Mask for EUV lithography and method of manufacturing the same

1. A method of manufacturing an extreme ultraviolet (EUV) lithography mask, the method comprising:

forming an image pattern in an absorption layer of EUV mask blank,

the EUV mask blank including:

a multilayer stack comprising alternating molybdenum (Mo) and silicon (Si) layers disposed over a first surface of a mask substrate;

a capping layer disposed over the multilayer stack; and

an absorption layer disposed over the capping layer;

forming a border region surrounding the image pattern to form a trench wherein the absorption layer, the capping layer and a portion of the multilayer stack are etched and a part of the multilayer stack remains;

forming concave sidewalls in the border region; and

converting an entirety of the remaining part of the multilayer stack and a part of a sidewall of the trench into an inter-diffused portion,

wherein the inter-diffused portion includes a non-periodic structure of silicon and molybdenum, thereby causing a reduced EUV reflectivity,

the inter-diffused portion is in direct contact with the first surface of the mask substrate, and

a periodic structure of the multilayer stack partially remains on the sidewall of the trench and is exposed to the trench.

2. The method of claim 1 , wherein the concave sidewalls include a protruding portion.

3. The method of claim 2 , wherein the protruding portion comprises a material selected from the group consisting of TaBO, TaBN, or a combination thereof.

4. The method of claim 2 , wherein the protruding portion of the concave sidewalls have a width in a range from 10 nm to 50 nm.

5. The method of claim 2 , wherein the protruding portion has a tapered profile.

6. The method of claim 1 , wherein the concave sidewalls are formed by isotropically etching the multilayer stack.

7. The method of claim 1 , wherein the inter-diffused portion is formed by a laser annealing operation.

8. The method of claim 1 , wherein the remaining periodic structure is located at an upper part of the sidewall of the trench and in contact with the absorption layer.

9. The method of claim 8 , wherein the inter-diffused portion has a U-shape cross section.

10. A method of manufacturing an extreme ultraviolet (EUV) lithography mask, the method comprising:

forming an image pattern in an absorption layer of EUV mask blank,

the EUV mask blank including:

a multilayer stack comprising alternating molybdenum (Mo) and silicon (Si) layers disposed over a first surface of a mask substrate;

a capping layer disposed over the multilayer stack; and

an absorption layer disposed over the capping layer;

forming a border region surrounding the image pattern having a trench wherein the absorption layer, the capping layer and a portion of the multilayer stack are etched and a part of the multilayer stack remains; and

converting an entirety of the remaining part of the multilayer stack and a part of a sidewall of the trench into an inter-diffused portion,

wherein the inter-diffused portion includes a non-periodic structure of silicon and molybdenum, causing a reduced EUV reflectivity, and

wherein a bottom surface of the border region is fully covered by the inter-diffused portion so that the inter-diffused portion is in direct contact with the first surface of the mask substrate, and a periodic structure of the multilayer stack partially remains on the sidewall of the trench and is exposed to the trench.

11. The method of claim 10 , wherein the inter-diffused portion is formed by a laser annealing operation.

12. The method of claim 11 , wherein the laser has a wavelength in a range from 266 nm to 1523 nm.

13. The method of claim 11 , wherein the laser has a resolution in a range from 0.1 μm to 250 μm.

14. The method of claim 11 , wherein the laser has a pulse time in a range from 0.1 ns to 2 ms.

15. The method of claim 11 , wherein heat from the laser diffuses laterally a distance in a range from 0.1 μm to 10 μm.

16. A mask for extreme ultraviolet (EUV) lithography, the mask comprising:

a multilayer stack comprising alternating molybdenum (Mo) and silicon (Si) layers disposed over a first surface of a mask substrate;

a capping layer disposed over the multilayer stack;

an absorption layer having an image pattern formed therein disposed over the capping layer;

a border region surrounding the image pattern having a trench wherein the absorption layer, the capping layer and at least a portion of the multilayer stack are etched,

wherein the border region has concave sidewalls, and

wherein an inter-diffused portion that includes a non-periodic structure of silicon and molybdenum, thereby causing a reduced EUV reflectivity, is disposed under a bottom of the trench,

the inter-diffused portion is in direct contact with the first surface of the mask substrate, and

a periodic structure of the multilayer stack partially remains on a sidewall of the trench and is exposed to the trench.

17. The mask of claim 16 , wherein the concave sidewalls include at least one protruding portion comprising a material selected from the group consisting of TaBO, TaBN, or a combination thereof.

18. The mask of claim 17 , wherein the at least one protruding portion has a tapered shape.

19. The mask of claim 17 , wherein the at least one protruding portion of the concave sidewalls have a width in a range of 10 nm to 50 nm.

20. The mask of claim 16 , further including an inter-diffused portion over the multilayer stack of the trench that is connected to the inter-diffused portion disposed over the bottom surface of the border region.