WO2002048023A2

WO2002048023A2 - Method for improving the polysilicon structures of a mems device by masking to inhibit anodic etching of the mems polysilicon structures

Info

Publication number: WO2002048023A2
Application number: PCT/US2001/051334
Authority: WO
Inventors: John Gritters; Michael J. Sailor
Original assignee: Omm, Inc.
Priority date: 2000-10-25
Filing date: 2001-10-25
Publication date: 2002-06-20
Also published as: WO2002048023A3

Abstract

A method is provided for fabricating a MEMS device on a workpiece by forming a mercaptain mask (306) on a gold structure (309). The mask (306) is used to inhibit anodic etching of polysilicon structures (303) during the acid etch process that is used to remove the oxide dielectric layer from the workpiece to expose the polysilicon structures of the MEMS device (303) to allow their movement. The mercaptain can be utilised to adhere to the exposed gold surface (309) to form a self-mask (306) on the gold surface (309). As such, a workpiece having numerous gold surfaces, such as numerous optomechanical switches, each having various types of gold structures, can be placed in a mercaptain solution. The mercaptain selectively coats the gold surfaces to form self-adhering mercaptain masks on all the exposed gold surfaces.

Description

METHOD FOR IMPROVING THE POLYSILICON STRUCTURES

OF A MEMS DEVICE BY MASKING TO INHIBIT ANODIC ETCHING

OF THE MEMS POLYSILICON STRUCTURES

BACKGROUND

Microelectromechanical systems or MEMS have electro-mechanical structures typically sized on a millimeter scale or smaller. These structures are used in a wide variety of applications including for example, sensing, electrical and optical switching, and micron scale (or smaller) machinery, such as robotics and motors. Because of their small size, MEMS devices may be fabricated utilizing semiconductor production methods and other microfabrication techniques such as thin film processing utilizing lithographic techniques. Once fabricated, the MEMS structures are assembled to form MEMS devices.

For optical switching, structures can be built which have a mirrored surface on a movable structure for reflecting a light beam received from a sending fiber to a selected one of several receiving fibers, to another switch, to a sensor, or the like. These types of structures are generally known as optomechanical switches. Optomechanical switches can employ any of a variety of configurations. A few examples of optomechanical switches are shown in: U.S. Patent Application Serial No. 09/063,664, filed on April 20, 1998, by Li Fan, entitled MICROMACHINED OPTOMECHANICAL SWITCHES, issued as U.S. Patent No. , on ; U.S. Patent Application Serial No. 09/483,268, filed on

January 13, 2000, by Fan, et al., entitled MICROMACHINED OPTOMECHANICAL

SWITCHING DEVICES, issued as U.S. Patent No. , on ; U.S.

Patent Application Serial No. , filed on , by Li Fan, entitled

MEMS OPTICAL SWITCH WITH A NOTCHED LATCHING APPARATUS FOR IMPROVED MIRROR POSITIONING AND METHOD OF FABRICATION THEREOF, issued as U.S. Patent No. , on ; and U.S. Application Serial No. , by Li Fan, entitled MEMS OPTICAL SWITCH WITH TORSIONAL HINGE

AND METHOD OF FABRICATION THEREOF, issued as U.S. Patent No. , on , all herein incorporated by reference in their entireties. MEMS devices typically have force bearing structures. That is, structures that communicate or sustain mechanical forces which are developed external to or generated by the device. MEMS devices are fabricated on a substrate, typically silicon, with thin film deposition and etch techniques. In silicon MEMS devices, the force bearing structures can be formed of polycrystalline silicon, sometimes referred to as polysilicon. Uniformity of these structures is important, and sometimes critical to the reliability of the device.

For example, optomechanical switches, such as the switch 100 shown in Fig. 1 A for illustration purposes, can employ a spring or torsional structure to bias a switch structure into a desired position. Electrical fields then may be used to actuate, for example, the mirror 120, from a spring biased position to a second position to alter the path of the light signal. In the case of Fig. 1 A, the mirror 120 is actuated into and out of the path of the light signal. It has been discovered that the required actuation voltage to overcome the spring constant can vary from production lot to production lot, or even from device to device. Further, it has been discovered that the force bearing structures, such as the spring 110, in the example of Fig. 1 A, can have varied maximum force bearing capabilities and fatigue resistance. This increases the failure rate and reduces the predictability of devices.

What is needed is a manufacturing process that optimizes device performance and provides more uniform device characteristics.

SUMMARY

In a possible implementation in accordance with the present invention, a method for fabricating a MEMS device on a workpiece is provided to include forming a mask over a metallic surface, etching a dielectric layer from the workpiece to expose a polysilicon comprising structure, and removing the mask from the metallic comprising surface. With such a method, it is possible to inhibit anodic etching of the polysilicon structures of the MEMS device.

By masking the metallic surface during etching of the polysilicon structures, the material properties such as uniformity, strength, and fatigue capabilities can be improved to provide better MEMS structures. This allows better structural uniformity, mechanically stronger parts, and better reliability and yields. Further, in the example of the MEMS optical switch, it can improve actuation voltage control allowing more consistent turn on, and turn off, voltage requirements. In a possible implementation in accordance with the present invention, a method is provided for fabricating a MEMS device on a workpiece by forming a mask on a gold structure using a sulfur compound, such as a mercaptain. The mask is used to inhibit anodic etching of polysilicon structures during the acid etch process that is used to remove the oxide layer from the workpiece and expose the polysilicon structures of the MEMS device to allow their movement.

The mercaptain can be utilized to adhere to the exposed gold surface to form a self- mask on the gold surface. As such, a workpiece having numerous gold surfaces, such as numerous optomechanical switches, each having various types of gold structures can be placed in a mercaptain solution. The mercaptain selectively coats the gold surfaces to form self-adhering mercaptain masks on all the exposed gold surfaces. Any excess mercaptain on non-gold surfaces can be removed with a short rinse while leaving the mercaptian mask.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 A shows an example of a MEMS optomechanical switch device.

Fig. IB shows a top view of the MEMS optomechanical switch device of Fig. 1A as partially fabricated. Fig. 2 illustrates a possible implementation in accordance with the present invention.

Fig. 3 illustrates an MEMS structure formed in accordance with the present invention.

Fig. 4 illustrates an MEMS structure formed in accordance with the present invention. Fig. 5 illustrates a possible implementation in accordance with the present invention.

Fig. 6 illustrates a possible implementation in accordance with the present invention.

DESCRIPTION

As part of a typical fabrication process of MEMS devices, polysilicon structures are defined in layers by thin film process. Such a process typically includes surrounding, partially or completely, the structural parts of the device with a dielectric, typically an oxide, such as silicon dioxide. As part of fabrication, the oxide portion is removed to expose the parts and allow their movement. Removal of the oxide can be performed with an acid etch process. For example, silicon dioxide may be removed with a hydrofluoric acid etch. With some MEMS devices, such as with the optomechanical switch 100 shown in

Fig. 1 A for example purposes, some assembly is required after the oxide etch process. Fig. IB shows a further example for illustration purposes, of a top view of the optomechanical switch 100 of Fig. 1 A prior to assembly.

It has been discovered that etching of the oxide layer can cause polysilicon structures to degrade under certain circumstances. In the case of force bearing structures, the material properties, such as strength and fatigue resistance, diminsh. Among other problems, this causes mechanically weaker parts, changes spring constants, and can lead to breakage. Further, it can lead to changes in the electrical properties of polysilicon E-field generating structures, including structures used to communicate the actuation voltage. This presents a reliability problem and, in the example of the MEMS optomechanical switch, creates difficulty in controlling the actuation voltage. Thus, the turn on and turn off voltage requirements vary.

Moreover, it has been discovered that etching of the oxide layer can cause visual coloration changes in the polysilicon, sometimes resulting in rejection of devices based on visual inspection. MEMS devices typically have structures having metallic material such as bond pads, interconnect lines, and, in the case of MEMS optical switches, a large mirrored surface. The relatively large size of the surface area of the mirror surface gives rise to a significant electrochemical reaction during etching. The mirror structure typically has a metallic mirror surface deposited over a polysilicon backing. The mirror surface can be deposited directly on the polysilicon. Or, the gold can be deposited on some other metallic or semi-metallic material that is deposited on the polysilicon to enhance the deposition characteristics of the mirror material.

The mirrored surface of the optomechanical switch can be any well known sufficiently reflective material, such as aluminum or gold. The material of the mirror is selected to have good reflective properties at the transmission frequency. With the optomechanical switch, gold is preferred for use with infrared frequency light, which is commonly used in fiber optic transmission lines. Gold is also sometimes used to form the interconnect lines, bond pads, and/or other structures typically formed with metallic material. The presence of the gold on the mirror and elsewhere causes galvanic action to arise during the acid etch used to expose the polysilicon structures. The galvanic action results in anodic etching of the polysilicon structures during the acid etch process. The galvanic action results from the gold being in electrical contact with the polysilicon structures of the device. The ratio of the exposed surface area of the. gold to the exposed polysilicon area determines the size of the galvanic cell, and thus determines how much voltage and current that can be developed. This voltage drives the acid to anodically etch the polysilicon, degrading its properties. h the case of the optomechanical switch referenced above, the torsional spring structure, which affixes the actuated portions of the switch to the substrate and provides a pivot point therebetween, can become severely anodically etched. This in turn weakens the spring. Furthermore, it also has been observed that the electrical pads used to actuate the switch also can be severely anodically etched. Anodically etched pads can change the characteristics of the actuation E-field communicated by the pad.

Turning to Fig. 2, in one implementation 200 of the present invention, to inhibit the deleterious effects resulting during the oxide dielectric removal, gold surfaces are masked 210. Then, the dielectric is etched to expose a polysilicon structure 220. After the etch, the gold coat is removed 230.

Fig. 3 illustrates a metallic structure 309 coupled to a polysilicon layer 303. The metallic structure maybe an electrode, bond pad, a lead, a via, a contact, a cladding surface or structure, a reflective structure, or other structure typically formed of conductive metals. The mask 306 is formed to cover the otherwise exposed surfaces of a metallic structure 309. The mask 306 inhibits the acid from coming into contact with the metallic structure during the etch process and thus inhibits the electrochemical cell f om forming between the metallic structure and the polysilicon layer 303.

The mask maybe formed of a sulfur compound, such as for example, an organosulfur compound, which can be a mercaptain. A mercaptain is a group of organosulfur compounds that are derivatives of hydrogen sulfide in the same way that alcohols are derivatives of water. Mercaptains such as 1-Decanethiol, 1-Octanethiol, or the like, may be utilized to form the mask. Mercaptains are available from Aldrich Chemical Company, of Milwaukee, Wisconsin. Mercaptains adhere particularly well to non-oxide containing metallic surfaces such as a gold surface. It is anticipated that mercaptains also could be used to form masks on structures formed of other noble metals as well.

In addition to mercaptains, other sulfur based compounds may be employed to mask noble metals. For example, it is contemplated that thioether, or compounds which have a sulfur atoms near the end of a molecule chain could be used as a masking agent. Further, it is contemplated that carbon based compounds, such as isocyanides, isocyanates, isonitrile, thiocyanates, or other carbon compounds which have a carbon atoms near the end of a molecule chain to provide adhesion properties to noble metals could be employed. Also, although not presently preferred, it is expected that selenium compounds or telurim compounds could be utilized.

It also is contemplated that in some implementations the mask 306 could be formed of photoresist to cover the metallic structure 309. This is provided that the photoresist mask can provide adequate protection during the desired duration of the acid etch process. For example, the photoresist mask must adhere well enough to the metallic structure without lifting off during the acid etch process used to release the structures of the MEMS devices.

The mask 306 can be employed in some emodiments to cover all the exposed surfaces of the metallic structure 309, such as the top and side walls 309a & 309b. This minimizes the amount of surface area exposed to the acid solution during etch. In the case of a gold mirror structure, the mercaptain adheres to the exposed gold surface to form a self-mask on the gold surface. As such, a workpiece having numerous optomechanical switches, each having various types of gold structures, can be placed in a mercaptain solution and the mercaptain will selectively coat the gold surfaces, forming self- adhering mercaptain masks on all the exposed gold surfaces. Any excess mercaptain on non-gold surfaces can be removed with a short rinse as is discussed further below.

An optional intermediate material 311 can be disposed between the metallic layer 309 and the polysilicon layer 303. In one implementation of the optomechanical switch discussed above, an intermediate layer 311 of TiW can be used to provide better adhesion of a gold mirror metallic layer 309 to a polysilicon layer 303 that is used as a mirror backing. Turning to Fig. 4, the intermediate layer 411, however, may be a material that forms an oxide passivation layer 416, such as, for example Cr. Such a material has an oxide layer 416, i.e. CrO₃, on the exterior walls of the Cr which is not striped during the acid etch process. As such, an oxide mask 416 exists on the sidewalls of intermediate layer 411 during the etch process, inhibiting galvanic action between the intermediate layer 411 and the polysilicon structures of the device. This further reduces the anodic etching of the polysilicon structures of the device. Although the mask 306 of Fig. 3 could be made to cover the intermediate layer in some embodiments, it is not necessary with Cr or the like. Referring to Fig. 3, it is also contemplated that the intermediate layer 311 could be formed of a dielectric material to inhibit electrical connection between the metallic structure 309 and the polysilicon layer 303 so as to inhibit anodic etching of the polysilicon. This may be possible with some metallic structures, where electrical connection to the polysilicon structures is not necessary. One example is the reflective mirror of the optomechanical switch discussed above. If a dielectric intermediate layer 311 were used, anodic etching of polysilicon structures would be inhibited without using the mask 306. In such an implementation, however, the dielectric material of the intermediate layer 311 should be inhibited from etching along with the dielectric oxide layer that is intentionally being removed. This is to insure that the reflective mirror material is not undercut to the point of causing it to lift off, compromising its integrity, reducing its reflective properties, or diminishing its reliability.

Fig. 5 shows one possible implementation 500 utilizing the mercaptain mask. Sometimes MEMS devices will have a photoresist layer present on the workpiece after the deposition process has been completed. If so, the photoresist is striped 505, usually with acetone, such as with a 3 to 5 second acetone rinse, followed by a 5 minute acetone soak in a glass container, followed by a 3 to 5 second acetone rinse.

After removal of any resist 505, if present, a pre-clean 507 is performed prior to forming the mercaptain mask. The preclean can be performed with a 5 minute soak in an alcohol solution in the glass container. The pre-clean 507 can be performed with the diluent used to form the mercaptain solution, such as with ethanol, or isopropyl alcohol.

After the pre-clean, a mercaptain solution, such as mercaptian in alcohol diluent, is applied to the workpiece 510. A 1-Decanethiol (96%) mercaptain can be utilized. Preferably, the workpiece is exposed to a solution with greater than about 8% solution of 1- Decanethiol (96%) in isopropyl alcohol, such as about 10% solution of 1-Decanethiol (96%>) in isopropyl alcohol, for about 5 minutes. It is possible to use less than about 8% of 1- Decanethiol (96%), and to use longer durations. A greater than about 8% of 1-Decanethiol (96%) solution, however, provides in a 5 minute period, a sufficient amount of coating on the gold surfaces to ensures sufficient integrity of the mask coating. As discussed above, alcohols conveniently can be used as the diluent for application of mercaptain. For example, isopropyl, ethyl, or other alcohol can be used as the diluent. In addition, it is contemplated that other diluents, which will not attack the structures of the workpiece, can be used. For example, petroleum ether, or other organic diluents capable of solubilizing sulfur compounds, could be utilized. Mercaptains also could be solubilized with inorganic solutions. For example, supercritical CO2 could be employed as a diluent for a solvent based application. In addition, gas vapor transport is a possible alternative to solution based application of mercaptain or other mask compound.

An alcohol rinse 515 may be performed after the application of the mercaptain to the gold surfaces to rinse away any excess mercaptain. The duration of the alcohol rinse 515 should be limited so that a sufficient coating of mercaptain remains on the gold surfaces. The alcohol rinse 515 maybe a 2 minute rinse followed by another 3 minute rinse with isopropyl alcohol. Mercaptain can clump or ball in water based solutions such as acid. As a mercaptain solution can be viscous, the rinse helps to remove any excess mercaptain left on non-gold surfaces. This will help to prevent formation on the oxide surfaces of clumps which can cause non-uniform etching of the oxide.

Next, the acid etch of the oxide layer to release the MEMS structures 520 can be performed. The acid etch may be a hydrofluoric acid bath, or other acid bath, in a TEFLON container. The mask formed on the gold, or other metallic surface, inhibits formation of a galvanic cell between the metallic surface and the polysilicon structures of the MEMS device. Thus, anodic etching of the polysilicon structures is inhibited during the acid etch of the oxide layer. After the acid etch, an alcohol rinse can be performed to remove any remaining acid from the acid etch process and to remove the mercaptain mask 530. Multiple separate rinses may be performed to improve removal of the mercaptain mask. For, example 3 separate 5 minute rinses using isopropyl alcohol with deionized water may be performed to remove the mercaptain f om the gold surfaces and wash away any remaining mercaptain clumps. Mild agitation may be used to facilitate removal of the mask material from the non-gold surfaces.

Although a rinse process could be used to remove all of the mercaptain from the gold surfaces, a short alcohol rinse process, such as discussed above, may be used to deplete the mercaptain mask, but not completely remove it. The short alcohol rinse process may be used to substantially remove the mercaptian mask, leaving a residual mercaptain film remaining. The remaining mercaptain film can be removed with an O₂ plasma etch, such as with an RF plasma, or with an ozone clean, such as by generating ozone with a ultra-violet light. Turning to Fig. 6, a 5 minute trichloroethylene rinse may be performed after the alcohol rinse 640. The trichloroethylene rinse removes the alcohol prior to it drying. This is done to inhibit a carbon residue that otherwise would form on surfaces as a result of drying the alcohol from the workpiece. Carbon residue could cause undesirable stiction between contacting surface of the device. A vacuum bake 650 may be performed after the trichloroethylene rinse to remove the trichloroethylene.

As an alternative to the trichloroethylene rinse and vacuum bake process, a super critical dry process could be used. Such a process is known in the art and employs CO₂ near its triple point which is "evaporated" from the surface rather than baked dry. In such a process, the CO₂ would displace the alcohol and inhibit residue from forming on the device surfaces.

Removal of any residual mercaptain that may remain on the gold surfaces after the alcohol rinse 530, can be performed after the workpiece has been dried. As such, an O₂ plasma etch, or an ozone clean, may be performed anytime after a vacuum bake, a super critical dry process, or other drying process.

While the preferred methods and embodiments of the present invention have been described in detail above, many changes to these embodiments may be made without departing from the true scope and teachings of the present invention. The present invention, therefore, is limited only as claimed below and the equivalents thereof.

Claims

WHAT IS CLAIMED IS:

1. A method for fabricating a microelectromechanical device on a workpiece, the method comprising: a) forming a mask over a metallic comprising surface; b) etching a dielectric layer from the workpiece to expose a polysilicon comprising structure; and c) removing the mask from the metallic comprising surface.

2. The method of Claim 1 wherein forming the mask comprises forming a mask on a gold comprising surface.

3. The method of Claim 2 wherein forming the mask comprises depositing a sulfur comprising layer.

4. The method of Claim 3 wherein depositing the sulfur comprising layer comprises depositing a mercaptain.

5. The method of Claim 4 wherein depositing the sulfur comprising layer comprises using an aqueous solution comprising alcohol.

6. The method of Claim 5 wherein etching comprises acid etching an oxygen comprising layer.

7. The method of Claim 6 wherein etching comprises etching silicon dioxide using hydrofluoric acid.

8. The method of Claim 2 wherein etching comprises etching an oxygen comprising layer.

9. The method of Claim 8 wherein etching comprises etching silicon dioxide.

10. The method of Claim 9 wherein etching comprises acid etching.

11. The method of Claim 3 wherein depositing the sulfur comprising layer comprises using an aqueous solution comprising greater than about 8% mercaptain.

12. The method of Claim 11 wherein depositing the sulfur comprising layer comprises exposing the gold comprising surface to the aqueous solution for about 5 minutes.

13. The method of Claim 3 wherein depositing the sulfur comprising layer comprises using an aqueous solution comprises about 10% mercaptain.

14. The method of Claim 13 wherein depositing the sulfur comprising layer comprises exposing the gold comprising surface to the aqueous solution for about 5 minutes.

15. The method of Claim 14 further comprising etching the dielectric layer substantially without anodically etching the polysilicon comprising structure.

16. The method of Claim 3 wherein depositing the sulfur comprising layer comprises exposing the workpiece to the mercaptian in an alcohol diluent.

17. The method of Claim 16 wherein exposing the workpiece comprises exposing the workpiece to the mercaptian in a diluent comprising at least one of ethanol or isopropyl alcohol.

18. The method of Claim 3 wherein depositing the sulfur comprising layer comprises exposing the workpiece to an aqueous solution comprising sulfur and a diluent, and further comprising rinsing the workpiece with the diluent after exposing the workpiece to the aqueous solution and prior to etching, wherein rinsing is performed such that a sulfur comprising layer is maintained on the gold comprising surface.

19. The method of Claim 18 further comprising agitating the workpiece while rinsing.

20. The method of Claim 19 wherein depositing the sulfur comprising layer comprises exposing the workpiece to a mercaptain in an alcohol diluent, and wherein rinsing comprises exposing the workpiece to an alcohol comprising solution for about 5 minutes.

21. The method of Claim 20 wherein rinsing comprises performing at least two separate rinses comprising an about 2 minute rinse and an about 3 minute rinse.

22. The method of Claim 3 wherein removing the mask comprises depleting the sulfur comprising layer, and further comprising rinsing the device with trichloroethylene after depleting the sulfur comprising layer and prior to drying the device.

23. The method of Claim 22 wherein depleting the sulfur comprising layer comprises rinsing with an alcohol comprising solution.

24. The method of Claim 23 wherein removing the sulfur comprising layer further comprises using one of an oxygen comprising plasma etch or an ozone clean process.

25. The method of Claim 24 wherein depositing the sulfur comprising layer comprises depositing a mercaptain in a solution comprising alcohol.

26. The method of Claim 3 further comprising performing a super critical dry process after removing the sulfur comprising layer.

27. The method of Claim 26 wherein removing the sulfur comprising layer comprises rinsing with an alcohol comprising solution.

28. The method of Claim 27 wherein depositing the sulfur comprising layer comprises depositing a mercaptain in a solution comprising alcohol.

29. The method of Claim 28 wherein removing the sulfur comprising layer further comprises using one of an oxygen comprising plasma etch or an ozone clean process.

30. The method of Claim 3 wherein removing the sulfur comprising layer comprises: a) rinsing with an alcohol comprising solution; and b) performing one of an oxygen comprising plasma etch or an ozone clean process.

31. The method of Claim 3 wherein depositing a sulfur comprising layer comprises covering a sidewall of a gold comprising structure.

32. The method of Claim 3 wherein depositing a sulfur comprising layer comprises covering a plurality of gold comprising surfaces.

33. The method of Claim 3 further comprising etching the dielectric layer essentially without anodically etching the polysilicon comprising structure.

34. The method of Claim 1 wherein forming the mask comprises covering an exposed gold comprising surface with a temporary mercaptain mask, and wherein etching the dielectric comprises etching an oxygen comprising dielectric layer from the workpiece to expose the polysilicon comprising structure.

35. The method of Claim 34 wherein covering exposed the surface comprises covering a top surface and sidewalls of the gold comprising structure.

36. The method of Claim 35 wherein covering exposed surface comprises covering all gold comprising structures.

37. The method of Claim 34 further comprising etching the oxygen comprising layer essentially without anodically etching the polysilicon comprising structure.

38. The method of Claim 34 wherein coyering the exposed surface comprises covering a mirror.

39. The method of Claim 38 wherein etching comprises exposing a torsional spring structure.

40. The method of Claim 1 wherein etching comprises exposing a force bearing structure.

41. The method of Claim 40 wherein etching comprises exposing a spring structure.

42. The method of Claim 1 further comprising depositing a gold comprising layer over a chromium comprising layer to form a metallic comprising structure having the metallic comprising surface.

43. A method for fabricating a microelectromechanical device on a workpiece, the method comprising: a) forming a mask consisting essentially of mercaptain on a gold comprising structure; and b) etching an oxygen comprising dielectric layer from the workpiece to expose a polysilicon comprising structure using the mask.

44. The method of Claim 43 wherein forming the mask comprises forming a mask that covers a top surface and sidewalls of the gold comprising structure.

45. The method of Claim 43 wherein forming the mask comprises covering all gold comprising structures.

46. The method of Claim 43 wherein forming the mask comprises using greater than about 8% mercaptain in diluent.

47. The method of Claim 46 wherein forming the mask comprises using greater than about 8% mercaptain in alcohol diluent.

48. The method of Claim 47 wherein forming the mask comprises exposing the gold comprising structure to the greater than about 8% mercaptain in alcohol diluent for about 5 minutes.

49. The method of Claim 46 wherein etching comprises acid etching.

50. The method of Claim 49 wherein etching comprises etching silicon dioxide with hydrofluoric acid.

51. The method of Claim 49 further comprising rinsing the workpiece with the diluent after forming the mask, and wherein rinsing is performed prior to etching and such that a mercaptain comprising layer is maintained on the gold comprising structure.

52. The method of Claim 51 comprising removing the mask from the gold comprising structure after etching.

53. The method of Claim 52 wherein removing the mask after etching comprises using the diluent.

54. The method of Claim 53 wherein removing the mask from the gold comprising structure further comprises using one of an oxygen comprising plasma etch process or an ozone clean process.

55. The method of Claim 52 further comprising agitating the workpiece while rinsing.

56. The method of Claim 53 wherein removing the mask comprises rinsing with an alcohol comprising solution, and further comprising rinsing the device with trichloroethylene prior to drying the device.

57. The method of Claim 53 further comprising performing a super critical dry process after using the diluent.

58. The method of Claim 43 comprising removing the mask from the gold comprising structure after etching comprising: a) rinsing with an alcohol comprising solution; and b) using one of a plasma etch process or an ozone clean process.

59. The method of Claim 58 further comprising drying the device prior to using one of a plasma etch process or an ozone clean process, and comprising one of: (1) rinsing the device with trichloroethylene and drying the device with a vacuum bake process, or (2) performing a super critical dry process.

60. The method of Claim 43 wherein forming the mask comprises using about 10% mercaptain in diluent.

61. The method of Claim 60 wherein forming the mask comprises using about 10% mercaptain in alcohol diluent.

62. The method of Claim 61 wherein forming the mask comprises exposing the gold comprising structure to about 10% mercaptain in alcohol diluent for about 5 minutes.

63. The method of Claim 62 wherein forming the mask comprises using about 10% mercaptain in at least one of ethanol or isopropyl alcohol diluent.

64. The method of Claim 43 wherein etching comprises exposing a force bearing structure.

65. The method of Claim 64 wherein etching comprises exposing a spring structure.

66. The method of Claim 43 further comprising forming the gold comprising structure by depositing a gold comprising layer over a chromium comprising layer.

67. A method for fabricating an optical switching device comprising a plurality of electromechanical optical switches on a workpiece, the method comprising: a) presoaking the workpiece in an alcohol comprising solution; b) forming a mercaptain mask covering a gold comprising surfaces of mirror structures of the plurality of electromechanical optical switches comprising:

(i) soaking the workpiece in a solution comprising greater than about 8% mercaptain in alcohol diluent to allow mercaptian to adhere to the gold comprising surfaces of the minor structures; and (ii) rinsing the workpiece in an alcohol comprising solution after soaking to remove excess mercaptain on non-gold comprising surfaces; c) acid etching an oxygen comprising dielectric layer encasing the plurality of optical switches to expose polysilicon comprising structures so as to allow assembly of the plurality of switches and comprising using the mercaptain mask so as to etch essentially without anodically etching polysilicon force bearing structures of the plurality of switches; and d) removing the mask from the gold comprising surface comprising: (i) rinsing the workpiece with an alcohol comprising solution; and (ii) performing one of an oxygen comprising plasma etch process or an ozone clean process.

68. The method of Claim 67 wherein soaking the workpiece comprises soaking for about 5 minutes.

69. The method of Claim 67 wherein acid etching comprises hydrofluoric acid etching of silicon dioxide.

70. The method of Claim 67 further comprising at least one of: (a) rinsing the device with trichloroethylene after exposing the device to the alcohol comprising solution to remove the mask so as to remove the alcohol comprising solution used to remove the mask prior to drying the device, or (b) performing a super critical dry process after exposing the device to the alcohol comprising solution to remove the mask so as to remove the alcohol comprising solution used to remove the mask from the surface of the device.

71. The method of Claim 67 further comprising forming the gold comprising surface of the mirror structures over a chromium comprising intermediate layer.

72. A method for fabricating a microelectromechanical device comprising polysilicon, the method comprising: a) forming a metallic comprising structure; b) performing an acid etch to expose a polysilicon structure; and c) inhibiting anodic etching of the polysilicon structure during the acid etch.

73. The method of Claim 72 comprising inhibiting anodic etching of a polysilicon force bearing structure.

74. The method of Claim 73 comprising inhibiting anodic etching of a polysilicon spring structure.

75. The method of Claim 74 wherein forming a metallic comprising structure comprises forming a structure having a gold comprising surface, and wherein inhibiting anodic etching of the polysilicon spring structure comprises coating the gold comprising surface with a mercaptain mask prior to performing the acid etch.

76. The method of Claim 72 wherein inhibiting anodic etching comprises forming a mask over the metallic comprising structure prior to performing the acid etch.

77. The method of Claim 76 wherein forming a metallic comprising structure comprises forming a structure having a gold, comprising surface, and wherein inhibiting anodic etching comprises coating the gold comprising surface with a mercaptain.

78. The method of Claim 77 further comprising forming an intermediate layer of chromium on a polysilicon surface electrically coupled to the polysilicon structure, the gold comprising surface being formed on the intermediate layer of chromium.

79. A method for fabricating a microelectromechanical device with reduced stiction, the method comprising rinsing the device with trichloroethylene after exposing the device to an alcohol comprising solution so as to remove the alcohol comprising solution prior to drying the device.

80. The method of Claim 79 further comprising drying the device comprising vacuum baking the device to remove the trichloroethylene.

81. A method for processing a microelectromechanical device with reduced stiction, the method comprising performing a super critical dry process after exposing the device to an alcohol comprising solution so as to remove the alcohol comprising solution from the surface of the device.