JPH1012908A - Manufacture of semiconductor device and particulate semiconductor film, and photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device and a particulate semiconductor film which have a high mobility and a low defect density even in a low- temperature process and which are uniform in the plane and depth directions, by electrically connecting a plurality of semiconductor crystal particulate nuclei which are discretely laminated on a substrate. SOLUTION: Silicon crystal particulates, melted near the surface thereof when passing on the optical path of a laser beam emitted from a laser light source, flocculate in a state of being electrically connected onto a substrate 22, thereby forming a thin film on the substrate 22. Thus, the thin film is made of silicon crystal particulate nuclei 30 which are not melted on the substrate 22, and a polycrystal portion 31 which has been melted by the laser and then recrystallized. Thus, a semiconductor device and a particulate semiconductor film which have a high mobility and a low defect density even in a low- temperature process and which are uniform in the plane and depth directions may be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a fine particle semiconductor film containing semiconductor crystal fine particles as a main component, a method for manufacturing the fine particle semiconductor film, and a photoelectric conversion element.

[0002]

2. Description of the Related Art In a liquid crystal display using a thin film transistor, a technology capable of forming a thin film having higher mobility and lower defect density by using a low-temperature process has been developed in order to realize a high-performance and low-cost device. It is urgently required.

Conventionally, a hydrogenated amorphous silicon (a-Si: H) film or a polycrystalline silicon (poly-Si) film has been widely used as a thin film of the device. a-S
As for the i: H film, a high-quality film having a defect density of 10 ¹⁵ cm ⁻³ or less can be formed at a low substrate temperature of about 300 ° C. or less by using a plasma CVD method or the like. However, unlike crystals, it is extremely difficult to achieve a high mobility of 2 cm ² / Vs or more because of irregularities in the silicon network.

On the other hand, in the case of a poly-Si film, about 600
Several hundred cm by a thermal CVD method in a high temperature process
A poly-Si film having a high mobility of ² / Vs or more can be formed. However, if the substrate is formed at 450 ° C. or lower in order to use a low-cost substrate, a poly-Si film cannot be formed. So 450 ° C
An a-Si: H film recrystallization method in which an a-Si film is formed at the following temperature and then recrystallized using excimer laser annealing is widely used. By this recrystallization method, a poly-Si film having high mobility can be formed.

FIG. 13 shows a typical cross section of a film obtained by the recrystallization method. 80 is a substrate, 81 is a polycrystalline nucleus, 82
Denotes a crystal grain boundary, 83a and 83b denote each one-shot width of the laser, and 83c denotes an overlapping portion of the laser light. In the overlapping portion 83c, since recrystallization proceeds further, the crystal grains become larger on average than the surroundings, so that planar unevenness occurs.
Therefore, there is a problem that the characteristics of the transistor when miniaturized vary. In addition, since recrystallization proceeds from the film surface on the laser incident side, the crystal grains on the substrate side become small, so that unevenness in the depth direction occurs. Therefore, there are problems such as poor reproducibility of film characteristics (particularly mobility).

By the way, a-Si: H or poly
As an element using -Si, there is a solar cell. Currently G
25% or more for compound systems such as aAs, 23% or more for single crystal Si and polycrystalline Si, and 13% for a-Si
The above conversion efficiencies have been reported. In order to form a solar cell made of crystalline silicon having high conversion efficiency, crystalline silicon must be formed at a temperature of 450 ° C. or higher. For that purpose, a heat-resistant glass substrate had to be used. Since heat-resistant glass is expensive, there has been a problem that the manufacturing cost is high.

However, for full-scale use for power generation and household use, it is urgently necessary to drastically reduce costs while maintaining high conversion efficiency. Therefore, a low-temperature thin film formed on a low-cost substrate (for example, low-melting glass, flexible film, metal) by using a crystalline semiconductor thin film such as GaAs or Si having a high conversion efficiency by using a process of 450 ° C. or lower. There is a need for a forming process.

A tandem type structure has been known as a method for obtaining higher conversion efficiency. This has a structure in which solar cells of different materials having different band gaps are stacked, and maximizes the absorptivity of sunlight to improve light efficiency. As a typical example of this structure, GaAs / S
i, and a conversion efficiency of 30% or more is reported. However, there has not yet been any case of forming such a tandem-type solar cell on a low-cost substrate.

[0009]

Conventionally, an a-Si: H film cannot be formed with high mobility by a low-temperature process. Further, a poly-Si film cannot be formed at a low temperature, and a-
After growing the Si film, laser annealing is performed to
When a ly-Si film is formed, a film having a uniform planar and depth direction cannot be obtained, and the characteristics of the transistor formed on the poly-Si film are different, and the reproducibility of the film characteristics is poor. there were. Further, in a solar cell, a crystalline film with high conversion efficiency could not be formed using a low-temperature process, so that it was not possible to achieve both low cost and high conversion efficiency.

An object of the present invention is to provide a semiconductor device having a high mobility and a low defect density even in a low-temperature process, and a method for manufacturing a semiconductor device and a fine particle semiconductor film which are uniform in a planar and depth direction. Another object is to provide a photoelectric conversion element capable of forming a crystalline film with high conversion efficiency by a low-temperature process of 450 ° C. or lower.

[0011]

[Means for Solving the Problems]

(1) A semiconductor device according to the present invention is a semiconductor device in which a fine particle semiconductor film is formed on a substrate, wherein the fine particle semiconductor film includes a plurality of semiconductor crystals discretely stacked on the substrate. It is characterized by comprising a fine particle nucleus and a polycrystalline semiconductor portion surrounding at least a part of these semiconductor crystal fine particle nuclei and electrically connecting adjacent semiconductor crystal fine particle nuclei. (2) The semiconductor device of the present invention is a semiconductor device having a fine particle semiconductor film formed on a substrate, wherein the fine particle semiconductor film comprises a plurality of semiconductor crystal fine particle nuclei discretely stacked on the substrate. A polycrystalline semiconductor portion surrounding at least a portion of these semiconductor crystal fine particle nuclei and electrically connecting adjacent semiconductor crystal fine particle nuclei, and an amorphous semiconductor portion surrounding at least a portion of the polycrystalline semiconductor portion. It is characterized by becoming. (3) In the method for producing a fine particle semiconductor film of the present invention, a step of supplying semiconductor crystal fine particles on a surface of a substrate provided for forming the fine particle semiconductor film; Melting the vicinity of the surface. (4) The photoelectric conversion element of the present invention is a photoelectric conversion element that has a pn junction of a p-type semiconductor and an n-type semiconductor and converts light energy into electric energy.
At least one of the n-type semiconductors is made of a fine particle semiconductor film. (5) The fine particle semiconductor film in the semiconductor device according to (1) preferably has an electron mobility of 10 cm ² / Vs or more, or a hole mobility of 1 cm ² / Vs or more. (6) In the fine particle semiconductor film in the semiconductor device according to (1), the volume fraction of the semiconductor crystal fine particle nucleus is desirably in the range of 5 to 95%. (7) The fine particle semiconductor film in the semiconductor device described in (2) preferably has an electron mobility of 2 cm ² / Vs or more, or a hole mobility of 0.1 cm ² / Vs or more. (8) In the fine particle semiconductor film in the semiconductor device described in (2), the volume fraction of the semiconductor crystal fine particle nucleus is in the range of 5 to 95%, and the volume fraction of the amorphous semiconductor portion is 0 to 50%. Is desirably within the range. (9) In the photoelectric conversion element according to (4), the fine particle semiconductor film is composed of a plurality of semiconductor crystal fine particles having different band gaps. (10) The photoelectric conversion element according to (4) has a junction including a fine particle semiconductor film and a microcrystalline semiconductor film or an amorphous semiconductor film. (11) The photoelectric conversion element according to (4) is of a tandem type.

The structure of an apparatus for forming a fine particle semiconductor film in the fine particle semiconductor device of the present invention will be described below. (12) a film forming chamber in which a substrate to be used for forming a fine particle semiconductor film is arranged; a means for supplying semiconductor crystal fine particles to be deposited on the substrate into the film forming chamber; Means for melting the vicinity of the surface of the semiconductor crystal fine particles. (13) A growth chamber for growing semiconductor crystal fine particles by a plasma gas phase reaction method, and a film formation chamber connected to the growth chamber via a plurality of orifices and in which a substrate for forming a fine particle semiconductor film is arranged. And melting means for melting the vicinity of the surface of the semiconductor crystal fine particles above the substrate. (14) The apparatus for manufacturing a fine particle semiconductor film according to (12) or (13) has means for applying a magnetic field to the film forming chamber. (15) The apparatus for manufacturing a fine particle semiconductor film according to (12) or (13) has means for applying a bias voltage to the substrate. (16) The apparatus for manufacturing a fine particle semiconductor film according to (12) has means for adjusting the distance between the orifice and the substrate to a desired value. (17) The apparatus for manufacturing a fine particle semiconductor film according to (12) has means for introducing an inert gas having a large atomic radius, such as Ar, Kr, or Xe, into the growth chamber. (18) The means for supplying semiconductor crystal fine particles of the apparatus for manufacturing a fine particle semiconductor film according to (13) supplies the fine semiconductor particle powder into the film forming chamber. (19) The means for melting the semiconductor crystal fine particles of the fine particle semiconductor film manufacturing apparatus according to (12) or (13) is for introducing a laser beam from outside into the film forming chamber. (20) The means for melting the semiconductor crystal fine particles of the apparatus for manufacturing a fine particle semiconductor film according to (12) or (13) generates thermal plasma to melt the semiconductor crystal fine particles.

(Operation) The semiconductor device of the present invention includes a fine particle semiconductor film, and the semiconductor crystal fine particle nucleus in the fine particle semiconductor film serves as a main conduction path of electrons and holes. Good electrical connection by the parts. Therefore, the conduction carriers can have higher mobility than a conventional semiconductor thin film in which only a polycrystalline or amorphous body is a main conduction path. In addition, since the semiconductor crystal fine particle nucleus having a very small number of defects is mainly used, the defect density is extremely low as compared with a conventional semiconductor thin film consisting only of a polycrystalline or amorphous body.

Further, according to the method for producing a fine particle semiconductor film of the present invention, the temperature of the substrate is set at 450 ° C.
Even in the following low-temperature process, a fine particle semiconductor film having high mobility and low defect density can be obtained. In addition, since the film can be formed without using a recrystallization process after film formation such as laser annealing, a uniform film can be obtained in the plane direction and the depth direction.

Further, if the position where the substrate and the semiconductor crystal fine particle nucleus are melted away from each other, the melted fine particles may come into contact with each other and stick to each other, so that the semiconductor fine particle nuclei in the film are formed with different sizes. Sometimes. Then, since the sizes of the semiconductor fine particle nuclei are different, the characteristics of the film are different. However, as in the present invention, the melting of the semiconductor fine particle nucleus
By performing the process near the upper part of the substrate, the size of the semiconductor crystal fine particle nuclei in the film becomes uniform.

In the photoelectric conversion device of the present invention, a crystalline thin film having high conversion efficiency can be formed at a temperature of 450 ° C. or less by using a fine particle semiconductor film. Therefore,
Since the substrate can be formed at a low substrate temperature, an inexpensive substrate can be used, and low cost and high conversion efficiency can be realized at the same time.

Further, when the photoelectric conversion element of the present invention is applied to a solar cell, it can be formed at a low substrate temperature of 450 ° C. or less, so that a crystalline system film is formed on a microcrystalline semiconductor film or an amorphous semiconductor film. It is possible to easily form a semiconductor junction in the form of a fine particle semiconductor film.

Further, by simultaneously supplying crystal fine particles of a plurality of substances and depositing them on a substrate, a thin film having crystal fine particle nuclei of a plurality of substances can be formed. By using such a film as a cell, it is possible to have the same properties as a tandem-type cell while being a single-type cell. This element has the same properties as the tandem cell but has a single cell structure, so that a low-cost photoelectric conversion element with high conversion efficiency can be manufactured.

Since a fine particle semiconductor film can be formed by a low-temperature process of 450 ° C. or less, a mixture of a crystalline semiconductor film and an amorphous or microcrystalline semiconductor film in a tandem cell including the fine particle semiconductor film. Can be formed at each ohmic connection of each cell, for example, by μc-Si or a-Si.
Can be used to form a pn junction. Of course, μ
The c-Si and a-Si films are formed at a temperature of 300 ° C. or less.
Since it can be formed by a plasma CVD method or the like, it is easy to deposit microcrystalline silicon (μc-Si) or a-Si on the fine particle semiconductor film.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a schematic view schematically showing an apparatus for manufacturing a fine particle semiconductor film according to a first embodiment of the present invention. Semiconductor crystal fine particle growth chamber 10 for producing semiconductor crystal fine particles
Is provided. Plasma CVD of semiconductor crystal particles
A source gas supply chamber 11 for storing a source gas to be formed by a method is provided outside the growth chamber 10. The source gas in the source gas supply chamber 11 is introduced into the growth chamber 10 via the valve 12. Further, in the growth chamber 10, a discharge plate 13 for supplying plasma power required for generating semiconductor crystal fine particles is provided. A high-frequency power supply 14 (for example, 144 MH) for supplying power to the discharge plate 13
z VHF band power supply) is provided outside the growth chamber 10,
It is connected to the discharge plate 13.

A film forming chamber 15 is connected to the growth chamber 10. A plurality of orifices 16 are provided between the growth chamber 10 and the film formation chamber 15 to uniformly introduce a gas containing semiconductor crystal fine particles generated in the growth chamber 10. An electromagnet 17 for generating a magnetic field for confining the semiconductor crystal fine particles is provided outside the film forming chamber 15. Electromagnet 1
Below 7, a laser light source 18 for melting the vicinity of the surface of the semiconductor crystal fine particles is provided. Then, the laser light emitted from the laser light source 18 is introduced into the film forming chamber 15 by adjusting the optical path and intensity by the cylindrical lens 19.

Near the lower part of the optical path of the laser light to be introduced,
Susceptor 21 heated to a predetermined temperature by heater 20
The substrate 22 is held thereon. A bias power supply 23 for applying a DC or AC bias voltage to the susceptor 21
Is provided. The susceptor 21 is provided with a movable mechanism 24.
This enables vertical and rotational movements, and the distance between the orifice 16 and the substrate 22 can be adjusted. In addition, the source gas supply chamber 1 is introduced so that the source gas is introduced from the source gas supply chamber 11 to the film formation chamber 15 as necessary.
A valve 26 is provided between 1 and the film forming chamber 15.

Next, the formation of a silicon crystal fine particle semiconductor film using the apparatus having the above configuration will be described as an example. After sufficiently evacuating the inside of the growth chamber 10 and the film formation chamber 15, a mixed gas of silane and argon gas is introduced into the growth chamber 10 from the source gas supply chamber 11. The pressure in the growth chamber 10 is set to 0.0
1 to ⁵ Torr, and the pressure of the film forming chamber 15 is set to 10 ^{-5 to 1} Torr.
r, the discharge plate 13 is connected to the high-frequency power source 14.
, A VHF power with high radical generation efficiency is applied to generate plasma.

Then, silicon crystal fine particles having a small particle diameter (diameter: several nm to several tens nm) are generated in the plasma.
Although the generated silicon crystal fine particles are negatively charged, they are pushed by the positive ion flow and stay on the sheath side of the discharge plate 13 having a negative potential. In addition, since the Ar positive ion flow having a large viscosity is directed toward the discharge plate 13 having a negative potential, the silicon crystal fine particles are less likely to escape from the vicinity of the discharge plate 13 and the residence time in the vicinity of the discharge plate 13 is prolonged. As a result, silicon crystal fine particles (several tens nm to a maximum of several μm, on average about 100 to 1000 nm) having a relatively large particle size can be grown near the discharge plate 13.

After a certain residence time, the silicon crystal fine particles move to the plurality of orifices 1 provided in the growth chamber 10.
6 and jumps out to the film forming chamber 15. The charged silicon crystal fine particles are not scattered in the direction of the inner wall of the film forming chamber 15 by the magnetic field given by the electromagnet 17 and are efficiently confined in the space of the film forming chamber 15 above the substrate 22.
The film forming speed increases.

When the silicon crystal fine particles pass on the optical path of the laser light emitted from the laser light source 18,
The vicinity of the surface is melted. Examples of the laser light source 18 include an excimer laser, a CO ₂ laser, a YAG laser, and the like, but any laser light source that can melt Si having a melting point of 1410 ° C. may be used. Then, the silicon crystal microparticles whose surface vicinity has been melted aggregate while being electrically connected to the substrate 22, and form a thin film on the substrate 22. At this time, even when the substrate temperature is as low as 450 ° C. or less, a thin film having high mobility and low defect density can be uniformly formed. Also,
When a bias voltage is applied to the susceptor 21 by the bias power supply 23, the charged silicon crystal fine particles can be more efficiently collected on the substrate, so that the film forming speed can be improved.

The orifice 1 is moved by the movable mechanism 24.
If the distance between the substrate 6 and the substrate is longer than a predetermined value, radicals (SiH3,
(SiH2, SiH, H, etc.) hardly reach the substrate 22, so that a thin film mainly composed of silicon crystal fine particles is formed. FIG. 2 shows a cross section of this thin film. It comprises a silicon crystal fine particle nucleus 30 not melted on the substrate 22 and a polycrystalline portion 31 melted and recrystallized by a laser. Here, 32 is a boundary of the silicon crystal fine particles attached to the substrate 22. However, since the actual boundary 32 is shared by the polycrystalline portions 31 of the adjacent fine particles, it is not always clearly observed.

Next, FIGS. 3 and 4 show the dependence of the electron mobility or hole mobility of the thin film on the volume fraction of the crystal fine particle nucleus 30. FIG. Here, both the electron mobility and the hole mobility show a common volume fraction dependency. 5% volume fraction
Between 95% and 95%, the electron mobility and the hole mobility increase as the volume fraction increases. However, when the volume fraction becomes 5% or less and 95% or more, it is understood that the electron mobility and the hole mobility sharply decrease. Therefore, the volume fraction of the silicon crystal fine particle nucleus 30 is 5% to 95%.
% Is desirable.

Further, if the distance between the substrate 22 and the orifice 16 is shorter than a predetermined value, the number of arrivals of radicals increases, so that amorphous silicon surrounds the electrically connected silicon crystal fine particle nuclei. A film can be formed. FIG. 5 shows a cross section of this thin film. The same components as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. The feature of this thin film is that an amorphous silicon portion 33 containing a silicon-hydrogen bond such as Si—H, Si—H ₂ , or Si—H ₃ is formed in the film, and a boundary 32 is formed by the amorphous silicon portion 33. That is, a film as if surrounded is formed. This thin film is characterized in that the surface flatness is improved as compared with the thin film of FIG.

FIGS. 6 and 7 show the dependence of the electron mobility or the hole mobility of the thin film on the volume fraction of the amorphous silicon portion 33. FIG. The electron mobility and the hole mobility show common volume fraction dependency. Between 0 and 50%, the electron and hole mobilities gently decrease. However, when the volume fraction becomes 50% or more, the electron mobility and the hole mobility show a characteristic of sharply decreasing. Therefore, it can be said that the volume fraction of the amorphous silicon portion 33 is desirably between 0 and 50%. At the same time, it can be said from FIGS. 3 and 4 that the volume fraction of crystal fine particle nuclei is desirably between 5 and 95%.

Second Embodiment FIG. 8 shows an apparatus different from the apparatus for manufacturing a fine particle semiconductor film of the first embodiment. The silicon fine-particle powder contained in the fine-particle powder supply chamber 40 is supplied to a plasma melting chamber 42 through a powder supply nozzle 41 together with a carrier gas. The size of the Si fine particles may be selected from a size of 10 nm to 100 μm. He, N is used as a carrier gas.
An inert gas such as e, Ar, Kr, and Xe can be used.

A gas for plasma generation and a source gas are introduced from a gas supply unit 43 into a plasma melting chamber 42 through a gas supply nozzle 44. As the plasma generating gas, an inert gas such as He, Ne, Ar, Kr, and Xe can be used. In the case where an amorphous Si portion is contained in the film, a silicon compound gas such as silane or sidilan may be used as a source gas, and a hydrogen gas may be mixed as necessary.

A high frequency coil 45 for generating a high frequency is provided around the plasma melting chamber 42. The film forming chamber 15 is connected below the plasma melting chamber 42. The substrate 22 is disposed on the susceptor 21 in the film forming chamber 15. An electromagnet 17 is provided outside the film forming chamber 15.

The production of the fine particle semiconductor film in this apparatus will be described. The Si fine particles flowing together with the carrier gas and the plasma generating gas are introduced into the plasma melting chamber 42. Then, a predetermined pressure (for example, 10 to 760)
After adjusting the pressure to Torr, high frequency power (frequency: 1 to 200 MHz, power: 1 to 100 k) is applied to the high frequency coil 45.
W) to generate thermal plasma. The surface of the Si fine particle powder is melted by this thermal plasma. At this time, by adjusting the frequency and electric power, all of the fine particle powder can be melted, or only the vicinity of the surface can be melted. The melted fine particle powder travels toward the substrate 22 along the gas flow and is deposited on the substrate 22.

When a magnetic field is applied to the film-forming chamber 15 on the substrate 22 by the electromagnet 17, the charged Si fine particles can be confined in the space on the substrate, so that the film-forming speed can be improved. I can do it.

It is also possible to use a device in which Si fine particles are supplied to a film forming chamber and the surface of the Si fine particles is melted by a laser. Further, as shown in FIG. 9, as in the first embodiment,
Even if Si fine particles are formed by a CVD method and supplied into a film formation chamber, a fine particle semiconductor film can be formed. Here, the same portions as those in FIGS. 1 and 8 are denoted by the same reference numerals, and description thereof will be omitted. This apparatus can provide microcrystals of a uniform size as compared with a method of supplying Si fine particles.

(Third Embodiment) FIG. 10 is a sectional view of a single cell solar cell according to a third embodiment of the present invention. At a low temperature of 450 ° C. or less, Ti, M
A back electrode 51 made of o, Cr, Al or the like is formed. On the back electrode 51, a p-type fine particle silicon (Si) film 52 having a thickness of about 5 to 1000 μm is formed.
The p-type fine particle Si film 52 is the fine particle semiconductor film described in the first embodiment. On the p-type fine particle Si film 52, 10
N-type microcrystalline silicon (μc-S
i) n of film or n-type amorphous carbide film (a-Si)
A transparent electrode 54 such as ITO is formed via the mold layer 53. The current collecting electrode 5 is partially provided on the transparent electrode 54.
5 are formed. Then, an antireflection film 56 is formed on the transparent electrode 54 and the current collecting electrode 55.

In the formation of the solar cell according to the present embodiment, after forming the p-type fine particle Si film 52, at an appropriate stage, in order to improve the ohmic contact between the p-type fine particle Si film 52 and the back electrode 51, 400 It is desirable that the sintering be performed at a temperature in the range of C to 450C for about 15 minutes.

The light incident from the transparent electrode 54 side causes p
The electrons generated in the type fine particle Si film 52 are diffused to the junction interface with the n-type layer 53, are pushed away by the pn junction electric field, and are extracted from the current collecting electrode 55. On the other hand, the holes generated in the same manner diffuse to the back surface electrode 51 and are taken out as a current.

When the characteristics of the solar cell of this embodiment were measured, a good conversion efficiency of 14% or more was obtained under irradiation with sunlight of AM-1.5 and 100 mW / cm ² . Further, even in a large-area element having an area of 1 m ² or more, a high conversion efficiency of 12% or more could be obtained.

Further, since the solar cell of the present embodiment is mainly made of a crystalline semiconductor, it does not suffer from light deterioration which has been observed in an amorphous silicon solar cell, and has a property of increasing reliability.

(Fourth Embodiment) FIG. 11 shows a fourth embodiment of the present invention.
It is sectional drawing of the solar cell concerning embodiment. Here, FIG.
The same reference numerals are given to the same portions as 0, and the description thereof will be omitted. The feature of this embodiment is that the p-type layer is made of p-type silicon (S
i) A p-type fine particle Si / Ge film 63 composed of crystal fine particles 61 and p-type germanium (Ge) crystal fine particles 62. That is, substances having different band gaps and light absorption wavelength regions are formed in one cell. Further, a metal substrate obtained at low cost is used as the substrate, for example, a stainless steel substrate 60 is used.

The band gaps of Si and Ge are 1.1 eV and 0.67 eV, respectively. Conventional Ge elements are:
Although photoelectric conversion is performed in a wavelength region of about 1.8 μm or less, which is wider than that of the Si element, the recombination loss of carriers due to surface absorption increases, and thus the sensitivity on the short wavelength side (about 1 μm or less) deteriorates. Was. On the other hand, in the structure of this embodiment, the Si fine particles emit short-wavelength light (wavelength
μm or less) can be efficiently photoelectrically converted.
The sensitivity on the short wavelength side can be greatly improved. Therefore, the short-circuit photocurrent can be significantly increased as compared with a conventional structure composed of a single Ge element or Si element. Further, the conventional Ge element has a narrow band gap, so that only a small open-circuit voltage of 0.3 to 0.35 V can be obtained. However, in the present embodiment, the open-circuit voltage increases to about 0.5 V, which is equivalent to that of a Si element, due to the presence of Si fine particles having a band gap larger than that of Ge fine particles.

In the solar cell of this embodiment, a large open-circuit voltage and a large short-circuit photocurrent can be obtained.
A high-performance device having the above (AM-1.5, 100 mW / cm ² ) can be manufactured at low cost.

(Fifth Embodiment) FIG. 12 shows a fifth embodiment of the present invention.
It is sectional drawing of the solar cell concerning embodiment. Here, FIG.
The same reference numerals are given to the same parts as 0 and 11, and the description thereof is omitted. The feature of the solar cell of the present embodiment is that the solar cell is constituted by a tandem cell in which three types of single cells are stacked.

A p-type fine particle Si / Ge film 6 made of Si and Ge is formed on a stainless steel substrate 60 via a back electrode 51.
3 are formed. An n-type layer 53 made of n-type μc-Si or a-Si is formed on a p-type fine particle Si / Ge film 63 to form a first single cell 70. The p-type μc-Si or a-
A second single cell 72 in which an ohmic connection layer 71 made of Si, a p-type Si microcrystalline film 52, and an n-type layer 53 are stacked is formed. On top of this, a p-type ohmic connection layer 71, an i-type amorphous silicon layer 73, an n-type layer 53, a transparent electrode 54, and a current collecting electrode 55
And the third single cell 7 on which the antireflection film 56 is laminated
4 are formed.

Light having a wavelength of about 700 nm or less (a-Si band gap of about 1.7 eV) is emitted from the third single cell 74 in the uppermost layer, and light having a wavelength of about 1.1 μm or less is emitted from the second single cell 72. The light is again applied to the lower first single cell 7.
At 0, light of about 1.8 μm or less is absorbed. The thickness of each layer is determined so that the short-circuit current of each single cell is equal and maximum. The sum of the open voltages of the three cells is the open voltage of this tandem cell. AM-1.5, the conversion efficiency under irradiation of 100 mW / cm ² was an open circuit voltage of 1.8 V or more and a short-circuit photocurrent of 15 mW / cm ^2.
cm ² , indicating a high value of 18% or more.

As described above, since the photoelectric conversion element of the present invention is formed by depositing a crystalline particulate semiconductor film on an arbitrary low-cost substrate at a low temperature, high photoelectric conversion efficiency and low cost can be simultaneously achieved. Can be realized.

The present invention is not limited to the above embodiment. The present invention can be applied to an element including a photoelectric conversion unit other than the solar cell. The fine particle semiconductor film in the semiconductor device of the present invention can be applied to a liquid crystal display using a thin film transistor in addition to a solar cell.

Although the fine particle semiconductor films of Si and Ge have been described, GaAs, AlGaAs, GaSb,
A fine particle semiconductor film made of InP, CdTe, ZnO, CuInSe ₂ or the like may be used.

The fine particle semiconductor film in the solar cells according to the third, fourth and fifth embodiments may include an amorphous semiconductor portion in the film. Further, the n-type layer may be made of a fine particle semiconductor film. In addition, various modifications can be made without departing from the spirit of the present invention.

[0052]

As described above, the semiconductor device of the present invention can provide a high mobility and low defect density film by electrically connecting fine particle crystal nuclei in the fine particle semiconductor film in the device.

According to the method for producing a fine particle semiconductor film of the present invention, a fine particle semiconductor film can be formed by a process at 450 ° C. or lower by supplying semiconductor fine particles, melting the surfaces of the fine particles, and depositing them on a substrate. .

In the photoelectric conversion element of the present invention, a crystalline film can be formed by a low-temperature process by using the above-mentioned fine particle semiconductor film, so that both cost reduction and high efficiency can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the concept of a fine particle semiconductor film manufacturing apparatus according to a first embodiment.

FIG. 2 is a cross-sectional view of the fine particle semiconductor film according to the first embodiment.

FIG. 3 is a characteristic diagram showing a volume fraction dependency of electron mobility of the fine particle semiconductor film of FIG. 2;

FIG. 4 is a characteristic diagram showing a volume fraction dependency of hole mobility of the fine particle semiconductor film of FIG. 2;

FIG. 5 is a sectional view of the particulate semiconductor film according to the first embodiment.

6 is a characteristic diagram showing the dependence of the electron mobility of the fine particle semiconductor film of FIG. 5 on the volume fraction of an amorphous silicon part.

FIG. 7 is a characteristic diagram showing the amorphous silicon volume fraction dependency of the hole mobility of the fine particle semiconductor film of FIG. 5;

FIG. 8 is a schematic view showing the concept of a fine particle semiconductor film manufacturing apparatus according to a second embodiment.

FIG. 9 is a schematic view showing the concept of a fine particle semiconductor film manufacturing apparatus according to a second embodiment.

FIG. 10 is a cross-sectional view showing a single-cell solar cell according to a third embodiment.

FIG. 11 is a sectional view showing a single-cell solar cell according to a fourth embodiment.

FIG. 12 is a sectional view showing a tandem-type solar cell according to a fifth embodiment.

FIG. 13 is a cross-sectional view showing a polycrystalline film formed by conventional laser annealing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Growth chamber 11 ... Source gas supply chamber 12 ... Valve 13 ... Discharge plate 14 ... High frequency power supply 15 ... Film formation chamber 16 ... Orifice 17 ... Electromagnet 18 ... Laser light source 19 ... Cylindrical lens 20 ... Heater 21 ... Bias power supply 22 ... Substrate Reference Signs List 23 bias power supply 24 movable mechanism 26 valve 30 silicon crystal fine particle nucleus 31 polycrystalline silicon part 32 boundary 33 amorphous silicon part 40 fine particle powder supply chamber 41 powder supply nozzle 42 plasma melting chamber 43 gas Supply part 44 ... Gas supply nozzle 45 ... High frequency coil 50 ... Glass substrate 51 ... Back electrode 52 ... P-type fine particle silicon film 53 ... N-type layer 54 ... Transparent electrode 55 ... Current collecting electrode 56 ... Anti-reflection film 60 ... Stainless steel substrate 61 ... p-type silicon crystal fine particles 62 ... p-type germanium crystal fine particles 63 ... p Particulate silicon-germanium film 70 ... first single cell 71 ... ohmic contact layer 72: second single cell 73 ... i-type amorphous silicon layer 74 ... third single-cell

Claims (4)

[Claims] 1. A semiconductor device having a fine particle semiconductor film formed on a substrate, wherein the fine particle semiconductor film comprises a plurality of semiconductor crystal fine particle nuclei discretely laminated on the substrate; A semiconductor device, comprising: a polycrystalline semiconductor portion surrounding at least a part of the fine particle nucleus and electrically connecting an adjacent semiconductor crystal fine particle nucleus. 2. A semiconductor device in which a fine particle semiconductor film is formed on a substrate, wherein the fine particle semiconductor film includes a plurality of semiconductor crystal fine particle nuclei discretely stacked on the substrate; A polycrystalline semiconductor portion surrounding at least a part of the fine particle nucleus and electrically connecting adjacent semiconductor crystal fine particle nuclei; and an amorphous semiconductor portion surrounding at least a part of the polycrystalline semiconductor portion. Semiconductor device. 3. A step of supplying semiconductor crystal fine particles on a surface of a substrate provided for forming a fine particle semiconductor film, and a step of melting the vicinity of the surface of the semiconductor crystal fine particles above the vicinity of the substrate. A method for producing a fine particle semiconductor film, characterized in that: 4. A photoelectric conversion element having a pn junction of a p-type semiconductor and an n-type semiconductor and converting light energy into electric energy, wherein at least one of the p-type semiconductor and the n-type semiconductor is formed of a fine particle semiconductor film. A photoelectric conversion element, comprising: