Patent ID: 10274848

Abstract:
An amplitude monitoring system, a focusing and leveling apparatus and a defocus detection method. The method includes: adjusting amplitude of a scanning mirror to a theoretical amplitude value and recording corresponding theoretical output voltage values of a photodetector; adjusting the amplitude of the scanning mirror and sampling real-time amplitude values of the scanning mirror and real-time output voltage values of the photodetector to calculate compensated real-time demodulation results, and recording real-time defocus amounts of a wafer table; subsequent to stepwise displacement of the wafer table, establishing a database based on the compensated real-time demodulation results and the real-time defocus amounts of the wafer table; and in an actual measurement, sampling in real time an actual amplitude value of the scanning mirror and actual output voltage values of the photodetector to calculate a compensated real-time demodulation result and finding an actual defocus amount of the wafer table.