Terms / Glossary
- Acceptor - An element, such as boron, indium, and gallium used to create a free hole in a semiconductor. The acceptor atoms are required to have one less valence electron than the semiconductor.
- Alignment Precision - Displacement of patterns that occurs during the photolithography process.
- Anisotropic - A process of etching that has very little or no undercutting
- Area Contamination - Any foreign particles or material that are found on the surface of a wafer. This is viewed as discolored or smudged, and it is the result of stains, fingerprints, water spots, etc.
- Azimuth, in Ellipsometry - The angle measured between the plane of incidence and the major axis of the ellipse.
- Backside - The bottom surface of a silicon wafer. (Note: This term is not preferred; instead, use ‘back surface’.)
- Base Silicon Layer - The silicon wafer that is located underneath the insulator layer, which supports the silicon film on top of the wafer.
- Bipolar - Transistors that are able to use both holes and electrons as charge carriers.
- Bonded Wafers - Two silicon wafers that have been bonded together by silicon dioxide, which acts as an insulating layer.
- Bonding Interface - The area where the bonding of two wafers occurs.
- Buried Layer - A path of low resistance for a current moving in a device. Many of these dopants are antimony and arsenic.
- Buried Oxide Layer (BOX) - The layer that insulates between the two wafers.
- Carrier - Valence holes and conduction electrons that are capable of carrying a charge through a solid surface in a silicon wafer.
- Chemical-Mechanical Polish (CMP) - A process of flattening and polishing wafers that utilizes both chemical removal and mechanical buffing. It is used during the fabrication process.
- Chuck Mark - A mark found on either surface of a wafer, caused by either a robotic end effector, a chuck, or a wand.
- Cleavage Plane - A fracture plane that is preferred.
- Crack - A mark found on a wafer that is greater than 0.25 mm in length.
- Crater - Visible under diffused illumination, a surface imperfection on a wafer that can be distinguished individually.
- Conductivity (electrical) - A measurement of how easily charge carriers can flow throughout a material.
- Conductivity Type - The type of charge carriers in a wafer, such as “N-type” and “P-type”.
- Contamination Area - An area that contains particles that can negatively affect the characteristics of a silicon wafer.
- Contamination Particulate - Particles found on the surface of a silicon wafer.
- Crystal Defect - Parts of the crystal that contain vacancies and dislocations that can have an impact on a circuit’s electrical performance.
- Crystal Indices - See Miller indices.
- Depletion Layer - A region on a wafer that contains an electrical field that sweeps out charge carriers.
- Dimple - A concave depression found on the surface of a wafer that is visible to the eye under the correct lighting conditions.
- Donor - A contaminate that has donated extra “free” electrons, thus making a wafer “N-Type”.
- Dopant - An element that contributes an electron or a hole to the conduction process, thus altering the conductivity. Dopants for silicon wafers are found in Groups III and V of the Periodic Table of the Elements.
- Doping - The process of the donation of an electron or hole to the conduction process by a dopant.
- 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 Exclusion, Nominal (EE) - The distance between the fixed quality area and the periphery of a wafer.
- Edge Profile - The edges of two bonded wafers that have been shaped either chemically or mechanically.
- Etch - A process of chemical reactions or physical removal to rid the wafer of excess materials.
- Fixed Quality Area (FQA) - The area that is most central on a wafer surface.
- Flat - A section of the perimeter of a wafer that has been removed for wafer orientation purposes.
- Flat Diameter - The measurement from the center of the flat through the center of the wafer to the opposite edge of the wafer. (Perpendicular to the flat)
- Four-Point Probe - Test equipment used to test resistivity of wafers.
- Furnace and Thermal Processes - Equipment with a temperature gauge used for processing wafers. A constant temperature is required for the process.
- Front Side - The top side of a silicon wafer. (This term is not preferred; use front surface instead.)
- Goniometer - An instrument used in measuring angles.
- Gradient, Resistivity - Not preferred; see resistivity variation.
- Groove - A scratch that was not completely polished out.
- Hand Scribe Mark - A marking that is hand scratched onto the back surface of a wafer for identification purposes.
- Haze - A mass concentration of surface imperfections, often giving a hazy appearance to the wafer.
- Hole - Similar to a positive charge, this is caused by the absence of a valence electron.
- Ingot - A cylindrical solid made of polycrystalline or single crystal silicon from which wafers are cut.
- Laser Light-Scattering Event - A signal pulse that locates surface imperfections on a wafer.
- Lay - The main direction of surface texture on a wafer.
- Light Point Defect (LPD) - Not preferred; see localized light-scatterer.
- 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 of similar sizes and characteristics placed together in a shipment.
- Majority Carrier - A carrier, either a hole or an electron that is dominant in a specific region, such as electrons in an N-Type area.
- Mechanical Test Wafer - A silicon wafer used for testing purposes.
- Microroughness - Surface roughness with spacing between the impurities with a measurement of less than 100 ?m.
- Miller Indices, of a Crystallographic Plane - A system that utilizes three numbers to identify plan orientation in a crystal.
- Minimal Conditions or Dimensions - The allowable conditions for determining whether or not a wafer is considered acceptable.
- Minority Carrier - A carrier, either a hole or an electron that is not dominant in a specific region, such as electrons in a P-Type area.
- Mound - A raised defect on the surface of a wafer measuring more than 0.25 mm.
- 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.
- Particle - A small piece of material found on a wafer that is not connected with it.
- Particle Counting - Wafers that are used to test tools for particle contamination.
- Particulate Contamination - Particles found on the surface of a wafer. They appear as bright points when a collineated light is shined on the wafer.
- 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.
- Premium Wafer - A wafer that can be used for particle counting, measuring pattern resolution in the photolithography process, and metal contamination monitoring. This wafer has very strict specifications for a specific usage, but looser specifications than the prime wafer.
- Primary Orientation Flat - The longest flat found on the wafer.
- Process Test Wafer - A wafer that can be used for processes as well as area cleanliness.
- Profilometer - A tool that is used for measuring surface topography.
- Resistivity (Electrical) - The amount of difficulty that charged carriers have in moving throughout material.
- Required - The minimum specifications needed by the customer when ordering wafers.
- Roughness - The texture found on the surface of the wafer that is spaced very closely together.
- Saw Marks - Surface irregularities
- Scan Direction - In the flatness calculation, the direction of the subsites.
- Scratch - A mark that is found on the wafer surface.
- Secondary Flat - A flat that is smaller than the primary orientation flat. The position of this flat determines what type the wafer is, and also the orientation of the wafer.
- 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 Array - a neighboring set of sites
- Slip - A defect pattern of small ridges found on the surface of the wafer.
- Smudge - A defect or contamination found on the wafer caused by fingerprints.
- Striation - Defects or contaminations found in the shape of a helix.
- Subsite, of a Site - An area found within the site, also rectangular. The center of the subsite must be located within the original site.
- Surface Texture - Variations found on the real surface of the wafer that deviate from the reference surface.
- Test Wafer - A silicon wafer that is used in manufacturing for monitoring and testing purposes.
- Thickness of Top Silicon Film - The distance found between the face of the top silicon film and the surface of the oxide layer.
- Top Silicon Film - The layer of silicon on which semiconductor devices are placed. This is located on top of the insulating layer.
- Total Indicator Reading (TIR) - The smallest distance between planes on the surface of the wafer.
- Virgin Test Wafer - A wafer that has not been used in manufacturing or other processes.
- Void - The lack of any sort of bond (particularly a chemical bond) at the site of bonding.
- Waves - Curves and contours found on the surface of the wafer that can be seen by the naked eye.
- Waviness - Widely spaced imperfections on the surface of a wafer.