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

• US 6,184,052 B1
• Filed: 10/26/1999
• Issued: 02/06/2001
• Est. Priority Date: 07/10/1997
• 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): Bowers, Charles
• Assistant Examiner(s): LEE, HSIEN MING
• Application Number:
  US09/428,863
• Time in Patent Office: 469 Days
• Field of Search: 438/50-53, 438/412, 438/739
• US Class Current: 438/51
• 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. A process for manufacturing integrated sensors, particularly accelerometers and gyroscopes, comprising the steps of forming a temporary support region of sacrificial material over a semiconductor material body and a suspended structure including a tungsten region over said temporary support region and then removing said temporary support region, wherein said step of forming a suspended structure comprises the steps of:

depositing a polycrystalline silicon layer over said temporary support region;

depositing a tungsten layer over said polycrystalline silicon layer;

depositing a first silicon carbide layer over said tungsten layer;

defining said suspended structure by selectively removing said silicon carbide, tungsten and polycrystalline silicon layers; and

forming spacer elements of silicon carbide laterally with respect to uncovered ends of said tungsten layer.

2. The process according to claim 1 wherein said sacrificial material comprises deposited silicon oxide.

3. The process according to claim 1 wherein said step of forming spacer elements comprises the steps of depositing a second silicon carbide layer over and laterally with respect to said suspended structure and etching said second silicon carbide layer anisotropically.

4. The process according to claim 1 wherein a first and, respectively, a second adhesive layer are deposited before depositing the polycrystalline silicon layer and before depositing the first silicon carbide layer.

5. The process according to claim 1 wherein a step of forming electrical connection regions inside said semiconductor material body is carried out before said step of forming a support region;

wherein said step of forming a support region comprises the step of depositing a sacrificial layer and wherein a step of selectively removing portions of said sacrificial layer at said electrical connection regions is carried out before depositing the polycrystalline silicon layer.

6. The process according to claim 5 wherein a step of depositing a silicon nitride layer is carried out before said step of depositing the sacrificial layer;

wherein said sacrificial layer is of silicon oxide, and wherein a step of selectively removing said silicon nitride layer at said electrical connection regions is carried out after said step of selectively removing portions of said sacrificial layer.

7. A method for producing a sensor, comprising:

forming a sacrificial support layer on a semiconductor substrate;

forming a suspended structure on the sacrificial support layer, the suspended structure having a tungsten region and coupled by at least one anchorage region to the semiconductor substrate; and

removing the sacrificial layer, wherein the step of forming a suspended structure layer comprises;

forming a polysilicon layer over the sacrificial support layer;

forming a tungsten layer over the polysilicon layer;

forming a protection layer over the tungsten layer;

selectively removing portions of the protective, tungsten and polysilicon layers to form a desired pattern; and

covering exposed portions of the tungsten layer with spacer elements.

8. The method of claim 7 wherein the step of covering exposed portions of the tungsten layer comprises:

forming a second protective layer over and lateral to the suspended structure; and

anisotropically etching portions of the second protective layer.

9. A method for producing a sensor, comprising:

forming a sacrificial support layer on a semiconductor substrate;

forming a suspended structure on the sacrificial support layer, the suspended structure having a tungsten region and coupled by at least one anchorage region to the semiconductor substrate; and

removing the sacrificial layer,

forming a first adhesive layer on the sacrificial support layer before forming the polysilicon layer; and

forming a second adhesive layer on the tungsten layer before forming the protective layer.