JPH10209048A - Method of forming semiconductor thin film - Google Patents

Abstract

(57) [Problem] To form a semiconductor thin film constituting a shallow and highly-doped layer suitable for a high-efficiency solar cell, which cannot be obtained by conventional techniques. In a method of forming a semiconductor thin film by a laser ablation method in which a target is irradiated with a laser beam in a vacuum chamber and an emission from the target is deposited on a substrate, a laser is applied to the semiconductor target and a dopant-containing target. By irradiating the beam, a doped semiconductor thin film is formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor thin film by a laser ablation method, and more particularly to a method for forming a semiconductor thin film forming a shallow and highly doped layer suitable for a pn junction of a high efficiency solar cell. About.

[0002]

2. Description of the Related Art In a conventional silicon solar cell, a pn junction is generally formed by forming an n-layer by diffusion of phosphorus (P) or a p-layer by diffusion of boron (B). . For thin film semiconductors, plasma CVD
Generally, a p-layer and an n-layer are formed by a method. In each case,
Since it is a doping method by a chemical reaction, a shallow and high-concentration p-layer / n-layer required for a high-efficiency solar cell cannot be formed.

On the other hand, a high-quality silicon thin film manufacturing technology by a laser ablation method is expected as a technology for practical use of a low-cost, high-efficiency thin-film solar cell or an electronic / optical device such as a thin film transistor (TFT). Also, diamond-like carbon (DLC)
Research is also actively being conducted on thin film, high-temperature superconducting thin film, and ferroelectric thin film forming techniques.

In the formation of a semiconductor thin film by a conventional laser ablation method, p is used as a doping means.
There is a method using a target of type silicon or n-type silicon. P-type silicon and n-type silicon contain boron or phosphorus at the time of manufacturing a silicon crystal. In order to grow a silicon crystal normally, these impurities cannot be contained in large amounts. Using as a target cannot form a highly doped thin film semiconductor.

Japanese Patent Application Laid-Open No. 6-248439 discloses that a substrate is irradiated with an excited nitrogen gas from a pulse nozzle in order to dope a high-concentration p-type impurity into a II-VI compound semiconductor. There is disclosed a technique of alternately performing pulsed laser irradiation on a target made of a constituent element of a group VI compound semiconductor. Although this method is physical doping, the ion beam used for forming the semiconductor cannot irradiate phosphorus or boron.

As described above, in the conventional technique, a shallow, high-concentration doped layer required for realizing a highly efficient solar cell could not be formed.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method of forming a semiconductor thin film forming a shallow and highly doped layer suitable for a high-efficiency solar cell, which was not obtained by the above-mentioned prior art. The purpose is to:

[0008]

In order to achieve the above object, a method of forming a semiconductor thin film according to the present invention comprises irradiating a target with a laser beam in a vacuum chamber, and discharging a substance emitted from the target by the irradiation. In a method for forming a semiconductor thin film by a laser ablation method deposited on a substrate, the semiconductor target and the dopant-containing target are irradiated with a laser beam to form a doped semiconductor thin film on the substrate.

In the laser ablation method, only atoms, molecules, and ions released from a target in a vacuum chamber are used as a film forming material, so that a high-purity thin film with very few impurities can be obtained, and the target composition can be used as it is. There is a feature that is reflected in. Therefore, according to the method of the present invention for irradiating a semiconductor target and a dopant-containing target with a laser beam, a semiconductor thin film of any composition can be formed by changing the timing and time of irradiation on each target. A shallow, high-concentration doped layer required for an efficient solar cell can be easily formed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Semiconductors formed according to the present invention include:
It may be a semiconductor composed of a simple substance such as silicon or a compound semiconductor composed of a plurality of elements. When a single semiconductor thin film made of a single element such as silicon is formed as the semiconductor target, a single target made of the same single element is used.

When a compound semiconductor thin film such as a group III-V compound is formed, (1) a compound target composed of a compound having the same composition as the thin film to be formed, and (2) a compound target having a mixing ratio corresponding to the composition of the thin film to be formed. A mixture target comprising a mixture,
Or (3) a plurality of semiconductor component-containing targets each containing each component of the thin film to be formed. As the dopant-containing target, a target composed of a dopant element or a target composed of a compound containing a dopant element can be used. As the target made of a compound, a target made of a material made of a dopant element and a component having the same composition as the semiconductor to be formed into a film and / or a component which can be removed by gasification during laser ablation treatment can be used. The dopant may be an n-type dopant that forms an n-type doped layer with respect to the semiconductor to be formed, or a p-type dopant that forms a p-type doped layer.

The laser beam irradiation on the semiconductor target and the dopant-containing target may be performed alternately or simultaneously according to the required dopant concentration and its thickness direction distribution. Of course, in the entire laser ablation period, alternate irradiation may be performed during a certain period and simultaneous irradiation may be performed during another period. Similarly,
When a plurality of semiconductor component-containing targets are used as a semiconductor target to form a compound semiconductor thin film, laser beam irradiation can be performed on each of the semiconductor component-containing targets alternately or simultaneously according to a desired compound composition.

In any case, the composition of the thin film including the doping concentration can be arbitrarily changed by controlling the irradiation time to each target. That is, an arbitrary doping concentration and an arbitrary basic composition can be obtained for the entire film thickness, and the doping concentration and the basic composition can be arbitrarily changed along the film thickness direction. The control of the irradiation time to each target can be performed by relatively moving each target and the laser beam.

By using a semiconductor thin film formed by the method of the present invention for a solar cell, a high power generation efficiency which has not been obtained conventionally can be achieved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings. [Embodiment 1] FIG. 1 shows a basic configuration of a laser ablation film forming apparatus for forming a highly doped semiconductor thin film according to the present invention.

In FIG. 1, a laser ablation film forming apparatus 15 is provided with a substrate holder 6 for holding a substrate 5 and a target holder 9 for holding a target 8 in a vacuum chamber 4. The substrate 5 is a substrate holder 6
Is maintained at a predetermined temperature by a heater 7 incorporated in the heater. As the substrate 5, a silicon wafer for manufacturing a semiconductor device and a synthetic quartz substrate were used. The vacuum chamber 4 is
The air is exhausted by a vacuum pump through an exhaust port 13 opened at the lower part.

A pulse laser beam 1 from a laser generator (not shown) provided outside the vacuum chamber 4 is introduced into the vacuum chamber 4 from a laser beam introduction port 3 through a lens system 2. The emission from the target 8 due to the laser beam irradiation is observed as a flame-shaped region, that is, a plume 12, between the substrate 5 and the target 8.
The composition of the thin film during and after formation is a set of RHEED
(Reflection high energy electron diffraction)

For example, a case where a P-doped n-type Si thin film is formed will be described below. As the laser beam 1, an ArF excimer laser beam having a wavelength of 193 nm and a wavelength 2
The irradiation energy is set to 15 to 80 mJ / pulse using a 48 nm KrF excimer laser beam. The target 8 has a configuration in which a Si target 8a and a P-containing target 8b are juxtaposed as shown in FIG. A P-containing target 8b as a source of P as an n-type dopant includes:
For example, those made of P ₃ N ₅ , P ₂ N ₃ , PN, P alone or the like are used. When the Si target 8a and the P-containing target 8b are irradiated with the laser beam 1, Si and P are emitted from the targets 8a and 8b as atoms or ions, respectively, and reach the substrate 5 while forming the plume 12, and 5 to form a thin film. That is, while the Si film is formed on the substrate 5, the P
Is doped, so that a highly P-doped Si thin film is formed.

As the P-containing target 8b, the above P ₃ N
₅ , when P ₂ N ₃ or PN is used, the PN bond is cut by the high energy of the laser, and N is removed as N ₂ molecules (nitrogen gas). Never be. P-doped n-type Si to be formed
The doping concentration and the doping depth of the thin film can be arbitrarily changed by changing the time and timing of laser beam irradiation on the Si target 8a and the P-containing target 8b. Can be easily obtained.

FIG. 2 shows an example of an optical system for controlling the time and timing of laser beam irradiation on each target. The laser light L0 emitted from the laser light source 21 passes through a collimator lens 22 and a cylindrical lens 23, and is reflected by a reflection mirror 24 into a polygon mirror 25.
It is led to. The laser beam L1 radially scanned by the rotation of the polygon mirror 25 passes through the fθ lens 26, and is applied to the targets 8a and 8b as the laser beam L2 in the scan range W via the cylindrical lens 27. The laser beam L2 is scanned in the X direction by the polygon mirror 25 and is irradiated on both of the two targets 8a and 8b. Actually, the laser beam L2 irradiates the two targets alternately. Laser light L
2 is also scanned in the Y direction by the rotation of the cylindrical lens 27, so that a wide range of the target surface is used effectively.

In the optical system shown in FIG.
5, the size and position of the scan range in the X direction are changed, and the targets 8a and 8b are controlled.
The time and timing of laser irradiation on the substrate 5 are changed, thereby changing the deposition rates of Si and P on the substrate 5 and changing the concentration and depth of P doping in the Si thin film. For example, to increase the doping concentration, P
Increasing the irradiation time ratio of the containing target 8b,
Increase the ratio of the P deposition rate to The rotation of the polygon mirror 25 and the cylindrical lens 27
It can be programmed by a computer to obtain the desired doping concentration and doping depth.

In conventional P doping by diffusion, the doping depth (diffusion depth) and the doping concentration (diffusion concentration) were limited to about 0.2 to 1 μm and about 0.02 to 0.2%, respectively. According to the method of the present invention, any doping depth and doping concentration can be set according to the required device characteristics. For example, a doping depth of 0.15 μm and a doping concentration of 0.5% can be easily obtained.

A p-type doped Si thin film can be formed in the same manner. However, in this case, a B-containing target is used as the target 8b. When the p-type dopant is B, B
SiB ₄ or SiB ₆ can be used as the containing target 8b. When the B-containing target 8b is irradiated with a laser, the Si-B bond is broken by the high energy of the laser, and B and Si are released together as atoms, molecules or ions. B is a dopant,
Further, Si becomes a thin film forming material together with Si released from the Si target 8a.

Embodiment 2 According to the present invention, a Si thin-film solar cell 30 having a Si pin structure shown in FIG. 3 is manufactured using the laser ablation film forming apparatus 15 shown in FIG. 1 having the optical system shown in FIG. An example will be described. Transparent glass substrate 3
A transparent electrode 32 (thickness 3000 °) of SnO ₂ is formed on the substrate 1 by a laser ablation method. This is Sn
This is performed using an O ₂ target. The transparent electrode 32 is made of SnO
Instead of ₂ , it may be formed of ITO (Indium Tin Oxide) or the like. The transparent electrode 32 may be formed by a method such as vacuum evaporation or sputtering instead of the laser ablation method. When formed by the laser ablation method, after forming the transparent electrode 32, the Si thin film can be formed in the same apparatus without being taken out of the film forming apparatus.
There is no need to consider contamination outside the film forming apparatus, and no take-out / transport / loading steps are required.

On the SnO ₂ transparent electrode 32, B-doped p-type S
An i-layer 33 is formed to a thickness of 100 °. This is performed by juxtaposing the Si target 8a and the B-containing target 8b such as SiB ₄ and irradiating each target with a laser beam alternately. On the B-doped p-type Si layer 33, a non-doped Si layer 34 is formed to a thickness of 5000 °. This is Si
This is performed by irradiating only the target 8a with a laser.

On the non-doped Si layer 34, a P-doped n-type S
An i-layer 35 is formed to a thickness of 200 °. This is performed by juxtaposing the Si target 8a and the P-containing target 8b such as P ₃ N ₅ and irradiating each target with a laser beam alternately. Al electrode 3 on P-doped n-type Si layer 35
6 is formed to a thickness of 3000 °. The Al electrode 36 may be formed by vacuum deposition or sputtering instead of the laser ablation method, similarly to the above-mentioned SnO ₂ transparent electrode 32.

In the case of a conventional pin type amorphous Si solar cell, a production method by plasma CVD using a silane gas, a phosphine gas, a diborane gas or the like has been generally used. However, as described above, in such a conventional method, p
Increasing the doping concentration of the layer and the n-layer has a limit in principle. According to the method of the present invention, high-concentration doping can be easily achieved by the laser ablation method using the Si target and the dopant-containing target as described above.

In addition, in the conventional production method using plasma CVD, hydrogen is unavoidably mixed into the film, so that there is a disadvantage that light deterioration is apt to occur. According to the method of the present invention, a dopant element alone containing no hydrogen or P ₃ N ₅
Since a film is formed by a laser ablation method under a high vacuum using a dopant element compound such as SiB ₄ or SiB ₄ as a target, hydrogen does not enter the film.

Although omitted in the above description, it is possible to form an anti-reflection film such as SiO ₂ , TiO ₂ , MgO or the like to prevent surface reflection, and to form a pyramid texture by selective etching. Of course you can. The same applies to each structure in the following examples.

[Embodiment 3] According to the present invention, the laser ablation film forming apparatus 15 shown in FIG. 1 equipped with the optical system shown in FIG. 2 was used, and all electrodes were provided on the same side of the substrate as shown in FIG. An example of manufacturing the Si thin film solar cell 40 will be described. Substrate 41 of glass or alumina ceramics
A buffer layer 42 of Si ₃ N ₄ / SiO _x or the like is formed thereon by laser ablation, sputtering, vacuum evaporation, or the like.
To form The provision of the buffer layer 42 prevents impurities from entering the thin film from the substrate 41 and enlarges the crystal grain size of the thin film, thereby ensuring good characteristics.

On top of this, a non-doped Si layer 43 is formed to a thickness of 5 μm by a laser ablation method. The upper surface of the non-doped Si layer 43 is partially masked with a stainless steel plate or the like, and a P-doped n-type Si layer 44 is formed to a thickness of 2000 ° on the unmasked exposed surface. This is performed by juxtaposing the Si target 8a and the P-containing target 8b such as P ₃ N ₅ and irradiating each target with a laser beam alternately.

With the above masking, n-type Si
A transparent electrode 45 such as SnO ₂ or ITO is formed on the layer 44.
(Thickness 3000 mm). This is performed by irradiating a SnO ₂ target or an ITO target with a laser beam. The transparent electrode 45 may be formed by a method such as vacuum evaporation or sputtering. The masking is removed, and instead, the masking is performed while leaving a part of the non-doped Si layer 43 including the region where the n-type Si layer 44 and the transparent electrode 45 are formed.
An Al electrode 46 is formed on the exposed surface by laser ablation or the like.

Embodiment 4 According to the present invention, an example in which a Si thin-film solar cell 50 having the structure shown in FIG. 5 is manufactured using the laser ablation film forming apparatus 15 shown in FIG. 1 equipped with the optical system shown in FIG. explain. The solar cell 50 of FIG.
A high-concentration n ^++- type doped Si thin film 54 is formed on a wafer 53 according to the present invention, and a Ti / P
In this case, a fine electrode 55 of d / Ag is formed. p-type S
On the back surface of the i-wafer 53, an inner Al layer 52 and an outer Ag layer
An Al / Ag electrode composed of the layer 51 is formed. Al
By performing the diffusion process of the layer 52, the p-type Si wafer 5 is formed.
A p ⁺ layer is formed at the interface between the layer 3 and the Al layer 52.

In a conventional single crystal Si solar cell, pn
The junction has been formed by diffusing P (phosphorus) into the p-type Si substrate or diffusing B into the n-type Si substrate. The formation of the n ⁺⁺ layer is performed by using PO on a p-type Si wafer.
Since the diffusion was performed by P vapor using Cl ₃ , there was a limit in increasing the concentration of P dope. According to the present invention, S
A high-concentration n ⁺⁺ layer can be easily formed by a laser ablation method using an i target and a P-containing target.

Further, in the conventional method, since the dopant contained in the substrate itself and the dopant newly doped have a canceling action, the shallow and high-concentration doping required for a high-efficiency solar cell is in principle required. It was difficult. According to the present invention, since there is no offsetting action between such dopants,
Shallow and high-concentration doping becomes possible. Further, conventionally, an interface between the electrode and the substrate Si was controlled by forming an n ⁺⁺ layer immediately below the electrode. However, according to the present invention, as shown in this embodiment, this interface control is more effective. Can be done

In this embodiment, the case where a p-type Si wafer is used has been described.
By forming a heavily doped p-layer by irradiating the target and a target containing a p-type dopant such as B with a laser, a structure similar to that of FIG. 5 can be manufactured. In addition,
In addition to the structure shown in FIG. 5, for example, by selectively forming a high-concentration doped region and a non-doped region using a mask, it is possible to form a Si thin film having a high dopant concentration only immediately below an electrode.

[Embodiment 5] An example in which the band gap of a Si thin film is controlled by controlling the dopant concentration in the Si thin film by the method of the present invention in a Si thin film solar cell will be described. The Si thin film solar cell 60 shown in FIG.
Are a Ti layer 62 and an Ag layer 6 on a stainless steel substrate 61.
3, a ZnO layer 64, an n layer 65, a gradient concentration doped Si thin film 66, a p / i layer (buffer layer) 67, a p layer 68, and an ITO transparent electrode layer 69.

The doping concentration of the gradient-concentration-doped Si thin film 66 is continuously changed in the film thickness direction, so that, for example, as shown in FIG. Is done. Conventionally, as a method of manufacturing a solar cell with a band gap control, for example, C (carbon) or Ge (germanium), which is the same Group 4 element as Si, is added in order to control the band gap of amorphous Si. A method of continuously changing the composition ratio has been used. Therefore, CVD using a mixed gas of a silane-based gas as a Si source and a hydrocarbon-based gas as a C source or a germane-based gas as a Ge source has been performed. In this case, in order to obtain a light absorption region in a wide wavelength range, a tandem structure in which band gap-controlled cells are stacked must be employed.

According to the present invention, when irradiating a laser to an Si target and a dopant-containing target, the irradiation time and / or the irradiation time of each target are changed to thereby increase the thickness direction of the Si thin film to be formed. By continuously changing the dopant concentration, it is possible to easily perform band gap control for continuously changing the band gap of the Si thin film in the film thickness direction. Therefore, the conventional C
It is not necessary to precisely control the flow rate of the source gas for controlling the concentration of the additional element such as Ge or Ge.

In the case of a tandem structure as in the prior art, the number of manufacturing steps and the amount of additives generally increase as the number of layers increases, so that not only the manufacturing process becomes complicated and the manufacturing cost increases, but also the film quality deteriorates. As a result, there is a problem that the actual conversion efficiency is not improved as expected as a result of the lamination. According to the present invention, since the band gap can be easily controlled in a wide range even though it is a single layer, it is possible to produce a low-cost and high-efficiency thin-film solar cell without such a conventional problem. There are great benefits.

The present invention does not specifically exclude a tandem structure. If an increase in manufacturing cost and a decrease in film quality due to lamination can be neglected, it is possible to further increase the conversion efficiency by adopting a tandem structure. Needless to say. FIG. 8 shows an example in which a tandem structure is formed according to the present invention.
Shown in The thin-film solar cell 80 includes a gradient concentration-doped Si layer 66, a lower n-layer 65, and an upper p / i layer 67 of FIG.
And a p-layer 68, three units of which are laminated, and an ITO transparent electrode layer 69 is formed on the uppermost layer to form a tandem structure. Here, the upper, middle, and lower three graded-concentration doped Si layers 66 shown in FIG. 8 can have a large, medium, and small band gap.

Embodiment 6 As described above, in the method of the present invention, the semiconductor target and the dopant-containing target are alternately or simultaneously irradiated with a laser beam to control the laser irradiation time on each target. Any doping concentration can be obtained. When a plurality of semiconductor component-containing targets are used as a semiconductor target to form a compound semiconductor thin film, an arbitrary composition is obtained for the plurality of semiconductor component-containing targets also by controlling irradiation time by alternate irradiation or simultaneous irradiation. be able to.

The irradiation time for each target can be controlled by relatively moving the target and the laser beam. Specifically, the laser beam is scanned as described with reference to FIG. 2, or each target is rotated or moved. FIG. 9 shows a structural example of an apparatus for rotating or moving a target in order to alternately irradiate a plurality of targets with a laser beam.

In the example shown in FIG. 9A, four different targets 92a and 92
The targets b, 92c, and 92d are arranged on the disk-shaped target holder 93 with a space between the targets, and are rotated in the direction of the arrow, so that the targets are sequentially and alternately irradiated.
For example, when forming an S-doped n-type InGaAs thin film, each target is an In target 92a, a Ga target 92b, an As target 92c, and an S target 92d.
It can be. In this apparatus, a continuous wave laser is not suitable because the holder is exposed between different kinds of targets. When the exposed part of the holder comes to a position where it meets the laser beam, it is necessary to stop the laser oscillation. For that purpose, it is necessary to control the rotation of the target holder and the timing of laser oscillation by using a pulse laser, a pulse motor for rotating the target holder, a pulse controller and a computer in combination.

In the example of FIG. 9B, the three different targets 92a, 92b, and 92c are arranged on the target holder 93 adjacent to each other without being separated from each other. It is not necessary to control the rotation of the target holder and the timing of laser oscillation, and a continuous wave laser can be used. Fig. 9 (c)
In the example of the above, nine different holders 92a to 92i are arranged on the square target holder 93 so as to be adjacent to each other without being separated from each other, and the holder 93 is moved in the xy directions. The target can be irradiated for an arbitrary time. The xy movement and the laser oscillation are controlled so as to skip a target that does not require irradiation during the movement.

In any of FIGS. 9A to 9C, the irradiation order for each target is determined according to the doping concentration and composition of the thin film to be formed and their distribution in the thickness direction (concentration gradient and composition gradient). It is desirable to control the computer and the irradiation time by a preset program.

Embodiment 7 FIG. 10 shows an example of an apparatus for simultaneously irradiating a plurality of targets with a laser beam. In the illustrated apparatus, the incident laser beam 101 is split into two laser beams 101a and 101b by a beam splitter 103, and the beam 10
Reference numeral 1a denotes a beam from the splitter 103 via a reflecting mirror 104, and a beam 101b is directly irradiated from the splitter 103 to different targets 102a and 102b. Although the figure shows a case where two types of targets are used, the same irradiation can be performed similarly when three or more types of targets are used.

When simultaneously irradiating a plurality of targets,
The composition of the formed thin film depends on the amount of a substance emitted from each target material by laser beam irradiation. In order to control the composition as desired, an optical switch or a chopper is provided in the optical path of the laser beam after branching, and the time for interrupting the optical path is controlled according to the required composition ratio. As described above, when a compound target or a mixture target is used as a semiconductor target, a target having the same composition or mixture ratio as the composition of the thin film to be formed is prepared in advance, and a single laser beam is applied to the target.

[0049]

As described above, according to the present invention,
By irradiating a semiconductor target and a dopant-containing target with a laser beam, it is possible to form a semiconductor thin film that constitutes a shallow and highly-doped layer required for a high-efficiency solar cell, which cannot be obtained by conventional techniques. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a basic configuration of a laser ablation film forming apparatus for forming a highly doped semiconductor thin film according to the present invention.

FIG. 2 is a layout diagram showing an example of an optical system for controlling the time and timing of laser beam irradiation on each target according to the present invention.

FIG. 3 is a cross-sectional view showing a solar cell having a Si pin structure manufactured according to the present invention.

FIG. 4 is a cross-sectional view showing a solar cell having a structure in which electrodes are provided on the same side of a substrate manufactured according to the present invention.

FIG. 5 is a cross-sectional view showing a solar cell manufactured according to the present invention and having a fine electrode as a surface current collecting electrode.

FIG. 6 is a cross-sectional view showing a solar cell having a gradient-doped Si thin film formed according to the present invention.

FIG. 7 is a schematic diagram showing a band gap obtained by the gradient concentration doping of FIG. 6;

FIG. 8 illustrates the graded doping S of FIG. 6 in accordance with the present invention.
It is sectional drawing which shows the solar cell of a tandem structure which laminated | stacked three units of structural units containing an i layer.

FIG. 9 is a schematic view showing an example of an apparatus for rotating or moving a target in order to alternately irradiate a plurality of targets with a laser beam according to the present invention.

FIG. 10 is a schematic view showing an example of an apparatus for simultaneously irradiating a plurality of targets with a laser beam according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pulse laser beam 2 ... Lens system 3 ... Laser beam introduction port 4 ... Vacuum chamber 5 ... Substrate 6 ... Substrate holder 7 ... Built-in heater 8 ... Target 8a ... Si target 8b ... P containing target or B containing target 9 ... Target holder 10, 11 ... RHEED (reflection high energy electron diffraction)
Apparatus 12 Plume of emission from target 8 13 Exhaust port 15 Laser ablation film forming apparatus 21 Laser light source L0, L1, L2 Laser light 22 Collimator lens 23 Cylindrical lens 24 Reflecting mirror 25 Polygon mirror 26 f-lens 27 cylindrical lens 30 Si thin-film solar cell 31 transparent glass substrate 32 SnO ₂ transparent electrode 33 B-doped p-type Si layer 34 non-doped Si layer 35 P-doped n-type Si layer 36 ... Al electrodes 40 substrate 42 ... Si such as Si thin-film solar cell 41 ... glass or alumina ceramics ₃ n ₄ / SiO _x buffer layer, such as 43 ... non-doped Si layer 44 ... P-doped n-type Si layer 45 ... SnO ₂ or Transparent electrode such as ITO 46 ... Al electrode 50 ... Si thin film type Positive battery 51: Ag layer 52: Al layer 53: p-type Si wafer 54: high-concentration n ^++- type doped Si thin film 55: fine electrode of Ti / Pd / Ag (surface collecting electrode) 60: Si thin-film solar cell 61 ... Stainless steel substrate 62 ... Ti layer 63 ... Ag layer 63 64 ... ZnO layer 65 ... n layer 66 ... gradient concentration doped Si thin film 67 ... p / i layer (buffer layer) 68 ... p layer 69 ... ITO transparent electrode layer 91 ... Laser beams 92a, 92b, 92c, 92d, 92e, 92f, 9
2g, 92h, 92i: Different target 93: Target holder 101: Incident laser beam 101a, 101b: Branched laser beam 102a, 102b: Different target 103: Beam splitter 104: Reflecting mirror

Claims (6)

[Claims] In a method for forming a semiconductor thin film by a laser ablation method, in which a target is irradiated with a laser beam in a vacuum chamber and an emission from the target is deposited on a substrate, the semiconductor target and the dopant-containing target are irradiated with a laser beam. A method for forming a semiconductor thin film, comprising forming a doped semiconductor thin film on a substrate by irradiating a laser beam. 2. The method according to claim 1, wherein the semiconductor target and the dopant-containing target are alternately or simultaneously irradiated with a laser beam. 3. The method according to claim 1, wherein the dopant is an n-type dopant or a p-type dopant. 4. The method of forming a semiconductor thin film according to claim 1, wherein the composition of the thin film is arbitrarily changed by controlling the irradiation time to each of the targets. 5. The method according to claim 4, wherein the target and the laser beam are relatively moved to control the irradiation time on each of the targets. 6. A solar cell using a semiconductor thin film formed by the method according to claim 1. Description: