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Optical Engineering

Simultaneous analysis of edge quality parameters for submillimeter-thick silicon wafer bar with Fourier optics
Author(s): Sarun Sumriddetchkajorn; Kosom Chaitavon
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Paper Abstract

This paper proposes an edge quality assessment system for a submillimeter thick wafer bar suitable for semiconductor and hard disk drive industries. Our key approach is based on Fourier optics analysis in a retro-reflective optical architecture featuring nondestructive and noncontact measurement. In our proposed design, a collimated optical beam is incident on a submillimeter thick wafer bar from its side. In this way, part of the optical beam is reflected back and is then Fourier transformed on a two-dimensional image sensor. By investigating the far-field diffraction pattern, important parameters of the wafer bar such as thickness, surface parallelism, edge parallelism, and surface defect can simultaneously be analyzed. To our knowledge, this is the first time that these important parameters are analyzed by only one system. Other key features include low cost and vibration insensitivity. Our field test study using a 635-nm wavelength laser and a 15-cm plano-convex lens for specified 246-μm thick rectangular wafer bars shows that our retro-reflective approach can measure the bar thickness within its specified ±10 μm. It can also simultaneously evaluate the remaining desired parameters and can distinguish nicely edged bars from poorly edged bars. Other key features include low cost, ease of implementation, robustness, and low component counts.

Paper Details

Date Published: 1 February 2011
PDF: 7 pages
Opt. Eng. 50(2) 023605 doi: 10.1117/1.3544589
Published in: Optical Engineering Volume 50, Issue 2
Show Author Affiliations
Sarun Sumriddetchkajorn, National Electronics and Computer Technology Ctr. (Thailand)
Kosom Chaitavon, National Electronics and Computer Technology Ctr. (Thailand)

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