Projection objective detecting method

Abstract

The invention discloses a detecting method of projective object lens of photo-etching machine, which comprises the following steps: (a1) moving working platform to the set position; (a2) sending illuminating order to the light source; separating the light source into measuring wave front and reference wave front to project on the optical detecting element separately through optical path separator; (a3) receiving the gathered image information through optical detecting element; (a4) calculating the image information to obtain true phase information; (a5) reducing the phase information into wave front error information; (a6) judging the position of the wave front to display the character of wave front according to the error information of the wave front. The invention can measure the wave front error, magnification ratio, distortion and field curvature of objective lens precisely, which reduces the size of optical detecting element with simple preparation, high precision and convenient operation.

Description

Technical field [0001] The invention relates to a method for detecting a projection objective lens, in particular to a method for detecting a projection objective lens of a photoetching machine in the manufacturing process of micro-devices such as semiconductor elements and liquid crystal display elements. Background technique [0002] In recent years, in the field of semiconductor lithography, projection lithography technology has continued to advance, and lines have advanced in a finer direction. At present, the key size of the chip has reached the lithography resolution capability of 90nm to 65nm. The imaging quality of the optical projection objective in the lithography system is a key factor affecting the resolution of lithography. Projection objectives can be designed to achieve high quality, but the optical quality of the objective lens will be affected during optical processing, assembly, and transportation. This requires offline optical inspection methods to ensure that ...

AI Technical Summary

Problems solved by technology

However, the main disadvantages of this online detection objective lens method are: 1. It is necessary to introduce an additional light source for measurement; 2. The Hartmann sensor is used to sample the wavefront. Due to manufacturing limitations, the Hartmann space sampling rate cannot be too high, so it cannot Measuring Advanced Aberrations of Projection Objectives

3. CCD manufacturing requirements are strict, since the accuracy of the Hartmann sensor is directly determined by the center position of the spot on the CCD, if there is a size error in the CCD manufacturing itself, this will inevitably lead to a position error of the center point

4. The manufacturing of the array lens is difficult, and the optical error it introduces affects the positioning accuracy of the spots

5. In addition, in order to measure the accuracy, it is necessary to increase the focal length of the array lens, which will also increase the size of the Hartmann sensor and CCD

6. The algorithm for determining the position of the spot is complex, and its model is difficult to determine due to the influence of many factors such as the aberration of the CCD characteristic array lens

In addition, US6573997 describes a method of using gratings to achieve phase-shift point diffraction interference to detect objective lenses. This method can effectively measure objective aberrations close to the diffraction limit, but it needs to use two gratings to achieve light splitting. , the fabrication and assembly of the grating are very difficult, and it is not suitable for integration on the lithography machine. In addition, this method cannot achieve phase shift at the same time, so the light source needs to be precisely controlled

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