# US 10,319,872 B2 · Cost-efficient high power PECVD deposition for solar cells

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- Number: US 10,319,872 B2
- Document ID: US10319872B2
- Status: Granted
- Kind: B2
- Application number: 13/468,292
- Filed: 2012-05-10
- Published: 2013-11-14
- Granted: 2019-06-11
- Earliest claimed: 2012-05-10
- Assignees: International Business Machines Corporation
- Applicants: Tze-Chiang Chen; Augustin J. Hong; Jeehwan Kim; Devendra K. Sadana
- Inventors: Tze-Chiang Chen; Augustin J. Hong; Jeehwan Kim; Devendra K. Sadana
- Web page: https://patentgrep.com/patent/US10319872B2

## CPC

- H10F 10/174: comprising monocrystalline or polycrystalline materials
- C23C 16/0272: {Deposition of sub-layers, e.g. to promote the adhesion of the main coating}
- C23C 16/45523: {Pulsed gas flow or change of composition over time}
- C23C 16/45557: {Pulsed pressure or control pressure}
- C23C 16/50: using electric discharges {(generation and control of plasma in discharge tubes for surface treatment H01J37/32, H01J37/34)}
- C23C 16/515: using pulsed discharges
- H10F 10/13: Photovoltaic cells having absorbing layers comprising graded bandgaps
- H10F 71/10: the devices comprising amorphous semiconductor material
- H10F 71/103: {including only Group IV materials}
- H10F 71/1218: {in microcrystalline form}
- H10F 77/1642: {including only Group IV materials}
- H10F 77/1648: {including microcrystalline Group IV-IV materials, e.g. microcrystalline SiGe}
- H10F 77/1662: {including only Group IV materials}
- H10F 77/1692: {the films including only Group IV materials}
- H10F 77/244: {made of transparent conductive layers, e.g. transparent conductive oxide [TCO] layers}
- H10F 77/247: {comprising indium tin oxide [ITO]}
- H10F 77/251: {comprising zinc oxide [ZnO]}
- H10F 77/311: {for photovoltaic cells}
- H10F 77/48: Back surface reflectors [BSR]
- H10P 14/24: using chemical vapour deposition [CVD]
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- Y02E 10/52: PV systems with concentrators
- Y02E 10/546: Polycrystalline silicon PV cells
- Y02E 10/547: Monocrystalline silicon PV cells
- Y02E 10/548: Amorphous silicon PV cells
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A method for forming a photovoltaic device includes providing a substrate. A layer is deposited to form one or more layers of a photovoltaic stack on the substrate. The depositing of the amorphous layer includes performing a high power flash deposition for depositing a first portion of the layer. A low power deposition is performed for depositing a second portion of the layer.

## Claims

### Claim 1

A method for forming a photovoltaic device, comprising:
providing a substrate; and
depositing a buffer layer of a photovoltaic stack directly on a transparent electrode and between said transparent electrode of zinc oxide and a p-type layer of hydrogenated silicon carbide having a germanium content less than the buffer layer, wherein the buffer layer being a single material layer of silicon germanium is in direct contact with both the transparent electrode and the p-type layer of the photovoltaic stack, the buffer layer comprises a p-type dopant selected from a group consisting of Ga, In and a combination thereof, wherein the depositing the buffer layer comprises using a chemical vapor deposition (CVD) apparatus that includes a high power generator and a low power generator that are separate power generators and are both in communication to an electrode in a single deposition chamber of the PCVD apparatus, the depositing of the single layer includes the steps of:
performing a high power flash deposition for depositing a first portion of the buffer layer on the substrate within the single deposition chamber, the high power flash deposition employing only the high power generator, wherein the high power flash deposition forms a first portion of the germanium containing material layers having a increasing crystallinity with increasing depth;
performing a low power deposition for depositing a second portion of the buffer layer on the substrate within the single deposition chamber, the lower power deposition employing only the low power generator, wherein the low power deposition forms a second portion of the germanium containing material layers that is amorphous to provide the single layer for the buffer layer and a varying crystal structure having said first portion with said increasing crystallinity with said increasing depth and said second portion being said amorphous, wherein the increasing crystallinity is in a direction towards the p-type layer of hydrogenated silicon to provide for alignment of a conduction band of the buffer layer and the p-type layer of hydrogenated silicon to reduce a Schottky barrier between the buffer layer and the p-type layer of hydrogenated silicon; and
forming a intrinsic layer of amorphous silicon on the p-type layer of hydrogenated silicon carbide and an n-type silicon layer to provide a PIN junction.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein the buffer layer includes germanium deposited on the transparent electrode.

### Claim 3 (depends on 1)

The method as recited in claim 1, wherein performing a high power flash deposition includes depositing a thickness of less than about 5 nm in less than about 5 seconds.

### Claim 4 (depends on 1)

The method as recited in claim 1, wherein performing a high power flash deposition includes providing a plasma enhanced chemical vapor deposition at a power of between about 100 mW/cm2 and about 100 W/cm2, wherein the low power deposition has a power between about 1.0 mW/cm2 to about 100 mW/cm2, wherein the power of the lower power deposition is less than the power of the high power flash deposition.

### Claim 5 (depends on 1)

The method as recited in claim 1, wherein performing a high power flash deposition includes pulsing the high power flash deposition to form multiple thicknesses of high power flash deposited material in a same layer.

### Claim 6 (depends on 1)

The method as recited in claim 1, wherein depositing the one or more layers includes depositing layers with increased crystallinity for a p-type layer and a buffer layer, the buffer layer being formed between a transparent electrode on the substrate and the p-type layer.

### Claim 7 (depends on 1)

The method as recited in claim 1, wherein the high power flash deposition is performed before the low power deposition.

### Claim 8 (depends on 1)

The method as recited in claim 1, wherein the high power flash deposition is performed after the low power deposition.

### Claim 9 (depends on 1)

The method as recited in claim 1, wherein the Schottky barrier is eliminated.

### Claim 10

A method for forming a photovoltaic device, comprising:
providing a substrate including a transparent electrode; and
depositing a buffer layer of a single material layer of silicon germanium directly on the transparent electrode of zinc oxide and between and in direct contact with said transparent electrode and a p-type layer of hydrogenated silicon in a photovoltaic stack using a chemical vapor deposition (CVD) apparatus that includes a high power generator and a low power generator that separate power generators and are both in communication to an electrode in a single deposition chamber of the CVD apparatus, the p-type layer of hydrogenated silicon having a germanium content less than the buffer layer, and the buffer layer comprising a p-type dopant selected from a group consisting of Ga, In and a combination thereof, the depositing of the buffer layer including the steps of:
performing a high power flash deposition for depositing a first portion of the buffer layer to increase crystallinity and conductivity of the buffer layer on the substrate within the single deposition chamber, the high power flash deposition employing only the high power generator, wherein the high power flash deposition forms a first portion of the germanium containing material layers having a increasing crystallinity with increasing depth;
performing a low power deposition for depositing a second portion of the buffer layer and having a more amorphous form on the substrate within the single deposition chamber, the lower power deposition employing only the low power generator, wherein the low power deposition forms a second portion of the germanium containing material layers that is amorphous to provide the single layer for the buffer layer of silicon germanium and having a varying crystal structure having said first portion with said increasing crystallinity with said increasing depth and said second portion being said amorphous, wherein the increasing crystallinity is in a direction towards the p-type layer of hydrogenated silicon to provide for alignment of a conduction band of the buffer layer and the p-type layer of hydrogenated silicon to reduce a Schottky barrier between the buffer layer and the p-type layer of hydrogenated silicon; and
forming an intrinsic layer of amorphous silicon on the p-type layer of hydrogenated silicon carbide and an n-type silicon layer to provide a PIN junction.

### Claim 11 (depends on 10)

The method as recited in claim 10, wherein the buffer layer includes germanium deposited on the transparent electrode.

### Claim 12 (depends on 10)

The method as recited in claim 10, wherein performing a high power flash deposition includes depositing a thickness of less than about 5 nm in less than about 5 seconds.

### Claim 13 (depends on 10)

The method as recited in claim 10, wherein performing a high power flash deposition includes providing a plasma enhanced chemical vapor deposition at a power of between about 100 mW/cm2 and about 100 W/cm2, wherein the low power deposition has a power between about 1.0 mW/cm2 to about 100 mW/cm2, wherein the power of the lower power deposition is less than the power of the high power flash deposition.

### Claim 14 (depends on 10)

The method as recited in claim 10, wherein performing a high power flash deposition includes pulsing the high power flash deposition to form multiple thicknesses of high power flash deposited material in a same layer.

### Claim 15 (depends on 10)

The method as recited in claim 10, further comprising depositing the p-type layer by performing a high power flash deposition for depositing a first portion of the p-type layer and performing a low power deposition for depositing a second portion of the p-type layer.

### Claim 16 (depends on 10)

The method as recited in claim 10, wherein the high power flash deposition is performed after the low power deposition.

### Claim 17 (depends on 10)

The method as recited in claim 10, wherein the Schottky barrier is eliminated.