Mask for EUV lithography, EUV lithography apparatus and method for determining a contrast proportion caused by DUV radiation

Patent metadata

Field	Value
Publication number	US-10156782-B2
Application number	US-201715431306-A
Country	US
Kind code	B2
Filing date	Feb 13, 2017
Priority date	Aug 13, 2014
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

A mask (M) for EUV lithography includes: a substrate ( 7 ), a first surface region (A 1 ) formed by a surface ( 8 a ) of a multilayer coating ( 8 ) embodied to reflect EUV radiation ( 27 ), said surface ( 8 a ) facing away from the substrate ( 7 ), and a second surface region (A 2 ) formed by a surface ( 18 a ) of a further coating ( 18 ) embodied to reflect DUV radiation ( 28 ) and to suppress the reflection of EUV radiation ( 27 ), said surface ( 18 a ) facing away from the substrate ( 7 ). The further coating is a multilayer coating ( 18 ). Also disclosed are an EUV lithography apparatus that includes such a mask (M) and a method for determining a contrast proportion caused by DUV radiation when imaging a mask (M) onto a light-sensitive layer.

First claim

What is claimed is:

1. A mask for extreme ultraviolet (EUV) lithography, comprising:
a substrate having:
a first surface region (A 1 ) formed by a surface of a multilayer coating embodied to reflect EUV radiation, said multilayer coating surface facing away from the substrate, and
a second surface region (A 2 ) formed by a surface of a further coating embodied to reflect deep ultraviolet (DUV) radiation and to suppress the reflection of the EUV radiation, said further coating surface facing away from the substrate, wherein the further coating is a further multilayer coating,
wherein the wavelength-dependent reflectivity of the further multilayer coating for the DUV radiation in the wavelength range between 140 nm and 400 nm does not deviate by more than +/−5% from the wavelength-dependent reflectivity of the multilayer coating.

2. The mask as claimed in claim 1 , further comprising: a third surface region (A 3 ) formed by a surface of a coating absorbing the EUV radiation, said EUV radiation absorbing surface facing away from the substrate.

3. The mask as claimed in claim 1 , wherein the reflectivity of the further coating is less than 0.3% at a used wavelength (λ B ) of the EUV radiation at which the reflectivity of the multilayer coating is at a maximum.

4. The mask as claimed in claim 1 , wherein the multilayer coating comprises a plurality of alternating layers made respectively of a layer material with a high refractive index and a layer material with a low refractive index.

5. The mask as claimed in claim 4 , wherein the layer materials of the alternating layers of the multilayer coating and of the further multilayer coating are identical.

6. The mask as claimed in claim 1 , wherein the surface of the multilayer coating forms a contiguous first surface region (A 1 ) of the mask, said first surface region covering 30% or more of the surface (A 1 +A 2 +A 3 ) of the mask provided for imaging.

7. The mask as claimed in claim 1 , wherein the surface of the further multilayer coating forms a contiguous second surface region (A 2 ) of the mask, said second surface region covering 30% or more of the surface (A 1 +A 2 +A 3 ) of the mask provided for imaging.

8. The mask as claimed in claim 1 , wherein the wavelength-dependent reflectivity of the further multilayer coating for the DUV radiation in the wavelength range between 140 nm and 400 nm does not deviate by more than +/−1% from the wavelength-dependent reflectivity of the multilayer coating.

9. The mask as claimed in claim 3 , wherein the reflectivity of the further coating is less than 0.1%, at a used wavelength (λ B ) of the EUV radiation at which the reflectivity of the multilayer coating is at a maximum.

10. An EUV lithography apparatus comprising: a mask as claimed in claim 1 .

11. A method for determining a contrast proportion (K DUV /K DUV+EUV ) caused by DUV radiation when imaging a mask onto a light-sensitive layer, comprising:
illuminating the mask with radiation for imaging the mask onto the light-sensitive layer,
determining a radiation dose (D 1 ) required for exposing a first region (B 1 ) of the light-sensitive layer, wherein radiation which is reflected at a multilayer coating of the mask is incident on the light-sensitive layer in the first region, said multilayer coating being embodied both to reflect EUV radiation and to reflect DUV radiation, and
determining a radiation dose (D 2 ) required for exposing a second region (B 2 ) of the light-sensitive layer, wherein radiation which is reflected by a further coating of the mask is incident on the light-sensitive layer in the second region (B 2 ), said further coating being embodied to suppress EUV radiation and to reflect DUV radiation, and
determining the contrast proportion (K DUV /K DUV+EUV ) by comparing the radiation doses (D 1 , D 2 ) required for exposing the first region (B 1 ) and for exposing the second region (B 2 ),
wherein the wavelength-dependent reflectivity of the further coating, which is embodied as a multilayer coating, for DUV radiation in the wavelength range between 140 nm and 400 nm is selected to not deviate by more than +/−5% from the wavelength-dependent reflectivity of the multilayer coating.

12. The method as claimed in claim 11 , wherein the contrast proportion K DUV /K DUV+EUV is determined from the radiation dose D 1 required for exposing the first region (B 1 ) and the radiation dose D 2 required for exposing the second region (B 2 ) in accordance with the following formula:
K DUV /K DUV+EUV =D 1 /D 2 .

13. The method as claimed in claim 11 , further comprising: determining a radiation dose (D 3 ) required for exposing a third region (B 3 ) of the light-sensitive layer, wherein radiation which is reflected by a coating which absorbs EUV radiation is incident on the light-sensitive layer in the third region (B 3 ), and determining the contrast proportion (K DUV /K DUV+EUV ) taking into account the radiation dose (D 3 ) required for exposing the third region (B 3 ).

14. The method as claimed in claim 13 , wherein the contrast proportion K DUV /K DUV+EUV is determined from the radiation dose D 1 required for exposing the first region (B 1 ), the radiation dose D 2 required for exposing the second region (B 2 ) and the radiation dose D 3 required for exposing the third region (B 3 ) in accordance with the following formula:
K DUV /K DUV+EUV =( A 3 /D 3 +( A 1 +A 2 )/ D 2 )/( A 3 /D 3 +( A 1 +A 2 )/ D 1 ),

where A 1 , A 2 , A 3 denote areas of the surfaces of the multilayer coating, the further coating and the coating which absorbs EUV radiation.

15. The method as claimed in claim 11 , wherein the further coating is embodied as a multilayer coating.

16. The method as claimed in claim 11 , wherein the wavelength-dependent reflectivity of the further coating, which is embodied as a multilayer coating, for DUV radiation in the wavelength range between 140 nm and 400 nm is selected to not deviate by more than +/−1% from the wavelength-dependent reflectivity of the multilayer coating.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Huber Peter

Classifications

• G03F1/44

  Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales · CPC title

• G03F7/70941

  Stray fields and charges, e.g. stray light, scattered light, flare, transmission loss · CPC title

• G03F1/24 Primary

  Reflection masks; Preparation thereof · CPC title

• G03F1/58

  having two or more different absorber layers, e.g. stacked multilayer absorbers · CPC title

• G03F7/70616

  Monitoring the printed patterns · CPC title