semi合集-English.pdf - 第5429页
SEMI M59-0305 © SEMI 2005 10 5.87.4 R qA can also be estimated by integrating the two-di mensional power spec tral density (PSD) fu nction, PSD ( f x , f y ), over the spatial frequency rang e between spatial freque ncie…
SEMI M59-0305 © SEMI 2005 9
5.80 point defect — a localized crystal defect such as a lattice vacancy, interstitial atom, or substitutional impurity.
Contrast with light point defect.
5.81 preferential etch — a selective etch that etches regions of different crystal strain or conductivity at different
rates, used to delineate crystal defects or regions of differing conductivity on wafer surfaces.
5.82 primary flat — the flat of longest length on the wafer, oriented such that the chord is parallel with a specified
low index crystal plane; sometimes called major flat.
5.83 radial gradient — not preferred; use resistivity variation.
5.84 reference plane — a plane defined by one of the following:
three points at specified locations on the front or back surface of the wafer,
the least squares fit to the front or median surface of the wafer using all points within the FQA,
the least squares fit to the front surface of the wafer using all points within a site, or
an ideal back surface (equivalent to the ideally flat chuck surface that contacts the wafer).
5.84.1 Discussion — For flatness measurement, the specified reference plane is chosen with due regard for the
capabilities of the imaging system. Front surface or back surface reference planes should be selected depending on
the wafer mounting system. If the wafer cannot be gimbaled in the imaging system, a back surface reference plane
should be specified. For shape measurement, the reference plane to be used is spelled out in the applicable test
method.
5.85 reference plane deviation, RPD — the distance perpendicular to the reference plane between the reference
plane and the wafer surface being measured.
5.86 resistivity, (electrical),
, [·cm] — the measure of difficulty with which charged carriers flow through a
material; the reciprocal of conductivity.
5.86.1 Discussion — the resistivity of a semiconductor or other material is the ratio of the potential gradient (electric
field) parallel with the current to the current density.
5.87 rms area microroughness, R
qA
— the root mean square of the topographic deviations of a surface Z(x,y) from
the mean surface taken within the (rectangular) evaluation area A
e
= L
x
L
y
.
5.87.1 Discussion — The rms area microroughness is one of several statistical metrics that can be used to describe
surface topography; definitions for other metrics and for such concepts as mean surface and evaluation area may be
found in ANSI/ASME B46.1 and ISO 4287/1.
5.87.2 The function R
qA
is related to a two-dimensional measurement of the surface profile as follows:
2/1
00
2
dd),(
1
x
y
L
L
e
qA
yxyxZ
A
R (1)
The digital approximation of R
qA
for a surface profile consisting of N by M data points equally spaced along the x
and y directions, respectively, is:
2/1
11
2
1
M
i
N
j
ijqA
Z
NM
R (2)
5.87.3 Experimentally, the profile is always limited by the spatial bandwidth of the measurement. In the x direction,
the profile length is L
x
divided into N equally spaced points; the lower spatial frequency limit for f
x
can never be less
than 1/L
x
and the upper spatial frequency limit can never be greater than the Nyquist limit, N/2L
x
. Similarly, in the y
direction, the profile length is L
y
divided into M equally spaced points; the lower frequency limit for f
y
can never be
less than 1/L
y
and the upper spatial frequency limit can never be greater than the Nyquist limit, M/2L
y
. Practical
limits to the spatial bandwidth are governed by considerations similar to those for the one-dimensional case (see
¶5.88.4).
SEMI M59-0305 © SEMI 2005 10
5.87.4 R
qA
can also be estimated by integrating the two-dimensional power spectral density (PSD) function, PSD(f
x
,
f
y
), over the spatial frequency range between spatial frequencies that lie within the bandwidth of the measurement:
2/1
2
1
2
1
dd),(
x
x
y
y
f
f
f
f
yxyxAqA
ffffPSDR (3)
5.87.5 If the surface is assumed to be isotropic and the instrument response function is neglected, the rms
microroughness over the spatial frequency range between f
1
and f
2
can also be obtained by integrating the isotropic
PSD function:
2/1
2
1
d)(
f
f
isoqA
ffPSDR (4)
where:
2/122
2
0
)(
and),,(2
d),()(
yx
yxA
yxAiso
fff
ffPSDf
fffPSDfPSD
5.88 rms microroughness, R
q
— the root mean square of the surface profile height deviations Z(x) from the mean
line taken within the evaluation length L.
5.88.1 Discussion — R
q
is one of several statistical metrics that can be used to describe a surface profile; definitions
for other metrics and for such concepts as mean line, evaluation length, and power spectral density function, may be
found in ANSI/ASME B46.1 and ISO 4287/1.
5.88.2 The function R
q
is related to a one-dimensional measurement of the surface profile as follows:
2/1
0
2
d)(
1
L
q
xxZ
L
R (5)
5.88.3 The digital approximation of R
q
for a profile consisting of N equally spaced points is:
2/1
1
2
1
N
i
iq
Z
N
R (6)
5.88.4 Experimentally, the profile is always limited by the spatial bandwidth of the measurement. For a profile of
length L, consisting of N equally spaced points, the lower spatial frequency limit f
1
can never be less than 1/L and
the upper spatial frequency limit f
2
can never be greater than the Nyquist limit, N/2L. In practical cases, f
1
2/L; the
achievable value of f
2
depends on instrumental parameters.
5.88.5 R
q
can also be estimated by integrating the one-dimensional power spectral density (PSD) function, PSD(f),
over the spatial frequency range between two spatial frequencies, f
1
and f
2
, that lie within the bandwidth of the
measurement:
2/1
2
1
d)(
f
f
q
ffPSDR (7)
5.88.6 In all cases, R
q
must be reported together with the lower and upper limits, f
1
and f
2
, respectively, of the spatial
frequency bandwidth over which it has been determined. Alternatively, the spatial bandwidth may be expressed in
terms of the upper and lower spatial wavelengths,
f
2
) and
f
1
), respectively.
5.89 roughness — the more narrowly spaced components of surface texture.
SEMI M59-0305 © SEMI 2005 11
5.89.1 Discussion —These components are considered within defined limits of spatial wavelength (or frequency).
5.90 scan direction — the direction of successive subsites in a scanner site flatness calculation.
5.90.1 Discussion — The scanner site flatness value obtained for a site may depend on scan direction.
5.91 scanner site flatness — the maximum subsite TIR or the maximum subsite FPD, of a site.
5.91.1 Discussion — The subsite TIR is the TIR of the portion of the subsite that falls within the FQA and within
the site; the subsite FPD is the maximum FPD of the portion of the subsite that falls within the FQA and within the
site. The reference plane is calculated using all points within the subsite that fall within the FQA.
5.91.2 Precise scanner site flatness measurement requires measurement points located closely enough to reveal the
surface topography in detail. It is recommended that the scanner site flatness be measured using a data point array
with adjacent points separated by 1 mm or less.
5.92 scratch — a shallow groove or cut below the established plane of the surface of a semiconductor wafer, with a
length to width ratio greater than 5:1.
5.93 secondary flat — a flat of length shorter than the primary orientation flat, whose position with respect to the
primary orientation flat identifies the type and orientation of the wafer.
5.94 shallow etch pits — etch pits that are small and shallow in depth under high magnification, > 200. Also
known as saucer pits (see also haze).
5.95 shape — for wafer surfaces, the deviation of a specified wafer surface relative to a specified reference plane
when the wafer is in an unclamped condition, expressed as the range or total indicator reading (TIR) or as the
maximum reference plane deviation (maximum RPD) within the specified fixed quality area.
5.95.1 Discussion — This definition is analogous to the definition of flatness, which applies to the front surface
geometry when the wafer is in the clamped condition.
5.96 site — a rectangular area, on the front surface of a wafer, whose sides are parallel and perpendicular to the
primary orientation flat or to the notch bisector, and whose center falls within the FQA.
5.97 site array — a set of contiguous sites.
5.98 site flatness — the TIR or the maximum FPD of the portion of a site that falls within the FQA.
5.98.1 Discussion — Precise site flatness measurement requires measurement points located closely enough to
reveal the surface topology in detail. It is recommended that site flatness be measured using a data point array with
adjacent points separated by 2 mm or less. It is also recommended that the data set used to calculate site flatness
have data at each site corner and along each site boundary. This makes the effective site measurement area equal to
the site size.
5.99 slip — a process of plastic deformation in which one part of a crystal undergoes a shear displacement relative
to another in a fashion that preserves the crystallinity of the material.
5.99.1 Discussion — After preferential etching, slip lines are evidenced by a pattern of one or more parallel straight
lines of dislocation etch pits that do not necessarily touch each other. On {111} surfaces, groups of lines are
inclined at 60° to each other; on {100} surfaces, they are inclined at 90° to each other.
5.100 sori — the difference between the maximum positive and maximum negative deviations of the front surface
of a wafer that is not chucked from a reference plane that is a least-squares fit to the front surface.
5.101 stain — area contamination that is chemical in nature and cannot be removed except through further lapping
or polishing.
5.101.1 Discussion — Included in this category are “white” stains that are seen after chemical etching as white or
brown streaks. Not included in this category are non-removable artifacts not caused by contaminants; such artifacts
are frequently localized differences in surface texture.
5.102 subsite, of a site — a rectangular area, L
ss
× W
ss
, on the front surface of a wafer, associated with a particular
site. The center of the subsite must be within the site. Some part of the subsite must be within or on the FQA
boundary. A subsite corresponds to the instantaneous area exposed by a scanning stepper.