Integrated released beam sensor for sensing acceleration and associated methods

• US 6,218,209 B1
• Filed: 11/09/1999
• Issued: 04/17/2001
• Est. Priority Date: 10/24/1997
• Status: Expired due to Term

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Chan, Tsiu Chiu, DeSilva, Melvin Joseph
• Primary Examiner(s): Picardat, Kevin M.
• Application Number:
  US09/436,560
• Time in Patent Office: 525 Days
• Field of Search: 438/48, 438/50, 438/51, 438/52, 257/417, 257/418
• US Class Current: 438/52
• CPC Class Codes: B81B 2201/018 Switches not provided for in B81B2201/014 - B81B2201/016
• 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 2203/0735 Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass

Abstract

An integrated circuit and method are provided for sensing activity such as acceleration in a predetermined direction. The integrated released beam sensor preferably includes a switch detecting circuit region and a sensor switching region connected to and positioned adjacent the switch detecting circuit region. The sensor switching region preferably includes a fixed contact layer, remaining portions of a sacrificial layer on the fixed contact layer, and a floating contact on the remaining portions of the sacrificial layer and having only portions thereof directly overlying the fixed contact layer and in spaced relation therefrom in a normally open position and extending lengthwise generally transverse to the predetermined direction so that the floating contact contacts the fixed contact layer responsive to acceleration in the predetermined direction. The floating contact is preferably a released beam which is released by opening a window or removing unwanted portions of the sacrificial layer. The methods of forming an integrated sensor advantageously are preferably compatible with know integrated circuit manufacturing processes, such as for CMOS circuit manufacturing, with only slight variations therefrom.

Claims

1. A method of forming an integrated sensor, the meth comprising the steps of:

forming a CMOS switch detecting circuit region; and

forming a sensor switching region connected to and positioned adjacent the CMOS switch detecting circuit region, the sensor switching region being formed by;

forming a first conducting layer of material on a support so as to define a fixed contact layer,

forming a sacrificial layer on the first conducting layer;

forming a second conducting layer on the sacrificial layer; and

removing unwanted portions of the sacrificial layer to release the second conducting layer so that the second conducting layer then defines a released beam.

2. A method as defined in claim 1, wherein the step of removing unwanted portions of the sacrificial layer comprises isotropically etching the sacrificial layer to thereby release the second conducting layer.

3. A method as defined in claim 1, wherein the step of forming the sensor switching region further comprises forming an insulating layer on the support prior to the step of forming the first conducting layer.

4. A method as defined in claim 1, wherein the fixed contact layer comprises at least one of polysilicon and a metal.

5. A method as defined in claim 2, wherein the released beam comprises at least one of polysilicon and a metal.

6. A method as defined in claim 2, wherein the released beam forms a released cantilever beam.

7. An integrated sensor as defined in claim 2, wherein said released beam forms a released beam overlying the fixed contact layer so as to have a configuration including at least two supports.

8. A method of forming an integrated sensor, the method comprising the steps of:

providing a switch detecting circuit region; and

forming a sensor switching region connected to and positioned adjacent the switch detecting circuit region, the sensor switching region being formed by at least;

forming a first conducting layer of material on a support so as to define a fixed contact layer,

depositing a sacrificial layer on the first conducting layer,

depositing a second conducting layer on the sacrificial layer, and

removing unwanted portions of the sacrificial layer to release the second conducting layer so as to define a released beam overlying the fixed contact layer.

9. A method as defined in claim 8, wherein the released beam forms a released cantilever beam.

10. A method as defined in claim 8, wherein the released beam forms a released beam overlying the fixed contact layer so as to have a configuration including at least two supports.

11. A method as defined in claim 8, wherein the step of forming the sensor switching region further comprises forming an insulating layer on the support prior to the step of forming the first conducting layer.

12. A method as defined in claim 8, wherein the fixed contact layer comprises at least one of polysilicon and a metal and wherein the step of removing unwanted portions includes isotropically etching the sacrificial layer.

13. A method as defined in claim 12, wherein the second conducting layer comprises at least one of polysilicon and a metal.