ASTM F1241-95(2000)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 1241 – 95 (Reapproved 2000)
Standard Terminology of
Silicon Technology
This standard is issued under the fixed designation F 1241; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope p–type material, or toward a more positive voltage for
n–type material, results in less than a 1 % change in the
1.1 This terminology covers terms and definition used in
maximum capacitance, C . F 1153
max
relation to semiconductor grade silicon crystal and wafers.
anisotropic, adj.— exhibiting different physical properties in
1.2 This terminology covers terms describing attributes of
different directions.
silicon wafers as specified in SEMI Specifications M1 and
SEMI Format M18. These attributes include electrical, struc-
DISCUSSION—In semiconductor technology, the different directions
tural, chemical, and mechanical characteristics of polished and are defined by the crystallographic planes.
epitaxial wafers as well as surface defects and contamination.
anisotropic etch—a selective etch that exhibits an accelerated
1.3 This terminology is applicable for use in connection
etch rate along specific crystallographic planes.
with research, developement, process control, procurement,
DISCUSSION—Anisotropic etches are used to determine crystal orien-
and inspection of silicon material.
tation, to facilitate dielectric component isolation, and to fabricate
1.4 Originally the terms and definitions included in this
micromechanical structures.
standard were extracted from other ASTM Standards relating
to silicon technology. The original source standards for such
area contamination—on a semiconductor wafer, matter, un-
terms are identified by their designations immediately follow-
intentionally added to the surface of the wafer, of extent
ing the definition. All such standards are found in this volume
greater than a single localized light scatterer.
of the Annual Book of ASTM Standards. More recently, new or
DISCUSSION—Area contamination may be foreign matter on the wafer
revised terms and definitions have been balloted directly for
surface resulting from chuck marks, finger or glove prints, stains, wax
inclusion in this standard; these terms have no designation
or solvent residues, etc.
following the definition.
area defect—not preferred, see extended light scatterer.
1.5 Almost all of the terms listed are nouns; in other cases,
azimuth—in ellipsometry, the angle between the major axis of
the part of speech is given explicitly immediately following the
the ellipse and the plane of incidence.
term.
autodoping—of an epitaxial layer, incorporation of dopant
2. Referenced Documents
originating from the substrate into epitaxial layer. Also
called self-doping.
2.1 SEMI Standards:
backside—Not preferred, use back surface.
M1 Specifications for Polished Monocrystalline Silicon Wa-
back surface—of a semiconductor wafer, the exposed surface
fers
opposite to that upon which active semiconductor devices
M18 Format for Silicon Wafer Specification Form for Order
have been or will be fabricated. F 523, F 533, F 534
Entry
bevel angle, a— the smaller of the angles between the wafer
3. Terminology
surface and the section plane. F 950
bipolar—semiconductor device fabrication technology that
3.1 Terms and Their Definitions:
produces transistors that use both holes and electrons as
acceptor—an impurity in a semiconductor that accepts elec-
charge carriers.
trons excited from the valence band, leading to hole conduc-
birefringence—a double-refraction phenomenon in which an
tion.
unpolarized beam of light is divided into two beams with
accumulation condition—the region of the C–V curve for
different directions and relative velocities.
which a 5-V increment toward a more negative voltage for
block structure—See cell structure. F 154
bow—of a semiconductor wafer, the deviation of the center
This terminology is under the jurisdiction of ASTM Committee F-1 on
point of the median surface of a free, unclamped wafer from
Electronics and is the direct responsibility of Subcommittee F01.06 on Silicon
a median-surface reference plane established by three points
Materials and Process Control.
equally spaced on a circle with diameter a specified amount
Current edition approved Sept. 15, 1995. Published November 1995. Originally
published as F 1241 – 89. Last previous edition F 1241 – 94b. less than the nominal diameter of the wafer. F 534
Available from Semiconductor Equipment and Materials International, 805 E.
buried layer—a diffused region in a substrate that is, or is
Middlefield Rd., Mountain View, CA 94043.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1241
intended to be, covered with an epitaxial layer. substrate defects either above or below the surface plane of
carrier—in semiconductor materials, an entity capable of silicon substrates after epitaxial deposition (see also fish-
carrying electric charge through a solid, for example, va- tails). F 154
lence holes and conduction electrons in semiconductors. crow’s-foot—on semiconductor wafers, intersecting cracks in
Also called charge carrier. a pattern resembling a “crow’s foot” Y on {111} surfaces and
carrier density, n (electrons); p (holes)—the number of a cross 88+” on {100} surfaces. F 154, F 523
majority carriers per unit volume in an extrinsic semicon- crystal—a solid composed of atoms, ions or molecules ar-
ductor, usually given in number/cm although the SI unit is ranged in a pattern that is periodic in three dimensions.
number/m . F 723 F47
cell structure—malformations attributable to crystal inhomo- crystal defect—departure from the regular arrangement of
geneities and that have their origins in the crystal growth atoms in the ideal crystal lattice.
process. Also known as block structure. F 154 crystal indices—See Miller indices.
chemical vapor deposition— in semiconductor technology,a crystal originated particle (COP)—a surface depression that
process in which a controlled chemical reaction produces a is formed during soft alkaline chemical treatment of silicon
thin surface film. wafer surfaces that contain crystal defects at or close to the
wafer surface and that scatters light similarly to a very small
DISCUSSION—Epitaxial growth is an example of a special case of
particle, also called surface micro defect (SMD).
chemical vapor deposition (CVD).
DISCUSSION—Soft alkaline chemical treatment may consist of clean-
chem-mechanical polish— in semiconductor technology,a
ing with a 5:1:1 H O-NH OH-H O (SC-1) solution, chem-mechanical
2 4 2 2
process for the removal of surface material from the wafer
polishing, etc.
that utilizes chemical and mechanical actions to achieve a
crystallographic notation—a symbolism based on Miller
mirror-like surface for subsequent processing.
indices used to label planes and directions in a crystal as
chip—in semiconductor wafers, region where material has
follows:
been unintentionally removed from the surface or edge of the
wafer. plane (111) direction [111]
family of planes {111} family of directions ^111&
chuck mark—any physical mark on either surface of a wafer
caused by robotic end effector, a chuck, or wand.
damage—a defect of the crystal lattice of a single crystal
cleavage plane—a crystallographically preferred fracture
silicon specimen in the form of irreversible deformation that
plane.
results from mechanical surface treatments such as sawing,
coherence—a measure of the ability a source of electromag- lapping, grinding, sandblasting, and shot peening at room
netic radiation has to interfere.
temperature without subsequent heat treatments. F 950
compensation—reduction in number of free carriers resulting damage depth, T —the maximum thickness of the damage
z
from the presence of impurities other than the majority
region as revealed by preferential etch that removes silicon
dopant density impurity. F 723 in the region of the deformation. F 950
concentration—relative amount of a minority constituent of a
deep level impurity—a chemical element that when intro-
mixture to the majority constituent (for example parts per duced into a semiconductor has an energy level (or levels)
million, parts per billion, or percent) by either volume or
that lies in the mid-range of the forbidden energy gap,
weight. F 723 between those of the dopant impurity species. F 723
conductivity (electrical)—a measure of the ease with which
depletion layer—a region in which the mobile carrier charge
charge carriers flow in a material; the reciprocal of resistiv-
density is not sufficient to neutralize the net fixed charge
ity.
density of donors and acceptors. Also known as barrier
layer, blocking layer, or space-charge layer.
DISCUSSION—In a semiconductor, the conductivity is proportional to
depletion width—the width of the region in a semiconductor
the product of free carrier density, electron charge, and carrier mobility.
near a metal-semiconductor contact in which the charge-
Most variant of all crystal properties, conductivity can range over 13
orders of magnitude. Conductivity can be locally modified by tempera-
carrier density is insufficient to neutralize the fixed-charge
ture, carrier injection, irradiation, or magnetic field. Symbol is s and
density of donors and acceptors. F 108
−1
units are (V·cm) .
diameter—of a semiconductor wafer, the linear dimension
across the surface of a circular wafer that contains the wafer
conductivity type—of a semiconductor crystal or wafer,a
center and excludes flats or other peripheral fiduciary geom-
property that identifies the majority charge carrier in the
etries. F 613
semiconductor. See also n-type, p-type.
diffused layer—a region of opposite conductivity type formed
contamination—on a semiconductor wafer, see area con-
near the surface of a semiconductor crystal as a result of the
tamination or particulate contamination.
introduction of impurities into the silicon crystal by means of
crack—on semiconductor wafers, cleavage or fracture that
solid state diffusion. F110
extends to the surface of a wafer and which may or may not
dimple—a shallow depression in a wafer surface, with a
pass through the entire thickness of the wafer. F 154
concave, spheroidal shape and gently sloping sides.
cratering—a surface texture of irregular closed ridges with
smooth central regions. F 523
crescents—structures with parallel major axes, attributed to These citations indicate definitions that have been edited or otherwise differ
from the definition in the source document.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1241
DISCUSSION—Dimples are macroscopic features that are visible to the
When observed by the unaided eye, an XLS can usually be seen under
unaided eye under proper lighting conditions. high intensity illumination. Some automated inspection instruments
have sensors for reporting XLSs. XLSs can be observed as increased
dirt—on semiconductor wafers, surface contaminant that can-
haze under dark field conditions. Under bright field conditions, an XLS
not be removed by pre-inspection solvent cleaning. F 154 can be observed as a decrease in the intensity of the specularly reflected
beam, sometimes called a light channel defect.
dislocation—a line imperfection in a crystal that either forms
the boundary between slipped and nonslipped areas of a
fast axis—in optics, of a doubly refracting crystal, that
crystals or that is characterized by a closure failure of
direction in which the velocity of light is a maximum.
Burger’s circuit. F47
F 576
donor—an impurity or imperfection in a semiconductor that
fishtails—structures, attributed to substrate defects, either
donates electrons to the conduction band, leading to electron
above or below the surface plane after epitaxial deposition,
conduction.
which have their 88tails” aligned in a particular crystallo-
dopant density—in an uncompensated extrinsic semiconduc-
graphic direction (see also crescents). F 154
tor, the number of dopant impurity atoms per unit volume,
fixed quality area (FQA)—central area of a wafer surface,
3 3
usually given in atoms/cm although the SI unit is atoms/m .
defined by a nominal edge exclusion, X, over which the
Symbols: N for donor impurities and N for acceptor
specified values of a perimeter apply.
D A
impurities. F 723
DISCUSSION—The boundary of the FQA is at all points the distance X
doping—addition of impurities to a semiconductor to control
away from the periphery of a wafer of nominal dimensions.
the electrical resistivity.
flake chip—See peripheral chip. F 154
edge effect—localized structure about the edge of a specimen.
flat—on a semiconductor wafer, a portion of the periphery of
F 154
a circular wafer that has been removed to a chord. See also
edge profile—on edge contoured wafers (whose edges have
primary orientation flat, secondary flat.
been shaped chemically or mechanically), a description of
flatband condition—in microelectronics, the point at which an
the contour of the boundary of the wafer that joins the front
external applied voltage causes there to be no internal
and back surfaces.
potential difference across an MOS structure. F 1153
effective electrical contact radius, (cm)—of a spreading
flatband voltage,V —the applied voltage necessary to pro-
resistance probe assembly, an empirical quantity defined by fb
duce the flatband condition. F 1153
a 5 nr/4R
s
flatband capacitance, C —the capacitance of an MOS struc-
fb
ture at the flatband voltage. F 1153
where:
flatness—for wafer surfaces, the deviation of the front surface,
n 5 number of current-carrying probes across which the
expressed in TIR or maximum FPD, relative to a specified
potential drop is determined,
p 5 resistivity of a homogeneous semiconductor speci- reference plane when the back surface of the wafer is ideally
men, V · cm, and flat, as when pulled down by a vacuum onto an ideally clean
R 5 measured spreading resistance, V.
flat chuck.
s
F 525, F 672
focal plane deviation (FPD)— on a wafer surface, the
ellipticity—in optics, of elliptically polarized light, the angle x distance parallel to the optical axis from a point on the wafer
given by the inverse tangent of the ratio of the minor to the
surface to the focal plane of the optical system.
major axis of the e
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