Selective etching of MEMS using gaseous halides and reactive co-etchants

• US 20080032439A1
• Filed: 08/02/2006
• Published: 02/07/2008
• Est. Priority Date: 08/02/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Gousev, Evgeni, Yan, Xiaoming, Tung, Ming-Hau, Arbuckle, Brian
• Granted Patent: US 7,566,664 B2
• Time in Patent Office: Days
• US Class Current: 438/72
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 1/00595 Control etch selectivity
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

A method for etching a target material in the presence of a structural material with improved selectivity uses a vapor phase etchant and a co-etchant. Embodiments of the method exhibit improved selectivities of from at least about 2-times to at least about 100-times compared with a similar etching process not using a co-etchant. In some embodiments, the target material comprises a metal etchable by the vapor phase etchant. Embodiments of the method are particularly useful in the manufacture of MEMS devices, for example, interferometric modulators. In some embodiments, the target material comprises a metal etchable by the vapor phase etchant, for example, molybdenum and the structural material comprises a dielectric, for example silicon dioxide.

Claims

1. A method for fabricating a microelectromechanical systems device comprising:

contacting a microelectromechanical systems device with a vapor phase etchant comprising a gaseous halide and a co-etchant, wherein

the microelectromechanical systems device comprises a target material and a structural material;

the target material and the structural material are both etchable by the gaseous halide with an etching selectivity between the target material and the structural material of at least about 50;

1 in the absence of a co-etchant; and

the co-etchant is present in an amount effective to improve the etching selectivity between the target material and the structural material by at least about 2-times compared with the etching selectivity in the absence of the co-etchant.

2. The method of claim 1, wherein the gaseous halide comprises a compound selected from the group consisting of noble gas fluorides, interhalogen fluorides, interhalogen chlorides, NF₃, and combinations thereof.

4. The method of claim 1, wherein the target material comprises a metal.

5. The method of claim 4, wherein the metal is selected from the group consisting of titanium, zirconium, hafnium, vanadium, tantalum, niobium, molybdenum, tungsten, and combinations thereof.

6. The method of claim 5, wherein the metal comprises molybdenum.

7. The method of claim 1, wherein the structural material comprises a dielectric material.

8. The method of claim 7, wherein the dielectric material comprises SiO₂.

9. The method of claim 1, wherein the co-etchant comprises an oxygen-containing compound.

10. The method of claim 9, wherein the oxygen-containing compound is selected from the group consisting of O₂, O₃, ozonides, peroxides, peracids, superoxides, N_xO_y, S_xO_y, and combinations thereof.

11. The method of claim 10, wherein the oxygen-containing compound comprises O₂.

12. The method of claim 1, wherein the co-etchant comprises a nitrogen-containing compound.

13. The method of claim 12, wherein the nitrogen-containing compound is selected from the group consisting of amines, amides, azides, and combinations thereof.

14. The method of claim 1, wherein the co-etchant comprises a sulfur-containing compound.

15. The method of claim 14, wherein the co-etchant comprises an sulfur-containing compound selected from the group consisting of thiols, sulfides, thiones, thioic acids, carbon disulfide, OCS, and combinations thereof.

16. The method of claim 1, wherein a ratio between the co-etchant and etchant is at least about 1:

1.

17. The method of claim 16, wherein a ratio between the co-etchant and etchant is at least about 10:

1.

18. The method of claim 1, wherein the etching selectivity between the target material and the structural material of at least about 100:

1 in the absence of a co-etchant.

19. The method of claim 1, wherein the etching selectivity between the target material and the structural material in the presence of the co-etchant is at least 4-times the etching selectivity between the target material and the structural material in the absence of the co-etchant.

20. The method of claim 19, wherein the etching selectivity between the target material and the structural material in the presence of the co-etchant is at least 10-times the etching selectivity between the target material and the structural material in the absence of the co-etchant.

21. The method of claim 1, wherein a pressure of the vapor phase etchant is from about 0.5 torr to about 400 torr for at least a portion of the etching process.

22. The method of claim 1, wherein a temperature is from about 0°

C. to about 200°

C. for at least a portion of the etching process.

23. The method of claim 1, wherein the microelectromechanical systems device comprises an interferometric modulator, wherein

at least a portion of the target material is a sacrificial material that after etching defines a cavity, and

at least a portion of the structural material is a dielectric material disposed on a stationary electrode.

24. A microelectromechanical (MEMS) device fabricated by the method of claim 1.

3. The method of claim 3, wherein the gaseous halide is XeF₂.

25. A method for fabricating a microelectromechanical systems device comprising:

contacting a microelectromechanical systems device with a vapor phase etchant means and a co-etchant means, wherein

the microelectromechanical systems device comprises a metal target material and a structural material; and

the co-etchant means is present in an amount effective to improve an etching selectivity between the target material and the structural material by at least 2-times compared with an etching selectivity between the target material and the structural material in the absence of the co-etchant means.

26. A method for fabricating an interferometric modulator comprising:

contacting an unreleased interferometric modulator with a vapor phase etchant and a vapor phase co-etchant, wherein

the unreleased interferometric modulator comprises a sacrificial material in contact with a dielectric material, and

at least a portion of the sacrificial material when etched away forms a cavity; and

etching away substantially all of the at least a portion of the sacrificial material, wherein the co-etchant is present in an amount sufficient to improve the etching selectivity between the sacrificial material and the dielectric material by at least 2-times.

27. The method of claim 26, wherein the sacrificial material comprises a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, tantalum, niobium, molybdenum, tungsten, and combinations thereof.

28. The method of claim 27, wherein the sacrificial material comprises molybdenum.

29. The method of claim 26, wherein the vapor phase etchant comprises a gaseous halide selected from the group consisting of noble gas fluorides, interhalogen fluorides, interhalogen chlorides, NF₃, and combinations thereof.

30. The method of claim 29, wherein the vapor phase etchant comprises XeF₂.

31. The method of claim 26, wherein the vapor phase co-etchant comprises a compound selected from the group consisting of oxygen-containing compounds, nitrogen containing compounds, and sulfur containing compounds.

32. The method of claim 31, wherein the vapor phase co-etchant comprises O₂.

33. The method of claim 26, wherein:

the etching selectivity between the sacrificial material and the dielectric material in the absence of the co-etchant is at least 400;

1; and

the co-etchant is present in an amount sufficient to improve the etching selectivity between the sacrificial material and the dielectric material by at least 10-times.

34. The method of claim 26, wherein the etching away substantially all of the at least a portion of the sacrificial material is performed in a single etching cycle.