METHOD TO REDUCE NATIVE DEFECT PRINTABILITY

• US 20200133141A1
• Filed: 10/24/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: SHIH, Chih-Tsung, CHIEN, Tsung-Chih, LEE, Tsung Chuan
• Granted Patent: US 10,824,080 B2
• Time in Patent Office: Days
• CPC Class Codes: G03F 7/70641 Focus
• CPC Class Codes: G03F 7/70866 of mask or workpiece

Abstract

A method includes reducing refractive index of an environment at or adjacent an extreme ultraviolet (EUV) mask to below 1.0. The EUV mask is in an EUV lithography system that forms a projection beam of EUV radiation using EUV radiation emitted from a radiation source. The method further includes exposing the EUV mask to the projection beam of EUV radiation.

Claims

1. A method, comprising:

reducing refractive index of an environment at or adjacent an extreme ultraviolet (EUV) mask to below 1.0, wherein the EUV mask is in an EUV lithography system that forms a projection beam of EUV radiation using EUV radiation emitted from a radiation source; and

exposing the EUV mask to the projection beam of EUV radiation.

2. The method of claim 1, wherein reducing the refractive index of the environment at or adjacent the EUV mask comprises generating a plasma in the environment.

3. The method of claim 2, wherein the EUV mask includes a substrate and a multi-layer (ML) structure formed on the substrate, and one or more of the substrate and multi-layer (ML) structure includes a defect.

4. The method of claim 3, wherein the generated plasma reduces destructive optical interference caused by the defect.

5. The method of claim 3, wherein generating the plasma in the environment reduces an effect of the defect on a semiconductor wafer that is exposed to the projection beam of EUV radiation.

6. The method of claim 2, wherein generating the plasma includes generating plasma having a density between 2×

10²⁵ ions/m³ to 2×

10³⁵ ions/m³.

7. The method of claim 2, wherein the plasma is generated adjacent the EUV mask.

8. The method of claim 1, wherein the refractive index of the environment includes is reduced to about 0.5-0.8.

9. An extreme ultraviolet (EUV) lithography system, comprising:

an extreme ultraviolet (EUV) radiation source;

a collector for collecting EUV radiation and focusing the EUV radiation;

a reticle stage supporting an EUV mask; and

a plasma adjacent the reticle stage, the plasma reducing a refractive index of an environment around the EUV mask to below 1.0.

10. The EUV lithography system of claim 9, wherein the EUV mask includes a substrate and a multi-layer (ML) structure formed on the substrate, and one or more of the substrate and multi-layer (ML) structure includes a defect.

11. The EUV lithography system of claim 10, wherein the plasma reduces destructive optical interference caused by the defect.

12. The EUV lithography system of claim 10, wherein the plasma reduces an effect of the defect on a semiconductor wafer that is exposed to the EUV radiation.

13. The EUV lithography system of claim 10, wherein the plasma increases an intensity of EUV radiation reflecting from a location of the EUV mask that includes the defect.

14. The EUV lithography system of claim 9, wherein the plasma has a density between 2×

10²⁵ ions/m³ to 2×

10³⁵ ions/m³.

15. The EUV lithography system of claim 9, wherein the plasma reduces the refractive index of the environment around the EUV mask to about 0.5-0.8.

16. The EUV lithography system of claim 9, wherein the plasma is located adjacent the EUV mask.

17. The EUV lithography system of claim 9, wherein the EUV mask is a reflective mask.

18. A method, comprising:

generating plasma to reduce a refractive index of an environment around an extreme ultraviolet (EUV) mask in an EUV lithography system to below 1.0, wherein the EUV lithography system forms a projection beam of EUV radiation using EUV radiation emitted from a radiation source;

exposing the EUV mask to the projection beam of EUV radiation; and

exposing a photoresist coated semiconductor wafer to the projection beam of EUV radiation reflecting off the EUV mask, wherein the plasma reduces an effect of a defect in the EUV mask on the photoresist coated semiconductor wafer that is exposed to the projection beam of EUV radiation.

19. The method of claim 18, wherein generating the plasma includes generating plasma having a density between 2×

10²⁵ ions/m³ to 2×

10³⁵ ions/m³.

20. The method of claim 18, wherein the refractive index of the environment is reduced to between 0.5 and 0.8.