Fabrication of microstructures with vacuum-sealed cavity

• US 20030217915A1
• Filed: 05/24/2002
• Published: 11/27/2003
• Est. Priority Date: 05/24/2002
• Status: Active Grant

• Current Assignee: Teledyne Digital Imaging, Inc. (Teledyne Technologies Incorporated)
• Original Assignee: Dalsa Semiconductor Inc (Teledyne Technologies Incorporated)
• Inventors: Tremblay, Yves, Ouellet, Luc, Antaki, Robert
• Granted Patent: US 6,902,656 B2
• Time in Patent Office: Days
• US Class Current: 204/192.15
• CPC Class Codes: B22F 1/0655 Hollow particles
• CPC Class Codes: B81C 1/00325 for reducing stress inside of the package structure
• CPC Class Codes: B81C 2201/0167 by adding further layers of materials having complementary strains, i.e. compressive or tensile strain
• CPC Class Codes: C23C 14/0021 Reactive sputtering or evaporation
• CPC Class Codes: C23C 14/0641 Nitrides C23C14/0617 takes precedence
• CPC Class Codes: C23C 14/228 Gas flow assisted PVD deposition
• CPC Class Codes: C23C 14/325 Electric arc evaporation
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details

Abstract

A cavity forming formed in an encapsulation structure under a vacuum in a vacuum chamber is sealed with a capping layer. A stiff protective layer under tensile stress is deposited on the capping layer prior to venting the vacuum chamber to atmospheric pressure. The capping layer is preferably aluminum or an aluminum alloy, and the protective layer is preferably δ-TiN having a suitable high Young'"'"'s modulus.

Claims

1. A method of fabricating a microstructure with a vacuum-sealed cavity, comprising the steps of:

fabricating said cavity in an encapsulation structure under a vacuum in a vacuum chamber;

sealing said cavity with a capping layer; and

depositing a stiff high Young'"'"'s modulus protective layer under tensile stress on said capping layer prior to venting said vacuum chamber to atmospheric pressure.

2. A method as claimed in claim 1, wherein said capping layer is aluminum or an aluminum alloy deposited at a temperature of in the range 100 to 600°

C.

3. A method as claimed in claim 2, wherein said capping layer is deposited at about 450°

C.

4. A method as claimed in claim 2, wherein said stiff protective layer is titanium nitride.

5. A method as claimed in claim 4, wherein said titanium nitride is deposited at a maximum temperature of about 500°

C.

6. A method as claimed in claim 5, wherein said titanium nitride is deposited by reactive sputtering.

7. A method as claimed in claim 6, wherein said titanium nitride is single phase δ

-TiN deposited at a temperature of less than about 400°

C.

8. A method as claimed in claim 7, wherein the thickness of said titanium nitride layer lies in the range of 0.2 to 0.7 μ

m.

9. A method as claimed in claim 8, wherein the thickness of said titanium nitride layer lies in the range of 0.2 to 10.0 μ

m.

10. A method as claimed in claim 9, wherein the thickness of said titanium nitride layer lies in the range of 0.7 μ

m.

11. A method as claimed in claim 9, wherein the thickness of said aluminum or aluminum alloy layer lies in the range 0.2 to 20 μ

m.

12. A method as claimed in claim 11, wherein the thickness of said aluminum or aluminum alloy layer is about 2.0 μ

m.

13. A method as claimed in claim 1, wherein said capping layer is selected from the group consisting of an aluminum alloy, wherein said aluminum is alloyed with an element selected from the group consisting of copper, silicon, titanium, and palladium.

14. A method as claimed in claim 1, wherein said capping layer is selected from the group consisting of copper, gold and silver.

15. A method as claimed in claim 14, wherein said capping layer is a flowable dielectric capable of reflow at a temperature of less than about 500°

C.

16. A method as claimed in claim 15, wherein said capping layer is selected from the group consisting of high doping content borosilicates, arsenosilicates, and germanosilicates.

17. A method as claimed in claim 1, wherein said cavity is subjected to degassing prior to capping with said capping layer.

18. A method as claimed in claim 17, wherein said microstructure is cooled to room temperature after deposition of said protective layer prior to exposure to the atmosphere.

19. A method as claimed in claim 1, wherein said protective layer is selected from the group consisting of Titanium aluminonitride, TiAlN;

Molybdenum silicide, MoSi₂;

Titanium carbide, TiC;

Silicon carbide, SiC;

Tungsten, W;

Aluminum nitride, AlN;

Titanium aluminide, TiAl;

Molybdenum, Mo;

Tantalum, Ta;

Platinum, Pt;

Tungsten silicide, WSi₂;

Titanium, Ti;

Gold, Au.

20. A method as claimed in claim 1, wherein said encapsulation structure is polysilicon.

21. A method as claimed in claim 20, wherein said encapsulation structure is selected from the group consisting of titanium, titanium nitride, silicon nitride, tungsten, titanium tungsten, or combinations thereof.

22. A method of fabricating a microstructure with a vacuum-sealed cavity, comprising the steps of:

fabricating said cavity in an encapsulation structure under a vacuum in a vacuum chamber;

sealing said cavity with a capping layer of aluminum or aluminum alloy deposited at a maximum temperature of 500°

C.; and

depositing in-situ a stiff high Young'"'"'s modulus protective layer of titanium nitride under tensile stress at a maximum temperature of 500°

on said capping layer prior to venting said vacuum chamber to atmospheric pressure.

23. A method as claimed in claim 22, wherein said capping layer is deposited at a temperature of about 450°

C.

24. A method as claimed in claim 22, wherein said capping layer is single phase δ

-titanium nitride.

25. A method as claimed in claim 22, wherein said titanium nitride has a tensile stress lower than about 1000 Gpa.

26. A method as claimed in claim 22, wherein the tensile stress of said titanium nitride is about 300 Gpa.

27. A method as claimed in claim 26, wherein said encapsulation structure is polysilicon having a tensile stress of about 300 Gpa.

28. A method as claimed in claim 22, wherein said cavity is degassed prior to being sealed with said capping layer.

29. A method as claimed 28, wherein said microstructure is cooled to room temperature prior to venting said vacuum chamber to the atmosphere.

30. A microstructure having a vacuum-sealed cavity, comprising:

an encapsulation structure defining a cavity;

a capping layer sealingly closing said cavity; and

a stiff high Young'"'"'s modulus protective layer under tensile stress deposited on said capping layer prior.

31. A microstructure as claimed in claim 30, wherein said protective layer has a tensile stress of less than about 1000 Gpa.

32. A microstructure as claimed in claim 31, wherein said protective layer has a tensile stress of less than about 300 Gpa.

33. A microstructure as claimed in claim 31, wherein said capping layer is aluminum or aluminum alloy.

39. A microstructure as claimed in claim 30, wherein said protective layer is selected from the group consisting of titanium aluminonitride, Molybdenum silicide, Titanium carbide, Silicon carbide, Tungsten, Aluminum nitride, Titanium aluminide, Molybdenum, Tantalum, Platinum, Tungsten silicide, Titanium and Gold.

34. A microstructure as claimed in claim 34, wherein said protective layer is TiN.

36. A microstructure as claimed in claim 34, wherein said protective layer is δ

-TiN.

37. A microstructure as claimed in claim 36, wherein said protective layer has a thickness lying in the range 0.2 μ

m to 10 μ

m.

38. A microstructure as claimed in claim 37, wherein said protective layer has a thickness of about 0.7 μ

m.

40. A microstructure as claimed in claim 34, wherein said encapsulation structure is polysilicon.