METHOD OF FORMING DEPOSITED FILM AND METHOD OF FORMING PHOTOVOLTAIC ELEMENT

Abstract

Provided is a deposited film containing microcrystalline silicon by plasma CVD, which includes changing at least one of conditions selected from a high frequency power density, a bias voltage with respect to an interelectrode distance, a bias current with respect to an electrode area, a high frequency power with respect to a source gas flow rate, a ratio of a diluting gas flow rate to a source gas flow rate, a substrate temperature, a pressure, and an interelectrode distance, between conditions for forming a deposited film of a microcrystalline region and conditions for forming a deposited film of an amorphous region; and forming a deposited film under conditions within a predetermined range in the vicinity of boundary conditions under which the crystal system of the deposited film substantially changes between a amorphous state and a microcrystalline state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating an exemplary layer structure of a solar cell formed according to the present invention.

FIG. 2 is a cross-sectional view illustrating another exemplary layer structure of a solar cell formed according to the present invention.

FIG. 3 is a cross-sectional view illustrating still another exemplary layer structure of a solar cell formed according to the present invention.

FIG. 4 is a cross-sectional view illustrating yet another exemplary layer structure of a solar cell formed according to the present invention.

FIG. 5 is a schematic view illustrating an embodiment of a manufacturing apparatus used according to the present invention.

FIG. 6 is an enlarged view of an i-type layer forming chamber.

FIG. 7 is a graphical representation illustrating a crystal system of a deposited film when an interelectrode distance and a pressure at a time of forming the deposited film of conditions for forming the deposited film are changed.

Claims

1. A method of forming a deposited film comprising microcrystalline silicon by plasma CVD, the method comprising: changing at least one of conditions selected from a high frequency power density, a bias voltage with respect to an interelectrode distance, a bias current with respect to an electrode area, a high frequency power with respect to a source gas flow rate, a ratio of a diluting gas flow rate to a source gas flow rate, a substrate temperature, a pressure, and an interelectrode distance, between conditions for forming a deposited film of a microcrystalline region and conditions for forming a deposited film of an amorphous region; andforming a deposited film under conditions within a predetermined range in the vicinity of boundary conditions under which the crystal system of the deposited film substantially changes between a amorphous state and a microcrystalline state.

2. The method according to claim 1, wherein the boundary conditions under which the crystal system of the deposited film substantially changes are such that a ratio of a Raman scattering intensity due to a crystalline component of the deposited film to a Raman scattering intensity due to an amorphous component thereof is changed from three or more to less than three.

3. The method according to claim 1, wherein the boundary conditions under which the crystal system of the deposited film substantially changes are such that both an open circuit voltage value and a short circuit current value of a photovoltaic element comprising the deposited film are changed by 5% or more.

4. A method of forming a deposited film comprising microcrystalline silicon by plasma CVD, the method comprising: changing at least one of conditions selected from a high frequency power density, a bias voltage with respect to an interelectrode distance, a bias current with respect to an electrode area, a high frequency power with respect to a source gas flow rate, a ratio of a diluting gas flow rate to a source gas flow rate, a substrate temperature, a pressure, and an interelectrode distance, between conditions for forming a deposited film of a microcrystalline region and conditions for forming a deposited film of a region in which powder comprising silicon atoms is generated; andforming a deposited film under conditions within a predetermined range in the vicinity of boundary conditions under which powder comprising silicon atoms is generated.

5. The method according to claim 1, wherein the conditions within the predetermined range are such that at least one of the conditions selected from (a) a high frequency power density, (b) a bias voltage with respect to an interelectrode distance, (c) a bias current with respect to an electrode area, (d) a high frequency power with respect to a source gas flow rate, (e) a ratio of a diluting gas flow rate to a source gas flow rate, (f) a substrate temperature, (g) a pressure, and (h) an interelectrode distance is changed from the boundary conditions within a range represented by the equations of 0<a≦0.5 W/cm2; 0<b≦150 V/cm; 0<c≦0.3 mA/cm2; 0<d≦3 W/sccm; 0<e≦10; 0<f≦20° C.; 0<g≦200 Pa; and 0<h≦5 mm.

6. A method of forming a photovoltaic element comprising at least one unit element comprising a p-type layer, an i-type layer, and an n-type layer by plasma CVD, wherein the i-type layer is a substantially intrinsic deposited film comprising microcrystalline silicon, and the i-type layer is formed by the method of forming a deposited film set forth in claim 1.