A Novel Automatic Probe-to-Pad Alignment Error Correction Approach

In wafer test, the probe mark center shall be close to the pad center as much as possible. But the traditional probe-to-pad alignment (PTPA) process cannot always meet the requirements. So a novel automatic error correction approach was developed in this paper to improve the PTPA process. The approach is based on a classic two dimension rigid motion model and enhanced by integrating an iteratively reweighted least squares algorithm. The singular value decomposition method is also used to seek the solutions. Using the probe mark and pad geometric information, it first best fits the probe mark centers to the targets, then it expands the minimum probe mark to pad edge clearance to the largest. The experiments proved its good feasibility, accuracy and efficiency.