METHOD FOR DETECTING FOCUS PLANE BASED ON HARTMANN WAVEFRONT DETECTION PRINCIPLE

摘要

The present disclosure relates to a method for detecting focus plane based on Hartmann wavefront detection principle, the function of which is to detect the position of a silicon wafer in a photolithograph machine in real time so as to accomplish adjustment of the leveling and focus of the silicon wafer. By utilizing microlens array to detect the wavefront carrying information about the position of the silicon wafer based on the Hartmann wavefront detection principle, the spherical wavefront is divided by the respective subunits of the microlens array and is imaged on the respective focus planes of the subunits. If the silicon wafer is located on the focal plane, the incident wavefront for the microlens array is a planar wavefront so that the diffraction light spots are on the focus of the respective subunits of the microlens array; and if the silicon wafer is defocused, the incident wavefront for the microlens array is a spherical wavefront so that the diffraction light spots are shifted on the focus plane of the microlens array. Based on Hartmann wavefront detection principle, the detection of the spherical wavefront may be implemented by the microlens array shifting the imaged light spots for the plane wavefront and the spherical wavefront, so as to accomplish the defocusing measurement for the silicon wafer. The system for detecting focus plane has a simple configuration, a higher accuracy and efficiency, so it is applied to measurement for detecting the focus plane in various types of photolithography machines in a high accuracy and in real time.

主权项

1. A method for detecting focus plane based on Hartmann wavefront detection principle, which is implemented by a system for detecting focus plane constituted of a light source and beam collimating and expanding unit, frontal set of lens, measured silicon wafer, posterior set of lens, microlens array and CCD detector, wherein the front set of lens and the posterior set of lens forms a 4f system, and the measured silicon wafer is on a cofocal plane of the 4f system, the method for detecting focus plane is characterized by that an emerging planar wavefront of the light source and the beam collimating and expanding unit passes through the frontal set of lens, is incident on a surface of the measured silicon wafer and reflected by the measured silicon wafer, passes through the posterior set of lens and the microlens array, and finally imaged in the CCD detector; if the measured silicon wafer is located on the cofocal plane of the frontal set of lens and the posterior set of lens, the microlens array enables imaging of the planar wavefront; and if the measured silicon wafer is defocused, the microlens array enables imaging of the spherical wavefront; and the measurement for detecting the focus plane of the measured silicon wafer is accomplished based on varied situations of the imaged light spot in the CCD detector.