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Terms used in the surface finishing industry

Glossary of industry terminology

This glossary is a collection of terminology commonly used in our industry. Do you have questions concerning a specific term, or would you like to contribute? Get in touch with us. We look forward to your feedback.

Aspheric lens or asphere A lens whose surface profiles are not portions of a sphere or cylinder.
Average roughness (Ra) Ra is calculated by an algorithm that measures the average length between the peaks and valleys and the deviation from the mean line on the entire surface within the sampling length. Ra averages all peaks and valleys of the roughness profile and then neutralizes the few outlying points so that the extreme points have no significant impact on the final results. It's a simple and effective method for monitoring surface texture and ensuring consistency in measurement of multiple surfaces.
Barrier layer A film layer that creates a blockade.
Bonded wafers Two silicon wafers that have been bonded together by silicon dioxide, which acts as an insulating layer.
Bow The deviation of the center point of the median surface of a free, un-clamped wafer from the median surface reference plane established by three points equally spaced on a circle with a diameter a specified amount less than the nominal diameter of the wafer.
Chemical-mechanical planarization/polish (CMP) A process of flattening and polishing wafers that utilizes both chemical removal and mechanical buffing. It is used during the fabrication process.
Conditioning A process that help to restore the original properties of a pad.
Contamination Other residual non-uniform surface abnormalities.
Contamination area An area that contains particles that can negatively affect the characteristics of a silicon wafer.
Critical dimension Typically, the minimum size line width on a circuit, pattern.
Defectivity Any surface imperfection, scratch, dig, or haze.
Dig A defect on a polished optical surface that is nearly equal in terms of its length and width.
Dimple A concave depression found on the surface of a wafer that is visible to the eye under the correct lighting conditions.
Down force The amount of pressure applied to the wafer per unit area on the substrate.
Edge chip and indent An edge imperfection that is greater than 0.25 mm.
Edge exclusion area The area located between the fixed quality area and the periphery of a wafer. (This varies according to the dimensions of the wafer.)
Edge profile The edges of a wafer that have been shaped either chemically or mechanically.
Etch A process of chemical reactions or physical removal to rid the wafer of excess materials.
Erosion A selectivity problem where one material is removed at a faster rate than another on a device.
Fringe One of the light or dark bands produced by interference or diffraction of light.
Focal plane deviation (FPD) The largest of the absolute values of the deviations from a reference plane.
Global flatness The total indicator reading (TIR) or the maximum focal plane deviation (FPD) relative to a specified reference plane within the fixed quality area.
Haze A mass concentration of surface imperfections micro-roughness, often giving a hazy appearance to the wafer.
Ingot A cylindrical solid made of polycrystalline or single crystal silicon from which wafers are cut.
Kerf Loss that is associated with any type of cutting and sectioning of materials. It is the amount of material lost in manufacturing process.
Laser light-scattering event A signal pulse that locates surface imperfections on a wafer.
Lithography The process used to transfer patterns onto wafers.
Localized light-scatterer One feature on the surface of a wafer, such as a pit or a scratch that scatters light. It is also called a light point defect.
Lot Wafers manufactured in the same batch and placed together in a shipment.
Mask Used for patterning Wafers.
Microroughness Surface roughness with spacing between the impurities with a measurement of less than 100 µm.
Notch An indent on the edge of a wafer used for orientation purposes.
Orange peel A roughened surface that is visible to the unaided eye.
Oxidation Growth of Oxide, formed during diffusion in a furnace at > 800° C.
Particle A small piece of material found on a wafer that is not connected with it.
Platen The rotating base on which the polishing pad is mounted also known as a table.
Pit A non-removable imperfection found on the surface of a wafer.
Point defect A crystal defect that is an impurity, such as a lattice vacancy or an interstitial atom.
Removal rate The amount of material removed in polishing or CMP process during a given amount of time.
Roughness The texture found on the surface of the wafer that is spaced very closely together.
Scratch A defect on a polished optical surface whose length is many times its width.
Surface flatness The surface flatness of the optical flat, given in terms of waves. (wave length =633nm or 25 millionth of an inch)
Site An area on the front surface of the wafer that has sides parallel and perpendicular to the primary orientation flat. (This area is rectangular in shape.)
Site flatness STIR The total indicator reading (TIR) or the maximum focal plane deviation (FPD) of the portion of the site that falls within the fixed quality area.
Selectivity The ratio of the relative removal rates on two or more materials.
Specific gravity The ratio of the density of a material to the density of water.
Sputtering A method of depositing a metal film.
Striation Defects or contamination found in the shape of a helix.
Swarf Material or debris generated during the polishing process that is a combination of the removed material, pad and slurry.
Surface roughness The arithmetic average of the absolute values or the average length between the peaks and valleys.
TTV (total thickness variation) The difference between the maximum and minimum values of thickness encountered during a scan pattern or series of point measurements.