High selectivity etching of a lead overlay structure

• US 20040020894A1
• Filed: 08/02/2002
• Published: 02/05/2004
• Est. Priority Date: 08/02/2002
• Status: Active Grant

• Current Assignee: Veeco Instruments Incorporated
• Original Assignee: Veeco Instruments Incorporated
• Inventors: Williams, Kurt E., Hegde, Hariharakeshara
• Granted Patent: US 6,838,389 B2
• Time in Patent Office: Days
• US Class Current: 216/14
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• 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: G11B 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• CPC Class Codes: G11B 5/3116 Shaping of layers, poles or gaps for improving the form of the electrical signal transduced, e.g. for shielding, contour effect, equalizing, side flux fringing, cross talk reduction between heads or between heads and information tracks G11B5/3113, G11B5/245 take precedence
• CPC Class Codes: G11B 5/3163 Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers
• CPC Class Codes: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures
• CPC Class Codes: H01L 21/0332 characterised by their composition, e.g. multilayer masks, materials
• CPC Class Codes: H01L 21/32136 using plasmas
• CPC Class Codes: H01L 21/32139 using masks

Abstract

A multi-step etching process for a lead overlay structure such as a thin-film magnetic head structure using secondary ion mass spectroscopy (SIMS) whereby high selectivity of a lead material or other high conductivity metal layer is realized versus that of a metallic mask material and stopping layer. The first step includes patterning the mask layer using IBE or RIE. Advantageously, a photoresist layer is present over a portion of the mask layer and is left in place to be removed in a subsequent step. The second step includes etching the high conductivity metal layer using CAIBE or RIBE with an inert/reactive gas mixture and using SIMS to detect when the stopping layer is reached. The gas mixture comprises an inert gas and a reactive gas that is either oxygen, nitrogen, or a combination of oxygen and nitrogen, whereby the ionized gas mixture contains ions that increase the sensitivity of the SIMS yield of the stopping layer such that the end point of the high conductivity metal layer is detected and etching can then be stopped at the appropriate time. The chemistry of the second etching step is effective to also remove the photoresist at a high etch rate. The third step includes etching the stopping layer with IBE using an inert gas, advantageously with a high angle of about 40-70°. The third step may also be effective to etch debris redeposited on the sidewalls of the structure, and to remove all or a portion of the remaining mask layer.

Claims

1. A method of etching a lead structure comprising at least a mask layer, a high conductivity metal layer and a stopping layer, the method comprising at least the steps of:

(a) patterning the mask layer through to the high conductivity metal layer with a process selected from the group consisting of ion beam etching and reactive ion etching;

(b) etching the high conductivity metal layer through to the stopping layer with a process selected from the group consisting of chemically assisted ion beam etching or reactive ion beam etching, wherein the etching process uses a gas mixture of an inert gas and a reactive gas selected from the group consisting of oxygen, nitrogen, and a combination of oxygen and nitrogen, and further comprising using secondary ion mass spectroscopy for end point detection and stopping the etching when the end point detection indicates the stopping layer is reached; and

(c) etching the stopping layer with ion beam etching using an inert gas.

2. The method of claim 1 wherein the patterning process of step (a) has a selectivity to the high conductivity metal layer of at least 2:

1.

3. The method of claim 1 wherein the patterning process of step (a) has a selectivity to the high conductivity metal layer of at least about 5:

1.

4. The method of claim 1 wherein the etching process of step (b) has a selectivity to the mask layer and the stopping layer of at least 2:

1.

5. The method of claim 1 wherein the etching process of step (b) has a selectivity to the mask layer and the stopping layer of at least about 5:

1.

6. The method of claim 1 wherein the structure further comprises a photoresist, and wherein the method further comprises leaving the photoresist in place during step (a) and removing the photoresist during step (b).

7. The method of claim 1 wherein the high conductivity metal layer comprises a Au lead material.

8. The method of claim 1 wherein the high conductivity metal layer comprises a Au/Pt bilayer.

9. The method of claim 1 wherein the mask layer and stopping layer each comprise TiW.

10. The method of claim 1 wherein the mask layer and stopping layer each comprise a Ti/Ta bilayer.

11. The method of claim 1 wherein the patterning of step (a) is with ion beam etching using Ar gas and further comprising using secondary ion mass spectroscopy for end point detection and stopping the patterning when the end point detection indicates the high conductivity metal layer is reached.

12. The method of claim 1 further comprising, during step (c), etching the mask layer until at least a portion of said layer is removed.

13. The method of claim 1 further comprising, during step (c), etching debris redeposited on sidewall structures during steps (a) and (b).

14. The method of claim 1 wherein steps (a)-(c) are performed sequentially in a single vacuum chamber without removing the structure between steps.

15. The method of claim 1 wherein the inert gases of steps (b) and (c) are both Ar.

16. The method of claim 1 wherein the high conductivity metal layer is a noble metal.

27. The method of claim 1 further comprising, during step (c), etching the mask layer until at least a portion of said layer is removed.

28. The method of claim 1 further comprising, during step (c), etching debris redeposited on sidewall structures during steps (a) and (b).

29. The method of claim 1 wherein steps (a)-(c) are performed sequentially in a single vacuum chamber without removing the structure between steps.

30. The method of claim 1 wherein the inert gases of steps (b) and (c) are both Ar.

31. The method of claim 1 wherein the high conductivity metal layer is a noble metal.

17. A method of etching a lead structure comprising at least a photoresist, a mask layer, a high conductivity metal layer and a stopping layer, the method comprising:

(a) patterning the mask layer through to the high conductivity metal layer, leaving the photoresist in place, with a process selected from the group consisting of;

(i) ion beam etching using secondary ion mass spectroscopy for end point detection and stopping the patterning when the end point detection indicates the high conductivity metal layer is reached, and

(ii) reactive ion etching having a selectivity to the high conductivity metal layer of at least 2;

1;

(b) etching the high conductivity metal layer through to the stopping layer and removing the photoresist with a process selected from the group consisting of chemically assisted ion beam etching and reactive ion beam etching, the process having a selectivity to the mask layer and the stopping layer of at least 2;

1, wherein the etching process uses a gas mixture of an inert gas and a reactive gas selected from the group consisting of oxygen, nitrogen, and a combination of oxygen and nitrogen and wherein the process further comprises using secondary ion mass spectroscopy for end point detection and stopping the etching when the end point detection indicates the stopping layer is reached; and

(c) etching the stopping layer with ion beam etching at an angle of about 40-70°

using an inert gas.

18. The method of claim 17 wherein the patterning process of step (a)(ii) has a selectivity to the high conductivity metal layer of at least about 5:

1.

19. The method of claim 17 wherein the etching process of step (a)(i) has a selectivity to the high conductivity metal layer of at least 2:

1.

20. The method of claim 17 wherein the etching process of step (a)(i) has a selectivity to the high conductivity metal layer of at least 5:

1.

21. The method of claim 17 wherein the etching process of step (b) has a selectivity to the mask layer and the stopping layer of at least about 5:

1.

22. The method of claim 17 wherein the high conductivity metal layer comprises a Au lead material.

23. The method of claim 17 wherein the high conductivity metal layer comprises a Au/Pt bilayer.

24. The method of claim 17 wherein the mask layer and stopping layer each comprise TiW.

25. The method of claim 17 wherein the mask layer and stopping layer each comprise a Ti/Ta bilayer.

26. The method of claim 17 wherein the patterning of step (a) is with ion beam etching using Ar gas.

32. A method of etching a lead structure comprising at least a photoresist, a TiW mask layer, a Au/Pt bilayer and a TiW stopping layer, the method comprising:

(a) patterning the TiW mask layer through to the Au/Pt bilayer, leaving the photoresist in place, with a process selected from the group consisting of;

(i) ion beam etching using secondary ion mass spectroscopy for end point detection and stopping the patterning when the end point detection indicates the Au/Pt bilayer is reached, and

(ii) reactive ion etching having a selectivity to Au of at least 2;

1;

(b) etching the Au/Pt bilayer through to the TiW stopping layer and removing the photoresist with a process selected from the group consisting of chemically assisted ion beam etching and reactive ion beam etching, the process having a selectivity to TiW of at least 2;

1, wherein the etching process uses a gas mixture of an inert gas and a reactive gas selected from the group consisting of oxygen, nitrogen, and a combination of oxygen and nitrogen and wherein the process further comprises using secondary ion mass spectroscopy for end point detection and stopping the etching when the end point detection indicates the TiW stopping layer is reached; and

(c) etching the TiW stopping layer with ion beam etching at an angle of about 40-70°

using an inert gas.

33. The method of claim 32 wherein the patterning process of step (a)(ii) has a selectivity to Au of at least about 5:

1.

34. The method of claim 32 wherein the etching process of step (a)(i) has a selectivity to Au of at least 2:

1.

35. The method of claim 32 wherein the etching process of step (a)(i) has a selectivity to Au of at least 5:

1.

36. The method of claim 32 wherein the etching process of step (b) has a selectivity to TiW of at least about 5:

1.

37. The method of claim 32 wherein the patterning of step (a) is with ion beam etching using Ar gas.

38. The method of claim 32 further comprising, during step (c), etching the TiW mask layer until at least a portion of said layer is removed.

39. The method of claim 32 further comprising, during step (c), etching debris redeposited on sidewall structures during steps (a) and (b).

40. The method of claim 32 wherein steps (a)-(c) are performed sequentially in a single vacuum chamber without removing the structure between steps.

41. The method of claim 32 wherein the inert gases of steps (b) and (c) are both Ar.

42. A method of etching a lead structure comprising at least a photoresist, a Ti/Ta mask bilayer, a Au lead layer and a Ti/Ta stopping bilayer, the method comprising:

(a) patterning the Ti/Ta mask bilayer through to the Au lead layer, leaving the photoresist in place, with a process selected from the group consisting of;

(i) ion beam etching using secondary ion mass spectroscopy for end point detection and stopping the patterning when the end point detection indicates the Au lead layer is reached, and

(ii) reactive ion etching having a selectivity to Au of at least 2;

1;

(b) etching the Au lead layer through to the Ti/Ta stopping bilayer and removing the photoresist with a process selected from the group consisting of chemically assisted ion beam etching and reactive ion beam etching, the process having a selectivity to Ti of at least 2;

1, wherein the etching process uses a gas mixture of an inert gas and a reactive gas selected from the group consisting of oxygen, nitrogen, and a combination of oxygen and nitrogen and wherein the process further comprises using secondary ion mass spectroscopy for end point detection and stopping the etching when the end point detection indicates the Ti/Ta stopping bilayer is reached; and

(c) etching the Ti/Ta stopping bilayer with ion beam etching at an angle of about 40-70°

using an inert gas.

43. The method of claim 42 wherein the patterning process of step (a)(ii) has a selectivity to Au of at least about 5:

1.

44. The method of claim 42 wherein the etching process of step (a)(i) has a selectivity to Au of at least 2:

1.

45. The method of claim 42 wherein the etching process of step (a)(i) has a selectivity to Au of at least 5:

1.

46. The method of claim 42 wherein the etching process of step (b) has a selectivity to Ti of at least about 5:

1.

47. The method of claim 42 wherein the patterning of step (a) is with ion beam etching using Ar gas.

48. The method of claim 42 further comprising, during step (c), etching the Ti/Ta mask bilayer until at least a portion of said bilayer is removed.

49. The method of claim 42 further comprising, during step (c), etching debris redeposited on sidewall structures during steps (a) and (b).

50. The method of claim 42 wherein steps (a)-(c) are performed sequentially in a single vacuum chamber without removing the structure between steps.

51. The method of claim 42 wherein the inert gases of steps (b) and (c) are both Ar.