Method of forming self-aligned contact structure with locally etched gate conductive layer

• US 6,855,610 B2
• Filed: 12/27/2002
• Issued: 02/15/2005
• Est. Priority Date: 09/18/2002
• Status: Active Grant

• Current Assignee: ProMOS Technologies, Inc.
• Original Assignee: ProMOS Technologies, Inc.
• Inventors: Tung, Ming-Sheng, Lee, Yueh-Chuan
• Primary Examiner(s): CLARK, SHEILA V
• Application Number:
  US10/330,522
• Publication Number:
  US 20040051183A1
• Time in Patent Office: 781 Days
• Field of Search: 438/157, 438/230, 438/229, 438/303, 438/299, 438/696, 438/720, 438/72, 438/686
• US Class Current: 438/299
• 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
• CPC Class Codes: H01L 23/485 consisting of layered constructions comprising conductive layers and insulating layers, e.g. planar contacts H01L23/4821, H01L23/4822, H01L23/4824, H01L23/4825 take precedence; materials H01L23/532, bond pads H01L24/02, bump connectors H01L24/10
• CPC Class Codes: H01L 29/66659 with asymmetry in the channel direction, e.g. lateral high-voltage MISFETs with drain offset region, extended drain MISFETs
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A method of forming a self-aligned contact structure with a locally etched conductive layer comprises the steps of: preparing a substrate formed with gate structures comprising a first conductive layer, a second conductive layer, and an insulating layer; depositing a photoresist material layer on the substrate; performing a lithographic step with a bit-line contact node photomask or a bit-line contact photomask to expose a portion of the surface of the substrate; etching the exposed second conductive layer with an etchant; removing the remaining photoresist material layer; forming a sidewall spacer on the sidewalls of each gate structure; forming a dielectric layer to cover the substrate; and performing lithographic and etching steps to remove the dielectric layer and to form self-aligned contact structure.

Claims

1. A method of forming a gate structure with a locally etched conductive layer, comprising the steps of:

(a) preparing a semiconductor substrate, the substrate having a plurality of separated gate structures formed thereon, wherein each of the gate structures comprises a first conductive layer formed on the substrate, a second conductive layer formed on the first conductive layer and an insulating layer formed on the second conductive layer;

(b) using a photomask to form a covering layer that has at least an opening so as to expose parts of gate structures until the top surface of the substrate is exposed;

(c) using an etchant that has a higher etching rate to the second conductive layer than to the insulating layer and the first conductive layer to etch the second conductive layer of the exposed gate structures;

(d) removing the covering layer; and

(e) forming a sidewall spacer on each side of each gate structure.

2. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the step of forming the covering layer in step (b) comprises the steps of:

(i) depositing a photoresist material layer on the substrate; and

(ii) performing a lithographic process.

3. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the step of forming the covering layer in step (b) comprises the steps of:

(i) depositing an anti-reflective layer and a photoresist material layer on the substrate; and

(ii) performing a lithographic process and an etching process.

4. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the photomask of step (b) is a bit-line contact node photomask.

5. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the photomask in step (b) is a bit-line contact photomask.

6. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the first conductive layer is selected from the group consisting of polysilicon and amorphous silicon.

7. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the second conductive layer is a metal silicide layer.

8. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the etching process of step (c) is an isotropic etching process.

9. The method of forming a gate structure with a locally etched conductive layer of claim 1, wherein the etchant of step (c) is a mixture of NH₄OH, H₂O₂, and H₂O.

10. A method of forming a self-aligned contact with a locally etched conductive layer, comprising the steps of:

(a) preparing a semiconductor substrate, the substrate having a plurality of separated gate structures formed thereon, wherein each of the gate structures comprises a first conductive layer formed on the substrate, a second conductive layer formed on the first conductive layer, and an insulating layer formed on the second conductive layer;

(b) using a bit-line contact node photomask at the side of each gate structure used to form a bit-line contact to form a covering layer, which has at least an opening so as to expose parts of the gate structures until the top surface of the substrate is exposed;

(c) using an etchant that has a higher etching rate to the second conductive layer than to the insulating layer and the first conductive layer to etch the second conductive layer of the exposed side of each gate structure;

(d) removing the covering layer;

(e) forming a sidewall spacer on each side of each gate structure;

(f) forming a dielectric layer that covers the substrate;

(g) performing a lithographic process and an etching process to remove the dielectric layer of the side of each gate structure used to form the bit-line contact until the top surface of the substrate is exposed so as to from a self-aligned contact; and

(h) forming a metal layer that covers the etched surface of the dielectric layer and the sidewall spacers of the gate structures and forming a self-aligned contact between the metal layer and the top surface of the exposed substrate.

11. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the step of forming the covering layer in step (b) comprises the steps of:

(i) depositing a photoresist material layer on the substrate; and

(ii) performing a lithographic process.

12. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the step of forming the covering layer in step (b) comprises the steps of:

(i) depositing an anti-reflective layer and a photoresist material layer on the substrate; and

(ii) performing a lithographic process and an etching process.

13. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the first conductive layer is selected from the group consisting of polysilicon and amorphous silicon.

14. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the second conductive layer is a metal silicide layer.

15. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 14, wherein the metal silicide layer is a tungsten silicide layer.

16. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the insulating layer is a silicon nitride layer.

17. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the sidewall spacer is a silicon nitride layer.

18. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the etching process of step (c) is an isotropic etching process.

19. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 10, wherein the etchant of step (c) is a mixture of NH₄OH, H₂O₂, and H₂O.

20. A method of forming a self-aligned contact window with a locally etched conductive layer, comprising the steps of:

(a) preparing a semiconductor substrate, the substrate having a plurality of separated gate structures formed thereon, wherein each of gate structures comprises a first conductive layer formed on the substrate, a second conductive layer formed on the first conductive layer, and an insulating layer formed on the second conductive layer;

(b) using a bit-line node photomask on the gate structures to form a covering layer that has at least a round opening so as to expose parts of the gate structures until the surface of the substrate is exposed, wherein the opening is the region used to form self-aligned contact windows;

(c) using an etchant that has a higher etching rate to the second conductive layer than to the insulating layer and the first conductive layer to etch the second conductive layer of the exposed side of each gate structure;

(d) removing the covering layer;

(e) forming a sidewall spacer at each side of each gate structure;

(f) forming a dielectric layer that covers the substrate;

(g) performing a lithographic process and an etching process to remove the dielectric layer of the side of each gate structure used to form the bit-line contact until the top surface of the substrate is exposed so as to from a self-aligned contact window; and

(h) forming a metal layer that covers the etched surface of the dielectric layer and the sidewall spacers of the gate structures and forming a self-aligned contact between the metal layer and the top surface of the exposed substrate.

21. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the step of forming the covering layer in step (b) comprises the steps of:

(i) depositing a photoresist material layer on the substrate; and

(ii) performing a lithographic process.

22. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the step of forming the covering layer in step (b) comprises the steps of:

(i) depositing an anti-reflective layer and a photoresist material layer on the substrate; and

(ii) performing a lithographic process and an etching process.

23. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the first conductive layer is selected from the group consisting of polysilicon and amorphous silicon.

24. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the second conductive layer is a metal silicide layer.

25. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 24, wherein the metal silicide layer is a tungsten silicide layer.

26. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the insulating layer is a silicon nitride layer.

27. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the sidewall spacer is a silicon nitride layer.

28. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the etching process of step (c) is an isotropic etching process.

29. The method of forming a self-aligned contact structure with a locally etched conductive layer of claim 20, wherein the etchant of step (c) is a mixture of NH₄OH, H₂O₂, and H₂O.