Methods of forming thermo-mechanical sensor

• US 6,171,879 B1
• Filed: 12/29/1998
• Issued: 01/09/2001
• 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): Niebling, John F.
• Assistant Examiner(s): Simkovic, Viktor
• Application Number:
  US09/222,171
• Time in Patent Office: 742 Days
• Field of Search: 438/48, 438/50, 438/51, 438/52, 438/53, 438/54, 438/55
• US Class Current: 438/52
• CPC Class Codes: G01K 5/486 using microstructures, e.g. made of silicon G01K7/015, G01K7/028, G01K7/226, G01K17/006 take precedence
• CPC Class Codes: H01H 2037/008 Micromechanical switches operated thermally

Abstract

An integrated circuit and method are provided for sensing activity such as temperature variations in a surrounding environment. The integrated released beam sensor preferably includes a switch detecting circuit region and a sensor switching region connected to the switch detecting circuit region. The sensor switching region preferably includes a fixed contact layer, a sacrificial layer on the fixed contact layer, and a floating contact on the sacrificial layer and having portions thereof overlying the fixed contact layer in spaced relation therefrom in an open switch position and extending lengthwise generally transverse to a predetermined direction. The floating contact preferably includes at least two layers of material. Each of the at least two layers have a different thermal expansion coefficient so that the floating contact displaces in the predetermined direction responsive to a predetermined temperature variation so as to contact the fixed contact layer and thereby form a closed switch position. The methods of forming an integrated sensor advantageously are preferably compatible with known integrated circuit manufacturing processes, such as for CMOS circuit manufacturing, with only slight variations therefrom.

Claims

1. A method of forming an integrated sensor for sensing a temperature variation, the method comprising the steps of:

forming 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;

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

forming a third conducting layer on the second conducting layer, the second conducting layer having a different thermal expansion coefficient than the first conducting layer, and wherein the first and second conducting layers define a floating contact.

2. A method as defined in claim 1, wherein the step of forming the sensor switching region further comprises removing at least unwanted portions of the sacrificial layer to release the second conducting layer so as to define a released beam.

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 1, wherein the first and second conducting layers of the floating contact comprise polysilicon and a metal, respectively.

6. A method as defined in claim 1, wherein each of the first and second conducting layers comprises at least one of the following:

polysilicon, silicon, tungsten, tungsten silicide, aluminum, titanium, titanium nitride, tantalum silicide, and tantalum nitride.

7. A method as defined in claim 1, wherein the floating contact forms a released cantilever beam.

8. An integrated sensor as defined in claim 1, wherein said released beam forms a released beam overlying the fixed contact layer so as to have a configuration including at least two supports.

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

forming a switch detecting circuit region on a substrate; and

then forming a sensor switching region connected to the switch detecting circuit region, the sensor switching region being formed by at least the steps of;

providing a support, the support including the substrate and an insulating layer formed on the substrate,

forming a first conducting layer of material on the insulating layer of the support layer 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,

depositing a third conducting layer on the second conducting 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.

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

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

12. A method as defined in claim 9, wherein the step of forming the sensor switching region further comprises providing wanted remaining portions of the sacrificial layer which include an arcuate surface region underlying the second conducting layer.

13. A method as defined in claim 9, wherein the fixed contact layer comprises at least one of polysilicon and a metal.

14. A method as defined in claim 9, wherein the second and third conducting layers comprises at least one of polysilicon and a metal, respectively.

15. A method as defined in claim 9, wherein each of the first and second conducting layers comprises at least one of the following:

polysilicon, silicon, tungsten, tungsten silicide, aluminum, titanium, titanium nitride, tantalum silicide, and tantalum nitride.

16. A method as defined in claim 9, wherein the integrated sensor comprises an integrated sensor for sensing temperature variation, wherein the second conducting layer has a different thermal expansion coefficient than the first conducting layer, and wherein the first and second conducting layers define a floating contact.