Sensor with improved thermal stability

• US 8,356,514 B2
• Filed: 01/13/2011
• Issued: 01/22/2013
• Est. Priority Date: 01/13/2011
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Wang, Yong-Fa, Beck, Scott Edward
• Primary Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US13/006,397
• Publication Number:
  US 20120180563A1
• Time in Patent Office: 740 Days
• Field of Search: 73 7324- 7326
• US Class Current: 73/204.26
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/692 Thin-film arrangements

Abstract

Improved sensors are disclosed that include a heater resistor and/or one or more sensor resistors. In some instances, the heater resistor may be configured to have a zero or near-zero temperature coefficient of resistance (TCR), while one or more sensor resistors may be configured to have a non-zero higher TCR. In some instances, the heater resistor may include a polysilicon material that is doped with a first concentration of dopant, and the one or more sensing elements may include a polysilicon material that is doped with a second higher concentration of dopant. In some cases, the first concentration of dopant may be configured to provide a heater resistor that has a zero or near-zero temperature coefficient of resistance (TCR).

Claims

1. A flow sensing die for sensing a flow of fluid along a flow direction, the flow sensing die comprising:

a substrate, the substrate defining a membrane;

a heater resistor supported by the membrane, wherein the heater resistor includes a polysilicon material that is doped with a first concentration of a dopant;

a first sensing resistor supported by the membrane at a position upstream of the heater resistor relative to the flow direction;

a second sensing resistor supported by the membrane at a position downstream of the heater resistor relative to the flow direction; and

wherein the first sensing resistor and the second sensing resistor include a polysilicon material that is doped with a second concentration of a dopant, wherein the second concentration is greater than the first concentration.

2. The flow sensing die of claim 1, wherein the first concentration of dopant is configured to provide the heater resistor with a temperature coefficient of resistance (TCR) in the range of zero plus or minus about 500 ppm/°

C.

3. The flow sensing die of claim 1, wherein the second concentration of dopant is configured to provide a larger temperature coefficient of resistance in the first sensing resistor and the second sensing resistor relative to the heater resistor.

4. The flow sensing die of claim 1, wherein the dopant includes phosphorus, arsenic, boron, antimony, aluminum, or gallium.

5. The flow sensing die of claim 1, wherein, when the heater resistor is activated, the first sensing resistor and the second sensing resistor are configured to sense a temperature differential in the flow of fluid along the flow direction.

6. The flow sensing die of claim 1, wherein the heater resistor, the first sensing resistor, and the second sensing resistor are thin film resistive elements.

7. A sensor comprising:

a substrate;

a heater resistor supported by the substrate, wherein the heater resistor includes a polysilicon material that is doped to provide a zero or near-zero temperature coefficient of resistance (TCR); and

one or more sensing resistors supported by the substrate, wherein the one or more sensor resistors include a material having a larger temperature coefficient of resistance (TCR) compared to the heater resistor.

8. The sensor of claim 7, wherein near-zero is in the range of plus or minus 500 ppm/°

C.

9. The sensor of claim 7, wherein the heater resistor includes a polysilicon material that is doped with a first concentration of a dopant.

10. The sensor of claim 9, wherein the one or more sensing resistors include a polysilicon material that is doped with a second concentration of dopant, wherein the second concentration of dopant is higher than the first concentration of dopant.

11. The sensor of claim 10, wherein the dopant includes phosphorus, arsenic, boron, antimony, aluminum, or gallium.

12. The sensor of claim 7, wherein the one or more sensing resistors includes a non-doped material having the larger TCR.

13. The sensor of claim 12, wherein the non-doped material includes platinum or Permalloy.

14. The sensor of claim 7, wherein the heater resistor and the one or more sensing resistors are thin film resistive elements.