Methods for depositing, releasing and packaging micro-electromechanical devices on wafer substrates

• US 20050191790A1
• Filed: 04/07/2005
• Published: 09/01/2005
• Est. Priority Date: 12/07/2000
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Patel, Satyadev R., Huibers, Andrew G., Chiang, Steve S.
• Application Number:
  US11/102,295
• Publication Number:
  US 20050191790A1
• Time in Patent Office: Days
• US Class Current: 438/107
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 7/0077 Other packages not provided for in groups B81B7/0035 - B81B7/0074
• CPC Class Codes: B81C 1/00214 Processes for the simultaneaous manufacturing of a network or an array of similar microstructural devices
• CPC Class Codes: B81C 1/00333 Aspects relating to packaging of MEMS devices, not covered by groups B81C1/00269 - B81C1/00325
• CPC Class Codes: B81C 1/00896 Temporary protection during separation into individual elements
• CPC Class Codes: B81C 1/00904 Multistep processes for the separation of wafers into individual elements not provided for in groups B81C1/00873 - B81C1/00896
• CPC Class Codes: B81C 2203/0118 Bonding a wafer on the substrate, i.e. where the cap consists of another wafer
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/85 using a wire connector
• CPC Class Codes: H01L 2224/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01018 Argon [Ar]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/0102 : Calcium [Ca]
• CPC Class Codes: H01L 2924/01023 : Vanadium [V]
• CPC Class Codes: H01L 2924/01027 : Cobalt [Co]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/01054 : Xenon [Xe]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• CPC Class Codes: H01L 2924/01072 : Hafnium [Hf]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01077 : Iridium [Ir]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/04953 : TaN
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/10329 : Gallium arsenide [GaAs]
• CPC Class Codes: H01L 2924/12036 : PN diode
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/12044 : OLED
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/1433 : Application-specific integrated circuit [ASIC]
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/19042 : being an inductor
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding

Abstract

A method for forming a MEMS device is disclosed, where a final release step is performed just prior to a wafer bonding step to protect the MEMS device from contamination, physical contact, or other deleterious external events. Without additional changes to the MEMS structure between release and wafer bonding and singulation, except for an optional stiction treatment, the MEMS device is best protected and overall process flow is improved. The method is applicable to the production of any MEMS device and is particularly beneficial in the making of fragile micromirrors.

Claims

1. A spatial light modulator comprising:

a lower semiconductor substrate comprising circuitry and electrodes;

an upper transparent substrate bonded in spaced apart relationship to the semiconductor substrate;

a spacer layer between the semiconductor and transparent substrates for holding the semiconductor and transparent substrates bonded together in spaced apart relation and defining a gap between the semiconductor substrate and the transparent substrate;

a rectangular array of reflective mirrors disposed within the gap;

a light blocking rectangular mask disposed as a frame around the mirrors;

wherein the mirrors comprise substantially square mirror plates having edges that are neither perpendicular nor parallel to edges of the rectangular array and torsion hinges that allow the mirror plates to move relative to the upper and lower substrates; and

wherein an edge of the transparent wafer is bonded offset from an edge of the semiconductor substrate such that a bond pad area is exposed on a top surface of the semiconductor substrate.

2. The spatial light modulator of claim 1, wherein the semiconductor substrate is a silicon substrate.

3. The spatial light modulator of claim 2, wherein the torsion hinges have a thickness of 50 Å

to 2100 Å

.

4. The spatial light modulator of claim 1, wherein the electrodes are designed to run at 0-5 V.

5. The spatial light modulator of claim 2, comprising an SRAM cell at each mirror location.

6. The spatial light modulator of claim 1, that has XGA resolution.

7. The spatial light modulator of claim 2, wherein the substrates are bonded together with an adhesive.

8. The spatial light modulator of claim 7, wherein the substrates are bonded together with an epoxy.

9. The spatial light modulator of claim 5, wherein the mirrors comprise a stiction treatment.

10. The spatial light modulator of claim 1, wherein the torsion hinges are disposed in a different plane than the mirror plates.

11. The spatial light modulator of claim 10, wherein the mirrors are formed on the semiconductor substrate.

12. The spatial light modulator of claim 11, wherein the semiconductor substrate is a silicon substrate.

13. The spatial light modulator of claim 1, further comprising a getter and lubricant within the gap.

14. The spatial light modulator of claim 13, wherein substrates are anodic bonded together.

15. The spatial light modulator of claim 13, wherein the substrates are solder bonded together.

16. The spatial light modulator of claim 13, wherein the substrates are compression bonded together.

17. The spatial light modulator of claim 13, wherein the mirrors have an anti-striction layer.

18. The spatial light modulator of claim 1, wherein the gap between the upper and lower substrate is from 1 to 10 um.

19. The spatial light modulator of claim 7, wherein the adhesive is a UV cured adhesive.

20. The spatial light modulator of claim 8, wherein the epoxy is a LV cured epoxy.

21. The spatial light modulator of claim 1, wherein the mask is formed on an underside of the transparent substrate.

22. The spatial light modulator of claim 21, wherein the mask blocks visible light around a perimeter of the mirrors.

23. The spatial light modulator of claim 1, wherein bond wires are connected to the bond pads on the silicon substrate.

24. The spatial light modulator of claim 23, wherein the mirrors are provided in an array of between 1 and 6 million mirrors.

25. The spatial light modulator of claim 24, wherein the mirrors are disposed within a rectangular area.

26. The spatial light modulator of claim 1, wherein the circuitry is DRAM circuitry.

27. The spatial light modulator of claim 1, further comprising a getter disposed on the light transmissive substrate.

28. The spatial light modulator of claim 1, further comprising a lubricant within the gap which is an organic lubricant.

29. The spatial light modulator of claim 13, wherein the lower semiconductor substrate is held on a lower packaging substrate.

30. The spatial light modulator of claim 29, wherein a distance between the upper and lower substrate is from 1 to 250 microns.

31. The spatial light modulator of claim 1, further comprising a getter disposed within the gap.

32. The spatial light modulator of claim 31, wherein the getter is a moisture getter.

33. The spatial light modulator of claim 31, wherein the getter is a particle getter.

34. The spatial light modulator of claim 31, wherein the getter is a hydrogen getter.

35. The spatial light modulator of claim 31, wherein the getter is a metal oxide getter.

36. The spatial light modulator of claim 31, wherein the getter is a zeolite getter.

37. The spatial light modulator of claim 25, wherein the mirrors comprise a self assembled monolayer.

38. The spatial light modulator of claim 1, wherein the spacer layer is one or more intermediate substrates having an internal open area defining the gap.

39. The spatial light modulator of claim 28, further comprising a combination getter within the gap.

40. The spatial light modulator of claim 1, wherein the mirrors correspond to pixels in a direct-view or projection display.

41. The spatial light modulator of claim 13, wherein the number of mirrors is from 6,000 to about 6 million.

42. The spatial light modulator of claim 41, wherein the transparent substrate is glass.

43. The spatial light modulator of claim 30, wherein a group of the mirror edges of the mirrors is neither parallel nor perpendicular to the edges of the rectangular array area, and another group of the edges is parallel to rectangular array area edges.

44. The spatial light modulator of claim 1, wherein the mirror edges are approximately 45 degrees relative to the rectangular array area edges.

45. The spatial light modulator of claim 1, wherein no mirror edges are parallel or perpendicular to edges of the rectangular array area.

46. The spatial light modulator of claim 3, wherein each mirror has a switching axis that is at a non-parallel and non-perpendicular angle to at least one edge of the mirror.

47. The spatial light modulator of claim 1, wherein each mirror has a switching axis parallel to at least one edge of the active area.

48. The spatial light modulator of claim 5, wherein each mirror has a switching axis at an angle of from 40 to 55 degrees to one or more edges of each nor.

49. The spatial light modulator of claim 1, wherein each mirror has a front edge that is non-perpendicular to any edge of the active area.

50. The spatial light modulator of claim 1, wherein each mirror is a square mirror having four edges defining the square mirror, wherein the four edges of each mirror is neither parallel nor perpendicular to any edges of the active area.

51. The spatial light modulator of claim 1, wherein addressing rows connect to every other mirror.

52. The spatial light modulator of claim 1, wherein addressing columns connect to every other mirror.

53. The spatial light modulator of claim 1, wherein hinges are disposed below each mirror and are held on support posts.

54. The spatial light modulator of claim 5, wherein the mirrors comprise hinges that extend parallel to the leading and trailing edges of the active area.

55. The spatial light modulator of claim 1, wherein the mirrors have jagged edges.