Etchant and method of use

• US 20040248413A1
• Filed: 07/09/2004
• Published: 12/09/2004
• Est. Priority Date: 04/27/2000
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Donohoe, Kevin G., Becker, David S.
• Granted Patent: US 7,074,724 B2
• Time in Patent Office: Days
• US Class Current: 438/689
• CPC Class Codes: C09K 13/08 containing a fluorine compound
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• 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 anisotropiocally etching a semiconductive substrate uses a hydrofluorocarbon etch gas with an etch selectivity fluorocarbon gas. The fluorocarbon gas is used under conditions that enhance selectivity of the etch to an etch stop layer with respect to a bulk dielectric material such as doped or undoped silicon dioxide. In one method, a silicon dioxide dielectric layer is provided upon an etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric layer. A gaseous etchant including a hydrofluorocarbon etch gas and a fluorocarbon selectivity compound is provided, and the silicon dioxide dielectric layer is exposed to the gaseous etchant.

Claims

1. A method of removing silicon dioxide upon an etch stop layer, the method comprising:

providing a silicon dioxide dielectric layer upon an etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric layer;

providing a gaseous etchant including a hydrofluorocarbon etch gas and a fluorocarbon selectivity compound; and

exposing the silicon dioxide dielectric layer to the gaseous etchant.

2. The method of claim 1, wherein the selectivity compound is selected from the group consisting of CF₄, C₂F₆, C₄F₈, C₅F₆, C₅F₈, and combinations thereof.

3. The method of claim 1, wherein the hydrofluorocarbon is provided in a first quantity, the fluorocarbon is provided in a second quantity, and the first quantity is at least twice the second quantity.

4. The method of claim 1, wherein exposing the silicon dioxide dielectric layer is performed in an etch chamber having a roof comprising silicon and having a temperature in a range from about 100°

C. to about 200°

C.

5. The method of claim 1, wherein etching of the silicon dioxide dielectric layer in the gaseous etchant is carried out until the etch stop layer is exposed.

6. The method of claim 1, wherein the selectivity compound is in a range from about less than one part to about 15 parts, and the hydrofluorocarbon comprises CHF₃ in a range from about 30 parts to about 50 parts.

7. The method of claim 1, wherein the selectivity compound is in a range from about 0.5 parts to about 4 parts, and the hydrofluorocarbon comprises CHF₃ in a range from about 44 parts to about 45 parts.

8. A method of removing a silicon dioxide dielectric upon an etch stop layer that is situated upon a semiconductive substrate positioned within an etch chamber, the method comprising:

etching the silicon dioxide dielectric to a first depth with a first etch recipe including a hydrofluorocarbon, the first etch recipe having a first selectivity to the etch stop layer;

etching the silicon dioxide dielectric to a second depth with a second etch recipe including the hydrofluorocarbon and a selectivity compound comprising a fluorocarbon, the second etch recipe having a second selectivity to the etch stop layer, wherein the first selectivity is greater than the second selectivity; and

stopping the second etching upon the etch stop layer, wherein the etch stop layer comprises silicon dioxide that is doped differently from the silicon dioxide dielectric.

9. The method of claim 8, wherein the selectivity compound is selected from the group consisting of CF₄, C₂F₆, C₄F₈, C₅F₆, C₅F₈, and combinations thereof.

10. The method of claim 8, wherein the etch chamber has a roof comprised of silicon and is at a temperature in a range from about 100°

C. to about 200°

C. while etching the silicon dioxide dielectric to the first and second depths.

11. The method of claim 8, wherein the first etch recipe comprises CH₂F₂, CH₃F, or mixtures thereof.

12. The method of claim 8, wherein the selectivity compound is in a range from about less than one part to about 15 parts, and the hydrofluorocarbon is in a range from about 30 parts to about 50 parts.

13. The method of claim 8, wherein the selectivity compound is in a range from about 0.5 parts to about 4 parts, and the hydrofluorocarbon is in a range from about 44 parts to about 45 parts.

14. The method of claim 8, wherein:

the etch stop layer is a spacer on each gate stack in a pair of adjacent, spaced apart gate stacks situated over the semiconductive substrate;

the silicon dioxide dielectric is formed over and between the gate stacks; and

etching the silicon dioxide dielectric to the first and second depths forms a contact hole between the pair of gate stacks without etching the spacer.

15. The method of claim 14, wherein the contact hole is a self-aligned contact hole with respect to the pair of gate stacks.

16. The method of claim 14, wherein the contact hole has an aspect ratio of at least about 5:

1.

17. A method of determining a specific etch recipe for etching silicon dioxide with predetermined selectivity to an etch stop layer underlying the silicon dioxide, the method comprising:

etching silicon dioxide with a gaseous etchant including a hydrofluorocarbon and a selectivity gas comprising carbon and fluorine to obtain a selectivity to the etch stop layer, wherein the etch stop layer comprises an oxide that is compositionally different from the silicon dioxide;

repeating the etching with different amounts of the selectivity gas to correspondingly obtain different selectivities to the etch stop layer;

selecting an amount of the different amounts of the selectivity gas corresponding to a desired etch selectivity to the etch stop layer; and

etching silicon dioxide with a gaseous etchant including the hydrofluorocarbon and the selected amount of the selectivity gas to obtain the desired selectivity to the etch stop layer.

18. The method of claim 17, wherein the selectivity gas is selected from the group consisting of CF₄, C₂F₆, C₄F₈, C₅F₆, C₅F₈, and combinations thereof.

19. The method of claim 17, wherein:

the etch stop layer is a spacer on each gate stack in a pair of separated gate stacks situated over the semiconductor substrate;

the silicon dioxide is formed over and between the gate stacks; and

each of the etching steps forms a contact hole between the pair of gate stacks without etching the spacer.

20. The method of claim 19, wherein the contact hole has an aspect ratio of at least about 5:

1.