An alignment mark for an exposure device

Abstract

The invention provides an alignment mark for an exposure device. Simultaneously, the alignment mark is technically characterized in that a, the whole body of the alignment mark is connected, namely any line in the alignment mark has a crossed line; b, the alignment mark is a central symmetric figure; c, a peripheral outline (the crossed part of a mark periphery and a background) of the alignment mark is communicated (namely, any place along the outline is used as a starting point and the alignment mark always returns to the starting point no matter whether the alignment mark walks in a clockwise direction or an anticlockwise direction along the outline); d, the minimum line width and the gap size for forming the alignment mark are greater than the limiting resolution of a measurement lens of the alignment mark; e, no less than four horizontal or vertical lines for forming the alignment mark are arranged in each direction. The alignment mark disclosed by the invention has obvious outline characteristics and is the central symmetric figure, so that the resolution is improved; meanwhile, the lengths of the horizontal line and the vertical lines of the alignment mark are the same and the alignment precision is improved.

Description

technical field [0001] The invention relates to the technical field of semiconductor manufacturing, in particular to an alignment mark used in an alignment system of an exposure device of a lithography machine. Background technique [0002] The alignment system is a very important core subsystem of semiconductor lithography equipment, and its alignment accuracy often directly determines the overlay accuracy that semiconductor lithography equipment can achieve. The semiconductor lithography equipment projects the circuit pattern drawn on the reticle onto the surface of the exposure object such as a silicon wafer coated with a photosensitive material through an optical projection method. Then, the pattern transfer between the mask plate and the exposure object is realized through etching and other processes. Since chips are composed of multiple layers of circuits, integrated circuit chips usually require multiple exposures to complete. In order to ensure the precise position...

AI Technical Summary

Problems solved by technology

[0005] (1) There are fewer horizontal and vertical lines of the alignment mark, resulting in less signal volume in the two directions, such as figure 1 The o mark in , makes the repeatability measurement of the alignment mark more susceptible to the noise of the image sensor, making the alignment accuracy worse;

[0006] (2) The mark is not connected, such as figure 1 The middle p marks, irregular symmetry, or does not have a unique centroid, such as figure 1 In the q-r mark, since the alignment of different process layers of semiconductors is based on the center of the mark, and the reference point of the template matching method commonly used in machine vision methods is generally based on the center of the template image, it is impossible to align the mark template for correction;

[0007] (3) According to the optical principle, when the size of the lines and gaps is smaller than the limit resolution of the lens of the alignment device, the marking lines observed by the alignment device will be connected together, resulting in indistinguishable marks

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