Plasma processing of tungsten using a gas mixture comprising a fluorinated gas and oxygen

• US 6,277,763 B1
• Filed: 12/16/1999
• Issued: 08/21/2001
• Est. Priority Date: 12/16/1999
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Kugimiya, Katsuhisa, Tajima, Daisuke, Nishizawa, Takanori
• Primary Examiner(s): POWELL, WILLIAM A
• Application Number:
  US09/465,031
• Time in Patent Office: 614 Days
• Field of Search: 438/8, 438/9, 438/14, 438/710, 438/720, 438/727, 438/730, 438/740, 438/742, 156/345.P, 156/345.MT, 216/59, 216/60, 216/67, 216/75, 252/79.1
• US Class Current: 438/720
• 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 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01L 21/32136 using plasmas

Abstract

A method and apparatus for etching of a substrate comprising both a polysilicon layer and an overlying tungsten layer. The method comprises etching the tungsten layer in a chamber using a plasma formed from a gas mixture comprising a fluorinated gas (such as CF₄, NF₃, SF₆, and the like) and oxygen.

Claims

1. Apparatus for etching a substrate comprising:

a processing chamber having a gas inlet; and

a gas panel coupled to said gas inlet for supplying fluorinated gas at a rate of about 10 to about 200 sccm and oxygen at a rate of about 10 to about 200 sccm, said fluorinated gas and oxygen forming a plasma capable of etching a tungsten layer disposed on said substrate, and wherein said oxygen forms an oxide etch stop layer atop a polysilicon layer underlying said tungsten layer.

2. The apparatus of claim 1 wherein the fluorinated gas is selected from the group consisting of CF₄, NF₃ and SF₆.

3. The apparatus of claim 1 further comprising:

a first power source applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said chamber; and

a second power source applying bias power of about 10 to about 300 Watts to a pedestal having an embedded electrode disposed in said chamber.

4. The apparatus of claim 1 wherein the fluorinated gas and the oxygen are regulated to a chamber pressure of between about 0.5 and 100 mTorr.

5. A method for etching a substrate comprising a tungsten layer overlying polysilicon, said method comprising the steps of:

supplying a reactant gas comprising a fluorinated gas to a processing chamber;

supplying oxygen to said processing chamber;

forming a plasma in said chamber from said reactant gas.

6. The method of claim 5 wherein the fluorinated gas is selected from the group consisting of CF₄, NF₃ and SF₆.

7. The method of claim 5 where said fluorinated gas is supplied at a flow rate of about 10 to about 200 sccm.

8. The method of claim 5 wherein said oxygen is supplied at a flow rate of about 10 to about 200 sccm.

9. The method of claim 5 further comprising the step of reaching an endpoint at or near the breakthrough of said tungsten layer wherein said oxygen supplying step occurs after said endpoint is reached.

10. The method of claim 5 further comprising the steps of:

applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber; and

,

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber.

11. The method of claim 5 wherein the steps of supplying the fluorinated gas and oxygen further comprise the step of:

regulating said chamber pressure between about 0.5 to about 100 mTorr.

12. The method of claim 5 further comprising the step of:

performing a main-etch to substantially remove said tungsten layer.

13. The method of claim 12 wherein said main-etch further comprises:

supplying a fluorinated gas to a processing chamber at a flow rate of about 10 to about 200 sccm, said fluorinated gas selected from the group consisting of CF₄, NF₃ and SF₆;

regulating said chamber pressure between about 0.5 to about 100 mTorr;

applying inductive source power of about 10 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber;

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber; and

,

forming a plasma in said chamber from said fluorinated gas.

14. The method of claim 12 wherein said fluorinated gas is supplied at a flow rate of about 10 to about 200 sccm.

15. The method of claim 12 wherein the steps of supplying the fluorinated gas and oxygen further comprise the step of:

regulating said chamber pressure between about 0.5 to about 100 mTorr.

16. The method of claim 12 further comprising the steps of:

applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber; and

,

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber.

17. A method for etching a substrate comprising a tungsten layer overlying polysilicon, said method comprising the steps of:

performing a first etch process comprising the steps of;

supplying a first fluorinated gas to a processing chamber at a flow rate of about 10 to about 200 sccm, said first fluorinated gas selected from the group consisting of CF₄, NF₃ and SF₆;

regulating said processing chamber pressure between about 0.5 to about 100 mTorr;

applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber;

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber;

forming a first plasma in said chamber from said first fluorinated gas; and

,

performing a second etch comprising the steps of;

supplying a second fluorinated gas to said processing chamber at a flow rate of about 10 to about 200 sccm, said second fluorinated gas selected from the group consisting of CF₄, NF₃ and SF₆;

supplying oxygen to said processing chamber at a flow rate of about 10 to about 200 sccm;

regulating said processing chamber pressure between about 0.5 to about 100 mTorr;

applying inductive source power of about 100 to about 1000 Watts to said inductively coupled antenna;

applying bias power of about 10 to about 300 Watts to said pedestal; and

,

forming a second plasma in said chamber from said fluorinated gas and oxygen.

18. A computer readable medium containing a software routine that, when execute by a processor, cause the semiconductor wafer processing system to perform the steps of:

supplying a reactant gas comprising a fluorinated gas to a processing chamber;

supplying oxygen to said processing chamber;

forming a plasma in said chamber from said reactant gas.

19. The computer readable medium of claim 18 further comprising the step of reaching an endpoint at or near the breakthrough of said tungsten layer wherein said oxygen supplying step occurs after said endpoint is reached.

20. The computer readable medium of claim 18 wherein the fluorinated gas is selected from the group consisting of CF₄, NF₃ and SF₆.

21. The computer readable medium of claim 18 where said fluorinated gas is supplied at a flow rate of about 10 to about 200 sccm.

22. The computer readable medium of claim 18 further comprising the steps of:

applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber; and

,

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber.

23. The computer readable medium of claim 18 wherein the steps of supplying the fluorinated gas and oxygen further comprise the step of:

regulating said chamber pressure between about 0.5 to about 100 mTorr.

24. The computer readable medium of claim 18 further comprising the step of:

performing a main-etch to substantially remove said tungsten layer.

25. The computer readable medium of claim 24 wherein said main-etch further comprises:

supplying a fluorinated gas to a processing chamber at a flow rate of about 10 to about 200 sccm, said fluorinated gas selected from the group consisting of CF₄, NF₃ and SF₆;

regulating said chamber pressure between about 0.5 to about 100 mTorr;

applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber;

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber; and

,

forming a plasma in said chamber from said fluorinated gas.

26. The computer readable medium of claim 24 wherein said fluorinated gas is supplied at a flow rate of about 10 to about 200 sccm.

27. The computer readable medium of claim 18 wherein said oxygen is supplied at a flow rate of about 10 to about 200 sccm.

28. The computer readable medium of claim 24 wherein the steps of supplying the fluorinated gas and oxygen further comprise the step of:

regulating said chamber pressure between about 0.5 to about 100 mTorr.

29. The computer readable medium of claim 24 further comprising the steps of:

applying inductive source power of about 100 to about 1000 Watts to an inductively coupled antenna disposed about said processing chamber; and

,

applying bias power of about 10 to about 300 Watts to a pedestal disposed within said processing chamber.