T or T/Y gate formation using trim etch processing

• US 6,403,456 B1
• Filed: 08/22/2000
• Issued: 06/11/2002
• Est. Priority Date: 08/22/2000
• Status: Expired due to Term

• Current Assignee: Globalfoundries US Incorporated (GlobalFoundries, Inc.)
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Subramanian, Ramkumar, Singh, Bhanwar, Lyons, Christopher F., Plat, Marina
• Primary Examiner(s): Smith, Mathew S.
• Assistant Examiner(s): MALSAWMA, LALRINFAMKIM HMAR
• Application Number:
  US09/643,611
• Time in Patent Office: 658 Days
• Field of Search: 438/167, 438/182, 438/573, 438/574, 438/576, 438/578, 438/579, 438/666
• US Class Current: 438/579
• CPC Class Codes: H01L 21/28114 characterised by the sectional shape, e.g. T, inverted-T
• CPC Class Codes: H01L 21/28123 Lithography-related aspects, e.g. sub-lithography lengths; Isolation-related aspects, e.g. to solve problems arising at the crossing with the side of the device isolation; Planarisation aspects
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• CPC Class Codes: H01L 29/42376 characterised by the length or the sectional shape

Abstract

A method for fabricating a T-gate structure is provided. The method comprises the steps of providing a silicon layer having a gate oxide layer, a protection layer over the gate oxide layer, a first sacrificial layer over the protection layer and a second sacrificial layer over the first sacrificial layer. A photoresist layer is formed over the second sacrificial layer. An opening is formed in the photoresist layer. An opening is then formed in the second sacrificial layer beneath the opening in the photoresist layer. The opening is then expanded in the photoresist layer to expose portions of the top surface of the second sacrificial layer around the opening in the second sacrificial layer. The opening is extended in the second sacrificial layer through the first sacrificial layer and the opening is expanded in the second sacrificial layer to form a T-shaped opening in the first and second sacrificial layers. The photoresist layer is removed and the T-shaped opening is filled with a conductive material.

Claims

1. A method for fabricating a T-gate structure comprising the steps of:

providing a silicon layer having a gate oxide layer, a protection layer over the gate oxide layer, a first sacrificial layer over the protection layer and a second sacrificial layer over the first sacrificial layer;

forming a photoresist layer over the second sacrificial layer;

forming an opening in the photoresist layer;

forming an opening in the second sacrificial layer beneath the opening in the photoresist layer;

expanding the opening in the photoresist layer to expose portions of the top surface of the second sacrificial layer around the opening in the second sacrificial layer;

extending the opening of the second sacrificial layer through the first sacrificial layer and expanding the opening in the second sacrificial layer to form a T-shaped opening in the first and second sacrificial layers;

removing the photoresist layer; and

filling the T-shaped opening with a conductive material.

2. The method of claim 1, the first sacrificial layer and the second sacrificial layer including at least two of silicon oxide, silicon dioxide, silicon nitride (Si₃N₄), (SiN), silicon oxynitride, (SiO_xN_y), fluonated silicon oxide (SiO_xF_y), and polyimide(s) wherein the first sacrificial layer is formed from a different material than the second sacrificial layer.

3. The method of claim 1, the step of filling the T-shaped opening with a conductive material comprising the step of depositing one of polysilicon, germanium, amorphous polysilicon and metal in the T-shaped opening.

4. The method of claim 1, further comprising the step of removing the first and second sacrificial layers.

5. The method of claim 4, the step of removing the first and second sacrificial layers comprising stripping the first and second sacrificial layers employing an anisotropic gaseous stripping process.

6. The method of claim 5, further comprising the step of removing portions of the protection layer and the gate oxide layer not forming a part of the T-gate structure.

7. The method of claim 6, the step of removing portions of the protection layer and the gate oxide layer not forming a part of the T-gate structure comprising the step of performing an etch on the protection layer and the gate oxide layer.

8. The method of claim 7, the etch on the protection layer and the gate oxide layer being one of a wet etch and a vertical plasma etch.

9. The method of claim 5, further comprising the step of removing portions of the protection layer and the gate oxide layer not forming a part of the T-gate structure using one of a wet etch and a vertical plasma etch.

10. The method of claim 1, the step of forming an opening in the photoresist layer comprising performing a first resist etch on the photoresist layer that is highly selective to the photoresist layer over the underlying second sacrificial layer.

11. The method of claim 1, the step of forming an opening in the second sacrificial layer beneath the opening in the photoresist layer comprising the step of etching the second sacrificial layer with an etch that is highly selective to the second sacrificial layer over the photoresist layer and the underlying first sacrificial layer.

12. The method of claim 1, the step of expanding the opening in the photoresist layer comprising the step of etching the photoresist opening with an oxygen plasma etch.

13. The method of claim 1, the step of extending the opening of the second sacrificial layer through the first sacrificial layer and expanding the opening in the second sacrificial layer to form a T-shaped opening in the first and second sacrificial layers comprising the step of etching the opening in the second sacrificial layer with an etch that is highly selective to the first and second sacrificial layers over the photoresist layer and the underlying protection layer.

14. The method of claim 1, the protection layer being formed from one of polysilicon and germanium.

19. The method of claim 14, the step of expanding the opening in the photoresist layer comprising the step of etching the photoresist opening with an oxygen plasma etch.

15. A method for fabricating a T-gate structure comprising the steps of:

providing a silicon layer having a gate oxide layer, a protection layer over the gate oxide layer and a single sacrificial layer over the protection layer;

forming a photoresist layer over the single sacrificial layer;

etching an opening in the photoresist layer exposing a portion of the single sacrificial layer;

etching the exposed portion of the single sacrificial layer to extend the opening partially into the single sacrificial layer, the opening in the single sacrificial layer extending from a top surface of the single sacrificial layer to a first depth;

expanding the opening in the photoresist layer to expose portions of the top surface of the single sacrificial layer around the opening in the single sacrificial layer;

etching the opening in the expanded opening in the photoresist layer to extend the opening of the single sacrificial layer through the single sacrificial layer to the protection layer and expand the opening in the single sacrificial layer at the first depth to form a T-shaped opening in the single sacrificial layer;

removing the photoresist layer; and

filling the T-shaped opening with a conductive material.

16. The method of claim 15, the single sacrificial layer including at least one of silicon oxide, silicon dioxide, silicon nitride (Si₃N₄), (SiN), silicon oxynitride, (SiO_xN_y), fluonated silicon oxide (SiO_xF_y), and polyimide(s).

17. The method of claim 15, the step of filling the T-shaped opening with a conductive material comprising the step of depositing one of polysilicon, germanium, amorphous polysilicon and metal in the T-shaped opening.

18. The method of claim 15, further comprising the step of removing the single sacrificial layer employing an anisotropic gaseous stripping process.

20. A method for fabricating a T-gate structure comprising the steps of:

providing a silicon layer having a gate oxide layer, a protection layer over the gate oxide layer, a first sacrificial layer over the protection layer and a second sacrificial layer over the first sacrificial layer;

forming a photoresist layer over the second sacrificial layer;

etching an opening in the photoresist layer exposing a portion of the second sacrificial layer, the etching being highly selective to the photoresist layer over the underlying second sacrificial layer;

etching the exposed portion of the second sacrificial layer to extend the opening into the second sacrificial layer, the etching being highly selective to the second sacrificial layer over the photoresist layer and the underlying first sacrificial layer;

expanding the opening in the photoresist layer to expose portions of the top surface of the second sacrificial layer around the opening in the second sacrificial layer using an oxygen plasma etch;

etching the opening of the second sacrificial layer through the first sacrificial layer and expanding the opening in the second sacrificial layer to form a T-shaped opening in the first and second sacrificial layers, the etching being highly selective to the second sacrificial layer and the first sacrificial layer over the photoresist layer and the underlying protection layer;

removing the photoresist layer;

filling the T-shaped opening with a conductive material;

removing the first and second sacrificial layers employing an anisotropic gaseous stripping process; and

removing portions of the protection layer and the gate oxide layer not forming a part of the T-gate structure by performing an etch on the protection layer and the gate oxide layer using a wet etch.