Preparation method and structure of overlay alignment mark

Abstract

The invention provides a preparation method and a structure of an overlay alignment mark. The overlay alignment mark comprises a metal mark and a current layer mark, wherein the metal mark serves as afront layer mark, the metal mark penetrates through the thin film structure, the bottom of the metal mark is located in the substrate, the substrate comprises a substrate first surface and a substrate second surface arranged correspondingly, and the thin film structure is located on the substrate first surface; the layer mark is located on the second surface of the substrate. According to the invention, the metal mark is used as the front layer mark, so that the signal intensity of the front layer mark to infrared rays is improved, the measurement error of the overlay alignment mark is reduced, the OVL is improved, the photoetching precision is improved, and the product quality is improved, and the metal marks are formed while the metal interconnection structure is formed, so that the cost can be further reduced.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preparing an overlay alignment mark and its structure. Background technique [0002] The manufacture of integrated circuit chips, from a structural point of view, is similar to building a house. It starts from the substrate and builds up layer by layer. A certain degree of precision alignment must be ensured between layers, so as to ensure the normal function of the final chip. We define the layer-to-layer alignment metric as the registration accuracy (overlay, OVL). [0003] Registration accuracy and critical dimensions are the basic measurement indicators of the lithography process. The critical dimensions ensure the required line width on the chip, and the registration accuracy ensures the alignment of the lines between different layers. To put it simply, OVL is the alignment accuracy between the current layer and the previous layer in the lithography proc...

AI Technical Summary

Problems solved by technology

[0005] At present, for the measurement of the overlay alignment mark on the back, the infrared measurement method is usually used, but when the back is aligned, the signal strength of the front mark in the overlay alignment mark to the infrared ray is weak, which is easy to cause overlay alignment. The measurement error of the quasi-mark will cause errors in the photolithography step, resulting in product failure

[0006] In order to improve the overlay alignment accuracy, people have obtained partial satisfaction by improving lithography equipment, but the improvement and replacement of lithography equipment requires a large capital investment, resulting in a waste of funds

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