Plasma pretreatment of photoresist in an oxide etch process

• US 6,326,307 B1
• Filed: 11/15/1999
• Issued: 12/04/2001
• Est. Priority Date: 11/15/1999
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Lindley, Roger A., Joshi, Ajey M., Komatsu, Takehito, Pu, Bryan Y., Kim, Yunsang, Shan, Hongqing, Fong, Henry
• Primary Examiner(s): Utech, Benjamin L.
• Assistant Examiner(s): PEREZ RAMOS, VANESSA
• Application Number:
  US09/440,792
• Time in Patent Office: 750 Days
• Field of Search: 438/710, 438/712, 438/689, 438/713
• US Class Current: 438/689
• CPC Class Codes: H01L 21/31116 by dry-etching
• CPC Class Codes: H01L 21/76802 by forming openings in dielectrics

Abstract

A photoresist plasma pretreatment performed prior to a plasma oxide etch. The plasma pretreatment is performed with an argon plasma or a carbon tetrafluoride and trifluoromethane plasma with lower power than in the main etch or is performed with a plasma of difluoromethane or trifluoromethane and carbon monoxide but no argon diluent gas. Thereby, striations on the oxide wall are reduced.

Claims

1. A plasma oxide etch process comprising the steps of:

placing a substrate including an oxide layer covered with a patterned photoresist layer onto a pedestal in a plasma etch reactor;

a first step of plasma treating in said reactor the photoresist layer with a first level of RF power applied to said chamber to create a plasma therein and with a first gas mixture including a first gas selected from a noble gas and a fluoromethane of at least three fluorine atoms and not including more than 5% of a fluorocarbon having an F/C ratio of 2 or less; and

a subsequent second step of plasma etching in the reactor the oxide to form a hole therein with a second level of RF power greater than said first level applied to said chamber and with a second gas mixture including a fluorocarbon having an F/C ratio of no more than two and no more than 1 hydrogen atom;

whereby said plasma treating reduces an occurrence of striations on a sidewall of said hole in said oxide.

2. The process of claim 1, wherein a plasma continues in said reactor between said first and second steps.

3. The process of claim 1, wherein said plasma treating and etching are performed in a single plasma etch reactor without breaking vacuum therebetween.

4. The process of claim 1, wherein said first gas mixture includes a noble gas.

5. The process of claim 4, wherein said noble gas is argon.

6. The process of claim 4, wherein said first gas mixture consists of said noble gas.

7. The process of claim 6, wherein said noble gas is argon.

8. The process of claim 1, where said first gas mixture includes carbon tetrafluoride.

9. The process of claim 8, wherein said first gas mixture consists of said carbon tetrafluoride and trifluoromethane.

10. The process of claim 1, wherein said photoresist layer directly overlies said oxide layer.

11. The process of claim 1, wherein said pedestal is a pedestal electrode and said first and second steps apply said RF power to said pedestal electrode.

12. The process of claim 11, wherein said first level of RF power is no more than 800 W normalized to a 200 mm-diameter substrate.

13. The process of claim 11, wherein said plasma etch reactor is a capacitively coupled reactive ion etch reactor.

14. The process of claim 13, wherein said reactor is a magnetically enhanced capacitively coupled reactive ion etch reactor.

15. The process of claim 14, wherein said etch reactor includes at least one magnetic coil for creating a magnetic field for magnetic enhancement, and wherein said plasma treating step is performed with a level of magnetic field less than that used in said etching step.

16. An oxide etch process for etching a hole in an oxide layer overlain by a photomask of patterned photoresist, comprising the steps of:

plasma treating said photomask with a first plasma principally comprising argon and not including more than 5% of a fluorocarbon having an F/C ratio of two or less; and

subsequently etching said oxide layer with a second plasma including a fluorocarbon having an F/C ratio of no more than two and no more than one carbon atom.

17. The process of claim 16, wherein said plasma treating and said etching are performed in a same plasma reaction chamber.

18. The process of claim 17, firther comprising placing a substrate comprising said oxide and photomask onto a pedestal electrode in said plasma reaction chamber;

wherein said plasma treating step includes applying a first level of RF power to said pedestal electrode; and

wherein said etching step includes applying a second level of RF power less than said first level to said pedestal electrode.

19. The process of claim 18, wherein said first level of RF power is less than 800 W normalized to a 200 mm-diameter substrate.

20. A process for pretreating patterned photoresist, comprising subjecting the photoresist to a plasma of a pretreatment gas comprising a fluoromethane selected from the group consisting of difluoromethane and monofluoromethane and carbon monoxide but substantially no diluent gas.

21. The process of claim 20, further comprising the subsequent step of subjecting an oxide layer underlying the patterned photoresist to a plasma of an etching gas comprising a fluorocarbon other than difluoromethane and monofluoromethane and a diluent gas.

22. The process of claim 20, wherein said fluoromethane is difluoromethane.

23. The process of claim 20, wherein said pretreatment gas includes at least twice an amount of carbon monoxide as said fluoromethane.

24. The process of claim 20, said pretreatment gas further comprises oxygen.

25. A plasma oxide etch process, comprising the steps of:

placing a substrate including an oxide layer covered with a patterned photoresist layer onto a pedestal in a plasma etch reactor;

a first step of plasma treating in said reactor the photoresist layer with a first level of RF power applied to said chamber to create a plasma therein and with a first gas mixture including a first gas selected from a noble gas and a fluoromethane of at least three fluorine atoms and not including more than 5% of a fluorocarbon having an F/C ratio of 2 or less; and

a subsequent second step of plasma etching in the reactor the oxide layer according to a pattern of said plasma treated photoresist layer to form a hole in said oxide layer, said plasma etching being performed with a second level of RF power greater than said first level applied to said chamber and with a second gas mixture including a fluorocarbon having an F/C ratio of no more than two and no more than 1 hydrogen atom.

26. The process of claim 25, wherein said first gas mixture consists essentially of argon.

27. The process of claim 25, wherein said first gas mixture consists essentially of a gas selected from the group consisting of CF₄ and CHF₃.

28. The process of claim 27, wherein said first gas mixture consists essentially of a combination of CF₄ and CHF₃.