Research On Wafer Pre-alignment Technique

Wafer Pre-alignment plays an important role in semiconductor manufacture. Pre-aligner detects wafer eccentricity and wafer notch (or flat) in order to position individual wafer and to improve consistency among wafers in one cassette, which ensures high accuracy in semiconductor manufacturing process. As the wafer size increases, pre-alignment accuracy requirements have been increased. Thus, research of wafer pre-alignment technique becomes necessary.The main research works are as follows:(1) First establish the model of wafer edge curve using piecewise function and then establish wafer edge data acquisition model of each segment. After that, calculate wafer eccentricity and notch direction using different algorithms based on the collected data of wafer edge.(2) Comparing the calculated eccentricity and notch position of the wafer with the preset value based on wafer edge data acquisition model, calculation error is achieved. According to the results under different condition, systematically study the regulation of impact of each parameter on wafer pre-alignment accuracy and achieve important conclusions related to the control, calibration and compensation of the error.(3) According to the error analysis result, transfer the error of pre-aligner into the error of the coordinate relationship between pre-aligner and the robot using error transformation method. With the method, achieve calibration of both errors in one process simultaneously. Then, different calibration methods are designed.(4) Test the accuracy of both mechanical and electrical parts of actual pre-aligner to Compensate for the deficiencies of simulation analysis. Measure the performance of wafer pre-alignment system, and then suggest improvement method according to the weak parts.