Reflective mask blank for euv lithography

Patent metadata

Field	Value
Publication number	US-2016357100-A1
Application number	US-201615168572-A
Country	US
Kind code	A1
Filing date	May 31, 2016
Priority date	Jun 8, 2015
Publication date	Dec 8, 2016
Grant date	—

Abstract

To provide a reflective mask blank for EUV lithography which is excellent in flatness, whereby the deterioration of the overlay accuracy at the time of pattern transfer can be relatively easily corrected, and the deterioration of the overlay accuracy due to the flatness is small.
A reflective mask blank for EUVL, which is a reflective mask blank for EUV lithography having a reflective layer for reflecting EUV light and an absorber layer for absorbing EUV light formed in this order on the main surface of a substrate and having a conductive film formed on the rear surface opposite to the main surface, of the substrate, wherein when the shapes of quality-guaranteed regions of the main surface and the rear surface of the reflective mask blank for EUVL are measured by a laser interferometer, and the measured values obtained are fitted to quadratic function, the proportion of the quadratic function components is at least 35%, and the flatness at the quality-guaranteed regions of the main surface and the rear surface is at most 600 nm.

First claim

What is claimed is:

1 . A reflective mask blank for EUVL, which is a reflective mask blank for EUV lithography having a reflective layer for reflecting EUV light and an absorber layer for absorbing EUV light formed in this order on the main surface of a substrate and having a conductive film formed on the rear surface opposite to the main surface, of the substrate, wherein when the shapes of quality-guaranteed regions of the main surface and the rear surface of the reflective mask blank for EUVL are measured by a laser interferometer, and the measured values obtained are fitted to quadratic function, the proportion of the quadratic function components is at least 35%, and the flatness at the quality-guaranteed regions of the main surface and the rear surface is at most 600 nm.

2 . A reflective mask blank for EUVL, which is a reflective mask blank for EUV lithography having a reflective layer for reflecting EUV light and an absorber layer for absorbing EUV light formed in this order on the main surface of a substrate and having a conductive film formed on the rear surface opposite to the main surface, of the substrate, wherein when the shapes of quality-guaranteed regions of the main surface and the rear surface of the reflective mask blank for EUVL are measured by a laser interferometer, and the measured values obtained are fitted to quadratic function to obtain central coordinates F and B, the distances between the central coordinates F and B obtained and the center coordinate C of the substrate are at most 0.5 mm, and the flatness at the quality-guaranteed regions of the main surface and the rear surface is at most 600 nm.

3 . A reflective mask blank for EUVL, which is a reflective mask blank for EUV lithography having a reflective layer for reflecting EUV light and an absorber layer for absorbing EUV light formed in this order on the main surface of a substrate and having a conductive film formed on the rear surface opposite to the main surface, of the substrate, wherein the shapes of quality-guaranteed regions of the main surface and the rear surface of the reflective mask blank for EUVL and the shapes of quality-guaranteed regions of the main surface and the rear surface of the substrate before forming the reflective layer, the absorber layer and the conductive film are measured by a laser interferometer respectively, and the differences between the shapes of quality-guaranteed regions of the main surface and the rear surface of the reflective mask blank for EUVL and the shapes of quality-guaranteed regions of the main surface and the rear surface of the substrate, are fitted to quadratic function to obtain central coordinates ΔF and ΔB, the distances between the central coordinates ΔF and ΔB obtained and the center coordinate C of the substrate are at most 0.5 mm, and the flatness at the quality-guaranteed regions of the main surface and the rear surface is at most 600 nm.

4 . The reflective mask blank for EUVL according to claim 2 , wherein after forming at least one selected from the group consisting of the reflective layer, the absorber layer and the conductive film, heating treatment is carried out, and when the shapes of quality-guaranteed regions of the main surface and the rear surface are measured by a laser interferometer respectively before and after the heating treatment, and the differences of the shapes of the quality-guaranteed regions of the main surface and the rear surface before and after the heating treatment, are fitted to quadratic function to obtain central coordinates ΔF h and ΔB h , the distances between the central coordinates ΔF h and ΔB h obtained and the center coordinate C of the substrate are at most 0.5 mm.

5 . The reflective mask blank for EUVL according to claim 3 , wherein after forming at least one selected from the group consisting of the reflective layer, the absorber layer and the conductive film, heating treatment is carried out, and when the shapes of quality-guaranteed regions of the main surface and the rear surface are measured by a laser interferometer respectively before and after the heating treatment, and the differences of the shapes of the quality-guaranteed regions of the main surface and the rear surface before and after the heating treatment, are fitted to quadratic function to obtain central coordinates ΔF h and ΔB h , the distances between the central coordinates ΔF h and ΔB h obtained and the center coordinate C of the substrate are at most 0.5 mm.

6 . The reflective mask blank for EUVL according to claim 1 , wherein between the reflective layer and the absorber layer, a protective layer for the reflective layer is formed.

7 . The reflective mask blank for EUVL according to claim 2 , wherein between the reflective layer and the absorber layer, a protective layer for the reflective layer is formed.

8 . The reflective mask blank for EUVL according to claim 3 , wherein between the reflective layer and the absorber layer, a protective layer for the reflective layer is formed.

9 . The reflective mask blank for EUVL according to claim 1 , wherein on the absorber layer, a low reflective layer for inspection light to be used for inspection of a mask pattern is formed.

10 . The reflective mask blank for EUVL according to claim 2 , wherein on the absorber layer, a low reflective layer for inspection light to be used for inspection of a mask pattern is formed.

11 . The reflective mask blank for EUVL according to claim 3 , wherein on the absorber layer, a low reflective layer for inspection light to be used for inspection of a mask pattern is formed.

Assignees

• Asahi Glass Co Ltd

Inventors

• Ikuta Yoshiaki

Classifications

• G03F1/48

  Protective coatings · CPC title

• G03F7/0032

  characterised by heat providing or glossing means · CPC title

• G03F1/24 Primary

  Reflection masks; Preparation thereof · CPC title

• G03F1/22 Primary

  Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof · CPC title

• G03F7/2008

  characterised by the reflectors, diffusers, light or heat filtering means or anti-reflective means used · CPC title