JPH11340486A - P-n junction and method for forming reaction product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a titanium oxide containing phosphorus, wherein a high- quality p-n junction and an antireflection film are formed at the same time, and to provide a solar cell with few number of processes, while being suited to modularity for lower cost and improved cell characteristics. SOLUTION: A crystalline silicon substrate of p-type conductive type is heated, and oxygen, gaseous titanium compound, and gaseous phosphorus compound are supplied to the substrate, which are oxidating decomposed to obtain a reaction product, which is thermally treated in an inert gas to form an n-layer and an antireflection film, and the supply amount ratio between the gaseous titanium compound and the gaseous phosphorus compound is changed to provide a reaction product, comprising a phosphorus-containing titanium oxide of a composition ratio 0.1-1.5 (phosphorus/titanium). A p-n junction and an antireflection film for a crystalline silicon solar cell are formed at the same time, with a sheet resistance value of n-layer on the silicon substrate side being 100 Ω/square or less, while a refractive index of the antireflection film being 2.2-2.7, resulting in a antireflection film for a solar cell, suitable for modularity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a pn junction and a reaction product of a crystalline silicon solar cell.

[0002]

2. Description of the Related Art A process shown in FIG. 3 is known as a method for forming a pn junction and an antireflection film of a crystalline silicon solar cell. A p-type crystalline silicon substrate having a texture structure formed on its surface is placed in a quartz tube heated to about 800 to 1100 ° C. A liquid impurity source such as POCl ₃ contained in a bubbler container is introduced into the quartz tube with a carrier gas such as N ₂ . Thus, a phosphorus oxide layer is formed on both surfaces of the substrate as a diffusion source. At the same time, phosphorus is diffused from the phosphorus oxide layer into the substrate to form a pn junction (S102).

After the diffusion step, an oxide film containing phosphorus as a main component having a hygroscopic property remains on the surface of the substrate.
It is removed using F (S103). Thereafter, an anti-reflection film is formed on the substrate surface side portion to further reduce surface reflection (S104). As the anti-reflection film at this time, a TiO ₂ film formed by using a normal pressure CVD (chemical vapor deposition) method, a SiN _x film formed by using a plasma CVD method, or the like is used.

For example, when a TiO ₂ film is formed by a normal pressure CVD method, a carrier gas such as N _{2 is} fed into a bubbler containing titanium alkoxide and water. Each of these materials is carried to the substrate surface by these carrier gases, and a hydrolysis reaction is caused on the substrate surface to deposit a TiO ₂ film.
The normal pressure CV at which the antireflection film can be formed
As the D apparatus, Watkins-Johnson Company (Watkins-Jo
hnson Co.) or BTU International (BTU)
International) a normal atmospheric pressure CVD apparatus has been commercialized.

In addition, the P used for forming the pn junction described above is
Instead of diffusing OCl ₃ , as shown in FIG.
There is also known a process of depositing SG (Phosphosilcate Glass, which is obtained by doping SiO ₂ with phosphorus or the like) and using this as a diffusion source. First, a PSG film is formed on the surface of the p-type crystalline silicon substrate (S202). Subsequently, by heating to about 800 to 1100 ° C., the PSG
Phosphorus is diffused from the film to form a pn junction on the substrate surface (S203). A typical method of forming a PSG film is as follows.

A method of applying a coating liquid comprising an organosilicon compound, an organic solvent and a phosphorus compound; a CVD method using SiH ₄ , PH ₃ and O ₂ or N ₂ O; a SiH ₄ , an organic phosphorus compound and O C using CVD method using _2, a _{· Si (OC 2 H 5)} 4 and the organic phosphorus compound and O ₂
VD method However, the PSG film remaining on the substrate surface after this diffusion step is not suitable as an anti-reflection film because its refractive index is about 1.4 to 1.5. Then, after removing this PSG film with HF (S204), an anti-reflection film such as TiO ₂ or SiN _x is formed on the substrate surface (S205).

For example, as shown in Japanese Patent Application Laid-Open No. 54-76629, the two processes shown in FIGS. 3 and 4 are simplified, and a pn junction and reflection are performed using a coating solution as shown in FIG. There is known a process for simultaneously forming a protective film. A titanium oxide film containing a pn junction dopant having a conductivity type different from that of the substrate is formed on the surface of the p or n-type crystal silicon substrate (S302). Subsequently, by heating to about 800 to 1100 ° C., a pn junction is formed on the surface of the substrate, and at the same time, an antireflection film made of a titanium oxide film containing a pn junction dopant is formed (S303). When the light receiving surface of the solar cell is in direct contact with air, the optimum refractive index of the antireflection film is 1.8 to
2.0. The titanium oxide film containing the pn junction dopant after the heat treatment has low hygroscopicity and a refractive index of about 1.7 to 2.
0.

Therefore, it can be used as it is as an antireflection film. The coating solution used in the process shown in FIG. 5 is made of a titanium alkoxide such as tetraisopropoxytitanium, a compound containing a pn junction dopant element such as phosphorus or boron, and a carboxylic acid or alcohol.

The coating on the surface of the p-type or n-type crystalline silicon substrate is performed by spin coating, dipping or spraying. As an example of an antireflection film formed from such a coating solution, JP-A-56-60075 discloses an antireflection film when the B ₂ O ₃ content in the film is changed from 10% by weight to 50% by weight. When the refractive index of the film changes from about 2.5 to about 2.0, and when the B ₂ O ₃ content is 30% by weight or more, the heat treatment at the same temperature saturates the carrier concentration and the junction depth. It has been shown.

Further, in Japanese Patent Application Laid-Open No. 8-85874, a process for forming a titanium oxide film containing phosphorus on the surface of a p-type crystalline silicon substrate by using a normal pressure CVD method instead of the above-mentioned coating method has been found. ing. In this case, a carrier gas such as N _{2 is} fed into a bubbler containing a titanium alkoxide and an organic phosphorus compound. That is, about 200
Each raw material is carried by a carrier gas to the substrate surface side heated to about 450 ° C., and a vapor phase thermal decomposition reaction is caused on the substrate surface to deposit a phosphorus-containing titanium oxide film. Subsequently, by heating to about 800 to 1000 ° C., a pn junction is formed on the substrate surface, and at the same time, an antireflection film made of a titanium oxide film containing phosphorus is formed.

FIG. 2 shows the sheet resistance of the silicon substrate surface and the refractive index of the film with respect to the substrate temperature during film formation. Since the refractive index of this film is about 1.6 to 2.0, it can be used as it is as an antireflection film when the light receiving surface of the solar cell is in direct contact with air. Thereafter, a back surface electrode and a light receiving surface electrode are formed in the same manner as in the processes of FIGS.
6, S107, S206, S207, S304, S30
5).

[0012]

One of the causes of the high cost of the solar cell is that it has disadvantages such as a large number of manufacturing steps and poor work efficiency as shown in FIGS. . In the method of FIG. 3, since diffusion is performed on both surfaces of the substrate,
It is necessary to remove the n-layer formed on the back surface after diffusion.
In the method of FIG. 4, it is necessary to form an anti-reflection film after forming a pn junction and removing the PSG film on the substrate surface.

As a means for solving these disadvantages at once, a process of forming a titanium oxide film containing a pn junction dopant from a coating solution as shown in FIG. 5 has been found.
However, as shown in FIG.
Crystalline silicon substrate 1 with fine irregularities of several tens of μm
, The following problem arises.

When the coating liquid 2 is applied to the substrate by the spin coating method or the dipping method, the coating liquid is accumulated on the concave portions 1a on the surface of the substrate, and becomes thicker on the convex portions 1b. As in the case of application by the spray method, since the size of the spray particles is several hundred μm, the application liquid is accumulated on the concave portion 1a on the substrate surface and becomes thicker, while the coating liquid becomes thinner on the convex portion 1b. Therefore, the thickness of the antireflection film formed from the above coating solution through heat treatment becomes non-uniform.

In general, the refractive index of a substance surrounding a solar cell is n ₀ (for example, n ₀ = 1 in air), the refractive index of silicon is n _s (about 3.5 to _4.0 ), and an antireflection film is used. the refractive index n, if the thickness of the antireflection film is d, the wavelength of the incident light lambda, an antireflection film so as to satisfy n ² = n ₀ · n _s and 4nd = lambda the condition of It is desirable. That is, in this case, the surface reflectance at the wavelength λ can be minimized. However, when the thickness of the anti-reflection film is not uniform as described above, this condition cannot be satisfied on the entire surface of the substrate, so that surface reflection cannot be reduced sufficiently.

FIG. 7 shows a surface of a solar cell (conventional example 1) manufactured by forming a pn junction in accordance with the process of FIG. 3 and then forming an anti-reflection film (titanium oxide film) using a normal pressure CVD method. A solar cell manufactured by spin-coating a coating solution of a titanium oxide film containing a pn junction dopant according to the reflectance and the process of FIG. 5 and then simultaneously forming a pn junction and an antireflection film (conventional example) 2) shows the surface reflectance. In Conventional Example 1, a minimum value of the reflectance is observed around a wavelength of 600 nm. However, in the conventional example 2, a clear minimum value of the reflectance is not seen. This indicates that the thickness of the antireflection film of Conventional Example 2 is non-uniform.

The light-receiving surface of the solar cell of Conventional Example 1 looks blue due to the interference effect of the antireflection film, whereas the light-receiving surface of the solar cell of Conventional Example 2 remains the ground color (gray) of the silicon substrate. Yes, it is clear that there is no interference effect. As a result, a solar cell manufactured by a process of simultaneously forming a pn junction and an antireflection film using a coating liquid (conventional example 2)
Has a problem that the short-circuit current is lower than that of a solar cell (conventional example 1) in which an anti-reflection film having a uniform film thickness is formed by a CVD method or the like.

Therefore, instead of the coating solution shown in FIG.
When a titanium oxide film containing phosphorus was formed by using the VD method, it was possible to form an antireflection film having a uniform thickness and an interference effect and a pn junction capable of functioning as a solar cell. However, as a pn junction that can function as a solar cell,
Sheet resistance value of silicon substrate surface is 30-100Ω / □
And the refractive index of the antireflection film formed simultaneously when the refractive index has a value of 1.5 to 2.0.

When this solar cell has a module structure, light is applied to the glass and the filler (n = 1.2) because glass is attached to the solar cell with a filler (generally, ethylene vinyl acetate is used). Go through 5)
Absorbed by the silicon substrate. In this case, in order to maximize the anti-reflection effect, the refractive index of the anti-reflection film needs to be about 2.5, and when the anti-reflection effect is 1.5 to 2.0, the anti-reflection effect becomes small.

Therefore, it is necessary to uniformly deposit a Si ₃ N ₄ film or a TiO ₂ film having a higher refractive index on the titanium oxide film containing phosphorus by a CVD method or the like. Further, in the process of FIG. 5, since the underlying titanium oxide film was not uniform in film thickness, a favorable antireflection film exhibiting an interference effect could not be obtained.

An object of the present invention is to provide a phosphorus-containing titanium oxide capable of simultaneously forming a high-quality pn junction and an antireflection film in order to enable a simple process with a small number of steps. It is still another object of the present invention to provide a solar cell which is reduced in cost and has improved cell characteristics. Another object of the present invention is to provide a solar cell suitable for modularization by a simple process with a small number of steps.

[0022]

According to a first aspect of the present invention, a crystalline silicon substrate having a p-type conductivity is heated to a predetermined temperature, and oxygen is added to the substrate. And a gaseous titanium compound and a gaseous phosphorus compound, and oxidatively decompose them to obtain a reaction product. Further, the reaction product is heat-treated in an inert gas to prevent reflection. In the method of forming a reaction product for forming a film, by changing the supply ratio of the titanium compound in the gaseous state and the phosphorus compound in the gaseous state,
The composition ratio (atomic number ratio) of phosphorus to titanium is 0.1 to
A method for forming a pn junction and a reaction product, characterized in that a film is formed to have a thickness of 1.5.

According to a second aspect of the present invention, the refractive index of the antireflection film is set to 2.2 by changing a supply ratio of the titanium compound in the gaseous state and the phosphorus compound in the gaseous state.
To 2.7 and the sheet resistance of the n-layer is 100 Ω /
□ A method for forming a pn junction and a reaction product, characterized in that:

According to a third aspect of the present invention, there is provided the method of forming a pn junction and a reaction product according to the first aspect, wherein the oxidative decomposition at a predetermined temperature on the substrate is performed at 300 to 600 ° C.

According to a fourth aspect of the present invention, there is provided a method of forming a pn junction and a reaction product, wherein the heat treatment is performed in an inert gas at 600 to 1200 ° C. is there.

According to a fifth aspect of the present invention, there is provided the method for forming a pn junction and a reaction product according to the fourth aspect, wherein the heat treatment is performed at 740 ° C. or higher in an inert gas of the reaction product. .

That is, according to the present invention, p
Oxygen, a phosphorus compound in a gaseous state, and a titanium compound in a gaseous state are supplied on a type crystal silicon substrate by a carrier gas. In order to achieve the above object, the molar ratio of phosphorus / titanium in the reaction product should be 0.1 to 0.1.
By controlling the temperature to 1.5 and heat-treating the reaction product at 600 to 1200 ° C. (preferably at 740 ° C. or higher), phosphorus is diffused into the substrate to form a pn junction and simultaneously form an antireflection film. The pn formed in this manner
The bonding has a sheet resistance value of 100Ω / □ or less on the surface of the silicon substrate. Since the antireflection film is formed by a vapor phase method, the film thickness is uniform, exhibits an interference effect, and has a refractive index of 2. It has a value of 2 to 2.7 and solves the above problem.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method for forming an antireflection film according to the present invention will be described in detail. The formation of the phosphorus-containing titanium oxide film which is the antireflection film of the present invention is performed as follows.

The temperature of the bubbler vessel containing the phosphorus compound is maintained at about 40-100 ° C. The carrier N ₂ gas is supplied to the carrier gas supply pipe, the phosphorus compound is contained in the carrier N ₂ gas up to a partial pressure corresponding to the vapor pressure, and supplied to the gas supply pipe through the phosphorus compound supply pipe.

On the other hand, the temperature of the bubbler container containing the titanium compound is maintained at about 70 to 120 ° C. The N ₂ carrier gas is supplied to the carrier gas supply pipe, the titanium compound is contained in the N ₂ carrier gas to a partial pressure according to the vapor pressure, and supplied to the gas supply pipe through the titanium compound supply pipe.

Further, N ₂ gas and O ₂ gas are supplied to the atmosphere gas supply pipe as the atmosphere gas. All these gases are supplied to the substrate surface on the heater block through a gas supply pipe and a gas distribution head. The gas reaction system is an open system at normal pressure.

Next, a p-type crystalline silicon substrate is mounted on the heater block. 300 substrates with heater block
Heating is performed in the range of 〜600 ° C., and when the substrate temperature becomes constant, supply of the source gas through the gas supply pipe is started. Thus, after forming a reaction product composed of a titanium oxide film containing phosphorus, heat treatment is performed in an N ₂ atmosphere to simultaneously form a pn junction and an antireflection film. As the carrier gas not only the N _2, it is possible to use an inert gas such as He or Ar.

Examples of the phosphorus compound include phosphoric acid esters (eg, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, tributyl phosphate, etc.) and phosphites (eg, phosphorus phosphite) which are liquid at ordinary temperature. Diethyl phosphite, trimethyl phosphite, triethyl phosphite, tripropyl phosphite, triisopropyl phosphite, tributyl phosphite, etc.), triethoxy phosphorus, trimethoxy phosphorus and the like.

Examples of the titanium compound include titanium alkoxides which are liquid at room temperature, for example, tetraethoxytitanium, tetrapropoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium, tetraisobutoxytitanium, tetrasecondary butoxytitanium, tetratertiary butoxytitanium and the like. Can be used.

The setting of the temperature of the bubbler vessel is related to the vapor pressure of the compound. That is, since the gas reaction system is open and at normal pressure, the compound is transferred to the carrier N up to a partial pressure corresponding to the vapor pressure.
_{This is because the} gas is contained in the _two gases and supplied to the gas supply pipe through the compound supply pipe.

The composition ratio (atomic ratio of phosphorus / titanium) in the titanium oxide film containing phosphorus can be controlled by adjusting the supply amounts of the phosphorus and titanium compounds. The supply amounts of the phosphorus and titanium compounds can be precisely controlled by controlling the vapor pressure by the set temperature of the bubbler container or by changing the flow rate of the carrier gas passed through the bubbler container.

The control of the substrate temperature affects the following reaction system. The gaseous phosphorus compound and titanium compound supplied to the substrate surface are thermally decomposed and thermally oxidized at or near the substrate surface. Therefore, the phosphorus compound becomes
The titanium compound becomes titanium oxide. The phosphorus oxide and the titanium oxide form a network, and a titanium oxide film containing phosphorus is formed on the surface of the substrate. For this reason, it is necessary to control the substrate in the range of 300 to 600C. As a result, the formed phosphorus-containing titanium oxide film has improved thickness uniformity, and the composition ratio of phosphorus / titanium in the film can be arbitrarily adjusted by adjusting the supply amounts of phosphorus and a titanium compound at a predetermined substrate temperature. Can be changed.

The heat treatment temperature is 600 to 12 in an N ₂ atmosphere.
The reaction is performed at 00 ° C. (preferably 740 ° C. or higher) for 10 minutes to 2 hours. This is because phosphorus in the titanium oxide film containing phosphorus diffuses into the p-type silicon substrate to form a pn junction operable as a solar cell.

[0039]

The present invention will be described in more detail with reference to the following examples.

The temperature of the bubbler vessel containing diethyl phosphite as a phosphorus compound is maintained at two temperatures of 65 and 75 ° C. The carrier N ₂ gas is supplied to the carrier gas supply pipe while changing the flow rate within a range of 1.0 to 10.0 l / min, and diethyl phosphite is contained in the carrier N ₂ gas up to a partial pressure corresponding to each vapor pressure. Let

On the other hand, the temperature of a bubbler container containing titanium tetraisopropoxide as a titanium compound was set to 100 ° C.
To keep. A carrier N ₂ gas is supplied to the carrier gas supply pipe at a flow rate of 1.5 l / min, and titanium tetraisopropoxide is contained in the carrier N ₂ gas to a partial pressure corresponding to the vapor pressure. By supplying these to the gas supply pipe, the supply amount of the phosphorus compound was changed. Further, N ₂ is supplied to the atmosphere gas supply pipe at a flow rate of 4.0 l / min and O ₂ is supplied at a flow rate of 7.0 l / min as the atmosphere gas.

The substrate temperature is set to 35 by the heater block.
A film forming experiment was performed in which the temperature was set to four different temperatures of 0, 375, 400, and 450 ° C. to change the phosphorus concentration in the titanium oxide film. Formed film, 900 in all N ₂ atmosphere
A heat treatment was performed at 30 ° C. for 30 minutes to form a pn junction on the silicon substrate.

The composition ratio of the antireflection film is ESCA (Electron
spectroscopy for chemical analysis) and EDS
(Energy Dispercive Spectrometer). The refractive index of the antireflection film was measured with an ellipsometer. The sheet resistance was measured by a four-probe method after dissolving a titanium oxide film containing phosphorus with hot concentrated sulfuric acid.

FIG. 1 shows the refractive index of the phosphorus-containing titanium oxide film and the sheet resistance of the n-layer with respect to the phosphorus / titanium composition ratio. As the phosphorus / titanium composition ratio increases from 0 to 2.5, the refractive index changes from 2.7 to 1.6, and the phosphorus / titanium ratio increases.
It became clear that the refractive index became 2.2 or more when the composition ratio of titanium was 1.5 or less.

In the region where the composition ratio of phosphorus / titanium is 0.05 or less, the conductivity type of the silicon substrate surface is p-type, and it is clear that no pn junction is formed.

In the region where the molar ratio is 0.05 or more, n-type is exhibited, and as the phosphorus / titanium composition ratio increases from 0.1 to 1.0, the sheet resistance increases from 100 Ω / □ to 30 Ω /
Changed to □.

As described above, the phosphorus / titanium molar ratio is 0.1
A pn junction can be formed in the range of 1.0 to 1.0, and the refractive index is 2.
It can be seen that it has a value of 2 to 2.7.

The relationship between the phosphorus / titanium composition ratio and the refractive index of the phosphorus-containing titanium oxide film shown in FIG. 1 is considered as follows. When the composition ratio of phosphorus / titanium is in the range of 0 to 1.0, the refractive index is 2.5 or more. In this region, it is considered that phosphorus in the film does not affect the crystal structure of titanium oxide. Titanium oxide is considered to be TiO _2, and is known to exhibit a rutile-type crystal structure when heat-treated at 740 ° C. or higher. The refractive index of rutile TiO ₂ is 2.5 to 2.7. The phosphorus-containing titanium oxide shown in FIG. 1 is subjected to a heat treatment at 900 ° C. Therefore, it is considered that the rutile crystal structure affects the refractive index.

When the composition ratio of phosphorus / titanium is from 1.0 to 2.0
In, the refractive index changes from 2.5 to 1.7. In this region, the crystal structure of titanium oxide in the film is affected by phosphorus, and the portion where the ternary network of P-Ti-O is assembled and the portion having the rutile structure are changed according to the phosphorus / titanium molar ratio. This causes a large change in the refractive index. When the phosphorus / titanium molar ratio is 2.0 or more, P-Ti
It is considered that the -O ternary network occupies a large part, and no large change in the refractive index is observed. Finally,
The difference and effectiveness of the present invention with respect to Japanese Patent Application Laid-Open No. 8-85874 will be described. Since the PTG film (anti-reflection film) formed in the present invention has a refractive index of about 2.5 after the heat treatment, it can be used for a solar cell without further special treatment. On the other hand, Japanese Patent Application Laid-Open No. 8-85874
Is disclosed in Japanese Patent Application Laid-Open Publication No. H11-27139, after a PTG film is formed and heat-treated.
A TiO ₂ film is formed on the PTG film. Therefore, it has a structure of TiO ₂ on PTG on Si. Therefore, the cell structure is greatly different from that described in the above publication. In the present invention, unlike the above publication, P
Since there is no need to form a TiO ₂ film on the TG film by the AP-CVD method, cost reduction can be achieved. Further, since the refractive index of the TiO ₂ film can be set to about 2.5,
The TG film suppresses surface loss due to reflection, and can also improve cell characteristics.

[0050]

By using the phosphorus-containing titanium oxide having a phosphorus / titanium composition ratio of 0.1 to 1.5 according to the present invention, the sheet resistance value of the n-layer as a pn junction of the crystalline silicon solar cell is 30 to 30. 100Ω / □ and refractive index 2.2
As a result, it is possible to simultaneously form the antireflection films of 2.7 to 2.7, and to provide a solar cell suitable for modularization.

Further, as compared with the method of simultaneously forming a pn junction and a titanium oxide film using a coating solution, a titanium oxide having a uniform film thickness can be obtained, so that an antireflection film exhibiting a good interference effect can be obtained. . Therefore, the manufacturing process is very simplified and it can be produced at low cost, so its industrial significance is very large.

[Brief description of the drawings]

FIG. 1 is a view showing a refractive index with respect to a phosphorus / titanium composition ratio in a phosphorus-containing titanium oxide film of the present invention and a sheet resistance value of an n-layer with respect to a phosphorus / titanium ratio in the film.

FIG. 2 is a diagram showing a sheet resistance value of an n-layer with respect to a refractive index with respect to a substrate temperature and a phosphorus / titanium composition ratio in a film when a conventional titanium oxide film containing phosphorus is formed.

FIG. 3 is a flowchart showing a conventional solar cell manufacturing process.

FIG. 4 is a flowchart showing another conventional solar cell manufacturing process.

FIG. 5 is a flowchart showing another conventional solar cell manufacturing process.

FIG. 6 is a diagram showing a state where a titanium oxide film containing a pn junction dopant is formed on a substrate surface having irregularities using a coating solution.

FIG. 7 is a view showing the surface reflectance of the solar cells of FIGS. 3 and 5;

[Explanation of symbols]

 1 Crystalline silicon substrate 2 Coating liquid

Claims (5)

[Claims] 1. A crystalline silicon substrate having a p-type conductivity is heated to a predetermined temperature, and oxygen and
A titanium compound in a gaseous state and a phosphorus compound in a gaseous state are supplied and oxidatively decomposed to obtain a reaction product. The reaction product is further heat-treated in an inert gas to obtain an n-layer and a reflection layer. In the method of forming a reaction product for forming the prevention film, the composition ratio (atomic ratio) of phosphorus to titanium is 1 by changing the supply ratio of the titanium compound in the gaseous state and the phosphorus compound in the gaseous state. : A method for forming a pn junction and a reaction product, wherein a film is formed to have a thickness of 0.1 to 1.5. 2. By changing the supply ratio of the titanium compound in the gaseous state and the phosphorus compound in the gaseous state,
A method for forming a pn junction and a reaction product, wherein the antireflection film has a refractive index of 2.2 to 2.7 and a sheet resistance of the n-layer is 100 Ω / □ or less. 3. The method according to claim 1, wherein the oxidative decomposition at a predetermined temperature on the substrate is performed at 300 to 600 ° C.
The method for forming a pn junction and a reaction product according to the above. 4. The method for forming a pn junction and a reaction product according to claim 1, wherein the heat treatment is performed at 600 to 1200 ° C. in an inert gas of the reaction product. 5. The method for forming a pn junction and a reaction product according to claim 4, wherein the heat treatment is performed in an inert gas of the reaction product at 740 ° C. or higher.