Apparatus and method for contacting a conductive layer

• US 6,478,976 B1
• Filed: 12/30/1998
• Issued: 11/12/2002
• Est. Priority Date: 12/30/1998
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SA (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Thomas, Danielle A., Do-Bento-Vieira, Antonio A., Lepert, Arnaud Yves
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): Ahmed, Shamim
• Application Number:
  US09/224,815
• Time in Patent Office: 1,413 Days
• Field of Search: 216/13, 216/17, 216/18, 438/720, 438/725
• US Class Current: 216/18
• CPC Class Codes: G06V 40/1329 Protecting the fingerprint sensor against damage caused by the finger

Abstract

A structure and method for creating a contact between a conductive layer and a pad for dissipating electrostatic charges comprising the steps of, forming a pad and a composite insulating layer between and over conductive plates on a substrate, wherein the insulating layer isolates and protects the conductive plates and pad from damage, the insulating layer comprising a dielectric region underlying a conductive layer. A passivation layer is formed over at least a portion of the conductive layer and a photoresist is patterned over at least a portion of the passivation. An opening is etched through the passivation and the insulating layers, wherein the photoresist and the conductive layer serve as masks. Finally, a conductive material is deposited in the opening to form an electrical contact between the pad and the conductive layer.

Claims

1. A method of forming an electrostatic discharge device contact comprising the steps of:

forming a pad on a substrate;

forming a composite protective layer between and over conductive plates and over and around the pad, wherein the protective layer isolates the conductive plates and pad and protects them from damage, and wherein the protective layer comprises a dielectric region underlying an electrostatic discharge region extending partially over the pad;

patterning a photoresist over the electrostatic discharge region, wherein the photoresist pattern partially covers the electrostatic discharge region; and

etching an opening through the protective layer and adjacent the electrostatic discharge region, wherein the photoresist and the electrostatic discharge region serve as masks during etching through a portion of the protective layer below the electrostatic discharge region, thereby forming the opening to the pad.

2. The method of claim 1, further comprising the step of:

forming a passivation layer over the dielectric region and the electrostatic discharge region.

3. The method of claim 2, further comprising the step of:

patterning a photoresist on the passivation layer, wherein the photoresist pattern partially covers the electrostatic discharge region; and

etching an opening through the passivation layer and the insulating layer, wherein the photoresist and the electrostatic discharge region serve as masks during a subsequent etch step.

4. The method of claim 1, further comprising the step of:

etching an opening through the protective layer to the pad; and

depositing a conductive material in the opening to form an electrical contact between the pad and the electrostatic discharge region.

5. The method of claim 4, wherein the conductive material comprises a conductive polymer.

6. The method of claim 4, wherein the conductive material comprises a wire bond.

7. The method of claim 4, wherein the conductive material comprises solder.

8. A method of forming an electrostatic discharge device contact comprising the steps of:

forming a pad on a substrate;

depositing a composite protective layer between and over conductive plates and over and arround the pad, wherein the protective layer isolates the conductive plates and pad and protects them from damage, and wherein the protective layer comprises a dielectric region underlying a conductive layer;

forming a passivation layer over at least a portion of the conductive layer;

patterning a photoresist over at least a portion of the passivation layer and the conductive layer;

etching an opening through the passivation layer, the conductive layer and the protective layer, wherein the photoresist and the conductive layer serve as masks during etching through the protective layer; and

depositing a conductive material in the opening to form an electrical contact between the pad and the conductive layer.

9. The method of claim 8, wherein the conductive material comprises a conductive polymer.

10. The method of claim 8, wherein the conductive material comprises a metal.

11. The method of claim 8, wherein the conductive material comprises solder.

12. The method of claim 8, wherein the conductive material comprises solder.

13. The method of claim 8, wherein the thickness of the dielectric layer is between approximately 6,000 and 12,000 angstroms.

14. The method of claim 8, wherein the dielectric material comprises oxide.

15. The method of claim 8, wherein the dielectric material comprises a doped glass.

16. The method of claim 8, wherein the dielectric material comprises a first dielectric layer disposed under a second dielectric layer.

17. The method of claim 16, wherein the first and second dielectric layers comprise different compatible materials.

18. The method of claim 16, wherein the first dielectric layer comprises oxide.

19. The method of claim 16, wherein the first dielectric layer comprises doped glass.

20. The method of claim 16, wherein the second dielectric layer comprises nitride.

21. The method of claim 16, wherein the first and second dielectric layers have a thickness between approximately 3,000 and 6,000 angstroms.

22. The method of claim 8, wherein the conductive layer has a sheet resistance low enough to adequately dissipate the electrostatic charge.

23. The method of claim 8, wherein the conductive layer comprises aluminum.

24. The method of claim 8, wherein the conductive layer has a thickness of between approximately 5,000 to 15,000 angstroms.

25. The method of claim 8, wherein the conductive layer has a resistivity of approximately 0.04 ohms per square.

26. The method of claim 8, wherein the conductive layer comprises titanium.

27. The method of claim 26, wherein the conductive layer has a thickness of between approximately 500 to 1,000 angstroms.

28. The method of claim 26, wherein the conductive layer has a resistivity of approximately 0.14 ohms per square.

29. The method of claim 8, wherein the conductive layer comprises tungsten.

30. The method of claim 29, wherein the conductive layer has a thickness of between approximately 4,000 to 8,000 angstroms.

31. The method of claim 29, wherein the conductive layer has a resistivity of approximately 0.14 ohms per square.

32. The method of claim 8, wherein the passivation layer has an optimum thickness to prevent damage to the underlying conductive plates due to use and environment while also allowing an electrostatic charge to dissipate through the conductive layer.

33. The method of claim 8, further comprising the step of:

forming a composite passivation layer disposed over at least a portion of the dielectric layer.

34. The method of claim 33, wherein the passivation layer comprises silicon carbide.

35. The method of claim 33, wherein the passivation layer comprises silicon nitride.

36. The method of claim 33, wherein the passivation layer has a thickness of between approximately 2,000 and 3,000 angstroms.