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Proceedings Paper

Curvature measurement system of Si-wafer using circular gratings
Author(s): Chi Seng Ng; Anand Krishna Asundi
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Paper Abstract

Flatness/Curvature measurement is critical in many Si-wafer based technologies ranging from micro-electronics to MEMS and to the current PV industry. As the thickness of the wafer becomes smaller there is an increased tendency for it to warp and this is not conducive to both patterning as well as dicing. Monitoring of curvature/flatness is thus necessary to ensure reliability of device and its uses. However, due to the prevalence of surface flatness measurement systems that flooded the market, the cycle time for curvature measurement system has become one of the critical factors for the user to consider. A simple and rapid whole-field curvature measurement system using a novel a computer aided phase shift reflection grating method has been developed and discussed in the previous publications. Laterals gratings in horizontal has vertical directions are needed in order to realize the curvature information on the wafer in both directions. In this paper, with same system setup, circular grating is being projected on to the specimen to measure the curvature distribution of the wafer. With the aid of coordinate-transform method and the digital phase-shifting technique, the digital images of reflected gratings are processed automatically and analyzed in the polar coordinate system. Unlike vertical or horizontal line gratings, the utilization of the circular gratings in radial shearing method provides curvature information in all directions, not only in one. Further, only four phase shifted images are captured and the measurement cycle time is thus reduced by half.

Paper Details

Date Published: 14 April 2010
PDF: 8 pages
Proc. SPIE 7522, Fourth International Conference on Experimental Mechanics, 75220K (14 April 2010); doi: 10.1117/12.851832
Show Author Affiliations
Chi Seng Ng, Nanyang Technological Univ. (Singapore)
Infineon Technologies (Malaysia) Sdn Bhd (Malaysia)
Anand Krishna Asundi, Nanayang Technological Univ. (Singapore)

Published in SPIE Proceedings Vol. 7522:
Fourth International Conference on Experimental Mechanics
Chenggen Quan; Kemao Qian; Anand Krishna Asundi; Fook Siong Chau, Editor(s)

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