A coarse to fine calibration method for the q-X-Z type wafer pre-alignment device

Abstract

Abstract The wafer pre-alignment device is a crucial component of the equipment front-end modules (EFEM) in the integrated circuit (IC) manufacturing industry. It corrects the wafer position and orientation errors before the wafer is transferred to the subsequent fine alignment wafer stage. To solve the calibration problem of a q-X-Z type wafer pre-alignment device, the study establishes its kinematic model and constructs the relationship between each axis and a laser sensor. Compared to the conventional method of directly selecting 4 points’ wafer edge data to achieve calibration, this paper proposes a method that makes full use of the edge data of a square calibration board. This method solves the device parameters through iteration based on coarse to fine thoughts and obtains a calibration accuracy within 10 microns. The statistical accuracy and operational repeatability of the proposed method are verified through a series of calibration experiments of the wafer pre-alignment device.