Development of a wafer warpage measurement technique using Moire-based method

作者：Hsieh Hung Lin^*; Huang Yung Guang; Tsai Yu Hsuan; Huang Yao Hui

来源：Applied Optics, 2016, 55(16): 4370-4377.

DOI：10.1364/AO.55.004370

This paper reports on a novel technique for measuring wafer warpage, using the design concepts of moire shift, digital moire, autocollimator, and the scanning profiling method. The measurement system is divided into two parts: an optical moire system and a phase analysis system. The optical arrangement can be adjusted to control the projection of a linear grating image onto the surface of a wafer to be reflected back into a CCD camera. The grating image acquired by the CCD camera is used for measurement whereas a reference grating image is obtained using the digital moire method. By overlapping the two images of the measurement and the reference gratings, the corresponding moire fringes are formed. The phase of the moire fringes will change proportionally to the degree of warpage in the wafer, which can be measured by detecting variations in the phase shift of the moire fringes in the scanning profile across the surface of the entire wafer. Measurement resolution can be controlled by adjusting the pitch size of the grating or the focal length of the focusing lens, or by adjusting the angle between the images of the measurement and reference gratings. Experiment results demonstrate that the proposed method is able to achieve an angular resolution of 0.2 mu rad. As compared to the current warpage measurement techniques, the proposed method has the ability of high measurement resolution, high stability, and high flexibility.

• 出版日期2016-6-1