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.
The visible light polariscope has been developed to provide high-resolution, full field, stress visualization and analysis in
transparent materials. The polariscope images are processed using a four-step phase shifting algorithm to provide
qualitative information. The system is calibrated using a disk under compression and then applied to detect the laser
induced damage. The capability of the system to locate laser induced damage induced by different power and scanning
speed are explored and compared to that using conventional transmission imaging. From the thermal stress, the
preliminary information of the laser power and the scanning speed can be obtained.
A Low Birefringence Polariscope (LBP) is developed to provide high-resolution, full-field thickness measurement of the
liquid crystal cell. By rotating the analyzer, phase shift images can be captured and analyzed to obtain the gap thickness
and uniformity of the liquid crystal cells. A comparative study with the commercial system shows good agreement. The
proposed method yields accurate and repeatable full-field measurement of the LC cell with a simple experimental setup.