Interferometer

Abstract

The invention discloses an interferometer to detect the projective object lens of photo-etching machine, which comprises the following parts: first polarizing spectroscope, two collimation lens groups to lead reference light and measuring light at one side of incidence face of first polarizing spectroscope separately, second and third polarizing spectroscopes at the incidence face of the first polarizing spectroscope, wherein one half retardation sheet and one quarter retardation sheet are allocated between the first and third polarizing spectroscopes; one quarter retardation sheet is set between the first and second polarizing spectroscopes. 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 an interferometer, in particular to an interferometer for detecting the wave aberration of a projection object lens of a photolithography 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, the projection lithography technology has been continuously improved, and the lines have been advanced in a finer direction. At present, the critical size of the chip has reached the lithography resolution capability of 90nm to 65nm. The imaging quality of the optical projection objective lens in the lithography system is a key factor affecting the resolution of lithography. The projection objective lens can achieve very high quality when it is designed, but the optical quality of the objective lens will be affected in the process of optical processing, assembly and transportation, wh...

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 use of the Hartmann sensor is to sample the wavefront. Due to manufacturing limitations, the Hartmann space sampling rate cannot be too high, so it cannot be measured 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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