Abstract: In the photo process, the product wafers' overlay accuracy mostly depends on the global alignment and final alignment result. Therefore, the key parameter of product wafer will be calculated via the laser onto the grating mark resulted in moire signal. The key parameter includes x, y coordinate, wafer rotation data, wafer orthogonal data, step scaling data. The alignment failed issues always suffer from the various films and thickness by laser alignment. Such as figure 1 is the power IC device for failed laser alignment. Figure 2 is the compared laser alignment issue about the WGA and LSA multiple grating mark, figure 3 is the compared laser alignment issue about the moire signal. In this paper, we provide several methods to improve the laser alignment issue. Specially, according to experimental results, we find out the improved direction for the laser alignment. The improved direction is that changed grating mark width, using the convex grating mark, using the higher viscosity photo resist and using the dry etching grating mark in etching process. !2
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