# US 11,307,490 B2 · Phase shift mask blank and phase shift mask

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- Number: US 11,307,490 B2
- Document ID: US11307490B2
- Status: Granted
- Kind: B2
- Application number: 16/832,395
- Filed: 2020-03-27
- Published: 2020-10-01
- Granted: 2022-04-19
- Earliest claimed: 2019-03-29
- Assignees: Shin-Etsu Chemical Co., Ltd.
- Applicants: Shin-Etsu Chemical Co., Ltd.
- Inventors: Takuro Kosaka
- Web page: https://patentgrep.com/patent/US11307490B2

## CPC

- G03F 1/32: Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof
- G03F 1/26: Phase shift masks [PSM]; PSM blanks; Preparation thereof
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

Provided is a phase shift mask blank including a substrate, and a phase shift film thereon, the phase shift film composed of a material containing silicon and nitrogen and free of a transition metal, the phase shift film including at least one compositionally graded layer having a composition continuously varying in a thickness direction, and a refractive index n and an extinction coefficient k, with respect to exposure light, varying in the thickness direction, the exposure light being KrF excimer laser, the compositionally graded layer having a difference between a maximum refractive index n(H) and a minimum refractive index n(L) of up to 0.40, and a difference between a maximum extinction coefficient k(H) and a minimum extinction coefficient k(L) of up to 1.5.

## Claims

### Claim 1

A phase shift mask blank comprising a substrate, and a phase shift film thereon, the phase shift film composed of a material containing silicon and nitrogen and free of a transition metal, wherein
the phase shift film has a phase shift of 170° to 190° and a transmittance of 4% to 8%, with respect to exposure light of KrF excimer laser, and a thickness of 85 to 90 nm,
the phase shift film comprises at least one compositionally graded layer having a composition continuously varying in a thickness direction, and a refractive index n and an extinction coefficient k, with respect to the exposure light, varying in the thickness direction, and
the compositionally graded layer has a difference between a maximum refractive index n(H) and a minimum refractive index n(L) of up to 0.40, and a difference between a maximum extinction coefficient k(H) and a minimum extinction coefficient k(L) of up to 1.5.

### Claim 2 (depends on 1)

The phase shift mask blank of claim 1, wherein the compositionally graded layer has a minimum refractive index n(L) of at least 2.3 and a maximum extinction coefficient k(H) of up to 2, the compositionally graded layer comprises a zone satisfying a refractive index n of at least 2.55 and an extinction coefficient k of up to 1.0, and said zone has a thickness of 5 to 30 nm.

### Claim 3 (depends on 1)

The phase shift mask blank of claim 1, wherein the compositionally graded layer has a zone continuously varying a content ratio N/(Si+N) within a range of 0.2 to 0.57 in a thickness direction, the ratio N/(Si+N) representing nitrogen content (at %) to the sum of silicon and nitrogen contents (at %).

### Claim 4 (depends on 1)

The phase shift mask blank of claim 1, wherein the compositionally graded layer has a difference between a maximum silicon content (at %) and a minimum silicon content (at %) of up to 30.

### Claim 5 (depends on 1)

The phase shift mask blank of claim 1, wherein in the phase shift film, a ratio of a deference between a maximum phase shift and a minimum phase shift to an average phase shift in plane of up to 3%, and a ratio of a deference between a maximum transmittance and a minimum transmittance to an average transmittance in plane of up to 5%.

### Claim 6 (depends on 1)

The phase shift mask blank of claim 1, wherein the material containing silicon and nitrogen and free of a transition metal is a material consisting of silicon and nitrogen.

### Claim 7 (depends on 1)

The phase shift mask blank of claim 1, further comprising a second layer consisting of a single layer or multiple layers on the phase shift film, the second layer being composed of a chromium-containing material.

### Claim 8 (depends on 1)

A phase shift mask having a patterned phase shift film manufactured by using the phase shift mask blank of claim 1.