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SEMI M1-0305 © SEMI 1978, 2005 46 are made at room temperature and recom bination lifet ime if they are made at elevated te mperature (50  to 75  C). The test specime ns required for t his test method ca n be made by p…

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SEMI M1-0305 © SEMI 1978, 2005 45
R2-2.3 JEITA (formerly JEIDA) Standard
2
EM-3505 — Height Calibration in 1 nm Order for AFM
R2-2.4 DIN Standards
4
50430 — Measurement of the Electrical Resistivity of Silicon or Germanium Single Crystals in Bars by Means of
the Two-point-probe Direct Current Method
50444 — Conversion Between Resistivity and Dopant Density; Silicon
R2-2.5 ANSI Standard
5
ANSI/ASME B46.1 — Surface Texture (Surface Roughness, Waviness, and Lay)
R2-2.6 ISO Standards
6
ISO 4287/1 — Surface Roughness – Terminology – Part 1: Surface and its Parameters
ISO 14644/1 — Clean Room and Associated Controlled Environments — Classification of Air Cleanliness
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
R2-3 General Characteristics
R2-3.1 Crystal Orientation—The crystallographic orientation of the source crystal can be determined by the x-ray
methods of SEMI MF26, JEITA EM-3501, or DIN 50433/1, the optical method of SEMI MF26 or DIN 50433/2, or
the Laue method of DIN 50433/3. X-ray methods are most commonly used by wafer suppliers.
{Need some
discussion here about differences between MF26 and EM-3501}}
R2-3.2 Conductivity Type—One of the five methods of SEMI MF42, one of the methods of JIS H 0607, or one of
the four methods of DIN 50432 should be used to determine conductivity type. This quantity is generally well
controlled by silicon wafer suppliers and is not usually verified on incoming.
R2-3.3 Many of these tests need to be carried out in cleanroom environments of ISO Class 4, 5, or 6 depending on
the cleanliness requirements. These classes are defined in ISO 14664-1.
R2-4 Electrical Characteristics
R2-4.1 Resistivity of wafers is most appropriately determined for referee purposes by SEMI MF84 or DIN 50431.
Under some circumstances these tests may be considered destructive, and an alternative means may be required.
One nondestructive test is SEMI MF673, having a range from 0.0001 to 100 ·cm. Another nondestructive test is
SEMI MF398, which is limited to carrier concentrations in the ranges from 1.5 × 10
18
to 1.5 × 10
21
cm
3
for n-type
silicon and from 3 × 10
18
to 5 × 10
20
cm
3
for p-type silicon, and has only moderate inter-laboratory precision. Other
older methods that require a bar-shaped test specimen include SEMI MF43 and DIN 50430; these methods are no
longer in general use. It is also possible to establish the dopant density from room temperature measurements in
silicon using SEMI MF723 (for boron, phosphorus, or arsenic doped silicon) or DIN 50444 (for boron and
phosphorus doped silicon only). SEMI MF1527 is a useful standard in describing ways of ensuring that resistivity
measuring instruments are performing correctly.
R2-4.2 Radial Resistivity Variation is generally determined by SEMI MF81 or DIN 50435. These test methods use
several different measurement positions so the desired position must be specified. It is also possible to measure the
resistivity in one of the circular patterns specified in SEMI MF1618 using SEMI MF1529 as the resistivity
measurement method.
R2-4.3 Resistivity Striations can generally be viewed visually using one of the techniques discussed in Section R2-
9. For an electrical measurement, spreading resistance (SEMI MF525) is generally employed but this is strictly an
off-line measurement.
R2-4.4 Minority Carrier Lifetime can be measured by a number of methods. The photoconductive decay methods
(SEMI MF28, JIS H 0604, and DIN 50440/1 all require the use of special test specimens; Microwave reflectivity
measurements (SEMI MF1535 and JEITA EM-3502) are applicable to measurements on wafers, but special surface
passivation procedures may be required to obtain meaningful results. Minority carrier lifetime may also be inferred
from measurements made in accordance with SEMI MF1388, which yields generation lifetime if the measurements
SEMI M1-0305 © SEMI 1978, 2005 46
are made at room temperature and recombination lifetime if they are made at elevated temperature (50 to 75C).
The test specimens required for this test method can be made by procedures compatible with typical wafer
processing.
R2-5 Chemical Characteristics
R2-5.1 Oxygen Concentration in relatively high resistivity specimens (
> 1 to 3 ·cm at room temperature) should
be measured by infrared techniques. SEMI MF1188, JEITA EM-3504, and DIN 50438 all utilize approximately
normal incidence illumination and the IOC-88 calibration factor to determine the interstitial oxygen content. See
SEMI M44 for a discussion of other calibration factors and their relationship to IOC-88. SEMI MF1619 uses p-
polarized radiation, incident at the Brewster angle to reduce the multiple reflections from polished wafers. For more
heavily doped wafers, secondary ion mass spectrometry (SIMS, SEMI MF1366) and gas fusion analysis (GFA) can
be used to determine total oxygen content. There is no standardized method for performing GFA, and the
repeatability of this technique is generally poorer than SIMS.
R2-5.2 Radial Oxygen Variation should be determined by measuring the oxygen content by one of the above
methods at selected locations on the wafer defined in SEMI MF951. Usually measurements are made at the center
and at a single point on the primary flat or notch bisector 10 mm from the edge of the wafer opposite the fiducial;
this is known as test plan A-1.
R2-5.3 Carbon Concentration should be measured by SEMI MF1391, JEITA 56, and DIN 50438/2. The most
modern calibration coefficients are used in SEMI MF1391 and JEITA 56. For these methods, the test specimen
cannot be too heavily doped, and special thick test specimens may be necessary.
R2-5.4 Boron Contamination in heavily doped n-type silicon can be determined by SEMI MF1528.
R2-6 Structural Characteristics
R2-6.1 Dislocation Etch Pit Density, Slip, Lineage, Twins, and Swirl are usually displayed by etching and visual or
microscopic observation. JIS H 0609 is a comprehensive test method for carrying out this procedure with the use of
non-chromic etchants. SEMI MF1809 also recommends non-chromic etchants for this test. For the full procedure,
SEMI MF1809 must be used with other standards including SEMI MF1726 and SEMI MF1810. DIN 50434 is an
older, but comprehensive test procedure to observe these and other structural defects based on chrome-containing
etchants. It is also possible to observe these defects by x-ray topography using DIN 50443/1.
R2-6.2 Shallow Pits can be exposed by the relatively low temperature heating cycle and procedures in SEMI
MF1049 if they are present in sufficient density, but testing for shallow pits in production environments is usually
carried out using the temperature cycle in SEMI MF1727 followed by etching with etchants discussed in SEMI
MF1809, examination by SEMI MF1726, and counting by SEMI MF1810. They can also be observed by using JIS
H 0609.
R2-6.3 Oxidation Induced Stacking Faults (OISF) can be observed by using JIS H 0609, or by using the
temperature cycle in SEMI MF1727 followed by etching with etchants discussed in SEMI MF1809, examination by
SEMI MF1726, and counting by SEMI MF1810. OISF can also be observed by x-ray topography using DIN
50443/1 following thermal treatment according to JIS H 0609 or SEMI MF1727.
R2-6.4 Oxide Precipitates (Bulk Micro Defects, BMD) are generated with the use of a temperature cycle such as
those in SEMI MF1239. The amount of precipitation can be measured by the oxygen reduction method of SEMI
MF1239 or by direct observation by infrared that has not yet been standardized.
R2-6.5 Bulk Defects can be detected by x-ray topography in accordance with DIN 50443/1.
R2.7 Dimensional Characteristics
R2-7.1 Diameter is presently very well controlled in silicon wafers that have been edge profiled with cam follower
equipment. For three-point measurements at locations defined by SEMI MF2074 and, except for positions on 150
mm diameter, n-type (100) wafers, by DIN 50441/4. The latter utilizes a measuring or projection microscope to
make the diameter measurements, but the former allows a dial gauge or any other equally accurate method of
dimensional measurement.
SEMI M1-0305 © SEMI 1978, 2005 47
R2-7.2 Flat Length should be determined by SEMI MF671. If flat diameter is specified instead of flat length, it can
be determined by ¶6.2.1 of DIN 50441/4 or by a dial gauge method as agreed upon between the supplier and
customer. Both SEMI MF671 and DIN 50441/4 take account of the possibility that the ends of the flat might be
rounded.
R2-7.3 Notch Dimensions should be determined by SEMI MF1152 (see Figure 5).
R2-7.4 Flat Orientation can be confirmed by SEMI MF847. There is no standardized method for determining the
crystallographic orientation of the diameter that bisects the notch.
R2-7.5 Edge Profile is usually determined by using one of the two templates (see Figure 6) with Method B of SEMI
MF928 or Procedure 2 of DIN 50441/2, both of which are nondestructive. The other two procedures in these
methods are destructive and not so widely used.
R2-7.6 Thickness is usually determined at the center point of the wafer with the use of SEMI MF1530, an
automated technique. Manual techniques originally used in the industry include SEMI MF533, JIS H 0611, and
DIN 50441/1.
NOTE 2: Test methods SEMI MF1530 (for thickness, thickness variation, and flatness), SEMI MF1451 (for sori), and SEMI
MF1390 (for warp) may not be suitable for use on large diameter wafers with polished back surfaces. New standardized test
methods for measuring these parameters on such wafers are under development.
R2-7.7 Total Thickness Variation (TTV) was originally determined with the use of manual 5-point techniques
covered in SEMI MF533, JIS H 0611, and DIN 50441/1. JIS H 0611 differs from SEMI MF533 and DIN 50441/1,
in that the measurements in JIS H 0611 are taken at the center and at 5 mm from the edge on diameters parallel and
perpendicular to the primary flat or notch bisector, while the measurements in SEMI MF533 and DIN 50441/1 are
taken at the center and at 6 mm from the edge on diameters 30 degrees and 120 degrees counterclockwise from the
bisector to the primary flat or notch (with the wafer facing front surface up). TTV can also be determined with the
use of SEMI MF657, which involves a continuous scan pattern over a portion of the wafer surface. Currently,
however, it is most frequently determined using SEMI MF1530, which involves an automated continuous scan
pattern over the entire wafer surface. In this case, the quantity determined is equal to the global flatness GBIR (see
Appendix 1 and Note 1, above).
R2-7.8 Surface Orientation can be determined by the x-ray methods of SEMI MF26, JEITA EM-3501, or DIN
50433/1, the optical method of SEMI MF26 or DIN 50433/2, or the Laue method of DIN 50433/3.
R2-7.9 For off-orientation {111} wafers, the orthogonal misorientation is specified for each of the wafer categories
in Tables 4 through 9. There is no standardized measurement method for this property so it should be determined by
a method agreed upon between supplier and customer.
R2-7.10 Bow can be determined with the manual methods SEMI MF534 and JIS H 0611. Currently, bow is not as
widely used a parameter as warp.
R2-7.11 Warp is currently most often measured with the use of SEMI MF1390, which is an automated method with
full surface scan and correction for gravitational sag. It can also be measured with the use of the contactless manual
method SEMI MF657, in which the prescribed scan pattern covers only a portion of the wafer surface in which there
is no correction for gravitational sag. As noted in Appendix 2, different reference planes are used for the two
methods. Because SEMI MF657 employs a back surface reference plane, the measured warp may include
contributions from thickness variation of the wafer. SEMI MF1390 employs a median surface reference plane and
is not susceptible to interferences from thickness variations. In general, the latter is preferred, especially for wafers
150 mm in diameter and larger (see Note 1, above).
R2-7.12 Sori , which is sometimes specified in lieu of bow or warp or both, can be determined by SEMI MF1451
(see Note 1, above).
R2-7.13 Global Flatness can be determined by either capacitance measurements, as in SEMI MF1530, or by
multiple beam interference, as in DIN 50441/3. Generally, the former is considered to be more reliable, especially
as the need increases for measuring smaller flatness deviation (see Note 1, above). As noted in ¶R2-7.7, GBIR is the
same as TTV; other global flatness parameters are discussed in Appendix 1.