Multilayer mirror for reflecting EUV radiation and method for producing the same

Patent metadata

Field	Value
Publication number	US-11500137-B2
Application number	US-201716338013-A
Country	US
Kind code	B2
Filing date	Sep 25, 2017
Priority date	Oct 6, 2016
Publication date	Nov 15, 2022
Grant date	Nov 15, 2022

Abstract

A multilayer mirror for reflecting Extreme Ultraviolet (EUV) radiation and a method for producing the same are disclosed. In an embodiment a multilayer mirror includes a layer sequence having a plurality of alternating first layers and second layers, the first layers including lanthanum or a lanthanum compound and the second layers including boron, wherein the second layers are doped with carbon, and wherein a molar fraction of carbon in the second layers is 10% or less.

First claim

The invention claimed is:

1. A multilayer mirror for Extreme Ultraviolet (EUV) radiation comprising:
a layer sequence having a plurality of alternating first layers and second layers, the first layers comprising lanthanum or a lanthanum compound and the second layers comprising boron,
wherein the second layers are doped with carbon, and
wherein a molar fraction of carbon in the second layers is 10% or less.

2. The multilayer mirror according to claim 1 , wherein the molar fraction of carbon in the second layers is 5% or less.

3. The multilayer mirror according to claim 1 , wherein the molar fraction of carbon in the second layers is 3% or less.

4. The multilayer mirror according to claim 1 , wherein the lanthanum compound is a lanthanum nitride, a lanthanum oxide or a lanthanum carbide.

5. The multilayer mirror according to claim 1 , wherein the first layers and the second layers each have a thickness between 1 nm and 3 nm.

6. The multilayer mirror according to claim 1 , further comprising thin barrier layers arranged at interfaces between the first layers and the second layers, wherein the thin barrier layers comprise B 4 C or C and have a thickness of not more than 1.0 nm.

7. The multilayer mirror according to claim 1 , wherein the layer sequence is a periodic layer sequence, wherein a period comprises a layer pair of one of the plurality of first layers and one of the plurality of second layers, and wherein the period has a thickness in a range from 3 nm to 4 nm.

8. The multilayer mirror according to claim 1 , wherein the layer sequence comprises between 100 and 400 layer pairs, each layer pairs having one of the first layers and one of the second layers.

9. A method for producing a multilayer mirror for an Extreme Ultraviolet (EUV) spectral range, the method comprising:
alternately depositing first layers comprising lanthanum or a lanthanum compound and second layers comprising boron, wherein the second layers are doped with carbon, and wherein a molar fraction of carbon in the second layers is 10% or less.

10. The method according to claim 9 , wherein depositing the first and second layers comprises DC magnetron sputtering the first layers and the second layers.

11. The method according to claim 10 , wherein the DC magnetron sputtering uses a sputtering target comprising carbon-doped boron for sputtering the second layers.

12. The method according to claim 11 , wherein the carbon in the sputtering target has a molar fraction of 10% or less.

13. The method according to claim 10 , wherein the DC magnetron sputtering is performed at room temperature.

Assignees

• Fraunhofer Ges Forschung

Inventors

• Naujok Philipp
• Yulin Sergiy
• Kaiser Norbert

Classifications

• C23C14/0605

  Carbon · CPC title

• G21K2201/061

  characterised by a multilayer structure · CPC title

• C23C28/44

  characterized by a measurable physical property of the alternating layer or system, e.g. thickness, density, hardness · CPC title

• G02B13/143

  for use with ultraviolet radiation · CPC title

• G02B5/0891 Primary

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