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SEMI MF1239-0305 © SEMI 2003, 2005 3 6 Summary of Test Method 6.1 A representative sam ple is selected from each group of wafers to be tested. 6.2 The initial val ue of interstitial oxygen concentration is measured by th…

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SEMI MF1239-0305 © SEMI 2003, 2005 2
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health guides and determine the
applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 All factors that affect the infrared absorption measurement (including differences in back surface condition,
instrumental characteristics, and wafer resistivity) may cause errors in the determination of oxygen reduction.
3.2 If significant quantities of oxygen are outdiffused during the thermal cycles, the measured oxygen reduction
may not be representative of the amount of oxygen precipitation.
3.3 If precipitate size varies from sample to sample, the variations in measured oxygen reduction may not be
representative of variations in the number of oxide precipitates that are formed.
3.4 The specified thermal cycles may or may not provide adequate simulation of the cycles used in a particular
device processing sequence. The results obtained in these test methods can serve as predictors of those expected in
actual device processing only to the extent that the simulation is representative of the device process.
4 Referenced Standards
4.1 SEMI Standards
SEMI C28 — Specifications and Guidelines for Hydrofluoric Acid
SEMI C29 — Specifications and Guideline for 4.9% Hydrofluoric Acid 10:1 v/v
SEMI C54 — Specifications and Guidelines for Oxygen
SEMI C59 — Specifications and Guidelines for Nitrogen
SEMI M59 — Terminology for Silicon Technology
SEMI MF951 — Test Method for Determination of Radial Interstitial Oxygen Variation Silicon Wafers
SEMI MF1188 — Test Method for Interstitial Atomic Oxygen Content of Silicon by Infrared Absorption with Short
Baseline
SEMI MF1619 — Test Method for Measurement of Interstitial Oxygen Content of Silicon Wafers by Infrared
Absorption Spectroscopy with p-Polarized Radiation Incident at the Brewster Angle
4.2 ASTM Standard
D 5127 — Guide for Ultra Pure Water Used in the Electronics and Semiconductor Industry
1
4.3 JEITA (formerly JEIDA) Standard
EM-3504 (61) — Standard Test Method for Interstitial Atomic Oxygen Content of Silicon by Infrared Absorption
2
4.4 DIN Standard
50438/1 — Determination of Impurity Content in Silicon by Infrared Absorption: Oxygen
3
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 For definitions of terms relating to silicon technology, refer to SEMI M59.
1 Annual Book of ASTM Standards, Vol 11.01, ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. Telephone: 610-
832-9500, Fax: 610-832-9555, Website:
www.astm.org
2 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, Telephone: 81.3.3518.6434, Fax: 81.3.3295.8726, Website:
www.jeita.or.jp
.
3 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.beuth.de
.
SEMI MF1239-0305 © SEMI 2003, 2005 3
6 Summary of Test Method
6.1 A representative sample is selected from each group of wafers to be tested.
6.2 The initial value of interstitial oxygen concentration is measured by the infrared absorption method at the
desired points on each wafer.
6.3 The wafers are passed through one of two simulation thermal cycles. Cycle A consists solely of a precipitation
step. Cycle B consists of a nucleation step followed by a precipitation step.
6.4 After the thermal cycle, the oxide film is stripped and the final value of oxygen concentration is measured at the
same points on each wafer using the same technique and instrumentation as was used to determine the initial value.
6.5 The oxygen reduction is determined for each wafer (or for each point on each wafer) tested as the difference
between the initial and final values.
6.6 If all samples have the same initial oxygen concentration (within a narrow range), the average oxygen reduction
for each test condition (such as, group or position on wafer) is computed, and the appropriate comparisons made.
6.7 If the samples have initial oxygen concentrations that cover a relatively wide range, a plot of oxygen reduction
against initial oxygen concentration is made for each group or position. Again appropriate comparisons can be
made.
7 Apparatus
7.1 Infrared Absorption Spectrophotometer, as specified in SEMI MF1188 or DIN 50438, Part 1.
7.2 Resistance Heated Tube Furnace, capable of providing temperatures in the range from 750°C to 1050°C to
±2°C over the length required to contain the load of wafers to be tested. The furnace shall be fitted with the
following:
7.2.1 Gas Manifold — That allows dry oxygen and nitrogen to be mixed at the required ratios and flows, (see Table
1);
Table 1 Thermal Cycle Tests for Oxygen Precipitation in Silicon
Parameter Value
Test A 1050°C for 16 h
Test B 750°C for 4 h followed by 1050°C for 16 h
Furnace Ambient Nitrogen plus 5% dry oxygen
Gas Flow Rate 4.2 ± 0.2 L/min
#1
Push/Pull Temperature 750°C
Push/Pull Rate 25 cm/min
Ramp Up Rate 10°C/min
Ramp Down Rate 5°C/min
#1
For 155 mm diameter tube; for other diameters flow rate should be proportional to the cross sectional area of the tube.
7.2.2 Quartz, Polysilicon, or Silicon Carbide Tube — Of diameter appropriate for the wafers to be tested to isolate
the wafers from external contamination;
7.2.3 Quartz Boats — To hold the wafers during processing;
7.2.4 Loader — To allow controlled insertion of the quartz boat into the hot zone, (see Table 1); and
7.2.5 Laminar Flow Load Station — To permit loading of the wafers without adding contamination to the surfaces.
7.3 Facilities for processing wafers through chem-mechanical polishing, or bright acid etching to provide smooth,
flat surfaces.
7.4 Facilities for dipping the wafers in hydrofluoric acid prior to the oxygen determination in order to remove the
surface oxide film grown during thermal cycling. Suitable protective clothing, acid disposal facilities, and
ventilation shall be provided.
SEMI MF1239-0305 © SEMI 2003, 2005 4
7.5 Facilities for cleaning and drying wafers by a standard process as customarily used in the laboratory performing
the test.
7.6 Scribe or Laser Marker — For marking the wafers with unique identification (unless premarked wafers are
available).
8 Reagents and Materials
8.1 Hydrofluoric Acid — In accordance with SEMI C28, Grade 1.
8.2 Oxygen — In accordance with grade 2.5 of SEMI C54.
8.3 Nitrogen — In accordance with grade 5.2 of SEMI C59.
8.4 Deionized Water — With purity equal to or greater than that specified for Type E-1 in ASTM Guide D 5127.
9 Hazards
9.1 The acids used in these test methods are hazardous. All precautions normally used with these chemicals should
be strictly observed. Obtain and read the material safety data sheet prior to use of any chemical.
10 Selection and Preparation of Test Specimens
10.1 Choose test wafers from each group being tested in such a way as to cover the entire range of oxygen
concentration found in the group. Choose at least two wafers with oxygen concentration in each 0.5 ppm (IOC-88)
4
interval in the range. For example, if the oxygen concentration range of a group is 3 ppma, at least 12 wafers from
that group should be tested.
10.2 Select or prepare test wafers with thickness, resistivity, and surface finish as required by the oxygen test
method being used.
10.3 Identify each test wafer individually with an alphanumeric laser marking or a hand scribed code unless pre–
marked wafers are used.
10.4 Prepare the wafers in accordance with SEMI MF1188, SEMI MF1619, DIN 50 438/1, or JEITA EM-3504, as
applicable.
11 Procedure
11.1 Determine the initial interstitial oxygen concentration of each wafer to be tested at the center in accordance
with SEMI MF1188, SEMI MF1619, DIN 50 438/1, or JEITA EM-3504. If desired, measure the interstitial oxygen
concentration at other locations on each wafer as specified by an appropriate pattern in SEMI MF951. Record the
oxygen value(s), the wafer identification, and measurement locations. Record the date of the test and the instrument
used in measuring the oxygen concentration. See Figure 1 for a suggested data sheet format.
11.2 Clean and dry the wafers in accordance with the usual wafer cleaning procedure employed by the laboratory
performing the test.
11.3 Process the samples as soon after cleaning as possible. If the samples must be stored between cleaning and
processing, store in clean covered cassettes.
11.4 Heat-treat in accordance with Cycle A or Cycle B, (see Table 1). Record the date of the heat treatment and the
cycle used.
11.5 Strip the surface oxide from the wafers with hydrofluoric acid (HF), and thoroughly clean and dry them with
the usual wafer cleaning procedure employed by the laboratory performing the test.
11.6 Measure the post-heat treatment interstitial oxygen concentration at each point measured before heat treatment.
Use the same instrument, test method, and set up for this measurement as was used for the initial measurement.
Record each final oxygen concentration on the same data sheet as was used to record initial oxygen concentration.
4 As defined in SEMI MF1188, SEMI MF1619, DIN 50 438/1, or JEITA EM-3504.