Zinc oxide film method and structure for cigs cell

• US 8,557,625 B1
• Filed: 02/10/2012
• Issued: 10/15/2013
• Est. Priority Date: 10/17/2008
• Status: Expired due to Fees

• Current Assignee: Stion Corporation
• Original Assignee: Stion Corporation
• Inventors: Wieting, Robert D.
• Primary Examiner(s): Garber, Charles
• Assistant Examiner(s): MUSTAPHA, ABDULFATTAH B
• Application Number:
  US13/371,239
• Time in Patent Office: 613 Days
• Field of Search: 438/48, 438/61, 438/98, 257/751, 257/763, 257/E21.168, 257/E31.007
• US Class Current: 438/61
• CPC Class Codes: C23C 16/407 of zinc, germanium, cadmium, indium, tin, thallium or bismuth
• CPC Class Codes: H01L 21/02422 Non-crystalline insulating materials, e.g. glass, polymers
• CPC Class Codes: H01L 21/02474 Sulfides
• CPC Class Codes: H01L 21/02485 Other chalcogenide semiconducting materials not being oxides, e.g. ternary compounds
• CPC Class Codes: H01L 21/02491 Conductive materials
• CPC Class Codes: H01L 21/02505 consisting of more than two layers
• CPC Class Codes: H01L 21/02554 Oxides
• CPC Class Codes: H01L 21/02576 N-type
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 31/0749 including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
• CPC Class Codes: H01L 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells

Abstract

A method for fabricating a thin film photovoltaic device. The method includes providing a substrate comprising an absorber layer and an overlying window layer. The substrate is loaded into a chamber and subjected to a vacuum environment. The vacuum environment is at a pressure ranging from 0.1 Torr to about 0.02 Torr. In a specific embodiment, a mixture of reactant species derived from diethylzinc species, water species and a carrier gas is introduced into the chamber. The method further introduces a diborane species using a selected flow rate into the mixture of reactant species. A zinc oxide film is formed overlying the window layer to define a transparent conductive oxide using the selected flow rate to provide a resistivity of about 2.5 milliohm-cm and less and an average grain size of about 3000 to 5000 Angstroms.

Claims

1. A method of forming a zinc oxide film for a photovoltaic device, the method comprising:

providing a substrate in a deposition chamber, wherein the substrate comprises an absorber layer and an overlying window layer;

subjecting the deposition chamber to a vacuum pressure ranging from about 0.1 Torr to about 0.02 Torr;

flowing a zinc-containing precursor and an oxygen-containing precursor into the deposition chamber to form a zinc oxide film over the window layer; and

flowing a boron-containing precursor into the deposition chamber during the flowing of the zinc-containing precursor.

2. The method of claim 1, wherein the zinc-containing precursor is diethylzinc vapor.

3. The method of claim 1, wherein the oxygen-containing precursor is water vapor.

4. The method of claim 1, wherein the oxygen-containing precursor to zinc-containing precursor ratio is greater than about 1 to about 4.

5. The method of claim 1, wherein the oxygen-containing precursor to zinc-containing precursor ratio is about 1.

6. The method of claim 1, wherein the boron-containing precursor to zinc-containing precursor ratio ranges from about zero to about five percent.

7. The method of claim 1, wherein the boron-containing precursor to zinc-containing precursor ratio is one percent.

8. The method of claim 1, wherein the substrate is maintained at a temperature of about 130 Degrees Celsius to about 190 Degrees Celsius.

9. The method of claim 1, wherein the substrate is maintained at a temperature greater than about 200 Degrees Celsius.

10. The method of claim 1, wherein the zinc oxide film has a transmission rate of 80 percent and greater for electromagnetic radiation having a wavelength of about 800 nanometers to about 1200 nanometers.

11. The method of claim 1, wherein the flowing the precursors increases a pressure of the deposition chamber to about 0.5 to about 1 Torr.

12. A method for forming a thin film photovoltaic device, the method comprising:

providing a substrate having a first electrode layer, an absorber material overlying the first electrode layer, and a window layer overlying the absorber layer;

subjecting the deposition chamber to a vacuum pressure ranging from about 0.1 Ton to about 0.02 Torr; and

forming a zinc oxide layer characterized by grain size ranging from about 3000 Å

to about 5000 Å

overlying the window layer using one or more precursor gases including a zinc-containing precursor and an oxygen-containing precursor and a carrier gas comprising a nitrogen species.

13. The method of claim 12, wherein the oxygen-containing precursor is derived from water vapor.

14. The method of claim 12, wherein the zinc-containing precursor is derived from diethylzinc.

15. The method of claim 12, wherein the zinc oxide layer is characterized by an optical transmission rate of 99% and greater.

16. The method of claim 12, wherein the substrate is maintained at a temperature of about 130 Degrees Celsius to about 190 Degrees Celsius.

17. The method of claim 12, wherein the substrate is maintained at a temperature greater than about 200 Degrees Celsius.

18. The method of claim 12, further comprising flowing a boron-containing precursor into the deposition chamber during the flowing of the zinc-precursor.

19. The method of claim 18, wherein the boron-containing precursor to zinc-containing precursor ratio ranges from about zero to about five percent.

20. The method of claim 18, wherein the boron-containing precursor comprises diborane.