Zero optical path difference self-referencing interferometric alignment system

Abstract

The present invention proposes a self-referencing interference alignment system with zero optical path difference, including: a laser light source module, used to provide the required illumination beam; an optical module, used to irradiate the illumination beam onto the alignment mark to form an optical signal; The electronic acquisition module is used to process the optical signal to obtain the light intensity signal; the software module is used to process the light intensity signal to further obtain the alignment position; it is characterized in that: the optical module includes a first-order optical path The loop makes the positive and negative secondary lights of different polarization states interfere after passing through the same optical path. The invention is improved on the basis of the prior art, and can realize zero optical path difference interference alignment of each color light and each level of sub-light, thereby improving the alignment precision.

Description

technical field [0001] The invention relates to the field of integrated circuit equipment manufacturing, in particular to a zero optical path difference self-referencing interference alignment system for photolithography equipment. Background technique [0002] In the manufacturing process of semiconductor IC integrated circuits, a complete chip usually needs to undergo multiple photolithography exposures before it can be completed. Except for the first photolithography, the photolithography of other levels must be accurately positioned before exposure, so as to ensure the correct relative position between the graphics of each layer. Instant overlay accuracy. Normally, the overlay accuracy is 1 / 3 to 1 / 5 of the resolution index of the lithography machine. For a 100nm lithography machine, the overlay accuracy index is required to be less than 35nm. Overlay accuracy is one of the main technical indicators of a projection lithography machine, and the alignment accuracy between...

AI Technical Summary

Problems solved by technology

However, the technology rotates and interferes with each other after splitting the two wavefronts through different optical paths, and the optical path difference caused by different optical paths between different orders of various colors is realized through the compensator, but for the wide spectrum, the compensation amount of the compensator is limited (1um or so), and the optical path difference caused by actual processing and assembly is much higher than 10um, and the 0th-order light is not filtered out in this technical solution. When the optical path difference between the two wavefronts after splitting is large, the 0-order light will leak. thus reducing the signal contrast

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