By Kevin Nguyen, SEMI
450mm notchless wafer standardization has been under discussion for over a year. Driven by the G450C Consortium, the proposed changes will improve wafer symmetry, but more importantly, increase the utilization of wafer surface area. The International Polished Wafer and International 450mm Wafer Task Forces (TF) led the effort to add a 450mm notchless wafer specification via ballot 5604. The document was completed late last year and is now published in the latest edition of SEMI M1-0215 Specification for Polished Single Crystal Silicon Wafers.
SEMI T7-0709 – Specification for Back Surface Marking of Double-Side Polished Wafers with a Two-Dimensional Matrix Code Symbol, is an important specification, which provides marking symbology with no intrusion in the fixed quality area of the wafer. This standard is applicable for various size of wafers, and not limited to 450mm notchless wafers. In alignment with SEMI M1, the Fiducial Mark Interoperability TF, in cooperation with the International 450mm Wafer TF, balloted and successfully received committee approval for doc. 5752, Revision of SEMI T7 to cover 450mm wafers. (See figure below for the primary location of the SEMI T7 mark on the polished wafer.) The document was approved at the Traceability Committee meeting during SEMICON Japan in December 2014. The new version of SEMI T7 is currently being processed for publication and will be available in Spring 2015. When the revision of the T7 is published, SEMI will have a total of 20 SEMI standards for 450mm manufacturing.
450mm Diameter Wafer with Location of Orientation Fiducial Marks (Source: SEMI M1 -Figure 6)
The International 450mm Wafer TF is also pursuing doc. 5794, Specification of Developmental 450 mm Diameter Polished Single Crystal Notchless Silicon Wafers With Back Surface Fiducial Marks. This standard is required for the development and test of wafer alignment systems for notchless wafers with back side fiducial laser scribed marks. The project is anticipated to be completed by SEMICON West, July 2015.
The International Advanced Wafer Geometry TF completed the revision of SEMI M49-1014, Guide for Specifying Geometry Measurement Systems for Silicon Wafers for the 130nm to 16nm Technology Generations, by reducing edge exclusion on 450mm wafer from 2mm to 1.5mm for 16 nm technology generation for measurement system.
Meanwhile doc. 5655 still needs to be completed for increasing the Fixed Quality Area (FQA) from 223mm to 223.5mm for 450mm polished wafers in SEMI M1-0215 Specification for Polished Single Crystal Silicon Wafers. These changes are significant since there may be issues in verifying the quality of wafers close to the wafer edge due to limitations of measurement equipment. No timetable is set, but doc. 5655 may be issued in cycle 4-2015 ballot for review at SEMICON West after discussion at the NA Standards 2015 Spring meetings.
In addition, other physical interfaces and carriers standardization efforts are underway including doc. 5069B, Specification for 450mm Wafer Shipping System. SEMI has a 300mm wafer shipping system standard (M45), but a 450mm wafer version is not yet available. The International 450mm Shipping Box Task Force is currently drafting doc. 5069B for the third time after it failed at the previous meeting in 2014. More progress will be reported at the next NA Physical Interfaces and Carriers TC Chapter meeting.
For complete listing of revisions and new standards efforts, visit (http://www.semi.org/node/42416)
While the timing of a transition to 450mm wafers remains unclear, the industry is continuing to develop the standards that will be essential to high-volume manufacturing on larger substrates. The first standard proposal was submitted in 2007, and SEMI has since published nineteen 450mm-related Standards. New standards are being developed as the industry identifies new requirements, and revisions to published standards are being made as areas for improvement are recognized.
If your company is not yet involved in these efforts to shape the future, learn more about SEMI Standards by visiting www.semi.org/en/Standards. Note that participation in the SEMI Standards Program is free, but requires registration. To learn more, contact your local SEMI Standards staff or register at: www.semi.org/standardsmembership.
For additional 450 information (PPTs, viewpoints, Standards revisions, etc.), visit 450 Central at www.semi.org/450.