An alignment system and alignment method for automatic focusing

Abstract

The invention provides an aligning system for an automatic focusing and an aligning method. The aligning system comprises a light source, a wavelength selection unit, an illumination mirror set, an illumination adjusting unit, a beam splitting unit, an imaging objective lens set, a splitting unit, a reference mark face and a reference mark, a silicon wafer and an aligning mark, and a motion bench in sequence. The splitting unit is connected to the imaging regulating unit, an imaging mirror set, and a detector in sequence, and the detector, the imaging regulating unit, the illumination adjusting unit, and the motion bench are connected to a signal processing and controlling unit. A beam of illumination light illuminates the reference mark and the aligning mark at the same time. The system searches and marks an optimal focal plane of the reference mark, and calculates the interference envelope extremum formed by the interferometric fringe of light reflected by the reference mark and the aligning mark in an area of the reference mark, and the deviation value of the aligning mark and the optimal focal plane can be determined. The aligning mark is moved to the optimal focal plane to complete focusing. The system can automatically, accurately, and fast focus, and reduce the effect that the precision is affected by the environment.

Description

technical field [0001] The invention relates to the field of semiconductor photolithography, in particular to an automatic focusing alignment system and alignment method. 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. When the feature size CD is required to be smaller, the requirements for overlay accuracy and the resulting alignment accuracy become more stringent. For example, a 90nm CD size requires an...

AI Technical Summary

Problems solved by technology

[0005] This technology solves the problems of complex structure, high installation and adjustment difficulty and difficult implementation when using a self-referencing interferometer to determine the position of the alignment mark

However, before the detector unit obtains the horizontal relative position relationship between the alignment mark and the reference mark, it must first obtain a clear image of the alignment mark. Due to environmental interference and increasingly small chip size, the alignment mark on the silicon wafer is very difficult It is difficult to image clearly, so it is necessary to invent an optical path alignment system that can solve the problem that the alignment system is easily disturbed by the environment and it is difficult to search for the best focal plane for small-sized alignment marks on silicon wafers

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