数字光栅调焦调平传感器的工艺适应性OA北大核心CSTPCD

In the digital grating displacement measurement technique,the CMOS pixel array of the camera is regarded as a'digitized'grating.The micron-scale grating images can realize nanoscale displacement meas-urements by constructing the period difference between optical grating and digital grating.Combined with the detection light path of oblique incidence,it can be applied to the lithography machine's focusing and lev-eling sensor to measure the wafer surface height accurately.In the actual measurement,the unexpected pat-terns on the wafer surface interfere with the reflection imaging of the optical grating,then affect the image processing results.In this paper,a process adaptability method for digital grating displacement measurement is proposed,which reconstructs the light intensity and recovers the light intensity curve from the CMOS im-age when interference patterns exist.The proposed method shows good stability when the large area pattern appears on the wafer substrate,and can adapt to multiple surface defects such as scratches,particles,stains and grooves.The experimental results show that the mean square error of the light intensity curve is signific-antly reduced and the method's Z-direction error correction is within±33 nm(±3σ=±41.2 nm)after recon-structing the light intensity.This method can enhance the process adaptability of the digital grating focusing and leveling sensor.Therefore,it can serve as a technical reference for the focusing and leveling method.