Curvature measurement system of Si-wafer using circular gratings

Chi Seng Ng; Anand Krishna Asundi

doi:10.1117/12.851832

14 April 2010 Curvature measurement system of Si-wafer using circular gratings

Chi Seng Ng, Anand Krishna Asundi

Proceedings Volume 7522, Fourth International Conference on Experimental Mechanics; 75220K (2010) https://doi.org/10.1117/12.851832
Event: Fourth International Conference on Experimental Mechanics, 2009, Singapore, Singapore

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.

Citation Download Citation

Chi Seng Ng and Anand Krishna Asundi "Curvature measurement system of Si-wafer using circular gratings", Proc. SPIE 7522, Fourth International Conference on Experimental Mechanics, 75220K (14 April 2010); https://doi.org/10.1117/12.851832

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