semi合集-English.pdf - 第7539页

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 c ontrol temperature effects. 8.3.1.4 Etch the specimen according to the removal and agitation restricti…

100%1 / 7923
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
SEMI MF1809-0704 © SEMI 2003, 2004 5
Table 3 Classification of Application and Issue Suitability for Chromium Free Etching Solutions
Application Issue
Solution Name
100 Orientation
111 Orientation
p-Type
P+ Type
n- Type
n+ Type
OISF
Shallow Pits
Hillocks
Dislocations
Epi Stacking
Faults
Bubble Formation
Agitation Required
Temperature
Flow Patterns
Copper-3 with Agitation A A A D A D A A C A A Yes Yes ~ 25° C No
Copper-3 without Agitation A A A D A D A A C A A Yes No ~ 25° C No
Modified Dash A A A C A D A A - A A Yes Yes ~ 25° C No
NOTE1: Classifications in Tables 3 and 4 are as follows: A = Excellent, B= Good, C= Acceptable, D = Unacceptable.
Table 4 Classification of Application and Issue Suitability for Chromium Containing Etching Solutions
Application Issue
Solution Name
100 Orientation
111 Orientation
p-Type
P+ Type
n- Type
n+ Type
OISF
Shallow Pits
Hillocks
Dislocations
Epi Stacking
Faults
Bubble Formation
Agitation Required
Temperature
Flow Patterns
Secco (NOTE 2) A B A D A C A B C A A Yes Yes < 30° C No
Wright A A A B A C A B B A A Yes Yes < 30° C No
NOTE 1: Classifications in Tables 3 and 4 are as follows: A = Excellent, B= Good, C= Acceptable, D = Unacceptable.
NOTE 2: Flow pattern defects form a characteristic “ v” shaped pattern when the wafer is etched in a vertical position without acid agitation (see
Figure 19). Other applications of Secco etch require some form of agitation to avoid confusing artifacts associated with bubble formation.
type, 10 Ω·cm, (100) Wafer; 1100° C Steam, 80 minute
Oxidation; Copper-3 Etch with Agitation; 2 µm removal
Figure 1
Oxidation Stacking Fault, 500
×
p type, 10 Ω·cm, (111) Wafer; 1100° C Steam, 80 minute
Oxidation; Copper-3 Etch with Agitation; 2 µm removal
Figure 2
Shallow Pits (Haze), 500
×