JP2013012703A - Manufacturing method and manufacturing apparatus of compound semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a compound semiconductor film with less variation in film quality.SOLUTION: In a compound semiconductor film manufacturing method, aggregates in a solution for deposition for depositing a compound semiconductor film by a CBD method is classified by centrifugal separation at least either before deposition or during deposition, and thereby an average particle size of the aggregates in the solution for deposition is controlled at not more than a predetermined value.

Description

  The present invention relates to a method and apparatus for manufacturing a compound semiconductor film.

As a manufacturing apparatus for forming a semiconductor film on a light absorption layer in a CIGS solar cell element, there is a film forming process using a CBD (Chemical Bath Deposition) method, and a predetermined amount of a plurality of solutions are added to a film forming tank. There is a film forming apparatus that forms a compound semiconductor film by adjusting the film forming solution to be supplied and immersing the substrate in the film forming solution.
In this film forming apparatus using the CBD method, the compound semiconductor film can be formed under the same conditions by controlling the conditions such as the concentration, temperature, and stirring speed of the film forming solution in the film forming tank to be constant. Desired.

  In this regard, by forming a film when the transparency of the film forming solution is within a predetermined range, it is possible to improve the film quality by forming a film with a small amount of agglomeration of compound semiconductor fine particles in the film forming solution. It is known (see, for example, Patent Document 1).

JP 2002-343987 A

However, even if the transmittance of the film forming solution is controlled as in the manufacturing method described in Patent Document 1, a change in the film forming solution cannot be sufficiently detected.
Therefore, the film quality of the compound semiconductor film formed during mass production may vary.

  Therefore, an object of the present invention is to produce a compound semiconductor film with little variation in film quality.

  In the method for producing a compound semiconductor film of the present invention, aggregates in a film forming solution for forming a compound semiconductor film by CBD method are classified by centrifugation at least before or during film formation. To control the average particle size of the aggregates in the film-forming solution to a predetermined value or less.

  In addition, the compound semiconductor film manufacturing apparatus of the present invention accommodates a film forming solution used for the CBD method, and between the film forming tank for forming the compound semiconductor film by the CBD method and the film forming tank. And a classification mechanism for centrifuging and classifying the aggregates in the film-forming solution circulated in step (b).

  According to the method and apparatus for producing a compound semiconductor film of the present invention, a compound semiconductor film with little variation in film quality can be produced.

It is a mimetic diagram showing the film deposition system of one embodiment of the present invention. It is a schematic diagram which shows the classification mechanism in the film-forming apparatus of one Embodiment of this invention. It is a graph which shows an example of the correlation between the film-forming rate of a compound semiconductor film, and the average particle diameter of the aggregate of compound semiconductor fine particles. It is a photograph substitute figure of an example of the conventional compound semiconductor film surface. It is a photograph substitute figure of an example of the compound semiconductor film surface of this invention. It is a cross-sectional schematic diagram of an example of a photoelectric conversion element. It is a cross-sectional schematic diagram which shows the epitaxial growth process of the compound semiconductor film in other embodiment of this invention.

  Hereinafter, taking a photoelectric conversion element 1 as an example, an embodiment of a method and an apparatus for producing a compound semiconductor film will be described in detail with reference to the drawings.

  In FIG. 6, the photoelectric conversion element 1 includes a substrate 21, a first electrode layer 22, a light absorption layer 23, a compound semiconductor layer 24, and a second electrode layer 25.

For example, the light absorption layer 23 preferably includes a chalcopyrite material and has a function of generating light by absorbing light. The light absorption layer 23 is not particularly limited. For example, Cu (In, Ga) Se ₂ (also referred to as CIGS), Cu (In, Ga) (Se, S) ₂ (also referred to as CIGSS), and CuInS ₂ (also referred to as CIS). Say). Cu (In, Ga) Se ₂ refers to a compound mainly composed of Cu, In, Ga, and Se. Cu (In, Ga) (Se, S) ₂ refers to a compound mainly composed of Cu, In, Ga, Se, and S. Moreover, for example, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, and the like can be given.

  Such a light absorption layer 23 is formed by forming a raw material element into a film shape by sputtering or vapor deposition, or forming a film shape by applying a raw material solution to form a precursor containing the raw material element. And the light absorption layer 23 which consists of a semiconductor can be formed by heating this precursor. Alternatively, it can also be formed by forming a metal element in the same manner as described above to form a precursor and heating the precursor in a gas atmosphere containing a VI-B group element.

  The compound semiconductor layer 24 refers to a layer that performs a heterojunction with the light absorption layer 23. The compound semiconductor layer 24 is formed on the light absorption layer 23 with a thickness of about 5 nm to 200 nm. The light absorption layer 23 and the compound semiconductor layer 24 are preferably of different conductivity types. For example, when the light absorption layer 23 is a p-type semiconductor, the compound semiconductor layer 24 is an n-type semiconductor. Preferably, from the viewpoint of reducing leakage current, the compound semiconductor layer 24 is a layer having a resistivity of 1 Ω · cm or more. In addition, the compound semiconductor layer 24 preferably has a light-transmitting property with respect to the wavelength region of light absorbed by the light absorption layer 23 in order to increase the absorption efficiency of the light absorption layer 23.

  In FIG. 6, a plurality of photoelectric conversion elements 1 are formed side by side. The photoelectric conversion element 1 includes a third electrode layer 26 provided on the substrate 21 side of the light absorption layer 23 so as to be separated from the first electrode layer 22. The second electrode layer 25 and the third electrode layer 26 are electrically connected. The third electrode layer 26 is integrated with the first electrode layer 22 of the adjacent photoelectric conversion element 1. With this configuration, adjacent photoelectric conversion elements 1 are connected in series.

  The substrate 1 is for supporting the photoelectric conversion element 1. Examples of the material used for the substrate 1 include glass, ceramics, resin, and metal.

  The first electrode layer 22 and the third electrode layer 26 are made of a conductor such as Mo, Al, Ti, or Au, and are formed on the substrate 1 by a sputtering method or a vapor deposition method.

The second electrode layer 25 is a 0.05 to 3.0 μm transparent conductive film such as ITO or ZnO.
The second electrode layer 25 is formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like. The second electrode layer 25 is a layer having a resistivity lower than that of the compound semiconductor layer 24, and is for taking out charges generated in the light absorption layer 23. From the viewpoint of taking out charges well, it is preferable that the resistivity of the second electrode layer 25 is less than 1 Ω · cm and the sheet resistance is 50 Ω / □ or less. In order to increase the absorption efficiency of the light absorption layer 23, the second electrode layer 25 preferably has a light transmittance with respect to the absorption light of the light absorption layer 23. The second electrode layer 25 has a thickness of 0.05 to 0.5 μm from the viewpoint of enhancing the light transmittance and at the same time enhancing the light reflection loss preventing effect and the light scattering effect and further transmitting the current generated by the photoelectric conversion. Thickness is preferred. Further, from the viewpoint of preventing light reflection loss at the interface between the second electrode layer 25 and the compound semiconductor layer 24, the refractive indexes of the second electrode layer 25 and the compound semiconductor layer 24 are preferably equal. Note that a collecting electrode may be formed on the second electrode layer 25.

<Production Method 1 of Compound Semiconductor Film>
Hereinafter, in the description of one embodiment of the present invention, the above-described compound semiconductor layer 24 is taken as an example of a compound semiconductor film.

  For example, a wet CBD method is used to form an InS-based compound semiconductor film using an aqueous solution of indium chloride and thioacedamide (in addition, ammonia water or hydrochloric acid may be used in combination for pH adjustment). doing. For example, as the film-forming solution 7, a solution prepared by mixing two solutions of an indium trichloride tetrahydrate aqueous solution 0.01 mol / liter and a thioacetamide aqueous solution 0.30 mol / liter in a ratio of 1: 1 is used. And formation of the compound semiconductor film by CBD method using this film-forming solution 7 is performed, for example, according to the following processing steps.

  First, as a first stage, the surface of the light absorption layer 24 of the solar cell element 1 is immersed in the film-forming solution 7 at room temperature T1, and the film-forming solution 7 is stirred, for a set time (for example, 5 to 10). For a minute). Stirring of the film-forming solution 7 is continued thereafter until the formation of the compound semiconductor film is completed.

  As a second step, the temperature of the film-forming solution 7 is set to a set temperature T2 (for example, 60 minutes) over a predetermined time (for example, about 10 minutes) while the surface of the light absorption layer 24 is immersed in the film-forming solution 7. To about ℃).

  Next, as a third stage, the surface of the light absorption layer 23 is continuously immersed in the film-forming solution 7 while maintaining the film-forming solution 7 at the set temperature T2, and after a temperature rise for a predetermined time (about 40 minutes). After waiting for the progress, the formation of the compound semiconductor film is terminated.

  In this embodiment, agglomerates in a film-forming solution for forming a compound semiconductor film by the CBD method are classified by centrifugation at least one of before and during the film formation. The average particle size of the aggregates in the solution is controlled to a predetermined value or less.

  The aggregate 5 of the compound semiconductor fine particles having a predetermined size or more in the film-forming solution 7 adsorbs the compound semiconductor fine particles having a particle size smaller than that, so that the particle size distribution of the aggregate 5 in the film-forming solution 7 is reduced. May change significantly.

  Accordingly, the aggregate 5 of the compound semiconductor fine particles is classified by centrifugation and then quickly removed from the film-forming solution 7 to maintain the particle size distribution of the compound semiconductor fine-particle aggregates 5 in the film-forming solution 7. Thus, a compound semiconductor film having a uniform film quality can be obtained.

For example, when two solutions of an indium trichloride tetrahydrate aqueous solution and a thioacetamide aqueous solution are used as the film forming solution 7, the predetermined value is 3 μm, that is, the average particle size of the aggregate 5 of compound semiconductor fine particles is 3 μm. The following is preferable.

  Here, the reason for the difference in the film quality of the compound semiconductor film due to the difference in the particle size distribution of the aggregates 5 of the compound semiconductor fine particles in the film-forming solution 7 can be considered as follows. A graph of the relationship between the average particle size of the aggregates 5 of the compound semiconductor fine particles in the film forming solution and the film formation rate of the compound semiconductor film is shown in FIG. From FIG. 3, when the average particle diameter of the aggregate 5 of compound semiconductor fine particles in the film-forming solution changes, the film formation rate changes greatly, and the large aggregate 5 of compound semiconductor fine particles adheres to the film formation surface. Normal epitaxial growth is hindered and the film quality tends to be different. For example, the surface of the compound semiconductor film formed with the film-forming solution 5 having an average particle diameter of 3 nm or less at the initial stage of film formation is in a good state as shown in FIG. 5, but the film formation is performed for a long time and the average particle diameter is 3 nm. In such a state, the surface state tends to be different as shown in FIG.

  In the present invention, the particle size distribution of the film-forming solution 7 can be maintained over a long period of time, and variations in film quality can be reduced.

<Compound semiconductor film manufacturing apparatus 1>
Hereinafter, an embodiment of a compound semiconductor film manufacturing apparatus (hereinafter also referred to as a film forming apparatus 10) of the present invention will be described with reference to the drawings. For example, in FIG. 1, as a mechanism of the film forming apparatus 10, the solution supply source 12 loaded on the measuring instrument 11 is controlled by the weight of the supply amount of the solution serving as the base of the film forming solution 7 inside. These solutions are supplied from the solution supply source 12 to the diffusion tank 8a through the supply pipe 14a by the pump 13a.

  Here, as the solution supply source 12 loaded on the measuring instrument 11, there are a thioacetamide solution, an indium chloride solution, hydrochloric acid, and the like, which are individually supplied to the diffusion tank 8a. Only one of them is shown.

  In the stirring layer 8a, the valve 17a is opened, and the pump 13b is activated, whereby each solution serving as the base of the film-forming solution 7 circulates through the circulation pipe 16a. As a result, the respective solutions that are the basis of the film-forming solution 7 are stirred to form the film-forming solution 7.

  Then, the valve 17c is opened, and the film forming solution 7 is supplied to the film forming tank 8b through the supply pipe 14b. The old film-forming solution 7 is periodically discharged to the drain 19 through the discharge pipe 15a by opening the valve 17b.

  The film forming apparatus 10 is provided with a supply system mechanism for supplying the film forming solution 7 into the film forming tank 8b so as to be separable from the film forming tank 8b. A discharge system mechanism for discharging from the tank 8b is provided so as to be separable from the film forming tank 8b.

  Furthermore, a circulation system mechanism for circulating the film forming solution 7 in the film forming tank 8b is provided in the film forming tank 8b. In other words, the circulation system mechanism is provided so as to be interlocked with the film forming tank 8b. Note that the valve 17d or the valve 17e is periodically opened, and the old film-forming solution 7 is discharged to the drain 19 through the discharge pipe 15b or 15c.

  Hereinafter, a classification mechanism according to an embodiment of the present invention will be described.

  In one embodiment of the compound semiconductor film manufacturing apparatus of the present invention, a film forming solution for containing a film forming solution used for the CBD method and forming a compound semiconductor film by the CBD method, a film forming tank, And a classification mechanism for centrifuging and classifying aggregates in the film-forming solution circulated between the two.

  More preferably, the classifying mechanism includes a rotating tank for storing the film forming solution supplied from the film forming tank, a rotating means for rotating and flowing the stored film forming solution, and one end disposed in the rotating tank. The light-weight agglomerate separation tube is for extracting agglomerates having a particle size of a predetermined value or less from the rotationally-flowing film-forming solution and returning it to the film-forming tank.

  Various forms of the classification mechanism can be implemented and are not specified. For example, as shown in FIGS. 1 and 2, after the collection pipe 18 c is put into the rotary tank 3 of the classification mechanism 2 after use. The film-forming solution 7 is supplied, and then the rotor 4 rotates to rotate and flow the film-forming solution 7, and the compound semiconductor fine particle aggregates 5 are centrifuged according to the particle diameter. Next, the light agglomerate 5a is collected by a light agglomerate separation pipe 6a having one end on the center side in the rotary tank 3, and then sent to the film formation tank 8b through the film formation pipe 18a for film formation. It can be implemented with a structure of providing.

  In FIG. 2, the light agglomerates 5 a are distributed on the center side and the weight agglomerates 5 b are distributed on the inner wall side. Therefore, the closer the one end of the light agglomerate collection pipe 6 a is to the center of the rotary tank 3, Become more.

On the other hand, the weight aggregate 5b is collected by the weight aggregate separation pipe 6b having one end on the inner wall side in the rotary tank 3, and then sent to another tank through the reuse pipe 18b. If the aggregated weight aggregate 5b is decomposed again by a reduction reaction or the like, it can be reused as the film-forming solution 7 and the increase in material cost can be reduced. For example, when the weight aggregate 5b is In ₂ S ₃ , In ₂ S ₃ can be reacted with HCl and reused as InCl ₃ . The film-forming solution 7 is circulated between the film-forming tank 8b and the classification mechanism 2 via the lightweight aggregate separation pipe 6a by a pump 13c provided in the film-forming tank 8b.

  By controlling the size of the aggregate 5 of compound semiconductor fine particles by the compound semiconductor film manufacturing apparatus and the compound semiconductor film manufacturing method as described above, a high-density compound semiconductor layer can be formed in a short time.

<Compound semiconductor film manufacturing apparatus 2>
Furthermore, as another example of the compound semiconductor film manufacturing apparatus of the present embodiment, the lightweight aggregate separation tube may be movable from the center side to the outer periphery side in the film formation tank.

  That is, in FIG. 2, the position of the mouth of the lightweight aggregate separation tube 6 a is movable in the radial direction of the film formation tank 3.

  When the mouth of the light-weight agglomerate separation tube 6a is on the center side in the film-forming tank 3, a film-forming solution 7 having a small agglomerate 5 of compound semiconductor fine particles is used. .

  On the other hand, when the mouth of the light-weight agglomerate separation tube 6a is on the outer peripheral side in the film-formation tank 3, the film-formation solution 7 having a large agglomerate 5 of compound semiconductor fine particles is used. It can be controlled to be smaller.

By using such a movable lightweight agglomerate separation tube 6a, it is possible to adjust the film formation speed to be optimal for epitaxial growth, so that the film quality variation of the compound semiconductor film can be reduced.

If such a device for manufacturing a compound semiconductor film is used, in addition to the original purpose of reducing the film quality variation of the compound semiconductor film, a manufacturing method for the following modified example is possible.

<Method 2 for producing compound semiconductor film>
According to another example of the manufacturing method of this embodiment, during the formation of the compound semiconductor film, classification is performed by changing the predetermined value of the average particle size of the aggregate in a plurality of stages.

  When forming the upper electrode layer 25 after forming the compound semiconductor layer 24, the compound semiconductor layer 24 may be damaged by the sputtered particles from the upper electrode layer 25 side. In order to shield the sputtered particles and buffer the damage, it is effective that the compound semiconductor layer 24 has a multi-layer structure having different densities, for example, the upper surface of the compound semiconductor layer 24 is made fluffy or porous. It is.

  Therefore, by using the manufacturing method of the present invention, it is possible to easily form such a multilayer structure having different densities and to reduce variations in film quality. That is, after classifying the compound semiconductor aggregate 5 so as to reduce the average particle size and forming the compound semiconductor as a dense layer, the compound semiconductor aggregate 5 is classified so that the average particle size of the compound semiconductor aggregate 5 increases. The semiconductor can be formed as a rough layer.

  Furthermore, according to another example of the production method of the present embodiment, the average particle size of the aggregate is periodically controlled by periodically performing classification by centrifugation.

In terms of reducing the internal stress in the compound semiconductor layer 24, it is effective to relieve the internal stress by using a stacked periodic structure in which the density in the compound semiconductor layer 24 is alternately changed.

Therefore, by using the manufacturing method of the present invention, the average particle size of the aggregates 5 of the compound semiconductor fine particles is periodically controlled to periodically change the film formation rate, for example, to make the compound semiconductor layer 24 dense / rough. It is possible to have a laminated periodic structure of / dense / rough.

  Here, in the film formation process of the compound semiconductor layer 24, it was difficult to re-form a dense film on a rough film in which the orientation of epitaxial growth was disturbed, but this is made possible by the manufacturing method of the present invention. 7 will be described in detail. For example, as shown in FIG. 7A, by increasing the aggregates 5 of the large compound semiconductor fine particles in the CBD film forming solution 7, the aggregates 5 of the compound semiconductor fine particles and the like are formed on the surface of the compound semiconductor film on the orientation plane a. By making it adhere, the orientation is changed to obtain a rough surface in which the orientation surface b is locally formed. Next, by reducing the agglomerates 5 of the large compound semiconductor fine particles in the CBD film forming solution 7, the film forming speed is increased, and the epitaxial growth of the orientation surface b in the concave portion is laterally performed as shown in FIG. 7B. Grow. As shown in FIG. 7C, the compound semiconductor films grown in the lateral direction are connected to each other, and an alignment plane c (here, an alignment plane perpendicular to the alignment plane b) can be formed.

  Thus, after the alignment surface of the compound semiconductor film once roughened is uniformly arranged, new epitaxial growth (alignment surface c) is promoted as shown in FIG. 7D to form a dense film. it can.

  Then, by increasing the aggregates 5 of the large compound semiconductor fine particles in the CBD film forming solution 7 and attaching the aggregates 5 of the compound semiconductor fine particles to the orientation plane c, the orientation becomes local again as shown in FIG. The surface is changed to a rough surface in which other orientation planes are locally formed.

Here, the concentration and temperature of the film-forming solution 7 are not particularly limited, but the formation condition of the dense structure with respect to the formation condition of the rough structure is that the film formation rate of the compound semiconductor layer 24 is twice or more, and the compound semiconductor The average particle size of the fine particle aggregate 5 is preferably ½ or less. For example, according to FIG. 3, the formation condition of the rough structure is a film formation rate of 2 nm / min and an average particle diameter of 4 μm, and the formation condition of the dense structure is a film formation rate of 5 nm / min and an average particle diameter of 2 μm. In addition, as long as it may expose to air every time it laminates | stacks, you may alternately immerse in each film-forming solution 7 from which the particle size distribution of the aggregate 5 of compound semiconductor fine particles differs.

1: Photoelectric conversion element 2: Classification mechanism 3: Rotating tank 4: Rotor 5: Compound semiconductor fine particle aggregate 5a: Lightweight aggregate 5b: Heavy weight aggregate 6: Separation tube 6a: Lightweight aggregate separation tube 6b: Weight aggregation Material separation tube 7: Film forming solution 8: Tank 8a: Diffusion tank 8b: Film forming tank 10: Film forming apparatus 11: Meter 12: Solution supply sources 13a, 13b, 13c: Pumps 14a, 14b: Supply pipe 15a 15b: Discharge piping 16a, 16b: Circulation piping 17a, 17b, 17c, 17d, 17e: Valve 18a: Film formation piping, 18b: Reuse piping, 18c: Recovery piping 19: Drain 20: Rectifying plate 21: Substrate 22: first electrode 23: light absorption layer 24: compound semiconductor layer 25: second electrode 26: third electrode a: film b of alignment plane a: film c of alignment plane b: film of alignment plane c

Claims (6)

  The agglomerates in the film-forming solution for forming the compound semiconductor film by the CBD method are classified by centrifugation at least one of before and during the film formation, whereby the aggregation in the film-forming solution is performed. The manufacturing method of the compound semiconductor film which controls the average particle size of a thing to below a predetermined value.   The method for producing a compound semiconductor film according to claim 1, wherein during the formation of the compound semiconductor film, classification is performed by changing a predetermined value of an average particle size of the aggregates in a plurality of stages.   3. The method for producing a compound semiconductor film according to claim 1, wherein the average particle size of the aggregate is periodically controlled by periodically performing the classification by centrifugation. A film forming tank for containing a film forming solution used for the CBD method and forming a compound semiconductor film by the CBD method;
An apparatus for producing a compound semiconductor film, comprising: a classification mechanism that centrifuges and classifies aggregates in the film-forming solution to be circulated between the film-forming tanks. The classification mechanism includes a rotating tank that stores the film-forming solution supplied from the film-forming tank;
A rotating means for rotating and flowing the film-forming solution stored therein;
A light-weight agglomerate separation tube having one end disposed in the rotary tank;
5. The compound semiconductor film according to claim 4, wherein the light-weight agglomerate separation tube extracts agglomerates having a particle size of a predetermined value or less from the rotating film-forming solution and returns it to the film-forming tank. Manufacturing equipment.   The apparatus for producing a compound semiconductor film according to claim 5, wherein the lightweight aggregate separation tube is movable from a center side to an outer peripheral side in the film formation tank.