Etching of chromium layers on photomasks utilizing high density plasma and low frequency RF bias

• US 20040259367A1
• Filed: 05/03/2004
• Published: 12/23/2004
• Est. Priority Date: 05/05/2003
• Status: Active Grant

• Current Assignee: Plasma-Therm Corporation
• Original Assignee: Unaxis USA Incorporated (Unaxis)
• Inventors: Westerman, Russell, Plumhoff, Jason, Johnson, David J., Constantine, Christopher
• Granted Patent: US 7,008,877 B2
• Time in Patent Office: Days
• US Class Current: 438/695
• 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: G03F 1/80 Etching
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma

Abstract

The present invention provides a method and an apparatus for etching a photolithographic substrate. The photolithographic substrate is placed on a support member in a vacuum chamber. A processing gas for etching a material from the photolithographic substrate is introduced into the vacuum chamber, and a plasma is generated. An RF bias is supplied to the support member in the vacuum chamber through an RF bias frequency generator at or below the ion transit frequency. Exposed material is etched from the photolithographic substrate with improved CD Etch Linearity and CD Etch Bias since the low frequency bias allows the developed charge on the photolithographic substrate, generated by the plasma, to dissipate.

Claims

1. A method for etching a photolithographic substrate comprising the steps of:

placing the photolithographic substrate on a support member in a vacuum chamber;

introducing at least one process gas into the vacuum chamber;

generating a plasma;

supplying an RF bias at or below the ion transit frequency to the support member in the vacuum chamber; and

etching the photolithographic substrate.

2. The method of claim 1 wherein the photolithographic substrate is comprised of a silicon containing material.

3. The method of claim 2 wherein the silicon containing material is quartz.

4. The method of claim 1 wherein the photolithographic substrate comprises an optically transparent material.

5. The method of claim 1 wherein the photolithographic substrate further comprises a patterned masking layer.

6. The method of claim 5 wherein the masking layer is photoresist.

7. The method of claim 5 wherein the masking layer contains a metal.

8. The method of claim 1 wherein the RF bias to the substrate support is voltage controlled.

9. The method of claim 8 wherein said RF bias has a Peak-to-Peak voltage of less than about 1.5 kV.

10. The method of claim 1 wherein the RF bias frequency is less than about 2 MHz.

11. The method of claim 1 wherein the RF bias frequency is about 380 kHz.

12. The method of claim 1 wherein the RF bias waveform is modulated.

13. The method of claim 12 wherein the modulation is pulsing.

14. The method of claim 13 wherein the duty cycle of the pulsed waveform is less than about 50%.

15. The method of claim 12 wherein the modulated RF bias waveform has a modulation period of less than about 10 ms.

16. The method of claim 12 wherein the RF bias waveform is amplitude modulated.

17. The method of claim 12 wherein the RF bias waveform is frequency modulated.

18. A method for etching at least one material on a photolithographic substrate comprising the steps of:

placing the photolithographic substrate on a support member in a vacuum chamber;

introducing at least one process gas into the vacuum chamber;

generating a plasma;

supplying an RF bias at or below the ion transit frequency to the support member in the vacuum chamber; and

etching at least one material from the photolithographic substrate.

19. The method of claim 18 wherein the etched material is chromium containing.

20. The method of claim 18 wherein the etched material contains a refractory metal.

21. The method of claim 18 wherein the etched material is silicon containing.

22. The method of claim 18 wherein the photolithographic substrate further comprising a patterned masking layer.

23. The method of claim 22 wherein the masking layer is photoresist.

24. The method of claim 22 wherein the masking layer contains a metal.

25. The method of claim 18 wherein the RF bias to the substrate support is voltage controlled.

26. The method of claim 25 wherein said RF bias has a Peak-to-Peak voltage of less than about 1.5 kV.

27. The method of claim 18 wherein the RF bias frequency is less than about 2 MHz.

28. The method of claim 18 wherein the RF bias frequency is about 380 kHz.

29. The method of claim 18 wherein the RF bias waveform is modulated.

30. The method of claim 29 wherein the modulation is pulsing.

31. The method of claim 30 wherein the duty cycle of the pulsed waveform is less than about 50%.

32. The method of claim 29 wherein the modulated RF bias waveform has a modulation period of less than about 10 ms.

33. The method of claim 29 wherein the RF bias waveform is amplitude modulated.

34. The method of claim 29 wherein the RF bias waveform is frequency modulated.

35. An apparatus for processing a photolithographic substrate comprising:

a vacuum chamber;

at least one gas supply communicating with said vacuum chamber for providing at least one process gas to said vacuum chamber;

a plasma generating source for generating a plasma in said vacuum chamber; and

an RF power source operating at an RF bias frequency at or below the ion transit frequency, said RF power source coupled to the photolithographic substrate support.

36. The apparatus of claim 35 further comprising an RF modulator for modulating the RF bias waveform.

37. A method for etching a photolithographic substrate comprising the steps of:

placing the photolithographic substrate on a support member in a vacuum chamber;

introducing at least one process gas into the vacuum chamber;

generating a plasma;

supplying an RF bias to the support member in the vacuum chamber;

controlling the level of the RF bias; and

etching the photolithographic substrate.

38. The method of claim 37 wherein the RF bias is controlled by controlling the peak to peak voltage.

39. The method of claim 37 wherein the RF bias is pulsed.

40. The method of claim 37 wherein the RF bias is modulated.

41. The method of claim 37 wherein the applied RF bias is at or below the ion transit frequency.