Alignment marks for photoetching equipment and alignment method

Abstract

The invention relates to alignment marks for photoetching equipment. The alignment marks are distributed in two different directions. At least two types of gratings with different periods are arranged in each direction. Each type of grating includes a plurality of gratings. The gratings with different periods are arrayed alternately in each direction of the alignment marks. Minus or plus 1 grade diffraction light of the gratings with different periods are imaged by an alignment optical system. The periods of the imaged gratings respectively correspond to different periods of reference gratings. An alignment method comprises the following steps of: capturing a position by utilizing cross imaging image processing or scanning and fitting a peak value of signal strength; carrying out coarse alignment by utilizing information of coherent images of the gratings with longer period and phases of scanning signals of the corresponding reference gratings; and carrying out accurate alignment by utilizing information of the gratings with shorter period and phases of scanning signals of the corresponding reference gratings so as to improve alignment accuracy and reduce alignment position errorscaused by asymmetric deformation of the alignment marks. The alignment marks can be also formed in scribing grooves which are vertical mutually among exposure fields of silicon slices.

Description

technical field [0001] The invention relates to photolithographic equipment in the field of integrated circuit or other micro device manufacturing, and in particular to an alignment mark and an alignment method used in an alignment system of a photolithographic equipment. Background technique [0002] At present, lithography equipment is mainly used in the manufacture of integrated circuits (ICs) or other micro-devices. Through photolithography equipment, multi-layer masks with different mask patterns are sequentially exposed and imaged on a silicon wafer coated with photoresist under precise alignment. The current lithography equipment is mainly divided into two categories, one is stepping lithography equipment, the mask pattern is exposed and imaged on one exposure area of ​​the silicon wafer, and then the silicon wafer moves relative to the mask to move the next exposure area to Underneath the mask pattern and the projection objective, the mask pattern is again exposed o...

AI Technical Summary

Problems solved by technology

However, when using a wedge array, the requirements for the surface shape and wedge angle consistency of the two wedges with the same positive and negative orders of refraction are very high; and the requirements for the manufacturing, assembly and adjustment of the wedge plate group are also very high. It is difficult and expensive to realize the project

[0008] Another prior art situation (Chinese invention patent application: 200710044152.1, title of invention: an alignment system for lithography equipment), the alignment system uses a three-period phase grating with a combination of thickness and thickness, and only uses these three The first-order diffracted light of each period is used as the alignment signal, which can achieve a large capture range and high alignment accuracy. Only the first-order diffracted light of each period can be used to obtain a stronger signal strength and improve the system signal-to-noise ratio. , does not need to use adjustment devices such as wedges to separate multi-channel high-order diffraction components, which simplifies optical path design and debugging difficulty, but the alignment marks in the alignment system are arranged in a line on the silicon wafer and the reference plate, which reduces the light source. Utilization rate, and this arrangement mode will cause the crosstalk problem of the scanning signal when each group of grating images of the alignment mark scans the corresponding reference grating in the alignment scanning. Alignment of Engraving Devices

[0009] At the same time, the above two alignment marks will cause asymmetric deformation of the alignment marks when the silicon wafer is asymmetrically deformed, resulting in a large error in the alignment position

Images