Silicon light trap devices, systems and methods

• US 10,007,056 B2
• Filed: 12/23/2016
• Issued: 06/26/2018
• Est. Priority Date: 10/18/2012
• Status: Active Grant

• Current Assignee: Infineon Technologies Dresden GmbH & Co. KG (Infineon Technologies AG)
• Original Assignee: Infineon Technologies Dresden GmbH (Infineon Technologies AG)
• Inventors: Kautzsch, Thoralf
• Primary Examiner(s): Dickey, Thomas L
• Application Number:
  US15/390,178
• Publication Number:
  US 20170115452A1
• Time in Patent Office: 550 Days
• CPC Class Codes: G02B 2006/12061 Silicon
• CPC Class Codes: G02B 2006/121 Channel; buried or the like
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/1223 high refractive index type, i.e. high-contrast waveguides
• CPC Class Codes: G02B 6/136 by etching
• 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 31/0547 comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
• CPC Class Codes: Y02E 10/52 PV systems with concentrators

Abstract

Embodiments relate to buried structures for silicon devices which can alter light paths and thereby form light traps. Embodiments of the lights traps can couple more light to a photosensitive surface of the device, rather than reflecting the light or absorbing it more deeply within the device, which can increase efficiency, improve device timing and provide other advantages appreciated by those skilled in the art.

Claims

1. A method of forming a silicon-on-nothing structure, comprising:

providing a silicon structure;

etching a plurality of trenches in the silicon structure;

exposing the silicon structure to a hydrogen atmosphere;

performing reflow or epitaxy,

wherein a light trap structure comprised of respective light trap elements is formed from the plurality of trenches; and

forming a roof structure on the light trap structure.

2. The method of claim 1, further comprising:

forming a plurality of light-focusing structures in the roof structure.

3. The method of claim 2, wherein the forming of the plurality of light-focusing structures comprises etching the roof structure.

4. The method of claim 3, wherein the etching the roof structure comprises etching using a masked potassium hydroxide solution.

5. The method of claim 2, wherein the light-focusing structures are shaped as inverted pyramid structures.

6. The method of claim 2, wherein the light-focusing structures are shaped as funnel structures.

7. The method of claim 1, wherein the roof structure is a separate layer.

8. The method of claim 1, wherein the roof structure is formed in a portion of the silicon structure.

9. The method of claim 1, further comprising:

forming a thermal liner oxide layer in the light trap structure.

10. A method of forming a silicon-on-nothing structure, comprising:

providing a silicon structure;

etching a plurality of trenches in the silicon structure;

exposing the silicon structure to a hydrogen atmosphere; and

performing reflow or epitaxy, wherein a light trap structure comprised of respective light trap elements is formed from the plurality of trenches; and

forming a photo-detector between the light trap structure and the surface of the silicon-on-nothing structure.

11. The method of claim 10, wherein the silicon-on-nothing structure is a photo-sensitive structure.

12. The method of claim 11, wherein the photo-sensitive structure is a photodiode.

13. The method of claim 11, wherein the photo-sensitive structure is a solar cell.

14. The method of claim 11, wherein the photo-sensitive structure forms only a portion of the surface of the silicon-on-nothing structure.

15. The method of claim 11, wherein the photo-sensitive structure forms an entire surface of the silicon-on-nothing structure.

16. The method of claim 11, wherein the photo-sensitive structure comprises a plurality of photo-sensitive structures spaced apart from one another.

17. The method of claim 16, wherein all of the plurality of photo-sensitive structures are formed at the surface of the silicon-on-nothing structure.

18. The method of claim 16, wherein only some of the plurality of photo-sensitive structures are formed at the surface of the structure.