Patent Application
20130295751
The present invention relates to a thin film forming device and a thin film forming method for forming a thin film for use in a photoelectric conversion element such as, for example, a solar cell.
In general, a photoelectric conversion element such as, for example, a solar cell uses an energy conversion characteristic of a semiconductor material. In particular, a solar cell receives attention as a means for obtaining electric energy without adversely affecting the global environment. A photoelectric conversion element of this type is configured by laminating various films for photoelectric conversion, for example, p-type semiconductor films or n-type semiconductor films over a plurality of layers on a surface of, for example, a silicon substrate using a vacuum film forming device such as, for example, a chemical vapor deposition (“CVD”) device.
When a vacuum film forming device is used, the quality of an obtained film is relatively good. However, devices or installations for manufacturing cost much. For this reason, in order to drastically cut device costs or installation costs, there has been newly proposed a film manufacturing method for obtaining a desired thin film by causing particles of a thin film material such as, for example, a metal oxide such as titanium oxide to be adhered to a surface of, for example, a film or a glass substrate through, for example, spraying or application of a solution formed by solving the particles in a solvent such as water or alcohols, and drying the solution by heat (see, e.g., Japanese Patent Laid-open Publication No. 2002-324591 and International Publication No. WO 2004/033756).
However, there is a problem in that a semiconductor thin film formed through the film forming method using a simple spray coating or an application as described above is not so good in liquid crystallinity and thus, not good in a film property.
The present invention is to provide a thin film forming device and a thin film forming capable of forming a thin film for a photoelectric conversion element which is excellent in crystallinity even in an atmosphere at atmospheric pressure.
The present invention provides a thin film forming method of forming a thin film containing a plurality of elements for use in a solar cell on a surface of an object to be processed (“processed object”). The thin film forming method includes dispersing a raw material solution containing the elements in a processing space as microparticles by an electric field, and causing the dispersed microparticles to be adhered to the surface of the processed object to form the thin film.
Also, the present invention provides a thin film forming device for forming a thin film containing a plurality of elements for use in a solar cell on a surface of a processed object. The thin film forming device includes: a raw material solution supply unit configured to supply a raw material solution containing the elements to a processing space; a holding unit configured to hold processed object; a heating unit configured to heat the processed object; and an electric field power supply unit configured to apply a voltage between the holding unit and the raw material solution supply unit to disperse the raw material solution as microparticles by the electric field.
Further, the present invention provides a thin film forming device for forming a thin film containing a plurality of elements for use in a solar cell on surface of a processed object. The thin film device includes: a raw material solution supply unit configured to supply a raw material solution containing the elements to a processing space; a holding unit configured to hold processed object; a heating unit configured to heat the processed object; a draw-out electrode installed in the vicinity of the raw material solution supply unit; and a draw-out power supply unit configured to apply a voltage between the holding unit and the raw material solution supply unit to disperse the raw material solution as microparticles by the electric field.
According to the present invention, a raw material solution is dispersed by an electric field as microparticles to be adhered to a surface of a processed project to form a film. Therefore, a crystalline thin film which has an excellent characteristic of film quality may be formed.
Hereinafter, exemplary embodiments of a thin film forming device and a thin film forming method for forming a thin film for use in a solar cell according to the present invention will be described in detail with reference to accompanying drawings.
As illustrated in
A holding unit 8 configured to hold a substrate 6 which is a processed object is provided on a bottom within the processing container 4. The substrate 6 is made of, for example, a glass plate or a resin plate. Here, a mounting table 10 is provided as the holding unit 8. The mounting table 10 is formed in a shape corresponding to the substrate 6. When the substrate 6 has a circular shape, the mounting table 10 is formed in the circular shape, and when the substrate 6 is has a rectangular shape, the mounting plate 10 is formed in the rectangular shape. In addition, the shape of the substrate 6 is optional.
The mounting table 10 is made of an electrically conductive metal such as, for example, aluminum or aluminum alloy and installed on the bottom of the container through an insulation member 12. A heating unit 15 configured to heat the substrate 6 is provided in the mounting table 10. As for the heating unit 15, a resistance heating heater such as, for example, a ceramic heater or a carbon wire heater is embedded in the mounting table 10 in an insulated state substantially over the entire mounting table 10.
The mounting table 10 is provided with lifter pins 14 configured to move up or down the substrate 6 at the time of carrying-in or carrying-out the substrate 6. Specifically, a pin insertion through-hole 16 extends in the vertical direction through the mounting table 10, the insulation member 12 and the bottom of the container, and the lifter pin 14 is inserted into the pin insertion through-hole 16 to be movable in the vertical direction. In addition, the lifter pin 14 is configured such that, when the lifter pin 14 is lifted by an actuator (not illustrated), the lifter pin 14 may be extended upward from the mounting table 10 or retracted to the mounting table 10 to raise or lower the substrate 6. Depending on the size of the substrate 6, a plurality of lifter pins 14 may be provided. Also, when the film forming processing is performed in a reduced pressure atmosphere, a retractable bellows (not illustrated) made of a metal may be installed at a portion of the bottom of the container penetrated by the lifter pin 14 to maintain the gas tightness of the inside of the processing container 4.
The heating unit 15 is configured to be connected to a heater power supply 20 through a power supply line 18 so that heating power may be supplied to the heating unit 15. In order to measure the temperature of the substrate 6, a temperature measuring unit 22 is provided. Specifically, the temperature measuring unit 22 may be constituted by a thermocouple 24 installed adjacent to the heating unit 15 in the mounting table 10 and the substrate 6 and configured to measure the temperature of the substrate 6. In addition, the temperature measuring unit 22 is connected to a temperature control unit 26 constituted with, for example, a computer, and the temperature control unit 26 is configured to adjust the output of the heater power supply 20 based on the measurement value by the thermocouple 24 so as to control the temperature of the substrate 6.
An exhaust port 28 is formed through the bottom of the processing container 4 and an exhaust system 30 is connected to the exhaust port 28 to exhaust the atmosphere within the processing container 4. Specifically, the exhaust system 30 includes an exhaust passage 32 connected to the exhaust port 28 and an exhaust pump 34 is installed in the middle of the exhaust passage to facilitate the exhaust. When the film forming processing is performed in an atmosphere at atmospheric pressure, the exhaust passage 32 may be directly connected to an exhaust duct that conducts the exhaust inside a factory without providing the exhaust pump 34. Further, when the film forming processing is performed in a reduced pressure atmosphere, a vacuum pump 34 may be used as the exhaust pump 34 and a pressure regulating valve (not illustrated) may be installed in the exhaust passage 32 upstream of the vacuum pump so as to enable the regulation of pressure within the processing container 4.
A substrate carrying-in/carrying-out hole 36 is formed on a side wall of the processing container 4 and an opening/closing door 38 is provided at the carrying-in/carrying-out hole 36. Also, when the film forming processing is performed in the reduced pressure atmosphere, a gate valve which is opened/closed in a gastight manner may be preferably used as the opening/closing door 38.
The processing container 4 is provided with a purging gas intake unit 40 configured to discharge a purging gas into the processing container 4. The purging gas intake unit 40 includes a gas nozzle 42 installed in a side wall of the processing container 4, and a gas passage 44 is connected to the gas nozzle 42. Further, a flow rate controller 46 such as a mass flow rate controller and an open/close valve 48 are sequentially installed in the gas passage 44 so as to supply a purging gas, for example, an N2 gas in a controlled manner as desired. Besides N2, a noble gas such as, for example, He or Ar may be used as the purging gas.
In addition, in a processing space 53 above the substrate 6 within the processing container 4, the processing container 4 is provided with a raw material solution supply unit 50 configured to supply a raw material solution that contains a plurality of elements which form a material of the thin film to be formed, and an electric field power supply unit 52 configured to apply voltage between the raw material solution supply unit 50 and the mounting table 10 which is the holding unit 8 to form an electric field in the processing space 53.
Specifically, the raw material solution supply unit 50 includes a header unit 54 configured to store the raw material solution temporarily. The header unit 54 is formed in a shape of a cylindrical body from an electrically conductive metallic material such as, for example, aluminum or aluminum alloy and attached to the ceiling portion of the container through an insulation member 60. Alternatively, the header unit 54 may be a dual structure cylinder of which the outer wall is formed from a metallic material and the inner wall is formed from, for example, a highly chemical-resistant glass or plastic. As illustrated in
Although the inner diameter H of the nozzle 56 may vary depending on the material, viscosity or density of the raw material solution or the installation direction of the nozzle 56, the inner diameter has a size in which the raw material solution does not drip as droplets, for example, in the range of about 0.1 mm to about 0.35 mm, preferably in the range of about 0.22 mm to about 0.26 mm. The nozzle 56 is also formed of an electrically conductive metallic material such as, for example, aluminum or aluminum alloy. Alternatively, the header unit 54 or the nozzle 56 may also be formed of a highly anti-corrosive and electrically conductive material, for example, PEEK (trademark).
A raw material passage 66 extending from a raw material storage tank 64 configured to store the raw material solution 62 is connected to the header unit 54 so that the raw material solution 62 may be pumped to the header unit 54 at a predetermined pressure by a compressed gas introduced into the raw material storage tank 64. In the middle of the raw material passage 66, a flow rate controller 68 such as a mass flow rate controller and an open/close valve 70 are sequentially provided so that the raw material solution 62 may be supplied to the header unit 54 while being controlled in flow rate as desired. Here, as for the raw material solution 62, a raw material solution that contains, for example, Cu, In and S as the elements is used and is adapted to form a CuInS2 film as the semiconductor thin film.
The electric field power supply unit 52 is constituted with an electric field power supply 72 which is configured to be voltage-controllable. The electric field power supply 72 is configured to apply a voltage between the header unit 54 and the mounting table 10 located below the header unit 54 through a wiring 73 so as to form an electric filed in the processing space 53. The electric field power supply 72 may be configured to apply, for example, a direct current (DC) voltage or a pulse voltage. Also, the electric field power supply 72 may be configured to apply an alternating current (AC) voltage as long as the AC voltage has a frequency that enables the dispersion of the raw material solution 62. The electric field power supply unit 52 has a function of drawing-out the raw material solution 62 in the form of mist from the nozzle 56 to disperse the raw material solution 62 as microparticles and a function of accelerating the dispersed microparticles to the mounting table 10 side.
Here, the distance between the nozzle 56 and the substrate 6 may vary depending on the size of the substrate 6 without being especially limited. For example, when the diameter of the substrate 6 is about 10 cm, the distance may be in the range of about 10 cm to about 20 cm. Also, the output of the electric field power supply 72 is, for example, in the range of about 10 kV to about 30 kV.
The overall operation of the thin film forming device 2 is adapted to be controlled by a device control unit 80 constituted by, for example, a computer, and the program of the computer for executing the operation is stored in a storage medium 82. The storage medium 82 may be constituted by, for example, a flexible disc, a CD (Compact Disc), a hard disc, a flash memory, or a DVD. Specifically, for example, a control of process pressure (when film forming in a pressure-reduced atmosphere), a control of supply pressure and supply flow rate of the raw material solution 62, and a control of output voltage of the power supply for electric field 72 are conducted by an instruction from the device control unit 80. Here, the mounting table 10 and the header unit 54 are fixedly installed. However, they may be moved relatively or, for example, the mounting table 10 may be provided with a rotation mechanism (not illustrated) so that the rotation mechanism may the mounting table 10.
Next, descriptions will be made on a thin film forming method of the present invention which may be performed using the thin film forming device of the present invention configured as described above. First, the opening/closing door 38 installed on a side wall of the processing container 4 is opened, and a non-processed substrate 6 held on a transportation arm (not illustrated) is carried into the processing container 4 through the carrying-in/carrying-out hole 36. In addition, the lift pins 14 provided in the mounting table 10 which is a holding unit 8 are moved up and down so that the lift pins 14 are extended from or retracted to the top surface of the mounting table 10. Thus, the lifter pins 14 receive and place the substrate 6 on the mounting table 10.
Next, power is supplied from a heater power supply 20 to the heating unit 15 installed in the mounting table 10 to heat the entire mounting table 10, thereby heating the substrate 6 placed on the mounting table 10 to a predetermined process temperature and maintaining the substrate 6 at the temperature. Further, while causing N2 gas as purging gas to flow within the processing container 4 from the introduction unit 40, the exhaust pump 34 of the exhaust system 30 is also driven to exhaust the atmosphere within the processing container 4 such as gas generated at the time of film forming. Here, since the film forming processing is performed, for example, in an atmosphere at atmospheric pressure, the exhaust pump 34 does not need to exhaust the atmosphere so strongly.
Also, the raw material solution supply unit 50 is driven to pump the raw material solution 62 from the raw material storage tank 64 and supply the raw material solution 62 to the header unit 54 while controlling the flow rate thereof. At the same time, the electric field power supply 72 of the electric field power supply unit 52 is operated to apply, for example, a direct current voltage between the header unit 54 and the nozzle 56 and the mounting table 10, thereby generating an electric field in the processing space 53. Thus, the raw material flowing out a little bit from the solution outlet 58 at the lower end of the nozzle 56 of the header unit 54 is drawn into the electric field to become microparticles which are dispersed in the form of mist. The microparticles are electrically charged and accelerated toward the mounting table 10 which is the opposite side electrode, and fall down in a spry form on the surface of the mounting table 10, i.e., on the surface of the substrate 6.
As a result, the microparticles of the raw material solution 62 are adhered to the surface of the substrate in the form of a film and the atoms of the raw material are moved on the surface of the substrate 6 by being heated, thereby forming a crystal semiconductor thin film. Such a film forming method is referred to as an electrostatic spray method.
<Formation of CuInS2 Thin Film>
The raw material solution used herein may be formed by solving, for example, chlorides of elements that constitute the thin film in a solvent. Specifically, when forming a semiconductor thin film formed by CuInS2 as the thin film, for example, CuCl2 which is a chloride of the element Cu (cupper), InCl3 which is a chloride of the element In (indium), and thiourea (SC(NH2)2) which is a compound of the element S (sulfur) are mixed and solved in a solvent, thereby forming the raw material solution 62. Here, for example, ethanol of alcohols may be used as the solvent.
The process pressure is set to substantially the atmospheric pressure here but is not limited to this. As described above, film forming may be performed in a reduced pressure atmosphere (vacuum atmosphere). The temperature of the substrate 6 is in the range of 250° C. to 305° C. When the temperature is lower than 250° C., energy is insufficient to crystallize the thin film and when the temperature is higher than 305° C., the sulfur (S) in the thin film is vaporized. Thus, the crystal film may not be formed.
In addition, the atomic ratio of “Cu” and “In” in the raw material solution 62, Cu/In, is set to a value in the range of 0.85 to 1.40. When the atomic ratio is smaller than 0.85 or larger than 1.40, a crystal thin film with a target energy gap may not be fabricated. By changing the atomic ratio, Cu/In, it is possible to control the conductivity type of the formed semiconductor thin film. As described in detail below, for example, when the atomic ratio, Cu/In, is not more than 1, the thin film becomes an n-type semiconductor and when the atomic ratio is more than 1, the thin film becomes a p-type semiconductor. Lack of sulfur may inhibit the formation of a crystalline thin film. However, even if the sulfur is added excessively, no particular problem will be caused because the sulfur is vaporized during the film forming. Accordingly, it is preferable to add sulfur in an atomic ratio of, for example, 1.5 to 5 times of Cu or In.
The strength of the electric field formed in the processing space 53 is set to preferably 100 kV/m or more. When the electric field is lower than this value, the raw material solution 62 may not be sufficiently dispersed in the form of mist. Thus, a thin film may not be formed. Since the film forming is conducted by dispersing the raw material solution as microparticles by the electric field so that the microparticles may be adhered to a surface of an object, a crystalline thin film with an excellent quality may be formed. In particular, when the film forming processing is conducted at the atmospheric pressure, it is not required to configure the thin film forming device itself in a vacuum-resistant specification, thereby substantially reducing the device costs and the installation costs.
<Evaluation of CuInS2 Thin Film>
A CuInS2 thin film was formed using a raw material solution in a mixed state in which “Cu”, “In” and “S” are contained therein as described above, and practically using the apparatus as illustrated in
First, CuInS2 thin films were fabricated while changing the substrate temperature at the time of film forming from 230° C. to 325° C. The atomic ratio, Cu/In, in the raw material solution at this time was “1.2” and the atomic ratio of sulfur, S/(Cu+In), was set to “2.0”. The thin films formed at this time were analyzed using an X-ray diffraction device and the results are represented in
As illustrated in
Next, energy gaps of thin films as being formed were measured while variously changing the atomic ratio, Cu/In, in the raw material solution 62. Here, the atomic ratio, Cu/In, was changed from 0.8 to 1.5. At that time, the substrate temperature Ts was 270° C. and the atomic ratio of sulfur, S/(Cu+In), was set to “2.0”. The results are represented in
As illustrated in
Next, measurements were made on the resistivity and conductivity type of semiconductor of thin films formed while variously changing the atomic ratio, Cu/In in the raw material solution. The atomic ratio, Cu/In, was changed from 0.8 to 1.2. At that time, the substrate temperature Ts was 270° C., and the atomic ratio of sulfur, S/In, was set to “10”. The results are represented in
As apparent from
<Evaluation of γ-In2Se3 Thin Film>
Next, semiconductor thin films were fabricated by an In2Se3 film instead of the above mentioned CuInS2 film and practically using the apparatus as illustrated
Here, a raw material solution was prepared by using InCl3 which is a chloride of In and N—N dimethyl selenourea (C3H8N2Se) which is a compound of Se as raw materials and solving them in ethanol. First, InSe containing films were fabricated while changing the substrate temperature at the time of film forming from 200° C. to 300° C. The atomic ratio, Se/In, in the raw material solution was set to “2.0”. The thin films as being formed were analyzed using an X-ray diffraction device and the results are represented in
As apparent from the graph illustrated in
In comparison, it may be seen that when the substrate temperature is in the range of 235° C. to 280° C., a target γ-In2Se3 film (0006) is sufficiently crystallized and formed on all the substrates and thus exhibits an excellent characteristic result. Also, the conductivity type of the γ-In2Se3 film was n-type. In such a case, it may be seen that the substrate temperature in the range of 250° C. to 265° C. is particularly preferable since the X-ray peak value is high.
Next, characteristics of quality of films were measured for the films fabricated when the substrate temperature at the time of film forming was changed while changing, variously the atomic ratio of In and Se. The results are represented in
With respect to the conductive films of the γ-In2Se3 crystal films formed as described above, an annealing processing was performed after film forming. As a result, it was possible to control the conductivity type of the conductive films. That is, as described above, the conductivity type of the γ-In2Se3 crystal films formed as described above was n-type. When the annealing temperature is lower than 320° C., the n-type was maintained. However, when the annealing temperature was set to 320° C. or higher, it was possible to change the conductivity type from n-type to p-type. Thus, in order to maintain the conductivity type of n-type after the semiconductor films of the γ-In2Se3 crystal films are produced, the annealing processing may not be performed or may be performed at a predetermined temperature, for example, at a temperature lower than 320° C. In order to change the conductivity type to p-type, the annealing may be performed at a predetermined temperature, for example, at a temperature of 320° C. or higher. Consequently, it may be seen that the conductivity type is freely selectable. In other words, it is possible to select the conductivity type of the semiconductor film by performing a temperature-controlled annealing processing.
<Evaluation of In253 Thin Film>
Next, semiconductor thin films made of an In2S3 film were fabricated practically using the apparatus illustrated in
Here, CuCl2 which is a chloride of Cu, InCl3 which is a chloride of In and thiourea which is a compound of S were used as raw materials, and a raw material solution was fabricated by solving these materials in ethanol. Here, the process pressure was set to about atmospheric pressure. First, In2S3 thin films were fabricated while changing the substrate temperature at the time of film forming from 200° C. to 400° C. The atomic ratio, S/In, in the raw material solution at this time was set to “2.0”. The thin films formed at this time were analyzed using an X-ray diffraction device and the results are represented in
As illustrated in
In comparison, when the substrate temperature is in the range of 275° C. to 350° C., all the thin films show a high X-ray peak at the crystal plane (0012). Thus, it may be seen that preferable semiconductor crystal films are formed. In addition, half value widths of X-ray spectrums at the time of X-ray diffraction were obtained and the results are represented in
For the purpose of confirmation, the resistivity and energy gap of the InS containing thin films were measured and the results are represented in
From these results, it was confirmed that when light irradiation is conducted, holes are produced and at the same time, electrons flow. In addition, when the substrate temperature is 400° C., the resistivity was considerably reduced. It is estimated that sulfur was excessively released by heating. In addition, as illustrated in
<Evaluation of Cu2ZnSnS4 Thin Film>
Next, semiconductor thin film made of a Cu2ZnSnS4 film were fabricated practically using the apparatus illustrated in
Here, as described above, a raw material solution was prepared by using CuCl3 which is a chloride of Cu, ZnCl2 which is a chloride of Zn, SnCl2 which is a chloride of Sn, and thiourea which is a compound of S as raw materials and mixing and solving the raw materials in a solvent (ethyl alcohol). The film forming process was conducted in the atmosphere. First, Cu2ZnSnS4 thin films were fabricated while changing the substrate temperature at the time of film forming from 320° C. to 440° C. The atomic ratio in the raw material solution was set to be “Cu:Zn:Sn:S=2:1:1:10.” The results obtained by analyzing the thin films formed at this time using an X-ray diffraction device are represented in
As illustrated in
In comparison, that when the substrate temperature is in the range of 340° C. to 380° C., all the thin films show a high X-ray peak at the crystal plane (112), and in particular, when the substrate temperature is in the range of 360° C. to 370° C., the X-ray peak appears especially strongly. Thus, it may be seen that preferable semiconductor films were formed. In addition, the half value widths of X-ray spectrums at the time of X-ray diffraction were calculated and the results are represented in
For confirmation, the resistivity and energy gap of the CuZnSnS containing thin films were measured and the results are represented in
In addition, when the substrate temperature is 400° C. or 420° C., the resistivity is considerably reduced. It is estimated that sulfur is released by heating and sulfur vacancies act as a donor. Further, as illustrated in
Next, the first modified exemplary embodiment of the raw material solution supply unit will be described. The above described exemplary embodiments use a single raw material solution that contains all the elements to be included in a thin film to be formed but is not limited to this. Plural kinds of raw material solutions may be used in each of which each elements to be included in the thin film to be formed is separately solved. Also, some, but not all, of elements to be included in the thin film to be formed may be contained in a single raw material solution. In such a case, the raw material solution supply unit is configured to be provided with a plurality of header units of which the number corresponds to the number of the kinds of the raw material solutions.
As illustrated in
In such a case, for example, a raw material solution formed by solving CuCl2 in a solvent (ethanol) is caused to flow in the raw material passage 66A, a raw material solution formed by solving InCl3 in a solvent (ethanol) is caused to flow in the raw material passage 66B, and a raw material solution formed by solving thiourea in a solvent (ethanol) is caused to flow in the raw material solution 66C. Here, the control of each atomic ratio may be achieved by controlling the supply amount of each raw material solution separately. The present modified exemplary embodiment may exhibit the same acting effects with those of the above described exemplary embodiments.
Next, the second modified exemplary embodiment of the raw material solution supply unit will be described. In the film forming method of CuInS2 films as described above, only a single material solution in which the atomic ratio, Cu/In, is specifically defined, is used in the thin film forming device and thus, thin films of only one conductivity type of p-type or n-type may be formed in one film forming process (See, e.g.,
As illustrated in
In the present modified exemplary embodiment, for example, a raw material solution (containing S) in which the atomic ratio, Cu/In, is adjusted so that an n-type semiconductor thin film may be formed is caused to flow in the raw material passage 66A, a raw material solution (containing S) in which the atomic ratio, Cu/In, is adjusted so that a p-type semiconductor thin film may be formed is caused to flow in the raw material passage 66B, and both the raw material solutions are selectively supplied to the processing space. As a result, an n-type CuInS2 thin film and a p-type CuInS2 thin film may be formed selectively and successively. The present modified exemplary embodiment may also exhibit the same acting effects with those of the above described exemplary embodiments.
Next, the third modified exemplary embodiment of the raw material solution supply unit will be described. In the raw material solution supply units 30 described above, each header unit 54 is provided with one nozzle but is not limited thereto. One header unit 54 may be provided with a plurality of nozzles.
As illustrated in
The header unit 54 is formed in a hollow disc shape in the third modified exemplary embodiment described above but not limited thereto and may be configured as in the fourth exemplary embodiment as illustrated in
As illustrated in
Such a header unit 54 is effective when the substrate 6 is formed in a rectangular shape which is long in the transverse direction. For example, when the header unit and the substrate are adapted to be relatively moved and the header unit 54 is moved by a scanner mechanism (not illustrated) in a direction indicated by arrow 84 (in the longitudinal direction of the substrate) which is orthogonal to the longitudinal direction of the header unit, a film forming processing may be efficiently performed.
In the fourth modified exemplary embodiment, a plurality of nozzles 56 of a circular cross-section are formed on the bottom portion of the header unit 54 but are not limited to this. A nozzle may be configured as in the fifth modified exemplary embodiment as illustrated in
As illustrated in
Such a header unit 54 is effective when the substrate 6 is formed in a rectangular shape which is long in the transverse direction as in the fourth modified exemplary embodiment. For example, when the header unit and the substrate are adapted to be relatively moved and the header unit 54 is moved by a scanner mechanism (not illustrated) in a direction indicated by arrow 84 (in the longitudinal direction of the substrate) which is orthogonal to the longitudinal direction of the header unit, a film fanning processing may be efficiently performed.
Next, the second exemplary embodiment of the thin film fanning device according to the present invention will be described.
In the thin film forming device described above with reference, for example,
As illustrated in
Here, the electrode body 118 includes a lateral side portion 118A formed in a cylindrical shape to enclose the nozzle 56 and a part of the lateral side of the header unit 54, and a bottom side portion 118B connected to the lower end of the side surface portion 18A and formed with the microparticle passage hole 116 at the central portion thereof. Thus, the solution outlet 58 of the nozzle 56 is configured to face the processing space 53 through the microparticle passage hole 116 positioned just below the solution outlet 58. An insulation member 60 is interposed between the header unit 54 and the upper portion of the cylindrical lateral side portion 118A of the electrode body in such a manner that the insulation member 60, the header unit 54 and the cylindrical lateral side portion 118a of the electrode body are integrally attached to each other, and the header unit 54 and the draw-out electrode 112 form a single solution injection unit 120.
In addition, the lateral side portion 118A of the electrode body is attached and fixed to the ceiling portion of a processing container 4 through an insulation member 122. Here, the diameter H2 of the microparticle passage hole 116 is set to, for example, about 0.5 mm and the distance H3 between microparticle passage hole 116 and the solution outlet 58 is set to, for example, about 0.5 mm. Further, the height of the electrode body 118 is about 32 mm and the diameter is about 30 mm but these sizes are not particularly limited. The material of the draw-out electrode 112 is a conductive material and, for example, a metal such as aluminum or aluminum alloy may be used for the material. However, a highly corrosion-resistant resin as described above, for example, PEEK (trade mark) may be used.
The draw-out power supply unit 114 includes a draw-out power supply 124 and is configured to apply draw-out voltage between the header unit 54 and the draw-out electrode 112 through a wiring 126. Thus, large electric field is generated between the front end of the nozzle 56 of the header unit 54 and the bottom side portion 118B of the electrode body so that the raw material solution 62 is drawn out and dispersed from the solution outlet 58 through the microparticle passage hole 116. The draw-out power supply 124 is configured to be voltage-controllable and to be capable of outputting a voltage of up to 10 kV. The draw-out power supply 124 may be a type that applies, for example, a direct current voltage or a plus voltage and may a type that applies a alternating current voltage as long as it has a frequency that enables the dispersion of the raw material solution 62.
Also, a constant current circuit 128 is provided in the middle of the wiring 126 that connects the draw-out power supply 124 and the header unit 54 to keep the current flowing in the header unit 54 constant so that the dispersion amount of the raw material solution 62 from the nozzle 56 may be kept constant. In addition, the constant current circuit 128 is configured to be capable of control a current value in response to an instruction from the device control unit 80 so as to control the dispersion amount. Further, the constant current circuit 128 may be omitted.
Further, an acceleration power supply unit 130 configured to accelerate the microparticles of the raw material solution is connected between the draw-out electrode 112 and the holding unit 8. Specifically, the acceleration power supply unit 130 includes an acceleration power supply 132 and connected between the draw-out electrode 112 and the holding unit through wirings 126, 134. Thus, an electric field is generated between the draw-out electrode 112 and the holding unit 8 so that the microparticles entering into the processing space 53 through the microparticle passage hole 116 may be accelerated downwardly. The acceleration power supply 132 is configured to be voltage-controllable and to output a voltage of, for example, up to 20 kV. With this acceleration power supply 132, for example, a direct current voltage, a pulse voltage, or an alternating current voltage may be used. When a direct current voltage is used for the draw-out power supply 124 and the acceleration power supply 132, it is natural that they are connected so the polarities of them take the same direction.
In addition, the power unit for acceleration 130 may be omitted as long as it is possible to obtain sufficient velocity of the dispersed microparticles with the power supply for draw-out 24. Further, the distance between the lower end of the draw-out electrode 112 and the top end of the mounting table 10 which is the holding unit 8 is, for example, about 1 cm to 10 cm.
Next, descriptions will be made on the operation of the second exemplary embodiment of the second exemplary embodiment of thin film forming device configured as described above. Also in the second exemplary embodiment, film forming may be performed either under a reduced pressure atmosphere or an atmospheric pressure, and the basic operation of the second exemplary embodiment is the same as that of the first exemplary embodiment except the method of applying the voltage for draw-out.
In the second exemplary embodiment, when the voltage from the draw-out power supply 124 is applied between the header unit 54 and the draw-out electrode 112, a high electric field is generated between the front end of the nozzle 56 of the header unit 54 and the bottom surface portion 118B of the draw-out electrode 112, an electric field concentration occurs at the front end of the nozzle 56 and raw material solution 62 is drown out from the solution outlet 58 at the lower end of the nozzle 56 and dispersed, thereby being brought into the microparticle state. At this time, the voltage applied between the nozzle 56 and the draw-out electrode 112 is, for example, about 1 kV to about 10 kV. The dispersed microparticles pass through the microparticle passage hole 116 fanned at the electrode body bottom surface portion 118b while being dispersed, thereby being diffused into the processing space 53.
In addition, the microparticles passing the processing space 53 are further accelerated and diffused downward, i.e., toward the mounting table 10 side by the electric field generated by the voltage for acceleration applied between the draw-out electrode 112 and the mounting table 10 by the acceleration power supply unit 132 and attached to the surface of the substrate 6 on the mounting table 10, thereby forming a thin film. At this time, the voltage applied between the electrode draw-out 112 and the holding unit 8 is, for example, about 0 kV to 20 kV. Here, in order to control the thin film fanning rate, it may be sufficient if the draw-out voltage applied to the header unit 54 or draw-out current flowing therein is regulated.
Thus, the second exemplary embodiment may exhibit the same acting effects as those of the first exemplary embodiment described above with reference to, for example,
Next, descriptions will be made on modified examples of the raw material solution supply unit and the drawn-out electrode.
In the second exemplary embodiment 2 as described above, only one solution injection unit 120 configured by the header unit 54 and the draw-out electrode 112 is installed on the ceiling portion of the processing container 4. However, without being limited thereto, a plurality of solution injection units may be installed as in the modified embodiment as illustrated in
As illustrated in
Also in such a case, the acting effects which are the same as those of the second exemplary embodiment described with reference to
Here, the electrode body 118 of each of the draw-out electrodes 112 is formed by a cylindrical lateral side portion 118A and a bottom side portion 118B but not limited thereto. For example, it is also possible to provide only the bottom side portion 118B of the electrode body while omitting the cylindrical lateral side portion 118A of the electrode body and to provide one sheet of conductive plate that interconnects four bottom side portions 118B transversely. In other words, it is possible to provide only one sheet of conductive plate and to form a microparticle passage hole 116 below and at a position corresponding to each of the solutions 58.
<Example of Photoelectric Conversion Element>
Next, descriptions will be made on a structure of a photoelectric conversion element using a semiconductor crystal thin film produced through the thin film forming methods as described above.
Also, the photoelectric conversion element illustrated in
Also, the photoelectric conversion element as illustrated in
In each of the above-described exemplary embodiments, the solvent forming a raw material solution is ethanol but is not limited to this. As for the solvent, for example, water, an alcohol containing ethanol or methanol, an organic solvent, an aromatic-based solvent, an alcohol-based solvent, an ether-based solvent, an ester-based solvent may be used.
Also, the thin films formed in each of the above-described exemplary embodiments are a CuInS2 film and an In2Se3 film but are not limited to them. A formed thin film may be that formed of any one selected from a group including, for example, In0.5Ga0.5P, γ-In2Se3, In2S3, CuIn1-XGaXS, GaAs, CdTe, CuInS2, CuIn1-XGaXSe, and Cu2ZnSnS4.
In particular, when an In2S3 film is formed as described above, the substrate temperature is in the range of 275° C. to 350° C., preferably in the range of 300° C. to 350° C. In addition, when a Cu2ZnSnS4 film is formed, the substrate temperature is in the range of 340° C. to 380° C., preferably in the range of 360° C. to 370° C.
Also, in the above-described exemplary embodiments, a header unit 54 of a raw material solution supply unit 50 is disposed at the upper side and a mounting table 10 (holding unit 8) in which a substrate 6 is held is disposed below the heater unit 54. However, since the raw material solution is dispersed by electric field regardless of gravity, the exemplary embodiments are not limited to this positional relationship. For example, the positional relationships described above may be disposed to be inversely opposed to each other in the vertical direction, to be inversely opposed to each other in the horizontal direction corresponding to a transverse direction, or to be opposed to each other to be inclined to a direction inclined to the vertical direction.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-005310 | Jan 2011 | JP | national |
| 2011-278995 | Dec 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/050572 | 1/13/2012 | WO | 00 | 7/10/2013 |
