DIODE BOLOMETER AND METHOD FOR PRODUCING A DIODE BOLOMETER

• US 20110140224A1
• Filed: 12/09/2010
• Published: 06/16/2011
• Est. Priority Date: 06/09/2008
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Kropelnicki, Piotr, Russ, Marco, Vogt, Holger
• Granted Patent: US 8,569,857 B2
• Time in Patent Office: Days
• US Class Current: 257/436
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 21/2007 Bonding of semiconductor wafers to insulating substrates or to semiconducting substrates using an intermediate insulating layer H01L21/2011 takes precedence; bonding of semiconductor wafers to semiconductor wafers for junction formation H01L21/187

Abstract

A bolometer has a semiconductor membrane having a single-crystalline portion, and spacers so as to keep the semiconductor membrane at a predetermined distance from an underlying substrate. The complementarily doped regions of the single-crystalline portion form a diode and the predetermined distance corresponds to a fourth of an infrared wavelength.

Claims

1. A bolometer array comprising pixel elements arranged in columns and rows, each one thereof forming a bolometer, comprising:

an underlying substrate;

a semiconductor membrane per pixel element, comprising a single-crystalline portion, wherein complementarily doped regions of the single-crystalline portion form a diode and a p-n junction extends between same along a column direction, pixel elements neighboring in the column direction exhibiting equal doping profiles; and

a first and a second spacer per pixel element so as to keep the semiconductor membrane at a predetermined distance from the underlying substrate,

wherein the predetermined distance corresponds to a fourth of an infrared wavelength,

wherein a first and a second edge region via which the semiconductor membrane contacts the spacers and which comprise lands for thermal insulation of the semiconductor membrane, follow the complementarily doped regions laterally on both sides of the p-n junction in each pixel element, and

wherein the bolometer additionally comprises an evaluating circuit for each pixel element and at least part of the evaluating circuit is arranged in the underlying substrate laterally between the first and second spacers.

2. The bolometer array in accordance with claim 1, wherein additionally an intrinsic region formed laterally along the semiconductor membrane between the complementarily doped regions is provided per pixel element so that the single-crystalline portion forms a PIN diode.

3. The bolometer array in accordance with claim 1, wherein the underlying substrate comprises a reflection layer such that incident infrared radiation is reflectable on the reflection layer in the direction of the semiconductor membrane.

4. The bolometer array in accordance with claim 1, wherein the complementarily doped regions form a sensor area and additionally serve as an absorption medium for the incident infrared radiation.

5. The bolometer array in accordance with claim 1, wherein in each pixel element the semiconductor membrane additionally comprises a first and a second conductive layer which are electrically insulated from each other by a gap,

wherein the first conductive layer contacts the first doped region and the second conductive layer contacts the second doped region, and wherein the gap is formed along the p-n junction between the complementarily doped regions.

6. The bolometer array in accordance with claim 5, wherein the complementarily doped regions are arranged on a side of the conductive layer facing away from the underlying substrate.

7. The bolometer array in accordance with claim 5, wherein the conductive layer is implemented such that the semiconductor membrane comprises a sheet resistance between 200 ohm/square area and 700 ohm/square area.

8. The bolometer array in accordance with claim 1, wherein the first and second edge regions comprise an amorphized doped semiconductor material.

9. The bolometer array in accordance with claim 1, wherein the lands comprise a reduced layer thickness compared to the semiconductor membrane.

10. The bolometer array in accordance with claim 1, wherein gaps are formed between the lands and the doped regions.

11. The bolometer array in accordance with claim 1, additionally comprising an insulation layer, wherein the insulation layer is arranged between the conductive layer and the complementarily doped regions or is formed on the semiconductor membrane.

12. The bolometer array in accordance with claim 1, wherein in each pixel element the lands are parallel to the p-n junction.

13. The bolometer array in accordance with claim 1, wherein the edge regions are arranged to be centered between the p-n junctions of pixel elements neighboring in the row direction.

14. The bolometer array in accordance with claim 1, wherein pixel elements neighboring in the row direction comprise complementary doping profiles.

15. A method for producing a bolometer array comprising pixel elements arranged in columns and rows, each one thereof forming a bolometer, comprising:

forming a semiconductor membrane comprising a single-crystalline portion per pixel element using complementarily doping regions of the single-crystalline portion of each pixel element so that the complementarily doped regions form a diode and a p-n junction extends between same along a column direction, pixel elements neighboring in a column direction exhibiting equal doping profiles;

forming a bond layer on the semiconductor membrane;

providing a circuit substrate which comprises an evaluating circuit for each pixel element;

bonding the semiconductor membrane and the circuit substrate along the bond layer;

forming a first and a second spacer per pixel element to keep, after removing the bond layer, the semiconductor membrane at a predetermined distance from the underlying substrate so that part of the evaluating circuit is arranged in the underlying substrate laterally between the first and second spacers for each pixel element, the predetermined distance corresponding to a fourth of an infrared wavelength,

patterning the semiconductor membrane so that a first and a second edge region via which the semiconductor membrane contacts the spacers and which comprise lands for thermal insulation of the semiconductor membrane, follow laterally to the complementarily doped regions at both sides of the p-n junction in each pixel element; and

removing the bond layer.

16. The method in accordance with claim 15, further comprising forming an intrinsic portion, the intrinsic portion being formed between the complementarily doped regions.

17. The method in accordance with claim 15, wherein forming the semiconductor membrane comprises:

providing a layer stack comprising a single-crystalline semiconductor layer, an oxide layer and a substrate layer;

thinning the single-crystalline semiconductor layer along the first and second edge regions;

doping the single-crystalline semiconductor layer so as to produce the complementarily doped region;

amorphizing the first and second edge regions; and

forming a conductive layer on the first and second edge regions and partly on the complementarily doped regions.

18. The method in accordance with claim 15, wherein forming the semiconductor membrane comprises:

doping the single-crystalline semiconductor layer so as to produce the complementarily doped regions, by doping in n-type and p-type doping areas which each extend from the p-n junction of the pixel elements of one column to the p-n junction of the pixel elements of a neighboring column such that the dopings continue alternatingly in the row direction and remain the same in the vertical direction, the edge regions being arranged to be centered in the doping areas.

19. A bolometer comprising:

an underlying substrate;

a semiconductor membrane comprising a single-crystalline portion; and

a spacer so as to keep the semiconductor membrane at a predetermined distance from the underlying substrate,

wherein complementarily doped regions of the single-crystalline portion form a diode and the predetermined distance corresponds to a fourth of an infrared wavelength,

wherein the semiconductor membrane contacts the spacers via a first and a second edge region which comprise lands for thermal insulation of the semiconductor membrane,

wherein the first and second edge regions comprise an amorphized doped semiconductor material, and

wherein the bolometer additionally comprises an evaluating circuit and at least part of the evaluating circuit is arranged in the underlying substrate laterally between the first and second spacers.

20. A method for producing a bolometer, comprising:

forming a semiconductor membrane comprising a single-crystalline portion using complementarily doping regions of the single-crystalline portion such that the complementarily doped region forms a diode;

forming a bond layer on the semiconductor membrane;

providing a circuit substrate comprising an evaluating circuit;

bonding the semiconductor membrane and the circuit substrate along the bond layer;

forming a first and a second spacer so as to keep, after removing the bond layer, the semiconductor membrane at a predetermined distance from the underlying substrate such that part of the evaluating circuit is arranged in the underlying substrate laterally between the first and second spacers, the predetermined distance corresponding to a fourth of an infrared wavelength,

patterning the semiconductor membrane such that the semiconductor membrane contacts the first and second spacers via a first and a second edge region;

amorphizing the first and second edge regions; and

removing the bond layer.