JP2001274439A - Electrode forming method for spherical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce costs for electrode formation while including facility costs by providing mass-production technology for forming positive and negative electrodes in a granulated spherical semiconductor device. SOLUTION: A contact hole 12 for positive electrode and a contact hole 13 for negative electrode are formed on the surface of a spherical semiconductor device 11 for constituting a solar battery cell provided with a pn bond 7 and a spherical crystal 2 of a p-type semiconductor, and this spherical semiconductor device 11 is immersed in a plating liquid 23. In the state of radiating no light, nonelectrolytic plating treatment is performed and a positive electrode 15 coupled to the p-type semiconductor of the spherical crystal 2 is formed inside the contact hole 12 for positive electrode. Next, the spherical semiconductor device 11 is immersed in the other plating liquid and while generating a photovoltaic power by radiating white light, the negative electrode is formed in a contact hole 13 for negative electrode by nonelectrolytic plating treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for forming a positive electrode and a negative electrode by electroless plating on a spherical semiconductor device having a photovoltaic power generation unit.

2. Description of the Related Art The applicant of the present application has published International Publication
As shown in Japanese Patent Publication No. 155983 and WO 99/10935, an n-type or p-type diffusion layer is formed on the surface of a spherical p-type or n-type semiconductor spherical crystal (for example, having a size of about 1 to 2 mmφ). To form a pn junction, form an insulating film or a semiconductor film on the surface thereof, and propose a spherical semiconductor device in which a positive electrode and a negative electrode opposed to each other with a central portion of the spherical crystal interposed therebetween. Researching practical application.

The spherical semiconductor device can be used as a photovoltaic cell that generates electric power by solar energy, a photocatalytic cell that generates an electrochemical reaction by receiving light energy, a light emitting diode cell that emits light by electric energy, and the like. When a solar cell is configured with this spherical semiconductor device, a large-capacity solar cell can be configured by connecting a plurality of solar cells connected in series in a plurality of columns in parallel. In addition, since the solar cell is made of a spherical semiconductor element, even if the incident direction of sunlight changes, the solar cell can have a structure in which the absorption efficiency for absorbing sunlight hardly decreases, so that the solar cell is an excellent solar cell. . Solar cells are more promising because they can be manufactured at low cost using polycrystalline silicon as a material.

[0003] When a photocatalyst device is constituted by this spherical semiconductor device, a photocatalyst device in which a number of photocatalyst cells capable of generating a necessary electromotive force according to the type of a chemical reaction are connected in series,
What is necessary is just to set many in a reaction liquid, and to irradiate light with a light irradiation means. This spherical semiconductor device can be manufactured at low cost, and can be recycled and reused.

On the other hand, US Pat. No. 4,173,494 discloses that a spherical semiconductor element having a large number of photovoltaic power generation sections is connected on a common electrode film, and individual electrodes are formed on each of the spherical semiconductor elements. Thus, a technology for forming a solar cell module has been proposed. U.S. Pat. No. 3,025,335 discloses connecting a spherical semiconductor element having a large number of photovoltaic power generating parts on a common electrode film, and connecting these spherical semiconductor elements to a common electrode film having a polarity different from that of the common electrode film. There is proposed a technology for connecting a solar cell module to a solar cell module.

As shown in the above-mentioned International Publication, in the above-mentioned spherical semiconductor device, it is necessary to form a pair of electrodes (a positive electrode and a negative electrode) opposed to each other with the center of the spherical crystal interposed therebetween. The electrode was formed by forming a titanium film on the electrode formation site and then forming a nickel film by a chemical vapor deposition technique. In this case, 1
Chemical vapor deposition is performed with a pair of contact holes formed and a plurality of spherical crystals arranged in a plane so that the contact holes are exposed.

[0006]

As described above, the method of forming an electrode on a granular spherical semiconductor device by chemical vapor deposition requires a special chemical vapor deposition apparatus, so that the equipment cost is high, Since the cycle time of formation is long and the number of spherical semiconductor devices that can be chemically vapor-deposited at one time is limited, there are problems that the semiconductor device is not suitable for mass production and that the cost of forming electrodes is high. An object of the present invention is to provide a mass production technique for forming positive and negative electrodes on a granular spherical semiconductor element, to reduce the cost of forming electrodes including equipment costs, and the like.

[0007]

According to a first aspect of the present invention, there is provided a method for forming an electrode of a spherical semiconductor element, wherein a photovoltaic generator including an n-type diffusion layer and a pn junction is formed on a surface of a spherical crystal of a p-type semiconductor. In addition, the surface of the spherical semiconductor element whose surface is covered with a light-transmitting coating made of an insulator or a semiconductor,
In a method of forming a pair of electrodes opposed to each other across a center of a spherical crystal, a contact hole for a positive electrode exposing a spherical crystal of a p-type semiconductor by removing the film at a portion where the pair of electrodes is formed. And a first step of forming a negative electrode contact hole exposing the n-type diffusion layer, and immersing the spherical semiconductor element in a first plating solution containing metal ions,
A second step of forming a positive electrode in a positive electrode contact hole by performing electroless plating without irradiation with light, and immersing the spherical semiconductor element in a second plating solution containing metal ions and irradiating with light. And forming a negative electrode in the negative electrode contact hole by electroless plating.

In the first step, the coating on the surface of the spherical semiconductor element where a pair of electrodes is formed is removed, and a contact hole for the positive electrode exposing the spherical crystal of the p-type semiconductor and an n-type diffusion A contact hole for a negative electrode exposing the layer is formed. In this case, for example, by etching in a state where a region where both contact holes are not formed is masked with a corrosion-resistant photosensitive resin film, a light-transmitting film made of an insulator or a semiconductor is removed. To form

In a second step, the spherical semiconductor element is immersed in a first plating solution containing metal ions and subjected to electroless plating without irradiation with light to form a positive electrode in a positive electrode contact hole. At this time, in a state where light is not irradiated, the surface of the p-type semiconductor exposed to the contact hole for the positive electrode has a (-) potential more than the surface of the n-type diffusion layer exposed to the contact hole for the negative electrode. , About 10-20
When the electroless plating is performed, metal ions in the first plating solution are bonded to the surface of the p-type semiconductor in the contact hole for the positive electrode, and the positive electrode is formed in a film shape.

In the third step, the spherical semiconductor element is immersed in a second plating solution containing metal ions, and subjected to electroless plating for about 10 to 20 minutes while being irradiated with light such as white light, for example. A negative electrode in the contact hole for use. In the state where the spherical semiconductor element is irradiated with light, photovoltaic power is generated by the photovoltaic power generator, and the p-type semiconductor has a (+) potential,
Since the n-type diffusion layer has a (-) potential, the metal ions in the plating solution are combined with the n-type diffusion layer exposed in the negative electrode contact hole, and the n-type diffusion layer is formed in the negative electrode contact hole. A negative electrode is formed on the surface in the form of a film.

According to a second aspect of the present invention, there is provided a method for forming an electrode of a spherical semiconductor device, comprising the steps of: forming a p-type diffusion layer on a surface of a spherical crystal of an n-type semiconductor;
A pair of photovoltaic generators including a junction and a surface portion of a spherical semiconductor element whose surface is covered with a light-transmitting coating made of an insulator or a semiconductor is opposed to the surface portion of the spherical semiconductor element with the center of the spherical crystal interposed therebetween. The method of forming the electrode of
A first contact hole for exposing a spherical crystal of an n-type semiconductor and a contact hole for a positive electrode exposing a p-type diffusion layer are formed by removing the film at a portion where a pair of electrodes are formed. A second step of immersing the semiconductor element in a first plating solution containing metal ions and performing an electroless plating process without irradiating light to form a positive electrode in a positive electrode contact hole; and A third step of immersing in a second plating solution containing metal ions, performing electroless plating while irradiating light, and forming a negative electrode in a negative electrode contact hole. is there.

According to a second aspect of the present invention, in the first aspect, the p-type semiconductor is an n-type semiconductor and the n-type diffusion layer is a p-type semiconductor.
In the first step, the contact hole for the negative electrode exposing the spherical crystal n-type semiconductor and the positive electrode exposing the p-type diffusion layer are formed in the first step. An electrode contact hole is formed. Next, in the same manner as in claim 1, in the second step, a positive electrode is formed on the surface of the p-type diffusion layer exposed in the positive electrode contact hole, and then, in the third step, the negative electrode contact hole is formed. A negative electrode is formed on the surface of the n-type semiconductor exposed inside.

Here, when the first plating solution contains Cu ions (claim 3), the Cu ions are apt to be plated in response to a slight potential difference, so that a positive electrode made of copper having excellent conductivity is formed. can do. When the second plating solution contains Ni ions (Claim 4), the Ni ions are C
Although the reactivity is not as high as that of u ions, plating is performed in a state where a photoelectromotive force is applied, so that a negative electrode made of nickel having excellent conductivity can be formed.

In the case where the coating comprises a coating of SiO ₂ (silicon oxide) and a coating of TiO ₂ (titanium oxide) outside the coating (claim 5), the light is generated by a photovoltaic power generation unit including a diffusion layer and a pn junction. An electromotive force can be generated, and a photoelectromotive force due to TiO ₂ can also be generated. When the coating is a TiO ₂ coating (claim 6), the structure of the coating of the spherical semiconductor element is simplified, and a photovoltaic power can be generated in a photovoltaic power generation unit including a diffusion layer and a pn junction. Photovoltaic power can also be generated by titanium oxide.

[0015]

Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is an example in which the present invention is applied to a spherical semiconductor element for constituting a solar cell. First, the structure of the solar cell will be described. As shown in FIG. 13, the solar cell 1 includes a spherical crystal 2 made of a p-type silicon semiconductor, an n-type diffusion layer 6 formed on most of the surface of the spherical crystal 2, and a spherical crystal 2. A pair of electrodes (positive electrode 15 and negative electrode 16) opposed to each other with the center of 2 interposed therebetween, and light-transmitting SiO ₂ (parts of the surface of the spherical crystal 2 other than the positive electrode 15 and the negative electrode 16) Coating 9 of silicon oxide) and this SiO ₂
And a light-transmitting TiO ₂ (titanium oxide) film 10 formed on the surface of the film 9.

The n-type diffusion layer 6 and pn
A photovoltaic generator including the junction 7 is formed, and a micro photovoltaic cell that generates photovoltaic power by the spherical crystal 2 and the photovoltaic generator is configured. Next, a manufacturing method for manufacturing the solar cell 1 will be described. In the first step, FIG.
As shown in FIG. 1, a spherical crystal 2 made of a spherical p-type silicon semiconductor is manufactured. The spherical crystal 2 is formed into a true spherical shape having a diameter of, for example, about 1.5 mm using a p-type silicon semiconductor having an impurity concentration of about 1.5 × 10 ¹⁶ cm ⁻³ .

Such a true spherical single crystal spherical crystal 2
Is produced as a spherical crystal 2 with a smooth surface by melting polycrystalline or single-crystal silicon semiconductor granules using an electromagnetic floating heating device, then releasing the floating and solidifying it while freely falling in a falling tube. can do.
Further, if necessary, 600 to 900 in an inert gas atmosphere.
To improve the crystal structure by heating to a temperature of ℃ to improve the crystal structure, or to perform multiple drop processes including melting, falling and solidification to precipitate impurities on the surface and remove the impurities by etching Thus, a high-quality spherical crystal can be obtained.

Next, in a second step, as shown in FIG. 2, the spherical crystal 2 is heated to about 1150 ° C. in an atmosphere containing oxygen, and a SiO ₂ (silicon oxide) film having a thickness of about 1 μm is formed on the entire surface. Form 3 Next, in a third step, as shown in FIG. 3, the spherical crystal 2 on which the coating 3 has been formed is placed on a support plate 4 made of glass, for example, and the radius of the spherical crystal 2 is placed on the support plate 4. A liquid resin film 5 of an acid-resistant synthetic resin having a thickness of about half of
After the ４ is covered with the resin film 5, the resin film 5 is solidified.

Next, in a fourth step, the portion of the spherical crystal 2 exposed from the resin film 5 is etched using a diluted hydrofluoric acid aqueous solution, and the SiO ₂ film 3 is dissolved and removed. The result is as shown in FIG. Next, in a fifth step, as shown in FIG. 5, the resin film 5 is dissolved with a solvent, the spherical crystal 2 is removed from the support plate 4, and the surface of the spherical crystal 2 is washed using an appropriate cleaning solution. An impurity element (for example, P or As) for forming the n-type diffusion layer 6 is thermally diffused into a portion of the surface portion of the spherical crystal 2 that is not masked by the coating 3 by a known method, and The diffusion layer 6 is formed. Note that the n-type semiconductor of the n-type diffusion layer 6 is correctly n-type semiconductor.
⁺ Type semiconductor.

By the thermal diffusion, an SiO ₂ coating 8 connected to the coating 3 is formed on the surface of the n-type diffusion layer 6. As a result, a pn junction 7 between the spherical crystal 2 and the n-type diffusion layer 6 is formed.
Is formed at a depth of about 0.5 to 0.8 μm from the surface of the spherical crystal 2. When light such as sunlight is received from the outside, the pn junction 7 forms photoexcited carriers (electrons and holes).
To generate photovoltaic power.

Next, in a sixth step, the coating films 3 and 8 on the surface of the spherical crystal 2 are removed by etching using a diluted hydrofluoric acid aqueous solution. Next, as shown in FIG. 6, a spherical crystal 2 including an n-type diffusion layer 6 is formed by a known technique such as physical vapor deposition (PVD) or chemical vapor deposition (CVD).
Si for inactivating the surface of the pn junction 7
An O ₂ coating 9 is formed, and TiO 2
₂ A film 10 of (titanium oxide) is formed.

The coatings 9 and 10 reduce and stabilize the leakage current on the surface of the pn junction 7, and reduce light reflection on the surface due to a difference in refractive index. That is, both films 9 and 10 are insulating films and passivation films that protect the pn junction 7 and passivate the surface, and function as anti-reflection films that prevent reflection of light. Since the TiO ₂ is an n-type semiconductor and generates photovoltaic power, about 42% of the incident light is used.
Light having a wavelength of 0 nm or less is absorbed by the TiO ₂ coating 10, and light having a longer wavelength is transmitted through the SiO ₂ coating 9 and absorbed by the spherical crystal 2.

The thicknesses of the two films 9 and 10 are set in consideration of the function of the pn junction 7 as a passivation film, the photovoltaic function of the film 10 and the degree of transmission of the spectrum to be received. For example, the thickness of the SiO ₂ coating 9 is about 0.3 to 0.7 μm, and the thickness of the TiO ₂ coating 10 is about 0.3 to 1.0 μm. Thus, first, the spherical semiconductor element 11 as shown in FIG. 6 is manufactured.

Next, in the seventh step, as shown in FIG. 7, at the lower end of the spherical semiconductor element 11 and the top of the n-type diffusion layer 6, two transparent coatings 9, 10 are applied to the center of the spherical crystal 2. A contact hole 12 for a positive electrode and a contact hole 13 for a negative electrode having a diameter of about 0.5 mm are formed so as to be opposed to each other. In this case, the corrosion-resistant photosensitive resin film 14
7, both contact holes 12 and 13 are formed by known photolithography and plasma etching. The contact hole 12 for the positive electrode is an opening for exposing the p-type semiconductor of the spherical crystal, and the contact hole 13 for the negative electrode is
An opening for exposing the shaped diffusion layer 6. As a result, the spherical semiconductor element 11 shown in FIG. 8 is obtained.

Next, in the eighth step, as shown in FIG.
The positive electrode 15 made of a Cu film is formed in the positive electrode contact hole 12 by performing electroless plating in a state where the substrate is not irradiated with light. This plating solution is, for example, 1
CuSO of 200g of water 000cc ₄ · 5H ₂ O and 1
0 HF (hydrogen fluoride) is mixed with a required amount of a plating solution having a composition.
And a plating tank 22 made of stainless steel, and the plating tank 22
And a plurality of spherical semiconductor elements 11 in the plating solution 23.
And plating them simultaneously. FIG.
Here, the spherical semiconductor element 11 is illustrated in an extremely enlarged manner.

At this time, the temperature of the plating solution 23 is about 50 to
The temperature is set to 60 ° C., and a plating process is performed for about 10 to 20 minutes. During this plating process, the p-type semiconductor has a (-) potential with respect to the n-type diffusion layer 6, so that the Cu ⁺⁺ in the plating solution 23
The ions are combined with the surface of the p-type semiconductor exposed in the contact hole 12 for the positive electrode to form a C layer having a thickness of about 5 to 10 μm.
A positive electrode 15 of u is formed. After this plating process, the spherical semiconductor element 11 is in the state shown in FIG. The HF contained in the plating solution 23 may be omitted.

Next, in a ninth step, as shown in FIG.
The negative electrode 16 made of a Ni film is formed in the negative electrode contact hole 13 by applying electroless plating while immersing the negative electrode 3 in white light B emitted from a tungsten lamp. This plating solution is, for example,
A necessary amount of the plating solution NiSO ₄ · 6H ₂ O and the composition of a mixture of NH ₃ (ammonia) in 10cc of 200 g,
The plating apparatus 30 includes an outer case 31, a plating tank 32 made of stainless steel and having a mirror-like Ni film formed on the inner surface, a plating solution 33 contained in the plating tank 32, and an electric heater 34. . In FIG. 11, the spherical semiconductor element 11 is illustrated in an extremely enlarged manner.

The inner surface of the inner periphery at the lower part of the plating tank 32 forms a paraboloid so that the irradiation light is efficiently concentrated on a large number of spherical semiconductor elements 11 at the bottom. A large number of spherical semiconductor elements 11 on which the positive electrode 15 has been formed are accommodated in the plating solution 33, and they are subjected to plating simultaneously. At this time, the temperature of the plating solution 33 is about 90-100 ° C., and about 10-2
Perform a 0 minute plating process. In this plating process, the p-type semiconductor has a (+) potential, and the n-type diffusion layer 6 has a (-) potential due to the photovoltaic power generated in the photovoltaic power generation section of the spherical semiconductor element 11.
Since the potential becomes Ni, the Ni ⁺⁺ ions in the plating solution 33 are exposed in the contact holes 13 for the negative electrode.
To form a negative electrode 16 of Ni having a thickness of about 5 to 10 μm. After this plating process,
The spherical semiconductor element 11 is in the state shown in FIG.

Next, in a tenth step, the spherical semiconductor element 11 on which the positive electrode 15 and the negative electrode 16 are formed as described above is immersed in molten solder in a solder bath (not shown).
When the solder layers 17 and 18 are formed on the surfaces of the negative electrode 5 and the negative electrode 16, respectively, and cleaned, the spherical semiconductor element 11 (this is a solar cell) in the state shown in FIG. 13 is obtained.

According to the electrode forming method performed in the seventh to ninth steps, the Cu (copper) positive electrode 15 and the Ni
The (nickel) negative electrode 16 can be formed to a desired thickness. Since the positive electrode 15 is made of Cu and the negative electrode 16 is made of Ni, the positive and negative electrodes can be identified.
Since the negative electrode 16 of i is magnetic, it is possible to distinguish between the positive and negative electrodes by the magnetic force. In a state where many spherical semiconductor elements 11 are successively immersed in the plating solutions 23 and 33,
Plating can be performed, and the positive and negative electrodes 15 and 16 can be efficiently formed in a large number of spherical semiconductor elements 11 in a short cycle time by the plating. In addition, since the positive and negative electrodes 15 and 16 can be formed by the plating apparatuses 20 and 30 having a simple configuration, equipment costs and electrode forming costs can be significantly reduced.

Next, a description will be given of a modification in which the above-described embodiment is partially modified. 1) The SiO ₂ coating 9 is not essential and may be omitted. In this case, the solar cell 1A is as shown in FIG. Further, a transparent glass film or a Si ₃ N ₄ film may be formed instead of the TiO ₂ film 10. Instead of the coatings 9 and 10, a coating made of another insulator or semiconductor may be formed.

2) Although the spherical semiconductor element 11 has been described as being applied to a solar cell as an example, it may be applied to a photocatalytic cell instead of a solar cell. In this case, the negative electrode 16 is formed so as to be separated from the TiO ₂ coating 10. Further, the spherical semiconductor element may be applied as a light emitting diode cell instead of a solar cell.
The semiconductor forming the spherical crystal may be a semiconductor other than silicon.

3) Instead of copper ions, A
By adding u ions or Ni ions, a positive electrode of Au or Ni can be formed. Moreover, Ni is used for the plating solution 33.
If Au ions are used instead of ions, a negative electrode of Au can be formed. The positive and negative electrodes are Cu, N
It is not limited to i, Au, etc., but may be made of other metals. The plating solutions 23 and 33 are merely examples, and plating solutions of other compositions may be applied. The temperature and time of the plating process are also examples, and are limited to those of the examples. Not in translation.

4) In the above embodiment, the spherical crystal 2 of p-type semiconductor is manufactured, and the diffusion layer 6 and the coatings 9 and 10 are formed on the surface thereof.
Has been described as an example, but a spherical semiconductor element in which a spherical crystal of an n-type semiconductor is manufactured and a p-type diffusion layer and coatings 9 and 10 are formed on the surface thereof,
A positive electrode and a negative electrode can be formed in the same manner as described above. In this case, in the seventh step, a contact hole for a positive electrode exposing a p-type diffusion layer and a contact hole for a negative electrode exposing an n-type semiconductor are formed in the same manner as in the above embodiment.

Next, in the eighth step, a positive electrode coupled to the p-type diffusion layer is formed in the same manner as in the above embodiment.
Next, in a ninth step, a negative electrode coupled to the n-type semiconductor of the spherical crystal is formed in the same manner as in the above embodiment.

[0036]

According to the first aspect of the present invention, a pair of contact holes for positive and negative electrodes are formed in the first step, and are immersed in the first plating solution in the second step without being irradiated with light. forming a positive electrode coupled to the p-type semiconductor, immersing in a second plating solution in a third step and irradiating light to form a negative electrode coupled to the n-type diffusion layer; If the positive and negative electrodes can be made of different metals or the same kind of metal and have desired thicknesses, and the positive and negative electrodes are made of different metals, the positive and negative electrodes can be easily identified. Positive and negative electrodes can be efficiently formed in a large number of spherical semiconductor elements by a plating process in a short cycle time, and electrodes can be formed by a plating apparatus having a simple structure, so that equipment costs and electrode forming costs can be reduced, which is suitable for mass production. The effect of being an electrode forming technique can be obtained.

According to the second aspect of the present invention, a pair of contact holes for positive and negative electrodes are formed in the first step, and the contact holes are immersed in the first plating solution in the second step so as to be p-type without irradiating light. In order to form a positive electrode coupled to the diffusion layer, and to form a negative electrode coupled to the n-type semiconductor while irradiating light by immersing in a second plating solution in a third step, The same effect as the invention can be obtained.

According to the third aspect of the present invention, since the first plating solution contains Cu ions, a copper positive electrode having excellent conductivity can be reliably formed by effectively utilizing a weak potential difference. The other effects are the same as those of the first or second aspect. According to the invention of claim 4, since the second plating solution contains Ni ions, it is possible to reliably form a negative electrode of nickel having excellent conductivity. Since the electrode is a copper positive electrode and a nickel negative electrode, the positive and negative electrodes can be easily identified. In addition, since the nickel negative electrode is a magnetic material, it can be identified using magnetic force. The other effects are the same as those of the first or second aspect.

According to the fifth aspect of the present invention, the film is made of Si
Since it is composed of an O ₂ film and a TiO ₂ film outside thereof, a spherical semiconductor element capable of generating a photovoltaic power in a photovoltaic power generation section including a diffusion layer and a pn junction and generating a photovoltaic power of titanium oxide Becomes Other effects similar to those of any one of the first to fourth aspects are exhibited.

According to the invention of claim 6, the coating is made of Ti
Because of the O ₂ film, the structure of the film of the spherical semiconductor element is simplified, and a photovoltaic power can be generated in a photovoltaic power generation unit including a diffusion layer and a pn junction, and a photovoltaic power generated by titanium oxide is generated. The resulting spherical semiconductor element can be obtained. Other effects similar to those of any one of the first to fourth aspects are exhibited.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a spherical crystal of a p-type semiconductor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a state where a spherical crystal is covered with a coating.

FIG. 3 is a cross-sectional view of a state in which the spherical crystal of FIG. 2 is masked with a resin film.

FIG. 4 is a cross-sectional view showing a state where an etching process is performed after a mask.

FIG. 5 is a cross-sectional view of a spherical crystal on which an n-type diffusion layer is formed.

FIG. 6 is a cross-sectional view of a spherical semiconductor device having a film formed on the surface of a spherical crystal.

FIG. 7 is a cross-sectional view showing a state where positive and negative electrode contact holes are formed by masking with a photosensitive resin film.

8 is a cross-sectional view of the spherical semiconductor device in a state where the photosensitive resin film of FIG. 7 is removed.

FIG. 9 is a sectional view of a plating apparatus and a spherical semiconductor element.

FIG. 10 is a cross-sectional view of a spherical semiconductor element on which a positive electrode is formed.

FIG. 11 is a sectional view of a plating apparatus and a spherical semiconductor element.

FIG. 12 is a sectional view of a spherical semiconductor element on which positive and negative electrodes are formed.

FIG. 13 is a cross-sectional view of a solar battery cell including a spherical semiconductor element.

FIG. 14 is a cross-sectional view of a solar cell according to a modified embodiment.

[Explanation of symbols]

 2 Spherical crystal (p-type semiconductor) 6 Diffusion layer 7 pn junction 9 Coating of silicon oxide 10 Coating of titanium oxide 11 Spherical semiconductor element 12 Contact hole for positive electrode 13 Contact hole for negative electrode 15 Positive electrode 16 Negative electrode 20 Plating device 23 Plating solution 30 Plating device 33 Plating solution

Claims (6)

[Claims] 1. A photovoltaic generator including an n-type diffusion layer and a pn junction is formed on the surface of a spherical crystal of a p-type semiconductor, and the surface is covered with a light-transmitting coating made of an insulator or a semiconductor. A method of forming a pair of electrodes facing each other across the center of a spherical crystal on a surface portion of a spherical semiconductor element formed by removing the coating on a portion where the pair of electrodes is formed;
forming a first contact hole for a positive electrode exposing a spherical crystal of a p-type semiconductor and a contact hole for a negative electrode exposing an n-type diffusion layer; A second step of immersing in a plating solution and performing electroless plating in a state where light is not irradiated to form a positive electrode in a positive electrode contact hole; and immersing the spherical semiconductor element in a second plating solution containing metal ions. A third step of forming a negative electrode in a negative electrode contact hole by performing an electroless plating process in a state where light is irradiated, and a third step of forming an electrode for a spherical semiconductor element. 2. A photovoltaic generator including a p-type diffusion layer and a pn junction is formed on the surface of a spherical crystal of an n-type semiconductor, and the surface is covered with a light-transmitting coating made of an insulator or a semiconductor. A method of forming a pair of electrodes facing each other across the center of a spherical crystal on a surface portion of a spherical semiconductor element formed by removing the coating on a portion where the pair of electrodes is formed;
a first step of forming a contact hole for a negative electrode exposing a spherical crystal of an n-type semiconductor and a contact hole for a positive electrode exposing a p-type diffusion layer; A second step of immersing in a plating solution and performing electroless plating in a state where light is not irradiated to form a positive electrode in a positive electrode contact hole; and immersing the spherical semiconductor element in a second plating solution containing metal ions. A third step of forming a negative electrode in a negative electrode contact hole by performing an electroless plating process in a state where light is irradiated, and a third step of forming an electrode for a spherical semiconductor element. 3. The method according to claim 1, wherein the first plating solution contains Cu-on. 4. The method according to claim 3, wherein the second plating solution contains Ni ions. 5. The film according to claim 1, wherein said film comprises a SiO ₂ film and a TiO ₂ film outside thereof.
5. The method for forming an electrode of a spherical semiconductor device according to any one of 4. 6. The method for forming an electrode of a spherical semiconductor device according to claim 1, wherein said coating is a coating of TiO ₂ .