Graded interface in bragg reflector

Patent metadata

Field	Value
Publication number	US-11327394-B2
Application number	US-202016850665-A
Country	US
Kind code	B2
Filing date	Apr 16, 2020
Priority date	Apr 19, 2019
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

A multilayer stack in the form of a Bragg reflector comprising a graded interfacial layer and a method of manufacturing are disclosed. The graded interfacial layer eliminates the formation of low-reflectivity interfaces in a multilayer stack and reduces roughness of interfaces in a multilayer stack.

First claim

What is claimed is:

1. A Bragg reflector comprising:
a multilayer stack of reflective layers on a substrate, the multilayer stack of reflective layers including a plurality of reflective layers including reflective layer pairs of a first layer of material A and a second layer of material B and graded interfacial layers between the first layer of material A and the second layer of material B, the graded interfacial layers comprising the first material A and the second material B, wherein the graded interfacial layers have a thickness, and the graded interfacial layers comprise a density gradient across the thickness.

2. The Bragg reflector of claim 1 , wherein each of the graded interfacial layers comprises a composition gradient across the thickness.

3. An extreme ultraviolet (EUV) mask blank comprising the Bragg reflector of claim 1 , wherein the first layer of material A comprises molybdenum (Mo) and the second layer of material B comprises silicon (Si), wherein the reflective layer pair reflects EUV radiation.

4. The extreme ultraviolet (EUV) mask blank of claim 3 , wherein the graded interfacial layers comprise MoSi x .

5. The extreme ultraviolet (EUV) mask blank of claim 4 , further comprising a capping layer on the multilayer stack of reflective layers.

6. The extreme ultraviolet (EUV) mask blank of claim 5 , further comprising an absorber layer on the capping layer.

7. The extreme ultraviolet (EUV) mask blank of claim 6 , wherein the graded interfacial layers increase the reflectance of the multilayer stack of reflective layers by greater than or equal to 2% versus a comparable multilayer stack of reflective layers that does not comprise graded interfacial layers.

8. The Bragg reflector of claim 2 , wherein the graded interfacial layers have a first region rich in material A adjacent to the first layer and a second region rich in material B adjacent to the second layer.

9. The EUV mask blank of claim 4 , wherein where x is a number from 0 to 2, and the material A comprises Si and the material B comprises Mo.

10. The EUV mask blank of claim 9 , wherein the graded interfacial layers have a first region rich in Mo adjacent to the first layer and a second region rich in Si adjacent to the second layer.

Assignees

• Applied Materials Inc

Inventors

• Xiao Wen
• Jindal Vibhu
• Li Weimin
• Liu Shuwei

Classifications

• G03F7/70316

  Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements · CPC title

• G03F7/7015

  Details of optical elements · CPC title

• G03F1/52

  Reflectors · CPC title

• G03F1/24 Primary

  Reflection masks; Preparation thereof · CPC title

• G02B5/0891

  Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06) · CPC title