Background Statement for SEMI Draft Document 4806
New Standard: GUIDE TO DEFECTS FOUND ON MONOCRYSTALLINE
SILICON CARBIDE SUBSTRATES
NOTICE: This background statement is not part of the balloted item. It is provided solely to assist the recipient in
reaching an informed decision based on the rationale of the activity that preceded the creation of this document.
NOTICE: Recipients of this document are invited to submit, with their comments, notification of any relevant
patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this
context, “patented technology” is defined as technology for which a patent has issued or has been applied for. In the
latter case, only publicly available information on the contents of the patent application is to be provided.
This document is intended to give users of silicon carbide substrate material a guideline for the nomenclature of
defects commonly found on this kind of material. Many defects are specific to SiC and experience and naming
conventions of traditional Si material (e.g. in SEMI M1 and related documents) is not always appropriate.
It is separated into three sections: bulk defects, surface defects and features observed after etching in molten KOH
salt.
Test methods are not listed, as SEMI M55 and its sub-standards list the appropriate test methods and redundancy
should be avoided. For several defects as micropipes no standard test methods are currently existing.
Review and Adjudication Information
Group:
Date:
Time & Timezone:
Location:
City, State/Country:
Leader(s):
Standards Staff:
Task Force Review
SiC TF – Defect Catalog Group
TBD
TBD
TBD
TBD
Arnd Weber (SiCrystal)
Committee Adjudication
EU CS Materials Committee
March 21, 2011 (tentative)
TBD
TBD
Frankfurt, Germany
Arnd Weber (SiCrystal)
Roland Bindemann (FCM)
Ian McLeod (SEMI NA)
imcleod@semi.org
OR
James Amano (SEMI HQ)
jamano@semi.org
Ian McLeod (SEMI NA)
imcleod@semi.org
OR
James Amano (SEMI HQ)
jamano@semi.org
This meeting’s details are subject to change, and additional review sessions may be scheduled if necessary. Contact
the task force leaders or Standards staff for confirmation.
Telephone and web information will be distributed to interested parties as the meeting date approaches. If you will
not be able to attend these meetings in person but would like to participate by telephone/web, please contact
Standards staff.
i
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SEMI Draft Document 4806
New Standard: GUIDE TO DEFECTS FOUND ON MONOCRYSTALLINE
SILICON CARBIDE SUBSTRATES
1 Purpose
1.1 The purpose of this guide is to list, illustrate and provide reference for various characteristic features and defects
that are seen on silicon carbide wafers. Recommended practices for observation are referenced as far as available
standards. The artifacts described in this guide are intended to support the development of test methods and to
support the content of SEMI M55.
2 Scope
2.1 Observed defects on monocrystalline SiC substrates, which are of potential relevance for industrial application
are identified and described on the basis of examples, mainly by photos, pictures and other relevant data for these
defects.
2.2 The defect terminology is reviewed and adapted where necessary.
2.3 This document does not cover epitaxial layers grown on SiC substrates.
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish appropriate safety and health practices and determine the
applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 Defects, structures, features or artifacts revealed or enhanced by the referenced methods and exhibited in this
guide must be carefully interpreted. Unless utmost care is exercised, the identification of the structure may be
ambiguous.
4 Referenced Standards and Documents
4.1 SEMI Standards
SEMI M55 — Specification for Polished Monocrystalline Silicon Carbide Wafers
4.2 ASTM Standards
ASTM F1404-92(2007) — Test Method for Crystallographic Perfection of Gallium Arsenide by Molten Potassium
Hydroxide (KOH) Etch Technique
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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5 Terminology
List of defects
Table 1 List of defects
Defect / Keyword
Remark
Figure
micropipe
planar defect
crystallite, crystallite defect
polytypes, polytype defect
crossed polarizers
edge chip
indent
pit
scratch, microscopic scratch
crack
large hexagonal etch pit
basal plane dislocation (BPD)
threading dislocation (TSD, TED)
screw dislocation (SD)
edge dislocation (ED)
bulk defect, no special preparation
bulk defect, no special preparation
bulk defect, no special preparation
bulk defect, no special preparation
method
surface feature
surface feature
surface feature
surface feature
surface feature
KOH etched surface, see also ASTM F1404
KOH etched surface, see also ASTM F1404
KOH etched surface, see also ASTM F1404
KOH etched surface, see also ASTM F1404
KOH etched surface, see also ASTM F1404
1, 3, 6
2, 3
6
4, 5
5, 6
7
7
8
9
10
11, 12
13, 15
14, 15
11, 14
14
6 Bulk features (no special preparation)
Figure 1
Micropipes, optical microscope, transmission mode, focus in bulk.
Material: 4H, 4deg off, Si-face.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
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Document Number: 4806
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0.5 mm
Figure 2
Planar Defect (void or negative crystal in bulk), optical microscope, transmission mode, focus in bulk.
Material: 4H, 4 deg off, Si face.
Figure 3
Planar Defect with micropipe attached on top left (optical microscope, transmission mode, different depth of
focus in the material).
Material: 4H, 4deg off, Si-face, n-type.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
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20 mm
Figure 4
Polytypes (foreign polytypes, polytype defect): deviating yellowish colour due to 15R or 21R or similar
modification on n-type material. The affected area may be much smaller in the order of 0.1 mm2.
Material: 6H, n-type
Figure 5
Left: crossed polarizer image showing weak structural imperfections visible due to contrast patterns.
(example area marked by red circle). Also present is a polytype defect on the left wafer side with deviating
color. (arrow, compare also Fig. 4)
Right: same wafer in transmission mode, only polytpe defect is visible.
Material: 4H, n-type.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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Figure 6
Crossed Polarizer Image showing crystallite defect (red circle). The darker region results from facetted
growth and exhibits higher doping concentrations. Also visible are micropipes due to cross-like contrast
patterns in the upper half of the wafer.
Material: 4H wafer, 50.8mm, 8 deg off, n-type.
7 Surface Features (no special preparation required, wafer as received)
0.5 mm
Figure 7
Edge chip and indent
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
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Figure 8
Pits (optical microscope, DIC-mode).
Material: 4H.
0.5 mm
Figure 9
Microscopic Scratch.
Material: 4H, Si-face.
0.5 mm
Figure 10
Crack
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
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8 Features revealed by molten KOH etching
8.1 Preparation — The material is exposed to molten KOH at approx 540°C for several minutes thereby revealing
characteristic etch pits on the polished
Si-face. As a guideline ASTM F1404 should be used.
Special attention has to be paid to possible artifacts in the etch pattern due to preparation conditions, as e.g. those
caused by scratches.
8.2 Interpretation of etch pits — in general depends on polytype, conductivity type and doping level
100 um
Figure 11
Large hexagonal etch pit (etched micropipe, super-screw dislocation, large defect), the appearance depends
on the etching and inspection conditions.
Material: 4H, 4 deg off, Si-face, n-type.
3
2
4
1
Figure 12
Large hexagonal etch pits in various configurations: (1) with white center, (2) with black center, (3) multiple
overlaying non-hexagonal pits, (4) multiple overlaying hexagonal pits. Many threading dislocations and basalplane dislocations (small etch pits) are also present (see also figure 14 and 15 below).
Material: 4H, 4 deg off, Si-face, n-type.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document development) activity. All other
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100 um
Figure 13
Basal plane dislocation.
Material: 4H, 4 deg off, Si face, n-type.
100 um
Figure 14
Threading dislocations (edge or screw depending on doping level).
Material: 4H, 4 deg off, Si face, n-type.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
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Figure 15
Threading dislocations (appearing dark, marked with arrow) and basal plane dislocations (appearing bright,
marked with circles).
Material: 4H, nominally on-axis, Si-face, semi-insulating.
NOTICE: SEMI makes no warranties or representations as to the suitability of the standard(s) set forth herein for
any particular application. The determination of the suitability of the standard(s) is solely the responsibility of the
user. Users are cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other
relevant literature respecting any materials or equipment mentioned herein. These standards are subject to change
without notice.
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respecting the validity of any patent rights or copyrights asserted in connection with any item mentioned in this
standard. Users of this standard are expressly advised that determination of any such patent rights or copyrights, and
the risk of infringement of such rights are entirely their own responsibility.
This is a draft document of the SEMI International Standards program. No material on this page is to be construed as an offi cial or adopted standard. Permission is granted to
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