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SEMI T1-95 © SEMI 1993, 2003 1 SEMI T1-95 (Reapproved 0303) SPECIFICATION FOR BACK SURF ACE BAR CODE MARKI NG OF SILICON WAFERS This specificati on was technically approved by the Global Trac eability Committee and is th…
SEMI INTERNATIONAL STANDARDS
TRACEABILITY
Semiconductor Equipment and Materials International
SEMI T1-95 © SEMI 1993, 2003 1
SEMI T1-95 (Reapproved 0303)
SPECIFICATION FOR BACK SURFACE BAR CODE MARKING OF
SILICON WAFERS
This specification was technically approved by the Global Traceability Committee and is the direct
responsibility of the North American Traceability Committee. Current edition approved by the North
American Regional Standards Committee on October 25, 2002. Initially available at www.semi.org
December 2002; to be published March 2003. Originally published in 1993; previously published in 1995.
NOTICE: The user’s attention is called to the
possibility that compliance with this specification may
require use of an invention covered by patent rights.
By publication of this specification, SEMI takes no
position respecting the validity of any patent rights
asserted in connection with any item mentioned in this
specification. Users of this specification are expressly
advised that determination of any such patent rights,
and the risk of the infringement of such rights, are
entirely their own responsibility.
1 Scope
1.1 This specification defines the content and location
of a back surface bar code marking for silicon wafers.
The code is variable in length from 7 to 18 characters
which are user-definable. A character position is held
constant for the checksum character, but all else is
variable. No other information is encrypted into the
code. This allows the performance requirements of
related bar code reading equipment to be simplified. In
addition, provision is made for an optional
alphanumeric marking of the size specified in SEMI
M12 to enable operator identification of wafers. This
alphanumeric code is not intended to be machine
readable.
NOTE 1: The example as described in Table 1 and Figure 1
pertains to a hard mark applied by the silicon wafer
manufacturer.
1.2 This specification applies to flatted or notched
silicon wafers of nominal diameter 125 mm and larger,
as specified in SEMI M1.
1.3 The bar code can be read bi-directionally without
impairing its decodability.
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.
2 Referenced Standards
2.1 SEMI Standards
SEMI M1 — Specifications for Polished
Monocrystalline Silicon Wafers
SEMI M12 — Specification for Serial Alphanumeric
Marking of the Front Surface of Wafers
NOTICE: Unless otherwise indicated, all documents
cited shall be the latest published versions.
3 Terminology
3.1 Definitions
3.1.1 background — of a bar code symbol — the
uniform lighter or more reflective region, including
quiet zones, that provides contrast for the darker bars.
3.1.2 bar — in a bar code symbol — the darker or less
reflective element of the symbol.
3.1.3 bar code density — the number of characters,
exclusive of quiet zones, that can be represented in a
linear unit of measure.
NOTE 2: Bar code density can be expressed in characters per
inch (cpi) or characters per millimeter (cpmm).
3.1.4 bar code symbol — an array of rectangular bars
and spaces that are arranged in a predetermined pattern
following specific rules to represent elements of data
that are referred to as characters.
NOTE 3: The symbol is comprised of message characters and
start/stop characters, check characters, and quiet zones as
required by a particular symbology to form a complete
scannable entity.
3.1.5 bar code character — a single group of bars and
spaces which represent an individual number, letter,
punctuation mark, or other symbol.
3.1.6 bar height — of a bar code symbol — the bar
dimension perpendicular to the bar width.
3.1.7 bar width — of a bar code symbol — the
perpendicular distance across a bar between the points
on opposite edges that have a reflectance that is
midway between the background and bar reflectance.
SEMI T1-95 © SEMI 1993, 2003 2
3.1.8 bi-directional bar code symbol — a bar code
symbol capable of being read successfully, either by
scanning from right to left or from left to right.
3.1.9 character — of a bar code — a single group of
bars and spaces that together represent an individual
numeral, letter, punctuation mark, or other symbol.
3.1.10 character set — the complete range of
characters available for encoding within a particular bar
code symbology.
3.1.11 check character — of a bar code symbol — a
character included within the symbol whose value is
used for the purpose of mathematical verification of the
accuracy of the read.
3.1.12 continuous code — a bar code symbol in which
all spaces within the symbol are parts of characters so
that there are no inter-character gaps.
3.1.13 element — of a bar code symbol — a single bar
or space.
3.1.14 module — of a bar code symbol — narrowest
element, bar, or space.
3.1.15 nominal width — of a bar code element — the
average width of each size element.
3.1.16 quiet zone — of a bar code symbol — a clear
background area that precedes the start character and
follows the stop character of the symbol.
3.1.17 self-checking bar code symbol — a bar code
symbol that uses a checking algorithm that can be
applied against each character such that substitution
errors can only occur if two or more “printing” defects
appear within a single character.
3.1.18 self-clocking bar code symbol — a bar code
symbol in which the number of modules, bars, and
spaces is the same in each character.
3.1.19 space — in a bar code symbol — the more
reflective element of the symbol, usually formed by the
background between bars.
3.1.20 start/stop character — in a bar code symbol —
special characters that provide initial timing references
and direction-of-read information to the decoding logic.
3.1.21 start/stop character pattern — a special bar
code character that provides the scanner with start and
stop reading instructions as well as scanning direction.
The start character is at the left end of a BC-412 symbol
(position #2). The stop character is at the right end of
the symbol (position #11).
3.1.22 symbol — a combination of characters, inclu-
ding start/stop characters, quiet zones, data characters,
and check characters, required by a particular
symbology, which form a complete scannable entity.
4 Method of Marking
4.1 The dot matrix laser method shall be used to write
characters. The minimum bar matrix shall be 1 dot
horizontal and 11 dots/mm vertical as shown in Table 1
and Figure 1. The minimum matrix for alphanumeric
characters shall be as specified in SEMI M12. In either
case, more dots may be used, up to and including a
solid line.
5 BC-412 Code
1
5.1 Characteristics — BC-412 is a presence-absence
bar code symbology which uses an alphanumeric
character set as outlined in Table 2. The name BC-412
is derived from the method used to encode data
characters. Each data character is comprised of four
single-width bars incremented within 12 modules. The
code is a continuous code.
5.2 Character Set — The character set available for
marking wafers consists of the ten digits (0−9) and all
capital letters in the English alphabet except O as listed
in Table 3. In addition, there is a start character and a
stop character.
5.2.1 Character Construction and Value — The
module sequence and value for use in calculating the
check character are listed for each character in Table 3.
5.3 Symbol Content — All character count and content
in the wafer marking symbol are user-definable and
vary in number from 7 to 18. The checksum character
position is fixed.
6 Optional Alphanumeric Code
6.1 The optional alphanumeric symbol is variable and
user definable, and similar to existing SEMI standards
M12 and M13 with respect to font style.
6.2 The characters may be oriented with the bottom or
top of each character toward the primary fiducial user
definable.
6.3 The characters in the optional alphanumeric
symbol are those in position #3 through position #
(n + 2) of the BC-412 symbol (see Table 4).
7 Code Field Locations
7.1 The code field locations for flatted and notched
wafers are specified in Figures 3 and 4, respectively.
Values of the dimensions for both cases are given in
Table 5.
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Director of Commercial Relations