semi合集-English.pdf - 第7318页

SEMI MF1188 © SEMI 2003, 2005 12 A1-4.1.3 Identification of test and reference specim ens, A1-4.1.4 Temperature of the spectrophotometer chamb er, A1-4.1.5 Thickness of test and refere nce specimens, A1-4.1.6 Location an…

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SEMI MF1188-0305 © SEMI 2003, 2005 11
double beam dispersive instruments, obtain the transmittance spectrum with the oxygen-free reference specimen in
the reference beam, and the test specimen in the sample beam. On single beam instruments, compute the
transmittance spectrum as the ratio of the emission spectrum of the test specimen to the emission spectrum of the
reference specimen.
A1-2.6 Plot the transmittance spectrum over the range from 900 cm
1
to 1300 cm
1
.
A1-2.7 Define the baseline by drawing a straight line from 900 cm
1
to 1300 cm
1
. Use the average transmittance
in the gions from 900 cm
1
to 1000 cm
1
, and 1200 cm
1
to 1300 cm
1
, to define the endpoints of the straight line.
A1-2.8 Locate the wavenumber corresponding to the minimum transmittance in the region from 1102 cm
1
to 1112
cm
1
. Record the value of that wavenumber, to five significant figures, as W
p
. Record the minimum transmittance
as T
p
, the transmittance at the absorption peak. Record the baseline transmittance, T
b
, as the value of the baseline
defined in ¶A1-2.7 at W
p
. Record both T
p
and T
b
to three significant figures.
A1-2.9 Determine and record the full width at half maximum (FWHM) of the peak.
A1-3 Calculations
A1-3.1 Calculate the peak and baseline absorption coefficients using the following equations:
p
x
p
xx
p
T
eTee
x 18.0
36.0)09.0()09.0(
ln
1
70.12270.170.1
(A1-1)
b
x
b
xx
b
T
eTee
x 18.0
36.0)09.0()09.0(
ln
1
70.12270.170.1
(A1-2)
where:
p
=
peak absorption coefficient, cm
1
,
b
=
baseline absorption coefficient, cm
1
,
x = thickness, cm,
T
p
= peak transmittance, and
T
b
= baseline transmittance.
A1-3.2 Calculate the net absorption coefficient,
O
, due to interstitial oxygen:
bpO
(A1-3)
A1-3.3 Calculate the interstitial oxygen content of the silicon slice as follows:
O
28.6 atomic ppm ion,concentratoxygen alInterstiti
(A1-4)
or
O
173
1014.3 atoms/cm density, umeoxygen vol alInterstiti (A1-5)
A1-3.4 This value of oxygen content is based on the IOC-88 calibration factor. If desired, calculate the interstitial
oxygen content in terms of any other standardized calibration factor using the appropriate conversion factor in SEMI
M44.
A1-4 Report
A1-4.1 Report the following information:
A1-4.1.1 The instrument used, the operator and the date of the measurements,
A1-4.1.2 Test method and baseline used (SEMI MF1188, Long Baseline),
SEMI MF1188 © SEMI 2003, 2005 12
A1-4.1.3 Identification of test and reference specimens,
A1-4.1.4 Temperature of the spectrophotometer chamber,
A1-4.1.5 Thickness of test and reference specimens,
A1-4.1.6 Location and size of the illuminated area on the specimen,
A1-4.1.7 Apodization function used (FT-IR instruments),
A1-4.1.8 Spectral full width at half maximum of the absorption peak,
A1-4.1.9 Area of specimen illuminated,
A1-4.1.10 W
p
, wavenumber of the absorption peak, in cm
1
,
A1-4.1.11 The absorption coefficient due to interstitial oxygen,
o
, in cm
1
,
A1-4.1.12 Oxygen concentration, in ppm or in atoms/cm
3
, and
A1-4.1.13 The calibration factor used (IOC-88 recommended).
A1-5 Precision
A1-5.1 The precision of this test method depends upon the thickness of the test specimen and its oxygen content.
The single instrument repeatability of this test method was studied in an international experiment, in which the
oxygen contents of equivalent sets of 20, 2 mm thick samples, with interstitial oxygen content ranging from 5 ppma
to 30 ppma (IOC-88), were measured by 18 different laboratories. The single instrument repeatability of this test
method, pooled over all 20 specimens in the test set, ranged from 0.4 to 1.2% (R1S) for the 18 laboratories in the
study.
1
A1-5.2 The multilaboratory reproducibility for the same sets of test specimens was determined in the same study,
with 18 participating laboratories, to be ± 3% (R1S).
1
A1-6 Bias
A1-6.1 This experiment also included measurements of the absolute oxygen content by a variety of physical
methods. The uncertainty in the absolute determinations of oxygen content in silicon during the Grand Round
Robin results primarily from the uncertainty in the chemical analysis measurements and any variations in the oxygen
content of the various slices used in the test. The first of these is estimated to be about 6%, and the second is
estimated to be much smaller. This uncertainty directly affects the assigned value of the IOC-88 calibration factor.
Errors in this calibration factor cause errors in the value of the derived oxygen content. Therefore, the bias of these
measurements from these sources is estimated not to exceed 6%.
A1-6.2 There is also the possibility of bias because of interfering peaks in the infrared spectrum at the
wavenumbers where the baseline is determined. The magnitude of this bias varies from sample to sample and
cannot be predicted.
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consent of SEMI.
SEMI MF1239-0305 © SEMI 2003, 2005 1
SEMI MF1239-0305
TEST METHOD FOR OXYGEN PRECIPITATION CHARACTERISTICS
OF SILICON WAFERS BY MEASUREMENT OF INTERSTITIAL OXYGEN
REDUCTION
These test methods were technically approved by the Global Silicon Wafer Committee and are the direct
responsibility of the North American Silicon Wafer Committee. Current edition approved for publication by
the North American Regional Standards Committee on December 10, 2004. Initially available at
www.semi.org January 2005; to be published March 2005. Original edition published by ASTM
International as ASTM F 1239-89. Last previous edition SEMI MF1239-02.
1 Purpose
1.1 Oxide precipitates in the bulk of a silicon wafer can act as gettering sites for contamination that may be
introduced during manufacture of circuits and devices. This contamination (usually metallic impurities), if not
gettered, can reduce device manufacturing yields and degrade device or circuit performance. Thus, the oxygen
precipitation characteristics of the silicon wafer can significantly affect both yields and performance.
1.2 Although interstitial oxygen concentration is an important factor in affecting the amount of oxygen precipitation
that occurs in silicon during a specific thermal cycle, the presence of other impurities such as carbon or nitrogen, and
differences in dopant type and density, thermal history, or defect properties of the crystal can also affect the
precipitation characteristics. Thus, it is frequently necessary to choose particular material properties and preparation
techniques to obtain the desired precipitation characteristics for a particular application.
1.3 This test method may be used to compare the oxygen reduction of two or more groups of silicon wafers. This
test method is based on thermal cycles that simulate certain common device processing cycles.
1.3.1 Cycle A, a one-step precipitation cycle, provides an indication of the native nucleation sites present in the as-
received wafers.
1.3.2 Cycle B, a two-step nucleation-precipitation cycle, simulates the precipitation that occurs in normal n-MOS
device processing.
1.4 These test methods may be used to compare qualitatively the precipitation characteristics of two or more groups
of wafers.
1.5 These test methods may also be used to determine the uniformity of oxygen reduction across a wafer (in
conjunction with SEMI MF951) or from wafer to wafer within a lot.
2 Scope
2.1 These test methods cover complementary procedures for testing the oxygen precipitation characteristics of
silicon wafers. It is assumed that the precipitation characteristics are related to the amount of interstitial oxygen lost
during specified thermal cycles.
2.2 These test methods may be applied to any n- or p-type Czochralski silicon wafers of any orientation whose
thickness, resistivity, and surface finish are such as to permit the oxygen concentration to be determined by infrared
absorption and whose oxygen concentration is such as to produce measurable oxygen loss.
2.3 These test methods are not suitable for determining the width or characteristics of a “denuded zone,'' a region
near the surface of a wafer that is essentially free of oxide precipitates.
2.4 Because these test methods are destructive, suitable sampling techniques must be employed.
2.5 Determination of material performance in actual device fabrication situations is beyond the scope of these
methods. However, by comparing the results of these tests with actual device yields and performance, criteria for
selection of specific material characteristics may be established.
2.6 The values stated in SI units are regarded as standard.