Etching an oxidized organo-silane film

• US 6,168,726 B1
• Filed: 11/25/1998
• Issued: 01/02/2001
• Est. Priority Date: 11/25/1998
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Li, Zongyu, Naik, Mehul, Ding, Jian
• Primary Examiner(s): Mills, Gregory
• Assistant Examiner(s): ALEJANDRO MULERO, LUZ L
• Application Number:
  US09/200,086
• Time in Patent Office: 769 Days
• Field of Search: 216/62, 216/63, 216/67, 216/68, 216/81, 216/79, 438/710, 438/718, 438/725
• US Class Current: 216/79
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/31138 by dry-etching
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics
• CPC Class Codes: H01L 21/76807 for dual damascene structures
• CPC Class Codes: H01L 21/76828 thermal treatment

Abstract

A process for etching an oxidized organo-silane film exhibiting a low dielectric constant and having a most preferred atomic composition of 52% hydrogen, 8% carbon, 19% silicon, and 21% oxygen. The process of etching deep holes in the organo-silane film while stopping on a nitride or other non-oxide layer is preferably performed in an inductively coupled high-density plasma reactor with a main etching gas mixture of a fluorocarbon, such as C₄F₈, and argon while the pedestal electrode supporting the wafer is RF biased. For very deep and narrow holes, oxygen or nitrogen may be added to volatize carbon. In an integrated process in which an oxygen plasma is used either for the film etching or for post-etch treatments such as ashing or nitride removal, the oxygen plasma should be excited only when no RF bias is applied to the pedestal electrode, and thereafter the sample should be annealed in an inert environment to recover the low dielectric constant.

Claims

1. A method of etching a carbon-doped dielectric comprising hydrogen, carbon, silicon, and oxygen, an atomic percentage of said carbon being between 5 and 25% and an atomic percentage of said silicon being between 15 and 25%, and an atomic percentage of said hydrogen being between 35 and 60%, said method comprising the steps of:

a first step of flowing a first etching gas mixture into a reaction chamber containing a pedestal electrode supporting a substrate having a patterned mask formed over said carbon-doped dielectric, said first etching gas mixture comprising a fluorocarbon and a chemically inactive gas;

RF biasing said pedestal electrode; and

a first step of exciting said first etching gas into a first plasma to thereby etch said carbon-doped dielectric while said pedestal electrode is RF biased.

2. The method of claim 1, wherein said first exciting step includes inductively coupling RF power into said chamber.

3. The method of claim 1, further comprising:

a subsequent, second step of flowing a second etching gas into said reaction chamber comprising a carbon-volatizing gas; and

a second step of exciting said second etching gas into a second plasma.

4. The method of claim 1, wherein said first exciting step excites said first plasma into a high-density plasma in a source region apart from said pedestal electrode.

5. The method of claim 1, wherein said first etching gas mixture additionally comprises a carbon-volatizing gas.

6. The method of claim 5, wherein said carbon-volatizing gas comprises nitrogen.

7. The method of claim 5, wherein said carbon-volatizing gas comprises oxygen.

8. The method of claim 1, wherein said first etching mixture contains no carbon-volatizing gas.

9. The method of claim 1, further comprising:

a second step of flowing a second etching gas mixture into said reaction chamber, said second etching mixture comprising a fluorocarbon, a chemically inactive gas, and a carbon-volatizing gas; and

a second step of exciting said second etching gas into a second plasma while said pedestal electrode is RF biased to thereby etch said carbon-doped dielectric.

10. The method of claim 9, wherein said carbon-volatizing gas comprises nitrogen.

11. The method of claim 9, wherein said carbon-volatizing gas comprises oxygen.

12. The method of claim 1, further comprising:

a second step of flowing a second etching gas mixture into said reaction chamber, said second etching mixture comprising oxygen; and

a second step of exciting said second etching gas into a plasma.

13. The method of claim 12, wherein said second exciting step is performed while said pedestal electrode is not substantially RF biased.

14. The method of claim 13, wherein said second steps of flowing and exciting are performed after said oxidized organo-silane film has been etched through to thereby remove residues.

15. The method of claim 12, wherein said second gas mixture consists essentially of oxygen.

16. The method of claim 12, further comprising, after said second exciting step, a step of annealing said substrate in a substantially oxygen-free environment.

17. The method of claim 16, wherein said annealing is performed in an inert atmosphere at between 200 and 450°

C.

18. The method of claim 1, wherein said fluorocarbon comprises octafluorocyclobutane.

19. The method of claim 1, wherein said fluorocarbon comprises trifluoromethane.

20. The method of claim 1, wherein a silica layer overlies said carbon-doped dielectric and is overlaid by said patterned mask and wherein said first exciting step etches through said silica layer.

21. The method of claim 1, wherein a nitride layer overlies said carbon-doped dielectric and further comprising the steps performed before said first flowing step of:

a second step of flowing a second gas mixture into said reaction chamber, said second gas mixture comprising said fluorocarbon, said chemically inactive gas, and another gas reducing selectivity to said nitride layer.

22. The method of claim 21, wherein said another gas comprises carbon monoxide.

23. A method of etching a film formed by oxidizing an organo-silane gas in a plasma excited with a surface power density of less than 1 W/cm² at a temperature of less than 100°

C., said etching method comprising the steps of;

a first step of flowing a first etching gas into a reaction chamber containing a pedestal electrode supporting a substrate having a patterned mask formed over said film, said first etching gas comprising a fluorocarbon and a chemically inactive gas;

RF biasing said pedestal electrode; and

a first step of exciting said first etching gas into a plasma to thereby etch said film while said pedestal electrode is RF biased.

24. The method of claim 23, wherein said first exciting step includes inductively coupling power into said chamber.

25. The method of claim 23, wherein said first etching gas additionally comprises a carbon-volatizing gas.

26. The method of claim 23, further comprising:

a second step of flowing into said chamber a second etching gas comprising oxygen; and

a second step of exciting said second gas mixture into a plasma while said pedestal electrode is not substantially RF biased.

27. The method of claim 26, further comprising the subsequent step of annealing said film in an inert environment at a temperature of between 200 and 450°

C.

28. A method of etching a hole having a high aspect ratio in a film of a low-k dielectric material comprising carbon, oxygen, and hydrogen overlying a non-oxide layer formed in a substrate, comprising the steps of:

flowing a first etching gas into a reaction chamber containing a pedestal electrode supporting said substrate having a patterned mask for said hole formed over said film, said first etching gas comprising a fluorocarbon gas, a carbon-volatizing gas, and a chemically inactive gas;

RF biasing said pedestal electrode; and

inductively coupling RF power into said reaction chamber to excite said first etching gas mixture into a plasma to thereby etch said film while said pedestal electrode is RF biased.

29. The method of claim 28, wherein said low-k dielectric material additionally comprises silicon.

30. The method of claim 28, wherein a flow of said chemically inactive gas is at east three times as large as a flow of said fluorocarbon gas.

31. The method of claim 28, further comprising:

a second step of flowing into said chamber a second etching gas comprising oxygen; and

exciting said second etching gas into a plasma while said pedestal electrode is not substantially RF biased.

32. The method of claim 31, wherein said low-k material additionally comprises silicon.

33. The method of claim 31, further comprising the subsequent step of annealing said film in an inert environment at a temperature of between 200 and 450°

C. to reduce an effect of said second exciting step increasing a dielectric constant of said film.

34. The method of claim 28, wherein said carbon-volatizing gas comprises either gaseous nitrogen or oxygen.

35. A method of etching a low-k dielectric film comprising carbon, hydrogen, and oxygen formed over a non-oxide film, comprising the steps of:

flowing a first etching gas into a reaction chamber containing a pedestal electrode supporting said substrate having a patterned mask for said hole formed over said low-k dielectric film, said first etching gas comprising a fluorocarbon and a chemically inactive gas;

RF biasing said pedestal electrode;

exciting said first etching gas into a plasma to thereby etch said low-k dielectric film while said pedestal electrode is RF biased;

a subsequent, second step of flowing into said chamber a second etching gas comprising oxygen; and

a second step of exciting said second etching gas into a plasma while said pedestal electrode is not substantially RF biased.

36. The method of claim 35, further comprising the subsequent step of annealing said low-k dielectric film in an inert environment at a temperature of between 200 and 450°

C. to decrease an effect of said second exciting step increasing a dielectric constant of said low-k dielectric film.

37. The method of claim 36, wherein said low-k dielectric film additionally comprises silicon.

38. The method of claim 35, wherein said low-k dielectric film additionally comprises silicon.

39. The method of claim 35, wherein said first etching gas additionally comprises a carbon-volatizing gas selected from the group consisting of gaseous oxygen and gaseous nitrogen.

40. The method of claim 35, wherein during said first flowing step a flow of said chemically inactive gas is at least three times as great as a flow of said fluorocarbon.