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

• US 20050191789A1
• 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:
  US11/102,291
• Publication Number:
  US 20050191789A1
• 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 silicon substrate comprising a plurality of circuitry, electrodes and deflectable mirrors disposed within a rectangular active area on the silicon substrate;

a glass substrate bonded in spaced apart relationship to the lower substrate;

an intermediate substrate bonded between the upper and lower substrates and having an open area for defining a cavity between the silicon substrate and the glass substrate, with the mirrors deflectable within the gap;

wherein the mirrors comprise substantially square mirror plates having edges that are neither perpendicular nor parallel to edges of the rectangular active area, and torsion hinges that allow the mirror plates to move relative to the silicon and glass substrates;

a RAM cell at each mirror location; and

wherein an edge of the silicon substrate is bonded offset from an edge of the glass substrate.

2. The spatial light modulator of claim 1, wherein some of the mirror edges of the mirrors are neither parallel nor perpendicular to the edges of the active area, and some edges are parallel to active area edges.

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

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

5. The spatial light modulator of claim 4, 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.

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

7. The spatial light modulator of claim 6, wherein each mirror has a switching axis at an angle of from 40 to 55 degrees to one or more edges of each mirror.

8. 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.

9. 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.

10. The spatial light modulator of claim 9, wherein addressing rows connect to every other mirror.

11. The spatial light modulator of claim 9, wherein addressing columns connect to every other mirror.

12. The spatial light modulator of claim 9, wherein hinges are disposed below each mirror and are held on support posts.

13. The spatial light modulator of claim 1, wherein the mirrors comprise hinges that extend parallel to the leading and trailing edges of the active area.

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

15. The spatial light modulator of claim 1, wherein the RAM cell is an SRAM cell.

17. The spatial light modulator of claim 26, wherein the substrates are bonded together with an epoxy.

18. The spatial light modulator of claim 2, further comprising a lubricant within the gap for decreasing stiction of the mirrors.

19. The spatial light modulator of claim 18, further comprising a getter within the gap.

20. The spatial light modulator of claim 17, wherein the epoxy is a UV cure epoxy.

21. The spatial light modulator of claim 19, wherein the glass substrate is bonded in an offset relation to the silicon substrate.

22. The spatial light modulator of claim 21, wherein bond pads are exposed on the silicon substrate due to the offset bond.

23. The spatial light modulator of claim 22, wherein bond wires are connected to the bond pads on the silicon substrate.

24. The spatial light modulator of claim 1, wherein the RAM cell is a DRAM cell.

25. The spatial light modulator of claim 23, wherein the getter is disposed on the glass substrate.

26. The spatial light modulator of claim 19, wherein the getter is disposed on the silicon substrate.

27. The spatial light modulator of claim 18, wherein the lubricant is an organic lubricant.

28. The spatial light modulator of claim 19, wherein the getter is a moisture getter.

29. The spatial light modulator of claim 19, wherein the getter is a particle getter.

30. The spatial light modulator of claim 26, wherein the getter is a hydrogen getter.

31. The spatial light modulator of claim 25, wherein the getter is a metal oxide getter.

32. The spatial light modulator of claim 19, wherein the getter is a zeolite getter.

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

34. The spatial light modulator of claim 33, wherein the getter is a combination getter.

35. The spatial light modulator of claim 27, wherein the number of mirrors is from 6,000 to about 6 million.

36. The spatial light modulator of claim 1, further comprising a light blocking rectangular mask.

37. The spatial light modulator of claim 36, wherein the light blocking mask is provided on an underside of the glass substrate.

38. The spatial light modulator of claim 1, wherein some of the mirror edges of the mirrors are neither parallel nor perpendicular to the edges of the active area, and some edges are parallel to active area edges.

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

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

41. The spatial light modulator of claim 40, 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.

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

43. The spatial light modulator of claim 42, wherein each mirror has a switching axis at an angle of from 40 to 55 degrees to one or more edges of each mirror.

44. 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.

45. 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.

46. The spatial light modulator of claim 45, wherein addressing rows connect to every other mirror.

47. The spatial light modulator of claim 45, wherein addressing columns connect to every other mirror.

16. The spatial light modulator of claim IS, wherein the torsion hinges having a thickness of 50 Å

to 2100 Å

.