Thermally decoupled micro-structured reference element for sensors

• US 8,556,504 B2
• Filed: 07/02/2009
• Issued: 10/15/2013
• Est. Priority Date: 09/02/2008
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Herrmann, Ingo, Herrmann, Daniel, Freund, Frank, Feyh, Ando, Eckardt, Martin
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): AHMED, NASIR UDDIN
• Application Number:
  US13/061,670
• Publication Number:
  US 20110211613A1
• Time in Patent Office: 1,566 Days
• Field of Search: 374/178, 374/E07.035, 374/124, 374/129, 428/156, 428/166, 428/172, 257/414
• US Class Current: 374/178
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/0225 Shape of the cavity itself or of elements contained in or suspended over the cavity
• CPC Class Codes: G01J 5/024 Special manufacturing steps or sacrificial layers or layer structures
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 27/14669 Infrared imagers
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence

Abstract

A micro-structured reference element for use in a sensor having a substrate and a dielectric membrane. The reference element has an electrical property which changes its value on the basis of temperature. The reference element is arranged with respect to the substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate. The reference element is arranged on the underside of the dielectric membrane. The reference element and side walls of the substrate define a circumferential cavern therebetween, which is also bounded by the dielectric membrane, arranged between them. The dielectric membrane is connected to the substrate. A surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area. A surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface. An edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane. Sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.

Claims

1. A micro-structured reference element for use in a sensor having a substrate and a dielectric membrane, wherein:

the reference element has an electrical property which changes its value on the basis of temperature,

the reference element is arranged with respect to the substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate,

the reference element is arranged on the underside of the dielectric membrane,

the reference element and side walls of the substrate define a circumferential cavern therebetween, which is also bounded by the dielectric membrane, arranged between them,

the dielectric membrane is connected to the substrate,

a surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area,

a surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface,

an edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane, and

sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.

2. The micro-structured reference element as claimed in claim 1, wherein the dielectric membrane is in the form of a subregion of one or more dielectric layers.

3. The micro-structured reference element as claimed in claim 1, comprising:

a monocrystalline layer which is produced on the underside of the dielectric membrane; and

at least one pn junction between a positively doped region and a negatively doped region.

4. The micro-structured reference element as claimed in claim 3, wherein the monocrystalline layer comprises epitaxially grown n-doped silicon and the pn junction is formed by p⁺-doped and n⁺-doped silicon.

5. The micro-structured reference element as claimed in claim 1, wherein a bottom of the cavern is formed within the substrate.

6. The micro-structured reference element as claimed in claim 1, wherein the cavern is formed through the substrate.

7. The micro-structured reference element as claimed in claim 1, wherein the dielectric membrane has continuous openings to the cavern.

8. The micro-structured reference element as claimed in claim 1, wherein a material of the dielectric membrane is silica.

9. A sensor arrangement, comprising a reference element and also a micro-structured sensor element having an electrical property which changes its value on the basis of temperature,

wherein the reference element has an electrical property which changes its value on the basis of temperature,

wherein the reference element is arranged with respect to a substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate,

wherein the reference element is arranged on the underside of a dielectric membrane,

wherein the reference element and side walls of the substrate define a circumferential cavern therebetween, which is also bounded by the dielectric membrane, arranged between them,

wherein the dielectric membrane is connected to the substrate,

wherein a surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area,

wherein a surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface,

wherein an edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane, and

wherein sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.

10. A method for operating a temperature sensor, wherein a micro-structured sensor element having an electrical property which changes its value on the basis of temperature determines the temperature to be measured and wherein a reference element is used for referencing,

wherein the reference element has an electrical property which changes its value on the basis of temperature,

wherein the reference element is arranged with respect to a substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate,

wherein the reference element is arranged on the underside of a dielectric membrane,

wherein the reference element and side walls of the substrate define a circumferential cavern therebetween, which is also bounded by the dielectric membrane, arranged between them,

wherein the dielectric membrane is connected to the substrate,

wherein a surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area,

wherein a surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface,

wherein an edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane, and

wherein sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.

11. A micro-structured reference element for use in a sensor having a substrate and a dielectric membrane, wherein:

the reference element has an electrical property which changes its value on the basis of temperature,

the reference element is arranged with respect to the substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate,

the reference element is supported on the underside of the dielectric membrane,

the reference element and side walls of the substrate define a circumferential cavern therebetween, the cavern bounded by the dielectric membrane arranged between the reference element and the side walls around the circumference of the cavern,

the dielectric membrane is in contact with the substrate,

a surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area,

a surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface,

an edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane, and

sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.

12. The micro-structured reference element as claimed in claim 11, wherein the dielectric membrane is in the form of a subregion of one or more dielectric layers.

13. The micro-structured reference element as claimed in claim 11, comprising:

a monocrystalline layer which is produced on the underside of the dielectric membrane; and

at least one pn junction between a positively doped region and a negatively doped region.

14. The micro-structured reference element as claimed in claim 13, wherein the monocrystalline layer comprises epitaxially grown n-doped silicon and the pn junction is formed by p⁺-doped and n⁺-doped silicon.

15. The micro-structured reference element as claimed in claim 11, wherein a bottom of the cavern is formed within the substrate.

16. The micro-structured reference element as claimed in claim 11, wherein the cavern is formed through the substrate.

17. The micro-structured reference element as claimed in claim 11, wherein the dielectric membrane has continuous openings to the cavern.

18. The micro-structured reference element as claimed in claim 11, wherein a material of the dielectric membrane is silica.

19. A sensor arrangement, comprising a reference element and also a micro-structured sensor element having an electrical property which changes its value on the basis of temperature,

wherein the reference element has an electrical property which changes its value on the basis of temperature,

wherein the reference element is arranged with respect to a substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate,

the reference element is supported on the underside of the dielectric membrane,

the reference element and side walls of the substrate define a circumferential cavern therebetween, the cavern bounded by the dielectric membrane arranged between the reference element and the side walls around the circumference of the cavern,

the dielectric membrane is in contact with the substrate,

wherein a surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area,

wherein a surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface,

wherein an edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane, and

wherein sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.

20. A method for operating a temperature sensor, wherein a micro-structured sensor element having an electrical property which changes its value on the basis of temperature determines the temperature to be measured and wherein a reference element is used for referencing,

wherein the reference element has an electrical property which changes its value on the basis of temperature,

wherein the reference element is arranged with respect to a substrate so that the reference element is (i) electrically insulated from the substrate, and (ii) thermally coupled to the substrate, the reference element is supported on the underside of the dielectric membrane,

the reference element and side walls of the substrate define a circumferential cavern therebetween, the cavern bounded by the dielectric membrane arranged between the reference element and the side walls around the circumference of the cavern,

the dielectric membrane is in contact with the substrate,

wherein a surface area of the reference element which is covered by the dielectric membrane is greater than or equal to 10% and less than or equal to 100% of the possible coverable surface area,

wherein a surface of the cavern which is covered by the dielectric membrane is greater than or equal to 50% and less than or equal to 100% of the possible coverable surface, wherein an edge of the reference element which faces the dielectric membrane has greater than or equal to 50% and less than or equal to 100% of its extent contacted by the dielectric membrane, and

wherein sections of the side walls of the cavern which face the dielectric membrane have greater than or equal to 50% and less than or equal to 100% of the possible size contacted by the dielectric membrane.