# US 2010/0167461 A1 · Dry cleaning of silicon surface for solar cell applications

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- Number: US 2010/0167461 A1
- Document ID: US20100167461A1
- Status: Published application
- Kind: A1
- Application number: 12/403,931
- Filed: 2009-03-13
- Published: 2010-07-01
- Earliest claimed: 2008-12-31
- Assignees: Applied Materials, Inc.
- Inventors: Virendra V.S. Rana; Michael P. Stewart
- Web page: https://patentgrep.com/patent/US20100167461A1

## CPC

- H10F 71/121: {The active layers comprising only Group IV materials}
- H10F 71/103: {including only Group IV materials}
- H10F 71/1218: {in microcrystalline form}
- Y02E 10/547: Monocrystalline silicon PV cells
- Y02E 10/548: Amorphous silicon PV cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A method and apparatus for cleaning layers of solar cell substrates is disclosed. The substrate is exposed to a reactive gas that may comprise neutral radicals comprising nitrogen and fluorine, or that may comprise anhydrous HF and water, alcohol, or a mixture of water and alcohol. The reactive gas may further comprise a carrier gas. The reactive gas etches the solar cell substrate surface, removing oxygen and other impurities. When exposed to the neutral radicals, the substrate grows a thin film containing ammonium hexafluorosilicate, which is subsequently removed by heat treatment.

## Claims

### Claim 1

A method of processing a layer of a solar cell substrate, comprising:
disposing the solar cell substrate on a substrate support in a process chamber having walls;
providing a reactive gas mixture comprising neutral radicals to the process chamber;
directing the reactive gas mixture toward the substrate;
reacting the neutral radicals with oxygen from the substrate to form a thin film on the substrate;
maintaining a temperature of the substrate below a temperature of the chamber walls during formation of the thin film; and
removing the thin film and depositing hydrogen, fluorine, or both on the substrate surface.

### Claim 2 (depends on 1)

The method of claim 1, wherein the reactive gas mixture comprises nitrogen, fluorine, and hydrogen.

### Claim 3 (depends on 1)

The method of claim 1, wherein providing the reactive gas mixture comprises applying dissociative energy to a precursor gas mixture.

### Claim 4 (depends on 1)

The method of claim 1, wherein the reactive gas mixture comprises nitrogen, fluorine, and hydrogen, and is free of electric charges.

### Claim 5 (depends on 1)

The method of claim 1, wherein the solar cell substrate comprises single crystal silicon, multi-crystalline silicon, or polycrystalline silicon.

### Claim 6

(canceled)

### Claim 7 (depends on 4)

The method of claim 4, wherein applying dissociative energy to the precursor gas mixture comprises forming charged and uncharged reactive species and combining the charged reactive species to form uncharged reactive species.

### Claim 8

A method of processing a solar cell substrate, comprising:
disposing the substrate on a substrate support in a process chamber;
providing a precursor gas mixture to an activation chamber;
activating the precursor gas mixture by applying dissociative energy to the precursor gas mixture to form a reactive gas mixture;
flowing the reactive gas mixture to the process chamber over an interval sufficient to neutralize at least 90% of charged active species in the reactive gas;
exposing a heavily-doped p-type layer of the substrate to the reactive gas to release oxygen gas while forming a thin film on the substrate;
cooling the substrate while exposing the substrate to the reactive gas;
removing the thin film to form an exposed substrate surface and depositing fluorine on the exposed substrate surface, wherein both the removing and depositing are performed by heating the thin film; and
depositing a passivating layer over the fluorinated exposed substrate surface.

### Claim 9 (depends on 8)

The method of claim 8, wherein the precursor gas comprises nitrogen, hydrogen, and fluorine.

### Claim 10 (depends on 8)

The method of claim 8, wherein the reactive gas comprises electrically neutral radicals.

### Claim 11 (depends on 8)

The method of claim 8, wherein the surface of the substrate is a layer of a p-i-n junction.

### Claim at position 12

12-20. (canceled)