IEC 63068-2:2019

IEC 63068-2 ®
Edition 1.0 2019-01
INTERNATIONAL
STANDARD
Semiconductor devices – Non-destructive recognition criteria of defects in
silicon carbide homoepitaxial wafer for power devices –
Part 2: Test method for defects using optical inspection
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IEC 63068-2 ®
Edition 1.0 2019-01
INTERNATIONAL
STANDARD
Semiconductor devices – Non-destructive recognition criteria of defects in

silicon carbide homoepitaxial wafer for power devices –

Part 2: Test method for defects using optical inspection

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.080.99 ISBN 978-2-8322-6480-5

– 2 – IEC 63068-2:2019 © IEC 2019
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Optical inspection method . 11
4.1 General . 11
4.2 Principle . 12
4.3 Requirements . 12
4.3.1 Illumination . 12
4.3.2 Wafer positioning and focusing . 13
4.3.3 Image capturing . 13
4.3.4 Image processing . 13
4.3.5 Image analysis . 13
4.3.6 Image evaluation . 13
4.3.7 Documentation . 13
4.4 Parameter settings . 14
4.4.1 General . 14
4.4.2 Parameter setting process . 14
4.5 Procedure . 14
4.6 Evaluation . 14
4.6.1 General . 14
4.6.2 Mean width of planar and volume defects . 14
4.6.3 Evaluation process . 15
4.7 Precision . 15
4.8 Test report . 15
Annex A (informative)  Optical inspection images of defects . 16
A.1 General . 16
A.2 Micropipe . 16
A.3 TSD . 17
A.4 TED . 17
A.5 BPD . 18
A.6 Scratch trace . 18
A.7 Stacking fault . 19
A.8 Propagated stacking fault . 19
A.9 Stacking fault complex . 20
A.10 Polytype inclusion . 21
A.11 Particle inclusion . 23
A.12 Bunched-step segment . 23
Bibliography . 25

Figure A.1 – Micropipe . 16
Figure A.2 – TSD . 17
Figure A.3 – TED . 18
Figure A.4 – Scratch trace . 18
Figure A.5 – Stacking fault . 19

Figure A.6 – Propagated stacking fault . 20
Figure A.7 – Stacking fault complex . 21
Figure A.8 – Polytype inclusion . 22
Figure A.9 – Particle inclusion . 23
Figure A.10 – Bunched-step segment . 24

– 4 – IEC 63068-2:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
NON-DESTRUCTIVE RECOGNITION CRITERIA OF DEFECTS IN SILICON
CARBIDE HOMOEPITAXIAL WAFER FOR POWER DEVICES –

Part 2: Test method for defects using optical inspection

FOREWORD
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International Standard IEC 63068-2 has been prepared by IEC technical committee 47:
Semiconductor devices.
The text of this International Standard is based on the following documents:
CDV Report on voting
47/2475/CDV 47/2522A/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 63068 series, published under the general title Semiconductor
devices – Non-destructive recognition criteria of defects in silicon carbide homoepitaxial wafer
for power devices, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – IEC 63068-2:2019 © IEC 2019
INTRODUCTION
Silicon carbide (SiC) is widely used as a semiconductor material for next-generation power
semiconductor devices. SiC, as compared with silicon (Si), has superior physical properties
such as a higher breakdown electric field, higher thermal conductivity, lower thermal
generation rate, higher saturated electron drift velocity, and lower intrinsic carrier
concentration. These attributes realize SiC-based power semiconductor devices with faster
switching speeds, lower losses, higher blocking voltages, and higher temperature operation
relative to standard Si-based power semiconductor devices.
SiC-based power semiconductor devices are not fully realized due to some issues including
high costs, low yield, and low long-term reliability. In particular, one of the serious issues lies
in the defects existing in SiC homoepitaxial wafers. Although efforts of decreasing defects in
SiC homoepitaxial wafers are actively implemented, there are a number of defects in
commercially available SiC homoepitaxial wafers. Therefore, it is indispensable to establish
an international standard regarding the quality assessment of SiC homoepitaxial wafers.
The IEC 63068 series of standards is planned to comprise Part 1, Part 2, and Part 3, as
detailed below. This document provides definitions and guidance in use of optical inspection
for detecting defects in commercially available silicon carbide (SiC) homoepitaxial wafers.
Part 1: Classification of defects
Part 2: Test method for defects using optical inspection
Part 3: Test method for defects using photoluminescence

SEMICONDUCTOR DEVICES –
NON-DESTRUCTIVE RECOGNITION CRITERIA OF DEFECTS IN SILICON
CARBIDE HOMOEPITAXIAL WAFER FOR POWER DEVICES –

Part 2: Test method for defects using optical inspection

1 Scope
This part of IEC 63068 provides definitions and guidance in use of optical inspection for
detecting as-grown defects in commercially available 4H-SiC (Silicon Carbide) epitaxial
wafers. Additionally, this document exemplifies optical images to enable the detection and
categorization of the defects for SiC homoepitaxial wafers.
This document deals with a non-destructive test method for the defects so that destructive
methods such as preferential etching are out of scope in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
optical inspection
morphological inspection of wafers using optical imaging where an optical image sensor
scans the wafer surface under a non-contact test method for obtaining features of defects, e.g.
size and shape of defects
3.2
optical imaging
technique for capturing, processing and analysing images of defects using light source for
illumination, optical components, optical image sensor and computer systems
3.3
illumination
application of light to defects and their surroundings so that they can be observed

– 8 – IEC 63068-2:2019 © IEC 2019
3.4
reflective illumination
illumination for observing the reflected light from defects by irradiating light onto the wafer
surface
3.5
directional lighting
lighting in which the light to the wafer is incident from a particular direction
3.6
diffused lighting
lighting in which the irradiation direction of the light to the wafer is random
3.7
bright-field observation
method of image capturing in which an optical image sensor detects both lights reflected and
scattered from defects
3.8
dark-field observation
method of image capturing in which an optical image sensor detects only light scattered from
defects
3.9
differential interference contrast observation
method of image capturing in which contrast derives from the difference in optical path
between adjacent points on the wafer surface by irradiating two orthogonal polarized lights
which are spatially displaced
3.10
polarized light observation
method of image capturing in which an optical image sensor detects a polarized light using
polarizing plates in a path from defects by irradiating polarized light
3.11
optical image sensor
device to transform an optical image into digital data
3.12
optical component
lenses, mirrors, filters and other components, which comprise an optical system and are used
to capture optical images
3.13
image capturing
process of creating a two-dimensional original digital image of defects on the wafer surface
3.14
original digital image
digitized image taken by an optical image sensor, without performing any image processing
Note 1 to entry: Original digital images are divided into pixels by a grid, and one grey level is assigned to each
pixel.
3.15
charge-coupled device
CCD
light-sensitive integrated circuit that stores and displays the data for optical images

Note 1 to entry: CCD chips are subdivided into fine elements, each of which corresponds to a pixel of original
digital images.
3.16
pixel
smallest formative element of original digital images, to which a grey level is assigned
3.17
resolution
number of pixels per unit length (or area) of original digital images
Note 1 to entry: If resolutions in the X- and Y- directions are different, both values have to be recorded.
3.18
grey level
shade of grey assigned to each pixel
Note 1 to entry: Shade of grey is usually a positive integer taken from grey scale.
3.19
grey scale
range of grey shades from black to white
st
EXAMPLE: 8-bit grey scale has two-to-the-eighth-power (= 256) grey levels. Grey level 0 (the 1 level)
th
corresponds to black, grey level 255 (the 256 level) to white.
3.20
image processing
software manipulation of original digital images to prepare for subsequent image analysis
Note 1 to entry: For example, image processing can be used to eliminate mistakes generated during image
capturing or to reduce image information to the essential.
3.21
binary image
image in which either 0 (black) or 1 (white) is assigned to each pixel
3.22
brightness
average grey level of a specified part of optical images
3.23
contrast
difference between the grey levels of two specified parts of optical images
3.24
shading correction
software method for correcting non-uniformity of the illumination over the wafer surface
3.25
thresholding
process of creating a binary image out of a grey scale image by setting exactly those pixels
whose value is greater than a given threshold to white and setting the other pixels to black.
Note 1 to entry: To make a binary image, grey level 0 (black) or 1 (white) is assigned to each pixel in the grey-
scale image, depending on whether the pixel indicates a grey level greater than or less than or equal to a given
threshold.
3.25.1
edge detection
method of isolating and locating edges of defects and surface features in a giv
...