Temperature sensor

• US 5,446,437 A
• Filed: 12/30/1992
• Issued: 08/29/1995
• Est. Priority Date: 01/31/1992
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Bantien, Frank, Reihlen, Eckart
• Primary Examiner(s): Lateef, Marvin M.
• Application Number:
  US07/998,516
• Time in Patent Office: 972 Days
• Field of Search: 338/25, 338/307, 338/308, 437/225, 437/60, 437/918, 73/204.16, 73/204.25, 73/204.26, 73/708, 73/721, 374/178, 204/192.21, 357/26
• US Class Current: 338/25
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/6888 Thermoelectric elements, e.g. thermocouples, thermopiles
• CPC Class Codes: G01K 7/02 using thermoelectric elements, e.g. thermocouples
• CPC Class Codes: G01K 7/22 the element being a non-linear resistance, e.g. thermistor G01K7/26 takes precedence
• CPC Class Codes: Y10S 438/977 Thinning or removal of substrate

Abstract

An improved temperature sensor is designed for the sensitive detection of temperature changes. The temperature sensor includes a frame 9 of monocrystalline silicon and a dielectric diaphragm 13 stretched on it. A monocrystalline silicon structure 35 is disposed on or under the dielectric diaphragm which is used for measuring the temperature. In the course of this, the Seebeck effect, as well as the temperature dependence of the electrical resistance, can be used for detection of any temperature changes.

Claims

1. A temperature sensor having

a frame (9) of monocrystalline silicon;

a dielectric diaphragm (13) supported by the frame (9);

a monocrystalline silicon structure (2, 11,

     35) formed on the dielectric diaphragm (13);

electrical terminal connections (4,

     14) connected to the monocrystalline silicon structure (2, 11,

     35) to obtain electrical measuring outputs representative of the temperature of the dielectric diaphragm (13); and

wherein the monocrystalline structure comprises a temperature-dependent resistor wherein the monocrystalline structure (2, 11,

     35) is doped with a deep doping material.

2. The sensor of claim 1, wherein the deep doping material comprises a material having an energy level which is at least approximately at the center of the energy gap of silicon.

3. The sensor of claim 1, wherein the deep doping material comprises gold, tin, cobalt or vanadium.

4. The sensor of claim 1, wherein the monocrystalline silicon structure (11) is applied to the underside of the dielectric diaphragm (13).

5. The sensor of claim 1, wherein the dielectric diaphragm (13) is formed with connection terminal openings (6), and said electrical terminal connections (4, 14) are connected to the monocrystalline silicon structure (2, 11, 35) through said openings.

6. The sensor of claim 1, wherein the monocrystalline structure (2, 11, 35) is solely supported by the diaphragm (13) and is devoid of overlap with the frame (9).

7. A temperature sensor having

a frame (9) of monocrystalline silicon;

a dielectric diaphragm (13) supported by the frame (9);

a monocrystalline silicon structure (2, 12,

     35) formed on the dielectric diaphragm (13);

electrical terminal connections (4,

     14) connected to the monocrystalline silicon structure (2, 12,

     35) to obtain electrical measuring outputs representative of the temperature of the dielectric diaphragm (13); and

wherein the monocrystalline structure comprises a Seebeck effect semiconductor wherein the monocrystalline structure (12) is partially located in the area of, and overlaps, the frame (9),

the electrical terminal connections are not made of silicon; and

one of two connecting points of the terminal connections (4,

     14), with the silicon structure (2,

     12), is located in the area of the frame (9) and the other is located in the area of the diaphragm (13).

8. The sensor of claim 7, wherein said monocrystalline silicon structure (2, 12, 35) is doped with a doping material comprising at least one of:

phosphorus, boron, or arsenic, and wherein, optionally, said doping materials are present at an elevated concentration.

9. The sensor of claim 7, wherein the monocrystalline silicon structure (12) is applied to the underside of the dielectric diaphragm (13).

10. The sensor of claim 7, wherein the dielectric diaphragm (13) is formed with connection terminal openings (6), and said electrical terminal connections (4, 14) are connected to the monocrystalline silicon structure (2, 12, 35) through said openings.

12. A temperature sensor for use in an air mass flow rate sensor,

comprising the sensor of claim 7,

and further including a heater (16) located adjacent the diaphragm (13) in the vicinity of the monocrystalline silicon structure (12, 35) to maintain the dielectric diaphragm at a higher temperature than the frame (9);

and

wherein the electrical terminal connections (14) are connectable to an electronic evaluation device (40) to evaluate the heat loss of a medium flowing across the surface of the diaphragm, said sensor measuring the temperature of the dielectric diaphragm (13).

13. A method to make a temperature sensor having

a frame (9) of monocrystalline silicon;

a dielectric diaphragm (13) supported by the frame (9);

a monocrystalline silicon structure (2, 11,

     12) formed on the dielectric diaphragm (13);

electrical terminal connections (4,

     14) connected to the monocrystalline silicon structure (2, 11,

     12) to obtain electrical measuring outputs representative of the temperature of the dielectric diaphragm (13);

comprising the steps of

providing a monocrystalline silicon wafer (31);

inserting oxygen ions in the wafer (31) to form a buried silicon oxide layer (32) therein, to form a monocrystalline portion (31) of the wafer, and leave a monocrystalline layer (33) above the silicon oxide layer (32);

shaping or structuring the monocrystalline layer (33) to form a monocrystalline structure (35) above the silicon oxide layer (32);

doping said monocrystalline structure (35);

providing the monocrystalline structure (35) with terminals (34); and

etching a cut-out (37) of the silicon wafer (31) up to the silicon oxide layer (32) while leaving a frame (9) of crystalline wafer material (31), whereby the silicon oxide layer (33) will form the diaphragm (13).

11. A temperature sensor for use in an air mass flow rate sensor,

comprising the sensor of claim 21,

and further including a heater (16) located adjacent the diaphragm (13) in the vicinity of the monocrystalline silicon structure (11, 35) to maintain the dielectric diaphragm at a higher temperature than the frame (9);

and

wherein the electrical terminal connections (14) are connectable to an electronic evaluation device (40) to evaluate the heat loss of a medium flowing across the surface of the diaphragm, said sensor measuring the temperature of the dielectric diaphragm (13).

14. The method of claim 13, wherein the etching step comprises applying an etching solution;

and

further including the step of protecting the silicon structure (2,

     35) from the effect of the etching solution by applying a voltage or by a high concentration of doping materials.

15. The method of claim 13, wherein the step of forming the dielectric layer comprises forming a chemical reaction of the wafer surface with a gas.

16. The method of claim 13, wherein the dielectric layer is created by deposition from a gaseous phase.

17. The method of claim 13, wherein the step of forming the dielectric layer comprises sputtering.

18. The method of claim 13, wherein said doping step comprises deep-doping said monocrystalline structure (2, 35) with a doping material having an energy level which is at least approximately at the center of the energy gap of silicon.

19. The method of claim 13, wherein the step of inserting oxygen ions comprises

implanting oxygen ions in the wafer (31) by ion implantation.

20. The method of claim 13, wherein the etching step comprises etching the cut-out (37) from the back of the silicon wafer (31) up to the silicon layer (32) while leaving the frame (9).

21. The method of claim 19, wherein the etching step comprises etching the cut-out (37) from the back of the silicon wafer (31) up to the silicon layer (32) while leaving the frame (9).