Micro-electro-mechanical structure having electrically insulated regions and manufacturing process thereof

• US 7,437,933 B2
• Filed: 07/07/2005
• Issued: 10/21/2008
• Est. Priority Date: 07/12/2004
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Durante, Guido Spinola, Sassolini, Simone, Ferrera, Marco, Marchi, Mauro
• Primary Examiner(s): NOLAND, THOMAS
• Application Number:
  US11/177,474
• Publication Number:
  US 20060070441A1
• Time in Patent Office: 1,202 Days
• Field of Search: 735/041.2, 735/041.5, 257/618, 216/13, 438/50
• US Class Current: 73/504.15
• CPC Class Codes: G01C 19/5769 Manufacturing; Mounting; Housings

Abstract

Micro-electro-mechanical structure formed by a substrate of semiconductor material and a suspended mass extending above the substrate and separated therefrom by an air gap. An insulating region of a first electrically insulating material extends through the suspended mass and divides it into at least one first electrically insulated suspended region and one second electrically insulated suspended region. A plug element of a second electrically insulating material different from the first electrically insulating material is formed underneath the insulating region and constitutes a barrier between the insulating region and the air gap for preventing removal of the insulating region during fabrication, when an etching agent is used for removing a sacrificial layer and forming the air gap.

Claims

1. A micro-electro-mechanical structure comprising:

a substrate of semiconductor material;

a suspended mass extending above said substrate, said suspended mass being separated from said substrate by an air gap and being supported by anchoring regions;

at least one insulating region of a first electrically insulating material, extending through said suspended mass and dividing said suspended mass into at least one first electrically insulated suspended region and one second electrically insulated suspended region; and

at least one plug element of a second electrically insulating material different from said first electrically insulating material, said plug element extending underneath said insulating region and forming a barrier between said insulating region and said air gap.

2. The structure according to claim 1 wherein said insulating region has a preset width and layout, and said plug element has said layout and a width greater than said insulating region.

3. The structure according to claim 1 wherein said plug element comprises a bottom protective region and an auxiliary protective region surrounding at least laterally said bottom protective region.

4. The structure according to claim 3 wherein said bottom protective region comprises a polycrystalline silicon portion facing said air gap.

5. The structure according to claim 4 wherein said bottom protective region further comprises a silicon oxide portion overlying said polycrystalline silicon portion.

6. The structure according to claim 3 wherein said auxiliary protective region further extends on top of said bottom protective region and comprises a silicon carbide layer.

7. The structure according to claim 6 wherein said auxiliary protective region further comprises an auxiliary layer overlying said silicon carbide layer, said auxiliary layer being chosen between silicon nitride and silicon carbide.

8. The structure according to claim 6 wherein said auxiliary protective region extends underneath said suspended mass throughout its extension.

9. The structure according to claim 3 wherein said auxiliary protective region comprises silicon nitride spacers.

10. The structure according to claim 1 wherein said plug element comprises a silicon carbide region.

11. The structure according to claim 1 comprising a gyroscope, said suspended mass forming an accelerometer of said gyroscope, including a first part electrically connected to an actuation assembly and a second part electrically connected to sensing electrodes.

12. A micro-electro-mechanical structure, comprising:

a substrate of semiconductor material; and

a first suspended mass movably suspended from the substrate, the first suspended mass including a first insulating region extending through the first suspended mass, separating the first suspended mass into first and second regions electrically isolated from each other.

13. The micro-electro-mechanical device of claim 12 wherein the first insulating region comprises first and second insulating portions, the first insulating portion lying between the second insulating portion and a first surface of the first suspended mass.

14. The micro-electro-mechanical device of claim 13 wherein first insulating portion includes a plurality of insulating layers.

15. The micro-electro-mechanical device of claim 13 wherein the first insulating region comprises a third insulating portion lying between the second insulating portion and a second surface of the first suspended mass.

16. The micro-electro-mechanical device of claim 12 further comprising a second suspended mass movably suspended from the first suspended mass, the second suspended mass including a second insulating region extending through the second suspended mass and separating the second suspended mass into third and fourth regions electrically isolated from each other.

17. The micro-electro-mechanical device of claim 16 wherein the second insulating region comprises first and second insulating portions, the first insulating portion lying between the second insulating portion and a surface of the second suspended mass.

18. The micro-electro-mechanical device of claim 12 wherein:

the substrate of semiconductor material has a first surface defining a first plane;

the first suspended mass includes second and third surfaces defining second and third planes lying substantially parallel to a plane defined by a surface of the substrate of semiconductor material; and

the first insulating region extends along a fourth plane substantially perpendicular to the second and third planes.

19. The micro-electro-mechanical device of claim 12, further comprising:

a first anchoring spring extending from the substrate to the first suspended mass and electrically coupling the first region of the first suspended mass to a first biasing region of the substrate; and

a second anchoring spring extending from the substrate to the first suspended mass and electrically coupling the second region of the first suspended mass to a second biasing region of the substrate.

20. The micro-electro-mechanical device of claim 12, further comprising:

a first and a second plurality of fixed electrodes coupled to the substrate; and

a first plurality of mobile electrodes coupled to the first suspended mass and comb-fingered to the first plurality of fixed electrodes, each of the first plurality of mobile electrodes being electrically coupled to the first region of the first suspended mass and electrically isolated from the second region of the first suspended mass.

21. The micro-electro-mechanical device of claim 20, further comprising:

a second plurality of mobile electrodes supported by the first suspended mass and comb-fingered to the second plurality of fixed electrodes, each of the second plurality of mobile electrodes being electrically coupled to the second region of the first suspended mass and electrically isolated from the first region of the first suspended mass.

22. The micro-electro-mechanical device of claim 21, further comprising:

a second suspended mass supported by the first suspended mass and movable with respect thereto, the second plurality of mobile electrodes being coupled to the second suspended mass and movable therewith, with respect to the first suspended mass.

23. The micro-electro-mechanical device of claim 22, further comprising:

a plurality of coupling springs extending between the first suspended mass and the second suspended mass, the first suspended mass having a C shape, and the second suspended mass being movably supported between arms of the first suspended mass by the plurality of coupling springs, the second plurality of mobile electrodes being electrically coupled to the second region of the first suspended mass by at least one of the plurality of coupling springs.

24. A micro-electro-mechanical device, comprising:

a substrate of semiconductor material having a first surface defining a first plane;

a suspended mass movably suspended from the substrate and having second and third surfaces defining second and third planes substantially parallel to the first plane, the suspended mass including an insulating region extending through the suspended mass along a fourth plane substantially perpendicular to the second and third planes, and separating the suspended mass into first and second regions electrically isolated from each other; and

protecting means for protecting the insulating region from manufacturing processes carried out after formation of the insulating region.

25. A micro-electro-mechanical device of claim 24 wherein the protecting means includes a plug region formed along a length of the insulating region and between the insulating region and the second surface of the suspended mass.

26. The micro-electro-mechanical device of claim 24, further comprising:

a first anchoring spring extending from the substrate to the suspended mass and electrically coupling the first region of the suspended mass to a first biasing region of the substrate; and

a second anchoring spring extending from the substrate to the suspended mass and electrically coupling the second region of the suspended mass to a second biasing region of the substrate.

27. A process for manufacturing a micro-electro-mechanical structure, comprising:

forming a suspended mass extending above a substrate of semiconductor material and separated therefrom by an air gap;

forming anchoring regions supporting said suspended mass;

forming at least one insulating region of a first electrically insulating material, extending through said suspended mass and dividing said suspended mass into at least one first electrically insulated suspended region and one second electrically insulated suspended region; and

forming at least one plug element of a second electrically insulating material different from said first electrically insulating material, extending underneath said insulating region so as to act as a barrier between said insulating region and said air gap.

28. The process of claim 27 wherein:

the step of forming a suspended mass comprises;

forming a sacrificial layer above a substrate,

forming a structural layer above said sacrificial layer,

removing selectively portions of said structural layer according to a predetermined layout, and

partially removing said sacrificial layer using etching agents for forming suspended regions;

the step of forming at least one plug element comprises, prior to forming said structural layer;

forming the at least one plug element of material resistant to said etching agents; and

the step of forming at least one insulating region comprises, prior to partially removing said sacrificial layer;

forming at least one insulating trench in said structural layer, in a position overlying and aligned to said plug element; and

filling said insulating trench with insulating material.

29. The process according to claim 28 wherein said step of forming at least one plug element comprises the steps of:

forming a bottom protective region; and

forming an auxiliary protective region surrounding at least laterally said bottom protective region.

30. The process according to claim 29 wherein said step of forming a bottom protective region comprises depositing a polycrystalline silicon layer, forming an oxide layer overlying said polycrystalline silicon layer, and removing selectively said oxide and polycrystalline silicon layers.

31. The process according to claim 29 wherein said step of forming an auxiliary protective region comprises depositing a silicon carbide layer above said bottom protective region and said sacrificial layer.

32. The process according to claim 31, wherein said step of forming an auxiliary protective region further comprises the step of depositing a silicon nitride layer on top of said silicon carbide layer.

33. The process according to claim 31, further comprising removing in a self-aligned way said silicon nitride and silicon carbide layers except above and alongside said bottom protective region.

34. The process according to claim 29 wherein said step of forming an auxiliary protective region comprises depositing a silicon nitride layer above said bottom protective region and said sacrificial layer, and removing said silicon nitride layer except alongside said bottom protective region for forming spacers.

35. The process according to claim 28 wherein said step of forming at least one plug element comprises the step of forming a silicon-carbide protective region.