Mark with focusing and slant correction function and aligning method

Abstract

The invention discloses a mark with a focusing and slant correction function and an aligning method. The mark comprises an aligning mark and at least one pair of focusing marks, wherein the center of the aligning mark is positioned on the middle point of a connecting line of any pair of the focusing marks; the focusing marks of any pair are arranged on two sides of the aligning mark in a manner of central symmetry; the aligning mark is a crossed mark or a star-shaped mark; the focusing marks are square type focusing marks or grating type focusing marks; the line width of the aligning mark is greater than discretization granularity; and the line width of the aligning mark is greater than twice of PSF width. The invention also provides the aligning method applied to the mark, and high-precision focusing leveling of the aligning mark is realized. Compared with the prior art, according to the mark provided by the invention, the influence of inclination on the mark is eliminated during focusing, so that the measurement reproducibility is improved; and moreover, the influence mechanism of distortion on the measurement reproducibility is analyzed, limited conditions for mark width are given out, and the measurement reproducibility is further improved.

Description

technical field [0001] The present invention relates to a mark with focus adjustment and tilt correction design and an alignment method, in particular to a mark comprising an alignment mark and at least one pair of focus adjustment marks and an alignment method thereof. Background technique [0002] In the integrated circuit manufacturing process, a complete chip usually requires multiple photolithography exposures to complete. Except for the first layer of lithography, the other layers of lithography must be accurately positioned before exposure to the graphics of this level and the graphics (ie marks) left by the exposure of the previous level, so as to ensure that there is a correct relationship between the graphics of each layer. The relative position, that is, the overlay accuracy. [0003] In the prior art, an alignment system based on the principle of optical imaging is one of the commonly used systems in lithography machines, such as NikonFIA system, UltratecMVS and...

AI Technical Summary

Problems solved by technology

Its influence mechanism is that the nonlinear coupling between the position uncertainty of the measurement mark in the field of view and the distortion affects the measurement reproducibility, such as figure 2 shown

Although the FIA ​​system reduces the influence of distortion through multiple iterations so that the marker is always measured at a fixed position, the iterations consume a lot of time

[0006] Secondly, if image 3 As shown, the defocusing tilt effect of the mark will also affect the measurement reproducibility, and the tilt angle a of the measured object will produce an error D

Although the focus and leveling system in the photolithography machine can realize the correction of tilt and defocus, because the focus and leveling measurement surface is the upper surface of the photoresist, and the alignment mark is sometimes located on the lower surface of the photoresist, the photoresist The thickness has certain fluctuations, so the focus and leveling system is not enough to achieve high-precision focus and leveling of the alignment marks

[0007] In addition, in the optical imaging system, although the automatic focusing technology has been widely used in the alignment sensor, the sensor that realizes the tilt correction while the automatic focusing has not been invented yet

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