JP2010098061A - Sputtering method and method of manufacturing photovoltaic element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sputtering method and the like which can efficiently deposit a sputtering film having a desired composition by the sputtering method using elements in group-IB, group-IIIB, and group-VIB of the periodic table. <P>SOLUTION: In the sputtering method, composite targets 21, 22, and 23 which are respectively placed on target electrodes 21a, 22a, and 23a connected to a high-frequency power source II and comprise a plurality of elements selected from elements in group-IB, group-IIIB, and group-VIB of the periodic table, and a substrate 11 as a film deposition body are disposed in opposition to each other in the atmosphere of inert gas Ar, and a high voltage is applied to target electrodes 21a, 22a, and 23a to sputter surfaces of composite targets 21, 22, and 23, whereby a thin film is deposited on the substrate 11. The substrate 11 is moved in front of the plurality of composite targets 21, 22, and 23 to deposit the laminate of thin films on the substrate 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sputtering method, and more particularly to a sputtering method using a composite target.

In recent years, expectations for solar cells have increased, and in particular, CIS solar cells using chalcopyrite type compound semiconductors centered on CuInSe ₂ are attracting attention because of their high photoelectric conversion efficiency. Among the thin films constituting each layer of the CIS solar cell, a sputtering method is known as one of the methods for forming a semiconductor layer particularly responsible for power generation (see Patent Document 1).

JP 2000-087234 A

By the way, from an industrial viewpoint, development of a process capable of manufacturing a CIS solar cell at a low cost is required. When employing the sputtering method, it is necessary to form a thin film having a composition to be a precursor of the compound semiconductor layer, and then melt and recrystallize the formed thin film.
However, according to the results studied by the present inventors, in a sputtering operation using a CIS-based semiconductor material, a desired composition may not be obtained for selenium (Se) element which is one of the components. Is known. In this case, in order to adjust the composition of the selenium (Se) element, even if a sputtering operation using a selenium (Se) element single target is performed, the selenium (Se) element has a relatively low melting point, so that the efficiency is high. There is a problem that the film is not formed.

An object of the present invention is to provide a sputtering method by which a sputtering film having a desired composition can be efficiently formed by a sputtering method using elements of Group IB, IIIB, and VIB of the periodic table.
Another object of the present invention is to provide a photovoltaic device manufacturing method capable of consistently forming a surface electrode layer from a back electrode layer at a high speed by a sputtering method.

  In the present invention, a composite target composed of a plurality of elements contained in a compound semiconductor material is used to form a plurality of semiconductor precursor layers having different elemental compositions of the compound semiconductor material by sputtering. In addition, in the photovoltaic device manufacturing method, a method of forming a thin film stack in which a plurality of semiconductor precursor layers having different elemental compositions are stacked by sputtering using a composite target and melting and diffusing the thin film stack is adopted. Yes.

Thus, according to the present invention, in an inert gas atmosphere, a composite target composed of a plurality of elements selected from Group IB, Group IIIB, and Group VIB placed on a target electrode connected to a high-frequency power source; There is provided a sputtering method characterized in that a thin film is formed on a substrate by opposingly arranging a substrate as a deposition target, applying a high voltage to a target electrode, and sputtering the surface of the composite target.
Here, in the sputtering method to which the present invention is applied, the composite target is preferably composed of selenium (Se) and a selenium (Se) compound.
Furthermore, the selenium compound is preferably a copper (Cu) -selenium (Se) compound or an indium (In) -selenium (Se) compound.
Furthermore, in the sputtering method to which the present invention is applied, a plurality of composite targets having different composition ratios of a plurality of elements selected from Group IB, IIIB, and VIB of the periodic table are arranged to face the substrate, and a plurality of substrates are arranged. It is preferable to form a thin film stack on the substrate by moving in front of the composite target.

  Next, according to the present invention, there is provided a method for manufacturing a photovoltaic device having a back electrode layer, a compound semiconductor layer, and a surface electrode layer, wherein the back electrode layer is formed on the substrate. A thin film stack forming step of forming a thin film stack in which a plurality of semiconductor precursor layers containing elements constituting the compound semiconductor material are stacked on the formed back electrode layer, and the formed thin film stack A surface electrode layer forming step for forming a surface electrode layer on the body, and a compound semiconductor layer capable of forming a pn junction by melting and diffusing a plurality of semiconductor precursor layers of the thin film stack after forming the surface electrode A plurality of semiconductor precursor layers of the thin film stack are formed by sputtering using a composite target composed of a plurality of elements contained in a compound semiconductor material. Method for manufacturing photovoltaic device It is provided.

Here, in the method for manufacturing a photovoltaic device to which the present invention is applied, it is preferable that the back electrode layer, the thin film laminate, and the front electrode layer are formed in a consistent manner by sputtering.
Further, the compound semiconductor layer is preferably composed of a chalcopyrite compound semiconductor material containing an element of Group IB, IIIB, or VIB of the periodic table.
Furthermore, the compound semiconductor layer is preferably composed of a CIS-based semiconductor material having a chalcopyrite structure containing copper (Cu), indium (In), and selenium (Se).

According to the present invention, by using a composite target including a plurality of elements constituting a compound semiconductor material, a plurality of semiconductor precursor layers having different element compositions can be efficiently formed by sputtering.
In addition, a compound semiconductor layer having good crystallinity and capable of forming a pn junction is formed by continuously forming a back electrode layer, a semiconductor precursor layer, a surface electrode layer, and the like by sputtering, followed by heat treatment. The photovoltaic device can be manufactured by high-speed and consistent operation.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary. Further, the drawings to be used are for explaining the present embodiment and do not represent the actual size.

In the photovoltaic device manufacturing method to which the present embodiment is applied, first, a predetermined sputtering apparatus is used, and a back electrode layer, a thin film laminate of a semiconductor precursor layer, and a surface electrode layer are formed on a substrate by a sputtering method. Film.
The thin film stack of the semiconductor precursor layers is formed by sputtering using a composite target composed of a plurality of elements contained in the compound semiconductor material. At this time, a combination of elements constituting the composite target is appropriately changed, and a plurality of semiconductor precursor layers having different element compositions are formed. The composite target will be described later.
Next, the substrate on which the back electrode layer, the thin film stack of the semiconductor precursor layer, and the surface electrode layer are formed is heated using a predetermined heating device (for example, light irradiation with a halogen lamp or the like). To do. By this heating operation, a plurality of semiconductor precursor layers are melted and diffused to form a compound semiconductor layer made of a compound semiconductor crystal capable of forming a pn junction.

FIG. 1 is a diagram for explaining an example of a photovoltaic element formed by the photovoltaic element manufacturing method to which the present embodiment is applied.
Figure 1 (a) shows a photovoltaic device precursor I ₀ depositing the thin film lamination of the semiconductor precursor layer, FIG. 1 (b) shows a photovoltaic element I to the compound semiconductor layer is formed.
As shown in FIG. 1 (a), the production of photovoltaic devices precursor I _0, first, on the substrate 1, forming the back surface electrode layer 2 made of a metal material (back electrode layer forming step). Next, on the back electrode layer 2, as a plurality of semiconductor precursor layers composed of elements contained in the compound semiconductor material, a p-type semiconductor forming precursor layer 8a, a diffusion control precursor layer 8b, and an n-type semiconductor are formed. The forming precursor layer 8c is formed in order, and the thin film stack 8 of the semiconductor precursor layer is formed (thin film stack forming step). Subsequently, a surface electrode layer 5 made of a transparent electrode material is formed thereon (surface electrode layer forming step). Each layer is formed by sputtering using a predetermined sputtering apparatus.

  In the present embodiment, the thin film stack 8 as a stack of a plurality of semiconductor precursor layers is formed using a composite target composed of a plurality of elements contained in a compound semiconductor material. Here, as the compound semiconductor material, a chalcopyrite type compound semiconductor material containing an element of Group IB, IIIB, or VIB of the periodic table is preferable. In particular, in this embodiment, a Cu—In—Se semiconductor material having a chalcopyrite structure including copper (Cu), indium (In), and selenium (Se) is preferable.

  Therefore, it is preferable that the element of the composite target used when forming the thin film laminate 8 composed of the semiconductor precursor layer is selected from elements of the IB group, IIIB group, and VIB group of the periodic table. Specifically, copper (Cu) is mentioned as an element of Periodic Table Group IB. Examples of Group IIIB elements of the periodic table include indium (In) and gallium (Ga). Examples of elements of the VIB group of the periodic table include selenium (Se) and sulfur (S).

Here, in FIG. 1 (a), a p-type semiconductor forming the precursor layer 8a of the photovoltaic device precursor I ₀ is a thin film having a composition of p-type semiconductor compound capable forming element by heating operations to be described later . In this embodiment, specifically, a Cu—Se compound is used in which the selenium (Se) concentration is in the range of 33.3 at% to 52.5 at%, and the melting point decreases as the selenium (Se) concentration increases. A film is being formed.
The n-type semiconductor forming precursor layer 8c is a thin film having a composition of elements that can form an n-type semiconductor compound by a heating operation described later. Specifically, in this embodiment, the selenium (Se) concentration is in the range of 50 at% to 60 at%, and the film is formed using an In—Se compound in which the melting point increases as the selenium (Se) concentration increases. Yes.
Furthermore, the diffusion control precursor layer 8b is provided to control the diffusion of the p-type semiconductor formation precursor layer 8a and the n-type semiconductor formation precursor layer 8c by melt diffusion.

In this embodiment, by using a composite target as a target of a sputtering apparatus, a plurality of semiconductor precursor layers having different composition ratios of elements contained in a compound semiconductor material can be easily formed.
In particular, in the present embodiment, the composite target is preferably composed of selenium (Se) and a selenium (Se) compound. Here, examples of the selenium (Se) compound include In—Se based compounds such as InSe ₄ and In ₂ Se ₃ ; Cu—Se based compounds, and Cu—Ga based compounds.

That is, as described above, the melting point of the Cu-Se compound or In-Se compound contained in the semiconductor precursor layer can be adjusted by the concentration of selenium (Se) contained in these compounds. Therefore, the composition of Se—In—Cu in the semiconductor precursor layer can be controlled by using a composite target in which selenium (Se) and a selenium (Se) compound are combined at an appropriate composition ratio. Further, by using such a composite target, it is not necessary to use an alloy having a special composition as a target during sputtering.
In particular, since selenium (Se) has a property of having a relatively low melting point compared to other elements, the selenium (Se) element is not efficiently formed even if a target made of selenium (Se) alone is used. The problem can be solved.

Next, as shown in FIG. 1 (a), the surface electrode layer 5 side is irradiated with infrared rays 9 as electromagnetic waves for a certain period of time to form a p-type semiconductor forming precursor layer 8a constituting the thin film laminate 8 described above, diffusion The control precursor layer 8b and the n-type semiconductor formation precursor layer 8c are heated. A halogen lamp is preferable as the light source of the infrared ray 9.
The compounds contained in each of the p-type semiconductor forming precursor layer 8a, the diffusion control precursor layer 8b, and the n-type semiconductor forming precursor layer 8c irradiated with the infrared rays 9 are diffused by melt diffusion. Then, as shown in FIG. 1B, the compound semiconductor layer 3 capable of forming a pn junction composed of the p-type semiconductor layer 3a and the n-type semiconductor layer 3b is formed, and the photovoltaic device I is manufactured.
Here, in the present embodiment, the compound semiconductor layer 3 responsible for power generation of the photovoltaic device I is composed of a chalcopyrite type compound semiconductor material containing elements of the IB group, IIIB group, and VIB group of the periodic table. Specifically, the compound semiconductor layer 3 is made of a CIS-based semiconductor material having a chalcopyrite structure containing copper (Cu), indium (In), and selenium (Se).

In addition, as a material which comprises the board | substrate 1, metal films, such as stainless steel, an organic film, glass etc. are mentioned, for example.
The material constituting the back electrode layer 2 is preferably a metal, and examples thereof include at least one metal selected from Mo, Ti, Cr, Al, Ag, Au, Cu, and Pt, or an alloy thereof.
In the present embodiment, the surface electrode layer 5 is made of a transparent electrode material containing at least one selected from ITO (Indium Tin Oxide), SiO ₂ , and ZnO.

(Sputtering equipment)
FIG. 2 is an example of a sputtering apparatus used in this embodiment.
Sputtering apparatus _X shown in FIG. 2 _0, the inside of a predetermined vacuum chamber 10, a composite target 21, 22, 23 the composition of elements three different included in the compound semiconductor material, a composite target 21, 22, 23 A substrate holder 13 configured to be able to hold a substrate 11 disposed to face the substrate 11 and a film forming tray 12 to which the substrate holder 13 is attached are disposed. Here, the composite targets 21, 22, and 23 are composed of a plurality of elements selected from the IB group, IIIB group, and VIB group of the periodic table. As shown in FIG. 1, the composite targets 21, 22, 23 and the substrate 11 are installed so as to be parallel to each other. The film formation tray 12 to which the substrate holder 13 is attached can be moved in the direction of arrow A by a predetermined moving means 14.

  The composite targets 21, 22, and 23 are integrally joined to target electrodes 21a, 22a, and 23a connected to the high-frequency power source II, respectively. The film forming tray 12 that also serves as an electrode of the substrate 11 is connected to a high frequency power source III. Further, the vacuum chamber 10 is provided with an exhaust port connected to the vacuum pump Va and an inlet for an inert gas Ar (discharge gas) such as argon gas.

In the present embodiment, for example, the composite target 21 is configured by combining a plurality of elements for forming the p-type semiconductor forming precursor layer 8a of the photovoltaic element precursor I ₀ (see FIG. 1). . The composite target 22 is configured by combining a plurality of elements for forming the diffusion control precursor layer 8b. Furthermore, the composite target 23 is configured by combining a plurality of elements for forming the n-type semiconductor forming precursor layer 8c.
As shown in FIG. 2, in the present embodiment, the substrate 11 is moved in the direction of the arrow A, so that the surfaces of the three composite targets 21, 22, and 23 are sputtered on the surface of the substrate 11. The thin films of the two semiconductor precursor layers are continuously stacked, and the thin film stack 8 (see FIG. 1) is formed.

(Composite target)
FIG. 3 is a diagram illustrating an example of a composite target. In FIG. 3A, two Se element plates and one In-Se compound plate each formed in a strip shape are used, and the In-Se compound plate is sandwiched between Se element plates. It is a composite target.
FIG. 3B shows a Se element using three Se element plates and two Cu—Se based compound plates each formed in a strip shape, and sandwiching the Cu—Se based compound plate by the Se element plates. This is a composite target in which plates and Cu—Se based compound plates are alternately arranged.
FIG. 3C shows a case where four Se element plates, two Cu—Se based compound plates, and two In—Se based compound plates each formed in a strip shape are used. This is a composite target in which Se-based compound plates and In—Se-based compound plates are alternately arranged with a predetermined angle.

FIG. 3D shows a case in which four circular plates each having a predetermined diameter are formed so that a Cu—Se-based compound plate formed in a quadrilateral is used as a matrix and Se elements partially exist in the matrix. This is a composite target having a structure in which an Se element plate is arranged.
In FIG. 3 (e), an In—Se-based compound plate formed in a relatively vertically long quadrilateral shape is used as a matrix, and the matrix is formed with a predetermined diameter so that Se elements partially exist in the matrix. This is a composite target having a structure in which three circular Se element plates are arranged.
FIG. 3 (f) shows an In—Se compound plate formed in a quadrilateral as a matrix, and is formed in a strip shape having a predetermined width and length so that Se elements partially exist in the matrix. And a composite target having a structure in which two Se element plates are arranged.

FIG. 3 (g) has a circular shape as a whole, and is divided into eight equal parts by four straight lines passing through the center of the circle, and four Se element plates and four In-Se systems. It is a composite target having a structure in which compound plates are alternately arranged.
FIG. 3 (h) shows a structure in which a Se element plate is arranged in the inner region and a Cu—Se based compound plate is arranged in the center and the outer periphery in a circular shape having regions concentrically divided. Is a composite target.

FIG. 3I shows a cross-sectional structure of the composite target. A composite target arranged using a combination of two Se element plates and one In-Se compound plate on a predetermined plate so that the In-Se compound plate is sandwiched between the two Se element plates. It is.
FIG. 3 (j) shows a composite target having a structure in which one In-Se compound plate is formed on a predetermined plate, and two Se element plates are further arranged on the predetermined plate at a predetermined interval. It is.

  FIG. 3 shows an example of the composite target used in the present embodiment, and the present invention is not limited to these. In the present embodiment, the number of elements constituting the composite target, the number of mixtures and compounds, the shape of the composite target, the thickness, width, length, etc. of each element plate constituting the composite target, each element plate The arrangement and the like can be appropriately selected according to the composition of the compound semiconductor layer to be formed, and are not particularly limited.

  Further, in the embodiment described above, a buffer layer can be provided between the compound semiconductor layer 3 and the surface electrode layer 5 of the photovoltaic device I as necessary. By providing a buffer layer between the compound semiconductor layer 3 and the surface electrode layer 5, defects generated at the interface between the compound semiconductor layer 3 and the surface electrode layer 5 can be suppressed.

In addition, the above description is only an example for demonstrating embodiment of this invention, and this invention is not limited to this embodiment.
The present invention can be applied to a photovoltaic device comprising a semiconductor layer composed of a plurality of elements and two electrode layers sandwiching the semiconductor layer, and a method for producing a photovoltaic device having such a structure. For example, a II-VI group semiconductor typified by Cd-Te series, an I-III-VI group semiconductor typified by Cu-In-Se series, and an I-II typified by Cu-Zn-Sn-S series compounds. The present invention can also be applied to an IV group semiconductor composed of two or more elements such as an -IV-VI group semiconductor, an II-IV-V group semiconductor, and a Si-Ge group.

It is a figure for demonstrating an example of the photovoltaic device formed with the manufacturing method of the photovoltaic device to which this Embodiment is applied. It is an example of the sputtering device used in this Embodiment. It is a figure explaining the example of a compound target.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 ... Board | substrate, 2 ... Back electrode layer, 3 ... Compound semiconductor layer, 3a ... P-type semiconductor layer, 3b ... N-type semiconductor layer, 5 ... Surface electrode layer, 8 ... Thin-film laminated body, 8a ... P-type semiconductor formation Precursor layer, 8b ... diffusion control precursor layer, 8c ... n-type semiconductor forming precursor layer, 9 ... infrared ray, 10 ... vacuum chamber, 12 ... film forming tray, 13 ... substrate holder, 14 ... moving means

Claims (8)

A composite target composed of a plurality of elements selected from Group IB, IIIB, and VIB of the periodic table placed on a target electrode connected to a high-frequency power source in an inert gas atmosphere and a substrate as a film formation target And facing each other,
A sputtering method, comprising: forming a thin film on the substrate by applying a high voltage to the target electrode and sputtering the surface of the composite target.   The sputtering method according to claim 1, wherein the composite target is composed of selenium (Se) and a selenium (Se) compound.   The sputtering method according to claim 2, wherein the selenium (Se) compound is a copper (Cu) -selenium (Se) compound or an indium (In) -selenium (Se) compound.   Arranging a plurality of the composite targets having different composition ratios of a plurality of elements selected from Group IB, IIIB, and VIB of the periodic table to face the substrate, and moving the substrate in front of the plurality of the composite targets 4. The sputtering method according to claim 1, wherein a thin film stack is formed on the substrate. A method for producing a photovoltaic device having a back electrode layer, a compound semiconductor layer, and a surface electrode layer,
A back electrode layer film forming step for forming a back electrode layer on the substrate;
A thin film laminate film forming step of forming a thin film laminate in which a plurality of semiconductor precursor layers containing an element constituting a compound semiconductor material are laminated on the formed back electrode layer; and
A surface electrode layer forming step of forming a surface electrode layer on the thin film laminate formed;
A semiconductor layer forming step of forming a compound semiconductor layer capable of forming a pn junction by melting and diffusing the plurality of semiconductor precursor layers of the thin film stack after forming the surface electrode layer;
The method for manufacturing a photovoltaic device, wherein the plurality of semiconductor precursor layers of the thin film stack are formed by sputtering using a composite target composed of a plurality of elements contained in a compound semiconductor material.   The method for manufacturing a photovoltaic device according to claim 5, wherein the back electrode layer, the thin film laminate, and the front electrode layer are formed by sputtering in a consistent manner.   The method for manufacturing a photovoltaic device according to claim 5 or 6, wherein the compound semiconductor layer is made of a chalcopyrite type compound semiconductor material containing an element of Group IB, IIIB, or VIB of the periodic table.   The said compound semiconductor layer is comprised from the CIS type | system | group semiconductor material which has a chalcopyrite structure containing copper (Cu), indium (In), and selenium (Se). The manufacturing method of the photovoltaic device of description.

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