Process for manufacturing high-sensitivity capacitive and resonant integrated sensors, particularly accelerometers and gyroscopes, and sensors made therefrom

• US 6,090,638 A
• Filed: 07/10/1998
• Issued: 07/18/2000
• Est. Priority Date: 07/10/1997
• Status: Expired due to Fees

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Montanini, Pietro, Ferrari, Paolo, Vigna, Benedetto, Ferrera, Marco
• Primary Examiner(s): Monin, Jr., Donald L.
• Assistant Examiner(s): DIETRICH, MICHAEL C
• Application Number:
  US09/113,979
• Time in Patent Office: 739 Days
• Field of Search: 257/420, 257/414, 257/415, 257/417, 438/50, 438/51, 438/52, 438/739
• US Class Current: 438/50
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2203/0136 Comb structures
• CPC Class Codes: B81B 2203/0307 Anchors
• 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 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• CPC Class Codes: B81C 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• 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 sensor having high sensitivity is formed using a suspended structure with a high-density tungsten core. To manufacture it, a sacrificial layer of silicon oxide, a polycrystal silicon layer, a tungsten layer and a silicon carbide layer are deposited in succession over a single crystal silicon body. The suspended structure is defined by selectively removing the silicon carbide, tungsten and polycrystal silicon layers. Then spacers of silicon carbide are formed which cover the uncovered ends of the tungsten layer, and the sacrificial layer is then removed.

Claims

1. An integrated sensor, comprising:

a suspended structure having a tungsten region, and positioned over a semiconductor material body, and connected to said semiconductor material body through anchorage portions; and

a protective structure comprising silicon portions coupled to and surrounding the tungsten region, wherein said protective structure comprises a region of polycrystalline silicon disposed directly underneath said tungsten region and silicon carbide regions positioned over and at sides of said tungsten region.

2. The sensor according to claim 1 wherein said protective structure is resistant to etching sacrificial material.

3. The sensor according to claim 1 wherein said anchorage portions comprise a tungsten core, the sensor further comprising electrical connection regions inside said semiconductor material body, also underneath and electrically connected to said anchorage portions.

4. The sensor according to claim 1 wherein said semiconductor material body is covered by a silicon nitride layer with the exception of said anchorage portions.

5. An integrated sensor, comprising:

a suspended structure having a tungsten region, and positioned over a semiconductor material body, and connected to said semiconductor material body through anchorage portions; and

a protective structure comprising silicon portions coupled to and surrounding the tungsten region, wherein said protective structure comprises a region of polycrystalline silicon disposed underneath said tungsten region and silicon carbide regions positioned over and at sides of said tungsten region wherein a first adhesive layer is present between said tungsten region and said region of polycrystalline silicon and wherein a second adhesive layer is present between said tungsten region and said silicon carbide regions.

6. An integrated sensor, comprising:

a semiconductor substrate;

a suspended structure suspended over the semiconductor substrate to form a gap between the suspended structure and the semiconductor substrate, the suspended structure including a tungsten region and a protective layer having portions of silicon coupled to and surrounding the tungsten region, wherein said protective layer comprises a region of polycrystalline silicon disposed directly underneath said tungsten region and silicon carbide regions positioned over and at sides of said tungsten region; and

anchorage portions laterally coupling the suspended structure to the semiconductor substrate.

7. The sensor of claim 6, further including:

electrical connection regions within the semiconductor substrate, wherein the anchorage portions are electrically connected to the electrical connection regions.

8. The sensor of claim 6 wherein the protective layer is resistive to etching of sacrificial material removed from between the suspended structure and the semiconductor substrate.

9. The sensor of claim 6, further including an adhesive layer between the tungsten region and the protective layer.

10. The sensor of claim 6 wherein portions of the semiconductor substrate are covered with a silicon nitride layer.

11. An integrated sensor, comprising:

a suspended structure having a tungsten region, the tungsten region surrounded by a protective structure resistant to etching sacrificial material, the protective structure comprising portions of silicon or portions of silicon carbide, the protective structure including a region of polycrystal silicon disposed underneath the tungsten region and a silicon carbide region positioned over and at sides of the tungsten region;

a first adhesive layer present between the tungsten region and the region of polycrystal silicon; and

a second adhesive layer present between the tungsten region and the silicon carbide region.

12. An integrated sensor, comprising:

a semiconductor substrate;

a suspended structure positioned over the semiconductor substrate to form a gap between the suspended structure and the semiconductor substrate, the suspended structure including a tungsten region and a protective layer coupled to and surrounding the tungsten region, the protective layer having a lower portion comprising silicon and an upper portion comprising silicon carbide, the lower portion being directly underneath the tungsten region; and

anchorage portions coupling the suspended structure to the semiconductor substrate.

13. The sensor of claim 12, further comprising another layer between the protective layer and the tungsten region.