Phase-shift mask manufacturing method

Abstract

A method for making a phase-shift mask is to form a thin mask layer on the sidewall of the patterned photoresist layer to cover the chromium layer after forming a patterned photoresist layer, and then to make a phase-shift layer to The patterned photoresist layer and the mask layer are used as masks to form phase shift openings on the transparent substrate. The chromium layer under the mask layer can precisely align itself with the phase shift layer, avoid alignment errors caused by multiple photolithography, improve the accuracy of the mask pattern, and can reduce a photolithography step and reduce the production of the mask cost.

Description

technical field [0001] The invention relates to a method for making a mask, and in particular to a method for making a phase shift mask (PSM), which can reduce the number of times the mask is subjected to photolithography and form an accurate mask pattern. Background technique [0002] In the semiconductor industry, photoresist patterns are made by using photolithography exposure tools such as steppers or scanners to expose on photosensitive materials to define the desired pattern. The steps are first to coat a layer of photoresist layer on the semiconductor substrate, use an exposure tool to project the pattern on the mask onto the photoresist layer, and then use a developer to develop the exposed part of the photoresist layer to make the photoresist layer appear. pattern on the mask. Afterwards, the patterned photoresist layer is used as a mask to perform subsequent etching or ion implantation processes. [0003] The mask is generally based on a transparent plate, on whi...

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Problems solved by technology

[0004] However, due to the increase in the complexity of semiconductor elements, the complexity of the mask pattern is relatively increased, making the pattern on the mask more dense, and the distance between the opaque regions is shortened, resulting in a decrease in the numerical aperture (Numerical Aperture).

When the numerical aperture is reduced and light penetrates the mask pattern, light diffraction occurs, which makes it impossible for traditional photolithography to improve

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