Process for manufacturing high-sensitivity accelerometric and gyroscopic integrated sensors, and sensor thus produced

• US RE41,856 E1
• Filed: 08/26/2002
• Issued: 10/26/2010
• Est. Priority Date: 07/31/1997
• Status: Expired due to Term

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Montanini, Pietro, Ferrari, Paolo, Vigna, Benedetto, Ferrera, Marco
• Primary Examiner(s): Kwok; Helen C.
• Application Number:
  US10/229,396
• Time in Patent Office: 2,983 Days
• Field of Search: 735/143.2, 735/142.9, 735/143.6, 735/143.8, 735/141.7, 735/041.2, 735/041.4, 735/041.8
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81C 1/00246 Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate
• CPC Class Codes: B81C 2201/0109 Sacrificial layers not provided for in B81C2201/0107 - B81C2201/0108
• CPC Class Codes: B81C 2201/0177 Epitaxy, i.e. homo-epitaxy, hetero-epitaxy, GaAs-epitaxy
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: B81C 2203/0778 Topology for facilitating the monolithic integration not provided for in B81C2203/0764 - B81C2203/0771
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: H01L 21/76202 using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO H01L21/76235 takes precedence; together with vertical isolation, e.g. LOCOS in a SOI substrate, H01L21/76264
• CPC Class Codes: H01L 21/764 Air gaps H01L21/76264 takes precedence

Abstract

A movable mass forming a seismic mass is formed starting from an epitaxial layer and is covered by a weighting region of tungsten which has high density. To manufacture the mass, buried conductive regions are formed in the substrate. Then, at the same time, a sacrificial region is formed in the zone where the movable mass is to be formed and oxide insulating regions are formed on the buried conductive regions so as to partially cover them. An epitaxial layer is then grown, using a nucleus region. A tungsten layer is deposited and defined and, using a silicon carbide layer as mask, the suspended structure is defined. Finally, the sacrificial region is removed, forming an air gap.

Claims

1. An integrated sensor, comprising:

a substrate of a first conductivity type and an epitaxial layer of semiconductor material formed on said substrate, said epitaxial layer forming a movable mass which that is surrounded at its sides by a fixed mass;

said movable mass being separated from said substrate by a gap and at the sides from said fixed mass through trenches formed in said epitaxial layer;

said movable mass being supported by said fixed mass through anchorage portions in said epitaxial layer;

and

buried conductive regions of second conductivity type formed in the substrate and providing electrical contact between the movable mass and the fixed mass, the buried conductive regions selectively facing the epitaxial layer; and

a weighting region comprising tungsten at said movable mass.

2. The sensor according to claim 1 wherein said weighting region extends above said movable mass.

3. The sensor according to claim 2 wherein said weighting region is surrounded by a protective layer of silicon carbide.

4. The sensor according to claim 2, further comprising electronic components formed in a single-crystal epitaxial region in said epitaxial layer wherein said electronic components comprise tungsten contact electrodes.

5. The sensor according to claim 4 wherein adhesive titanium nitride regions extend underneath said weighting region and said contact electrodes.

6. The sensor of claim 1 wherein said substrate has a first conductivity type, the sensor , further comprising:

buried conductive regions of a second conductivity type extending in said substrate and selectively facing said epitaxial layer;

electrically insulating material regions extending on said buried conductive regions and delimiting therebetween portions of selective contact between said buried conductive regions and said movable mass and said fixed mass; and

deep contact regions extending from a surface of said epitaxial layer as far as said buried conductive regions to form deep contacts.

7. The sensor of claim 1 wherein said movable mass has movable electrodes facing and interleaved with fixed electrodes extending from said fixed mass to form a sensor of capacitive type, said movable electrodes comprising respective tungsten weighting regions.

8. An integrated sensor comprising:

a semiconductor substrate having an epitaxial layer formed thereon;

a fixed mass formed in the epitaxial layer on the substrate; and

a movable mass formed in the epitaxial layer and suspended over the substrate to form a gap between the movable mass and the semiconductor substrate, the movable mass including a tungsten layer and being supported by the fixed mass through anchorage portions and separated from the fixed mass by trenches;

buried conductive regions of a second conductivity type extending in said substrate and selectively facing said epitaxial layer;

electrically insulating material regions extending on said buried conductive regions and delimiting therebetween portions of selective contact between said buried conductive regions and said movable mass and said fixed mass; and

a weighting region.

9. The sensor of claim 8 wherein the movable mass includes a tungsten layer is surrounded by a protective layer.

10. The sensor of claim 8, further including electronic components formed on the fixed mass.

11. The sensor of claim 8 wherein the movable mass has moveable electrodes interleaved with fixed electrodes that extend from the fixed mass thus forming a capacitive sensor.

12. An integrated sensor, comprising:

a substrate having a first conductivity type and an epitaxial layer of semiconductor material, the epitaxial layer configured to have a movable mass surrounded at its sides by a fixed mass, the movable mass being separated from the substrate by a gap and separated at the sides from the fixed mass through trenches, the movable mass being supported by the fixed mass through anchorage portions in the epitaxial layer;

a weighting region comprising tungsten at the movable mass;

buried conductive regions of a second conductivity type extending in the substrate and selectively facing the epitaxial layer;

electrically insulating material regions extending on the buried conductive regions and delimiting therebetween portions of selective contact between the buried conductive regions and the movable mass and the fixed mass; and

deep contact regions extending from a surface of the epitaxial layer as far as the buried conductive regions to form deep contacts.

13. The sensor of claim 12 wherein the weighting region comprises tungsten that extends above the movable mass.

14. The sensor of claim 13 wherein the weighting region is surrounded by a protective layer of silicon carbide.

15. The sensor of claim 13, further comprising electronic components formed in a single-crystal epitaxial region in the epitaxial layer, and the electronic components comprising tungsten contact electrodes.

16. The sensor of claim 15 wherein adhesive titanium nitride regions extend underneath the weighting region and the contact electrodes.

17. An integrated sensor, comprising:

a substrate of a first conductivity type and an epitaxial layer of semiconductor material formed on said substrate, said epitaxial layer forming a movable mass that is surrounded at its sides by a fixed mass;

said movable mass separated from said substrate by a gap and at the sides from said fixed mass through trenches formed in said epitaxial layer;

said movable mass supported by said fixed mass through anchorage portions in said epitaxial layer;

buried conductive regions of a second conductivity type extending in the substrate and selectively facing the epitaxial layer;

electrically insulating material regions extending on the buried conductive regions and delimiting therebetween portions of selective contact between the buried conductive regions and the movable mass and the fixed mass; and

a weighting region comprising a metal at said movable mass.

18. The integrated sensor of claim 17 wherein said weighting region comprises the metal layer formed on top of the fixed mass.

19. The integrated sensor of claim 17, the sensor further comprising:

deep contact regions extending from a surface of the epitaxial layer as far as the buried conductive regions to form deep contacts.

20. An integrated sensor, comprising:

a substrate having a first conductivity type and an epitaxial layer of semiconductor material formed on said substrate, said epitaxial layer forming a movable mass that is surrounded at its sides by a fixed mass;

said movable mass being separated from said substrate by a gap and at the sides from said fixed mass through trenches formed in said epitaxial layer;

said movable mass being supported by said fixed mass through anchorage portions in said epitaxial layer;

a weighting region at said movable mass;

buried conductive regions of a second conductivity type extending in said substrate and selectively facing said epitaxial layer;

electrically insulating material regions extending on said buried conductive regions and delimiting therebetween portions of selective contact between said buried conductive regions and said movable mass and said fixed mass; and

deep contact regions extending from a surface of said epitaxial layer as far as said buried conductive regions to form deep contacts.

21. The sensor according to claim 20 wherein said weighting region extends above said movable mass.

22. The sensor according to claim 21 wherein said weighting region is surrounded by a protective layer of silicon carbide.

23. The sensor according to claim 21, further comprising electronic components formed in a single-crystal epitaxial region in said epitaxial layer wherein said electronic components comprise tungsten contact electrodes.

24. The sensor according to claim 23 wherein adhesive titanium nitride regions extend underneath said weighting region and said contact electrodes.

25. The sensor of claim 20 wherein said movable mass has movable electrodes facing and interleaved with fixed electrodes extending from said fixed mass to form a sensor of capacitive type, said movable electrodes comprising respective tungsten weighting regions.