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SEMI MF951-0305 © SEMI 2003, 2005 7 12 Precision 12.1 The test m ethod precision is directly depen d ent on the preci sion of the individual oxy gen measurem ents. If the only sources of precision errors are the i ndivid…
SEMI MF951-0305 © SEMI 2003, 2005 6
10.1.2 Test Plan B — Three Positions (Center and Two Edges, Figure 2):
100
ValueCenter
ValueCenter Values) Edge of (Avg
ROV (2)
10.1.3 Test Plan B1 — Five Positions (Figure 2):
10.1.3.1 ROV is the larger of the values found from Equation 2 and from the following:
100
ValueCenter
ValueCenter Values) R/2 of (Avg
ROV
(3)
10.1.4 Test Plan C — Five Positions (Figure 3):
100
ValueCenter
ValueCenter Values) Edge of (Avg
ROV
(4)
10.1.5 Test Plan D — Multiple Positions (Figure A1-4):
100
ValueCenter
Value Low IndividualValue)High Individual
ROV
(5)
NOTE 2: All edge positions are located from the center of the IR beam to the slice edge. All other non-center positions are
located such that the center of the IR beam is located as given by the dimensions in Figures 1–4.
10.2 For referee tests, calculate the ROV for each of the five determinations and calculate the average ROV as
follows:
5
54321
ROVROVROVROVROV
ROV
(6)
where ROV
i
is the ROV calculated from the i
th
measurement.
11 Report
11.1 Report the following information:
11.1.1 Date, operator, and affiliation,
11.1.2 Description of test method used,
11.1.3 Number of slices and their identification,
11.1.4 Sample descriptions including nominal resistivity, thickness, diameter, and surface finishes,
11.1.5 Sample plan used,
11.1.6 Instrument factors,
11.1.6.1 Manufacturer/model,
11.1.6.2 Resolution,
11.1.6.3 Apertured beam size,
11.1.6.4 Differential or air reference method,
11.1.6.5 Measurement wavelength region,
11.1.7 ROV results, and
11.1.8 Any unusual relevant conditions.
SEMI MF951-0305 © SEMI 2003, 2005 7
12 Precision
12.1 The test method precision is directly dependent on the precision of the individual oxygen measurements. If the
only sources of precision errors are the individual measurements, the radial oxygen variation precision can be
computed for each sampling plan.
13 Bias
13.1 No reference standards are available for oxygen variation, so it is impossible to determine bias except for that
of the individual measurements. Bias of the individual measurements should be determined in accordance with the
procedures of the test methods utilized.
14 Keywords
infrared transmission; interstitial oxygen; oxygen; radial variation; silicon; uniformity; variation
NOTICE: SEMI makes no warranties or representations as to the suitability of the standards set forth herein for any
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SEMI MF1049-0304 © SEMI 2003, 2004 1
SEMI MF1049-0304
PRACTICE FOR SHALLOW ETCH PIT DETECTION ON SILICON
WAFERS
This practice was technically approved by the Global Silicon Wafer Committee and is the direct
responsibility of the North American Silicon Wafer Committee. Current edition approved for publication by
the North American Regional Standards Committee on December 4, 2003. Initially available at
www.semi.org February 2004; to be published March 2004. Originally published by ASTM International as
ASTM F 1049-87. Last previous edition SEMI MF1049-02.
1 Purpose
1.1 High levels of etch pits are reported
1
to indicate
metallic contamination that is detrimental to wafer
processing. This can be deduced from the density of
etch pits on the surface of the wafer.
1.2 This practice is used to detect shallow etch pits that
may be related to the level of metallic impurities near
the surface of silicon epitaxial or polished wafers.
2 Scope
2.1 This practice covers detection of high densities of
shallow etch pits on silicon wafers doped either p- or n-
type and with resistivities as low as 0.005 Ω·cm. This
practice is applicable for silicon wafers cut from
crystals grown in either a (111) or (100) crystal
orientation.
2.2 This practice is not recommended for use in defect
density evaluations, but as a subjective means of
estimating defect densities and distributions on the
surface of a polished or epitaxial wafer.
NOTE 1: For determination of shallow and other defect
densities in wafer production environments, use of the
sequence of procedures in SEMI MF 1726, SEMI MF1727,
SEMI MF1809, and SEMI MF1810 is recommended.
2.3 This practice utilizes a thermal oxidation process
followed by a chemical preferential etchant to create
and then delineate shallow etch pits.
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 Etch artifacts are the primary cause of difficulty in
identifying shallow etch pits. Etch artifacts are
generated in various ways such as gas bubble formation
1 Pearce, C. W., and McMahon, R. G., “Role of Metallic Contamina-
tion in the Formation of ‘Saucer’ Pit Defects in Epitaxial Silicon,” J.
Vac. Sci. Tech., 14, 40 (1977).
during etching, improperly cleaned surface prior to
etching, or insufficient etch solution volume.
3.2 Excessive silicon staining (very dark color) during
the preferential etching may obscure or prevent the
development of shallow etch pits on heavily doped p-
type silicon material (<0.2 Ω·cm).
2
NOTE 2: Light staining will not affect subsequent defect etch
results. However, heavy stains are undesirable.
4 Referenced Standards
4.1 SEMI Standards
SEMI C54 — Specifications and Guidelines for
Oxygen
SEMI C59 — Specifications and Guidelines for
Nitrogen
SEMI C28 — Specifications and Guidelines for
Hydrofluoric Acid
SEMI M17 —Guide for a Universal Wafer Grid
SEMI MF154 — Guide for Identification of Structures
and Contaminants Seen on Specular Silicon Surfaces
SEMI MF1726 — Practice for Analysis of
Crystallographic Perfection of Silicon Wafers
SEMI MF1727 — Practice for Detection of Oxidation
Induced Defects in Polished Silicon Wafers
3
SEMI MF1809 — Guide for Selection and Use of
Etching Solutions to Delineate Structural Defects in
Silicon
SEMI MF1810 — Test Method for Counting
Preferentially Etched or Decorated Surface Defects in
Silicon Wafers
4.2 ASTM Standard
D 5127 — Guide for Ultra Pure Water Used in the
Electronics and Semiconductor Industry
3
2 Schimmel, D. G., and Elkind, M. J., “An Examination of the
Chemical Staining of Silicon,” J. Electrochem. Soc., 125, 152 (1978).
3 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