Metal Gate Scheme for Device and Methods of Forming

• US 20160322471A1
• Filed: 06/04/2015
• Published: 11/03/2016
• Est. Priority Date: 04/30/2015
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: JangJian, Shiu-Ko, Liu, Chi-Wen, Wu, Chih-Nan, Lin, Chun Che
• Granted Patent: US 9,941,376 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/28088 the final conductor layer next to the insulator being a composite, e.g. TiN
• CPC Class Codes: H01L 21/823842 gate conductors with different gate conductor materials or different gate conductor implants, e.g. dual gate structures
• CPC Class Codes: H01L 29/165 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/4966 the conductor material next to the insulator being a composite material, e.g. organic material, TiN, MoSi2 H01L29/4908, H01L29/4983 take precedence
• CPC Class Codes: H01L 29/66545 using a dummy, i.e. replacement gate in a process wherein at least a part of the final gate is self aligned to the dummy gate
• CPC Class Codes: H01L 29/66636 with source or drain recessed by etching or first recessed by etching and then refilled
• CPC Class Codes: H01L 29/7834 with a non-planar structure, e.g. the gate or the source or the drain being non-planar
• CPC Class Codes: H01L 29/7848 the means being located in the source/drain region, e.g. SiGe source and drain

Abstract

Gate structures and methods of forming the gate structures are described. In some embodiments, a method includes forming source/drain regions in a substrate, and forming a gate structure between the source/drain regions. The gate structure includes a gate dielectric layer over the substrate, a work function tuning layer over the gate dielectric layer, a first metal over the work function tuning layer, an adhesion layer over the first metal, and a second metal over the adhesion layer. In some embodiments, the adhesion layer can include an alloy of the first and second metals, and may be formed by annealing the first and second metals. In other embodiments, the adhesion layer can include an oxide of at least one of the first and/or second metal, and may be formed at least in part by exposing the first metal to an oxygen-containing plasma or to a natural environment.

Claims

1. A method comprising:

forming a first source/drain region and a second source/drain region in a substrate; and

forming a gate structure between the first source/drain region and the second source/drain region and over the substrate, the gate structure comprising;

a gate dielectric layer over the substrate,

a work function tuning layer over the gate dielectric layer,

a first metal over the work function tuning layer,

an adhesion layer over the first metal, and

a second metal over the adhesion layer, the second metal being different from the first metal.

2. The method of claim 1, wherein the adhesion layer comprises an alloy of the first metal and the second metal.

3. The method of claim 1, wherein the adhesion layer is an oxide of the first metal.

4. The method of claim 1, wherein the adhesion layer comprises a first sub-layer of an oxide of the first metal and a second sub-layer of an oxide of the second metal.

5. The method of claim 1, wherein the adhesion layer is an oxide of a mixture of the first metal and the second metal.

6. The method of claim 1, wherein the forming the gate structure comprises:

depositing the first metal over the work function tuning layer;

depositing the second metal over the first metal; and

after depositing the first metal and the second metal, forming the adhesion layer by annealing the first metal and the second metal.

7. The method of claim 1, wherein the forming the gate structure comprises:

depositing, in a chamber, the first metal over the work function tuning layer;

after depositing the first metal, allowing a natural environment in the chamber; and

after allowing the natural environment in the chamber, depositing, in the chamber, the second metal over the first metal, wherein the adhesion layer comprises an oxide formed at least in part by allowing the natural environment in the chamber.

8. The method of claim 1, wherein the forming the gate structure comprises:

depositing the first metal over the work function tuning layer;

after depositing the first metal, exposing the first metal to an oxygen-containing plasma; and

after exposing the first metal to the oxygen-containing plasma, depositing the second metal over the first metal, wherein the adhesion layer comprises an oxide formed at least in part by exposing the first metal to the oxygen-containing plasma.

9. The method of claim 1 further comprising:

forming a buffer layer over the gate structure, the buffer layer comprising an oxide of the second metal; and

forming a dielectric cap over the buffer layer.

10. A method comprising:

forming a first source/drain region and a second source/drain region in a substrate;

forming an inter-layer dielectric over the substrate, an opening being through the inter-layer dielectric to the substrate, the opening being between the first source/drain region and the second source/drain region;

forming a gate dielectric layer in the opening and over the substrate;

forming a work function tuning layer in the opening and over the gate dielectric layer;

forming a first metal in the opening and over the work function tuning layer;

forming a second metal in the opening and over the first metal, the second metal being different from the first metal; and

forming an adhesion layer between the first metal and the second metal.

11. The method of claim 10, wherein the adhesion layer is an oxide of the first metal.

12. The method of claim 10, wherein the adhesion layer is a composite of a first sub-layer of an oxide of the first metal and a second sub-layer of an oxide of the second metal.

13. The method of claim 10, wherein the adhesion layer is an alloy of the first metal and the second metal.

14. The method of claim 10, wherein forming the adhesion layer comprises annealing the first metal and the second metal to react to form an alloy of the first metal and the second metal.

15. The method of claim 10, wherein forming the adhesion layer comprises exposing the first metal to a natural environment.

16. The method of claim 10, wherein forming the adhesion layer comprises exposing the first metal to an oxygen-containing plasma.

17. A structure comprising:

a first source/drain region and a second source/drain region in a substrate;

a gate structure on the substrate and between the first source/drain region and the second source/drain region, the gate structure comprising;

a gate dielectric layer over the substrate,

a work function tuning layer over the gate dielectric layer,

a first metal over the work function tuning layer,

an adhesion layer over the first metal, and

a second metal over the adhesion layer, the second metal being different from the first metal; and

an inter-layer dielectric over the substrate and around the gate structure.

18. The structure of claim 17, wherein the adhesion layer comprises an oxide of the first metal.

19. The structure of claim 17, wherein the adhesion layer comprises an alloy of the first metal and the second metal.

20. The structure of claim 17 further comprising:

a buffer layer over the gate structure, the buffer layer comprising an oxide of the second metal; and

a dielectric cap over the buffer layer, a top surface of the dielectric cap being co-planar with a top surface of the inter-layer dielectric.