semi合集-English.pdf - 第7538页
SEMI MF1809-0704 © SEMI 2003, 2004 3 Formulati ons of the standard assay foll ow this example: A HF/HNO 3 /Acetic solution, in the 1:1:2 ratio is th e same as 25% (49% HF) + 25% (70% HNO 3 + 50% (glacial acetic) by volum…
SEMI MF1809-0704 © SEMI 2003, 2004 2
3.1.7 The samples must be free of work damage,
contamination, and other complicating residues. Clean,
specular surfaces are suitable for metallographic
examination and provide the best results. Surfaces
examined should be flat with parallel faces, to simplify
microscope inspection.
4 Referenced Standards
4.1 SEMI Standards
SEMI C18 — Specification for Acetic Acid
SEMI C28 — Specifications and Guidelines for
Hydrofluoric Acid
SEMI C35 — Specifications and Guidelines for Nitric
Acid
SEMI MF523 — Practice for Unaided Visual
Inspection of Polished Silicon Wafer Surfaces
SEMI MF1241 — Terminology of Silicon Technology
SEMI MF1725 — Practice for Analysis of
Crystallographic Perfection of Silicon Ingots
SEMI MF1726 — Practice for Analysis of
Crystallographic Perfection of Silicon Wafers
SEMI MF1727 — Practice for Detection of Oxidation
Induced Defects in Polished Silicon Wafers
SEMI MF1810 — Test Method for Counting
Preferentially Etched or Decorated Surface Defects in
Silicon Wafers
4.2 ASTM Standard
1
D 5127 — Guide for Ultra Pure Water Used in the
Electronics and Semiconductor Industry
4.3 Japan Industrial Standard
2
JIS H 0609 — Test Methods Of Crystalline Defects In
Silicon By Preferential Etch Techniques
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
5 Terminology
5.1 Defect-related terminology may be found in SEMI
MF1241.
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 Available, in Japanese language edition only, through the Japanese
Standards Association, 1-24, Akasaka 4-Chome, Minato-ku, Tokyo
107-8440, Japan. Telephone: 81.3.3583.8005; Fax: 81.3.3586.2014
Website: www.jsa.or.jp
6 Apparatus
6.1 No standard apparatus or facility satisfies the
universal needs for the various applications of these
etching solutions. Systems range from a simple HF-
resistant beaker to large etching tanks complete with
nitrogen bubblers, temperature control and nitrous
oxide and hydrofluoric acid (HF) scrubbers.
6.1.1 For larger samples (wafers or slugs), use large
etching tanks with nitrogen bubble agitation or
ultrasonic agitation. Most of the etchant solutions listed
work more effectively with the aid of agitation. Heat
exchangers or just the thermal mass of the solution can
control temperature. Large volumes of acid heat more
slowly and allow an intrinsic form of temperature
control. To reduce heating effects, maintain 1 L of
solution for each 1,000 cm
2
of sample surface area.
6.1.2 Maintain proper environmental controls. Make
provisions to dispose of nitrous oxides, HF fumes, and
any solid wastes evolved whatever system is chosen.
Chromium and copper-based etching solutions produce
solid waste and gaseous byproducts. Chromium-free
etching solutions produce no measurable solid waste
but do generate nitrous oxides and HF fumes.
7 Reagents and Materials
7.1 Purity of Reagents — Chemicals shall conform to
the assay and impurity levels of Grade 1 SEMI
Specifications where they exist. Reagents for which
SEMI specifications have not been developed shall
conform to the specifications of the Committee on
Analytical Reagents of the American Chemical
Society,
3
where such specifications are available. Other
grades may be used provided it is first ascertained that
the reagent is of sufficiently high purity to permit its
use without lessening the accuracy of the determination.
7.2 Purity of Water — Reference to water shall be
understood to mean Type E-3 or better water as
described in ASTM Guide D 5127.
7.3 Volume of components describes all solutions in
parts of a standard assay. The formulas give solid or
dissolved components in grams per 100 mm of total
solution.
7.4 All formulations employ a Standard Solution
Convention (SSC) that specifies each solution
component as an acceptable assay ± some tolerance.
3 Reagent Chemicals, American Chemical Society Specifications,
American Chemical Society, Washington, DC. For suggestions on the
testing of reagents not listed by the American Chemical Society, see
Analar Standards for Laboratory Chemicals, BDH Ltd., Poole,
Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc., (USPC), Rockville,
MD.
SEMI MF1809-0704 © SEMI 2003, 2004 3
Formulations of the standard assay follow this example:
A HF/HNO
3
/Acetic solution, in the 1:1:2 ratio is the
same as 25% (49% HF) + 25% (70% HNO
3
+ 50%
(glacial acetic) by volume. The specified chemicals
shall have the following nominal assay:
• Acetic acid, glacial >99.7%
• Chromium trioxide >98%
• Copper nitrate >98%
• Hydrofluoric acid 49± 0.25%
• Nitric acid 70 to 71%
7.5 The chemicals used in these etching solutions are
potentially harmful. Handle and use them in a chemical
exhaust fume hood, with the utmost care. Hydrofluoric
acid solutions are particularly hazardous.
7.6 Release of chromic acid or solutions of chromic
acid into domestic sewer systems is usually not
allowed. Chromates are extreme biological and
ecological hazards. Chromic acid is a strong oxidizing
agent and should not contact organic solvents or other
easily oxidized materials.
7.7 Safety or protective gear should be worn while
handling these acid solutions or their components.
Safety requirements vary, but essential items are plastic
gloves, safety glasses, face shield, acid gown, and shoe
covers. The handling of large quantities of powdered
chromic acid may require a respirator or other breathing
apparatus.
8 Procedure
8.1 Selection of Etching Solutions
8.1.1 The following tables show two broad categories
of solutions. The first group in Tables 1 and 3 includes
only chromium-free etching solutions. Although uses
may be limited, these solutions should be considered
whenever appropriate. The second group in Tables 2
and 4 includes only solutions that contain chromium
compounds. These do well for their intended
applications, but they can be harmful to the
environment. Use these highly contaminated etching
solutions with caution. Release into the environment of
hexavalent chromium waste is a recognized hazard (see
Section 7.6). Exposure can cause cancer.
NOTE 2: Copper-3 solution is also identified as “MEMC
etch” in referenced publications.
NOTE 3: Sopori and Sato etches have been suggested for
inclusion in Tables 2 and 4, and these solutions may be added
when solution information and pictures become available
from sponsors (see Related Information 2 for the
methodology by which new solutions can be added to the
guide).
8.1.2 Tables 1 and 2 list the figure numbers of the
etched defect examples for these etching solutions
together with their etching rates.
8.1.3 Tables 3 and 4 classify the suitability of each
listed etching solution for the various applications. In
the tables,
• A = Excellent,
• B = Good,
• C = Acceptable, and
• D = Unacceptable.
Each solution has advantages and disadvantages and
this guide does not endorse one in favor of another.
Selection of an etchant solution should be based upon
etch rate, etchant life, solution heating, environmental
harm, ease of interpretation, and range of use.
8.1.4 Investigate local environmental and safety
requirements before selecting an etchant solution.
Identify the sample orientation, type, resistivity level,
and primary defects of interest; this information helps
the user rank the various possible solutions and then
select the most appropriate choice.
8.1.4.1 Although this guide does not require a specific
solution, it is highly recommended that chromium-free
etching solutions should be used whenever possible, for
environmental and biological reasons.
8.2 Sample Preparation
8.2.1 Most silicon samples have residual oxide on the
surface, either thermally grown as part of the
fabrication process or occurring naturally due to
exposure to air.
8.2.2 Immediately before defect etching, submerge the
sample in concentrated HF solution for 1 min or until
the surface becomes hydrophobic to remove surface
oxide layers.
8.2.3 Rinse and hold the samples in deionized water
until transferred to the etching solution.
8.3 Defect Etching
8.3.1 No standard design for etching systems exists
(see Section 6.1). In general, the procedures defined for
the etching system available to the user of this guide
must be followed. A simple system for manual use is
as follows:
8.3.1.1 Place the specimen in the bottom of a HF-proof
beaker with the surface to be inspected facing upward.
8.3.1.2 Pour in sufficient etchant to cover the specimen
with about 2 cm of solution.
SEMI MF1809-0704 © SEMI 2003, 2004 4
8.3.1.3 Maintain 1 L of solution for each 1,000 cm
2
of
sample surface area to control temperature effects.
8.3.1.4 Etch the specimen according to the removal and
agitation restriction provided in the selection tables.
The time of the etching process may be derived by use
of the suggested etching depth for specific defects.
NOTE 4: Suggested removals may be found in SEMI
MF1725 and SEMI MF1726.
8.3.1.5 If the etching solution must be contained at the
point of use, decant the solution into a container for
(hazardous) waste and rinse the specimen thoroughly
with running water. If the solution is chromium-free
and is not contained for disposal, the solution may be
quenched with water and thoroughly rinsed in the same
beaker.
8.3.1.6 Blow the specimen dry with filtered, organic
free nitrogen.
8.3.1.7 Store the specimen in a clean container until
inspected.
9 Related Documents
9.1 Additional information may be found in the
following references that report details of various
etching solutions:
Sirtl, E., and Adler, A. “Chromic Acid-Hydrofluoric
Acid as Specific Reagents for the Development of
Etching Pits in Silicon,” Z. Metalkunde, 52, 529 (1961).
Secco d’Arragona, F., “Dislocation Etch for (100)
Planes in Silicon,” J. Electrochem. Soc., 110, 948,
(1972).
Schimmel, D.G., “Defect Etch for <100> Silicon
Evaluation,” J. Electrochem. Soc., 126, 479 (1979).
Wright-Jenkins, M., “A New Preferential Etch For
Defects in Silicon Crystals,” J. Electrochem. Soc., 124,
757, (1977).
Yang, K.H., “ An Etch for the Delineation of Defects in
Silicon,” J. Electrochem. Soc., 131, 1140 (1984).
Dash, W.C., “Copper Precipitation on Dislocations in
Silicon,” J. Appl. Phys., 27, 1193 (1956).
Chandler, T.C., “MEMC Etch-A Chromium Trioxide-
free Etchant for Delineating Dislocation and Slip in
Silicon,” J. Electrochem. Soc., 137, 944 (1990).
Sopori, B.L., “A New Defect Etch for Polycrystalline
Silicon,” J. Electrochem. Soc., 131, 667 (1984).
10 Keywords
10.1 defect density; dislocation; grain boundary;
microscopic; polycrystalline imperfection; preferential
etch; silicon; slip
Table 1 Recipes, Figure Index, and Approximate Etch Rates for Chromium Free Etching Solutions
Solution Name See Figures Recipe Approximate Etch Rate
Copper-3
1−2
(with agitation)
HF : HNO
3
: HAc : H
2
O : Cu(NO
3
)
2
·3H
2
O
@
36 : 25 : 18 : 21 : 1 g/100 ml total volume
1 µm/min
Copper-3
3−8
(without agitation)
HF : HNO
3
: HAc : H
2
O : Cu(NO
3
)
2
·3H
2
O
@
36 : 25 : 18 : 21 : 1 g/100 ml total volume
5 µm/min
Modified Dash 9-16
HF : HNO
3
: HAc : H
2
O
@
1 : 3 : 12: 0.17 + AgNO
3
0.005 to 0.05 g/L
1 µm/min
Table 2 Recipes, Figure Index, and Approximate Etch Rates for Chromium Containing Etching Solutions
Solution Name See Figures Recipe Approximate Etch Rate
Secco
17−22
HF : K
2
Cr
2
O
7
(0.15 M)
@
2 : 1
1 µm/min
Wright
23−32
HF : HNO
3
: CrO
3
(5 M) : HAc : H
2
O : Cu(NO
3
)
2
·3H
2
O
@
2 : 1 : 1 : 2 : 2 : 2 g/240 ml total volume
0.6 µm/min