Modules integrating MEMS devices with pre-processed electronic circuitry, and methods for fabricating such modules

• US 20040227201A1
• Filed: 05/13/2003
• Published: 11/18/2004
• Est. Priority Date: 05/13/2003
• Status: Active Grant

• Current Assignee: Teledyne Scientific & Imaging, LLC (Teledyne Technologies Incorporated)
• Original Assignee: Innovative Technology Licensing LLC
• Inventors: DeNatale, Jeffrey F., Anderson, Robert J., Borwick, Robert L. III
• Granted Patent: US 6,979,872 B2
• Time in Patent Office: Days
• US Class Current: 257/414
• CPC Class Codes: B81C 1/00238 Joining a substrate with an electronic processing unit and a substrate with a micromechanical structure
• CPC Class Codes: H01G 5/38 Multiple capacitors, e.g. ganged
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations
• CPC Class Codes: H01L 2224/48091 Arched
• 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

Abstract

A MEMS module is provided comprising at least one MEMS device adhesively bonded to a substrate or wafer, such as a CMOS die, carrying pre-processed electronic circuitry. The at least one MEMS device, which may comprise a sensor or an actuator, may thus be integrated with related control, readout/signal conditioning, and/or signal processing circuitry.

An example of a method pursuant to the invention comprises the adhesive bonding of a pre-processed electronics substrate or wafer to a layered structure preferably in the form of a silicon-on-insulator (SOI) substrate. The SOI is then bulk micromachined to selectively remove portions thereof to define the MEMS device. Prior to release of the MEMS device, the device and the associated electronic circuitry are electrically interconnected, for example, by wire bonds or metallized vias.

Claims

1. A MEMS module comprising:

at least one MEMS device including a movable element;

a substrate having a surface carrying electronic circuitry, the at least one MEMS device overlying at least a portion of the electronic circuitry;

an organic adhesive bond joining the at least one MEMS device and the circuitry-carrying surface of the substrate; and

electrical conductors connecting the at least one MEMS device with the electronic circuitry.

2. The module of claim 1 in which:

the substrate includes an extension carrying electrical contacts connected to the electronic circuitry, the contacts being adapted to connect the module to a higher assembly.

3. The module of claim 1 in which:

the electrical conductors connecting the at least one MEMS device with the electronic circuitry comprises wire bonds.

4. The module of claim 1 in which:

the electrical conductors connecting the at least one MEMS device with the electronic circuitry comprises plated-through vias.

5. The module of claim 1 in which:

the electronic circuitry-carrying substrate comprises a CMOS die.

6. The module of claim 1 in which:

the module comprises a plurality of MEMS devices; and

the electronic circuitry-carrying substrate comprises a CMOS wafer, the electronic circuitry comprising a plurality of electronic circuits.

7. The module of claim 1 in which:

the at least one MEMS device is formed on an SOI substrate.

8. The module of claim 1 in which:

the at least one MEMS device comprises at least one MEMS sensor and/or at least one MEMS actuator.

9. The module of claim 1 in which:

the at least one MEMS device is selected from the group consisting of an electrical switch, an electromechanical motor, an accelerometer, a capacitor, a pressure transducer, an electrical current sensor, a gyro and a magnetic sensor.

10. The module of claim 1 in which:

the organic adhesive bond comprises an epoxy.

11. The module of claim 1 in which:

the organic adhesive bond is selected from the group consisting of epoxy, polyimide, silicone, acrylic, polyurethane, polybenzimidazole, polyquinoraline and benzocyclobutene.

12. The module of claim 1 further comprising:

a cover enclosing the MEMS device.

13. The module of claim 1 in which:

the at least one MEMS device overlies the entire area occupied by the electronic circuitry.

14. A method of fabricating a module integrating at least one MEMS device with electronic circuitry, the method comprising the steps of:

providing a first substrate including a surface having the electronic circuitry formed thereon;

using an adhesive polymer, bonding said surface of the first substrate to a surface of a second substrate, said surface of the second substrate overlying the electronic circuitry;

selectively etching a portion of the second substrate to define the at least one MEMS device;

selectively etching away a portion of the adhesive polymer to release at least one movable element of the at least one MEMS device, the at least one MEMS device being supported and coupled to the first substrate by at least a part of the remaining adhesive polymer; and

electrically interconnecting the at least one MEMS device with the electronic circuitry on the first substrate.

15. The method of claim 14 in which:

the first substrate comprises a CMOS die.

16. The method of claim 14 in which:

the second substrate comprises a silicon-on-insulator substrate.

17. The method of claim 14 in which:

the step of electrically interconnecting the at least one MEMS device with the electronic circuitry on the first substrate is performed by forming electrically conductive vias through the remaining adhesive polymer.

18. The method of claim 14 in which:

the step of electrically interconnecting the at least one MEMS device with the electronic circuitry on the first substrate is performed by wire bonding.

19. The method of claim 14 in which:

the step of selectively etching a portion of the second substrate to define the at least one MEMS device is performed by an anistropic etching process.

20. The method of claim 19 in which:

the etching process comprises deep reactive ion etching.

21. The method of claim 14 in which:

the step of selectively etching away a portion of the adhesive polymer is performed by an isotropic etching process to selectively undercut the at least one MEMS device and to thereby release the at least one movable element thereof.

22. The method of claim 21 in which:

the isotropic etching process comprises oxygen plasma etching.

23. The method of claim 14 in which:

the adhesive polymer comprises a material selected from the group consisting of epoxy, polyimide, silicone, acrylic, polyurethane, polybenzimidazole, polyquinoraline and benezocyclobutene.

24. The method of claim 14 in which:

the module comprises a plurality of MEMS devices;

the first substrate comprises a CMOS wafer; and

the electronic circuitry comprises plurality of electronic circuits.

25. A method of fabricating a module comprising at least one MEMS device and electronic circuitry connected to said MEMS device, the method comprising the steps of:

providing an SOI substrate comprising a silicon handle layer and a silicon device layer sandwiching an insulating layer, the silicon device layer having a surface defining a bottom surface of the SOI substrate;

providing a pre-processed substrate having a surface carrying said electronic circuitry;

adhesively bonding the bottom surface of the SOI substrate to the electronic circuitry-carrying surface of the pre-processed substrate;

removing the SOI handle and insulating layers to expose an upper surface of the device layer;

selectively removing portions of the device layer to define the at least one MEMS device;

selectively removing portions of the adhesive bond to release the at least one MEMS device; and

electrically interconnecting the at least one MEMS device with at least a portion of the electronic circuitry.

26. The method of claim 25 further comprising the step of:

forming an insulating layer on the upper surface of the device layer after removal of the SOI handle and insulating layers and wherein the step of selective removal of the device layer includes the removal of selected portions of the insulating layer.

27. The method of claim 26 in which:

the insulating layer formed on the upper surface of the device layer comprises a material selected from the group consisting of silicon dioxide, silicon nitride, aluminum oxide, silicon oxynitride and silicon carbide.

28. The method of claim 25 further comprising the step of:

forming an electrically conductive layer on the upper surface of the device layer after removal of the SOI handle and insulating layers and wherein the step of selective removal of the device layer includes the removal of selected portions of the electrically conducting layer.

29. The method of claim 25 in which:

the electrical interconnecting step is performed by wire bonding.

30. The method of claim 25 in which:

the electrical interconnecting step is performed by forming electrically conductive vias through the silicon and adhesive layers.

31. The method of claim 25 in which:

the pre-processed substrate comprises a CMOS wafer.

32. The method of claim 25 further comprising the step of:

enclosing the at least one MEMS device with a protective cover.

33. The method of claim 25 in which:

the silicon device layer of the SOI substrate is doped to impart etch stop and/or semiconductor properties.

34. The method of claim 25 further comprising the steps of:

providing an extension on the pre-processed substrate; and

forming on said extension electrical contacts connected to said electronic circuitry, said contacts being adapted to couple said circuitry to a higher assembly.

35. A method for fabricating a MEMS device module

comprising the steps of:

providing a first substrate;

providing a second substrate, said second substrate having a surface carrying electronic circuitry;

bonding said first substrate to the circuitry-carrying surface of said second substrate with an adhesive polymer layer to form a composite structure;

selectively etching a portion of said first substrate to define a MEMS device; and

selectively etching a portion of said adhesive polymer layer to release said MEMS device, said MEMS device being supported by said first substrate, said first substrate, other than said MEM device, remaining coupled to said second substrate by a remaining portion of said adhesive polymer layer.

36. The method of claim 35 further comprising the step of reducing the thickness of said first substrate prior to the first of said etching steps.

37. The method of claim 35 further comprising the step of doping said first substrate to impart etch stop and/or semiconductor properties.

38. The method of claim 35 wherein said etching of said first substrate comprises the step of performing an anisotropic plasma dry etch.

39. The method of claim 35 wherein said etching of said adhesive polymer layer comprises the step of performing an oxygen plasma etch to selectively undercut and to release the MEM device while maintaining said composite structure.

40. The method of claim 35 wherein said adhesive polymer comprises an epoxy.

41. The method of claim 35 wherein said adhesive polymer is a material selected from the group consisting of epoxy, polyimide, silicone, acrylic, polyurethane, polybenzimidazole, polyquinoraline and benzocyclobutene.

42. The method of claim 35 wherein said bonding step further comprises the steps of:

depositing a layer of epoxy on said first substrate;

depositing a layer of epoxy on the circuitry-carrying surface of said second substrate;

positioning said first and second substrates in a vacuum chamber with said adhesive layers in confronting relationship;

evacuating the air in said chamber;

joining together said first and second substrates so as to form a single epoxy layer therebetween; and

curing said epoxy.

43. A method for fabricating a MEMS device module comprising the steps of:

providing a silicon substrate;

depositing a layer of semiconductor material on said silicon substrate;

providing a pre-processed CMOS wafer having electronic circuitry microfabricated on a surface thereof;

bonding said layer of said semiconductor material to said surface of said CMOS wafer with a layer of adhesive polymer to form a composite structure;

etching said silicon substrate to expose said layer of semiconductor material;

etching said layer of semiconductor material to define a MEMS device; and

selectively removing portions of said layer of adhesive polymer using an isotropic etch to selectively undercut said adhesive polymer layer to release at least one suspended element of said MEMS device, said semiconductor material, other than said MEMS device, being coupled to said CMOS wafer by a remaining portion of said adhesive polymer layer.

44. The method of claim 43 wherein said etching of said silicon substrate comprises the step of performing an anisotropic plasma dry etch.

45. The method of claim 43 further comprising the step of depositing a silicon dioxide layer on said semiconductor material.

46. The method of claim 45 further comprising the step of depositing a layer of adhesive polymer on said silicon dioxide layer and said CMOS wafer prior to said bonding step.

47. The method of claim 46 wherein said etching of said adhesive layer comprises the step of performing an isotrophic etch to selectively undercut said adhesive layer to release the MEMS device while maintaining said composite structure.

48. The method of claim 43 wherein said adhesive polymer is a material selected from the group consisting of epoxy, polyimide, silicone, acrylic, polyurethane, polybenzimidazole, polyquinoraline and benzocyclobutene.

49. The method of claim 43 wherein said etch process step to release said MEMS device from said adhesive layer comprises an oxygen plasma etch.

50. The method of claim 43 wherein said bonding step comprises the steps of:

positioning said silicon substrate and said CMOS wafer with at least one adhesive layer therebetween;

evacuating the air between said substrate and said wafer;

placing said substrate and said wafer into physical contact to form a single adhesive layer thereby forming said composite structure; and

curing said adhesive.

51. The method of claim 50 wherein said adhesive is an epoxy.

52. The method of claim 43 wherein said bonding step further comprises the steps of:

depositing a layer of adhesive polymer on one side of said semiconductor material;

depositing a layer of adhesive polymer on the circuitry-carrying surface of said CMOS wafer;

positioning said semiconductor layer and said CMOS wafer in a vacuum chamber with said adhesive layers in confronting relationship;

evacuating the air from said chamber;

placing said semiconductor layer and said wafer into physical contact so as to form a single adhesive layer therebetween; and

curing said adhesive.

53. The method of claim 52 wherein said adhesive comprises an epoxy.

54. A method for fabricating a module comprising a MEMS device and an electronic circuit, the method comprising the steps of:

providing a silicon-on-insulator (SOI) substrate comprising an insulating layer sandwiched between a silicon handle layer and a silicon device layer, the silicon device layer defining a lower surface of the SOI substrate;

providing an electronics wafer;

bonding the lower surface of said Sol substrate to said electronics wafer with a layer of adhesive polymer to form a composite structure;

removing the SOI handle and insulating layers to expose an upper surface of said SOI device layer;

depositing a top layer of insulating or electrically conducting material on the exposed upper surface of said device layer;

selectively removing said top layer and said device layer to define a MEMS device;

selectively removing said adhesive polymer layer under said MEMS device to release said device; and

electrically interconnecting said MEMS device with said electronics wafer.

55. The method of claim 54 in which:

the top layer is formed of an insulating material selected from the group consisting of silicon dioxide, silicon nitride, aluminum oxide, silicon oxynitride and silicon carbide.

56. The method of claim 54 wherein said selective removal of said top layer and said device layer is performed by an anisotropic plasma dry etch.

57. The method of claim 54 wherein said adhesive is a material selected from the group consisting of epoxy, polyimide, silicone, acrylic, polyurethane, polybenzimidazole, polyquinoraline and benzocyclobutene.

58. The method of claim 54 wherein said step of releasing the MEMS device from said adhesive comprises an oxygen plasma etch.

59. The method of claim 54 wherein said bonding step comprises the steps of:

positioning said SOI substrate and said CMOS wafer with at least one adhesive layer therebetween;

evacuating the air from between said substrate and said wafer;

placing said substrate and said wafer into physical contact to form a single adhesive bond thereby forming a composite structure; and

curing said adhesive.

60. The method of claim 54 wherein said electronics wafer comprises a CMOS wafer.