Methods of forming silicon nitride spacers

• US 9,257,293 B2
• Filed: 03/12/2014
• Issued: 02/09/2016
• Est. Priority Date: 03/14/2013
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Posseme, Nicolas, Joubert, Olivier, Lill, Thorsten, David, Thibaut
• Primary Examiner(s): GHYKA, ALEXANDER G
• Application Number:
  US14/205,673
• Publication Number:
  US 20140273292A1
• Time in Patent Office: 699 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H01L 21/3065 Plasma etching; Reactive-ion etching
• CPC Class Codes: H01L 21/3105 After-treatment
• CPC Class Codes: H01L 21/31111 by chemical means
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 29/66575 where the source and drain or source and drain extensions are self-aligned to the sides of the gate H01L29/66606 takes precedence
• CPC Class Codes: H01L 29/66628 recessing the gate by forming single crystalline semiconductor material at the source or drain location
• CPC Class Codes: H01L 29/7834 with a non-planar structure, e.g. the gate or the source or the drain being non-planar

Abstract

Embodiments of methods of forming silicon nitride spacers are provided herein. In some embodiments, a method of forming silicon nitride spacers atop a substrate includes: depositing a silicon nitride layer atop an exposed silicon containing layer and an at least partially formed gate stack disposed atop a substrate; modifying a portion of the silicon nitride layer by exposing the silicon nitride layer to a hydrogen or helium containing plasma that is substantially free of fluorine; and removing the modified portion of the silicon nitride layer by performing a wet cleaning process to form the silicon nitride spacers, wherein the wet cleaning process removes the modified portion of the silicon nitride layer selectively to the silicon containing layer.

Claims

1. A method of forming silicon nitride spacers atop a substrate, comprising:

depositing a silicon nitride layer atop an exposed silicon containing layer and an at least partially formed gate stack disposed atop a substrate;

modifying a portion of the silicon nitride layer by exposing the silicon nitride layer to a hydrogen or helium containing plasma that is substantially free of fluorine; and

removing the modified portion of the silicon nitride layer by performing a wet cleaning process to form the silicon nitride spacers, wherein the wet cleaning process removes the modified portion of the silicon nitride layer selectively to the silicon containing layer.

2. The method of claim 1, further comprising:

partially etching the silicon nitride layer by exposing the silicon nitride layer to a fluorine containing plasma.

3. The method of claim 1, wherein the silicon nitride layer is modified to a depth of about 1 to about 2 nm atop a sidewall of the at least partially formed gate stack and to a depth of about 2 to about 8 nm atop the exposed silicon containing layer.

4. The method of claim 1, further comprising:

subsequent to removing the modified portion of the silicon nitride layer, repeatedly modifying a portion of the silicon nitride layer by exposing the silicon nitride layer to a hydrogen or helium containing plasma that is substantially free of fluorine and subsequently removing the modified portion of the silicon nitride layer by performing a wet cleaning process until the silicon nitride spacers having desired dimensions are formed.

5. The method of claim 1, wherein the silicon nitride spacers are formed to a thickness of at least 3 nm.

6. The method of claim 1, wherein the wet cleaning process comprises exposing the modified portion of the silicon nitride layer to an aqueous solution containing hydrofluoric (HF) acid or phosphoric (H₃PO₄) acid.

7. The method of claim 1, wherein the hydrogen or helium containing plasma is formed from a process gas comprising one of helium (He) gas, hydrogen (H₂) gas, ammonia (NH₃), or methane (CH₄).

8. The method of claim 1, wherein a depth of the portion of the silicon nitride layer modified by the hydrogen or helium containing plasma is controlled by adjusting at least one of an amount of power coupled to the plasma, a pressure maintained in a process chamber utilized to perform the modification of the silicon nitride layer or a temperature of the substrate.

9. The method of claim 1, further comprising:

subsequent to removing the modified portion of the silicon nitride layer, performing an implantation process to implant an arsenic (As) containing material or a phosphorous (P) containing material in the exposed silicon containing layer to form a n-type MOSFET device or to implant a boron difluoride (BF₂) in the exposed silicon containing layer to form a p-type MOSFET device.

10. The method of claim 1, further comprising:

subsequent to removing the modified portion of the silicon nitride layer forming an epitaxial layer atop the silicon containing layer.

11. The method of claim 1, wherein the exposed silicon containing layer comprises one of crystalline silicon (Si) or crystalline silicon oxide (SiO₂).

12. A method of forming silicon nitride spacers atop a substrate, comprising:

depositing a silicon nitride layer atop an exposed silicon containing layer and an at least partially formed gate stack disposed atop a substrate;

modifying a portion of the silicon nitride layer by exposing the silicon nitride layer to a hydrogen or helium containing plasma that is substantially free of fluorine, wherein a depth of the portion of the silicon nitride layer modified by the hydrogen or helium containing plasma is controlled by adjusting at least one of an amount of power coupled to the plasma, a pressure maintained in a process chamber utilized to perform the modification of the silicon nitride layer or a temperature of the substrate; and

removing the modified portion of the silicon nitride layer by exposing the modified portion of the silicon nitride layer to an aqueous solution containing hydrofluoric (HF) acid or phosphoric (H₃PO₄) acid to form the silicon nitride spacers, wherein the aqueous solution removes the modified portion of the silicon nitride layer selectively to the silicon containing layer.

13. A computer readable medium having instructions stored thereon that, when executed, cause a method of forming silicon nitride spacers atop a substrate to be performed in a process chamber, the method comprising:

depositing a silicon nitride layer atop an exposed silicon containing layer and an at least partially formed gate stack disposed atop a substrate;

modifying a portion of the silicon nitride layer by exposing the silicon nitride layer to a hydrogen or helium containing plasma that is substantially free of fluorine; and

removing the modified portion of the silicon nitride layer by performing a wet cleaning process to form the silicon nitride spacers, wherein the wet cleaning process removes the modified portion of the silicon nitride layer selectively to the silicon containing layer.

14. The computer readable medium of claim 13, further comprising:

partially etching the silicon nitride layer by exposing the silicon nitride layer to a fluorine containing plasma.

15. The computer readable medium of claim 13, wherein the silicon nitride layer is modified to a depth of about 1 to about 2 nm atop a sidewall of the at least partially formed gate stack and to a depth of about 2 to about 8 nm atop the exposed silicon containing layer.

16. The computer readable medium of claim 13, further comprising:

subsequent to removing the modified portion of the silicon nitride layer, repeatedly modifying a portion of the silicon nitride layer by exposing the silicon nitride layer to a hydrogen or helium containing plasma that is substantially free of fluorine and subsequently removing the modified portion of the silicon nitride layer by performing a wet cleaning process until the silicon nitride spacers having desired dimensions are formed.

17. The computer readable medium of claim 13, wherein the silicon nitride spacers are formed to a thickness of at least 3 nm.

18. The computer readable medium of claim 13, wherein the wet cleaning process comprises exposing the modified portion of the silicon nitride layer to an aqueous solution containing hydrofluoric (HF) acid or phosphoric (H₃PO₄) acid.

19. The computer readable medium of claim 13, wherein the hydrogen or helium containing plasma is formed from a process gas comprising one of helium (He) gas, hydrogen (H₂) gas, ammonia (NH₃), or methane (CH₄).

20. The computer readable medium of claim 13, wherein a depth of the portion of the silicon nitride layer modified by the hydrogen or helium containing plasma is controlled by adjusting at least one of an amount of power coupled to the plasma, a pressure maintained in a process chamber utilized to perform the modification of the silicon nitride layer or a temperature of the substrate.