Method for plasma etching tungsten

• US 4,838,990 A
• Filed: 07/16/1987
• Issued: 06/13/1989
• Est. Priority Date: 07/16/1987
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Davis, Cecil J., Jucha, Rhett B., Jones, John I.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US07/074,450
• Time in Patent Office: 698 Days
• Field of Search: 156/643, 156/646, 156/651, 156/656, 156/657, 156/659.1, 156/662, 156/345, 252/79.1, 437/228, 437/234, 437/235, 437/238, 437/241, 437/245, 414/217, 414/222, 414/225, 414/226, 414/744 R, 414/744 A, 414/744 B, 414/744 C, 414/411, 414/416, 414/422, 204/192.1, 204/192.12, 204/192.23, 204/192.25, 204/192.32, 204/192.35, 204/192.36, 204/192.37, 204/298, 427/38, 427/39, 427/41, 427/54.1, 118/728, 118/729, 118/50.1, 118/620
• US Class Current: 438/711
• CPC Class Codes: C23C 16/517 using a combination of discharges covered by two or more of groups C23C16/503 - C23C16/515
• CPC Class Codes: C23F 4/00 Processes for removing metallic material from surfaces, not provided for in group C23F1/00 or C23F3/00
• CPC Class Codes: H01J 2237/022 Avoiding or removing foreign or contaminating particles, debris or deposits on sample or tube
• CPC Class Codes: H01J 2237/184 Vacuum locks
• CPC Class Codes: H01J 2237/3345 anisotropy
• CPC Class Codes: H01J 37/32339 using electromagnetic radiation
• CPC Class Codes: H01J 37/32743 for introducing the material into processing chamber
• CPC Class Codes: H01J 37/32788 for extracting the material from the process chamber
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/67069 for drying etching
• CPC Class Codes: H01L 21/67115 mainly by radiation
• CPC Class Codes: H01L 21/67748 horizontal transfer of a single workpiece
• CPC Class Codes: H01L 21/67751 vertical transfer of a single workpiece

Abstract

A process wherein a thin film metal (e.g. tungsten) is anisotropically etched under plasma bombardment conditions by using a feed gas mixture which includes a fluorine source (such as SF₆) plus a fluorosilane (e.g. SiF₄), plus a bromine source (such as HBr), plus a weak oxygen source such as carbon monoxide. This chemistry provides anisotropic high rate fluoro-etching with good selectivity to photoresist.

Claims

1. A method for etching Tungsten on a wafer comprising:

(a) transferring a wafer into a vacuum processing chamber;

(b) applying a pressure to said chamber less than ambient to maintain said chamber at less than ambient;

(c) providing fluorine containing gas to a remote plasma chamber separated from said chamber and producing a remote plasma;

(d) adding a very weak oxygen source gas to said remote plasma chamber;

(e) adding a bromine containing gas and a resist selectivity enhancement has to said remote plasma chamber;

(f) applying a radio frequency signal across two electrodes one of which is adjacent to the wafer and causing a plasma to be formed whose dark space is in the vicinity of the surface of the slice; and

(g) flowing the gas mixture over said wafer disposed within said chamber.

4. The process as set forth in claim 1 wherein the steps of generating free radicals and an in situ plasma are controlled singly.

5. The process as set forth in claim 1 wherein the steps of generating free radicals and an in situ plasma are controlled in combination with each other.

2. A method for etching tungsten on a wafer comprising:

(a) disposing said wafer into a process chamber at low pressure;

(b) generating a remote plasma form a source of fluorine, a weak source of oxygen, and a source of bromide;

(c) introducing said remote plasma into said chamber to a face of said wafer; and

(d) generating an in situ plasma within said chamber.

3. The process as set forth in claim 2 wherein said step of generating said remote plasma includes a fluorosilane.

6. The process as set forth in claim 2 wherein the steps of generating free radicals and an in situ plasma are controlled singly.

7. The process as set forth in claim 2 wherein the steps of generating free radicals and an in situ plasma are controlled in combination with each other.

8. A method for etching Tungsten on a wafer in a process chamber, comprising the steps of:

(a) generating free radicals from a fluorine containing gas, very weak oxygen source, a bromine containing gas and a resist selectivity enhancement gas to plasma generator remote from the process chamber;

(b) introducing the free radicals to the process chamber and to a face of the wafer to be porocessed; and

(c) generating an in situ plasma from the free radicals in the process chamber.

9. The process as set forth in claim 8 wherein the steps of generating free radicals and an in situ plasma are controlled singly.

10. The process as set forth in claim 8 wherein the steps of generating free radicals and an in situ plasma are controlled in combination with each other.

11. The process as set forth in claim 8 wherein the fluorine containing gas is fluorosilane.