Interferometry of double-sided polished wafer and error analysis
doi: 10.37188/CO.2022-0226
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摘要:
为了实现双面抛光晶圆总厚度变化(TTV)和变形程度中弯曲度(Bow)和翘曲度(Warp)的测量,提出了一种干涉测量方法。采用两个带有标准镜的菲索式相移干涉仪对晶圆正反面同时进行测量,将测量所得晶圆正反面形貌与未放置晶圆时两个干涉仪的空腔形貌进行组合运算,可得到不受标准镜误差影响的双面抛光晶圆的表面相关参数。在组合运算中,由于两个标准镜未精确对准会产生映射误差,影响相关参数的测量结果。针对这一问题,在晶圆测量之前,将三点定位装置固定在两个标准镜之间,基于三点定圆定理不断调整两个标准镜的位置,可使映射误差极小,进而减小映射误差对测量结果的影响。实验结果表明,50 mm晶圆横向和纵向的映射误差分别为21.592 μm和37.480 μm,TTV、弯曲度和翘曲度分别为0.198 μm、−0.326 μm和1.423 μm。为了进一步验证调整方法的有效性,采用单个干涉仪对晶圆进行翻转测量,由测量结果可知晶圆的TTV、弯曲度和翘曲度分别为0.208 μm、−0.326 μm和1.415 μm。所提干涉法在调整好两个标准镜的位置后,可以方便快速的用于大批量大尺寸晶圆的测量,提高了晶圆的检测效率,同时具有较高的测量精度。
Abstract:An interferometric measurement method is proposed to measure the Total Thickness Variation (TTV) and the Bow and Warp in the deformation of a double-sided polished wafer. Two phase-shifting Fizeau interferometers with reference mirrors are used to measure the topography of the front and back surfaces of the wafer simultaneously, and the measured topography of the front and back surfaces of the wafer are combined with the cavity topography of the two interferometers when the wafer is not placed to obtain the surface parameters of the double-sided polished wafer which are not affected by the reference mirror error. In the combined operation, the mapping error is introduced because the two reference mirrors are not precisely aligned, which affects the measurement results of the relevant parameters. To this end, before wafer measurement, the three-point positioning device is fixed between the two reference mirrors, and the position of the two reference mirrors is continuously adjusted based on the three-point circular theorem, which can make the mapping error extremely small, thereby reducing the influence of the mapping error on the measurement results. The experimental results show that the mapping errors of 50 mm wafer transverse and longitudinal directions are 21.592 μm and 37.480 μm, respectively, and the TTV, Bow and Warp are 0.198 μm, −0.326 μm and 1.423 μm, respectively. In order to further verify the effectiveness of the adjustment method, a single interferometer was used to flip the wafer for measurement, and the TTV, Bow and Warp of wafer are 0.208 μm, −0.326 μm and 1.415 μm, respectively. The proposed interferometric method can be easily and quickly used for the measurement of large quantities of large-sized wafers after adjusting the position of two reference mirrors, which improves wafer inspection efficiency. At the same time, it has a superior measurement accuracy.
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Key words:
- interferometry /
- double-sided polished wafer /
- error analysis /
- TTV /
- bow /
- warp
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