Fabrication method of a self-aligned contact window

• US 6,245,625 B1
• Filed: 06/19/1999
• Issued: 06/12/2001
• Est. Priority Date: 06/19/1999
• Status: Expired due to Fees

• Current Assignee: United Microelectronics Corporation
• Original Assignee: United Microelectronics Corporation
• Inventors: Gau, Jing-Horng
• Primary Examiner(s): Fourson, George
• Assistant Examiner(s): GARCIA, JOANNIE A
• Application Number:
  US09/336,553
• Time in Patent Office: 724 Days
• Field of Search: 438/639, 438/595, 438/FOR.199, 438/FOR.355, 438/FOR.196, 438/305, 438/FOR.188
• US Class Current: 438/305
• 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 of fabricating a self-aligned contact window structure is described in which a substrate is provided with a plurality of gates formed on the substrate and a plurality of lightly doped regions is formed in the substrate on both sides of the gate. A first dielectric layer of a certain thickness is then formed on the substrate with the surface of the first dielectric layer being lower than the surfaces of the gates such that the sidewalls of the gates are partially exposed. A plurality of spacers is further formed on the exposed sidewalls of the gates. Using the gates and the spacers as masks, the first dielectric layer is anisotropically etched until the lightly doped regions are partially exposed. Using the gate and the spacer as masks, a plurality of heavily doped regions is formed in the lightly doped region and in the substrate. A second dielectric layer is formed covering the gates. The second dielectric is then defined to form a self-aligned contact window.

Claims

1. A fabrication method of a self-aligned contact window, comprising the steps of:

providing a semiconductor substrate with a plurality of gates formed on the substrate and a plurality of lightly doped regions formed in the substrate on both sides of the gates, wherein the gates comprise a gate oxide layer, a doped polysilicon layer, a metal silicide layer, and a roof layer;

forming a first dielectric layer with a certain thickness on the substrate, such that the upper surface of the first dielectric layer is lower than the upper surfaces of the gates and fully exposing the roof layers of the gates;

forming a plurality of spacers on the exposed sidewalls of the gates;

conducting an anisotropic etching on the first dielectric layer until a portion of the lightly doped region is exposed, with the gates and the spacers serving as masks;

forming a plurality of heavily doped regions in the lightly doped region and in the substrate, with the gates and the spacers serving as masks;

forming a second dielectric layer covering the gates; and

defining the second dielectric layer to form a self-aligned contact window.

2. The fabrication method of a self-aligned contact window according to claim 1, wherein the first dielectric layer is approximately 300-500 Å

thick.

3. The fabrication method of a self-aligned contact window according to claim 1, wherein a method of forming the first dielectric layer comprises the steps of:

forming a planarized third dielectric layer on the substrate to cover the gates; and

removing the third dielectric layer until its remaining thickness is same as that of the first dielectric layer.

4. The fabrication method of a self-aligned contact window according to claim 3, wherein the third dielectric layer is partially removed by a process such as wet etching.

5. The fabrication method of a self-aligned contact window according to claim 3, wherein the third dielectric layer is planarized by a process including chemical mechanical polishing.

6. The fabrication method of a self-aligned contact window according to claim 3, wherein the third dielectric layer includes silicon oxide.

7. The fabrication method of a self-aligned contact window according to claim 3, wherein the first dielectric layer is approximately 300-500 Å

thick.

8. The fabrication method of a self-aligned contact window according to claim 1, wherein the first dielectric layer includes silicon oxide.

9. The fabrication method of a self-aligned contact window according to claim 1, wherein the spacer includes silicon nitride.

10. The fabrication method of a self-aligned contact window according to claim 9, wherein forming the spacer further comprises the steps of:

forming a silicon nitride layer on the substrate; and

etching back the silicon nitride layer to form the spacers on the sidewalls of the gates.

11. The fabrication method for a self-aligned contact window according to claim 1. wherein fabricating the self-aligned contact window further includes forming a bit line on the second dielectric layer and in the self-aligned contact window.

12. The fabrication method of a self-aligned contact window according to claim 1, wherein the bit line includes a polysilicon layer and a metal silicide layer.

13. The fabrication method of a self-aligned contact window according to claim 1, wherein the roof layer includes silicon nitride.

14. A fabrication method of a self-aligned contact window, comprising the steps of:

providing a substrate with a gate formed on the substrate, wherein the gate comprises at least a roof layer;

forming a planarized first dielectric layer on the substrate covering the gate;

removing a portion of the planarized first dielectric layer until a surface of a remaining planarized first dielectric layer is lower than a surface of the gate and exposes the roof layer of the gate;

forming a spacer on an exposed sidewall of the gate;

defining the remaining planarized first dielectric layer until the substrate is partially exposed, with the gate and the spacer serving as masks;

forming a second dielectric layer to cover the gate; and

defining the second dielectric layer to form a self-aligned contact window.

15. The fabrication method of a self-aligned contact window of claim 14, wherein the remaining planarized first dielectric layer is approximately 300-500 Å

thick.

16. The fabrication method of a self-aligned contact window according to claim 14, wherein the portion of the planarized first dielectric layer is removed by a wet etching process.

17. The fabrication method of a self-aligned contact window according to claim 14, wherein the spacer includes silicon nitride.