Integrated sensor having plurality of released beams for sensing acceleration and associated methods

• US 6,235,550 B1
• Filed: 01/05/2000
• Issued: 05/22/2001
• 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): CHAUDHARI, CHANDRA P
• Application Number:
  US09/478,026
• Time in Patent Office: 503 Days
• Field of Search: 438/52, 438/53, 438/200, 438/233
• US Class Current: 438/52
• CPC Class Codes: B81B 2201/014 having a cantilever fixed on one side connected to one or more dimples
• 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 15/0802 Details
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: G01P 15/18 in two or more dimensions

Abstract

An integrated circuit and method are provided for sensing activity such as acceleration in a predetermined direction of movement. 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 plurality of floating contacts positioned adjacent and lengthwise extending outwardly from said switch detecting circuit region for defining a plurality of released beams so that each of said plurality of released beams displaces in a predetermined direction responsive to acceleration. The plurality of released beams preferably includes at least two released beams lengthwise extending outwardly from the switch detecting circuit region to different predetermined lengths and at least two released beams lengthwise extending outwardly from the switch detecting circuit region to substantially the same predetermined lengths. 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 method comprising the steps of:

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

forming a sacrificial layer on each of the plurality of fixed contact layers,

forming a plurality of second conducting layers on the sacrificial layer, and

removing unwanted portions of the sacrificial layer to release the plurality of second conducting layers so that each of the plurality of second conducting layers defines a released beam overlying the at least one fixed contact layer, the released beam comprising an integrally monolithic material having a generally uniform thickness extending substantially the entire length thereof.

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 each of the plurality of second conducting layers.

3. A method as defined in claim 1, wherein the step of forming the sensor switching region further comprises forming at least one insulating layer on the support prior to the step o f forming the plurality of first conducting layers.

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

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

6. A method as defined in claim 5, wherein each of the plurality of released beams forms a released cantilever beam.

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

providing at least one switch detecting circuit region; and

forming a plurality of sensor switching regions connected to and positioned adjacent the switch detecting circuit region, each of the plurality of sensor switching regions 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 at least unwanted portions of the sacrificial layer to release the second conducting layer so as to define a released beam overlying the fixed contact layer, the released beam comprising an integrally monolithic material having a generally uniform thickness extending substantially the entire length thereof.

8. A method as defined in claim 7, wherein the released beam forms a released cantilever beam, and the method further comprises forming an acceleration calibrator associated with the plurality of released cantilever beams for providing a plurality of calibrated accelerations sensed by the integrated sensor, the acceleration calibrator including a different predetermined length of each of said plurality of released beams so as to substantially correspond to a plurality of different preselected calibration threshold regions.

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

10. A method as defined in claim 7, 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.

11. A method as defined in claim 7, wherein the fixed contact layer comprises at least one of polysilicon and a metal.

12. A method as defined in claim 11, wherein the second conducting layer comprises at least one of polysilicon and a metal.