Systems and methods for forming thermoelectric devices

• US 9,515,246 B2
• Filed: 02/17/2015
• Issued: 12/06/2016
• Est. Priority Date: 08/17/2012
• Status: Active Grant

• Current Assignee: Silicium Energy, Inc.
• Original Assignee: Silicium Energy, Inc.
• Inventors: Boukai, Akram I., Tham, Douglas W., Hopkins, Adam
• Primary Examiner(s): Rodriguez, Armando
• Application Number:
  US14/624,506
• Publication Number:
  US 20150228883A1
• Time in Patent Office: 658 Days
• US Class Current: 1/1
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: H10N 10/01 Manufacture or treatment
• CPC Class Codes: H10N 10/17 characterised by the structure or configuration of the cell or thermocouple forming the device

Abstract

A vapor phase method for forming a thermoelectric element comprises providing a substrate in a reaction space, the substrate including a pattern of a metallic material adjacent to the substrate, which metallic material is configured to catalyze the oxidation of the substrate. The metallic material is then exposed to a gas having an oxidizing agent and a chemical etchant to form holes in or wires from the substrate.

Claims

1. A method for forming a thermoelectric element, comprising:

(a) providing a substrate in a reaction space, wherein said substrate comprises a semiconductor material, wherein said substrate has a pattern of a metallic material adjacent to said substrate, which metallic material is configured to catalyze the oxidation of said substrate;

(b) exposing said metallic material to a vapor phase oxidizing agent and a vapor phase chemical etchant; and

(c) etching said substrate at an etch rate of at least about 0.01 micrometers/second to form holes in or wires from the substrate, thereby forming said thermoelectric element.

2. The method of claim 1, wherein each of said holes or wires has an aspect ratio of at least about 20:

1.

3. The method of claim 1, wherein a ratio of oxidizing agent to chemical etchant in said gas is at least about 2:

1.

4. The method of claim 1, wherein said substrate is heated to a temperature between about −

50°

C. and 200°

C.

5. The method of claim 1, wherein (a) further comprises:

providing a mask adjacent to said substrate;

forming a pattern of holes in said mask, wherein an individual hole exposes an oxide layer adjacent to said substrate;

exposing said oxide layer to a vapor phase etchant to remove said oxide layer;

depositing said metallic material adjacent to said substrate; and

removing said mask.

6. The method of claim 1, further comprising forming a passivation layer on an underside of said substrate prior to etching said substrate.

7. The method of claim 1, further comprising applying an electric field across said substrate while etching said substrate.

8. The method of claim 1, wherein said substrate is exposed to said vapor phase oxidizing agent and said vapor phase chemical etchant simultaneously.

9. The method of claim 1, wherein said vapor phase oxidizing agent and said vapor phase chemical etchant are in the supercritical phase.

10. The method of claim 1, wherein said thermoelectric element has a figure-of-merit of at least about 0.5.

11. A method for forming a thermoelectric element, comprising contacting a metallic material adjacent to a substrate with a vapor phase oxidizing agent and a vapor phase chemical etchant to form holes in or wires from the substrate at an etch rate of at least about 0.1 nanometer/second to form said thermoelectric element, wherein said holes or wires have an aspect ratio of at least about 20:

1, and wherein surfaces of said substrate exposed by said holes or wires have a roughness between about 0.5 nanometers (nm) and 50 nm across said holes or wires as measured by transmission electron microscopy.

12. The method of claim 11, wherein an individual hole or wire has a surface with a metal content of at least about 0.000001% as measured by x-ray photoelectron spectroscopy (XPS).

13. The method of claim 11, wherein said substrate is simultaneously contacted with said vapor phase oxidizing agent and said vapor phase chemical etchant.

14. The method of claim 11, wherein said thermoelectric element has a figure-of-merit of at least about 0.5.

15. A method for forming a thermoelectric device, comprising:

(a) providing particles of a metallic material adjacent to a substrate, wherein said particles of the metallic material each has an Euler Characteristic <

2; and

(b) exposing said particles to an oxidizing agent and a chemical etchant in the gas phase to catalytically etch said substrate at an etch rate of at least about 0.01 micrometers/second to form holes in or wires from the substrate, thereby forming a thermoelectric element of said thermoelectric device.

16. The method of claim 15, wherein (a) further comprises:

providing a mask adjacent to said substrate, the mask having an array of holes;

depositing a layer of said metallic material adjacent to said mask and exposed portions of said substrate; and

removing said mask to provide said particles of said metallic material adjacent to said substrate.

17. The method of claim 16, wherein providing said mask further comprises:

forming said mask adjacent to said substrate, said mask having three-dimensional structures phase-separated in a polymer matrix; and

removing said three-dimensional structures, thereby providing said holes in said polymer matrix, which holes expose portions of said substrate.

18. The method of claim 15, wherein said particles of said metallic material each has an Euler Characteristic equal to zero.

19. The method of claim 15, wherein said thermoelectric element has a figure-of-merit of at least about 0.5.