JP3831592B2 - Method for producing compound semiconductor thin film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for producing a compound semiconductor thin film and a compound semiconductor thin film obtained therefrom. More specifically, the present invention relates to a method and apparatus for producing a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element used in the field of thin film solar cells, and a compound semiconductor thin film obtained therefrom.
[0002]
[Prior art]
In recent years, a compound semiconductor thin film having a chalcopyrite structure composed of a group IB element, a group IIIB element and a group VIB element has been used as a light absorption layer constituting a thin film solar cell. As such a compound semiconductor thin film, for example, CuInSe₂Film (so-called “CIS” film), CuInGaSe₂Film (specifically Cu (In, Ga) Se₂Membranes, so-called “CIGS” membranes).
[0003]
Conventional manufacturing methods of such a compound semiconductor thin film are generally roughly classified into a method using a vapor deposition method and a method using a sputtering method. Hereinafter, as an example of these methods, CuInSe₂Several typical methods for forming a film will be described.
[0004]
As a conventional method using a vapor deposition method, there is a method in which constituent elements of a target compound semiconductor thin film are supplied in multiple steps onto a high-temperature substrate by a vapor deposition method. In this method, a vapor deposition source in which a Cu evaporation source, an In evaporation source, and a Se evaporation source are installed, respectively, and a glass substrate having, for example, a Mo film on its upper surface is kept at room temperature in a vacuum chamber maintained at a predetermined pressure. In the state heated to a higher temperature of about 325 ° C., first, as a first stage, the In evaporation source and the Se evaporation source are heated and evaporated, and In and Se are supplied onto the substrate. An In—Se layer is formed. Next, as a second stage, the substrate is further heated to a high temperature of about 500 to 600 ° C., and in this state, the Cu evaporation source and the Se evaporation source are heated and evaporated, and Cu and Se are respectively supplied by a vapor deposition method. . At this time, since the substrate is in a high temperature state, Cu and Se supplied to the surface of the In—Se layer are not stacked on the In—Se layer but are taken into the In—Se layer to form a compound, Thereby, a Cu—In—Se compound layer grows. Finally, as a third stage, with the substrate kept at a high temperature, the In evaporation source and the Se evaporation source are heated and evaporated, and In and Se are respectively supplied by a vapor deposition method. Even at this stage, Cu and Se supplied to the surface of the Cu—In—Se layer are taken into this layer to form a compound, and the Cu—In—Se compound layer grows, and finally CuInSe.₂A film is formed.
[0005]
On the other hand, as a conventional method using the sputtering method, there is a method of supplying the constituent elements of the target compound semiconductor thin film onto the substrate in one step by the sputtering method. In this method, for example, a sputtering source in which a Cu target, an In target, and an Se target are respectively installed is provided, and each target is sputtered in a vacuum chamber maintained at a predetermined pressure, so that the above-described substrate is formed. Cu, In, and Se are simultaneously supplied to CuInSe.₂A film is grown and formed. As the target, a target made of any combination of materials selected from the group consisting of Cu, In, and Se can also be used.
[0006]
Further, as another conventional method using the sputtering method, a constituent element other than Se of the target compound semiconductor thin film is supplied onto the substrate in multiple stages by the sputtering method to form a laminated film, and then hydrogen selenide ( H₂There is a method of heat-treating a substrate in an Se) atmosphere. In this method, first, in a vacuum chamber maintained at a predetermined pressure, for example, a Cu target is sputtered onto the substrate as described above to supply Cu, and then an In target is sputtered to supply In. Thereby, a Cu film and an In film are sequentially formed to form a laminated film. Next, the obtained substrate is heated to about 500 ° C. in a hydrogen selenide atmosphere and subjected to heat treatment (also referred to as Se conversion treatment). At this time, the laminated film composed of the Cu film and the In film takes in Se and grows while forming a compound, and finally, CuInSe₂A film is formed.
[0007]
In addition to the above-described method, there is a method in which constituent elements other than Se of the target compound semiconductor thin film are supplied onto the substrate in one step by sputtering, and simultaneously, Se is deposited by evaporation. In this method, in a vacuum chamber maintained at a predetermined pressure, for example, a Cu target and an In target are sputtered, and Cu and In are respectively supplied onto the substrate as described above in one step, and at the same time, Se. The evaporation material is heated to evaporate, and Se is supplied by an evaporation method. As a result, Cu, In, and Se are simultaneously supplied, and CuInSe₂The film grows.
[0008]
CuInSe₂Although the method of forming the film has been described in detail, CuInGaSe₂A film and a similar thin film can be formed in substantially the same manner.
[0009]
[Problems to be solved by the invention]
In recent years, further increase in capacity (larger area), higher efficiency, and lower cost of thin film solar cells are desired. Accordingly, even for compound semiconductor thin films containing a group IB element, a group IIIB element, and a group VIB element used as a light absorption layer of a thin film solar cell, a thin film having a uniform and uniform film thickness over a large area. Establishment of forming technology is desired.
[0010]
However, none of the conventional methods for producing a compound semiconductor thin film as described above sufficiently satisfy such a demand.
[0011]
In the conventional manufacturing method using the vapor deposition method alone, generally, as a vapor deposition source, for example, a crucible around which a heater such as a metal wire is wound is used, an evaporation raw material is put into this crucible, and resistance heating is used under vacuum. The evaporation material is heated to evaporate, but such a method has a problem that the evaporation rate (or the evaporation rate or the supply rate) of the evaporation material changes depending on the amount of the evaporation material in the crucible. For this reason, in order to obtain a constant evaporation rate, it is preferable to control by appropriately changing the current passed through the heater according to the evaporation / consumption of the evaporation raw material, but such control is actually difficult. In addition, in the vapor deposition method using such a vapor deposition source, it is difficult to form a thin film with a uniform thickness on a large-area substrate. In addition to this, in the vapor deposition method, it is necessary to heat the substrate in a high temperature state (for example, about 500 to 600 ° C.) for a long time (for example, about 10 to 90 minutes). high.
[0012]
On the other hand, in the conventional manufacturing method using the sputtering method alone, the target of the raw material element is generally installed in the sputtering source, and the target is sputtered and evaporated by Ar ions or the like under vacuum. According to this method, since the fluctuation of the evaporation rate is small, it is easy to form a thin film with a uniform thickness on a large-area substrate as compared with the method using the evaporation method as described above. High controllability. However, when the VIB group element is supplied by the sputtering method, a part of the VIB group element released by sputtering evaporation from the VIB group element (or including it) target is negatively ionized, and the negative ionized VIB group element is formed into a film. There is a problem in that the surface is impacted to cause defects in the film.
[0013]
Further, according to the above-described conventional manufacturing method in which a laminated film is formed by sputtering and then heat-treated (or Se-treated) in a hydrogen selenide atmosphere, the defects as described above are alleviated by heat treatment after sputtering. The film quality can be improved. However, hydrogen selenide used in this method is a toxic gas, and the production is carried out in a work environment with high risk. Furthermore, it is necessary to install special incidental equipment such as a detoxification device in order to dispose of hydrogen selenide used in Se treatment and hydrogen as a by-product in the atmosphere. Installation of such equipment And additional costs for maintenance.
[0014]
On the other hand, according to the above-described conventional manufacturing method in which constituent elements other than Se are supplied onto the substrate in one step by a sputtering method and simultaneously by a vapor deposition method, the VIB group element is not a sputtering method but a vapor deposition method. Since it can be supplied, the problem of defect formation can be avoided, and furthermore, since toxic hydrogen selenide is not used, the production can be carried out in a safer working environment. However, in this method, since the IB group element and the IIIB element other than the VIB group element are supplied by the sputtering method and the VIB group element is supplied by the vapor deposition method, for example, Cu as the IB group element, In as the IIIB group element, and In / When using S and / or Se as a Ga, VIB group element, the low melting point group IIIB and VIB group elements are re-evaporated and insufficient, and the relatively high melting point group IB element is excessive, This causes a new problem that compositional deviation (that is, formation of a compound having a composition deviated from the composition of the target compound) is likely to occur as compared with other methods.
[0015]
The phenomenon in which such a composition shift occurs is, for example, when Cu is used as the IB group element, In is used as the IIIB group element, and Se is used as the VIB group element. And Se are high melting point In on the substrate supply surface.₂Se_ThreeSince the compound phase was initially formed, it was not seen because the low-melting elements (in this case In and Se) were prevented from re-evaporating. However, when Se is supplied by a vapor deposition method and Cu and In are simultaneously supplied by a sputtering method, the energy of Se particles supplied by the vapor deposition method is compared with the energy of In particles supplied by the sputtering method. Much smaller, In₂Se_ThreeSince it becomes difficult to form a compound phase, more In and Se are re-evaporated than when all elements are supplied by the sputtering method, while the high melting point Cu supplied simultaneously with In and Se is regenerated. Since evaporation hardly occurs, it is relatively excessive with respect to In and Se. As a result, it is considered that a large composition shift tends to occur in some cases in a method in which sputtering and vapor deposition are simultaneously used and supplied onto the substrate in only one stage.
[0016]
This problem of compositional deviation also occurs when Ga is used as the IIIB group element and S is used as the VIB group element. This is because Ga and S also have a low melting point and are easily re-evaporated.
[0017]
The present invention has been made to solve the conventional problems as described above, and an object of the present invention is a method for producing a compound semiconductor thin film containing a group IB element, a group IIIB element and a group VIB element, A novel manufacturing method that at least partially ameliorates conventional problems such as non-uniform film thickness over a large area, occurrence of large compositional deviations, generation of crystal defects, high risk of working environment, high manufacturing cost, etc. Another object of the present invention is to provide an apparatus capable of carrying out such a method, and a compound semiconductor thin film obtained thereby.
[0018]
Throughout this specification, the term “sputtering method” refers to accelerating ionized gas atoms (for example, Ar ions) and using this to release raw material particles from a target of a raw material element provided in a sputtering source by a sputtering phenomenon ( (Or sputtering evaporation). The “evaporation method” refers to a method of evaporating raw material particles by heating an evaporation material provided in an evaporation source under a so-called vacuum.
[0019]
[Means for Solving the Problems]
The method of the present invention is a method for producing a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element, comprising: (a) supplying at least a predetermined raw material element on a substrate using a sputtering method; Forming a precursor thin film containing a group IB element and a group IIIB element or a precursor thin film containing a group IB element, a group IIIB element and a group VIB element on a substrate; and (b) using a method other than sputtering. While supplying the VIB group element onto the precursor thin film, the substrate on which the precursor thin film is formed is heat-treated at a temperature higher than the temperature in the step (a), and from the precursor thin film, the group IB element, group IIIB Forming a compound semiconductor thin film containing an element and a VIB group element on a substrate.
[0020]
According to the method of the present invention as described above, since the precursor thin film is formed by using the sputtering method in the step (a), the thickness of the compound semiconductor thin film obtained therefrom is uniform over a large area. It is suitable for forming a compound semiconductor thin film on a large-area substrate.
[0021]
Furthermore, according to the method of the present invention, since it is not necessary to supply the VIB group element using a sputtering method, the introduction of crystal defects resulting from the ionization of the VIB group element is reduced in the compound semiconductor thin film. However, the method of the present invention optionally includes supplying the group VIB element using a sputtering method in step (a), in which crystal defects may be introduced into the precursor thin film, but the subsequent step ( In b), since the VIB group element is supplied onto the precursor thin film using a method other than sputtering and the substrate is heat-treated at a high temperature, the introduced crystal defects can be relaxed and reduced. Therefore, the generation of crystal defects is reduced by the method of the present invention.
[0022]
Further, according to the method of the present invention, the time for maintaining the substrate at a high temperature is shortened as compared with the conventional method using the vapor deposition method alone. This provides an inexpensive method for manufacturing a compound semiconductor thin film with relatively low power consumption. This method is a safe manufacturing method that does not use a toxic gas such as hydrogen selenide, and there is no need to provide incidental equipment.
[0023]
In the present invention, the group IB element, the group IIIB element and the group VIB element can be arbitrarily selected based on the periodic table. For example, the group IB element is either or both of Ag and Cu, and the group IIIB The element can be either or both of In and Ga, and the VIB group element can be either or both of Se and S. More preferably, the group IB element is Cu, the group IIIB element is In, or In and Ga, the group VIB element is Se, and CuInSe containing these elements₂Film or Cu (In, Ga) Se₂The film is manufactured according to the method of the present invention as a compound semiconductor thin film. However, the present invention is not limited to this, and other compound semiconductor thin films (for example, CuInS)₂, CuGaSe₂, CuGaS₂, Cu (In, Ga) S₂, Cu (In, Ga) (S, Se)₂, CuIn_ThreeSe_Five, CuIn_ThreeS_Five, CuGa_ThreeSe_Five, CuGa_ThreeS_Five, Cu (In, Ga)_ThreeSe_Five, Cu (In, Ga)_ThreeS_Five, And Cu (In, Ga)_Three(S, Se)_FiveOr a compound semiconductor thin film in which a small amount of other elements are dissolved in addition to the IB group element, the IIIB group element and the VIB group element.
[0024]
In the present invention, the “precursor thin film” refers to a semiconductor layer before the target compound semiconductor thin film is formed, and may be a multilayer or a single layer depending on the formation mode of the precursor thin film and the substrate temperature at this time. This precursor thin film contains a group IB element and a group IIIB element, and may or may not contain a group VIB element.
[0025]
The “method other than the sputtering method” refers to a method of supplying a target raw material element to a predetermined place other than the sputtering method. Examples of such a method include a vapor deposition method, laser ablation, proximity sublimation method, and the like, and a method of using these in any combination, and a vapor deposition method is preferable.
[0026]
As a substrate that can be used in the present invention, for example, a glass substrate, a metal substrate, a metal film, a resin substrate, a resin film, or the like can be used. Further, such a substrate is used as a substrate body on which, for example, Mo, MoSe.₂, Pt, Au, Cr, Ni, AgPdCu, WSi, etc., and in particular when a glass substrate, a transparent metal film or a resin film is used, the conductive film made of such a material. Instead, ITO, ZnO: Al, SnO₂A transparent conductive film such as ZnO and a window layer such as ZnO may be provided.
[0027]
Hereinafter, the method of the present invention will be described in detail.
[0028]
In the step (a), a precursor thin film containing a group IB element and a group IIIB element, or a group IB element, by supplying a predetermined raw material element onto the substrate using at least a sputtering method, A precursor thin film containing a group IIIB element and a group VIB element is formed on the substrate.
[0029]
In a preferred embodiment, the temperature of the substrate in step (a) is in the range of 20 to 450 ° C, more preferably in the range of 300 to 400 ° C.
[0030]
Here, a method of supplying a group IB element and a group IIIB element using a sputtering method includes a target composed of a group IB element (for example, a Cu target), a target composed of a group IIIB element (for example, an In target), and a group IB element. A target composed of a group IIIB element (for example, a Cu-Ga target), a group composed of a group IB element and / or a group IIIB element and an element other than these elements (for example, a group VIB element) (for example, a Cu-Se target, In- (Se target, Cu-In-Se target, Cu-Ga-Se target) may be sputtered.
[0031]
At this time, in order to form the precursor thin film, not only the IB group element and the IIIB group element (and possibly other elements) are supplied using the sputtering method, but also a method other than the sputtering method is used in combination. May be. For example, the IB group element and / or the IIIB group element may be supplied by a sputtering method, and the VIB group element may be supplied by a method other than the sputtering method such as an evaporation method. In addition, for example, the IB group element and / or the IIIB group element may be supplied by a sputtering method, and at the same time, the same kind of element may be supplied by a method other than the sputtering method such as an evaporation method.
[0032]
In a preferred embodiment, the step (a) includes a first step of supplying a group IIIB element or supplying a group IIIB element and a group VIB element, and a group IB element and a group VIB element supplying a group IB element. Supplying, supplying a group IB element and a group IIIB element, or supplying a group IB element, a group IIIB element and a group VIB element.
[0033]
In this aspect, the order of performing the first step and the second step may be the second step after the first step is performed or vice versa.
[0034]
According to this aspect, although depending on the temperature of the substrate, a structure of two or more layers comprising the layer formed by the first step and the layer formed by the second step (however, the first step and the second step are respectively When implemented in one step, a precursor thin film having a two-layer structure can be formed on the substrate.
[0035]
Further, according to this aspect, the group IB element and the group IIIB element are supplied by the sputtering method, and at the same time, the group VIB element is supplied by the vapor deposition method, so that it is not formed in one step. Even when In and / or Ga is used as a group element and Se and / or S is used as a VIB group element, a compound semiconductor thin film having a desired composition can be formed without causing a large composition shift.
[0036]
The first step can be performed, for example, as follows.
(1-1) A group IIIB element target (for example, an In target) is used to supply a group IIIB element by a sputtering method.
(1-2) Supplying a Group IIIB element and a Group VIB element by sputtering using at least one target (for example, an In-Se target and, if necessary, an In target) containing a Group IIIB element and a Group VIB element Or
(1-3) A group IIIB element is supplied by a sputtering method using a group IIIB element target (for example, an In target), and at the same time a group VIB element is deposited by a vapor deposition method using a group VIB element evaporation source (for example, an Se evaporation source). Supply.
[0037]
Moreover, the said 2nd process can be implemented as follows, for example.
(2-1) supplying a group IB element by a sputtering method using a group IB element target (for example, a Cu target);
(2-2) Supplying a group IB element and a group VIB element by a sputtering method using at least one kind of target (for example, a Cu-Se target and, if necessary, a Cu target) containing a group IB element and a group VIB element ,
(2-3) A group IB element is supplied by sputtering using a group IB element target (for example, Cu target), and simultaneously a group VIB element is deposited by vapor deposition using a group VIB element evaporation source (for example, Se evaporation source). Supply,
(2-4) IB group elements and IIIB group elements are supplied by sputtering using at least one target (for example, a Cu-Ga target and optionally a Cu target) containing a group IB element and a group IIIB element. ,
(2-5) Using at least one kind of target (for example, Cu-In-Se target or Cu-Ga-Se target) containing a group IB element, a group IIIB element, and a group VIB element, a group IB element, a group IIIB element, and Supply VIB group elements by sputtering, or
(2-6) Supplying a group IB element and a group IIIB element by a sputtering method using at least one kind of target containing a group IB element and a group IIIB element (for example, a Cu-Ga target and, if necessary, a Cu target). At the same time, the VIB group element is supplied by vapor deposition using the VIB group element evaporation raw material (for example, Se evaporation raw material).
[0038]
The first step and the second step are independent of each other from the above-mentioned first step examples (1-1) to (1-3) and the second step examples (2-1) to (2-6). One or more can be selected, and can be implemented in any appropriate combination depending on the constituent elements of the compound semiconductor thin film to be formed. The above example (1-1) or (1-2) as the first step, the above example (2-2) and / or (2-4) as the second step, or the above as the first step The combination of Example (1-3) and Example (2-3) and / or (2-4) above is preferable as the second step.
[0039]
In a preferred embodiment, the second step includes supplying a group IB element, or supplying a group IB element and a VIB element, step A, supplying a group IB element and a group IIIB element, or providing a group IB element, And a second B step of supplying a group IIIB element and a group VIB element.
[0040]
In this embodiment, the first step, the second A step, and the second B step can be performed in any appropriate combination order. Specifically, (first process, 2A process, 2B process), (first process, 2B process, 2A process), (2A process, 2B process, 1st process), (2B process) You may implement in any order of a process, 2A process, 1st process), (2A process, 1st process, 2B process), and (2B process, 1st process, 2A process).
[0041]
In this aspect, the second step in the above-described aspect is performed in two stages. According to this aspect, although it depends on the temperature of the substrate, a structure of three or more layers comprising a layer formed by the first step, a layer formed by the second A step, and a layer formed by the second B step (however, When the first step, the second A step, and the second B step are each performed in one step, a precursor thin film having a three-layer structure can be formed on the substrate.
[0042]
The second 2A step can be performed, for example, by any one of the above (2-1) to (2-3). Moreover, 2nd B process can be implemented by either of said (2-4)-(2-6), for example.
[0043]
Also in this embodiment, the first step, the second A step, and the second B step are the above-described first step examples (1-1) to (1-3) and the second A step examples (2-1) to (2). -3) and the examples (2-4) to (2-6) of Step 2B can be selected independently from each other, and can be carried out in any appropriate combination. The above example (1-1) or (1-2) as the first step, the above example (2-2) as the 2A step, and the above example (2-4) as the 2B step, Alternatively, the combination of the above example (1-3) as the first step, the above example (2-3) as the 2A step, and the above example (2-4) as the 2B step is preferable.
[0044]
Next, in the step (b), the substrate is heated to a temperature higher than that in the step (a) while supplying the VIB group element using a method other than the sputtering method onto the precursor thin film formed as described above. Heat treatment at temperature.
[0045]
Specifically, for example, while supplying a VIB group element, the substrate is heated to a predetermined temperature, maintained at a predetermined temperature for a predetermined time as necessary, and then cooled to near the substrate temperature in step (a). Heat treatment can be performed by stopping the supply of the group VI element when the pressure reaches the maximum. Alternatively, while supplying the VIB group element, the substrate is heated to reach a predetermined temperature, or if necessary, after maintaining the predetermined temperature for a predetermined time, the supply of the VI group element is stopped, and then the step (a The substrate can be heat-treated so that the substrate is cooled to around the substrate temperature.
[0046]
In a preferred embodiment, the temperature of the substrate in step (b) is raised to a temperature in the range of 300 to 600 ° C. and higher than the temperature of the substrate in step (a), more preferably 450 to 550 ° C. Is raised to a temperature in the range of. The heat treatment in step (b) is preferably performed for about 1 second to 10 minutes.
[0047]
In the step (b), since the substrate is heat-treated at the high temperature as described above, the precursor thin film takes in the VIB group element and grows while forming the compound, and the IB group element and the IIIB group element are formed from the precursor thin film. , And a compound semiconductor thin film containing a VIB group element is formed on the substrate.
[0048]
In another aspect of the present invention, one or more sputter sources for forming the precursor thin film on the substrate, a sputter source shutter provided in each sputter source, temperature control means for controlling the temperature of the substrate, An apparatus for manufacturing a compound semiconductor thin film is provided, which includes a supply source for supplying a group VIB element onto the precursor thin film using a method other than sputtering. Here, the sputtering source shutter has an effect of preventing the target provided in the sputtering source from being contaminated with another substance, for example, a VIB group element released from the supply source, but the contamination of the target is not a problem. If it is, it can be omitted.
[0049]
In one preferable aspect, the supply source is housed in a chamber different from the chamber in which the sputter source is housed. When a plurality of sputter sources are provided, the plurality of sputter sources are also different from each other. More preferably, it is arranged in the chamber. In this embodiment, the target provided in the sputtering source is not contaminated by the VIB group element supplied from the supply source, and the contamination of the target is negligible. Therefore, the sputtering source shutter is not necessarily provided in each sputtering source. Good.
[0050]
In another preferred embodiment, the supply source and the sputtering source are accommodated in the same chamber and separated from each other by a partition plate provided therebetween. When a plurality of sputtering sources are provided, it is more preferable that the plurality of sputtering sources are also partitioned from each other by a partition plate. Also in this embodiment, since the target provided in the sputtering source is not contaminated by the VIB group element supplied from the supply source, it is not always necessary to provide a sputtering source shutter for each sputtering source.
[0051]
The apparatus of the present invention can be suitably used for carrying out the above-described method for producing a compound semiconductor of the present invention. As the sputtering source usable in the apparatus of the present invention, a sputtering source known in the art can be used, and one or more sputtering sources depending on the number of targets used for forming the precursor thin film. Is provided. Also in the apparatus of the present invention, similarly to the above-described method of the present invention, any method selected from the group consisting of vapor deposition, laser ablation, and proximity sublimation or any of these may be used as a method other than sputtering. These methods are used in combination, preferably a vapor deposition method, and the supply source is a supply source using these methods, preferably a vapor deposition source. As the vapor deposition source, a vapor deposition source known in the art can be used. For example, a crucible in which a resistance heater is contacted indirectly or directly can be used.
[0052]
In still another aspect of the present invention, there is provided a thin-film solar battery including a compound semiconductor thin film formed according to the method of the present invention as described above as a light absorption layer. Alternatively, in a thin film solar cell including a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element as a light absorption layer, the compound semiconductor thin film is 3 cm × 3 cm (3 cm □) or more, further 10 cm × 10 cm or more, Further, a thin film solar cell having a surface roughness value in the range of 0.01 to 0.5 μm, and further in the range of 0.01 to 0.3 μm is provided over a large area of 30 cm × 30 cm or more. “Surface roughness” refers to the center line average roughness of irregularities on the exposed surface of a compound semiconductor thin film formed on a substrate.
[0053]
The compound semiconductor thin film of the present invention can be obtained, for example, by performing the above-described method for producing a compound semiconductor of the present invention using the apparatus of the present invention as described above. This compound semiconductor thin film has a good film quality in which the film thickness is uniform over a large area, composition deviation hardly occurs, generation of crystal defects is reduced, surface roughness is relatively small, and crystal grains are large. Therefore, the compound semiconductor thin film of the present invention can be advantageously used as a light absorption layer of a large area and high efficiency thin film solar cell.
[0054]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
As a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element, Cu (In, Ga) Se₂One embodiment of the present invention for forming a film will be described with reference to FIGS. FIG. 1A is a schematic view of the compound semiconductor thin film manufacturing apparatus of the present embodiment, and FIG. 1B is a top view taken along the line XX ′ of the apparatus of FIG. It is. 2 (a) and 2 (b) are schematic process diagrams for explaining the method for producing a compound semiconductor thin film of the present embodiment, and show schematic sectional views of the substrate on which the precursor thin film and the compound semiconductor thin film are formed, respectively. . The present embodiment relates to a case where the above example (1-3) is performed as the first step and the above examples (2-3) and (2-4) are performed as the second step.
[0055]
As shown in FIGS. 1A and 1B, the compound semiconductor thin film manufacturing apparatus 20 of the present embodiment includes a vapor deposition source 2 as a VIB group element supply source, a group IB element, Three sputtering sources 3a, 3b and 3c for supplying a group IIIB element onto the substrate by sputtering and forming a precursor thin film containing the group IB element and the group IIIB element on the substrate; And a lamp heater 6 for heating the heater. In this embodiment, the vapor deposition source 2 is for arrange | positioning Se evaporation raw material. The sputtering sources 3a, 3b, and 3c are arranged with an In target that is a group IIIB element target, a Cu target that is a group IB element target, and a Cu-Ga target that is a target composed of a group IB element and a group IIIB element, respectively. However, these three targets may be arranged in any combination in the three sputtering sources 3a, 3b, and 3c.
[0056]
In the present embodiment, an apparatus including three sputtering sources for forming a precursor thin film by sputtering three targets is shown, but the present invention is not limited to this. One, two, or four or more targets may be used depending on the formation mode of the precursor thin film, and in that case, it is a person skilled in the art to use an apparatus having a number of sputtering sources corresponding to the number of targets. Will be easily understood.
[0057]
In this apparatus 20, a substrate 5 attached to a soaking plate 4 made of a carbon material is supported by using a susceptor (or holder) 7 with the soaking plate 4 facing the heater 6. The heater 6 uniformly heats the substrate 5 through the soaking plate 4, and is a surface on the side of the substrate 5 on which a film is formed (that is, an exposed surface opposite to the soaking plate 4, see FIG. 2). The temperature of an exposed surface of the conductive film 5a described later can be controlled to a desired value. The susceptor 7 is connected to the rotation drive shaft 8, and the rotation of the rotation drive shaft 8 causes the susceptor 7 to rotate, causing the substrate 5 and the heat equalizing plate 4 to rotate. Further, in the chamber 1, the deposition source 2, the sputter source 3 a, the sputter source 3 b, and the sputter source 3 c are controlled so as to control the supply of each raw material particle (Cu, In, Ga, and Se) to the surface of the substrate 5. And a shutter 9 disposed between the substrate 5 and the substrate 5. In order to prevent Se that evaporates from the vapor deposition source 2 from adhering to the targets provided in the respective sputtering sources 3a to 3c when the voltage is not applied to the sputtering source, for example, a slide is used for the sputtering sources 3a, 3b, and 3c. Sputter source shutters 3A, 3B, and 3C (shown by dotted lines in FIGS. 1A and 1B) such as an openable shutter are provided. The soaking plate 4, the rotary drive shaft 8, and the shutter 9 are not necessarily required for carrying out the present invention, but are preferably provided with them.
[0058]
Each of the sputter sources 3a, 3b, and 3c is switchably connected to a grounded DC power source (not shown), thereby controlling voltage application. Note that an RF (high frequency) power source may be used instead of the DC (direct current) power source, and in this case, the RF power source can be used together with a matching unit, a capacitor, and the like. An exhaust line 10 for evacuating the chamber 1 and an Ar gas line 11 for supplying Ar gas into the chamber 1 are connected to the chamber 1.
[0059]
Next, the manufacturing method of the compound semiconductor thin film of this embodiment using such an apparatus 20 will be described.
[0060]
1. Preparation
First, the conductive film 5a made of Mo or the like as shown in FIG. 2 is formed on the substrate body 5b made of glass. The substrate 5 shown in FIG. It is attached so as to contact the hot platen 4. On the other hand, the chamber 1 is evacuated from the exhaust line 10 using a pump (not shown) or the like. In this chamber 1, a substrate 5 attached to a soaking plate 4 is placed on a susceptor 7 as shown in FIG. 1, and an Se evaporation raw material, an In target, a Cu target, and a Cu—Ga target are used as a deposition source 2 and a sputtering source, respectively. 3a, sputter source 3b and sputter source 3c. At this time, no voltage is applied to each sputtering source, and the sputtering source shutters 3A to 3C and the shutter 9 are closed.
[0061]
Next, the substrate 5 is uniformly heated using the heater 6 through the soaking plate 4 so that the surface of the Mo film 5a of the substrate 5 is, for example, about 20 to 450 ° C., preferably about 300 to 400 ° C. The heating is controlled, and on the other hand, Ar gas is supplied from the Ar gas supply line 11 into the chamber 1. When the substrate 5 reaches a predetermined temperature and reaches a substantially constant temperature, the rotation drive shaft 8 is rotated to rotate the susceptor 7, thereby rotating the substrate 5 and the soaking plate 4. At this time, the supply and exhaust of Ar gas are controlled so that the pressure in the chamber 1 is maintained at a predetermined pressure while the supply of Ar gas is maintained.
[0062]
2. Step (a)
2-1. First step
Thereafter, the sputtering source shutter 3A of the sputtering source 3a on which the In target is installed is opened, a voltage is applied by connecting the sputtering source 3a to a power source, and the vapor deposition source 2 on which the Se evaporation source is installed is heated. At this time, if necessary, pre-sputtering may be performed to clean the surface of the In target. When In and Se are stably released, the shutter 9 is opened and, as the first step, In is supplied to the surface of the substrate 5 by sputtering and Se is supplied by evaporation. After a predetermined time elapses, for example, after 3 to 60 minutes, the shutter 9 and the sputtering source shutter 3A are closed, the voltage application of the sputtering source 3a is stopped, and the In emission is finished. By this first step, the first layer 12 (see FIG. 2A) made of In—Se is formed on the Mo film 5a of the substrate 5.
[0063]
2-2. Second step
Next, while maintaining the heating of the Se deposition source 2 following the first step, the sputtering source shutters 3B and 3C of the sputtering sources 3b and 3c on which the Cu target and the Cu—Ga target are respectively installed are opened, and the sputtering source 3b And 3c are each connected to a power source to apply a voltage. At this time, if necessary, pre-sputtering may be performed to clean the surface of the Cu target and the Cu—Ga target. When Cu and Ga are stably released, the shutter 9 is opened, and as a second step, Se is deposited by vapor deposition, Cu and Ga is sputtered by sputtering, and more specifically on the surface of the first layer 12. To supply. After a predetermined time has elapsed, for example, after 1 to 30 minutes, the shutter 9 and the sputtering source shutters 3B and 3C are closed, the voltage application of the sputtering sources 3b and 3c is stopped, and the emission of Cu and Ga is completed. By this second step, the second layer 13 (see FIG. 2A) made of Cu—Ga—Se is formed on the first layer 12.
[0064]
As described above, the precursor thin film 14 in which the first layer 12 and the second layer 13 are sequentially laminated as shown in FIG. 2A is formed through the first step and the second step.
[0065]
3. Step (b)
After the precursor thin film 14 is formed by the above-described step (a), the Ar gas supply is preferably stopped while maintaining the heating of the Se vapor deposition source 2 following the first and second steps, and the shutter 9 is again turned on. And Se is supplied to the surface of the precursor thin film 14 by a vapor deposition method. While supplying Se in this way, the temperature of the surface of the Mo film 5a of the substrate 5 is higher than that at the time of forming the precursor thin film, for example, about 300 to 600 ° C. and higher than in step (a), Preferably, the heating from the heater 6 is controlled to be about 450 to 550 ° C. After a predetermined time has elapsed, preferably after about 1 second to 10 minutes, heating of the heater 6 is stopped. Thereafter, when the substrate temperature decreases to a temperature in the vicinity of the step (a), the shutter 9 is closed, the heating of the vapor deposition source 2 is stopped, and the release of Se is completed. Through this process, Se is taken into the precursor thin film 14 and a compound is formed. From the precursor thin film 14, Cu (In, Ga) Se is formed.₂A thin film 15 (see FIG. 2B) is formed.
[0066]
By the steps (a) and (b) as described above, Cu (In, Ga) Se as shown in FIG.₂A compound semiconductor thin film 15 is formed.
[0067]
The obtained compound semiconductor thin film 15 has a large area of 3 cm × 3 cm or more, further 10 cm × 10 cm, and further 30 cm × 30 cm or more, in the range of about 0.01 to 0.5 μm, further 0.01 to It has a surface roughness in the range of 0.3 μm. This value is a relatively small value, and it can be seen that the compound semiconductor thin film has a smooth surface.
[0068]
According to the present embodiment, a precursor thin film is formed using a sputtering method in the step (a), and then heat treatment is performed while supplying Se in the step (b). In such a method, the film thickness of the compound semiconductor thin film can be made uniform over a large area as compared with the method of forming the compound semiconductor thin film using only the conventional vapor deposition method.
[0069]
Further, according to the present embodiment, Se, which is a VIB group element, is not supplied using a sputtering method, but is supplied using a vapor deposition method, and further, the precursor thin film formed in the step (a) is subjected to a heat treatment. Therefore, the crystal defects introduced into the compound semiconductor thin film are reduced as compared with the conventional method of forming the compound semiconductor thin film using only the sputtering method in one step. Instead of this embodiment, it is possible to supply Se by sputtering using a Cu—Se target or the like in the step (a). In this case, the precursor is obtained by a heat treatment in the subsequent step (b). Since crystal defects that can be introduced into the body thin film are alleviated, crystal defects introduced into the compound semiconductor thin film are reduced as compared with the conventional method.
[0070]
Further, according to the present embodiment, the IB group element (Cu) and the IIIB group element (In) are supplied by the sputtering method, and at the same time, the VIB group element (Se) is not supplied by the vapor deposition method, and In and Se are supplied. Since it is supplied separately from the supply of Cu, it is possible to form a compound by sufficiently reacting In and Se, which are easily re-evaporated, without causing a relative excess of Cu. Thereby, a compound semiconductor thin film with reduced composition deviation can be formed.
[0071]
Furthermore, according to the present embodiment, an inexpensive method for producing a compound semiconductor thin film is provided in which the time for maintaining the substrate at a high temperature is shortened as compared with the conventional method using the vapor deposition method alone, and the power consumption is smaller. The This method is a safe manufacturing method that does not use a toxic gas such as hydrogen selenide.
[0072]
In addition, according to the present embodiment, the sputtering source shutter is provided in the sputtering source, and when the sputtering source is not used, the target provided in the sputtering source can be covered with the sputtering source shutter. It is possible to prevent the sputtering source from being contaminated by the VIB group element (Se) released from the source.
[0073]
As described above, the compound semiconductor thin film obtained according to the present embodiment is uniform because the film thickness is uniform over a large area, the occurrence of crystal defects is reduced, the composition deviation is reduced, and the surface roughness is small. It has a film quality and can be advantageously used as a light absorbing layer of a large area and high efficiency thin film solar cell.
[0074]
In the present embodiment, as the first layer, In is supplied by the sputtering method and Se is supplied by the vapor deposition method to form the In—Se layer, but instead of this, the supply of Se is omitted. A layer may be formed. In the present embodiment, as the second layer, Cu and Ga are supplied by the sputtering method, and at the same time, Se is supplied by the vapor deposition method to form the Cu-Ga-Se layer. Instead, the supply of Se is performed. You may abbreviate | omit and form a Cu-Ga layer.
[0075]
Furthermore, although the Cu-target and the Cu-Ga target are used in the present embodiment, the Cu target can be used alone or a Cu-Se target can be used instead. In the case of using a Cu target, Cu is supplied by a sputtering method in the second step, and a Cu layer is formed as the second layer, or Cu is supplied by a sputtering method and at the same time, Se is supplied by an evaporation method. A Cu—Se layer may be formed as the second layer. Moreover, when using a Cu-Se target, Cu and Se may be supplied by a sputtering method in a 2nd process, and a Cu-Se layer may be formed as a 2nd layer. Also by such a method, CuInSe as in the present embodiment.₂It is possible to form a film.
[0076]
In this embodiment, the first step and the second step are performed in this order, and the In—Se layer (or In layer) is used as the first layer, and the Cu—Ga—Se layer (or Cu—) is used as the second layer. (Ga layer, Cu layer, or Cu—Se layer) is formed, but the order of performing the first step and the second step can be reversed. That is, the second step is performed first to form a Cu—Ga layer (or Cu—Ga—Se layer, Cu layer, or Cu—Se layer) as the first layer, and then the second step is performed to perform the first step. An In—Se layer (or In layer) may be formed as two layers.
[0077]
In addition to the above modifications, the present embodiment can be variously modified by those skilled in the art. For example, the vapor deposition method is used to supply the VIB group element (Se), but other methods other than the sputtering method may be used. In addition, an appropriate gas other than Ar gas can be used to perform the sputtering method, and the shutter opening / closing timing can be changed.
[0078]
(Embodiment 2)
As a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element, Cu (In, Ga) Se₂Another embodiment of the present invention for forming a film will be described with reference to FIG. 3 (a) and 3 (b) are schematic process diagrams for explaining the method for producing a compound semiconductor thin film of the present embodiment, and show schematic sectional views of the substrate on which the precursor thin film and the compound semiconductor thin film are formed, respectively. .
[0079]
  This embodimentIII Group B elements and VI Supply group B elements, III Group B elements and VI Forming a first layer comprising a group B element (i), a group IB element and III Supply Group B element, Group IB element and III Forming a second layer comprising a group B element ( ii ) Group IB elements and VI Supply Group B element, Group IB element and VI Forming a third layer comprising a group B element ( iii ) In sequence. In addition, these process (i), process ( ii ) And process ( iii ) Is included in each of the first step, the second B step, and the second A step in the present specification. This embodiment is more specifically described in step (i).The above example (1-3) was carried out asProcess ( ii )Perform the above example (2-4) asProcess ( iii )As for what implements the above example (2-3), it is carried out using the same apparatus as the compound semiconductor thin film manufacturing apparatus (FIGS. 1A and 1B) detailed in the first embodiment. Can do. Hereinafter, the manufacturing method of the compound semiconductor thin film of the present embodiment will be described focusing on differences from the first embodiment.
[0080]
1. Preparation
First, preparation is performed in the same manner as in the first embodiment. Also in this embodiment, the heating is controlled so that the surface of the Mo film 5a of the substrate 5 becomes, for example, about 20 to 450 ° C., preferably about 300 to 400 ° C., and the pressure in the chamber is kept at a predetermined pressure. Control the supply and exhaust of Ar gas.
[0081]
  2. Step (a)
    2-1.Step (i)
  Thereafter, In and Se are supplied to the surface of the substrate 5 by a sputtering method and a vapor deposition method, respectively, in the same manner as in the first step of the first embodiment. thisStep (i)As a result, the first layer 12 (see FIG. 3A) made of In—Se is formed on the Mo film 5a of the substrate 5.
[0082]
    2-2.Process ( ii )
  Next, a sputtering source in which a Cu target and a Cu—Ga target are respectively installed is performed in the same manner as in the second step of Embodiment 1 except that the heating of the Se vapor deposition source is stopped and the supply of Se is stopped. Then, Cu and Ga are supplied on the surface of the substrate, more specifically, on the first layer 12 by a sputtering method for a predetermined time, for example, 1 to 30 minutes. thisProcess ( ii )Thus, the second layer 16 (see FIG. 3A) made of Cu—Ga is formed on the first layer 12.
[0083]
    2-3.Process ( iii )
  Subsequently, while maintaining the release of Cu from the Cu sputter source, the Se deposition source was heated again,Process ( iii )As described above, Cu and Se are supplied on the surface of the substrate 5, more specifically, on the second layer 16 by a sputtering method and a vapor deposition method, respectively, for a predetermined time, for example, 1 to 30 minutes. thisProcess ( iii )Thus, the third layer 17 (see FIG. 3A) made of Cu—Se is formed on the second layer 16.
[0084]
  As above,Step (i),Process ( ii ),andProcess ( iii )After that, a precursor thin film 18 in which the first layer 12, the second layer 16, and the third layer 17 are sequentially laminated as shown in FIG. 3A is formed.
[0085]
3. Step (b)
After forming the precursor thin film 18 by the above step (a), the temperature of the surface of the Mo film 5a of the substrate 5 is higher than that at the time of forming the precursor thin film in the same manner as in the step (b) of the first embodiment. The heating is controlled to be, for example, about 300 to 600 ° C. and higher than that in step (a), preferably about 450 to 550 ° C., and then Se is deposited on the surface of the precursor thin film 18 by vapor deposition. To supply. Through this process, Se is taken into the precursor thin film 18 and a compound is formed together. From the precursor thin film 18, Cu (In, Ga) Se is formed.₂A thin film 19 (see FIG. 3B) is formed.
[0086]
By the steps (a) and (b) as described above, Cu (In, Ga) Se as shown in FIG.₂A compound semiconductor thin film 19 is formed.
[0087]
Also according to the present embodiment, the same effects as those of the first embodiment can be obtained.
[0088]
In this embodiment, an In layer may be formed as the first layer instead of the In—Se layer, and a Cu—Ga—Se layer is formed as the second layer instead of the Cu—Ga layer. May be. Furthermore, as the third layer, Cu was supplied by the sputtering method and Se was supplied by the vapor deposition method to form a Cu-Se layer. Instead, the supply of Se was omitted to form the Cu layer. Also good.
[0089]
  In this embodiment,Step (i),Process ( ii ),andProcess ( iii )In this order, the In—Se layer (or In layer) is used as the first layer, the Cu—Ga layer (or Cu—Ga—Se layer) as the second layer, and then the Cu—Se layer (as the third layer). Or Cu layer)Step (i),Process ( ii ),andProcess ( iii )It is also possible to change the order of performing. For example, process(I)After forming the In—Se layer (or In layer) as the first layer,Process ( iii )To form a Cu-Se layer (or Cu layer),Process ( ii )And a Cu—Ga layer (or Cu—Ga—Se layer) may be formed as the third layer. Or firstProcess ( ii )To form a Cu-Ga layer (or Cu-Ga-Se layer) as the first layer,Process ( iii )To form a Cu-Se layer (or Cu layer)(I)And an In—Se layer (or In layer) may be formed as the first layer.
[0090]
In the first embodiment and the second embodiment described above, the precursor thin film having two layers and three layers is formed by using the apparatus having three sputter sources, respectively. However, the apparatus having one sputter source is used. One skilled in the art would also be able to form a single layer precursor thin film or to form a precursor thin film of any suitable number of layers using an apparatus comprising two or more sputter sources. It can be easily conceived.
[0091]
(Embodiment 3)
Another compound semiconductor thin film manufacturing apparatus that can be used for manufacturing a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element will be described with reference to FIG. FIG. 4 is a schematic diagram of the compound semiconductor thin film manufacturing apparatus of the present embodiment. In FIG. 4, the same members as those of the apparatus described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
[0092]
As shown in FIG. 4, the compound semiconductor thin film manufacturing apparatus 30 of the present embodiment includes two chambers 1a and 1b. The chamber 1a is provided with three sputter sources 3a, 3b and 3c (however, the sputter source 3c is not shown in FIG. 4), while the chamber 1b has a VIB group element supply source. The vapor deposition source 2 is provided. Exhaust lines 10a and 10b are connected to the chambers 1a and 1b, respectively, and an Ar gas line 11 is further connected to the chamber 1a. Inside the chambers 1a and 1b, a lamp heater 6, a susceptor 7, a rotation drive shaft 8, and a shutter 9 are provided in common.
[0093]
In the manufacturing apparatus 30 of this embodiment, the vapor deposition source 2 which is a VIB group element supply source is arrange | positioned in the chamber 1b different from the chamber 1a in which the sputtering sources 3a, 3b, and 3c are arrange | positioned. Therefore, in this embodiment, since the sputtering source and the vapor deposition source are arranged in separate chambers, Se that is evaporated and released from the vapor deposition source adheres to the target provided in the sputtering source and contaminates the target. Therefore, it is not always necessary to provide a sputtering source shutter for each sputtering source.
[0094]
In the apparatus 30 of the present embodiment, the step (a) is performed in the chamber 1a using only the sputtering method in the first and second embodiments, and then the substrate is transferred from the chamber 1a to the chamber 1b. The method for producing a compound semiconductor thin film of the present invention can be carried out by modifying the step (b) at 1b.
[0095]
According to the apparatus of the present embodiment, when the vapor deposition source is used as the supply source of the VIB group element, the vapor deposition source and the sputter source are isolated from each other, so that the sputtered by the VIB group element evaporated using the vapor deposition source. It is possible to prevent the target surface provided in the source from being contaminated.
[0096]
In the present embodiment, the chamber for performing the step (a) includes three sputter sources, but may include one, two, four or more sputter sources as necessary. .
[0097]
Moreover, in this embodiment, although the apparatus provided with two chambers consisting of the chamber which accommodates a sputtering source and the chamber which accommodates a vapor deposition source was shown, a partition plate was provided in one chamber, and a sputtering source and vapor deposition were shown. It can also be modified to separate the source.
[0098]
(Embodiment 4)
Another apparatus for manufacturing a compound semiconductor thin film that can be used for manufacturing a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element will be described with reference to FIG. FIG. 5 is a schematic top view of the compound semiconductor thin film manufacturing apparatus of the present embodiment.
[0099]
As shown in FIG. 5, the compound semiconductor thin film manufacturing apparatus 40 of this embodiment includes a central chamber 41 and chambers 42 to 47 that are adjacent to each other around the chamber 41 and are isolated from each other. The chamber 42 is a load chamber into which a substrate is put, and the chamber 47 is an unload chamber into which a substrate is taken out. The chambers 43 to 45 have the same configuration as the chamber 1a of the apparatus 30 shown in FIG. 4 except that each of the chambers 43 to 45 includes one sputter source (not shown), and the chamber 46 is shown in FIG. It is assumed that the apparatus 30 has the same configuration as that of the chamber 1b. Therefore, in this embodiment, since the sputtering source and the vapor deposition source are individually arranged in separate chambers, Se evaporated from the vapor deposition source and attached to the target provided in the sputtering source adheres to the target. Since no contamination occurs, it is not always necessary to provide a sputtering source shutter for each sputtering source.
[0100]
In such an apparatus 40, the compound semiconductor thin film of the present invention is modified by modifying each layer of the precursor thin film composed of the first to third layers detailed in Embodiment 2 in a separate chamber. A manufacturing method can be implemented. Specifically, first, the substrate placed in the chamber 42 is transferred to the chamber 43 via the chamber 41 to form the first layer, and then transferred to the chamber 44 via the chamber 41 to form the second layer. And then transferred to chamber 45 via chamber 41 to form a third layer to form a precursor thin film and then transferred to chamber 44 via chamber 41 to perform step (b) A compound semiconductor thin film is formed, and finally, the substrate on which the compound semiconductor thin film is formed is transferred to the chamber 47 via the chamber 41 and taken out therefrom. Thus, even if the apparatus of this embodiment is used, the method for producing a compound semiconductor thin film of the present invention can be carried out while moving the substrate through the central chamber.
[0101]
According to the apparatus of this embodiment, in addition to the effects obtained by the apparatus of Embodiment 3, since the sputter sources are isolated from each other, the target surface provided in the sputter source by particles emitted from other sputter sources can be obtained. It is possible to prevent contamination.
[0102]
Furthermore, according to the apparatus of the present embodiment, since a plurality of substrates can be processed simultaneously in different chambers, the film formation tact time can be shortened (or the number of processed sheets per unit time can be increased). Can do.
[0103]
(Embodiment 5)
Another compound semiconductor thin film manufacturing apparatus that can be used for manufacturing a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element will be described with reference to FIG. FIG. 6 is a schematic top view of the compound semiconductor thin film manufacturing apparatus of the present embodiment.
[0104]
As shown in FIG. 6, the compound semiconductor thin film manufacturing apparatus 50 according to the present embodiment includes a chamber 51 and internal chambers 53 to 58 disposed adjacent to each other through a partition plate 52 inside the chamber 51. . The internal chamber 53 is a load chamber into which a substrate is placed, and the internal chamber 58 is an unload chamber from which a substrate is taken out. The chambers 54 to 56 have the same configuration as the chambers 43 to 45 of the apparatus 40 shown in FIG. 5, and the chamber 57 has the same configuration as the chamber 46 of the apparatus 40 shown in FIG. . Here, in the present embodiment, since the sputtering source and the vapor deposition source are individually partitioned and arranged, as in the fourth embodiment, it is not always necessary to provide a sputtering source shutter for each sputtering source.
[0105]
In such an apparatus 50, the compound semiconductor thin film of the present invention is modified by modifying each layer of the precursor thin film consisting of the first to third layers described in detail in Embodiment 2 in a separate chamber. A manufacturing method can be implemented. Specifically, first, the substrate placed in the internal chamber 53 is transferred to the chamber 54 to form the first layer, then transferred to the internal chamber 55 to form the second layer, and then transferred to the internal chamber 56 and the first layer. Three layers are formed to form a precursor thin film, and then transferred to the internal chamber 57 to perform step (b) to form a desired compound semiconductor thin film. Finally, the substrate on which the compound semiconductor thin film is formed It moves to the chamber 58 and is taken out from here. Thus, even if the apparatus of this embodiment is used, the manufacturing method of the compound semiconductor thin film of this invention can be implemented, revolving and moving a board | substrate.
[0106]
According to the apparatus of the present embodiment, the film forming tact can be shortened as in the effect obtained by the apparatus of the fourth embodiment.
[0107]
In the fourth embodiment and the fifth embodiment described above, three chambers each having one sputter source are shown. However, the number of chambers and the number of sputter sources provided in each chamber are selected as necessary. It is also possible.
[0108]
【Example】
Using the apparatus of the first embodiment described above, a manufacturing method similar to that of the first embodiment is performed except that a Cu—Ga target is not used, and CuInSe is used as a compound semiconductor thin film.₂A film was formed. That is, in this example, only the In target that is a group IIIB element target and the Cu target that is a group IB element target are installed and used as the sputtering source.
[0109]
In this example, a substrate made of a soda-lime glass substrate body having a thickness of about 0.55 mm and a Mo conductive film having a thickness of about 0.8 μm formed on the upper surface thereof was used.
[0110]
First, in the step (a) of the first embodiment, an In—Se layer was formed on the above substrate by simultaneously supplying In by sputtering as the first step and simultaneously supplying Se by a vapor deposition method. Next, as a second step, Cu was supplied by sputtering and at the same time, Se was supplied by a vapor deposition method to form a Cu—Se layer. Thereby, a precursor thin film in which an In—Se layer and a Cu—Se layer were sequentially laminated on the substrate was obtained. The step (a) including the first step and the second step was performed while maintaining the substrate temperature (more specifically, the Mo conductive film temperature) at about 200 to 350 ° C. (see FIG. 7).
[0111]
Next, in step (b) of Embodiment 1, as shown in FIG. 7, while supplying Se onto the precursor thin film by vapor deposition, the substrate is first heated to bring the substrate temperature to about 1 second to 5 minutes. The temperature was raised to about 400 to 500 ° C. for heat treatment, and then the heating was stopped and the substrate was allowed to cool. The supply of Se was continued until the substrate temperature reached the temperature in the previous step (a), that is, about 200 to 350 ° C., and then the supply was stopped. Thereby, a Cu—In—Se compound semiconductor thin film was formed on the substrate.
[0112]
The obtained compound semiconductor thin film was found to have a composition ratio of Cu 22.7 atomic%, In 26.25 atomic%, and Se 51.4 atomic% by energy dispersive X-ray measurement. This analysis value is CuInSe₂Slightly excessive In and Se composition ratio (specifically Cu: In is about 0.8 to 1.0) relative to the stoichiometric ratio of the film, and used as a light absorption layer of a solar cell It was approximately equal to a suitable target composition ratio.
[0113]
Using this compound semiconductor thin film as a light absorbing layer, a CdS layer (buffer layer), a ZnO layer, and an ITO film (all of which are transparent conductive films) were sequentially formed on the compound semiconductor thin film by conventional methods known in the art. A thin film solar cell was fabricated by stacking and extracting leads from the Mo conductive film and ITO film of the substrate. This thin-film solar cell has a conversion efficiency of 9.06% and a current density of 36.16 mA / cm.²The open circuit voltage is 0.40 V, the curvature factor is 0.62, and the characteristics are high compared to the characteristics of a thin film solar cell including a compound semiconductor thin film made of Cu, In, and Se obtained according to a conventional manufacturing method. It was.
[0114]
【The invention's effect】
According to the present invention, there is provided a method of manufacturing a compound semiconductor thin film containing a group IB element, a group IIIB element, and a group VIB element, wherein the film thickness is uniform over a large area, the compositional deviation is reduced, and crystal defects are reduced. An inexpensive and safe manufacturing method with reduced generation is provided. Furthermore, according to this invention, the apparatus used suitably for implementing such a manufacturing method is provided. In accordance with the method of the present invention, the compound semiconductor thin film obtained using the apparatus of the present invention has a good film quality and can be used as a light absorbing layer of a large area and high efficiency thin film solar cell.
[Brief description of the drawings]
FIG. 1 (a) is a schematic view of a compound semiconductor thin film manufacturing apparatus according to one embodiment of the present invention, and FIG. 1 (b) is an XX ′ view of the apparatus of FIG. 1 (a). It is the top view cut along the line.
FIGS. 2 (a) and 2 (b) are schematic process diagrams illustrating a method of manufacturing a compound semiconductor thin film according to one embodiment of the present invention, which is performed using the apparatus of FIG. The schematic sectional drawing of the board | substrate with which the precursor thin film and the compound semiconductor thin film were each formed is shown.
FIGS. 3A and 3B are schematic process diagrams for explaining a method of manufacturing a compound semiconductor thin film according to another embodiment of the present invention, and FIGS. 3A and 3B show a precursor thin film and a compound semiconductor thin film formed. A schematic sectional view of a substrate is shown respectively.
FIG. 4 is a schematic view of an apparatus for producing a compound semiconductor thin film according to another embodiment of the present invention.
FIG. 5 is a schematic view of an apparatus for producing a compound semiconductor thin film according to another embodiment of the present invention.
FIG. 6 is a schematic view of an apparatus for producing a compound semiconductor thin film according to another embodiment of the present invention.
FIG. 7 is a graph showing a substrate temperature profile in one embodiment of the present invention.
[Explanation of symbols]
1 chamber
2 Deposition source
3a, 3b, 3c Sputter source
3A, 3B, 3C Sputter source shutter
4 Soaking plate
5 Substrate
6 Heater
7 Susceptor
8 Drive shaft
9 Shutter
10 Exhaust line
11 Ar gas supply line
20 Compound semiconductor thin film manufacturing equipment

Claims (5)

A method for producing a compound semiconductor thin film containing a group IB element, a group IIIB element and a group VIB element,
(A) the raw material elements using at least a sputtering method comprising the steps of supplying the substrate,
(I) supplying the III B group element and VI B group element, to form a first layer of III B group element and VI B group element,
(Ii) supplying a group IB element and III B group element, to form a second layer of group IB and III B group element, and
And (iii) supplying a group IB element and VI B group element, to form a third layer consisting of Group IB elements and VI B group element
Forming a precursor thin film comprising the first layer, the second layer, and the third layer on the substrate in this order ,
(B) While supplying the VIB group element onto the precursor thin film using a method other than sputtering, the substrate on which the precursor thin film is formed is heat-treated at a temperature higher than the temperature in step (a), Forming a compound semiconductor thin film containing a group IB element, a group IIIB element and a group VIB element on a substrate from a precursor thin film. The method according to claim 1, wherein the temperature of the substrate in the step (a) is in the range of 20 to 450 ° C. The method according to claim 1 or 2, wherein the temperature of the substrate in the step (b) is in the range of 300 to 600 ° C and higher than the temperature of the substrate in the step (a). The group IB element is one or both of Ag and Cu; III The group B element is either one or both of In and Ga; VI The method according to any one of claims 1 to 3, wherein the group B element is one or both of Se and S. The IB group element is Cu; III The group B element is In, or In and Ga, VI The method according to claim 4, wherein the group B element is Se.

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