JPH1126792A - Manufacture of silicon film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a silicon film with no high-temperature condition required by housing a silicate glass in a vessel, making the inside of the vessel to be reducing atmosphere, irradiating the silicate glass with a vacuum ultraviolet light of specific wavelength radiated from a vacuum ultraviolet ray source, and generating a silicon film on the surface of the silicate glass. SOLUTION: Such shape of silicate glass as a glass substrate 21 is allocated, in advance, at a supporting part 20 in a reactive vessel 1, and such a reducing gas as hydrogen gas is introduced from a gas supply part 10, and then, a vacuum ultraviolet light of wavelength 130 nm or shorter which is radiated from a vacuum ultraviolet light source 2 is point-condensed on the surface of silicate glass with condenser mirrors 8a and 8b to form a silicon film. Thanks to the quantum effect of vacuum ultraviolet light in wavelength range of 130 nm or below, SiO2 dissociates to silicon and oxygen, which is to be liberated, so that a silicon film is formed on a glass surface. If a reducing atmosphere is kept under a reducing atmosphere in the vessel at that time, dissociation phenomenon is promoted, so a silicon film is formed on the glass surface at a practical speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a silicon film, and more particularly to a method for forming a silicon (Si) film on the surface of a silicate glass such as quartz glass.

[0002]

2. Description of the Related Art In general, a silicon film is produced from a so-called silica (SiO ₂ ) or silane-based gas.
Si) is produced through many complicated processes such as physical vapor deposition or chemical vapor deposition (CVD) of the obtained silicon on a base surface. In addition, Si for solar cells
At present, the production of simple silicon in a substrate manufacturing process or the like is typically performed by SiO ₂ reduction under a high temperature condition (1100 ° C. or higher) using an electric furnace or the like. For this reason, in the conventional silicon film manufacturing process, manufacturing costs such as power costs tend to be high.
Therefore, in the production of a silicon substrate for a thin-film solar cell by a conventional silicon film production process, a high production cost of the silicon film obtained by the production process is a factor.
The price of solar cells, which are supposed to save energy, has risen or profits have been easily broken. For this reason,
In the field of manufacturing solar cells and other semiconductors, it is desired to develop a silicon film manufacturing process that is inexpensive and does not require complicated processing steps.

[0003] By the way, a group of Prof. Kurosawa and others of Miyazaki University and colleagues reported that silicon and oxygen were dissociated from SiO ₂ by irradiating quartz with vacuum ultraviolet light of a predetermined intensity, and as a result, the quartz surface was damaged. It is reported that silicon particles are formed (K. Kurosawa, Y. Takigawa, W. Sasaki, M. Katto an
d Y. Inoue: Japanese Journal of Applied Physics, V
ol. 30 (1991), pp. 3219-3222).

[0004]

However, according to the method based on the above reported example, a particle diameter of 100 nm
It took more than a week to produce silicon particles of the order, and it was not possible to produce a continuous silicon film as required in solar cells and other semiconductor manufacturing fields.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to provide a method for efficiently producing a silicon film without requiring high-temperature conditions as in the above-mentioned conventional production process. And a method for efficiently manufacturing a semiconductor device such as a solar cell based on the silicon film manufacturing method.

[0006]

In order to achieve the above object, the present invention provides a process for accommodating a silicate glass or an object to be treated having a silicate glass in a container.
A step of reducing the inside of the container to a reducing atmosphere, and a step of irradiating the silicate glass in the container with vacuum ultraviolet light having a wavelength of 130 nm or less emitted from a vacuum ultraviolet light source, whereby the surface of the silicate glass is A silicon film is produced (hereinafter, referred to as “first method for producing a silicon film of the present invention”).

[0007] In this specification, the term "silicate glass" is a general term for silicate glass and silica glass (quartz glass) containing SiO ₂ as a main component. Silica glass to which various dopants (impurities) that can be a so-called p-type semiconductor material or an n-type semiconductor material are added in advance is also included in the silicate glass in this specification.

In the first method for producing a silicon film of the present invention,
130n wavelength on silicate glass in a container with original atmosphere
m or less of vacuum ultraviolet light. According to this method,
Vacuum ultraviolet light in the relevant wavelength range
By the quantum effect of SiO_TwoDissociates into silicon and oxygen
I do. When oxygen generated by the dissociation is released,
In addition, silicon consisting of silicon generated by the dissociation action
A film is formed on the silicate glass surface. At this time,
If the chamber is kept in a reducing atmosphere, vacuum ultraviolet light
SiO _TwoDissociation into silicon and oxygen accelerated
Silicon film on the glass surface at a practical speed.
It is possible to make it.

One preferable method of the first method for producing a silicon film of the present invention is to realize a reducing atmosphere by injecting hydrogen gas into the container. Hydrogen wavelength 13
It transmits vacuum ultraviolet light of 0 nm or less well.

In order to achieve the above object, in another method of the present invention, a silicate glass or an object to be treated having silicate glass is contained in a container, and a vacuum having a wavelength of 130 nm or less emitted from a vacuum ultraviolet light source. A step of condensing at least a part of the ultraviolet light, and a step of irradiating the collected vacuum ultraviolet light to the silicate glass in the container, thereby generating a silicon film on the surface of the silicate glass (Hereinafter, referred to as “second silicon film production method of the present invention”).

In the second method for producing a silicon film of the present invention, similarly to the first method for producing a silicon film, the silicate glass housed in the container is irradiated with vacuum ultraviolet light having a wavelength of 130 nm or less. On the silicate glass surface, the dissociation of SiO ₂ into silicon and oxygen is induced by the quantum effect of the vacuum ultraviolet light in the above wavelength range, and as a result, oxygen is liberated to form a silicon film on the silicate glass surface. At this time, in the second silicon film production method of the present invention,
After condensing the vacuum ultraviolet light in the above wavelength range emitted from the vacuum ultraviolet light source, the silicate glass in the container is irradiated. As a result, the intensity of the vacuum ultraviolet light applied to the silicate glass increases, and a silicon film is efficiently formed on the silicate glass surface. According to the second method, a silicon film can be formed at a practical speed.

The most preferred embodiment of the present invention is to carry out the first and second methods at the same time. The inside of the container is maintained in a reducing atmosphere, and the collected vacuum ultraviolet light is applied thereto. According to the silicon film production method of this aspect, the irradiation efficiency of vacuum ultraviolet light is increased, and the silicon film formation reaction on the silicate glass surface can be further promoted.

In the second method for producing a silicon film according to the present invention, the vacuum ultraviolet light source comprises a focused excitation laser and a target material exposed to the excitation laser. It is preferable to select a material that generates plasma when exposed to the excitation laser and generates vacuum ultraviolet light having a wavelength of 130 nm or less from the plasma.

When the vacuum ultraviolet light source of this mode is used, the area where the vacuum ultraviolet light is generated is narrowed down to a point, and when this area is collected, it can be collected again in a small area. For this reason, the energy density at the focal point increases, and the silicon film formation reaction on the silicate glass surface can be further promoted.

Further, a particularly preferred method of the present invention for producing a silicon film is to locally supply a silane-based fluid and / or silicone oil near the surface of the silicate glass in the container. In the silicon film manufacturing method of this mode, the silicate glass in the container is irradiated with vacuum ultraviolet rays in the above wavelength range, and a silane-based fluid and / or silicone oil is supplied to the irradiated portion. Thereby, not only the silicate glass but also the silane-based fluid and / or silicone oil supplied thereto is irradiated with the vacuum ultraviolet rays. As a result, in addition to silicon generated based on the dissociation of SiO ₂ constituting the silicate glass, silicon is also dissociated as a simple substance from the supplied silane-based fluid and / or silicone oil, and both are combined on the silicate glass surface. A silicon film is formed. Therefore, according to the method of the present invention for producing a silicon film, it is possible to speed up the formation of the silicon film on the silicate glass surface.

According to another aspect of the present invention, there is provided a vacuum ultraviolet light irradiating apparatus for producing a silicon film, comprising the above-mentioned container and the above-mentioned vacuum ultraviolet light source for carrying out the above-mentioned method for producing a silicon film of the present invention. . The method for producing a silicon film of the present invention can be suitably performed by the vacuum ultraviolet light irradiation device of the present invention.

According to the present invention, p-type and n-type silicon films, that is, p-type and n-type silicon layers are formed on the surface of a silicate glass by applying any one of the above-described methods for producing a silicon film of the present invention. It is characterized by the following.
This method is particularly suitable for manufacturing solar cells. In this solar cell manufacturing method, a Si substrate for a pn junction type solar cell can be easily manufactured from a silicon film manufactured by the above-described silicon film manufacturing method. A pn junction solar cell can be easily manufactured without performing a multi-step process.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be typically implemented as follows.

In carrying out the method for producing a silicon film according to the present invention, various containers capable of containing silicate glass (including an object to be treated having silicate glass; the same applies hereinafter), which is a container which can be sealed from the outside air. A container having a shape (hereinafter, referred to as a “reaction container”), and vacuum ultraviolet light of 130 nm or less (that is, an electromagnetic wave having a wavelength of 1 nm to 2 nm connected to X-rays,
Various types of vacuum ultraviolet light sources capable of irradiating (typically 105 nm to 130 nm) can be used. Hereinafter, a preferred embodiment of the method for producing a silicon film of the present invention when a silicon film is formed on the surface of a glass substrate made of quartz or the like will be described with reference to FIG.

FIG. 1 schematically shows a vacuum ultraviolet light irradiation apparatus for carrying out the method for producing a silicon film according to the present invention according to this embodiment. As shown in FIG. 1, in order to carry out the method for producing a silicon film according to the present invention, a reaction vessel 1 sealed with respect to the outside air and vacuum ultraviolet light of 130 nm or less (hereinafter referred to as a A vacuum ultraviolet light source 2 that can irradiate ultraviolet light (hereinafter simply referred to as “vacuum ultraviolet light”) is used.

The vacuum ultraviolet light source 2 used here includes an argon gas (Ar), which is a typical example of a target material (chemical species) capable of emitting vacuum ultraviolet light upon excitation, and the A gas.
The laser beam L for exciting r is supplied, and plasma is generated when exposed to the laser beam L, and the vacuum ultraviolet light generated from the plasma is emitted into the reaction vessel 1. It is a configured light source unit. That is, as schematically shown in FIG. 1, in the vacuum ultraviolet light source 2, Ar is introduced from a jet nozzle 3 connected to an argon gas supply source, and an external laser system (typically Nd ^{3 +} : YAG laser oscillation system). Thus, the laser beam L for Ar excitation emitted from the external laser system is applied to the Ar ejection position of the ejection nozzle 3 in the vacuum ultraviolet light source 2. At this time, as shown in FIG. 1, the vacuum ultraviolet light source 2 is equipped with a lens 4 for focusing the excitation laser light L. For this reason, the Ar excitation laser beam L emitted from the external laser system is used.
Can be applied to the Ar ejection position at the tip of the ejection nozzle 3 after being substantially condensed by the lens 4 (see the laser focal point F in FIG. 1). In the present vacuum ultraviolet light source 2, the excitation laser light L can be focused until the laser focus F at the Ar ejection position becomes about 500 μm in diameter. The Ar gas applied to the excitation laser generates high-temperature plasma, from which vacuum ultraviolet light is emitted. Since the excitation laser is focused, the excitation efficiency of Ar is increased, and high-intensity vacuum ultraviolet light is
Can be generated from Further, the vacuum ultraviolet light is generated in a very narrow range narrowed down in a point shape. Ar continuously supplied from the nozzle 3 to the vacuum ultraviolet light source 2 can be forcibly exhausted to the outside of the light source 2 from an exhaust mechanism (not shown) provided in the light source 2. Thus, the interior of the vacuum ultraviolet light source 2 can be always kept in an Ar atmosphere, and
The internal pressure can be reduced to a level generally called a vacuum state.

Next, the reaction vessel 1 used in this embodiment will be described. The present reaction vessel 1 is an airtight box formed so as to be able to be sealed from the outside air, and as schematically shown in FIG. 1, a window 6 made of magnesium fluoride (MgF ₂ ).
(5 mm in thickness) and is connected to the vacuum ultraviolet light source 2. The magnesium fluoride window 6 is connected to the light source 2
This is provided to introduce the vacuum ultraviolet light radiated from the inside into the reaction vessel 1, and is made of magnesium fluoride in consideration of the transmission performance of the vacuum ultraviolet light.

On the other hand, the inside of the reaction vessel 1 constitutes a reaction chamber for forming a silicon film on the surface of the silicate glass in a step described later, and a support portion 20 for disposing the silicate glass such as a glass substrate 21 is provided. It is provided slidably. Further, the reaction vessel 1 is provided with a gas supply unit 10 for supplying a desired reducing gas from the outside into the reaction chamber. In the present embodiment, the gas supply unit 10 is provided outside. It is connected to a hydrogen gas supply source (not shown). Thus, by introducing hydrogen gas from the gas supply unit 10, the inside of the reaction vessel 1 can be made a hydrogen gas (H ₂ ) atmosphere. The reaction vessel 1 includes an exhaust mechanism (not shown) for forcibly exhausting the hydrogen gas supplied from the gas supply unit 10 into the reaction vessel 1 to the outside of the reaction vessel 1. The hydrogen gas atmosphere in the container 1 can be adjusted to a desired pressure.

Further, the reaction vessel 1 has the support 2
A gas inlet 9 for supplying the above-mentioned silane-based fluid is provided near zero. In the present embodiment, the gas inlet 9 is connected to an external silane gas (typically, monosilane SiH ₄ ) source (not shown). Thereby, a silane gas can be locally supplied to the surface of the silicate glass disposed on the support portion 20.

By the way, inside the reaction vessel 1, the window 6
Vacuum ultraviolet light emitted into the reaction chamber through the support 20
Are provided with condensing mirrors 8a and 8b for condensing light on the surface of the silicate glass disposed at the position. That is, the reflecting surfaces of the converging mirrors 8a and 8b are deposited with gold, and the Ar ejection position at the tip of the ejection nozzle 3 in the vacuum ultraviolet light source 2 (that is, the vacuum ultraviolet light generating portion) and the support portion 20 It is formed so as to match the inner surface shape of an imaginary spheroid having a predetermined portion as two focal points. For this reason, the vacuum ultraviolet light that has reached the reflecting surfaces of the condenser mirrors 8a and 8b with the vacuum ultraviolet light generated at the Ar ejection position, which is one focal point of the imaginary spheroid, is efficiently reflected there, and The light is condensed on a predetermined portion on the support portion 20, which is the other focal point of the spheroid. Thereby, in the present embodiment, as shown in FIG.
Not only the vacuum ultraviolet light that can be directly radiated from the light source 2 to the silicate glass disposed in the reaction vessel 1 through the window 6 but also the amount of vacuum ultraviolet light that cannot be radiated to the silicate glass otherwise is applied to the silicate glass surface. Irradiation can be performed together (see FIG. 1). Further, since the support portion 20 is provided so as to be slidable, the support portion 2 can be slid.
By moving 0, vacuum ultraviolet light can be condensed and applied to a desired position on the silicate glass surface without moving and adjusting the condensing mirrors 8a and 8b. Since the inside of the reaction vessel 1 is in a hydrogen gas atmosphere as a reducing gas, it is possible to prevent deterioration of the condenser mirrors 8a and 8b due to an oxidizing action and the like.

The method for producing a silicon film according to the present invention can be suitably performed by using the vacuum ultraviolet irradiation apparatus having the above-described structure. That is, the support 2 in the reaction vessel 1
0, a silicate glass having a shape such as a glass substrate 21 is arranged in advance, a reducing gas such as hydrogen gas is introduced from the gas supply unit 10, and a vacuum radiated from the vacuum ultraviolet light source 2 is applied to the silicate glass surface. By irradiating the ultraviolet light while converging it with the condensing mirrors 8a and 8b,
A silicon film can be efficiently formed on the surface of the silicate glass at a practical speed. At the same time,
A silane gas (typically, S) is locally applied from the gas inlet 9 to the surface of the silicate glass irradiated with the vacuum ultraviolet light.
By supplying iH ₄ and Si ₂ H ₆ ), formation of a silicon film on the surface of the silicate glass can be promoted.

[0027]

EXAMPLES In the following examples, the method for producing a silicon film of the present invention using the vacuum ultraviolet irradiation apparatus having the above-mentioned structure will be described more specifically, but these will not limit the scope of the claims of the present invention. is not. The method for producing a silicon film of the present invention can be carried out in various modes without using the vacuum ultraviolet irradiation apparatus having the above-described configuration.

(First Embodiment) A quartz glass substrate 21 of 1.5 cm square (about 1 mm thick) as silicate glass is placed on the support section 20 in the reaction vessel 1, and hydrogen gas is supplied from the gas supply section 10. Then, the inside of the reaction vessel 1 was set to a hydrogen gas atmosphere of approximately 1 atm. Next, Ar is supplied to the vacuum ultraviolet light source 2, and the Ar is irradiated with laser light L from the external laser system to generate vacuum ultraviolet light, and the vacuum ultraviolet light is supplied through the window 6 into the reaction vessel 1. To the quartz glass substrate 21.

That is, first, the external laser system emits an Ar-excitation laser beam L having a wavelength of about 1 μm, a pulse width of 8 nanoseconds, and an energy of 1 joule at 10 Hz for 10 minutes (ie, 6000 times in total). I do. Then, the emitted laser light L is focused by the lens 4 so that the laser focus F has a diameter of 500 μm at the ejection position of the tip of the ejection nozzle 3, and the focused laser light L is applied to Ar flowing therethrough. (FIG. 1). At this time, a vacuum ultraviolet light spectrum generated from plasma (a highly ionized state) generated from Ar exposed to the laser light L was measured using a vacuum ultraviolet light spectroscope. The measurement chart is shown in FIG. The horizontal axis in FIG. 2 indicates the wavelength (nm), and the vertical axis indicates the intensity of the analyzed vacuum ultraviolet light for each wavelength in a relative arbitrary unit. As is clear from this chart, in the vacuum ultraviolet light generated from the light source 2 used in the method for manufacturing a silicon film of the present invention under the above-described conditions, a strong line spectrum having wavelengths of 105 nm and 107 nm and a relatively strong line spectrum having wavelengths of 126 nm to 130 nm were obtained. A strong continuous spectrum was observed (see the arrow in the figure).

Next, vacuum ultraviolet light having the above-mentioned spectrum is guided into the reaction vessel 1 through the window 6. At this time, the vacuum ultraviolet light introduced into the reaction vessel 1 is condensed by the condensing mirrors 8a and 8b provided in the reaction vessel 1 as described above, and is then placed on the support section 20. A predetermined position on the quartz glass substrate 21 was irradiated with a point light. In this way, after performing the vacuum ultraviolet light irradiation for 10 minutes in synchronization with the laser light L irradiation, a general so-called X-ray photoelectron spectroscopy (XPS) is applied to the portion of the quartz glass substrate 21 irradiated with the vacuum ultraviolet light. ) An analysis was performed. In this XPS analysis, as a result of observing the electron spectroscopy spectrum of Si-2p and O-1s from the portion (surface) of the quartz glass substrate 21 irradiated with vacuum ultraviolet light, the surface of the quartz glass substrate 21 irradiated with vacuum ultraviolet light showed It was recognized that quartz (SiO ₂ ) was dissociated and a large amount of silicon (Si) was generated instead. Further, as a result of observation with a scanning electron microscope, a silicon film (porous film) having a thickness of about 2 μm was formed on the surface of the quartz glass substrate 21 in the portion irradiated with the vacuum ultraviolet light.
(porous) and a little lacking flatness) was formed.

(Comparative Example) Next, as a comparative example of the first embodiment, neon gas (N
e) was supplied to the vacuum ultraviolet light source 2 to irradiate the quartz glass substrate 21 in the reaction vessel 1 with ultraviolet light, and the deterioration state of the surface of the quartz glass substrate 21 was examined. As in the case of the first embodiment, the quartz glass substrate 21 is arranged, and the vacuum ultraviolet light source 2 is placed in a reaction vessel 1 in a hydrogen gas atmosphere of 1 atm.
Was irradiated with ultraviolet light. That is, the laser beam L was emitted from the external laser system to Ne ejected from the tip of the ejection nozzle 3 under the same conditions as in the first embodiment. Then, a vacuum ultraviolet spectrum generated from the excited Ne was measured using a vacuum ultraviolet light spectroscope. As a result, A
Unlike the case where r is the target material, the wavelength 130
Almost no vacuum ultraviolet light having a high intensity of not more than nm was observed. Instead, high-intensity ultraviolet light having a wavelength of 140 nm to 200 nm was observed (the measurement chart is not shown).

Further, ultraviolet light derived from Ne having the above-mentioned spectrum was focused and irradiated on a predetermined position on the quartz glass substrate 21 in the same manner as in the first embodiment. After completion of the irradiation treatment for 10 minutes, the surface of the quartz glass substrate 21 irradiated with Ne-derived ultraviolet light was observed by XPS analysis and scanning electron microscope in the same manner as in the first embodiment. Such silicon formation was hardly observed.

(Second Embodiment) Next, as a second embodiment of the silicon film manufacturing method of the present invention, a vacuum is applied to the quartz glass substrate 21 while locally supplying monosilane gas (SiH ₄ ) to the surface of the quartz glass substrate 21. An ultraviolet light irradiation treatment was performed. That is, similarly to the first embodiment, the surface of the quartz glass substrate 21 disposed in the reaction vessel 1 was point-focused and irradiated with vacuum ultraviolet light from the vacuum ultraviolet light source 2 (FIG. 1). Here, in this embodiment, SiH ₄ was supplied from the gas inlet 9 at a rate of approximately 100 cc per minute to the vacuum ultraviolet light irradiation site on the surface of the quartz glass substrate 21 in the reaction vessel 1. Further, in the present embodiment, the vacuum ultraviolet light
The SiH ₄ supply process is performed in synchronization with the irradiation process.

That is, as described in the first embodiment, the present vacuum ultraviolet light source 2 has a pulse width of 10
In synchronism with the irradiation of the laser beam L onto Ar at intervals of Hertz, the vacuum ultraviolet light generated there is also intermittently emitted into the reaction vessel 1 at intervals of 10 Hertz. Therefore, a valve is provided in the gas inlet 9, and the valve is operated so as to synchronize with the above-mentioned vacuum ultraviolet light emission interval so that the supply of SiH ₄ is reduced to one.
On / off control is performed at 0 Hertz intervals. In particular,
A timing slightly earlier than the timing at which the vacuum ultraviolet light is radiated from the light source 2 is set as the supply start point of SiH ₄ , and the valve is opened / closed at intervals of 10 Hz from the start point to supply / stop SiH ₄ . This makes it possible to always maintain the SiH ₄ concentration near the surface of the quartz glass substrate 21 at an appropriate level, and to prevent excess SiH ₄ from staying near the surface of the quartz glass substrate 21 during irradiation with vacuum ultraviolet light. To prevent. That is, if excess SiH ₄ stays near the surface of the quartz glass substrate 21, the amount of vacuum ultraviolet rays reaching the surface of the quartz glass substrate 21 may be excessively reduced, which is not a preferable situation. Also,
By supplying SiH ₄ into the container 1 in this manner, S
iH ₄ usage can also be saved.

After performing the vacuum ultraviolet light irradiation treatment for 10 minutes in the same manner as in the first embodiment, the quartz glass substrate 21
The part irradiated with the vacuum ultraviolet light was subjected to XPS analysis and scanning electron microscope observation. As a result, it was confirmed that a larger amount of silicon (Si) was generated on the surface of the quartz glass substrate 21 irradiated with the vacuum ultraviolet light, and a flat silicon film having a thickness of 3 μm or more was formed. That is,
By using the above-mentioned SiH ₄ supply treatment together, the production rate of the silicon film was increased 1.5 times or more, and the practicality of the method for producing a silicon film of the present invention was further enhanced.

Third Embodiment Next, an example in which a solar cell is manufactured by applying the silicon film manufacturing method of the present invention will be described.
As shown in FIG. 3, a quartz glass substrate 22 having a shape obtained by dividing a cylinder in half is disposed on a support portion 20 (FIG. 1) in the reaction vessel 1, and is shown in the first embodiment or the second embodiment. According to the method described above, the flat surface of the quartz glass substrate 22 was subjected to vacuum ultraviolet light irradiation treatment for 60 minutes. At this time, the support portion 20 (that is, the semi-cylindrical quartz glass substrate 22) is reciprocated in the cylindrical axis direction, so that a 2 μm-thick and 1 cm wide strip-shaped silicon film 22a is formed on the flat surface of the quartz glass substrate 22. did. Silicon film 2 thus obtained
When sunlight was incident on the quartz glass substrate 22 with 2a (that is, the Si substrate for solar cells) from the outer peripheral surface of the cylinder, the sunlight was condensed on the silicon film 22a formed as shown in FIG. . That is, by using the silicon film manufacturing method of the present invention, a Si substrate 22 for a thin-film solar cell having good light-collecting efficiency can be formed in a simple process and at a practical speed without performing costly high-temperature conditions or complicated processes. Can be produced. That is, the silicon film is produced on the flat surface of the semi-cylindrical glass substrate 22 (or the dome-shaped glass substrate) as shown in FIG. 4 by the silicon film production method of the present invention. An integrated solar cell capable of efficiently condensing sunlight on a silicon film can be manufactured. Further, the integrated solar cell can also be manufactured by forming a silicon film on a silicate glass having a Fresnel lens shape instead of the semi-cylindrical shape.

In the following fourth to seventh embodiments,
A specific example in which a pn junction type thin film solar cell 30 as shown in FIG. 5 is manufactured by a solar cell manufacturing method characterized by applying the silicon film manufacturing method of the present invention will be described. In these examples, except for the part relating to the implementation of the silicon film manufacturing method of the present invention, all the conventional techniques for manufacturing solar cells or semiconductor devices (for example, etching techniques) are applied. What is obtained is understood by those skilled in the art.

(Fourth Embodiment) A back surface (a lower surface in FIG. 5; the same applies hereinafter) of a silicate glass substrate 24 (FIG. 5) having a thin plate-like borosilicate glass containing boron (B) as a dopant in a surface layer portion is provided. A groove was previously formed by grinding, etching, or the like. Then, silicon having a desired thickness (typically 1 to 100 μm) is formed on the surface (the upper surface in FIG. 5; the same applies hereinafter) of the silicate glass substrate 24 by the method described in the first embodiment or the second embodiment. Films, ie, silicon layers 25 and 26, were produced. However, in this state, the silicon layers 25 and 26 are all p-type. Therefore, next, the silicon layer 25,
Phosphorus (P) was diffused on the surface of the substrate 26 by a known technique such as a thermal diffusion method, thereby forming a thin n-type silicon layer 26 (typically 0.2 to 0.4 μm). This allows
A pn junction is formed in the silicate glass substrate 24.
Next, an anti-reflection film 27 (preferably made of magnesium fluoride, silicon nitride, silicon dioxide, or the like) is formed on the surface of the n-type silicon layer 26 as necessary, and is formed by a normal technique (surface etching, cleaning, etc.). The antireflection film 27 was subjected to a window opening process. Then, a surface grid electrode (+) 32 was formed by a normal vacuum deposition method or the like. On the other hand, the above-described groove on the back surface of the silicate glass substrate 24 was also subjected to an etching treatment, and a back electrode (-) 34 was formed by a vacuum deposition method or the like. As described above, by these series of steps involving the implementation of the silicon film production method of the present invention,
The thin-film solar cell 30 shown in FIG. 5 can be manufactured with a simple process and at a practical speed without performing a high-temperature reduction treatment using an electric furnace or the like as in the conventional solar cell Si substrate manufacturing process.

(Fifth Embodiment) A solar cell 30 as shown in FIG. 5 can also be manufactured as follows. That is, the silicate glass substrate 24 made of quartz
A groove was previously formed on the back surface by grinding, etching, or the like. Then, a silicon film having a desired thickness (typically 1 to 100 μm), that is, silicon layers 25 and 26 was formed on the surface of the silicate glass substrate 24 by the method described in the first embodiment or the second embodiment. . Next, in order to make the generated silicon layers 25 and 26 p-type, a p-type dopant such as boron was doped (added) to the generated silicon layers 25 and 26 by an ordinary ion implantation method or the like. However, in this state, since the silicon layers 25 and 26 are all p-type, next, phosphorus is diffused into the surfaces of the silicon layers 25 and 26 by a known technique such as a thermal diffusion method to form a thin n-type silicon layer. 26 (typically 0.2-0.4 μm). As a result, a pn junction is formed in the silicate glass substrate 24. Next, by performing the same processing as in the fourth embodiment, the thin-film solar cell 30 shown in FIG. 5 was manufactured.

(Sixth Embodiment) The thin-film solar cell 30 shown in FIG. 5 can also be manufactured as follows. That is, instead of the silicate glass substrate 24 used in the fourth and fifth embodiments, a two-layer structure in which the surface layer is a phosphorus silicate glass containing phosphorus and the lower layer is a borosilicate glass containing boron is used. Was used. Thus, similarly to the fourth embodiment, grooves were previously formed on the back surface of the silicate glass substrate 24 by grinding, etching, or the like. Then, silicon layers 25 and 26 were formed on the surface layer of the silicate glass substrate 24 by the method described in the first embodiment or the second embodiment. In this case, of the generated silicon layers 25 and 26, the silicon layer 26 in the surface layer is n-type, and the silicon layer 25 in the lower layer is p-type. That is, in the present embodiment, a pn junction can be directly formed by implementing the method for manufacturing a silicon film of the present invention. Next, by performing the same processing as in the fourth embodiment, the thin-film solar cell 30 shown in FIG. 5 was manufactured. Note that the silicate glass substrate 24 having the two-layer structure is obtained by forming a quartz glass substrate (that is, a substrate containing no dopant that can affect the electric conductivity of Si) by adding boron and then phosphorus by an ion implantation method or a thermal diffusion method. It can be produced by doping by a known technique. Alternatively, the silicate glass substrate 2 having the two-layer structure may be formed by diffusing phosphorus into the surface of a boron-containing borosilicate glass by a known technique such as a thermal diffusion method.
4 can be prepared in advance before the silicon film manufacturing method of the present invention is carried out.

(Seventh Embodiment) The fourth to sixth embodiments are described as follows.
In each case, the n-type silicon layer 26 was formed on the surface layer and the p-type silicon layer 25 was formed immediately below the surface layer.
The p-type silicon layer 26 may be formed on the surface layer, and the n-type silicon layer 25 may be formed directly below the p-type silicon layer 26. Even in this case,
Except that the order of forming the p-type silicon layer and the n-type silicon layer is reversed, it is manufactured basically according to the fourth to sixth embodiments.

In the preferred embodiments and examples of the present invention described above, the method of manufacturing a silicon film of the present invention was carried out by the vacuum ultraviolet light irradiation apparatus (FIG. 1). In carrying out the film manufacturing method, the use of the apparatus having the above configuration is not essential. For example, the vacuum ultraviolet light source at the time of carrying out the silicon film production method of the present invention is not limited to the one using the above-mentioned excitation laser light L, but discharges in a vacuum vessel, atoms or molecules by means of microwaves or the like. Is used as a vacuum ultraviolet light source when implementing the silicon film manufacturing method of the present invention, as long as it can realize an excitation (or ionization) level of the compound and can generate and emit vacuum ultraviolet light based on a transition from the level. obtain. For example, an electron beam pumped excimer laser or the like can be suitably used. In the vacuum ultraviolet light irradiation device, the reaction vessel 1 and the light source 2 are separately configured via the window 6 made of magnesium fluoride. However, the present invention is not limited to this. For example, a vacuum ultraviolet light source is provided in the reaction vessel. An integrated vacuum ultraviolet light irradiation device may be configured.

In the above embodiment and the second embodiment, a monosilane gas (or disilane gas) is employed as the silane-based gas or silicone oil to be supplied into the reaction vessel 1, and the gas is introduced from the gas inlet 9 into the support section. 20 is supplied to a predetermined position, but is not limited to this. Other silane gas (silicon hydride) or silicon halide (preferably silicon fluoride (Si
F ₄ )) or dichlorosilane (SiCl ₂ H ₂ )
And the like, and a fluid compound of silicon, hydrogen and a halogen element. Alternatively, polydimethylsiloxane,
Silicone oils having alkyl, aryl or derivatives thereof, such as pentaphenyltrisiloxane, may be provided.

The means for setting the inside of the reaction vessel 1 to a reducing atmosphere may be replaced by introducing a reducing gas such as hydrogen gas directly into the vessel as described above, and then introducing a reducing gas into the reaction vessel 1 and then introducing a vacuum. Alternatively, a means for introducing a liquid medium such as silicone oil capable of generating a reducing gas upon irradiation with ultraviolet light into the container may be used.

[0045]

According to the present invention, a silicon film can be manufactured at a simple process and at a practical speed without requiring high-temperature conditions as in the conventional manufacturing process.

Further, according to the first method for producing a silicon film of the present invention, the inside of the container is set to a reducing atmosphere. This can promote the silicon film formation reaction on the silicate glass surface.

According to the second method for producing a silicon film of the present invention, the vacuum ultraviolet light emitted from the vacuum ultraviolet light source is condensed and then irradiated onto the silicate glass disposed in the container. Thus, not only the vacuum ultraviolet light that can be directly irradiated from the light source to the silicate glass, but also the amount of vacuum ultraviolet light that cannot be normally irradiated to the silicate glass can be irradiated to the silicate glass surface. For this reason, the intensity of the vacuum ultraviolet light applied to the silicate glass can be increased, and the silicon film formation reaction on the silicate glass surface can be promoted.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a vacuum ultraviolet irradiation apparatus for performing a silicon film manufacturing method of the present invention.

FIG. 2 is a graph showing a vacuum ultraviolet light spectrum from Ar excited by laser light.

FIG. 3 is an explanatory view showing the formation of a silicon film on the surface of a semi-cylindrical silicate glass by the method for producing a silicon film of the present invention.

FIG. 4 is an explanatory diagram showing a state of condensing sunlight on a semi-cylindrical Si substrate obtained by the method for producing a silicon film of the present invention.

FIG. 5 is a schematic view showing the appearance of a thin-film solar cell obtained by the method for producing a silicon film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reaction container 2 Vacuum ultraviolet light source 3 Blow-out nozzle 4 Lens 6 Window 8a, 8b Condensing mirror 9 Gas inlet 10 Gas supply unit 20 Support unit 21, 22, 24 Glass substrate 25, 26 Silicon layer 27 Anti-reflection film 30 Solar cell 32 Front grid electrode 34 Back electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tomomi Motohiro 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. 41 No. 1, Yokomichi, Chuchu, Toyota Central Research Institute, Inc.

Claims (2)

[Claims] 1. A method for producing a silicon film, comprising: a step of containing a silicate glass or an object to be treated having a silicate glass in a container; a step of setting the inside of the container to a reducing atmosphere; Wavelength 1
Irradiating the silicate glass in the container with vacuum ultraviolet light of 30 nm or less; and forming a silicon film on the surface of the silicate glass. 2. A method for producing a silicon film, comprising: a step of housing a silicate glass or an object to be treated having a silicate glass in a container; at least one of vacuum ultraviolet light having a wavelength of 130 nm or less emitted from a vacuum ultraviolet light source. Condensing a portion; and irradiating the collected silicate glass in the container with the collected vacuum ultraviolet light; and forming a silicon film on the surface of the silicate glass. Production method.