semi合集-English.pdf - 第7310页
SEMI MF1188 © SEMI 2003, 2005 4 5.2.1 certified reference material (CRM) , n — a reference material, o ne or m ore of whose prope rty values are certified by a technically valid procedure , accompanied by or traceable to…
SEMI MF1188-0305 © SEMI 2003, 2005 3
3 Limitations
3.1 The oxygen absorption band overlaps a silicon lattice band. The oxygen-free reference specimen must be
matched within ±0.5% to the thickness of the test specimen in order to properly remove the effects of the silicon
lattice absorption.
3.2 Since both the oxygen band and the lattice band can change with the specimen temperature, the temperature
inside the spectrophotometer sample compartment must be maintained at 27 ± 5°C during the measurement.
3.3 Significant free carrier absorption occurs in n-type silicon with resistivity below 1 ·cm, and in p-type silicon
with resistivity below 3.0 ·cm. For test specimens below these resistivities, the reference crystal must be matched
in resistivity as well as in thickness. The resistivity match must be sufficiently close so that the transmittance of the
test specimen relative to the reference specimen at 1600 cm
1
must be 100 ± 5 %.
3.4 The free carrier absorption in n-type crystals with resistivities less than 0.1 ·cm, or in p-type crystals with
resistivities less than 0.5 ·cm reduces the available energy below that required for the satisfactory operation of
most spectrophotometers.
3.5 The full width at half maximum (FWHM) of the oxygen-in-silicon band at 300 K is 32 cm
1
. Calculations
made from spectral data having a FWHM greater than this value may be in error.
4 Referenced Standards
4.1 SEMI Standards
SEMI C29 — Specifications and Guideline for 4.9% Hydrofluoric Acid 10:1 v/v
SEMI M44 — Guide to Conversion Factors for Interstitial Oxygen in Silicon
4.2 ASTM Standards
E 1 — Specification for ASTM Thermometers
7
E 131 — Terminology Relating to Molecular Spectroscopy
8
E 932 — Practice for Describing and Measuring Performance of Dispersive Infrared Spectrophotometers
8
F 121— Test Method for Intersititial Atomic Oxygen Content of Silicon by Infrared Absorption
9
4.3 JEITA (formerly JEIDA) Standard
EM-3504 (61) — Standard Test Method for Interstitial Atomic Oxygen Content of Silicon by Infrared Absorption
10
4.4 DIN Standard
50438/1 — Determination of Impurity Content in Silicon by Infrared Absorption: Oxygen
11
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 For definitions of terms relating to absorption spectroscopy, refer to ASTM Terminology E 131.
5.2 Definitions
7 Annual Book of ASTM Standards, Vol 14.03, ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. Telephone: 610-
832-9500, Fax: 610-832-9555, Website:
www.astm.org
8 Annual Book of ASTM Standards, Vol 03.06.
9 Withdrawn in 1988; last available edition in the 1987 edition of Annual Book of ASTM Standards, Vol 10.05.
10 Japan Electronics and Information Technology Industries Association, 3
rd
floor, Mitsui Sumitomo Kaijo Bldg. Annex, 11, Kanda-Surugadai
3-chome, Chiyoda-ku, Tokyo 101-0062, Japan, Website:
www.jeita.or.jp
.
11 Deutches Institut für Normung e.V., standards are available in both English and German editions from Beuth Verlag GmbH,
Burggrafenstrasse 6, 10787 Berlin, Germany, Telephone: 49.30.2601-0, Fax: 49.30.2601.1263, Website:
www.din.de
.
SEMI MF1188 © SEMI 2003, 2005 4
5.2.1 certified reference material (CRM), n — a reference material, one or more of whose property values are
certified by a technically valid procedure, accompanied by or traceable to a certificate or other documentation issued
by a certifying body.
5.2.2 dispersive infrared (DIR) spectrophotometer, n — a type of infrared spectrometer that uses at least one prism
or grating as the dispersing element, in which the data are obtained as an amplitude-wavenumber (or wavelength)
spectrum.
5.2.2.1 Discussion — Some dispersive infrared spectrometers are used in conjunction with a computer, which is
used to store data. The data are then accessible for manipulation or computation, as required. These spectrometers
are referred to as computer-assisted dispersive infrared spectrophotometers (CA-DIR). Dispersive infrared
spectrometers that are not computer-assisted are referred to, for convenience, as simple dispersive infrared
spectrometers (S-DIR).
5.2.3 Fourier transform infrared (FT-IR) spectrophotometer, n — a type of infrared spectrometer in which the data
are obtained as an interferogram.
5.2.3.1 Discussion — An interferogram is a record of the modulated component of the interference signal measured
by the detector as a function of retardation in the interferometer. This interferogram is then subjected to a Fourier
transformation to obtain an amplitude-wavenumber (or wavelength) spectrum. Due to the complexity of the Fourier
transformation, FT-IR instruments are always used in conjunction with a computer.
5.2.4 reference spectrum, n — the spectrum of the reference specimen.
5.2.4.1 Discussion — In true double-beam spectrometers, the reference spectrum may be obtained directly, with the
reference specimen in the sample beam, and the reference beam empty. In single-beam spectrometers, it can be
calculated from the ratio of a spectrum obtained with the reference specimen in the IR beam, to a background
spectrum.
5.2.5 sample spectrum, n — the spectrum of the test specimen.
5.2.5.1 Discussion — In true double-beam spectrometers, the sample spectrum may be obtained directly, with the
sample specimen in the sample beam, and the reference beam empty. In single-beam spectrometers, it can be
calculated from the ratio of a spectrum obtained with the test specimen in the IR beam, to a background spectrum.
6 Summary of Test Method
6.1 The relative infrared transmittance spectrum of an oxygen-containing silicon slice is obtained using a reference
method with a calibrated IR spectrophotometer, preferably one calibrated by means of a suitable set of reference
materials. The oxygen-free reference specimen is matched closely in thickness to the test specimen, so as to
eliminate the effects of absorption due to silicon lattice vibrations.
6.2 After conducting selected instrumental checks, the infrared transmittance spectrum is measured over the
wavenumber range from 900 cm
1
to 1300 cm
1
.
6.3 The measured absorption coefficient of the 1107 cm
1
oxygen-in-silicon band is then used to determine the
interstitial oxygen content of the silicon slice.
7 Apparatus
7.1 Infrared Spectrophotometer , either a DIR (S or CA), or FT-IR instrument, as described in ¶5.2.2 and ¶5.2.3,
respectively, may be used. It must be possible to set the resolution of the spectrophotometer to 4 cm
1
, or better, for
FT-IR spectrophotometers, and to 5 cm
1
, or better, for DIR spectrophotometers. Use of an FT-IR spectropho-
tometer is strongly recommended.
7.2 The three following paragraphs apply only to FT-IR spectrophotometers:
7.2.1 Zero Filling — When an FT-IR instrument collects an unsymmetrical interferogram, an additional set of
points whose values are all zero shall be added to the end of the collected interferogram such that the total number of
points for performing the Fourier transform is double the number of data points originally collected.
7.2.2 Undersampling — The data collection method shall produce interferograms which, when zero-filled and
Fourier transformed, produce a spectrum containing at least two data points per resolution increment. For example,
SEMI MF1188-0305 © SEMI 2003, 2005 5
after transformation, a spectrum obtained at 4 cm
1
resolution shall contain at least one data point every two
wavenumbers.
7.2.3 Phase Correction — The phase correction routine used during Fourier transformation shall use at least 200
points on both sides of the point of zero retardation in order to produce a phase array that can be used to eliminate
phase errors.
12
7.3 Specimen Holders of Appropriate Size — If the specimen being measured is small, it must be mounted in a
holder that has an opening small enough to prevent any of the infrared beam from bypassing the specimen. The
specimens shall be held normal, or nearly normal, to the axis of the incident infrared beam (see ¶8.3).
7.4 Equipment and Materials, for slicing and polishing crystals to a thickness similarity of 0.5% or less and a
surface flatness of 2.25 m or better (one fourth the wavelength at the maximum absorption of the interstitial
oxygen impurity band).
7.5 Acid Fume Hood and Suitable Protective Gear, for use when stripping oxide films from specimens for
measurement.
7.6 Micrometer Caliper, or other instrument suitable for the measurement of the thickness of the specimens to a
tolerance of ±0.2%.
7.7 Thermocouple-Millivolt Potentiometer, or other system suitable for measurements of the specimen temperature
during test.
7.8 Hydrofluoric Acid, 4.9% (10:1 v/v), in accordance with Grade 2 of SEMI C29.
NOTE 1: Warning — The acids used in this test method are hazardous. All precautions normally used with these chemicals
should be strictly observed. Obtain and read the Material Safety Data Sheet prior to the use of any chemical.
8 Testing of the Apparatus
8.1 Evaluate the performance of S-DIR spectrometers according to Instrument Operation and Nature of Test
Sections of ASTM Practice E 932. Follow the appropriate paragraphs of these sections to evaluate the performance
of CA-DIR instruments.
8.2 Verify a proper purge condition for the specimen chamber by monitoring water vapor or carbon dioxide
absorption bands. The water vapor line is monitored at 1521 cm
1
and the carbon dioxide line at 667 cm
1
. The
instrument shall be sufficiently well purged or evacuated that the transmittance at these locations is between 98 and
102%.
8.3 Under certain conditions, the spectrophotometer may have a nonlinear response, or be plagued by undesirable
extraneous reflections between the specimen surfaces and the spectrometer components. Place a flat, double-side
polished and high resistivity (greater than 5 ·cm) silicon slice in the instrument. The effective transmittance of the
silicon slice, due to reflective losses at the silicon surfaces, should be 53.8% ± 2% in the 1600 cm
1
to 2000 cm
1
region. In some instruments, this silicon slice may have to be placed at a small angle to the axis of the incoming IR
beam, in order to minimize undesirable reflections between the silicon surfaces, and the spectrometer components.
This angle may be determined by initially placing the silicon slice normal to the axis of the incoming beam and then
gradually tilting the sample while repeatedly obtaining the transmittance spectrum of the slice above 1600 cm
1
.
The optimum angle is reached when a flat baseline as close as possible to 53.8% ± 2% is obtained from 1600 cm
1
to
4000 cm
1
. This optimum angle is typically less than 10°.
9 Calibration Specimens
9.1 Obtain a set of certified reference materials (CRMs) for interstitial oxygen in silicon with the following
characteristics:
9.1.1 Each specimen in the set is double-side polished and approximately 2 mm thick,
9.1.2 The set covers the oxygen range of interest with three or more samples,
12 For a discussion of the phase correction computation, see Chase, D. B., Applied Spectroscopy 36, 240 (1982).