defect pattern are used to orient the ingot for wafer slicing.

Lineation Etch

In semiconductor development the term was originally applied to distinctly aligned dislocation patterns associated with stress induced during the rotation/pull growth of Czochralski (CZ) single crystal ingots. The patterns are very distinctive on (111) and (100) oriented wafer surfaces: a series of over-lapping dislocations reducing in size from the wafer periphery toward wafer center, and disappearing before reaching the wafer center. On (111) surfaces, as three lines at 120 and associated with the bulk <211> directions; whereas on (100) surfaces, four such lines at 90 and associated with <110> bulk directions. With improved growth control, this form of defect rarely observed today.
Any crystallographically oriented line segment - representative of slip in a single crystal surface - may be termed lineation or slip. Where a series of such line segments are closely parallel - called stacking faults (SFs). This type of defect can be introduced by processing - oxidation, diffusion, epitaxy, ion implantation, and is often associated with oxide and nitride thin films. For these latter, HF:CrO3 preferential etchants have been tailored for stacking fault study.

Liquid Etch

Any wet chemical etch (WCE) solution used to effect etch action. Also the use of a solid chemical molten flux etch, such as KOH pellets at 360 C.

Long Etch

A time period for etching, as against a short or dip time period. Solution is either a slow etch on the material, or a cleaning solution with an extended soak time. This latter is common in metal processing, such as in soak etching or conditioning a surface prior to plating.

Long-Term Etching

Etching times of a few minutes to hours.

Loose Etch

Any solution used where parts are dropped free and not held in any way in the solution during the etch period.

Low Etch

Applied with specific reference to the level of a solution above a part being etched, where insufficient covering acid will not block the in-diffusion of atmosphere over the open container. If the solution level is too shallow, it also can cause erratic etching results.

Lubricant

The liquid used for cooling and lubricating.

Macro Etch

Defects and structure observable on a surface with the unaided eye after etching. The term is widely used in the metallographic preparation of metals and alloys in the metals industries, and in geologic study of thin sections. It has occasionally been used with reference to preferential etching of semiconductor and other single crystal surfaces. Controlled etching of the surface of a metallic specimen, intended to reveal a structure which is visible at low magnification (not usually greater than 10 times).

Magnetic Etch

Not a real etching method, yet has been used in two ways: (1) magnetic powder has been brushed on wafer surfaces of ferromagnetic materials to develop domain structure, such as barium titanate and ferrites; (2) iron or carbon powder brushed on a preferentially etched wafer surface to accentuate defects and etched patterns. There are magnet-stir hot plates where a Teflon or plastic-coated magnet is dropped into the solution, then solution rotation and heat controlled by the hot plate dials. Barium titanate, being fabricated as an ultrasonic transducer, is electrically (magnetic flux) poled in water to orient domains.

Matte Etch

A surface finish etch used for decorative purposes on metal surfaces, such as copper or nickel. The surface has a low-profile grain-like structure with a dull sheen, and can be as a semi-matte finish.

Medium Etch

Used in two ways: (1) with regard to time, as a slow, medium, or fast etch, and (2) with regard to solution strength, as weak, medium, or strong.

Melt Away Etch

The separation of a thin film from a substrate for microscope study by heat liquefying and removal of the substrate. Etch removal of a metal thin film or alloyed pre-form, wire, etc., to observe the pit formed in the material surface by the metal. Semiconductor wafers with alloyed p-n junctions have been etched from the back to observe the buried junction-front in the bulk wafer. Sodium chloride, (100) substrates have been heated to the liquid state in order to remove a thin film for TEM study, rather than the usual use of water to dissolve the substrate/film interface.

Melt-Back Etch

A specialized Solid State term relative to wafer surface etching during epitaxy growth, such as using indium on indium phosphide, InP, or gallium on gallium arsenide, GaAs during liquid phase epitaxy (LPE). The method is used to clean the surfaces to reduce the growth of defects in the epitaxy film.

Mesaetch

The etching of a roughly cylindrical column or pylon on a single Crystal surface as a p-n junction device structure. In Solid State, as a single mesa, it is the mesa diode. As an array of mesas in the fabrication of SCRs, they are elements for power distribution and control in the electrical operation of the device. Mesas are commonly formed with a slightly preferential etch such that the mesa side slopes have a degree of crystallographic orientation. Using dry chemical etching techniques, the mesa sides can be more cylindrical without crystal facets.

Metal Etch

In the broadest sense, any solution used to etch any metal more commonly, the use of a liquified metal as an etch medium on high temperature, chemically inert metals, such as molybdenum, tantalum, or titanium. Occasionally refers to the metallizing of a material surface with in-diffusion to decorate defects.

Metallographic Etchig

Term primarily used in the preparation of metals and alloys as specimens for defect and structure analysis using preferential etches. Common in the metals industries and in geology, and most Solid State companies maintain a metallographic laboratory for material inspection and evaluation of processing. The etch can be macro- or micro-etch as a size definition.

Metallography

That branch of science which relates to the constitution and structure, and their relation to the properties, of metals and alloys.

Metallurgical Etch

Not common, but any etch applied to a metal or alloy specimen with reference to the field of metallurgy or metallurgical engineering as a science. Also with reference to the use of a metallurgical microscope for material observation.

Micro Etch

Any defect, figure, or structure etched on a surface that cannot be easily observed by the unaided eye, and requires a microscope for proper viewing. Both macro- and micro-etch are terms widely used in the study of metallographic specimens in general metal processing, not as often used in Solid State processing. Development of microstructure for microscopic examination. Usual magnification of more then 10 times.

Microstructure

The structure of a suitable prepared specimen as revealed by a microscope.

Milling Etch

In Solid State it refers to the use of an ion milling vacuum system where ionized argon (Ar+) or nitrogen (N+) is used to etch remove and pattern thin film metallization on circuit substrates or active devices. In general metal processing, it occasionally means the use of a lathe or cutting mill for a combination of cutting, etching, or shaping of a part, and may be as an electrolytic etch with the lathe head as the cathode.

Minimum Etch

An etch used for a short period of time, or one that removes little or no material during the etching period.

Mist Etch

The use of an etch as a spray of finely divided particles as from an atomizer. The method has been used for final etch cleaning of a surface; to fine-tune and optimize electrical characteristics of an exposed p-n junction semiconductor device; or to develop defects, structure, or figures in a surface for optimum clarity observation. Used in metallographic specimen etching to develop fine structure of crystallites, phases etc.

Molar Etch

Any solution mixed by its molecular weight.A Molar solution may be used as the etching solution by itself, or be only one constituent of an etch mixture.

Molten Flux Etch

Any metal or compound liquidized at or slightly above its melting point without the inclusion of water or other liquid solvent.

Multiple Etching

Treatment of microsection sequentially with specific reagents attacking distinct microconstituents.

Named Etch

Many etch solutions have a number, letter, chemical, individual's name, or a combination of such.

Native Oxide Etch

Almost all inorganic metals and compounds become surface passivated by an oxide when exposed to air. Such oxides are called native oxides as they are a normal attribute of the surface and not artificially produced. The removal of this type of oxide can be critical to metal processing, such as preparing aluminum surfaces for plating as well as copper, nickel, iron, and steels. It is of major importance in preparing semiconductor wafers for etching, metallization, diffusion, etc., as such residual oxides can affect device characteristics. Any etch solution used to remove such oxides is called a native oxide removal etch to differentiate it from a solution used to etch an oxide thin film or material, such as titanium dioxide, TiO2 or quartz, SiO2, and called an "oxide etch". It should be realized that a "native" oxide only occurs under natural atmospheric conditions, even though it is called such in Solid State processing where residual surface oxide remains after chemical treatment.

Network Etching

Formation of networks, especially in mild steels, after etching in nitric acid. These networks relate to subgrain boundaries.

Neutral Etch

A very slow, nonreactive etch, when used as a cleaning solution, or the use of water as a pH 7 neutral wash or quenching solvent.

Nitride Etch

There are several artificially grown nitride compounds, such as silicon nitride, Si3N4 and aluminum nitride, A1N. The metal industries use a nitridization process to condition metal surfaces and the Solid State industry is developing and applying both oxide and nitride surface thin films in processes. In either case, any etch solution used to remove or pattern a nitride is called a nitride etch, and many also can be used on oxides.

Normal Etch

An etch solution mixed on the basis of the total valence of the metallic radical ions in solution. To obtain the number of grams of a compound for a Normal solution: divide one gram-molecular-weight (1 mole) by the total valence number of the element and radical.

Oil Etch

Petroleum base oils can act as etchants on some metals, even though they are normally only thought of as coolants in metal cutting, and similar processing. For critical materials, such as semiconductor wafers and assembly or test parts, such oil coolants with various additives for rust prevent, foaming, etc. can be severely degraded because of chemical attack, residual films, and other anomalies, such that silicones are used as replacement liquids for petroleum oils.

Optical Etching

Development of microstructure under application of special illumination techniques (dark field, phase contrast, interference contrast, polarized light).

Optical Interferometry

Is a technique that provides precise details of a materials surface topography. The simplest interferometer employs the interference between two beams of light. One beam is focused on the specimen and the second beam on an optically flat reference surface. The two reflected beams are then recombined by the beam splitter and pass through the eyepiece together. The two beams reinforce each other for those points on the specimen for which their path lengths are either the same of differ by an integral multiple of the wavelenth, n x lambda. The beams canel for path differences of n x lambda. Todays interferometers provide quantitiative 3-dimensional surface topography information.
The two most common optical interferometry techniques include - phase shifting interferometry (PSI) which uses a PZT to shift the optical path of the objective and vertical scanning interferometry (VSI) which changes the focus range of the objective. The main differences between PSI and VSI are that PSI has a higher z-axis resolution, whereas VSI has a larger scan range. PSI and VSI can also be combined to provide both high surface resolution and a larger scan range.

Orientation Etch

A preferential solution used to determine the single crystal orientation of a specimen surface by development of surface etch pits.

Oxide Cleaning Etch

A solution developed to clean an oxide surface with minimum or no removal. It can be acid, alkali, or solvent.

Oxide Etch

Any solution used to etch a metallic oxide material. See the immediately following terms for special case applications.

Oxide Removal Etch

In Solid State processing, often refers to removal of a native oxide on a material surface prior to further processing. It also is used where a deposited oxide thin film (SiO2, Al2O3) is being pattern etched or removed.

Ozone Etch

Ozone; O3, is an extremely strong oxidizing agent. In Solid State and some metal processing it is used, by itself, as a surface cleaner. Caution should be exercised as concentrations greater than 1 % in air can be hazardous to health. There are ozone producing commercial cleaning systems used in metal processing for material surface cleaning. Similar units are used in movie theaters or other commercial offices and buildings as an air freshener, and for cigarette smoke removal.

Particulate Etch

Any solution used to remove a material matrix and expose embedded particles without affecting the particles. This is common in some ore processing operations where gangue material is separated, and in some material studies. The etch may expose the particulate, only, or be used to remove the particles for separate microscope study.

Passivation Etch

The term is used in two ways: (1) a solution developed to remove a passivating thin film from a surface, such as a native oxide, or (2) a solution that will introduce a surface film passivation. An iodine solution has been used on diamonds in the latter case as pas-sivation against etching with H3PO4, and an l2:Me0H rinse applied as an ionic surface contamination removal system on silicon wafers prior to diffusion.

Pattern Etch

Any etch solution that will develop structure in or on a surface and there are several different applications and methods: (1) to develop defects in surfaces; (2) to differentiate between elements, structure, or minerals in a mixture material; (3) to etch through a masking layer, such as photo resist patterned thin film oxides to remove the oxide down to the substrate in the desired pattern; (4) etching via holes, or (5) circuit pattern etching of substrates.

Phase Etch

Common to metal and metal alloy etching of steel in the etch development of alpha-, beta-, or delta-phase structure, and the recognition of martensite, carbide, and similar crystal structures.

Photo Resist Etch

Photo resist lacquers, such as the AZ- series, COP-, or PMMA types used in device and circuit fabrication of semiconductor devices, have their own solutions called developers, and used after UV exposure of the resists in fabricating patterns. The developers are designed for each type of commercial photo resist formulation, many contain hydroxide, such that caution should be observed if the material being processed in particularly vulnerable to attack by alkaline solutions.
Note that in removing photo resists before or after metallization of the specimens or wafers, the most widely used solvent is acetone (a ketone) by soaking, spraying, or light scrubbing of the specimen surfaces.

Physical Etching

Development of microstructure through removal of atoms from surface or lowering the grain-surface potential.

Pickling Etch

Term common in metal processing and plating. Metal surfaces are soak-cleaned for conditioning, such as for removal of scale, or other type contamination.

Pinhole Etch

Small, roughly circular defects in a deposited thin film are referred to as "pinholes" and may or may not go completely through the film. Any solution or method used to locate and observe such pinholes is called a pinhole etch. Such pinholes can be created by con-tamination on a substrate surface, be due to insufficient cohesion within the growing thin film, or from entrapment of particles in the film. Oxide and nitride thin films are particularly prone to pinholing in Solid State processing, and are the subject of much study. The term also is applied to the etching of a controlled pinhole, such as for thickness measurement of the film, diffusion depth profiling, or observation and study of epitaxy layer structures.

Pit Etch

A preferential etch used to develop dislocations or surface damage pits in single crystal wafers or similar specimens as wet chemical etching (WCE). This includes controlled damage pit development as a device structure. Dry chemical etching (DCE) through a photo resist, metal, or oxide/nitride thin film mask, as well as WCE, also for device fabrication. Note that dislocation pits conform to crystallographic structure and bulk plane directions, such as the sharp triangular pit on a (111) wafer surface, and do not increase in size to any extent with extended etching; whereas a surface damage pit does not conform to crystal planes and directions, expand in size with extended etching with a flat pit bottom that may be heavily terraced, and will disappear when the bulk, undamaged material surface is reached. Un-damaged bulk surfaces can be recognized by their usual high reflectivity, and common near1-mammillary and near-hexagon structure, particularly recognizable on (111) oriented surfaces. The (100) wafer bulk surface is more block-like in structure, coincident with the square out-line dislocation and surface etch pits.

Planar Etch

A polish etch that produces a very flat, highly reflective surface. Now a major surface finish for three-dimensional layered electronic device and circuit substrate structuring.

Plane Etch

Preferential solution used to develop a crystal facet, or plane in a single crystal material. Occasionally with reference to etching a planar surface.

Plasma Etch

The use of ionized gas particles to effect cleaning or etching. Either RF or DC plasmas are used, RF more common in microwave, high frequency electronic device fabrication.

Polar Etch

Any etch used on a polar material, such as the compound semiconductors and, in particular, the (111) oriented surfaces. Gallium arsenide, as an example: the positive (111)Ga [(111)A] surface vs. the negative (111)As[(111)B] surface show different etching phenom-ena. One surface will etch preferentially with defects; whereas the opposed surface, usually the negative (111)B, will be erratic, and it is difficult to develop an etch solution that will equally polish both surfaces. Note that in compound semiconductors there also may be different electronic characteristics.

Polarity Etch

Any solution used to develop the preferential etching characteristics of polar compounds, such as GaAs, InP, AlSb, or their associated trinary and quaternary forms.

Pole Etch

A specialized term applied to the etching of magnetizable structure in materials such as barium titanate, Ba2TiO2, where the magnetic domains are aligned by polarization with electrolytic solutions and a magnetic flux. Garnet memory devices as a computer chip are similarly poled. The term also is applied in the etching of single crystal spheres for finite crystal form, when the solution produces only crystallographic "pole" figures at axial points, rather than developing exterior facets (planes) as a finite crystal solid form.

Polishing

A mechanical, chemical, or electrolytic process or combination therof used to prepare a smooth reflective surface suitable for microstructure examination, free of artifacts or damage introduced during prior sectioning or grinding.

Polish Etch

Any etch solution that attacks a material surface at an equal rate in all crystal plane directions without regard to their orientation. This is the opposite of preferential etching. In the Solid State single crystal etching, and much metal etching, a polished surface is required in the fabrication of devices and parts, such that polish etching is of great importance, and a major criterion in processes. It also is now called isotropic etching.

Potentiostatic Etching

Anodic development of microstructure at a constant potential. By adjusting the potential, a defined etching of singular phases is possible.

Precipitation Etching

Development of microstructure through formation of reaction products at the surface of the microsection (see also staining).

Preferential Etch

Any etch solution that will attack crystallographic planes at different rates, and produce structure as controlled by those planes. It is the opposite of polish etching. Much of the structuring and selective etching of semiconductors wafers and similar materials as devices is done with preferential etching, as well as in crystallographic study of single crystals. Such device processing includes formation of pits, channels, "V" grooves, via holes, saw-tooth structures. This was the only method of selective structuring semiconductor devices (wet chemical etching or electrolytic etching) until the fairly recent advent of dry chemical etching. Preferential etching also is now called anisotropic etching.

Pre-Plate Etch

Any acid, alkali, salt, or alcohol solution used to clean or condition a material surface prior to plating.

Pressure Etch

The forming of material, or alteration of a surface by direct pressure, alone, and may include heat or a gas atmosphere when a furnace or vacuum is used. Natural pressure produces etch figures on meteor surfaces during atmospheric entry; six-rayed star percussion figures are formed on (0001) oriented mica sheets by striking; controlled point pressure damaging of single crystal wafer surface is used in forming etched pits or grooves in device structuring.

Printing

A method in which a carrier material is soaked with an etchant and pressed against the surface of the specimen. The etchant reacts with one of the phases. Substances form which react with the carrier material. These leave behind a life-size image. Used for exposing particular elements - for example, sulfur (sulfur prints).

Priming Etch

The term is applied with two meanings: (1) the type preparation of a surface prior to plating, such as a priming etch for conditioning, and (2) the adding of a small piece of the material to be etched to the etching solution prior to use. The latter method is used on highly reactive solutions, such as 1 HF:3 HNO3, to obtain an even etch rate from the beginning.

Primary Etching

Development of cast structures including coring.

Profile Etch

The term is used in two ways: (1) Selective etching of any "form of structure in or on material, and (2) profile etching. The latter includes etching through thin film or metal masks; etching to observe and measure diffusion depths; to study epitaxy layer structures. Many wafers are processed with (100) surface orientation and, for profile study of structures, are cross-sectioned by cleaving in a <110> bulk plane direction.

Pylon Etch

Any etch used to form vertical, roughly cylindrical structures on a surface. A slightly preferential etch will produce facetted side-wall slopes with WCE; whereas smooth, unfa-cetted walls can be fabricated by DCE etching.

Quality Etch

Applied with regard to the purity of acids and chemicals used, such as electronic grade vs. commercial grade liquids or gases.

Quantity Etch

The etching or cleaning of a number of parts at a single time, or the use of a large volume of solution.

Rapid Etch

Any fast etching solution as against a slow etch. As an example, the 1 HF:3 HNO3 mixture is the most rapid etch solution of this two-component etching system.

Raster Etch

Electron beam (E-beam) etching using high intensity electrons; electron lithography, where a computer is used for beam positioning and exposure of photo resist patterns; and laser etching may be referred to as raster etching or annealing, as has been irradiation with ionic gases or radiation with particles in the sense of using a controlled beam of energized particles, electrons, etc., to effect an etching action. The term relates to the raster tracking element of a computer screen.

Rate Etch

Used in two ways: (1) the time period for any solution required to obtain desired results, or (2) the physical reactivity time/rate of specific mixtures. The latter most important when using exothermic solutions. Determining etch rates is a major factor in processing.

Reactive Ion Etch

A form of dry chemical etching (DCE) where one or more of the ionized gases is a reactive gas, such as BCl3 used in etching aluminum oxide surface films. Common acronym: RIE. This form of etching is increasingly used for selective etch structuring of electronic devices that contain layered epitaxy and metallized structure. Note that there are a number of specifically designed dry ionized gas etching systems with their own special acronyms, though all operate in a similar manner.

Reproducibility

Once a preparation method of sample has been developed and adjusted, it should produce exactly the same results for the same material, every time it is a carried out.

Redoxetch

Originally referred to as oxidation-reduction reaction, where one acid is a reducing agent, and the other an oxidizer. HF:HNO3 solutions are an atypical example, where HF acts as the reducer and HNO3 the oxidizer. As a REDOX etching system, the term is applied to selective etching with pH control of the solution.

Relief Etch

Etching of any form of structure on a surface. It can be as a raised mesa, pit, channel, or via-hole completely through the material.

Removal Etch

Any solution that will dissolve and reduce the thickness or weight of a material. All etches are removal type and many are classified by their etch-rate of removal.

RF Plasma Etch

Another term for dry chemical etching (DCE), and used as a general term for any form of ionized gas etching or cleaning.

Rolling Etch

Any solution used with a rolling motion. Single crystal spheres are etch polished in a beaker held at about 45 and hand swirled to produce a slow rolling action of the spheres.
Occasionally used with reference to a boiling solution that has a rolling or roiling motion. It also has been used with regard to allowing a specimen to roll and tumble down an incline during an etching period, or the etching of an extruded, rolled metal sheet to include etching in or against the rolled direction.

Rotational Speed (rpm)

The speed with which the grinding/polishing disc is rotating.

Rough Etch

Has been applied with two meanings: (1) general reduction in thickness or size without regard to surface finish and measured in mils of depth removed from a surface or by total gram-weight loss of a specimen and (2) a controlled etch to roughen a surface. Glass microscope slides have had one side roughed with HF vapor etching to improve thin film gold adhesion for TEM study of the film growth and structure characteristics, and some metal parts arc surface finished with a named roughness, such as a matte or satin finish.

Sand Etch

The term has been applied with reference to the use of a dry abrasive to effect removal action with the abrasive under gas pressure (nitrogen) applied by spray or jet. The method also is used to clean, roughen, or condition a surface. Abrasives are usually considered as lapping and polishing compounds, although fine jets of sand have been used to fabricate screws, to drill holes through material, or form cavities (pits) in a surface. The use of S.S. White Dental Unit was one of the original methods used to dice silicon and germanium wafers, and the units are still used for sand cleaning of surfaces, e.g., bead blasting technique for cleaning metal parts.

Satin Etch

Specialized term used in the metal industry where an etch solution produces a surface finish that has the appearance of satin cloth. The surface structure contains variable length and width lines, roughly parallel with some cross-hatching, and with the reflective sheen of satin cloth. The method is called satin finishing, and is used as a decorative finish on copper, nickel, brass and other metals.

Saturation Etch

A solution containing the maximum amount of a dissolved chemical in water, alcohol or solvent at room temperature and standard pressure. If such a solution is mixed above room temperature, and under pressure^ it is called a super-saturated solution.

Saw (Acid) Etch

When wafers are cut from an ingot by a wire that is wetted with acid, it is called the acid-saw technique (AST). The wire can be of iron, SST, rayon, plastic thread, etc.
In cutting, lapping, or polishing a surface mechanically there is always a subsurface damaged zone remaining with damage depth determined by abrasive grit size and other factors. Solid State wafers, such as silicon or gallium arsenide, are often chem/mech polished with bromine-methanol (BRM) solutions to remove this damaged zone. This has been referred to as saw damage removal etching.

Scale Etch

Term used in metal processing where slow etch solutions are used to remove surface contamination - oxidation, oils, dirt - that are called "scale".

Seeded Etch

Any solution to which is added a small piece of the material to be etched. This technique is used with solutions that initially show a rapid rate of attack in the first few seconds, then a more controllable linear rate. A mixture of 1 HF:3 HNO3 is of this type. By initially seeding such a solution, allowing the piece to completely be dissolved, the etchant becomes more controllable for linear controlled removal.

Secondary Etching

Developmnet of microstructures deviating from primary structure through transformation and heat tretment in the solid state.

Segregation (Coring) Etching

Development of segregation (coring) mainly in macrostructures and microstructures of castings.

Segregate Etch

Any etch used to remove a matrix material to expose a paniculate or segregate embedded. This may be as a contaminant included during ingot growth or a new compound due to regrowth, such as is observed in fabricating silicides as blocking layers in Solid State devices.

Selective Etch

Either wet chemical etching (WCE) or dry chemical etching (DCE), where the solution or gas is used to structure a surface, or to remove specific material layers in a heterojunction/ heterostructure device. In the latter case, the etch will attack one material layer and not another, and by suitable masking of surfaces with a thin film oxide, photo resist, or metal, then exposing a pattern, pits, channels, via-holes, or other structure can be etched selectively.

Sequence Etch

A single solution, or a series of different solutions used in a consecutive order of etching steps. Clean/etch sequences are of this type, and can include vapor degreasing, etch removal of subsurface damage, acid etching, alkali etching, with water and/or alcohol rinses following etching, or the rinses as individual steps.
The term also is applied to the etching of different layers of heterostructure devices where different etch mixtures are used again consecutively.

Series Etch

Term has been used in two ways: (1) a single etchant used two or more times in sequence, such as in dip etching or (2) different acids, alkalies, and alcohols used in a sequence.

Shaping Etch

Any solution used to etch form a solid material. May be electrolytic etching, and term has been used with reference to electroforming.

Shim Etch

Either the etching of shim-stock material, such as thin nickel sheet pattern etching for use as an evaporation mask; or the etch thinning of a material to shim thickness, e.g., at or under about 0.010".

Short Etch

Any etch solution used for a brief period of time, as against a long period, such as a soak etch.

Short-Term Etching

Etching times of seconds to a few minutes.

Shrink Etching

Precipitation on grain surfaces. Shrinkage takes place during drying, which causes a cracking of the layer formed during etching. Crack orientation depends on the underlying structure.

Sizing Etch

In Solid State material processing the term applies to the etch reduction of physical size to a particular dimension* such as in thinning of a specimen for TEM microscope study. In general material processing, there is a gelatinous substance called "size", much like a weak glue which is used as a surface coating with applications similar to those in photolithographic processing with photo resist lacquers.
In paper manufacture, size is added to the pulp to prevent ink from running, and is the more accurate meaning, where tree rosins and alums are added as the sizing compounds.

Slosh Etch

Any etch solution used with either movement of the solution or the part.

Slow Etch

The removal rate of a solution as against a rapid or fast rate. Many polish etch solutions are designed to be slow for maximum planarity of surfaces, and for the prevention of erratic surface anomalies that can occur from a too rapid etch.

Slush Etch

Etches containing ice or snow as cold solutions.

Snow Etch

Some cold etch solution use snow as one constituent to establish a specific temperature. As a group, they are sometimes referred to as the "snow etches".

Soak Etch

A slow cleaning or etching solution where the part remains immersed for an extended period of time. Common to the metal and plating industries for surface preparation.

Solid Etch

The term has been used in two ways; (1) the etching of any solid material, or (2) molten flux etching with a liquified solid chemical compound, such as KOH pellets.

Solution Etch

A term used for wet chemical etching (WCE) where the etchant is a liquid; whereas dry chemical etching (DCE) uses ionized gases.

Solvent Etch

The use of a chemical solvent as a cleaning or etching solution as against an acid, alkali, or alcohol. A few metallic compounds can only be etched in a solvent.

Spark Etch

The use of an electric spark to generate an etching action, As a cutting method, called spark erosion; as a etching method an electrically activated wire loop in alcohol is used to observe pinholes in oxide and nitride thin films by the appearance of bubbles come from the substrate surface as the wire passes over in the alcohol solution. Metal spheres, both single crystal and polycrystalline, have been formed from chips of material by electrical sparking from a copper pot under argon, and spark vaporization of material from a surface is a standard method for spectrographic analysis.

Sphere Etch

The term has been used in two ways: (1) the slow polish etching of a material sphere, or (2) the preferential etching of a single crystal sphere to finite crystal form (FCF). Single crystal spheres have been widely used to establish etch and oxidation rates on convex surfaces in metal and metallic compound development for device structuring applications.

Spin Etch

Etching of a specimen with the solution and/or part rotating.

Sputter Etch

A term for RF or DC plasma etching.

Squirt Etch

Any solution used in the form of a liquid jet or spray. Term often applied when a polyethylene bottle know as a "squirt bottle" is used, and there are many designed jet etch systems.

Stacking Fault Etch

Specialized dislocation term used in single crystal processing. Specific preferential etches have been developed to accentuate this form of defect, which can be common to oxide and nitride thin films. The defect appears as a series of short, parallel slip lines in a translucent to transparent thin section, and are a three-dimensional defect relative to x, y, z crystallo-graphic axes. They occur due to inherent stress factors from the difference between coef-ficients of expansion of oxide/nitride thin films and the substrate materials on which they are deposited. The stacking faults can be in both the oxide/nitride or in the immediate substrate surface near the interface between the two compounds (SiCVSi interface, as an example).

Stagnant Etch

The term is applied to an etch mixture that has been allowed to stand before use. The H2SO4:H2O2 mixtures have been so used, with effective depletion of the hydrogen peroxide. CP4 also has been allowed to sit 24 h before use with the effective vaporization loss of the bromine fraction. Aqua regia (1 HC1:3 HNO3) is an example of a solution that requires aging before use, but it is not a stagnant solution.

Stain Etch

Any liquid solution or gas, such as air or oxygen, producing a coloration action on a surface with minimum etch removal. HF:HNO3 solutions, either high in HF on high in HNO3, will stain a surface rather than etch. Other solutions, such as those containing salts of copper, silver or gold, also will produce stains. Both HF and HNO3, develop red/blue/yellow color; whereas metal stains are grey to black. Staining has been used for depth profiling of diffused p-n junctions; in delineating exposed planar junctions; or to observe epitaxy layer structures in cleaved (110) cross-sections, which are stained after cleaving. Spheres have been oxidized in oxide growth rate studies relative to crystal planes, and metallographic samples are heat-tinted by oxidation in air on a hot plate.

Staining

Preciptation etching that causes contrast by distinctive staining of microconstituents; different interference colors orginate from surface layers of varying thickness. Prof of inhomogeneities.

Standard Etch

The term has been used in three ways: (1) a solution developed for a particular process becomes a Standard for that process; (2) a solution used as a reference in material or chemical analysis, and (3) a solution that has become standard for a particular use, such as CP4 as a polish etch, or Sirtl etch for defects.

Steam Etch

The use of water at its boiling point as a cleaning or etching solution. Steam cleaning under pressure for cleaning buildings, clothing, and small parts in autoclaves. In material processing the steam actively getters and uses a portion of the material surface in forming the oxide, such as a silicon wafer surface atoms being used to form silicon dioxide.

Step Etch

Any solution used to form an etched step in a material surface. The method is used in device structuring; to measure a layer thickness; to profile diffused junction depths; to trace defects in a material bulk; and may be single or multiple steps. A specimen surface is successively coasted with stripes of Apiezon-W (black wax) or photo resist coated in a similar manner, being etched to a controlled depth between each coating to form the steps.

Still Etch

A solution used without movement of either the solution or the part being etched. Some very slow polishing etches have been used in this manner.

Stir Etch

Any solution used with a rotational motion. Magnetic stirring hot plates; hand swirling;a hand of electrically operated stirring rod in solution, etc. In etching wafer surfaces for planarity, rotation speed is controlled so as to prevent flow patterns being developed.

Stop Etch

Also called: "Etch-Stop". Any etch solution that will attack one material and not another in a layer-type structure, A fairly recent term as applied to the selective etching of semi-conductor heterostructure devices, although the method has been in existence for many, many years in both the metals and semiconductor industries without having a specific name applied to the process, such as the etch removal or pattern etching of an oxide with HF that does not attack the underlying substrate. The solution may not be a complete "stop", as with an Si3N4 thin film on SiO2 etched with H3PO4, where the oxide etches at a much slower rate, effectively working as an etch-stop.

Strain Etch

Similar to Stress Etch. Terms often used in combination as stress and strain studies. The bending of a thin material, such as a semiconductor wafer, will develop dislocations due to strain. Such defects have been studied as both a positive (+) or negative (-) strain direction relative to (100), (111)A or (TTT)B faces, and <110> directions.

Stress Etch

A preferential solution used to develop stress figures in a material. Stress may be from normal wear-and-tear; induced by heat treatment; physically induced by tension, compression or torque with or without heat. The latter method used in material studies.

Strong Etch

A general term applied to the use of concentrated acids or alkalies, as against a diluted solution, or a solution using weak acids.

Structure Etch

Any solution used to develop physical structure whether it is a defect in the material, a selectively etched pit, mesa, channel or the shaping of a solid.

Subtractive Etch

Term applies to the selective etching of multiple thin film layers. The removal of one layer without affecting others.

Swab Etch

Use of cotton or plastic foam type material on a stick. Medical Q-tips are used and, in Solid State processing, the cotton has been replaced with plastic foam to prevent reaction from the glue used to attach the cotton. Used with acetone for cleaning photo resist lacquers from surfaces. In processing metallographic specimens, swab etching is a common term and method of etching surface structure. Wiping of the specimen surface with a cotton ball saturated with etchant to simultaneously remove reaction products.

Swirl Etch

Any solution used with a rotating motion.

Temperature Etch

Temperature of cleaning or etching solutions vary with solution mixture, application requirements, and may be as a solid, liquid, or gas. May also refer to the use of temperature, alone, as a (heat/thermal) etch agent, under vacuum or furnace conditions. Much WCE etching is done at room temperature, but many solutions are exothermic, thus heating the solution during the etching period. To control such reactions, water or solvent cooling coils surround a water bath holding the etch solution vessel have been designed to limit such temperature rise. And temperature can be a major control factor for particular etch mix-tures... at room temperature (RT) a 1HF:8HNO3 solution is a good polish etch... but at 8C becomes preferential... and at 50C too rapid and erratic for control.

Thermal Etch

Term has been applied as (1) the use of heat in vacuum; (2) the use of heat in furnaces with a gas atmosphere. In the latter case, also called heat treatment (metals), and annealing (Solid State), though both terms have been used in all material processing areas. Pure heat alone can develop etch figures or structures on surfaces.

Thermal Etching

Annealing of the specimen in vacuum or inert atmosphere. Used primarily in high-temperature microscopy.

Thimble Etch

Any cup shaped vessel used to hold an etch solution. Specifically referenced to using small, ceramic, high temperature metal (platinum), or graphite crucibles to contain highly reactive, hot chemicals or liquid metals, such as KOH pellets at 360C for dislocation etching of silicon wafers.

Thinning Etch

Any solution used to reduce thickness of a specimen. Widely used with reference to preparing specimens for transmission electron microscopy (TEM) studies.

Time

Preparation time, the time during which the specimen holder is rotating and pressed against the grinding/polishing disc.

Tinting

See heat tinting.

Trim Etch

Any etch used to reduce thickness, width, or length of a part, specimen, or device by small increments, only. This can include laser trimming, such as in fine-tuning paired diode devices for electrical matching parameters.

True Microstructure

Theoretically we are interested in examining a specimen surface which shows us a precise image of the microstructure we are to analyse. Ideally, we require the following: no deformation, no scratches, no pull-outs, no introduction of foreign materials, no smearing, no relief or rounded edges and no thermal damage. This nearly perfect condition, with only superficial damage remaining, is commonly called the true microstructure.

Tumble Etch

A closed-end cylinder - called a "tumbler" - has long been used to polish rock and mineral specimens, or for surface cleaning of parts. Dry abrasive, a wet slurry or acid-slurry abrasive is added to specimens, then the tumbler rotated horizontally on a set of parallel bars. Rotation can be with a hand-operated crank but today tumblers are electrically operated. For parts clean/etch cycles, time is in minutes; whereas gem stone polishing is in days. Specimens and parts can be tumble etched in a beaker with the solution being stirred and parts floating free.

Ultrasonic Etch

Any solution used with an ultrasonic generator to develop agitation during an etching or cleaning period. There are small cup to very large basin-type systems. The latter include vapor degreasing systems. The cup types are used for cleaning and etching small parts with an etch beaker seated in a water bath that transmits the vibration frequency to the solution. Most systems are fixed frequency, but variable frequency units are available. A barium titanate, Ba2Ti03, transducer is used to translate physical motion of the titanate into electrical frequency, much like piezoelectric quartz crystal radio frequency blanks.

Used Etch

Any solution applied for more than one period of time. In high volume processing where several parts are batch etched at one time, large volumes of etch solutions are used to sustain solution action without constituent depletion, and ensure good repetitive, temperature in-dependent etching without having to replenish with fresh solution after each etch period. In metal plating, the plating baths are automatically monitored, and additional solution added when plating rate reduces to a pre-set level.

Vacuum Etch

The use of pure vacuum to effect etching action by varying the vapor pressure. This method has been used to preferentially etch single crystal gases grown under cryogenic arid pressure conditions in vacuum.

Vapor Decreasing Etch

Vapor degreasing has wide use in cleaning parts with a combination of hot liquid, hot spray, and a hot vapor head in which parts are held. In the large systems, the hot liquid tank may include an ultrasonic transducer. Size ranges from a beaker on a hot plate to large tanks with an overhead crane hoist. Parts are lowered and held in the hot vapor head until they are deemed clean; they are then slowly removed and are found clean and dry. Although trichloroethylene (TCE), dichloroethylene (DCE, Perk), or trichloroethane (TCA) have been used in the past, Freon solvents are being used as replacements due to the carcinogenic nature of chlorinated solvents.

Vapor Etch

Any solution used in vapor form to effect an etching or cleaning action. HNO3, H2O, and H2O2 arc all used to oxidize a surface, then the oxide stripped with HF as one method of surface cleaning. In epitaxy system, hot HCl vapor is used to clean the quartz tube walls, the susceptor carrier and, in some cases, the material surface about to be deposited upon.

Via Hole Etch

Specialized term in semiconductor processing where a crystallographically orient hole is Selectively etched through a wafer. The side walls of the hole are then metallized through from top to bottom surface, often referred to as wrap-around plating for an electrical ground plane. See Selective Etch.

Vibration Etch

Any form of vibration used in conjunction with an etching or cleaning solution. The two most common systems are an ultrasonic transducer or a shaker table. Vibration alone is a standard assembly test vehicle, and can cause part or assembly failure. Such vibration tests include acceleration/deceleration, and g-force generators with an x, y, z spin component.

Wash Etch

Used with reference to the pouring of a solution across a surface. Not widely used for etching, as it tends to cause surface channelling. Standard water quenching of parts after etching is sometimes referred to as "Wash" clean, but is not an actual etching method.

Water Etch

Though water is considered neutral, with pH 7, the major liquid used for quenching an etch solution, and for general washing and rinsing, it can act as an acid etch on water soluble compounds. Such compounds can be polished, preferential etched, or selective etched with water only. Sodium Chloride, NaCl, is one such compound that is widely used as a (100) oriented substrate for thin film metal evaporation and epitaxy growth in morphological studies with thin films removed by the float-off technique for TEM observation. High purity water, as well as brine and atmospheric moisture, will slowly corrode many metals and alloys. The metal industry uses coupons of new materials in corrosion tests by exposure to salt atmosphere along scacoasts, and study irons and steels by dripping high purity water onto surfaces over extended periods of time. In the study of ice, it is grown as single crystals and water is used to polish or preferential etch surfaces.

Weak Etch

The use of a highly diluted etch mixture or a singular liquid; such as ammonium hydroxide, NH4OH and ammonia, NH3, which are both weak bases.

Wet Chemical Etching (WCE)

One of the three major divisions in chemical etching. It is the use of any liquid to effect cleaning or etching action and still the most widely used method of etching.

Wet Etching

Developmnet of microstructure with liquids (acids, bases, neutral solutions, mixtures of solutions).

Wipe Etching

See swabbing.

White Etch

The term has been applied to mixtures of HF:HNO3 with or without HAc/H2O. It is not recommended, as these solutions are clear and transparent, not an opaque white.

Work Damage Etch

Any polish etch used to remove residual sub-surface damage remaining after cutting and mechanical lap and polish in preparing a wafer or similar specimen. The bromine:methanol (Br2:Me0H) or BRM solutions are currently used on many metals and metallic compounds for this purpose, as they not only remove such damage, but act as slow polishing solutions.

X-Ray Etch

Though X-rays are a photographic technique used in both medicine and material studies, X-rays, as well as other particles, have been used in material surface studies. Fluorite, CaF2, will show color changes when subjected to X-rays, such that here it is referred to as a method of etching. Radiation or irradiation using ionized gases or atomic particles can produce similar effects in material, as well as cause internal, bulk damage. Again, not a true etching phenomenon, but of major importance in material processing. All space hardware is subjected to radiation evaluation as one high reliability test, and X-ray may be included.

Yellow Room Etch

Any solution used in a Yellow Room for the processing of material by photolithographic techniques. Photo resist lacquers are affected by exposure to white light, such that all processing is done under yellow light with humidity controlled at 40 % 5 RH, and temperature between 70-72 F for- optimum results. Too much humidity and photo resist will not harden properly; whereas too low a humidity, the lacquer will harden too rapidly and crack. If the temperature approaches 80F, the resist also will not cure or harden properly even under controlled oven bake out conditions.

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