JP4346699B2 - Method for manufacturing photoelectric conversion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a photoelectric conversion device typified by a solar cell or an image input sensor.
[0002]
[Prior art]
An amorphous silicon film can be produced in a large area at a low temperature of 400 ° C. or lower as compared with a crystalline silicon material, and a thickness of about 1 μm necessary for absorbing light as a photoelectric conversion layer is sufficient. It is characterized by being. For this reason, it has been suggested that silicon resources can be saved and manufacturing energy can be reduced, and has been attracting attention as a low-cost material.
[0003]
In conventional techniques, a photoelectric conversion layer such as a solar cell, an image sensor, or a photosensor generally uses a diode-type structure in which a pin junction is formed in order to increase photoelectric conversion efficiency and photoresponsiveness. . Here, it is possible to form all of the p-type and n-type semiconductor films and the substantially intrinsic i-type semiconductor film with an amorphous silicon film, but in order to obtain good photoelectric conversion characteristics. It has been known that good photoelectric conversion characteristics can be obtained by using a microcrystalline silicon material for p-type and n-type semiconductor films. This is because, in an element having this structure, the i-type amorphous silicon film is responsible for light absorption and the accompanying charge generation, and therefore it is desirable that the p-type and n-type semiconductor films have high light transmittance, and This is because a material having high conductivity is required to obtain a good contact with the electrode. In response to such a demand, the microcrystalline silicon film is a suitable material because it has a characteristic that combines low light absorption and high electrical conductivity.
[0004]
The amorphous silicon film is produced by a chemical deposition method (plasma CVD method) using glow discharge plasma under reduced pressure. In the plasma CVD method, a reaction chamber, an exhaust means for keeping the reaction chamber under reduced pressure, a gas introduction means for introducing a source gas, a means for generating glow discharge plasma in the reaction chamber, and a means for holding and heating the substrate Is used. The source gas is silane (SiH _Four ) Gas is usually used, but disilane (Si ₂ H ₆ ) Gas may be used, and the source gas may be hydrogen gas (H ₂ It was also possible to use after diluting with).
[0005]
On the other hand, the microcrystalline silicon film uses SiH as a source gas. _Four Gas and H ₂ A mixed gas with gas is used, and SiH _Four H against gas ₂ It was possible to obtain a film with an increased gas dilution ratio. A microcrystalline silicon film to which no p-type or n-type conductivity-determining impurity element is added is known to exhibit n-type conductivity by itself, but usually has a p-type or n-type conductivity type. For control purposes, the source gas is prepared by simultaneously adding an impurity gas containing p-type and n-type conductivity determining elements during film formation. In the field of semiconductors, p-type conductivity determining elements include elements represented by boron (B), aluminum (Al), gallium (Ga), and indium (In), and n-type conductivity determining elements. For example, elements represented by phosphorus (P), arsenic (As), and antimony (Sb) are known. In the normal plasma CVD method, B ₂ H ₆ And PH _Three The film is formed by mixing an impurity gas represented by The amount of impurity gas added at this time is SiH. _Four The concentration was about 0.1% to 5%, and at most 10% or less.
[0006]
[Problems to be solved by the invention]
The basic process of a photoelectric conversion device such as a solar cell or an image sensor manufactured on a substrate is to form a first electrode on the substrate and to make a photoelectric conversion consisting of a pin junction in close contact with the first electrode. A layer is formed, and further a second electrode is stacked. In producing a pin junction, in order to improve the characteristics of the junction interface, film formation is usually performed without turning off the vacuum.
[0007]
At this time, when the impurity gas is added to the source gas in order to form a p-type or n-type semiconductor film, a very small amount of the impurity gas and its reaction product are generated in the reaction chamber or in the glow discharge plasma generating means. It has been known that the residual electrode adheres to the discharge electrode. Here, when a substantially intrinsic i-type amorphous silicon film is formed continuously without adding impurity gas in the same reaction chamber, the residual impurities are detached and newly taken into the film. There was a problem that would be lost. A substantially intrinsic i-type amorphous silicon film has a defect density of about 1 × 10 6 in the film. ¹⁶ / Cm ^Three Since it is fabricated to have the following values, there is a problem that even if the impurity element is incorporated at a concentration of several tens of ppm to several hundreds of ppm, the order of impurities is formed to change the film characteristics. .
[0008]
To solve such a problem, a multi-chamber separation type CVD apparatus in which a plurality of reaction chambers are provided in a plasma CVD apparatus, and each reaction chamber is separated by a gate valve between the reaction chamber and another reaction chamber. Has been devised. Therefore, according to the prior art, in order to form a pin junction, it is necessary to provide at least three independent reaction chambers for forming p-type, i-type, and n-type semiconductor films.
[0009]
As a result, the plasma CVD apparatus corresponds to each reaction chamber with SiH. _Four , H ₂ , B ₂ H ₆ , PH _Three It is necessary to provide gas introducing means, exhaust means, glow discharge plasma generating means, etc. for introducing the gas, etc., resulting in a complicated and large-scale configuration. Therefore, a great amount of labor has been required from the aspect of maintenance and management of the apparatus.
[0010]
Further, from the viewpoint of the process, every time a semiconductor film of one conductivity type is formed, the steps of moving the substrate from one reaction chamber to another reaction chamber, introducing the reaction gas, and exhausting the reaction gas It was necessary to repeat this process sequentially. Therefore, shortening the time for forming the photoelectric conversion layer is naturally limited. Even if the actual film formation time is shortened by using the high-speed film formation technique, the time required for transporting the substrate and introducing and exhausting the gas has been a problem that cannot be ignored.
[0011]
Further, in the technical field of conventional solar cells, a method for improving the bonding property by continuously changing the p-type impurity concentration at the p / i interface of the photoelectric conversion layer to form the interface continuity is known. It has been. In the prior art, it is necessary to precisely control a gas containing a small amount of a p-type impurity element using a computer or the like in a film forming process.
[0012]
[Means for Solving the Problems]
As a means for solving the above problems, the present invention separates the step of forming the amorphous semiconductor layer and the microcrystalline semiconductor layer from the step of controlling the conductivity type by adding impurities to the microcrystalline semiconductor layer. A method for forming a photoelectric conversion layer is disclosed.
[0013]
The present invention does not add a p-type or n-type conductivity-determining impurity element in close contact with the first electrode in order to increase productivity in a photoelectric conversion layer manufacturing process typified by plasma CVD. A step of forming a photoelectric conversion layer made of the first and second microcrystalline semiconductor films manufactured in step 1 and a substantially intrinsic amorphous semiconductor film, and a second layer in close contact with the photoelectric conversion layer. A step of forming an electrode; and a step of injecting a p-type conductivity-determining impurity element into the microcrystalline semiconductor film from the surface of the second electrode and heating.
[0014]
According to the invention, a photoelectric conversion layer including the first microcrystalline semiconductor film, the substantially intrinsic amorphous semiconductor film, and the second microcrystalline semiconductor film is formed, and the second microcrystalline semiconductor film is formed. From the surface of the second electrode provided in close contact with the microcrystalline semiconductor film, the interface between the second microcrystalline silicon film and the second microcrystalline silicon film of a substantially intrinsic amorphous silicon film A photoelectric conversion device is manufactured by injecting a P-type conductivity-determining impurity element in the vicinity and heating.
[0015]
In addition, according to the present invention, the first and second microcrystalline semiconductor films formed without adding a p-type or n-type conductivity-determining impurity element to prevent impurity gas contamination by the plasma CVD method. On the other hand, the first microcrystalline semiconductor film and the second microcrystalline semiconductor film into which the p-type conductivity-determining impurity element has been implanted have p-type and n-type conductivity by heating. A microcrystalline semiconductor film is obtained and a photoelectric conversion layer is manufactured.
[0016]
In the present invention, it is the most desirable embodiment that a microcrystalline silicon film is applied to the microcrystalline semiconductor film and an amorphous silicon film is applied to the amorphous semiconductor film. As the amorphous semiconductor film, an amorphous silicon carbide film, an amorphous silicon germanium film, or an amorphous silicon tin film can be applied.
[0017]
As a method for injecting the p-type conductivity determining impurity element from the surface of the second electrode, an ion doping method is an example of a preferred embodiment of the present invention.
[0018]
[Action]
According to the present invention, it is not necessary to add a p-type or n-type conductivity-determining impurity element to the conventional step of forming p-type and n-type microcrystalline semiconductor films. This is because it is not necessary to consider the contamination due to the impurities in the step of forming the p-type and n-type microcrystalline semiconductor films and the substantially intrinsic i-type amorphous semiconductor film. It is also possible to form a film continuously in the film formation chamber. Specifically, the p-type and n-type microcrystalline silicon films and the substantially intrinsic amorphous silicon film are SiH. _Four Gas or Si ₂ H ₆ Gas and H ₂ Since it is produced only from gas, it can be formed by the same glow discharge plasma generating means provided in the same reaction chamber. Further, it becomes possible to continuously produce p-type and n-type microcrystalline silicon films and substantially intrinsic amorphous silicon films while maintaining glow discharge plasma.
[0019]
Further, according to the present invention, there is no need to introduce an impurity gas in the step of forming a p-type and n-type microcrystalline semiconductor film and a substantially intrinsic i-type amorphous semiconductor film. Since the influence of impurity contamination in the apparatus is reduced, the number of reaction chambers is substantially one, and the configuration of the plasma CVD apparatus can be simplified.
[0020]
Therefore, according to the present invention, a step of forming a first microcrystalline semiconductor film, a step of forming a substantially intrinsic amorphous semiconductor film, a step of forming a second microcrystalline semiconductor film, A step of implanting a p-type determining impurity element into the second microcrystalline semiconductor film, and a step of heating the first and second microcrystalline semiconductor films and the substantially intrinsic amorphous semiconductor film, A microcrystalline semiconductor film exhibiting n-type conductivity and a substantially intrinsic amorphous semiconductor film can be obtained, and a pin junction can be formed. A microcrystalline silicon film to which no p-type or n-type conductivity determining impurity element is added exhibits n-type conductivity by itself. It has been found that even when a pin junction is formed using this n-type conductive microcrystalline silicon film as the first microcrystalline semiconductor film, a good photoelectric conversion layer can be obtained. Therefore, it is not necessary to use the conventional n-type impurity element.
[0021]
In a preferred embodiment of the present invention, the first and second microcrystalline silicon films and the substantially intrinsic amorphous silicon film are SiH. _Four Gas and H ₂ Since it can be produced from gas, it is not always necessary to switch the gas when producing each film. Therefore, the time required for the movement of the substrate from the reaction chamber to the reaction chamber and the introduction and exhaust of gas as required in the conventional process becomes unnecessary, and the process throughput can be improved.
[0022]
Further, according to the present invention, the p-type and n-type microcrystalline silicon films and the substantially intrinsic amorphous silicon film are simultaneously formed in each reaction chamber of a plasma CVD apparatus having a plurality of reaction chambers. Alternatively, each can be manufactured, and process throughput can be improved.
[0023]
Further, by implanting a p-type conductivity-determining impurity element from the surface of the second microcrystalline semiconductor film using an ion doping method, the concentration distribution in the film thickness direction of the p-type impurity can be easily controlled. it can.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
[0025]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.
[0026]
[Example 1]
An example of an embodiment according to the present invention will be described according to the steps of the solar cell shown in FIG. The substrate 101 may be made of a material having a flattened insulating surface and a heat resistance temperature of about 450 ° C. at the maximum. Here, a commercially available alkali-free glass was used.
[0027]
A first electrode is formed on the surface of the substrate 101. The first electrode 102 was formed using a known method typified by a vacuum evaporation method or a sputtering method. The material used for the first electrode 102 may be a light-reflective metal electrode selected from Al, Ag, Ti, Cr, Ni, and Pt. A necessary film thickness is about 100 nm to 300 nm, but even a thickness outside this range is not related to the constituent elements of the present invention. Here, Ti was formed to a thickness of 250 nm by sputtering. (Fig. 1 (a))
[0028]
Next, a step of forming a microcrystalline silicon film and an amorphous silicon film to be a photoelectric conversion layer on the surface of the first electrode 102 was performed. The first microcrystalline silicon film 103, the substantially intrinsic amorphous silicon film 104, the p-type or n-type conductivity-determining impurity element without adding the p-type or n-type conductivity-determining impurity element The second microcrystalline silicon film 105a was formed by plasma CVD without adding. (Fig. 1 (b))
[0029]
FIG. 2 is a conceptual diagram of a single wafer plasma CVD apparatus used in this embodiment. The plasma CVD apparatus may have a structure according to the prior art, and includes a substrate carry-in / carry-in chamber 202 and a plurality of reaction chambers 203a, 203b, and 203c centered on a substrate transfer chamber 201, and each reaction chamber has a plasma generating means 204. Is provided. Although not shown, each reaction chamber is provided with an exhaust means for keeping the reaction chamber under reduced pressure and a means for holding and heating the substrate. According to the present invention, the first and second microcrystalline silicon layers and the substantially intrinsic amorphous silicon layer are SiH. _Four Gas and H ₂ Since only two types of gas need be supplied, the same discharge means can be used in the same reaction chamber. Therefore, when the single-wafer plasma CVD apparatus having the conventional structure shown in FIG. 2 is used, the same film formation can be performed in each of the plurality of reaction chambers.
[0030]
Although not used in this embodiment, an in-line type plasma CVD apparatus having a configuration in which a substrate loading / unloading chamber and one or a plurality of reaction chambers are connected in series may be used.
[0031]
In this step, the first microcrystalline silicon film 103 and the second microcrystalline silicon film 105a formed without adding the p-type or n-type conductivity determining impurity element were formed under the same conditions. Specifically, SiH _Four Flow rate 2sccm, H ₂ The flow rate is 200 sccm, the pressure is kept at 133 Pa, and 120 mW / cm. ² Of RF (13.56 MHz) was applied to form a film. At this time, the substrate temperature was kept at 160 ° C. The conditions for forming the microcrystalline silicon film are basically known techniques and are not limited to the above film forming conditions. The range of applicable film formation conditions is SiH. _Four : H ₂ = 1: 30 to 100, pressure 5 to 266 Pa, RF power density 10 to 250 mW / cm ² The substrate temperature is 80 to 300 ° C. The first microcrystalline silicon film 103 may be deposited in the range of 10 to 80 nm, and the second microcrystalline silicon film 105a may be deposited in the range of 5 to 50 nm. In this embodiment, the first microcrystalline silicon film 103 is formed. 103 was set to 30 nm, and the second microcrystalline silicon film 105a was set to 25 nm.
[0032]
The substantially intrinsic amorphous silicon film 104 is made of SiH. _Four Flow rate 40sccm, H ₂ The flow rate is 360 sccm, the pressure is kept at 133 Pa, and 48 mW / cm. ² Of RF (13.56 MHz) was applied to form a film. At this time, the substrate temperature was kept at 160 ° C. The film formation conditions for the amorphous silicon film are basically known techniques and are not limited to the above film formation conditions. The range of applicable film formation conditions is SiH. _Four H for gas ₂ The gas ratio may be selected in the range of 0% to 95%, pressure 5 to 266 Pa, RF power density 5 to 100 mW / cm. ² The substrate temperature is 80 to 350 ° C. The deposited film thickness is desirably in the range of 100 to 2000 nm, and in this example, the film was formed with a thickness of 1000 nm.
[0033]
Also, instead of a substantially intrinsic amorphous silicon film, SiH _Four In addition to gas, carbon (C), germanium (Ge), tin (Sn) hydride, fluoride, chloride gas is introduced to form amorphous silicon carbide film, amorphous silicon germanium film It is also possible to form an amorphous silicon tin film.
[0034]
After the above steps, an integration processing step of dividing the photoelectric conversion layer and the electrode in the same substrate plane and connecting them in series was performed. The integration process is performed by a known technique, and includes a step of forming a hole in the photoelectric conversion layer and the electrode by a laser scribe method and a step of forming an insulating resin by a screen printing method. Matters relating to the design of the integration process are according to known examples and will not be described in detail here.
[0035]
The first openings 107a and 107b are insulating separation openings formed in the photoelectric conversion layer and the first electrode, and these openings form a plurality of unit cells on the same substrate surface. Is for the purpose. The second openings 108a and 108b are provided adjacent to the first openings 107a and 107b, respectively, for connecting the adjacent first electrode and the second electrode. The opening was formed by a laser scribing method. (Fig. 1 (c))
[0036]
After forming the first opening and the second opening, an insulating resin was printed by a screen printing method. As the insulating resin, first insulating resin regions 109a and 109b and second insulating resin regions 111a and 111b were formed. The first insulating resin regions 109a and 109b are formed on and filling the first openings 107a and 107b, and the second insulating resin regions 111a and 111b are formed as the second openings 108a and 108b. Is provided adjacent to. A commercially available insulating resin may be used, but an acrylic or urethane resin is desirable and can be fired at about 200 ° C. The thickness of the insulating resin is not particularly limited, but here it is 20 μm thick. (Fig. 1 (d))
[0037]
The second electrode 106 was formed so as to cover the second microcrystalline silicon film 105a, the first insulating resin regions 109a and 109b, and the second insulating resin regions 111a and 111b. The second electrode 106 is a transparent electrode, and a known method typified by a vacuum evaporation method or a sputtering method may be used. Specifically, In ₂ O _Three , SnO ₂ ZnO, ITO film, or the like may be used. Here, the ITO film is formed by sputtering to a thickness of 70 nm. (Fig. 1 (e))
[0038]
The third openings 112a and 112b that divide the second electrode 106 into the respective unit cells were formed on the second insulating resin region by a laser scribing method adjacent to the second openings. (Fig. 1 (f))
[0039]
Since the second electrode 106 has a relatively high resistivity, it is more desirable to form the auxiliary electrode 113. The auxiliary electrodes 113a and 113b are provided in close contact with the second electrode 106 and are formed so as to cover the second openings 108a and 108b. The auxiliary electrode is formed of a highly conductive metal material, and here, silver (Ag) is formed in a comb shape by a screen printing method. (Fig. 1 (f))
[0040]
After the above steps, p-type conductivity determining impurities are introduced from the surface of the second electrode into the second microcrystalline silicon film 105a by ion doping to form the p-type microcrystalline silicon film 105b. The process to do was performed. Impurities that can be controlled to valence electrons in the p-type with respect to the microcrystalline silicon film include elements of Group IIIb of the periodic table such as boron (B), aluminum (Al), gallium (Ga), and indium (In) It ’s fine. In the ion doping method, a gas such as a hydride, chloride, or fluoride of the impurity element is turned into plasma, the generated impurity element is ionized, and an electric field is applied in a direction to accelerate the substrate, thereby applying an electric field to the substrate. It is a method of injection. In this embodiment, B ₂ H ₆ Gas was used. The dose is 2.0 × 10 ¹³ ~ 5.0 × 10 ¹⁵ / Cm ² In this case, 1.0 × 10 ¹⁴ / Cm ² It was. (Fig. 1 (g))
[0041]
In the ion doping method, the implanted element has a concentration distribution in the depth direction depending on the acceleration voltage, and it is necessary to appropriately adjust this value. In the case of a solar cell, although the optimum conditions differ depending on the thickness of the p-type layer, the acceleration voltage was set in the range of 5 to 25 keV. In this embodiment, it was set to 15 keV. Dose amount 1.0 × 10 ¹⁴ / Cm ² When B is implanted under the condition of an acceleration voltage of 10 keV, the concentration of B implanted into the film is examined by secondary ion mass spectrometry, and the concentration at the peak position is 5 × 10 5. ¹⁹ / Cm ^Three Concentration was obtained.
[0042]
Further, the acceleration voltage is increased, and the p-type impurity element is implanted into a region in the vicinity of the interface between the second microcrystalline silicon film and the second microcrystalline silicon film of a substantially intrinsic amorphous silicon film. You may do it. In the technical field of solar cells, a method for improving the junction characteristics of an interface by continuously changing the p-type impurity concentration at the p / i interface is a conventionally known technique. In the prior art, in the film formation process, it was necessary to precisely control a gas containing a small amount of p-type impurity element using a computer or the like. According to the present invention, in the ion doping process, Since only the accelerating voltage needs to be controlled, the film thickness direction of the impurity concentration at this interface and in the vicinity thereof can be controlled more precisely.
[0043]
Since the implanted B element does not act as a p-type impurity element as it is, an activation step by heat treatment is required. The heat treatment step may be performed in an air atmosphere, a nitrogen atmosphere, or a hydrogen atmosphere, and the temperature may be in the range of 200 to 450 ° C., and preferably in the range of 300 to 400 ° C. Here, heat treatment was performed at 300 ° C. for 2 hours. (Fig. 1 (h))
[0044]
The change in conductivity due to the heat treatment of the microcrystalline silicon film has been confirmed in advance by experiments. The result is shown in FIG. SiH _Four Gas and H ₂ The conductivity after forming the microcrystalline silicon film made from the gas is about 5 × 10 ^-Four Although it was S / cm, the conductivity could be increased by injecting and heating p-type impurities as in the configuration of the present invention. Conductivity is 2 to 3 × 10 by heat treatment at 300 ° C. ^-0 It was confirmed that it increased to S / cm. Further, when the microcrystalline silicon film not implanted with any impurity element is similarly heated, the conductivity is about 1.1 × 10 10. ^-2 It was confirmed that it increased to S / cm. It was also confirmed that the microcrystalline silicon film into which no impurity element was implanted had n-type conductivity.
[0045]
Through the above steps, a photoelectric conversion layer including the first n-type microcrystalline silicon film, the substantially intrinsic amorphous silicon film, and the second p-type microcrystalline silicon film can be formed. It was.
[0046]
Through the above steps, a solar cell in which a plurality of unit cells 110a, 110b, 110c were connected in series could be manufactured. The method for manufacturing a solar cell shown in this example includes a step of forming a first electrode, a step of forming a first microcrystalline silicon film, a step of forming a substantially intrinsic amorphous silicon film, A step of forming a second microcrystalline silicon film, a step of implanting a P-type determining impurity element into the second microcrystalline silicon film, and an amorphous silicon film substantially intrinsic to the first and second microcrystalline silicon films. A step of forming a second electrode, and a step of patterning the first or second electrode by a known method and arranging them at predetermined positions on the surface of the substrate. It can be applied to the production of serial connection structures, image sensors, and photosensors.
[0047]
[Example 2]
Another example of the embodiment according to the present invention will be described according to the process of the solar cell shown in FIG. The substrate 101 may be made of a material having a flattened insulating surface and a heat resistance temperature of about 450 ° C. at the maximum. Here, a commercially available alkali-free glass was used.
[0048]
A first electrode is formed on the surface of the substrate 101. The first electrode 102 was formed using a known method typified by a vacuum evaporation method or a sputtering method. The material used for the first electrode 102 may be a light-reflective metal electrode selected from Al, Ag, Ti, Cr, Ni, and Pt. A necessary film thickness is about 100 nm to 300 nm, but even a thickness outside this range is not related to the constituent elements of the present invention. Here, Ti was formed to a thickness of 300 nm by a sputtering method. (Fig. 1 (a))
[0049]
Next, a step of forming a microcrystalline silicon layer and an amorphous silicon layer to be a photoelectric conversion layer on the surface of the first electrode 102 was performed. The first microcrystalline silicon film 103, the substantially intrinsic amorphous silicon film 104, the p-type or n-type conductivity-determining impurity element without adding the p-type or n-type conductivity-determining impurity element The second microcrystalline silicon film 105a was formed by plasma CVD without adding. (Fig. 1 (b))
[0050]
FIG. 2 is a conceptual diagram of a single wafer plasma CVD apparatus used in this embodiment. The plasma CVD apparatus may have a structure according to the prior art, and includes a substrate carry-in / carry-in chamber 202 and a plurality of reaction chambers 203a, 203b, 203c, centering on a substrate transfer chamber 201, and each reaction chamber has plasma generating means 204. Is provided. Although not shown, each reaction chamber is provided with a substrate heating means, and the configuration of other exhaust means and the like is in accordance with the prior art. According to the present invention, the first and second microcrystalline silicon layers and the substantially intrinsic amorphous silicon layer are SiH. _Four Gas and H ₂ Since only two types of gas need be supplied, the same discharge means can be used in the same reaction chamber. Therefore, when the single-wafer plasma CVD apparatus having the conventional structure shown in FIG. 2 is used, the same film formation can be performed in each of the plurality of reaction chambers.
[0051]
Although not used in this embodiment, an in-line type plasma CVD apparatus having a configuration in which a substrate loading / unloading chamber and one or a plurality of reaction chambers are connected in series may be used.
[0052]
According to the present invention, the first microcrystalline silicon film 103, the substantially intrinsic amorphous silicon film 104, and the second microcrystalline silicon film 105a are the same SiH. _Four Gas and H ₂ Since it can be produced from the gas in the same reaction chamber, continuous film formation is possible only by changing the conditions during film formation as appropriate. Specifically, the gas mixture ratio, discharge power, and reaction gas pressure may be adjusted.
[0053]
In this step, the first microcrystalline silicon film 103 formed without adding the p-type or n-type conductivity determining impurity element and the second microcrystalline silicon film 105a were formed under the same conditions. Specifically, SiH _Four Flow rate 4sccm, H ₂ The flow rate is 400 sccm, the pressure is kept at 133 Pa, and 120 mW / cm. ² Of RF (13.56 MHz) was applied to form a film. At this time, the substrate temperature was kept at 160 ° C. The conditions for forming the microcrystalline silicon film are basically known techniques and are not limited to the above film forming conditions. The range of applicable film formation conditions is SiH. _Four : H ₂ = 1: 30 to 100, pressure 5 to 266 Pa, RF power density 10 to 250 mW / cm ² The substrate temperature is 80 to 300 ° C.
[0054]
The thickness of the first microcrystalline silicon film 103 is determined by the deposition time based on the deposition rate obtained in advance, and here the thickness is 30 nm. And SiH _Four Gas and H ₂ A substantially intrinsic amorphous silicon film 104 was produced without stopping the supply of the reactive gas and the glow discharge. Specifically, SiH _Four Increase the gas flow rate from 4 sccm to 40 sccm, ₂ While reducing the gas flow rate from 400 seem to 360 seem, the RF power density is 120 mW / cm ² To 48mW / cm ² Changed to. Here, the gas flow rate and the amount of change over time of the RF power density are design issues and are not described here. At this time, the substrate temperature was maintained at 160 ° C. and the pressure was maintained at 133 Pa.
[0055]
The film formation conditions for the amorphous silicon film are basically known techniques and are not limited to the above film formation conditions. The range of applicable film formation conditions is SiH. _Four H for gas ₂ The gas ratio may be selected in the range of 0% to 95%, pressure 5 to 266 Pa, RF power density 5 to 100 mW / cm. ² The substrate temperature is 80 to 350 ° C.
[0056]
The thickness of the substantially intrinsic amorphous silicon film 104 is also determined by the deposition time based on the deposition rate, and here, the thickness is 1000 nm. And SiH _Four Gas and H ₂ The second microcrystalline silicon film 105a was manufactured without stopping the supply of the reactive gas and the glow discharge. Specifically, SiH _Four Reduce the gas flow rate from 40 sccm to 4 sccm, ₂ While increasing the gas flow rate from 360 sccm to 400 sccm, the RF power density is 4 mW / cm. ² To 120mW / cm ² Changed to. At this time, the substrate temperature was maintained at 160 ° C. and the pressure was maintained at 133 Pa. The second microcrystalline silicon film 105a was set to have a thickness of 25 nm.
[0057]
In addition, instead of the substantially intrinsic amorphous silicon film in the above process, SiH _Four In addition to gas, carbon (C), germanium (Ge), tin (Sn) hydride, fluoride, chloride gas is introduced to form amorphous silicon carbide film, amorphous silicon germanium film It is also possible to form an amorphous silicon tin film.
[0058]
By taking the steps shown in the present embodiment, a junction having a continuously changing structure is formed from the microcrystalline silicon film to the amorphous silicon film and from the amorphous silicon film to the microcrystalline silicon film. I was able to.
[0059]
After the above steps, an integration processing step of dividing the photoelectric conversion layer and the electrode in the same substrate plane and connecting them in series was performed. The integration process is performed by a known technique, and includes a step of forming a hole in the photoelectric conversion layer and the electrode by a laser scribe method and a step of forming an insulating resin by a screen printing method. Matters relating to the design of the integration process are according to known examples and will not be described in detail here.
[0060]
The first openings 107a and 107b are insulating separation openings formed in the photoelectric conversion layer and the first electrode, and a plurality of unit cells are formed on the same substrate surface by the openings. The The second openings 108a and 108b are provided adjacent to the first openings 107a and 107b, respectively, and are openings for connecting the adjacent first electrode and the second electrode. The above was performed by the laser scribing method. (Fig. 1 (c))
[0061]
After forming the first opening and the second opening, an insulating resin was printed by a screen printing method. As the insulating resin, first insulating resin regions 109a and 109b and second insulating resin regions 111a and 111b were formed. The first insulating resin regions 109a and 109b are formed on and filling the first openings 107a and 107b, and the second insulating resin regions 111a and 111b are formed as the second openings 108a and 108b. Are provided adjacent to each other. A commercially available insulating resin may be used, but an acrylic or urethane resin is desirable and can be fired at about 200 ° C. The thickness of the insulating resin is not particularly limited, but here it is 20 μm thick. (Fig. 1 (d))
[0062]
The second electrode 106 was formed so as to cover the second microcrystalline silicon film 105a, the first insulating resin regions 109a and 109b, and the second insulating resin regions 111a and 111b. The second electrode 106 is a transparent electrode, and a known method typified by a vacuum evaporation method or a sputtering method may be used. Specifically, In ₂ O _Three , SnO ₂ ZnO, ITO film, or the like may be used. Here, the ITO film is formed by sputtering to a thickness of 70 nm. (Fig. 1 (e))
[0063]
The third openings 111a and 111b that separate the second electrode 106 into unit cells were formed on the second insulating resin region by a laser scribing method adjacent to the second opening. (Fig. 1 (f))
[0064]
Since the second electrode 106 has a relatively high resistivity, it is more desirable to form the auxiliary electrodes 113a and 113b. The auxiliary electrode 112 is provided in close contact with the second electrode 106 and is formed so as to cover the second openings 108a and 108b. The auxiliary electrode is formed of a highly conductive metal material, and here, silver (Ag) is formed in a comb shape by a screen printing method. (Fig. 1 (f))
[0065]
After the above steps, p-type conductivity determining impurities are introduced from the surface of the second electrode into the second microcrystalline silicon film 105a by ion doping to form the p-type microcrystalline silicon film 105b. The process to do was performed. Impurities that can be controlled to valence electrons in the p-type with respect to the microcrystalline silicon film include elements of Group IIIb of the periodic table such as boron (B), aluminum (Al), gallium (Ga), and indium (In) It ’s fine. In the ion doping method, a gas such as a hydride, chloride, or fluoride of the impurity element is turned into plasma, the generated impurity element is ionized, and an electric field is applied in a direction to accelerate the substrate, thereby applying an electric field to the substrate. It is a method of injection. In this embodiment, B ₂ H ₆ Gas was used. The dose is 2.0 × 10 ¹³ ~ 5.0 × 10 ¹⁵ / Cm ² In this case, 1.0 × 10 ¹⁴ / Cm ² It was. (Fig. 1 (g))
[0066]
In the ion doping method, the implanted element has a concentration distribution in the depth direction depending on the acceleration voltage, and it is necessary to appropriately adjust this value. In the case of a solar cell, although the optimum conditions differ depending on the thickness of the p-type layer, the acceleration voltage was set in the range of 5 to 25 keV. In this embodiment, it was set to 10 keV. Dose amount 1.0 × 10 ¹⁴ / Cm ² When B is implanted under the condition of an acceleration voltage of 10 keV, the concentration of B implanted into the film is examined by secondary ion mass spectrometry, and the concentration at the peak position is 5 × 10 5. ¹⁹ / Cm ^Three Concentration was obtained.
[0067]
According to the results of the experiment, the amount of B injected into the film changes almost in proportion to the dose, and the dose is 1.0 × 10 6. ¹⁵ / Cm ² If so, 5 × 10 ²⁰ / Cm ^Three Concentration was obtained.
[0068]
The acceleration voltage is increased, and the p-type is applied to a region in the vicinity of the interface between the second microcrystalline silicon film and the continuously changed second microcrystalline silicon film of the substantially intrinsic amorphous silicon film. An impurity element may be implanted. In the technical field of solar cells, a method of continuously changing the p-type impurity concentration at the p / i interface to improve the bondability at the interface is a conventionally known technique. In the prior art, it was necessary to precisely control a gas containing a small amount of a p-type impurity element using a computer or the like in the film forming process. However, according to the present invention, acceleration is performed in the ion doping process. Since only the voltage needs to be controlled, it becomes easier to control the thickness direction of the film of the impurity concentration at and near the interface.
[0069]
Since the implanted B element does not act as a p-type impurity element as it is, an activation step by heat treatment is required. The heat treatment step may be performed in an air atmosphere, a nitrogen atmosphere, or a hydrogen atmosphere, and the temperature may be in the range of 200 to 450 ° C., and preferably in the range of 300 to 400 ° C. Here, heat treatment was performed at 300 ° C. for 2 hours. (Fig. 1 (h))
[0070]
The conductivity after deposition of microcrystalline silicon is about 5 × 10 ^-Four S / cm, 2-3 × 10 by heat treatment at 300 ° C. ^-0 It was confirmed that it increased to S / cm. Furthermore, even in a microcrystalline silicon film into which no impurity element is implanted, the conductivity is about 1.1 × 10 10. ^-2 It was confirmed that it increased to S / cm. It was also confirmed that the microcrystalline silicon film into which no impurity element was implanted had n-type conductivity.
[0071]
Through the above steps, a solar cell in which a plurality of unit cells 110a, 110b, 110c were connected in series could be manufactured. The method for manufacturing a solar cell shown in this example includes a step of forming a first electrode, a step of forming a first microcrystalline silicon film, a step of forming a substantially intrinsic amorphous silicon film, A step of forming a second microcrystalline silicon film, a step of implanting a P-type determining impurity element into the second microcrystalline silicon film, and an amorphous silicon film substantially intrinsic to the first and second microcrystalline silicon films. A step of forming a second electrode, and a step of patterning the first or second electrode by a known method and arranging them at predetermined positions on the surface of the substrate. It can be applied to the production of serial connection structures, image sensors, and photosensors.
[0072]
【The invention's effect】
According to the present invention, it is necessary to consider contamination due to p-type and n-type impurities in the step of forming the p-type and n-type microcrystalline silicon films and the substantially intrinsic i-type amorphous silicon film. For example, it is possible to continuously form films in the same film forming chamber. Specifically, the p-type and n-type microcrystalline silicon films and the substantially intrinsic amorphous silicon film are SiH. _Four Gas or Si ₂ H ₆ Gas and H ₂ Since it can be produced only from gas, it can be formed by the same glow discharge plasma generating means provided in the same reaction chamber. This makes it possible to simplify the configuration of the plasma CVD apparatus. Further, it becomes possible to continuously produce p-type and n-type microcrystalline silicon films and substantially intrinsic amorphous silicon films while maintaining glow discharge plasma.
[0073]
Therefore, according to the present invention, the step of forming the first electrode, the step of forming the first microcrystalline silicon film, the step of forming the substantially intrinsic amorphous silicon film, A step of forming a crystalline silicon film; a step of implanting a P-type determining impurity element into the second microcrystalline silicon film; and an amorphous silicon film substantially intrinsic to the first and second microcrystalline silicon films. By the heating step, a microcrystalline silicon film exhibiting p-type and n-type conductivity and a substantially intrinsic amorphous silicon film can be obtained, and a pin junction can be formed. Therefore, it is not necessary to use the conventional n-type impurity element.
[0074]
The first and second microcrystalline silicon films and the substantially intrinsic amorphous silicon film are SiH. _Four Gas and H ₂ Since it can be produced from gas, it is not always necessary to switch the gas when producing each film. Therefore, the time required for the movement of the substrate from the reaction chamber to the reaction chamber and the introduction and exhaust of gas as required in the conventional process becomes unnecessary, and the process throughput can be improved.
[0075]
Further, according to the present invention, the p-type and n-type microcrystalline silicon films and the substantially intrinsic amorphous silicon film are simultaneously formed in each reaction chamber of a plasma CVD apparatus having a plurality of reaction chambers. Alternatively, each can be manufactured, and process throughput can be improved.
[0076]
In addition, a p-type conductivity-determining impurity element is implanted from the surface of the second microcrystalline semiconductor film using an ion doping method, so that the acceleration voltage at the time of implantation is controlled in the film thickness direction of the p-type impurity. The concentration distribution can be easily controlled.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an example of a method for manufacturing a photoelectric conversion device according to an embodiment.
FIG. 2 is a schematic diagram showing the configuration of a plasma CVD apparatus applied to produce a photoelectric conversion device of an example.
FIG. 3 is a graph showing a change in conductivity depending on a heat treatment temperature of a microcrystalline silicon film showing p-type and n-type conductivity obtained by an example.
[Explanation of symbols]
101 ・ ・ ・ ・ ・ ・ Board
102... First electrode
103... First microcrystalline silicon film (n-type)
104... Substantially intrinsic amorphous silicon film (i-type)
105a .... Second microcrystalline silicon film (before activation)
105b... Second microcrystalline silicon film (after activation)
106... Second electrode
107a, 107b ... 1st opening
108a, 108b ... second opening
109a, 109b... First insulating resin region
110a , 110b , 110c ... Unit cell
111a, 111b... Second insulating resin region
112a, 112b... Third aperture
112a, 112b... Auxiliary electrode
201 ... Transfer room
202 ..... Board loading / unloading room
203a, 203b, 203c ・ ・ ・ ・ ・ ・ ・ ・ Reaction chamber
204... Glow discharge plasma generation means
205... Reactive gas supply means

Claims (16)

Forming a first electrode over a substrate having an insulating surface;
Forming a first microcrystalline semiconductor film in the reaction chamber without adding N-type and P-type conductivity determining impurity elements on the first electrode;
On the first microcrystalline semiconductor film, a substantially intrinsic amorphous semiconductor film is formed in the reaction chamber without switching from a gas for forming the first microcrystalline semiconductor film,
A second microcrystalline semiconductor film is formed on the substantially intrinsic amorphous semiconductor film without adding N-type and P-type conductivity-determining impurity elements, and the first microcrystalline semiconductor film and the substantially microcrystalline semiconductor film. Formed in the reaction chamber without switching from a film-forming gas of an intrinsic amorphous semiconductor film,
Forming a second electrode over the second microcrystalline semiconductor film;
Injecting a P-type conductivity-determining impurity element from the surface of the second electrode into the second microcrystalline semiconductor film,
By subjecting the first and second microcrystalline semiconductor films and the substantially intrinsic amorphous semiconductor film to a heat treatment at a temperature of 300 ° C. to 400 ° C. , the first microcrystalline semiconductor film and A method for manufacturing a photoelectric conversion device, comprising increasing the conductivity of the second microcrystalline semiconductor film into which a P-type conductivity-determining impurity element is implanted . In claim 1,
A method for manufacturing a photoelectric conversion device, wherein the second electrode is formed over the second microcrystalline semiconductor film and then a third electrode made of a metal material is formed over the second electrode. Forming a first electrode over a substrate having an insulating surface;
Forming a first microcrystalline semiconductor film in the reaction chamber without adding N-type and P-type conductivity determining impurity elements on the first electrode;
On the first microcrystalline semiconductor film, a substantially intrinsic amorphous semiconductor film is formed in the reaction chamber without switching from a gas for forming the first microcrystalline semiconductor film,
A second microcrystalline semiconductor film is formed on the substantially intrinsic amorphous semiconductor film without adding N-type and P-type conductivity-determining impurity elements, and the first microcrystalline semiconductor film and the substantially microcrystalline semiconductor film. Formed in the reaction chamber without switching from a film-forming gas of an intrinsic amorphous semiconductor film,
Adjacent first and second openings penetrate through the first electrode, the first microcrystalline semiconductor film, the substantially intrinsic amorphous semiconductor film, and the second microcrystalline semiconductor film. Forming multiple holes,
Filling each of the plurality of first openings with an insulating resin;
A second electrode is formed to cover the second microcrystalline semiconductor film and the plurality of insulating resins, and the first electrode and the second electrode are connected in the plurality of second openings. ,
Forming a third aperture in the second electrode adjacent to each of the plurality of second apertures;
Injecting a P-type conductivity-determining impurity element from the surface of the second electrode into the second microcrystalline semiconductor film,
By subjecting the first and second microcrystalline semiconductor films and the substantially intrinsic amorphous semiconductor film to a heat treatment at a temperature of 300 ° C. to 400 ° C. , the first microcrystalline semiconductor film and A method for manufacturing a photoelectric conversion device, comprising increasing the conductivity of the second microcrystalline semiconductor film into which a P-type conductivity-determining impurity element is implanted . In claim 3,
After forming the second electrode so as to cover the second microcrystalline semiconductor film and the plurality of insulating resins, a third electrode made of a metal material is formed over the second electrode. A method for manufacturing a photoelectric conversion device.   5. The method for manufacturing a photoelectric conversion device according to claim 3, wherein the plurality of insulating resins are acrylic resins or urethane resins.   6. The photoelectric conversion device according to claim 3, wherein the first opening, the second opening, and the third opening are formed using a laser scribing method. Manufacturing method. In any one of Claims 1 thru | or 6,
When the P-type conductivity-determining impurity element is implanted from the surface of the second electrode into the second microcrystalline semiconductor film, the second microcrystalline semiconductor film and the substantially intrinsic non-impurity element are introduced. A method for manufacturing a photoelectric conversion device, comprising implanting the P-type conductivity-determining impurity element in the vicinity of an interface with a crystalline semiconductor film. In any one of Claims 1 thru | or 7,
The first microcrystalline semiconductor film, the substantially intrinsic amorphous semiconductor film, and the second microcrystalline semiconductor film are formed by the same glow discharge plasma generating means. A method for manufacturing a conversion device. In any one of Claims 1 thru | or 7,
The first microcrystalline semiconductor film, the substantially intrinsic amorphous semiconductor film, and the second microcrystalline semiconductor film are continuously formed by the same glow discharge plasma generation means while maintaining glow discharge. A method for manufacturing a photoelectric conversion device, which is characterized by being formed. In any one of Claims 1 thru | or 7,
A method for manufacturing a photoelectric conversion device, wherein the first microcrystalline semiconductor film, the substantially intrinsic amorphous semiconductor film, and the second microcrystalline semiconductor film are formed by a plasma CVD apparatus. . In any one of Claims 1 thru | or 10,
The first microcrystalline semiconductor film and the second microcrystalline semiconductor film are microcrystalline silicon films, and the substantially intrinsic amorphous semiconductor film is an amorphous silicon film. A method for manufacturing a photoelectric conversion device. In any one of Claims 1 thru | or 11,
A method for manufacturing a photoelectric conversion device, wherein the P-type conductivity-determining impurity element is implanted into the second microcrystalline semiconductor film by an ion doping method. In any one of Claims 1 thru | or 12,
The method for manufacturing a photoelectric conversion device, wherein the P-type conductivity-determining impurity element is an element selected from B, Al, Ga, and In. In any one of claims 1 to 13, the P-type conductivity determining impurity element, 2 × ¹⁰ 13 ^{cm -2} or more 5 × ¹⁰ 15 ^{cm -2} or less the a dose of the second microcrystalline semiconductor film A method for manufacturing a photoelectric conversion device, which is characterized by being injected into the substrate. In any one of claims 1 to 14, wherein the N-type and P-type conductivity determining impurity element of the first microcrystalline semiconductor film formed without the addition of the to show the N-type conductivity A method for manufacturing a photoelectric conversion device. In any one of Claims 1 thru | or 15 ,
The method for manufacturing a photoelectric conversion device, wherein the second electrode is a light transmissive electrode made of one or more materials selected from In ₂ O ₃ , SnO ₂ , and ZnO.

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