# US 12,216,398 B2 · Reflective mask blank and reflective mask

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- Number: US 12,216,398 B2
- Document ID: US12216398B2
- Status: Granted
- Kind: B2
- Application number: 18/417,352
- Filed: 2024-01-19
- Published: 2024-05-30
- Granted: 2025-02-04
- Earliest claimed: 2019-10-29
- Assignees: AGC Inc.
- Applicants: Agc Inc.
- Inventors: Hiroyoshi Tanabe; Hiroshi Hanekawa; Toshiyuki Uno
- Web page: https://patentgrep.com/patent/US12216398B2

## CPC

- G03F 1/24: Reflection masks; Preparation thereof
- G03F 1/26: Phase shift masks [PSM]; PSM blanks; Preparation thereof
- G03F 1/32: Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof
- G03F 7/20: Exposure; Apparatus therefor (photographic printing apparatus for making copies G03B27/00)
- G03F 1/52: Reflectors
- G03F 1/54: Absorbers, e.g. of opaque materials
- 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

A reflective mask blank includes a substrate and, on or above the substrate in order, a reflective layer for reflecting EUV light, a protective layer for protecting the reflective layer, and an absorbent layer for absorbing EUV light. The absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10% and consists of a lower absorption layer and an upper absorption layer. A film thickness dbi of the absorbent layer satisfies a relationship of: dbi MAX−(i×6+1) nm≤dbi≤dbi MAX−(i×6−1) nm where the integer i is 0 or 1, and dbi MAX is represented by: d bi ⁢ MAX ( nm ) = 13.53 2 ⁢ n ⁢ cos ⁢ 6 ⁢ ° { INT ( 0.58 1 - n 1 ) + 1 2 ⁢ π ⁢ ( tan - 1 ( - k 2 1 - n 2 ) + 0.64 ) } , where n1 is a refractive index of the lower absorbent layer, n2 is a refractive index of the upper absorbent layer, k2 is an absorption coefficient of the upper absorbent layer, and INT(x) is a function of returning an integer value obtained by truncating a decimal part.

## Claims

### Claim 1

A reflective mask blank comprising a substrate and, on or above the substrate in order, a reflective layer for reflecting EUV light, a protective layer for protecting the reflective layer, and an absorbent layer for absorbing EUV light,
wherein the absorbent layer has a reflectance for a wavelength of 13.53 nm of from 2.5% to 10%,
the absorbent layer consists of two layers of a lower absorbent layer and an upper absorbent layer, and
a film thickness dbi of the absorbent layer consisting of the two layers satisfies a relationship of:
dbi MAX−(i×6+1) nm≤dbi≤dbi MAX−(i×6−1) nm
wherein the integer i is 0 or 1, and dbi MAX is represented by:
d
bi
⁢
MAX
(
nm
)
=
13.53
2
⁢
n
⁢
cos
⁢
6
⁢
°
{
INT
(
0.58
1
-
n
1
)
+
1
2
⁢
π
⁢
(
tan
-
1
(
-
k
2
1
-
n
2
)
+
0.64
)
}
,
wherein n1 is a refractive index of the lower absorbent layer, n2 is a refractive index of the upper absorbent layer, k2 is an absorption coefficient of the upper absorbent layer, and INT (x) is a function of returning an integer value obtained by truncating a decimal part.

### Claim 2 (depends on 1)

The reflective mask blank according to claim 1, wherein a phase difference of a reflected light for a wavelength of 13.53 nm of the absorbent layer relative to a reflected light for a wavelength of 13.53 nm of the reflective layer is from 190° to 220°.

### Claim 3 (depends on 1)

The reflected mask blank according to claim 1, wherein the absorbent layer comprises one or more elements selected from the group consisting of Ta, Nb, Mo, Ti, Zr, Re, Ru, Au, Pt, Pd, Rh, B, N, and O.

### Claim 4 (depends on 1)

The reflected mask blank according to claim 1, wherein denoting as λMAX a peak wavelength in a reflected light spectrum of the absorbent layer, the peak wavelength satisfies:
(
13.53
+
i
10
-
0.1
)
⁢
nm
≤
λ
MAX
≤
(
13.53
+
i
10
+
0.1
)
⁢
nm
,
in correspondence to the integer i.

### Claim 5 (depends on 1)

The reflective mask blank according to claim 1, comprising a hard mask layer on the absorbent layer.

### Claim 6 (depends on 5)

The reflective mask blank according to claim 5, wherein the hard mask layer comprises at least one element of Cr and Si.

### Claim 7 (depends on 1)

The reflective mask blank according to claim 1, comprising a backside electroconductive layer on a backside of the substrate.

### Claim 8 (depends on 7)

The reflective mask blank according to claim 7, wherein a material of the backside electroconductive layer is Cr, Ta, or an alloy of Cr or Ta.

### Claim 9 (depends on 2)

A reflective mask obtained by forming a pattern in the absorbent layer of the reflective mask blank according to claim 2.