Method for selective trimming of gate structures and apparatus formed thereby

• US 6,815,737 B2
• Filed: 03/12/2004
• Issued: 11/09/2004
• Est. Priority Date: 01/04/1999
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hakey, Mark C., Furukawa, Toshiharu, Horak, David V., Holmes, Steven J., Rabidoux, Paul A.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): HOANG, QUOC DINH
• Application Number:
  US10/799,819
• Publication Number:
  US 20040180484A1
• Time in Patent Office: 242 Days
• Field of Search: 257/204, 257/351, 438/199
• US Class Current: 257/204
• CPC Class Codes: H01L 21/76888 By rendering at least a portion of the conductor non conductive, e.g. oxidation
• CPC Class Codes: H01L 21/76895 Local interconnects; Local pads, as exemplified by patent document EP0896365
• CPC Class Codes: H01L 21/76897 Formation of self-aligned vias or contact plugs, i.e. involving a lithographically uncritical step self-aligned silicidation on field effect transistors H01L29/665

Abstract

A method for forming a trimmed gate in a transistor comprises the steps of forming a polysilicon gate conductor on a semiconductor substrate and trimming the polysilicon portion by a film growth method chosen from among selective surface oxidation and selective surface nitridation. The trimming step may selectively compensate n-channel and p-channel devices. Also, the trimming film may optionally be removed by a method chosen from among anisotropic and isotropic etching. Further, gate conductor spacers may be formed by anisotropic etching of the grown film. The resulting transistor may comprise a trimmed polysilicon portion of a gate conductor, wherein the trimming occurred by a film growth method chosen from among selective surface oxidation and selective surface nitridation.

Claims

1. An electrical structure, comprising:

a semiconductor substrate having an electrically insulative isolation structure therein, wherein a top surface of the substrate and a top surface of the isolation structure are coplanar;

a first gate oxide layer on the substrate and in direct mechanical contact with the top surface of the substrate;

a first polysilicon layer on the first gate oxide layer and in direct mechanical contact with the first gate oxide layer;

a second gate oxide layer on the isolation structure and in direct mechanical contact with the top surface or the isolation structure, wherein the first and second gate oxide layers have a same thickness in a first direction perpendicular to the top surface of the substrate, and wherein the first gate oxide layer has a smaller width than the second gate oxide layer in a second direction parallel to the top surface of the substrate; and

a second polysilicon layer on the second gate oxide layer and in direct mechanical contact with the second gate oxide layer, wherein the first polysilicon layer has a smaller thickness than the second polysilicon layer in the first direction, and wherein the first polysilicon layer has a smaller width than the second polysilicon layer in the second direction.

2. The electrical structure of claim 1, further comprising a first dielectric film surrounding and in direct mechanical contact with the first gate oxide layer and the first polysilicon layer and in direct mechanical contact with the top surface of the substrate, wherein a combined thickness of the first polysilicon layer and the first dielectric film in the first direction exceeds the thickness of the second polysilicon layer in the first direction, and wherein a combined width of the first polysilicon layer and the first dielectric film in the second direction exceeds the width of the second polysilicon layer in the second direction.

3. The electrical structure of claim 2, further comprising a second dielectric film surrounding and in direct mechanical contact with the first dielectric film and in direct mechanical contact with the top surface of the substrate.

4. The electrical structure of claim 3, further comprising a diffusion area in the substrate, wherein the top surface of the substrate and a top surface of the diffusion area are coplanar, and wherein the top surface of the diffusion area is in direct mechanical contact with the first gate oxide layer, the first dielectric film, and the second dielectric film.

5. The electrical structure of claim 2, wherein the first dielectric film comprises silicon oxide.

6. The electrical structure of claim 2, wherein the first dielectric film comprises silicon nitride.

7. The electrical structure of claim 1, further comprising a dielectric cap layer on the first polysilicon layer and in direct mechanical contact with a top surface of the first polysilicon layer, and wherein the top surface of the first polysilicon layer is about parallel to the top surface of the substrate.

8. The electrical structure of claim 7, further comprising an electrically insulative spacer in direct mechanical contact with the first gate oxide layer, the first polysilicon layer, and a side surface of the dielectric cap layer, and whereon a portion of the side surface of the dielectric cap layer is not in mechanical contact with the spacer.

9. The electrical structure of claim 8, further comprising a diffusion area in the substrate, wherein the top surface of the substrate and a top surface of the diffusion area are coplanar, and wherein the top surface of the diffusion area is in direct mechanical contact with the first gate oxide layer and the spacer.

10. The electrical structure of claim 7, wherein the dielectric cap layer comprises silicon oxide.

11. The electrical structure of claim 7, wherein the dielectric cap layer comprises silicon nitride.

12. The electrical structure of claim 7, wherein the spacer comprises a silicon-rich material.

13. The electrical structure of claim 12, wherein the silicon-rich material comprises silicon-rich silicon nitride.

14. The electrical structure of claim 12, wherein the silicon-rich material comprises silicon-rich silicon oxynitride.

15. The electrical structure of claim 1, wherein the substrate comprises single crystal silicon.

16. The electrical structure of claim 1, wherein the thickness of the first gate oxide in the first direction is 3 to 5 nanometers.

17. A structure comprising:

a semiconductor substrate;

a first gate oxide layer on the substrate and in direct mechanical contact with the top surface of the substrate;

a first polysilicon layer on the first gate oxide layer and in direct mechanical contact with the first gate oxide layer;

an electrically insulative isolation structure within the substrate, wherein the top surface of the substrate and a top surface of the insulation structure are coplanar;

a second gate oxide layer on the isolation structure and in direct mechanical contact with the top surface of the isolation structure; and

a second polysilicon layer on the second gate oxide layer and in direct mechanical contact with the second gate oxide layer, wherein the first polysilicon layer has a smaller thickness than the second polysilicon layer in a first direction perpendicular to the top surface of the substrate, and wherein the first polysilicon layer has a smaller width than the second polysilicon layer in a second direction parallel to the top surface of the substrate.