System and method for mass-production of high-efficiency photovoltaic structures

• US 9,842,956 B2
• Filed: 12/21/2015
• Issued: 12/12/2017
• Est. Priority Date: 12/21/2015
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Inc.
• Inventors: Xie, Zhigang, Reddy, Anand J., Xiao, Chunguang, Heng, Jiunn Benjamin
• Primary Examiner(s): Everhart, Caridad
• Assistant Examiner(s): SINGAL, ANKUSH K
• Application Number:
  US14/976,900
• Publication Number:
  US 20170179326A1
• Time in Patent Office: 722 Days
• CPC Class Codes: H01L 31/03682 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/03762 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/0725 Multiple junction or tandem solar cells
• CPC Class Codes: H01L 31/0745 comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells
• CPC Class Codes: H01L 31/0747 comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1868 Passivation
• CPC Class Codes: H01L 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/546 Polycrystalline silicon PV cells
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

One embodiment of the invention can provide a system for fabricating a photovoltaic structure. During fabrication, the system can form a sacrificial layer on a first side of a Si substrate; load the Si substrate into a chemical vapor deposition tool, with the sacrificial layer in contact with a wafer carrier; and form a first doped Si layer on a second side of the Si substrate. The system subsequently can remove the sacrificial layer; load the Si substrate into a chemical vapor deposition tool, with the first doped Si layer facing a wafer carrier; and form a second doped Si layer on the first side of the Si substrate.

Claims

1. A method for fabricating a photovoltaic structure, comprising:

forming a sacrificial layer on a first side of a Si substrate;

loading the Si substrate into a chemical vapor deposition tool, with the sacrificial layer in contact with a wafer carrier;

forming a first doped Si layer on a second side of the Si substrate;

subsequent to forming the first doped Si layer, removing the sacrificial layer that has been in contact with the wafer carrier;

loading the Si substrate into the chemical vapor deposition tool; and

forming a second doped Si layer on the first side of the Si substrate.

2. The method of claim 1, wherein forming the sacrificial layer involves one or more operations selected from a group consisting of:

wet oxidation to form an oxide layer;

thermal oxidation to form an oxide layer;

low-pressure radical oxidation to form an oxide layer;

atomic layer deposition to form an oxide layer or a semiconductor layer; and

chemical-vapor deposition to form an oxide layer or a semiconductor layer.

3. The method of claim 1, wherein a thickness of the sacrificial layer is between 1 and 50 angstroms.

4. The method of claim 1, further comprising:

performing a quick dump rinsing operation prior to removing the sacrificial layer.

5. The method of claim 1, wherein the sacrificial layer includes an oxide layer, and wherein removing the sacrificial layer involves performing a diluted hydrofluoric acid dip.

6. The method of claim 5, wherein a concentration of the diluted hydrofluoric acid is between 0.1 and 5%.

7. The method of claim 1, further comprising:

forming a passivation layer positioned between the Si substrate and the first doped Si layer, wherein the passivation layer includes one or more materials selected from a group consisting of;

aluminum oxide;

amorphous Si;

amorphous SiC; and

intrinsic hydrogenated amorphous Si incorporated with oxygen.

8. The method of claim 1, further comprising:

forming a passivation layer positioned between the Si substrate and the second doped Si layer, wherein the passivation layer includes one or more materials selected from a group consisting of;

aluminum oxide;

amorphous Si;

amorphous SiC; and

intrinsic hydrogenated amorphous Si incorporated with oxygen.

9. The method of claim 1, wherein the first doped Si layer has a graded doping profile, and wherein a doping concentration of the first doped Si layer near a surface away from the Si substrate is greater than 3×

10¹⁹/cm³.

10. The method of claim 1, further comprising one or more operations selected from a group consisting of:

forming a transparent conductive oxide layer on the first doped Si layer; and

forming a transparent conductive oxide layer on the second doped Si layer.

11. A fabrication system, comprising:

a first wet station configured to form a sacrificial layer on a first side of a plurality of photovoltaic structures;

a first chemical vapor deposition tool configured to deposit a first doped Si layer on a second side of the photovoltaic structures, wherein a wafer carrier associated with the first vapor deposition tool is in contact with the sacrificial layer;

a second wet station configured to remove the sacrificial layer; and

a second chemical vapor deposition tool configured to deposit a second doped Si layer on the first side of the photovoltaic structures, wherein during deposition, a wafer carrier associated with the second vapor deposition tool is facing the first doped Si layer.

12. The system of claim 11, wherein while forming the sacrificial layer, the first wet station is configured to perform a wet oxidation process to form an oxide layer on the first side of the photovoltaic structures.

13. The system of claim 12, wherein while removing the sacrificial layer, the second wet station is configured to perform a diluted hydrofluoric acid dip.

14. The system of claim 13, wherein a concentration of the diluted hydrofluoric acid is between 0.1 and 5%.

15. The system of claim 11, wherein a thickness of the sacrificial layer is between 1 and 50 angstroms.

16. The system of claim 11, wherein the second wet station is further configured to perform a quick dump rinsing operation prior to removing the sacrificial layer.

17. The system of claim 11, wherein the first chemical vapor deposition tool is further configured to form a passivation layer positioned between the Si substrate and the first doped Si layer, wherein the passivation layer includes one or more materials selected from a group consisting of:

aluminum oxide;

amorphous Si;

amorphous SiC; and

intrinsic hydrogenated amorphous Si incorporated with oxygen.

18. The system of claim 11, wherein the second chemical vapor deposition tool is further configured to form a passivation layer positioned between the Si substrate and the second doped Si layer, wherein the passivation layer includes one or more materials selected from a group consisting of:

aluminum oxide;

amorphous Si;

amorphous SiC; and

intrinsic hydrogenated amorphous Si incorporated with oxygen.

19. The system of claim 11, wherein the first doped Si layer has a graded doping profile, and wherein a doping concentration of the first doped Si layer near a surface away from the Si substrate is greater than 3×

10¹⁹/cm³.

20. The system of claim 11, further comprising a physical vapor deposition tool configured to perform one or more operations selected from a group consisting of:

forming a transparent conductive oxide layer on the first doped Si layer; and

forming a transparent conductive oxide layer on the second doped Si layer.