JP3346907B2 - Solar cell and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell,
The present invention relates to a crystalline silicon solar cell having high photoelectric conversion efficiency and a method for manufacturing the same.

[0002]

2. Description of the Related Art In order to increase the photoelectric conversion efficiency of a crystalline silicon solar cell, a silicon semiconductor substrate having the same conductivity type as the substrate and having a higher conductivity is provided on the back surface opposite to the light incident side (hereinafter referred to as the light receiving surface). 2. Description of the Related Art A solar cell having a structure in which a microcrystalline silicon semiconductor layer having hydrogen containing a high concentration of impurities is provided is known (for example, Japanese Patent Application Laid-Open No. 4-192569). This specification
In the book, microcrystals and non-crystals as described in
A layer consisting of crystalline mixed silicon hydride
It is called a crystalline silicon semiconductor layer.

FIG. 9 shows a cross-sectional view of this solar cell. First
A silicon semiconductor layer 32 of the second conductivity type is formed on the light receiving surface of the silicon semiconductor substrate 31 of the conductivity type, and the back surface is covered with a thermal oxide film layer 40. The thermal oxide film layer 40 is provided with a plurality of dot-shaped openings, and the microcrystalline silicon semiconductor layer 37 containing hydrogen of the first conductivity type formed so as to cover the bottom surface of the thermal oxide film layer 40 is Is in contact with the silicon semiconductor substrate 31 through the opening. As shown in the energy band diagram of FIG. 10, the microcrystalline silicon semiconductor layer 37 containing hydrogen has a band gap larger than that of the silicon semiconductor substrate 31 and has a high concentration of impurities. An internal electric field is formed near the microcrystalline silicon semiconductor layer 37 containing hydrogen. Due to this internal electric field, majority carriers generated near the back surface of the silicon semiconductor substrate 31 are efficiently converted to the back electrode 38.
To the silicon semiconductor substrate 31
The carrier is pushed back inside, and recombination of carriers near the back surface of the silicon semiconductor substrate 31 is reduced.

[0004] Since the thermal oxide film layer 40 is present except for the opening where the microcrystalline semiconductor layer containing hydrogen is formed in contact with the back surface of the silicon semiconductor substrate 31, this layer 40 is formed. Oxygen atoms in the passivation inactivate (passivate) defects in the portion of the back surface of the silicon semiconductor substrate 31 that does not take out majority carriers, and suppress the recombination of carriers formed by photoelectric conversion via the defects. (Hereinafter referred to as a back surface passivation effect).

[0005]

However, when the thermal oxide film layer 40 is used as a layer for extracting the back surface passivation effect (hereinafter referred to as a back surface passivation layer), processing at a high temperature of 800.degree. Becomes In the production of a crystalline silicon solar cell, such a treatment at a high temperature causes the following problems, and therefore it is necessary to avoid it as much as possible.

Since the dopant profile of the second conductivity type silicon semiconductor layer 32 changes and the characteristics of the PN junction change, it is necessary to set conditions in consideration of this change in the process of manufacturing a solar cell. Management of manufacturing conditions becomes complicated.

[0007] Deterioration of characteristics of silicon semiconductor substrate 31
(Especially, a reduction in carrier lifetime in the substrate).

Further, since the thermal oxide film layer 40 does not allow the carriers generated near the back surface of the silicon semiconductor substrate 31 to pass through, there is a problem that the carrier extraction efficiency on the back surface is reduced.

Further, in the step of forming the thermal oxide film layer 40 and the microcrystalline silicon semiconductor layer 37 containing hydrogen on the back surface of the silicon semiconductor substrate 31, the deposition rate is very low (0.
(1 nm / s or less) A process of depositing the microcrystalline silicon semiconductor layer 37 containing hydrogen by a plasma CVD method, a process of photoetching, and the like are included. It was such a thing.

The present invention solves the above problems,
It is an object of the present invention to provide a configuration of a solar cell having high photoelectric conversion efficiency in which changes in PN characteristics and substrate characteristics are suppressed, and a method of manufacturing a solar cell that can be manufactured simply and in a short time.

[0011]

According to a first aspect of the present invention, there is provided a solar cell comprising a silicon semiconductor substrate of a first conductivity type and a light- receiving side of the silicon semiconductor substrate.
Having a second conductivity type silicon semiconductor layer formed
Water in contact with the back surface of the silicon semiconductor substrate in the pond
An amorphous silicon semiconductor layer having silicon and the amorphous silicon semiconductor layer.
The silicon semiconductor replaced by part of the semiconductor layer
Crystal having hydrogen of the first conductivity type in contact with the back surface of the body substrate
A silicon semiconductor layer and the intrinsic amorphous silicon semiconductor layer
And a back surface formed to cover the microcrystalline silicon semiconductor layer
And a surface electrode .

[0012] The solar cell according to claim 2, the
The amorphous silicon semiconductor layer containing hydrogen is
It has the same conductivity type as the conductive substrate.

According to a third aspect of the present invention, there is provided a method for manufacturing a solar cell.
At least the light incident side of the silicon semiconductor substrate of the first conductivity type
Forming a silicon semiconductor layer of the second conductivity type in
Hydrogen on the entire back surface of the silicon semiconductor substrate
Forming a crystalline silicon semiconductor layer;
Laser light irradiates a part of the amorphous silicon semiconductor layer
By doing so, the silicon semiconductor substrate is partially
Amorphous silicon semiconductor layer having an amount of hydrogen of the first conductivity type
To change to microcrystalline silicon semiconductor layer containing hydrogen
And include

According to a fourth aspect of the present invention, there is provided a method of manufacturing a solar cell.
4. The manufacturing method according to claim 3, wherein the laser beam is irradiated.
Amorphous silicon semiconductor containing hydrogen
Microcrystalline silicon semiconductor having body layer of first conductivity type hydrogen
Includes first conductivity type impurities and hydrogen gas to be converted into layers
Things.

According to a fifth aspect of the present invention, there is provided a method for manufacturing a solar cell.
4. The manufacturing method according to claim 3, wherein an amorphous silicon semiconductor layer having hydrogen of the first conductivity type is formed on the entire back surface of the silicon semiconductor substrate, and the amorphous silicon semiconductor layer having hydrogen of the first conductivity type is formed. A portion of the silicon semiconductor layer is irradiated with laser light, and the portion is changed to a microcrystalline silicon semiconductor layer containing hydrogen of the first conductivity type.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a solar cell as defined in the fifth aspect.
The atmosphere at the time of light irradiation contains hydrogen gas .

Further, the method for manufacturing a solar cell according to claim 7 is the same as the method for manufacturing a solar cell according to claim 5 above.
The first conductivity type impurity in the atmosphere when irradiating the laser beam.
And hydrogen gas .

[0018]

In the solar cell according to the first aspect of the present invention, since the amorphous silicon semiconductor layer having hydrogen is used as the back surface passivation layer, defects generated on the back surface of the silicon semiconductor substrate can be reduced. It can be inactivated by hydrogen atoms in the silicon semiconductor layer, and can suppress recombination of carriers generated by photoelectric conversion via the defect. Further, the substrate temperature required for forming the hydrogen-containing amorphous silicon semiconductor layer is 300 ° C. or less, which eliminates the need for high-temperature processing unlike the case where a thermal oxide film layer is used for the back surface passivation layer. Changes in the PN characteristics of the surface and changes in the substrate characteristics can be suppressed.

In this structure, the conductivity type of the amorphous silicon semiconductor layer having hydrogen can be made the same as that of the substrate, and the resistance can be reduced. A part of majority carriers generated near the back surface of the substrate can be guided to the back electrode through the layer.

Further, in the manufacturing method according to the third aspect, the first method
Laser light irradiation is performed on a part of the amorphous silicon semiconductor layer containing hydrogen formed over the silicon semiconductor substrate of the conductivity type, whereby a microcrystalline silicon semiconductor layer of the first conductivity type containing hydrogen is obtained. Therefore, processing steps on the backside of the substrate include:
Since the method does not include a step of depositing a microcrystalline silicon semiconductor layer containing hydrogen by a plasma CVD method with a low deposition rate or a complicated step such as photoetching, the processing can be performed easily and in a short time (usually several minutes). it can.

According to the fourth aspect of the present invention, the amorphous silicon semiconductor layer having hydrogen is converted into a fine layer of the first conductivity type by including an impurity of the first conductivity type in the atmosphere when the laser beam is irradiated. It can be changed to a crystalline silicon semiconductor layer.

According to a fifth aspect of the present invention, a laser beam is irradiated to a part of the first conductive type hydrogen-containing amorphous silicon semiconductor layer formed on the first conductive type silicon semiconductor substrate. To obtain a first conductivity type microcrystalline silicon semiconductor layer containing hydrogen.

In the manufacturing method according to the sixth aspect, since hydrogen is included in the atmosphere when laser light irradiation is performed, hydrogen released from the layer during laser light irradiation can be supplemented.

According to the seventh aspect of the present invention, the impurity concentration of the hydrogen-containing microcrystalline silicon semiconductor layer is increased because the first conductivity type dopant is included in the atmosphere when the laser light is irradiated. Can be.

[0025]

【Example】

(First Embodiment) FIG. 1 is a sectional view of a solar cell according to a first embodiment of the present invention. An N-type silicon semiconductor layer 12 is formed on the light receiving surface of the P-type silicon semiconductor substrate 11.
Further, a silicon oxide film layer 13 and an anti-reflection film layer 14 are formed so as to further cover them. Silicon oxide film layer 1
Numeral 3 is provided to inactivate surface defects of the N-type silicon semiconductor layer 12, and an antireflection film layer 14 is provided to reduce reflection of incident light. The current is applied to the silicon oxide film layer 1
Third, the light is extracted through a grid electrode 15 that penetrates the antireflection film layer 14 and is connected to the N-type silicon semiconductor layer 12. An intrinsic amorphous silicon semiconductor layer 16 containing hydrogen is formed on the back surface of the P-type silicon semiconductor substrate 11, and a P ⁺ -type impurity containing hydrogen doped with a high concentration of impurities is dispersed in the layer 16 portion. A microcrystalline silicon semiconductor layer 17 is formed. They are covered by a back electrode 18. The current on the back surface is extracted from the P-type silicon semiconductor substrate 11 through the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen and the back surface electrode 18.

According to this embodiment, the internal electric field exists between the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen and the P-type silicon semiconductor substrate 11. The majority carriers (vacancies) among the carriers generated near the back surface of the silicon semiconductor substrate 11 are efficiently led out to the back electrode 18. In addition, since the intrinsic amorphous silicon semiconductor layer 16 containing hydrogen is formed in contact with the back surface of the P-type silicon semiconductor substrate 11, defects occurring on the back surface of the P-type silicon semiconductor Can be inactivated by hydrogen atoms in the porous silicon semiconductor layer 16. As a result, recombination of carriers generated near the back surface of the P-type silicon semiconductor substrate 11 via the above-described defect can be suppressed. Thus, a solar cell having high photoelectric conversion efficiency can be realized.

FIG. 2 is a manufacturing flowchart showing a method for manufacturing the solar cell of FIG.

First, a single-crystal P-type silicon semiconductor substrate 1
After cleaning 1, anisotropic etching is performed so that the surface becomes uneven. The silicon semiconductor substrate 11 is not limited to a single-crystal P-type silicon semiconductor substrate, but may be a polycrystalline P-type silicon semiconductor substrate. In this case, the unevenness on the surface is formed by digging a groove by laser light irradiation or mechanical means.

Next, the N-type silicon semiconductor layer 12 is deposited on the light-receiving surface of the P-type silicon semiconductor substrate 11 by vapor phase diffusion using phosphorus oxychloride (POCl ₃ ).
Are formed by diffusion. Subsequently, silicon oxide (SiO
₂ ) The film layer 13 is formed by a thermal oxidation method, and silicon nitride (Si)
₃ N ₄₎ plasma CVD anti-reflective film layer 14 made of film
It is formed by a method. As the antireflection film 14, a titanium oxide (TiO ₂ ) film, an alumina (Al ₂ O ₃ ) film, or the like can be used.

Subsequently, the back surface of the P-type silicon semiconductor substrate 11 is etched to remove the N-type silicon semiconductor and the silicon oxide film deposited on the back surface. When the N-type silicon semiconductor layer 12 is formed by diffusing only the light receiving surface using a coating solution such as a silicon oxide glass solution containing phosphorus, it is not necessary to remove the N-type silicon semiconductor on the back surface. is there.

Next, a film thickness of 30
Intrinsic amorphous silicon semiconductor layer 16 having 0 nm of hydrogen
Is formed on the back surface of the P-type silicon semiconductor substrate 11. The intrinsic amorphous silicon semiconductor layer 16 has a substrate temperature of 200
C., an input RF power of 10 W (13.56 MHz), and a film was formed under the conditions using silane (SiH ₄ ) gas as a source gas. The deposition rate was about 1 nm / s. This condition is an example, and the film forming condition is not limited to the above condition. For example, as raw material gas types, silane gas and hydrogen (H
₂ ) A mixed gas of gases or disilane (Si ₂ H ₆ ) gas may be used.

Next, a portion of the intrinsic amorphous silicon semiconductor layer 16 containing hydrogen is irradiated with a laser beam in an atmosphere containing a P-type dopant to microcrystallize the portion and simultaneously apply the P-type dopant. P ⁺ with hydrogen added
A type microcrystalline silicon semiconductor layer 17 is obtained. As a P-type dopant, boron trichloride (BCl ₃ ), trimethyl boron (B (CH ₃ ) ₃ ), diborane (B ₂ H ₆ ), or the like can be used. As a laser beam, an ArF excimer laser (wavelength:
195 nm), KrF excimer laser (wavelength: 248 n)
m), a XeCl excimer laser (wavelength: 308 nm) or the like can be used. Although the irradiation laser light amount was 400 mJ / cm ² , it is not limited to this.

If hydrogen gas is added to the atmosphere to be irradiated with the laser beam, hydrogen released when the intrinsic amorphous silicon semiconductor layer 16 containing hydrogen is microcrystallized can be replenished. Accordingly, defects due to hydrogen elimination in the intrinsic amorphous silicon semiconductor layer 16 containing hydrogen and the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen can be suppressed.

Subsequently, the back electrode 18 is covered with the intrinsic amorphous silicon semiconductor layer 16 containing hydrogen and the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen, and a metal such as aluminum or silver is deposited by vacuum evaporation. Is formed by vapor deposition. Next, after processing the silicon oxide film layer 13 and the antireflection film 14 on the light receiving surface side by using a photoetching method, a metal is deposited in the order of titanium, palladium, and silver.
Finally, the grid electrode 15 is formed by performing lift-off.

In the above steps, the intrinsic amorphous silicon semiconductor layer 16 containing hydrogen for passivating the back surface of the P-type silicon semiconductor substrate 11 and the microcrystalline silicon semiconductor layer 17 containing hydrogen for forming an internal electric field are formed at 300 ° C. It can be performed at the following low temperatures. Therefore, it is possible to suppress a change in the characteristics of the PN junction on the light receiving surface and a deterioration in the substrate characteristics caused by repeating the high-temperature processing. In addition, the processing steps on the back surface side of the P-type silicon substrate 11 do not include complicated processing steps such as photoetching or steps that take a long time such as formation of a microcrystalline silicon semiconductor layer containing hydrogen by a plasma CVD method. Therefore, the processing can be easily performed in a short time.

(Second Embodiment) FIG. 3 is a sectional view showing a solar cell according to a second embodiment. 1 are denoted by the same reference numerals, and description thereof is omitted. On the back surface of the P-type silicon semiconductor substrate 11, a P-type amorphous silicon semiconductor layer 19 having hydrogen is formed, and further, in contact with the P-type silicon semiconductor substrate 11, the P-type amorphous silicon semiconductor having hydrogen A P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen is formed dispersed in the layer 19. Also in the case of this configuration, the P-type amorphous silicon semiconductor layer 19 having hydrogen
However, similarly to the first embodiment, defects generated on the back surface of the P-type silicon semiconductor substrate 11 can be inactivated by hydrogen atoms, and carriers generated near the back surface of the P-type silicon semiconductor substrate 11 can be inactivated. Recombination via the above defects can be suppressed. In addition, as the back surface passivation layer,
When the P-type amorphous silicon semiconductor layer 19 containing hydrogen is used, since the layer 19 itself has conductivity, a part of majority carriers can be guided to the back surface electrode 18 through this layer, and a higher photoelectric conversion can be achieved. A solar cell having high efficiency can be realized.

Next, FIG. 4 is a manufacturing flowchart showing a method of manufacturing the solar cell of FIG. It should be noted that other than the steps of manufacturing the P-type amorphous silicon semiconductor layer 19 containing hydrogen and the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen, that is, the N-type silicon semiconductor layer 12, the silicon oxide film layer 13, the antireflection film The manufacturing process of the layer 14, the grid electrode 15, and the back surface electrode 18 is the same as the manufacturing process of the solar cell of the first embodiment, and the description is omitted.

The P-type amorphous silicon semiconductor layer 19 containing hydrogen was formed by a plasma CVD method. The film forming conditions were as follows: substrate temperature = 200 ° C., input RF power = 10 W, source gas = mixed gas of H ₂ diluted SiH ₄ and B ₂ H ₆ , B ₂ H ₆ / Si
H ₄ = 0.002 and thickness = 300 nm. This condition is an example, and a film can be formed under conditions other than the above.

The P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen is a P-type amorphous silicon semiconductor layer 19 containing hydrogen.
Is obtained by irradiating a part of the laser beam with laser light. In general, the activation rate of boron in a P-type amorphous silicon semiconductor containing hydrogen is low, but when it is microcrystallized, the activation rate of boron increases and the semiconductor becomes P ⁺ -type.

When hydrogen gas is included in the atmosphere at the time of laser beam irradiation, it is possible to supplement the hydrogen released from the P-type amorphous silicon semiconductor layer 19 containing hydrogen when the layer is microcrystallized. it can. Therefore, defects due to hydrogen elimination can be suppressed.

Further, when the P-type amorphous silicon semiconductor layer 19 containing hydrogen is irradiated with a laser beam to form the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen, an atmosphere containing boron trichloride gas, trimethyl boron gas, When a dopant such as diborane gas is included, a P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen having a higher concentration of impurities is obtained,
A larger internal electric field is generated between the back surface of the silicon semiconductor substrate 11 and the P ⁺ -type microcrystalline silicon semiconductor layer 17 containing hydrogen.

In the above manufacturing method, the solar cell can be manufactured easily and in a short time, as in the case of the first embodiment.

(Third Embodiment) FIG. 5 is a sectional view of a solar cell according to a third embodiment of the present invention. On the light receiving surface of the N-type silicon semiconductor substrate 21, a P-type silicon semiconductor layer 22 is formed. Further, a silicon oxide film layer 23 and an anti-reflection film layer 24 are formed so as to further cover them. The silicon oxide film layer 23 is provided to inactivate surface defects of the P-type silicon semiconductor layer 22, and the antireflection film layer 24 is provided to reduce reflection of incident light. The current is extracted through a grid electrode 25 that passes through the silicon oxide film layer 23 and the antireflection film layer 24 and is connected to the P-type silicon semiconductor layer 22. On the back surface of the N-type silicon semiconductor substrate 21, an intrinsic amorphous silicon semiconductor layer 26 containing hydrogen is formed, and an N ⁺ -type impurity containing hydrogen doped with a high concentration of impurities is dispersed in the layer 26. A microcrystalline silicon semiconductor layer 27 is formed. They are covered by a back electrode 28, and the current on the back surface is extracted from the N-type silicon semiconductor substrate 21 through the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen and the back electrode 28.

With this structure, according to the present embodiment, since an internal electric field exists between the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen and the N-type silicon semiconductor substrate 21, Majority carriers (electrons) among the carriers generated near the back surface of the silicon semiconductor substrate 21 are efficiently led to the back electrode 28. Further, since the intrinsic amorphous silicon semiconductor layer 26 containing hydrogen is formed in contact with the back surface of the N-type silicon semiconductor substrate 21, a defect generated on the back surface of the N-type silicon semiconductor substrate 21 is reduced to an intrinsic non-hydrogen containing hydrogen. It can be inactivated by hydrogen atoms in the crystalline silicon semiconductor layer 26. As a result, recombination of carriers generated near the back surface of the N-type silicon semiconductor substrate 21 via the above-described defect can be suppressed. Thus, a solar cell having high photoelectric conversion efficiency can be realized.

FIG. 6 is a manufacturing flowchart showing a method for manufacturing the solar cell of FIG.

First, a single-crystal N-type silicon semiconductor substrate 2
After cleaning 1, anisotropic etching is performed so that the surface becomes uneven. The silicon semiconductor substrate 21 is not limited to a single-crystal N-type silicon semiconductor substrate, but may be a polycrystalline N-type silicon semiconductor substrate. In this case, the unevenness on the surface is formed by digging a groove by laser light irradiation or mechanical means.

Next, boron is diffused to the light-receiving surface of the N-type silicon substrate 21 by vapor phase diffusion using boron tribromide (BBr ₃ ) to form a P-type silicon semiconductor layer 22. Subsequently, a silicon oxide (SiO ₂ ) film layer 2 is formed by a thermal oxidation method.
3 is formed, and an anti-reflection film layer 24 made of a silicon nitride (Si ₃ N ₄ ) film is formed by a plasma CVD method. Titanium oxide as an antireflection film 24 (TiO ₂₎ film or an alumina (Al ₂ O ₃₎ film or the like can be used.

Subsequently, the back surface of the N-type silicon semiconductor substrate 21 is etched to remove the P-type silicon semiconductor and the silicon oxide film deposited on the back surface. When the P-type silicon semiconductor layer 22 is formed by diffusing only the light-receiving surface using a coating liquid such as a silicon oxide glass liquid containing boron, it is not necessary to remove the P-type silicon semiconductor on the back surface. .

Next, an intrinsic amorphous silicon semiconductor layer 26 containing hydrogen is formed to a thickness of 300 nm by a plasma CVD method.
To form on the back surface of the N-type silicon semiconductor substrate 21. The intrinsic amorphous silicon semiconductor layer 26 has a substrate temperature of 200
C., an input RF power of 10 W (13.56 MHz), and a film using silane gas as a source gas. The deposition rate was about 1 nm / s. This condition is an example, and the film forming condition is not limited to the above condition. For example, a mixed gas of a silane gas and a hydrogen gas or a disilane gas may be used as a source gas.

Next, in phosphorus trichloride (PCl ₃ ) gas,
A portion of the intrinsic amorphous silicon semiconductor layer 26 containing hydrogen is irradiated with an ArF excimer laser beam at a dose of 400 mJ / cm ² to microcrystallize the portion and simultaneously add phosphorus (N ⁺ type containing hydrogen). Microcrystalline silicon semiconductor layer 27
Becomes). The method of microcrystallization and the method of adding impurities are not limited to the above conditions, and may be performed in a gas of phosphine (PH ₃ ), trimethylphosphine ((CH ₃ ) ₃ P), or a mixed gas of these gases and hydrogen gas. Then, a laser beam may be irradiated. The laser light may be a KrF excimer laser light, a XeCl excimer laser light, or the like. The irradiation laser light amount is not limited to 400 mJ / cm ² .

If hydrogen gas is added to the atmosphere to be irradiated with laser light, hydrogen released when microcrystalline the intrinsic amorphous silicon semiconductor layer 26 containing hydrogen can be replenished. Accordingly, defects due to hydrogen elimination in the intrinsic amorphous silicon semiconductor layer 26 containing hydrogen and the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen can be suppressed.

Subsequently, the back electrode 28 is covered with the intrinsic amorphous silicon semiconductor layer 26 containing hydrogen and the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen, and is made of aluminum or silver by vacuum evaporation. It is formed by evaporating metal. Next, after processing the silicon oxide film layer 23 and the antireflection film 24 on the light-receiving surface side by using a photo-etching method, a metal is deposited in the order of titanium, palladium, and silver.
Finally, the grid electrode 25 is formed by performing lift-off.

In the above steps, the intrinsic amorphous silicon semiconductor layer 26 containing hydrogen for passivating the back surface of the N-type silicon semiconductor substrate 21 and the microcrystalline silicon semiconductor layer 27 containing hydrogen for forming an internal electric field are formed at 300 ° C. It can be performed at the following low temperatures. Therefore, it is possible to suppress a change in the characteristics of the PN junction on the light receiving surface and a deterioration in the substrate characteristics caused by repeating the high-temperature processing. In addition, the processing steps on the back surface side of the N-type silicon substrate 21 do not include complicated processing steps such as photoetching or long-time steps such as formation of a microcrystalline silicon semiconductor layer containing hydrogen by a plasma CVD method. Therefore, the processing can be easily performed in a short time.

(Fourth Embodiment) FIG. 7 is a sectional view showing a solar cell according to a fourth embodiment. 5 are denoted by the same reference numerals, and description thereof will be omitted. An N-type amorphous silicon semiconductor layer 29 having hydrogen is formed on the back surface of the N-type silicon semiconductor substrate 21. Further, the N-type amorphous silicon semiconductor having hydrogen is in contact with the N-type silicon semiconductor substrate 21. An N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen is formed dispersed in the layer 29. Also in the case of this configuration, the N-type amorphous silicon semiconductor layer 29 containing hydrogen
However, similar to the third embodiment, the N-type silicon semiconductor substrate 2
1 can be inactivated by hydrogen atoms, and recombination of carriers generated near the rear surface of the N-type silicon semiconductor substrate 21 via the defects can be suppressed. In particular, when the N-type amorphous silicon semiconductor layer 29 containing hydrogen is used as the back surface passivation layer,
Since the layer 29 itself has conductivity, a part of majority carriers can be guided to the back electrode 28 through the layer 29, and a solar cell having higher photoelectric conversion efficiency can be realized.

Next, FIG. 8 is a manufacturing flowchart showing a method of manufacturing the solar cell of FIG. It should be noted that other than the steps of manufacturing the N-type amorphous silicon semiconductor layer 29 containing hydrogen and the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen, that is, the P-type silicon semiconductor layer 22, the silicon oxide film layer 23, the antireflection film The steps of forming the layer 24, the grid electrode 25, and the back electrode 28 are the same as the steps of manufacturing the solar cell of the third embodiment, and a description thereof will be omitted.

The N-type amorphous silicon semiconductor layer 29 containing hydrogen was formed by a plasma CVD method. The film forming conditions were as follows: substrate temperature = 200 ° C., input RF power = 10 W, source gas = mixed gas of SiH ₄ and PH ₃ diluted with H ₂ , PH ₃ / SiH
₄ = 0.005 and thickness = 300 nm. This condition is an example, and a film can be formed under conditions other than the above.

The N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen is an N-type amorphous silicon semiconductor layer 29 containing hydrogen.
Is obtained by irradiating a part of the laser beam with laser light. In general, the activation rate of phosphorus in an N-type amorphous silicon semiconductor containing hydrogen is low, but when it is microcrystallized, the activation rate of phosphorus increases and the semiconductor becomes N ⁺ -type.

When hydrogen gas is included in the atmosphere for laser beam irradiation, hydrogen released from the N-type amorphous silicon semiconductor layer 29 containing hydrogen when the layer is microcrystallized can be supplemented. it can. Therefore, defects due to hydrogen elimination can be suppressed.

Further, when the N-type amorphous silicon semiconductor layer 29 containing hydrogen is irradiated with laser light to form the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen, an atmosphere such as phosphine gas or trimethylphosphine gas is used. Including the dopant, N ⁺ with hydrogen with a higher concentration of impurities
As a result, a larger internal electric field is generated between the back surface of the silicon semiconductor substrate 21 and the N ⁺ -type microcrystalline silicon semiconductor layer 27 containing hydrogen.

In the above manufacturing method, the solar cell can be manufactured easily and in a short time as in the case of the third embodiment.

[0061]

As described above, according to the solar cell of the present invention, since the amorphous silicon semiconductor layer containing hydrogen is used as the back surface passivation layer, the photoelectric conversion efficiency can be improved. In addition, the substrate temperature required for forming the back surface passivation layer can be reduced, and a change in the PN characteristics of the light receiving surface and a change in the substrate characteristics can be suppressed.

According to the method for manufacturing a solar cell of the present invention, a part of an intrinsic or first conductivity type amorphous silicon semiconductor layer containing hydrogen is irradiated with a laser beam to contain hydrogen. A microcrystalline silicon semiconductor layer of the first conductivity type is obtained, and a step of depositing the microcrystalline silicon semiconductor layer;
Since a complicated process such as photoetching is not included, the process can be performed easily and in a short time (usually several minutes).

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a solar cell according to a first embodiment of the present invention.

FIG. 2 is a manufacturing flowchart showing a method for manufacturing the solar cell of FIG.

FIG. 3 is a sectional view showing a structure of a solar cell according to a second embodiment of the present invention.

FIG. 4 is a manufacturing flowchart showing a method for manufacturing the solar cell of FIG.

FIG. 5 is a sectional view showing a structure of a solar cell according to a third embodiment of the present invention.

FIG. 6 is a manufacturing flowchart showing a method for manufacturing the solar cell of FIG.

FIG. 7 is a cross-sectional view illustrating a structure of a solar cell according to a fourth embodiment of the present invention.

FIG. 8 is a manufacturing flowchart showing a method for manufacturing the solar cell of FIG. 7;

FIG. 9 is a cross-sectional view illustrating a structure of a conventional solar cell.

FIG. 10 is an energy band diagram of the solar cell of FIG.

[Explanation of symbols]

Reference Signs List 11 P-type silicon semiconductor substrate 12 N-type silicon semiconductor layer 16 Intrinsic amorphous semiconductor layer containing hydrogen 17 P ⁺ -type microcrystalline silicon semiconductor layer containing hydrogen 19 P-type amorphous semiconductor layer containing hydrogen 21 N-type silicon semiconductor Substrate 22 P-type silicon semiconductor layer 26 Intrinsic amorphous silicon semiconductor layer having hydrogen 27 N ⁺ -type microcrystalline silicon semiconductor layer having hydrogen 29 N-type amorphous silicon semiconductor layer having hydrogen

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Nishida 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Yuji 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp shares In-company (56) References JP-A-4-192569 (JP, A) JP-A-64-51673 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04

Claims (7)

(57) [Claims] 1. A solar cell having a silicon semiconductor substrate of a first conductivity type and a silicon semiconductor layer of a second conductivity type formed on a light incident side of the silicon semiconductor substrate, wherein hydrogen in contact with a back surface of the silicon semiconductor substrate is provided. and the amorphous silicon semiconductor layer having the replaced part of the amorphous silicon semiconductor layer, before
Hydrogen of the first conductivity type in contact with the back surface of the silicon semiconductor substrate
A microcrystalline silicon semiconductor layer, the intrinsic amorphous silicon semiconductor layer and the microcrystalline silicon
A solar cell , comprising: a back electrode formed to cover the semiconductor layer . 2. The solar cell according to claim 1, wherein the hydrogen-containing amorphous silicon semiconductor layer has the same conductivity type as the silicon semiconductor substrate. Forming a silicon semiconductor layer of a second conductivity type on at least a light incident side of the silicon semiconductor substrate of the first conductivity type; and amorphous silicon having hydrogen over the entire back surface of the silicon semiconductor substrate. Forming a semiconductor layer; and irradiating a portion of the hydrogen-containing amorphous silicon semiconductor layer with laser light to form the silicon semiconductor substrate.
Converting the amorphous silicon semiconductor layer having a part of hydrogen to a microcrystalline silicon semiconductor layer having hydrogen of the first conductivity type up to the above . 4. The method for manufacturing a solar cell according to claim 3, wherein the amorphous silicon semiconductor layer containing hydrogen is converted to a microcrystalline silicon semiconductor containing hydrogen of the first conductivity type in an atmosphere when the laser light is irradiated. A method for manufacturing a solar cell, comprising a first conductivity type impurity to be changed into a layer and hydrogen gas . 5. The method for manufacturing a solar cell according to claim 3, wherein the first surface of the silicon semiconductor substrate is entirely covered on the back surface.
Forming an amorphous silicon semiconductor layer having hydrogen of the first conductivity type and irradiating a portion of the amorphous silicon semiconductor layer having hydrogen of the first conductivity type with laser light; A method for manufacturing a solar cell, wherein a porous silicon semiconductor layer is changed to a microcrystalline silicon semiconductor layer containing hydrogen of a first conductivity type. 6. The method for manufacturing a solar cell according to claim 5 , wherein hydrogen gas is contained in an atmosphere when the laser light is irradiated. 7. The method for manufacturing a solar cell according to claim 5, wherein an atmosphere for irradiating the laser beam contains impurities of a first conductivity type and hydrogen gas. Method.