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

• US RE41,889 E1
• Filed: 02/05/2003
• 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, Ferrera, Marco, Vigna, Benedetto
• Primary Examiner(s): HOANG, QUOC DINH
• Application Number:
  US10/360,367
• Time in Patent Office: 2,820 Days
• Field of Search: 438/50, 438/52, 438/53, 438/48, 438/619, 216/21, 216/2, 216/11, 257414-420, 257/E21.613
• US Class Current: 438/48
• 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. A process for manufacturing an accelerometric and gyroscopic integrated sensor, comprising the steps of:

forming a sacrificial region on in a substrate of semiconductor material;

growing an epitaxial layer on said substrate and said sacrificial region;

and

removing selective portions of said epitaxial layer and said sacrificial region to form a movable mass surrounded at the sides and separated from fixed regions by trenches and separated from said substrate by an air gap, the movable mass supported by anchorage zones only at the sides;

and

forming a weighting region of tungsten at said movable mass.

2. The process according to claim 1, wherein said step of forming a weighting region comprises a step of depositing and defining a tungsten layer over said epitaxial layer to have a shape corresponding to a shape of the movable mass.

3. The process according to claim 2 wherein said step of depositing and defining a tungsten layer is carried out before said step of removing selective portions of said epitaxial layer.

4. The process according to claim 2 wherein after said step of depositing and defining said tungsten layer, a step of masking the epitaxial layer and said weighting regions through a protective layer resistant to etching of said sacrificial region is performed.

5. The process according to claim 4 wherein said sacrificial region is a silicon oxide and said protective layer comprises silicon carbide.

6. The process according to claim 2, comprising, before said step of depositing said tungsten layer, the steps of:

forming electronic components in said epitaxial layer;

depositing a dielectric layer over said electronic components; and

forming contact openings in said dielectric layer, and wherein said step of defining said tungsten layer further comprises the step of forming tungsten contact electrodes for said electronic components and for said accelerometric and gyroscopic sensor.

7. The process according to claim 2 wherein before said step of depositing and defining a tungsten layer, a step of depositing an adhesive titanium nitride layer is performed.

8. The process according to claim 1 wherein a step of forming a nucleus region of non-single-crystal semiconductor material on said sacrificial region is earned out before said step of growing an epitaxial layer and wherein said step of growing an epitaxial layer comprises the step of growing a multi-crystal region on said nucleus region and growing a single-crystal region on said substrate, and wherein said suspended mass is formed in said multi-crystal region and wherein the process comprises the step of forming electronic components in said single-crystal region.

9. The process according to claim 8 wherein said substrate has a first conductivity type;

wherein, before said step of forming a sacrificial region, a step of forming buried conductive regions of a second conductivity type in said substrate is carried out, wherein, at the same time as said step of forming a sacrificial layer, electrically insulating material regions are formed, extending on said buried conductive regions and delimiting therebetween portions of selective contact of said buried conductive regions; and

wherein, after said step of growing an epitaxial layer, a step of forming deep contact regions extending from a surface of said epitaxial layer as far as said buried conductive regions to form deep contacts is performed.

10. A method for producing an integrated sensor comprising the steps of:

forming a sacrificial support layer on in a semiconductor substrate;

forming an epitaxial layer on the sacrificial support layer and on the semiconductor substrate;

depositing a tungsten layer weighting region on the epitaxial layer;

removing the sacrificial support layer; and

forming a movable mass from portions of the epitaxial layer and tungsten layers the weighting region by forming trenches to separate the movable mass from fixed regions of the epitaxial layer and tungsten layers weighting region and separated from said substrate by an air gap, the movable mass thereby supported by anchorage zones only at the sides.

11. The method of claim 10 wherein the step of depositing a weighting region comprises depositing a tungsten layer is performed before the step of forming a movable mass to have a shape corresponding to a shape of the movable mass.

12. The method of claim 10 wherein the step of forming a moveable mass comprises:

forming a protective layer on the tungsten layer weighting region;

masking a pattern on the protective layer; and

etching trenches through the protective layer, tungsten, and epitaxial layers layer, and the weighting region.

13. The method of claim 10, further including the steps of:

forming electronic components in the epitaxial layer;

depositing a dielectric layer over the components; and

forming contact openings in the dielectric layer.

14. A process for manufacturing an accelerometric and gyroscopic integrated sensor, comprising the steps of:

forming a sacrificial region in a substrate of semiconductor material;

growing an epitaxial layer on said substrate and said sacrificial region; and

removing selective portions of said epitaxial layer and said sacrificial region to form a movable mass surrounded at the sides and separated from fixed regions by trenches and separated from said substrate by an air gap, the movable mass supported by anchorage zones only at the sides; and

forming a weighting region of a metal at said movable mass.

15. The process according to claim 14 wherein said step of forming a weighting region comprises a step of depositing and defining a tungsten layer over said epitaxial layer to have a shape corresponding to a shape of the movable mass.

16. A method for producing an integrated sensor comprising the steps of:

forming a sacrificial support layer in a semiconductor substrate;

forming an epitaxial layer in the sacrificial support layer and on the semiconductor substrate;

depositing a metal layer on the epitaxial layer;

removing the sacrificial support layer; and

forming a movable mass from portions of the epitaxial layer and the metal layer by forming trenches to separate the movable mass from fixed regions of the epitaxial layer and weighting region and separated from said substrate by an air gap, the movable mass thereby supported by anchorage zones only at the sides.

17. The process according to claim 16 wherein the step of depositing a metal layer comprises depositing a tungsten layer to have a shape corresponding to a shape of the movable mass.

18. A process for manufacturing an accelerometric and gyroscopic integrated sensor, comprising the steps of:

forming a sacrificial region on a substrate of semiconductor material;

growing an epitaxial layer on said substrate and said sacrificial region;

removing selective portions of said epitaxial layer and said sacrificial region to form a movable mass surrounded at the sides and separated from fixed regions by trenches and separated from said substrate by an air gap, the movable mass supported by anchorage zones only at the sides; and

forming a weighting region at said movable mass,

wherein a step of forming a nucleus region of non-single-crystal semiconductor material on said sacrificial region is carried out before said step of growing an epitaxial layer and wherein said step of growing an epitaxial layer comprises the step of growing a multi-crystal region on said nucleus region and growing a single-crystal region on said substrate, and wherein said suspended mass is formed in said multi-crystal region and wherein the process comprises the step of forming electronic components in said single-crystal region.

19. The process according to claim 18 wherein said substrate has a first conductivity type;

wherein, before said step of forming a sacrificial region, a step of forming buried conductive regions of a second conductivity type in said substrate is carried out, wherein, at the same time as said step of forming a sacrificial layer, electrically insulating material regions are formed, extending on said buried conductive regions and delimiting therebetween portions of selective contact of said buried conductive regions; and

wherein, after said step of growing an epitaxial layer, a step of forming deep contact regions extending from a surface of said epitaxial layer as far as said buried conductive regions to form deep contacts is performed.

20. The process of claim 18 wherein forming the weighting region comprises forming the weighting region over the movable mass to have a shape corresponding to a shape of the movable mass.