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Background Statement for SEMI Draft Document 5530
NEW STANDARD: SPECIFICATION FOR ORIENTATION FIDUCIAL MARKS FOR PV SILICON WAFERS
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.
Currently, geometric wafer parameters, such as thickness, waviness or side lengths, are measured in an arbitrary orientation. This may create differing measurement results by different parties and may start unnecessary discussions regarding wafer specifications. The new standard will define ways to unambiguously orient the wafer during measurement and processing.
Review and Adjudication Information
Task Force Review / Committee AdjudicationGroup: / PV Si Materials Task Force / PV Materials Committee
Date: / March 2013, PV Fab Manager Forum / March 13, 2013, PV Fab Manager Forum
Time & Timezone: / 9:00 CET / 13:00 CET
Location: / Leonardo Royal Hotel Berlin Alexanderplatz / Leonardo Royal Hotel Berlin Alexanderplatz
City, State/Country: / Berlin, Germany / Berlin, Germany
Leader(s): / Peter Wagner / Hubert Aulich (PV Crystalox)
Peter Wagner
Standards Staff: / Yann Guillou (SEMI Europe)
/ Yann Guillou (SEMI Europe)
Meeting date and time are subject to change, and additional TF review sessions may be scheduled if necessary. Contact the task force leaders or Standards staff for confirmation. Check for the latest schedule.
SEMI Draft Document 5530
NEW STANDARD: SPECIFICATION FOR ORIENTATION FIDUCIAL MARKS FOR PV SILICON WAFERS
1 Purpose
1.1 Dimensional metrics as described in several SEMI test methodsdo not define wafer physical orientation during measurement.
1.2 Measurements of the same wafer differently oriented (rotated or flipped between measurements) result in permuted data sets, within the limits of the measurement equipment precision. This may generate confusion or at least discussions during claim handling or specification verification.
1.3 It may also benefit some solar cell process steps to orient a wafer in a specified or preferred orientation.
1.4 Therefore orientation fiducial marks are required that allow unique orientation of square or pseudo-square silicon (Si) wafers during measurement or processing.
1.5 Many PV Si wafers are currently marked to enable tracing and to tracking. These marks may be used also as orientation fiducial marks.
1.6 This specification defines how current marks may be used as orientation fiducial marks.
1.7 It defines also how to apply an orientation fiducial mark on an otherwise unmarked wafer.
2 Scope
2.1 Thisspecification covers square and pseudo-square Si wafers for photovoltaic (PV) applications, with a nominal edge length ≥ 125 mm and a nominal thickness ≥ 100 µm.
2.2 It may be applied to single crystalline as well as to multicrystalline Si wafers.
2.3 It applies to PV Si wafers that are marked with one of the marks as described in SEMI PV29 and PV32.
2.4 It applies also to wafers with only a fiducial mark according to § 7.2.
NOTICE:SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their use. It is the responsibility of the users of the documents to establish appropriate safety and health practices, and determine the applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 None.
4 Referenced Standards and Documents
4.1 SEMI Standards and Safety Guidelines
SEMI PV29 –– Specification for Front Surface Marking of PV Silicon Wafers with Two-Dimensional Matrix Symbols
SEMI PV32 –– Specification for Marking of PV Silicon Brick Face and PV Wafer Edge
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
(Refer to the SEMI Standards Compilation of Terms (COTs) for a list of the current Abbreviations, Acronyms, Definitions, and Symbols.)
5.1 Abbreviations and Acronyms
5.1.1 BSC — brick slice code
6 Ordering Information
6.1 Checklist — Purchase orders for silicon wafers furnished to this specification shall include the following items:
- For wafers with ID marks
- Type of mark used, SEMI PV29 or PV32.
- Number and relative orientation of marks.
- For wafers without ID mark
- Statement if a single notch according to §7.2 shall be applied or not.
7 Requirements
7.1 Wafers with ID Marks
7.1.1 According to SEMI PV29 or PV32 wafers may have an ID marking for being able to trace them back to their position in the ingot during crystallization and for tracking them through the solar cell manufacturing process.
7.1.2 These ID marks may serve as orientation fiducial marks (see Figure 1):
7.1.2.1 Wafers with front side marks according to SEMI PV29:
7.1.2.1.1 The wafer sides parallel to the finder patterns of the code are defined as a1 and a4 when viewing the wafer from above the surface containing the marks.
7.1.2.1.2 The corner of the wafer where a1 and a4 meet is defined as K1.
7.1.2.2 Wafers with brick slice coding according to SEMI PV32:
7.1.2.2.1 The wafer edge containing the mark is defined as side a1according to Figure 3 and the corner K1 corresponds to the corner closest to the brick ID of this mark.
7.1.2.2.2 If a wafer has two adjacent edges with ID marks then K1 is the corner where the sides with the marks meet and side a1 is defined as that side where the brick ID is closest to the corner.
7.1.2.2.3 Brick slice codes on opposing edges of a wafer are not recommended, according to SEMI PV32.
7.2 Wafers without ID Marks
7.2.1 Such wafers will be marked with a single notch on an edge, which could be applied already on the brick (see Figure 2).
7.2.2 The wafer edge containing the notch is defined as side a1.
7.2.3 The center of the notch is placed at a distance of A1/4 ± notch width from wafer corner K1.
7.2.4 The depth and width of the notch are according to SEMI PV32.
7.2.5 The wafer is viewed from the top when the notch is to the right of K1.
NOTE:The sizes of the front side laser mark and the notches are greatly exaggerated with respect to the wafer size.
Figure 1
Schematic Drawing of the Relations between Wafer Marks (BSC or Front Side Mark) and the Wafer Corners and Sides for a Square Wafer
NOTE:The size of the notch is greatly exaggerated with respect to the wafer size.
Figure 2
Schematic Drawing of the Fiducial Mark on an Otherwise Unmarked Wafer
NOTICE:Semiconductor Equipment and Materials International (SEMI) makes no warranties or representations as to the suitability of the Standards and Safety Guidelines set forth herein for any particular application. The determination of the suitability of the Standard or Safety Guideline 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. Standards and Safety Guidelines are subject to change without notice.
By publication of this Standard or Safety Guideline, SEMI takes no position respecting the validity of any patent rights or copyrights asserted in connection with any items mentioned in this Standard or Safety Guideline. Users of this Standard or Safety Guideline 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 official or adopted Standard or Safety Guideline. 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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