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Term (Index) Definition
mask  device used to shape desired geometries on the surface of the wafer; Examples: (i)photomask; allows selective irradiation of resist on the wafer surface by blocking irradiation in selected areas; consist of opaque (non-transparent to given wavelengths) and blank (transparent) parts; in photolithography chrome, and quartz respectively; (ii)mechanical (shadow) mask; a thin sheet of metal with properly shaped holes; sometimes used to define crude geometries on the surface of the wafer during physical vapor depositions.
photomask  mask used in photolithography to block resist exposure to UV radiation in selected areas; consists of chrome opaque areas supported by high quality quartz plate transparent to UV radiation.
X-ray mask  mask used in X-ray lithography; uses gold as an opaque material; gold pattern (defined using e-beam lithography) is supported by a thin membrane made out of material transparent to X-rays of given wavelength, e.g. Si3N4, SiC and others.
Term (Index) Definition
chrome mask  mask used in photolithography which uses thin film of chrome as an opaque material; due to sharper edges, mechanical durability, and optical density of Cr superior to emulsion based photomask.
photomask  mask used in photolithography to block resist exposure to UV radiation in selected areas; consists of chrome opaque areas supported by high quality quartz plate transparent to UV radiation.
photoemulsion  material acting as an opaque (nontransparent to UV radiation) part of the masks used in photolithography; inferior to chrome, used for the same purpose, due to lower optical density (thicker film needed to block off UV radiation) grainy structure (not as sharp edges as in the case of chrome) and softness making it vulnerable to mechanical damage.
opaque material  part of the mask which is not transparent to radiation used for resist exposure; different opaque materials are used in photolithography and X-ray lithography.
Term (Index) Definition
etch mask  material blocking etching in selected areas of the wafer surface; typically photoresist is acting as an etch mask.
photoresist  photo-sensitive material used in photolithography to transfer pattern from the mask onto the wafer; a liquid deposited on the surface of the wafer as a thin film then solidified by low temperature anneal; in the areas in which photoresist can be reached by UV radiation photochemical reactions change its properties, specifically, solubility in the developer; two types of photoresist: positive and negative.
Term (Index) Definition
mask, photolithography  see photomask
photomask  mask used in photolithography to block resist exposure to UV radiation in selected areas; consists of chrome opaque areas supported by high quality quartz plate transparent to UV radiation.
X-ray mask  mask used in X-ray lithography; uses gold as an opaque material; gold pattern (defined using e-beam lithography) is supported by a thin membrane made out of material transparent to X-rays of given wavelength, e.g. Si3N4, SiC and others.
Term (Index) Definition
mask, X-ray lithography  see X-ray mask.
X-ray mask  mask used in X-ray lithography; uses gold as an opaque material; gold pattern (defined using e-beam lithography) is supported by a thin membrane made out of material transparent to X-rays of given wavelength, e.g. Si3N4, SiC and others.
Term (Index) Definition
mechanical mask  thin, yet rigid, sheet of metal with adequately shaped holes through which material can be deposited directly on the wafer surface; deposited geometries reflect shape of the openings in the sheet metal, but resolution of the process is very low.
evaporation  common technique used to deposit thin film materials; material to be deposited is heated in vacuum, 10-6 Torr - 10-7 Torr range, until it melts and starts evaporating; vapor of material is condensing on the cooler substrate exposed to the vapor; common technique in thin film metal deposition; not suitable for high melting point materials; one of the PVD (Physical Vapor Deposition) methods of thin film formation.
mask  device used to shape desired geometries on the surface of the wafer; Examples: (i)photomask; allows selective irradiation of resist on the wafer surface by blocking irradiation in selected areas; consist of opaque (non-transparent to given wavelengths) and blank (transparent) parts; in photolithography chrome, and quartz respectively; (ii)mechanical (shadow) mask; a thin sheet of metal with properly shaped holes; sometimes used to define crude geometries on the surface of the wafer during physical vapor depositions.
sputtering, sputter deposition  bombardment of solid (target) by high energy chemically inert ions (e.g. Ar+)extracted from plasma; causes ejection of atoms from the target which are then re-deposited on the surface of the substrate purposely located in the vicinity of the target; common method of Physical Vapor Deposition (PVD) of metals and oxides.
Term (Index) Definition
oxidation mask  thin layer of material capable of preventing oxidation of material underneath it; in silicon processing a silicon nitride, Si3N4, is acting as a very effective oxidation mask (see LOCOS)
LOCOS  Local Oxidation of Silicon; isolation scheme commonly used in MOS/CMOS silicon technology; thick (in the range of 500 nm) pad of thermally grown SiO2 separates adjacent devices (e.g. PMOS and NMOS transistor in CMOS structure); local oxidation is accomplished by using silicon nitride, Si3N4, to prevent oxidation of Si in selected areas, hence, "local" oxidation; prior to SiO2 pad formation silicon in between Si3N4 covered regions is implanted to form "channel stop"; Si3N4 mask is etched off following thermal oxidation and MOSFETs are ten formed in the open spaces.
silicon nitride, Si3N4  dielectric material with energy gap = 5 eV and density ~3.0 g/cm3; excellent mask (barrier) against oxidation of Si; commonlly used in silicon integrated circuit manufacturing primarily in LOCOS process; not used as a gate dielectric due to inferior interface with silicon and bulk defects; properties depend on deposition method: dielectric strength ~107 V/cm, dielectric constant k ~6-7, bulk resistivity 1015-1017 ohm-cm; deposited by CDV.
Term (Index) Definition
phase shift mask, PSM  a conventional mask to which layer of material featuring desired refractive index and thickness is locally added in order to shift phase of light passing through transparent portion of the mask; phase shifting increases resolution of pattern transfer by destructive interference preventing resist exposure in the regions in which it should not be exposed.
mask  device used to shape desired geometries on the surface of the wafer; Examples: (i)photomask; allows selective irradiation of resist on the wafer surface by blocking irradiation in selected areas; consist of opaque (non-transparent to given wavelengths) and blank (transparent) parts; in photolithography chrome, and quartz respectively; (ii)mechanical (shadow) mask; a thin sheet of metal with properly shaped holes; sometimes used to define crude geometries on the surface of the wafer during physical vapor depositions.
mask, photolithography  see photomask
enhancement techniques  term typically refers to techniques employed to extend use of photolithography into sub-100 nm regime; e.g., phase-shift masks, immersion photolithography, new photoresist formulations, etc.
Term (Index) Definition
photoemulsion mask  mask used in photolithography which uses thin fim of photoemulsion as an opaque material.
photolithography, optical lithography  pattern definition method which uses UV radiation to expose the resist; the most common lithography technique in semiconductor manufacturing; using extremely short wavelength UV (extreme UV; wavelenghts below 200 nm), projection printing (steppers), phase shift masks, and adequate resist technology photolithography is capable of resolution below 100 nm.
photoemulsion  material acting as an opaque (nontransparent to UV radiation) part of the masks used in photolithography; inferior to chrome, used for the same purpose, due to lower optical density (thicker film needed to block off UV radiation) grainy structure (not as sharp edges as in the case of chrome) and softness making it vulnerable to mechanical damage.
Term (Index) Definition
shadow mask  same as mechanical mask.
mechanical mask  thin, yet rigid, sheet of metal with adequately shaped holes through which material can be deposited directly on the wafer surface; deposited geometries reflect shape of the openings in the sheet metal, but resolution of the process is very low.
Term (Index) Definition
X-ray mask  mask used in X-ray lithography; uses gold as an opaque material; gold pattern (defined using e-beam lithography) is supported by a thin membrane made out of material transparent to X-rays of given wavelength, e.g. Si3N4, SiC and others.
photomask  mask used in photolithography to block resist exposure to UV radiation in selected areas; consists of chrome opaque areas supported by high quality quartz plate transparent to UV radiation.
X-ray lithography  lithography method using X-ray to expose the resist; due to shorter wavelength of X-ray radiation (0.4 - 4 nm)XRL allows higher resolution than photolithography which uses longer wavelength UV irradiation; XRL requires special mask and resists sensitive to X-rays.
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Jerzy Ruzyllo is a Distinguished Professor Emeritus in the Department of Electrical Engineering at Penn State University.



This book gives a complete account of semiconductor engineering covering semiconductor properties, semiconductor materials, semiconductor devices and their uses, process technology, fabrication processes, and semiconductor materials and process characterization.


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Created and operated by J. Ruzyllo. Copyright © J. Ruzyllo 2001-2016. All rights reserved.

Information in this glossary is provided at the author's discretion. Any liability based on, or related to the contents of this glossary is disclaimed.