IMPLEMENTATION OF AN OPTIMIZED AVALANCHE PHOTODIODE (APD)/SINGLE PHOTON AVALANCHE DIODE (SPAD) STRUCTURE

• US 20200135956A1
• Filed: 10/24/2018
• Published: 04/30/2020
• Est. Priority Date: 10/24/2018
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Inventors: Piemonte, Claudio
• Granted Patent: US 10,971,643 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 27/1443 with at least one potential jump or surface barrier
• CPC Class Codes: H01L 27/1446 in a repetitive configuration
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14689 MOS based technologies
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/02327 the optical elements being integrated or being directly associated to the device, e.g. back reflectors optical coatings H01L31/0216
• CPC Class Codes: H01L 31/02363 of the semiconductor body itself, e.g. textured active layers
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table

Abstract

A semiconductor device, sensor, and array of SPAD cubes are described. One example of the disclosed semiconductor device includes an array of single-photon avalanche diodes, each single-photon avalanche diode including an undepleted anode region, an undepleted cathode region, an active depleted region positioned between the anode region and cathode region, and at least one conductive trench extending between the anode region and cathode region. In some examples, the at least one conductive trench surrounds the active depleted region and reflects light back into the active depleted region such that one or more photons can be absorbed within the active depleted region even though an absorption coefficient of the light is greater than a thickness of the active depleted region.

Claims

1. A photodetector, comprising:

a plurality of single-photon avalanche diodes or avalanche photodiodes, at least one of the plurality of single-photon avalanche diodes or avalanche photodiodes comprising an un-depleted anode and cathode region which are separated by one or more conductive trenches that extend completely between the anode region and cathode region, wherein the one or more conductive trenches define an active volume of the at least one single-photon avalanche diode or avalanche photodiode and are configured to reflect light back into the active volume of the at least one single-photon avalanche diode or avalanche photodiode.

2. The photodetector of claim 1, wherein the at least one single-photon avalanche diode or avalanche photodiode comprises a light-receiving surface and an opposing surface that at least partially reflects light received at the light-receiving surface back into the active volume of the at least one single-photon avalanche diode or avalanche photodiode, wherein the one or more conductive trenches contain a conductive material therein that is in direct contact with the active volume of the at least one single-photon avalanche diode or avalanche photodiode.

3. The photodetector of claim 2, wherein the light-receiving surface comprises an anti-reflective material and wherein the opposing surface comprises a reflective material.

4. The photodetector of claim 3, wherein the opposing surface and the one or more conductive trenches completely enclose the active volume of the at least one single-photon avalanche diode on all sides except a side corresponding to the light-receiving surface.

5. The photodetector of claim 3, wherein the reflective material comprises metal.

6. The photodetector of claim 1, wherein a distance between the anode region and the cathode region is less than 20 microns.

7. The photodetector of claim 6, wherein the light comprises near-infrared light and wherein the thickness of the anode region and the cathode region is less than 5 microns.

8. The photodetector of claim 2, further comprising:

a conductive grid positioned in proximity with one of the anode region and cathode region.

9. The photodetector of claim 8, wherein the conductive grid is formed by the one or more conductive trenches.

10. The photodetector of claim 8, wherein the conductive grid is positioned on a light-receiving side of the active volume.

11. The photodetector of claim 8, wherein the conductive grid is positioned opposite a light-receiving side of the active volume.

12. The photodetector of claim 1, further comprising:

a dielectric layer positioned adjacent to at least one of the anode region and cathode region.

13. A semiconductor device, comprising:

an array of single-photon avalanche diodes or avalanche photodiodes, each single-photon avalanche diode or avalanche photodiode comprising;

an undepleted anode region;

an undepleted cathode region;

an active depleted region positioned between the anode region and cathode region; and

at least one conductive trench extending between the anode region and cathode region, wherein the at least one conductive trench surrounds the active depleted region and reflects light back into the active depleted region such that one or more photons can be absorbed within the active depleted region even though an absorption coefficient of the light is greater than a thickness of the active depleted region.

14. The semiconductor device of claim 13, wherein the active depleted region is no more than 20 microns thick and wherein the light comprises near-infrared light.

15. The semiconductor device of claim 13, wherein the at least one conductive trench comprises at least four conductive trenches.

16. The semiconductor device of claim 13, wherein the at least one conductive trench comprises a via filled with a metal and wherein the at least one conductive trench is further filled with a polysilicon layer.

17. A sensor, comprising:

a plurality of single-photon avalanche diodes or avalanche photodiodes, each of the plurality of single-photon avalanche diodes or avalanche photodiodes comprising;

an anode region;

a cathode region;

an active depleted region positioned between the anode region and cathode region; and

a conductive trench extending between the anode region and cathode region, wherein the conductive trench encloses the active depleted region and reflects light back into the active depleted region such that one or more photons can be absorbed within the active depleted region even though an absorption coefficient of the light is greater than a thickness of the active depleted region.

18. The sensor of claim 17, wherein the conductive trench is part of a metal grid.

19. The sensor of claim 18, wherein the metal grid is positioned on a light-receiving surface of the plurality of single-photon avalanche diodes.

20. The sensor of claim 18, wherein the metal grid is positioned on a surface that opposes a light-receiving surface of the plurality of single-photon avalanche diodes.