US 7,678,509 B2Granted

Method of producing phase shift masks

AssigneeHoya Corporation

InventorHideki Suda

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Abstract

A light-shielding film pattern 2a having a main opening 5 and auxiliary openings 6 is formed in a first process and, then, recess etching of a transparent substrate (formation of a substrate etched portion 8) is performed in a second process. Thus, the main opening and auxiliary openings can be simultaneously exposed in the first process and the positioning accuracy of them becomes excellent. Patterning of a light-shielding film 2 is performed by the use of an etching mask layer 3a and therefore the processing accuracy of the light-shielding film becomes excellent. The etching mask layer 3a is removed in a third process as the final process and thus the light-shielding film pattern 2a can be protected by the etching mask layer 3a upon recess-etching the transparent substrate in the second process. Thus, it is possible to prevent damage to the light-shielding film pattern 2a in the recess etching of the transparent substrate. Specifically, the etching mask layer 3a itself is damaged in the recess etching of the transparent substrate and this etching mask layer 3a is removed in the third process, causing no problem.

A method of manufacturing a phase shift mask having, on a transparent substrate, a main opening formed by partly removing a light-shielding film and an auxiliary opening provided at a peripheral portion of said main opening, said auxiliary opening having a width incapable of being resolved when transferring, wherein the transparent substrate is partly removed in a depth direction such that phases of light passing through the main opening and light passing through the auxiliary opening differ from each other by a predetermined angle, comprising:

a first process including
a step of preparing a photomask blank having the light-shielding film, a thin film for forming an etching mask layer, and a first resist film which are formed in this order on the transparent substrate,
said light-shielding film comprising a material being etchable by a fluorine-based etching medium,
said thin film having a resistance to the fluorine-based etching medium, comprising a metal selected from chromium, tantalum, titanium, aluminum, hafnium, vanadium, or zirconium, an alloy of one or more of said metals, a metal compound containing one or more of oxygen, nitrogen, carbon, fluorine along with one of said metal or alloy,
a step of exposing a pattern corresponding to the main opening and the auxiliary opening onto the first resist film and then developing to form a first resist pattern, a step of, using said first resist pattern as a mask, etching the thin film to form the etching mask layer, a step of, using the etching mask layer as a mask, etching the light-shielding film, and a step of stripping the remaining first resist pattern,
a second process including a step of forming a second resist film on the transparent substrate obtained in the first process, a step of exposing a pattern corresponding to one of the main opening and the auxiliary opening and then developing to form a second resist pattern, a step of, using the second resist pattern as a mask, etching part of the transparent substrate to a depth such that the phases of the light passing through the main opening and the light passing through the auxiliary opening differ from each other by the predetermined angle, and a step of stripping the remaining second resist pattern, and
a third process including a step of removing a part of or whole of the etching mask layer.

4 more elements

Abstract

Claims13