3 October 2008 Residual stress in silicon wafer using IR polariscope
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Proceedings Volume 7155, Ninth International Symposium on Laser Metrology; 715512 (2008); doi: 10.1117/12.814538
Event: Ninth International Symposium on Laser Metrology, 2008, Singapore, Singapore
Abstract
The infrared phase shift polariscope (IR-PSP) is a full-field optical technique for stress analysis in Silicon wafers. Phase shift polariscope is preferred to a conventional polariscope, as it can provide quantitative information of the normal stress difference and the shear stress in the specimen. The method is based on the principles of photoelasticity, in which stresses induces temporary birefringence in materials which can be quantitatively analyzed using a phase shift polariscope. Compared to other stress analysis techniques such as x-ray diffraction or laser scanning, infrared photoelastic stress analysis provides full-field information with high resolution and in near real time. As the semiconductor fabrication is advancing, larger wafers, thinner films and more compact packages are being manufactured. This results in a growing demand of process control. Residual stress exist in silicon during semiconductor fabrication and these stresses may make cell processing difficult or even cause the failure of the silicon. Reducing these stresses would improve manufacturability and reliability. Therefore stress analysis is essential to trace the root cause of the stresses. The polariscope images are processed using MATLAB and four-step phase shifting method to provide quantitative as well as qualitative information regarding the residual stress of the sample. The system is calibrated using four-point bend specimen and then the residual stress distribution in a MEMS sample is shown.
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Zhijia Lu, Pin Wang, Anand Asundi, "Residual stress in silicon wafer using IR polariscope", Proc. SPIE 7155, Ninth International Symposium on Laser Metrology, 715512 (3 October 2008); doi: 10.1117/12.814538; https://doi.org/10.1117/12.814538
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KEYWORDS
Silicon

Semiconducting wafers

Phase shifts

Infrared radiation

Stress analysis

Calibration

Photoelasticity

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