JP2022094878A - Apparatus and method for manufacturing thin plate-like single crystal - Google Patents

Abstract

To provide an apparatus and method for manufacturing a thin plate-like single crystal, capable of continuously manufacturing a thin plate-like single crystal having uniform additive concentration at the optimum composition even in a harmonic melt besides the single crystal of a decomposition melt or a solid solution material and having a thickness of several hundred μm at a low cost with high accuracy.SOLUTION: An apparatus for manufacturing a thin plate-like single crystal includes: infrared irradiation means for irradiating the upper side surface of a raw material lump for manufacturing a thin plate-like single crystal with infrared to melt the upper side surface; and lifting means for dipping the lower side surface of a thin plate-like seed single crystal into the melt melted by the infrared irradiation means and obtained on the upper side surface and pulling the thin plate-like seed single crystal upward from the dipped state. The growth of a single crystal is started from the lower side surface of the dipped thin plate-like seed single crystal by dipping the lower side surface of the thin plate-like seed single crystal into the melt obtained on the upper side surface of the raw material lump for manufacturing the thin plate-like single crystal by the infrared irradiation means through the lifting means, and a thin plate-like single crystal is continuously manufactured by pulling the thin plate-like seed single crystal upward through the lifting means.SELECTED DRAWING: Figure 1

Description

The present invention relates to a thin plate-shaped single crystal manufacturing apparatus and a thin plate-shaped single crystal manufacturing method capable of continuously manufacturing a thin plate-shaped single crystal having a thickness of about several hundred μm.

In recent years, the conversion from fossil fuels to renewable energy has been called for, and the conversion from oil-consuming power generation methods to solar power generation methods using solar cells is progressing on a global scale. However, the power generation cost of photovoltaic power generation is still higher than that of other power generation methods, and the development of highly efficient and inexpensive solar cells is desired.

Various materials such as semiconductor silicon crystals, amorphous silicon, and compound semiconductor crystals are known as substrate materials constituting solar cells, and development is underway for each of them. Among them, semiconductor silicon crystals are the main substrate material. The general-purpose size of the substrate is 155 mm square and about 0.3 mm thick, and this general-purpose size silicon crystal substrate is treated to enable high-efficiency solar power generation, and electrodes for extracting the generated power are attached. The product is called a "cell", and the product in which a large number of these cells are arranged in a plane is called a "module". This module is installed according to the usage environment and used as a solar power generation device.

To reduce the power generation cost of solar cells, we will improve the performance of substrates made of semiconductor silicon crystals, which are the main components of cells, and develop new manufacturing methods that can reduce the manufacturing costs of substrate materials from the current level. is important.

By the way, as a structure of a solar cell that is said to be able to achieve highly efficient power generation as a solar cell, an N-type silicon single crystal plate to which phosphorus is added is sandwiched between amorphous silicon layers from both sides to generate usable sunlight. HIT (Heterojunction) with expanded wavelength range
There is a method called withIntrinsic Thin-layer) type.

It is said that the highest efficiency can be achieved by the back contact type combined method that adopts this method called HIT type, collects all the electrodes that take out the generated electricity on the back side, and eliminates the electrodes from the front side. In the N-type silicon single crystal substrate used here, phosphorus must be added homogeneously in the optimum composition.

There are two methods for manufacturing silicon crystal substrates for general-purpose solar cells at present. The first method is a one-way solidification method in which the raw material is melted in a large quartz crucible and solidified from the bottom to the top, and the obtained large crystal mass is cut into a general-purpose size to manufacture a crystal substrate. How to do it.

However, the crystal mass produced by this method is a P-type polycrystal to which boron is added, and in principle, this one-way solidification method produces an N-type single crystal substrate necessary for the highly efficient solar cell described above. Can't be done.

The second method is to melt the raw material in a quartz pot, immerse the seed single crystal in the obtained melt, and pull it upward while thickening it. This is a method of manufacturing a general-purpose size single crystal substrate by cutting a round bar-shaped single crystal.

There are two major issues with this pulling method. The first issue is that the manufacturing unit price becomes high.
The manufacturing cost of the single crystal rod obtained by the pulling method increases as the diameter of the single crystal rod increases. A single crystal rod having a diameter of about 250 mm is required to obtain a general-purpose size substrate, but in order to reduce the manufacturing cost, a single crystal rod having a diameter of about 200 mm is used to manufacture a general-purpose size substrate. Therefore, the shape is such that the four corners of the square are missing, and the efficiency is naturally lower than that of an accurate square product.

The second problem of the pulling method is that the concentration of phosphorus added to make it N-type cannot be homogenized. The phosphorus concentration in the melt melted by adding phosphorus to the raw material silicon is uniform, but the phosphorus concentration in the portion initially solidified as a single crystal is lower than the phosphorus concentration in the melt. This phenomenon is called a "distribution phenomenon", and the ratio of the phosphorus concentration in the melt to the phosphorus concentration in the solidified product is called the "partition coefficient".

In the case of silicon, the partition coefficient of phosphorus is about 0.35, so the phosphorus concentration in the initially solidified portion is thin and the difference remains in the melt. Therefore, as the solidification progresses, the phosphorus concentration in the melt increases, and the phosphorus concentration in the solidified product also increases according to the partition coefficient. Therefore, the optimum composition portion is limited to a part of the obtained single crystal.

Moreover, when about half of the raw material melted in the crucible is solidified at first, the concentration of phosphorus becomes too high and it cannot be used for solar cells. Therefore, the production work of the single crystal is stopped, the atmosphere in the production furnace is maintained in the inert gas atmosphere, the product is taken out while maintaining the raw material melt temperature, and the residual raw material melt is replenished with new granular raw materials. The production method of returning to the original raw material melt composition and restarting the production of the second single crystal is adopted.

In this manufacturing method, the quartz crucible that holds the raw material melt is consumed, so the number of times of repeated use is 2 times, or even if a specially prepared high quality quartz crucible is used, it is limited to 3 times at most. be.

The most problematic thing about this manufacturing method is that the concentration of phosphorus in the product cannot be made uniform. High efficiency can be achieved by manufacturing cells for solar cells using only the optimum composition, but the price of the optimum composition is high because the yield is low, which directly leads to an increase in power generation cost.

Therefore, if cost reduction is attempted by using a product having a phosphorus concentration too low or a phosphorus concentration too high than that of the optimum composition, the power generation efficiency of the module will naturally deteriorate.
In addition to the above, the development of methods for reducing the manufacturing cost of silicon single crystal substrates for solar cells has been vigorously carried out. Rather than cutting a large crystal block to produce a thin plate single crystal, it is possible to reduce cutting loss and production cost by producing a thin plate single crystal having a predetermined thickness from the beginning and cutting it to a predetermined size. Of course, the possibility is high.

There are three types of methods for producing silicon thin plate crystals that have been reported so far.
The first method is to insert a jig called a die (DIE) in which a slit is provided in the raw material melt melted in the rutsubo, and to make the raw material melt that comes out from the slit of the die (DIE) to the upper part by surface tension. , A method for producing a thin plate-shaped single crystal by immersing and solidifying the thin plate-shaped seed single crystal and pulling it upward, which is called an EFG (Edge defined Film-fed Growth) method.

This manufacturing method has been energetically developed mainly in the United States, but has not yet been put into practical use for manufacturing silicon substrates for solar cells. The reasons for this include the fact that it is not possible to find a jig material that can withstand long-term use in a stable manner, that it is difficult to control the temperature when solidifying the raw material melt, and that it is difficult to increase the size. ing.

The second method is a method named ESR (Edge Stabilized Ribbon) method, in which a string is used instead of the above-mentioned die (DIE). In this ESR method, the string is first dipped in the surface of the raw material melt and attached laterally, and when it is lifted slightly upward, the raw material melt that is lifted along with the string by surface tension solidifies to form thin plate crystals.

When the strings are connected to both sides of the string and pulled upward together, the solidified thin plate-like crystals are also pulled upward while growing together. However, in this method, the portion that is first lifted and solidified by the string is "polycrystal", and the thin plate that grows with it is also "polycrystal" and does not become "single crystal".

The third method is the method named Dendritic web (dendritic cloth) method method. Dendrites (dendritic crystals) have the property of preferentially growing in the directional direction with high thermal conductivity when the growth rate reaches a certain rate. This method is a method for producing thin plate-like crystals by utilizing the properties of this dendrite (dendritic crystal).

This method is a method that does not use a jig or a string like the EFG method and the ESR method, and it is said that a single crystal can be grown if the growth is optimally controlled. However, in reality, a single crystal cannot be produced unless the first dendrite (dendritic crystal) is made into a single crystal.Therefore, there is no example of continuous growth of a large and long thin plate-like single crystal by this method. It has not reached industrial production.

On the other hand, as described above, all of the methods for producing thin plate-like crystals reported so far are methods for producing crystals by holding a silicon melt in a quartz crucible. When the raw material silicon is melted in a quartz crucible as in these manufacturing methods, silicon monoxide (SiO) is generated by the reaction between the silicon melt and quartz as in Equation 1.

Silicon monoxide (SiO) produced by the reaction is mixed as a solid solution in the silicon crystal which is a product, and becomes a major factor of performance deterioration as a single crystal. Therefore, in order to produce a high-quality single crystal, a production method that does not require the use of a quartz crucible is desirable.

Currently, as a method for producing a silicon single crystal without using a rutsubo, a high-frequency floating zone melting method for producing a single crystal by melting and solidifying a raw material rod using high-frequency induction heating has been put into practical use (for example, Patent Documents). 1). By this high frequency floating zone melting method, a high-purity single crystal containing no silicon monoxide (SiO) in the product can be obtained.

However, the raw material rods that can be used in the high frequency floating zone melting method are specially prepared and highly precise products, and such raw material rods are expensive, the supply amount is limited, and low cost is expected. Not suitable for use. Furthermore, it is extremely difficult to produce a thin plate-shaped single crystal by this high-frequency floating zone melting method, and there is no report that it was produced.

As another method for producing a high-purity single crystal without using a crucible, a method using infrared rays is known. As a method for producing a single crystal using infrared rays, an infrared floating zone melting method is known in which a raw material powder is processed into a rod shape, which is locally heated to melt and solidify to produce a single crystal rod. ..

In this infrared floating zone melting method, the melt formed by heating with infrared rays is held on the raw material rod by the surface tension of the melt itself, and the raw material is continuously melted and solidified.
In this infrared floating zone melting method, a method of irradiating infrared rays from a horizontal direction has been conventionally adopted. However, in principle, a single crystal having a large diameter cannot be produced by this horizontal irradiation method.

Therefore, a top melting method has been developed that enables the production of single crystals with a large diameter by irradiating the upper surface of a single crystal with a large diameter placed at the bottom with infrared rays to melt it and dropping the raw material melt that melted the raw material onto it. Was done. By this top melting method, the diameter of the single crystal that can be produced is not limited in principle, and the range of application is dramatically expanded.

On the other hand, as the current industrial single crystal materials, in addition to the above-mentioned materials for solar cells, ferroelectric materials such as lithium niobate and lithium tantalate, and phosphor materials such as lutetium silicate and gadolinium silicate are used. Many oxide materials such as yttrium aluminum garnet and gadolinium gallium garnet, which are laser materials, are used.

These oxide materials are used for manufacturing various devices by producing a round bar-shaped single crystal by a pulling method and cutting it into a thin plate-shaped single crystal having a thickness of about 0.3 mm. However, in the pulling method, contamination of the crucible material into the product is unavoidable, and in principle, the concentration of the useful additive in the product cannot be homogenized due to the above-mentioned distribution phenomenon. This causes inconvenience in manufacturing high quality devices.

Therefore, it is far better to manufacture and use a thin plate-shaped single crystal with an optimum composition and a predetermined thickness from the beginning than to manufacture a round bar-shaped single crystal and then cut it into a thin plate-shaped single crystal for use. High-performance products can be manufactured at low cost.

Japanese Patent No. 5279727

However, the results of research and development in the thin plate single crystal manufacturing method so far are not sufficient, and there are only a few examples of manufacturing thin plate single crystals and using them for industrial purposes, such as sapphire single crystal plates and gallium oxide by the EFG method. The production of single crystal plates is known.

The present invention has been made in view of such circumstances, and a thin plate-shaped single crystal having an optimum composition and a homogeneous additive concentration and a thickness of about several hundred μm can be continuously produced at low cost. It is an object of the present invention to provide a thin plate-shaped single crystal manufacturing apparatus and a thin plate-shaped single crystal manufacturing method capable of manufacturing with high accuracy.

The present invention has been invented in order to solve the above-mentioned problems in the prior art.
The thin plate-shaped single crystal manufacturing apparatus of the present invention
An infrared irradiation means for irradiating the upper side surface of a raw material mass for producing a thin plate-shaped single crystal (hereinafter, also referred to as a raw material mass) with infrared rays to melt the surface of the upper side surface.
An elevating means for immersing the lower side surface of the thin plate-shaped seed single crystal in the melt obtained by melting by the infrared irradiation means and obtaining the surface of the upper side surface, and pulling the thin plate-shaped seed single crystal upward from the soaked state. When,
Equipped with
The lower side surface of the thin plate-shaped seed single crystal was immersed in the melt obtained on the surface of the upper side surface of the raw material mass for producing the thin plate-shaped single crystal by the infrared irradiation means. The growth of the single crystal is started from the lower side surface of the thin plate-shaped seed single crystal, and further, the thin plate-shaped seed single crystal is pulled upward via the elevating means, so that the thin plate-shaped single crystal is continuously produced. It is characterized by being done.

With such a configuration, there are few members constituting the apparatus, the additive concentration is uniform with the optimum composition, and a thin plate-shaped single crystal having a thickness of about several hundred μm can be continuously high at low cost. Can be manufactured with precision. Furthermore, a thin plate-like single crystal having a homogeneous composition of a so-called mismatched melting substance such as a decomposition-melting substance or a solid solution substance can be produced with high accuracy.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The infrared ray emitted from the infrared irradiation means is a laser beam.
In this way, the laser beam can accurately heat a predetermined range of the raw material mass, so that the melt does not spill from the upper side surface of the raw material mass, and the melt (melt pool) is surely collected. Can continue to form.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The shape of the irradiation area of the laser beam is a hollow square shape elongated in the horizontal direction.
The peripheral region excluding the central portion of the upper side surface of the raw material mass for producing a thin plate-shaped single crystal is characterized by irradiating a laser beam so as to form the hollow square-shaped irradiation region.

By irradiating the laser beam so as to form the hollow square-shaped irradiation area so as to match the peripheral region excluding the central portion of the upper side surface of the raw material mass, the central portion of the upper side surface of the raw material mass can be irradiated. The peripheral region to be removed is melted first, and the central portion not exposed to the laser beam is melted by heat conduction from the melt in the peripheral region previously melted.

Therefore, the temperature of the central portion can be controlled to be lower than the temperature of the peripheral region. As a method of forming a hollow rectangular irradiation area of the laser beam, for example, a linear laser beam may be irradiated from all sides.

Further, the laser beam may be applied to the upper side surface of the raw material mass from an obliquely upper direction or from directly above to a vertical direction, but the heat conduction characteristics of the single crystal material and the thin plate-like single to be produced are used. It is preferable that the irradiation angle can be adjusted to the optimum angle according to the thickness of the crystal.
By the way, in order to continuously produce a thin plate-shaped single crystal by melting the raw material mass, it is necessary to continuously melt the raw material mass and solidify it as a thin plate-shaped single crystal at the same time. However, heating is required to melt the raw material mass, and cooling of the melt is required to solidify the thin plate-shaped single crystal.

Therefore, in order to enable stable production of thin plate-shaped single crystals, it is essential to continue the contradictory actions of "heating" and "cooling" in a stable manner with good controllability. This can be realized by irradiating the raw material block with the above-mentioned hollow square laser beam.
That is, by having such a temperature distribution in the melt pool on the upper side surface of the raw material mass, the thin plate-shaped single crystal can be stably and continuously grown from the central portion.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The elevating means
It is a winding means for continuously winding the manufactured thin plate-shaped single crystal into a roll shape.
The winding means
A winding shaft that continuously winds the thin plate-shaped single crystal, and
A rotating means for rotating the winding shaft and
Equipped with
It is characterized in that the thin plate-shaped seed single crystal is suspended from the winding shaft.

If the winding means is configured in this way, the continuously produced thin plate-shaped single crystal can be reliably wound around the winding shaft, and the apparatus will not be unnecessarily large. Further, since the produced thin plate-shaped single crystal is in the form of a roll, it can be easily transported at the time of shipment, and the handleability can be improved.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The thin plate-shaped seed single crystal
It is characterized in that it is suspended from the winding shaft via a plurality of thin wires.
By suspending the thin plate-shaped single crystal in this way with a thin wire that is resistant to heat and has high strength, the continuously produced thin plate-shaped single crystal can be reliably wound around the winding shaft.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
In the thin plate-shaped seed single crystal,
The thickness of the part where the thin wire is attached is
The size is preferably equal to or less than the thickness of the thin plate-shaped single crystal to be produced.

As described above, in the thin plate-shaped seed single crystal, if the thickness of the portion to which the thin wire is attached is set to a size equal to or less than the thickness of the manufactured thin plate-shaped single crystal, the thin plate-shaped single crystal is formed on the winding shaft. It is possible to surely prevent the surface of the thin plate-shaped single crystal from coming into contact with the fine wire and causing damage when the thin plate-shaped single crystal is wound.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
On the upper side surface of the raw material mass for producing a thin plate-shaped single crystal,
It is characterized in that a required amount of a liquid phase composition that coexists in equilibrium with the composition of the thin plate-shaped single crystal to be produced is first arranged.

In this way, if the required amount of the liquid phase composition that coexists in equilibrium with the composition of the produced thin plate-shaped single crystal is placed on the upper side surface of the raw material mass from the beginning, the thin plate-shaped single crystal having a homogeneous and optimum composition can be continuously produced. Can be manufactured to.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
Between the elevating means and the raw material mass for producing a thin plate-shaped single crystal,
It is characterized in that an anti-sway member for preventing the continuously manufactured thin plate-shaped single crystal from shaking is provided.

If the anti-sway member is arranged in this way, it is possible to prevent the manufactured thin plate-shaped single crystal from swinging too much from side to side. Therefore, the growth position can be kept within a predetermined range without causing deviation, and a high-quality thin plate-shaped single crystal can be continuously and stably produced.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
Between the elevating means and the raw material mass for producing a thin plate-shaped single crystal,
It is preferable that a shielding member is provided so as to prevent the radiant heat generated from the melt from reaching the continuously produced thin plate-shaped single crystal.

The thin plate-shaped single crystal solidifies while being pulled up from the melt, but when the radiant heat emitted from the melt reaches the manufactured thin plate-shaped single crystal, the production speed of the thin plate-shaped single crystal can be accelerated. It will be difficult. Therefore, by providing the shielding member, it becomes difficult for the radiant heat of the melt to reach the produced thin plate-shaped single crystal, and the production efficiency of the thin plate-shaped single crystal can be improved.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The raw material mass for producing a thin plate-shaped single crystal is characterized in that it is a substantially rectangular parallelepiped.
With such a shape, a melt (melt pool) can be continuously provided on the surface of the upper side surface of the raw material mass by irradiation with infrared rays.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The size of the upper side surface of the raw material mass for producing the thin plate-shaped single crystal shall be set to be several mm or more larger in both the thickness direction and the lateral direction than the size of the lower side surface of the thin plate-shaped seed single crystal. It is characterized by.

If the size of the raw material mass and the thin plate-shaped seed single crystal is set in this way, the lower side surface of the thin plate-shaped seed single crystal can be completely immersed in the melt, and the thin plate-shaped single crystal of a desired size can be continuously arranged. Can be manufactured as a target.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
A mounting table on which the raw material mass for producing a thin plate-shaped single crystal is placed, and
A position control means for controlling the position of the pedestal described above so as to be a predetermined position,
It is characterized by having.

If the position of the mounting table (especially the position in the vertical direction) can be controlled in this way, the initial position is maintained even if the liquid level position of the melt of the raw material mass is lowered due to the pulling up of the thin plate-shaped single crystal. The position of the raw material mass can be raised as described above, and the liquid level position can always be controlled to the same position. Therefore, it suffices to always fix the infrared irradiation position at the same position, and a thin plate-shaped single crystal can be continuously produced stably and with good yield.
When irradiating the laser beam traveling in parallel from the direction perpendicular to the upper side surface of the raw material mass, the irradiation intensity of the laser beam does not change even if the liquid level position of the melt of the raw material mass is lowered. It is not necessary to control the position to keep the liquid level position of the mass melt constant.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The elevating means
It is characterized in that the lower side surface of the thin plate-shaped seed single crystal is immersed in the center of the melt on the upper side surface of the raw material mass for producing a thin plate-shaped single crystal melted by the infrared irradiation means.

The central part of the melt is a part where the melt is continuously accumulated, and if the lower side surface of the thin plate-shaped seed single crystal is immersed in this center, the thin plate-shaped seed single crystal is continuously pulled upward by an elevating means. It is possible to produce a thin plate-shaped single crystal.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
Around the raw material mass for producing a thin plate-shaped single crystal,
It is characterized in that a preheating means for preheating the raw material mass for producing a thin plate-shaped single crystal is provided.

By heating the raw material mass to near the melting point in advance in this way, it is possible to reduce the amount of infrared irradiation by the infrared irradiation means, and at the same time, by improving the adjustment accuracy, the range of the melt pool can be finely adjusted. .. Therefore, thin plate-shaped single crystals can be continuously produced stably and with high accuracy.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
At least the raw material mass for producing a thin plate-shaped single crystal is arranged in the chamber.
It is preferable that the elevating means is arranged on the upper part of the chamber.
If the raw material mass is arranged in the chamber in this way, a thin plate-shaped single crystal can be produced in an atmosphere that matches the single crystal material.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The chamber is provided with a gas introduction device that fills the inside of the chamber with an atmospheric gas containing an additive.

If the gas introduction device is provided in this way, the inside of the chamber can be made to have an atmosphere that matches the characteristics of the material of the thin plate-shaped single crystal to be manufactured, whereby the additive concentration is the optimum composition and the uniform high quality. A thin plate-shaped single crystal can be produced.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The elevating means
It is characterized in that a plurality of them are provided on the upper part of the raw material block for producing a thin plate-shaped single crystal.

If it is configured in this way, for example, by immersing a plurality of thin plate-shaped seed single crystals side by side in one melt pool and pulling them up by an elevating means, the thin plate-shaped single crystals are compared with the case where one elevating means is used. The manufacturing efficiency of the product can be significantly improved.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The thickness of the thin plate-shaped seed single crystal is preferably in the range of 300 μm to 500 μm.
With such a thickness, it is possible to continuously produce a high-purity thin plate-shaped single crystal and wind it up to achieve a longer length.

Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention is used.
The thickness of the thin plate-shaped single crystal is preferably in the range of 100 μm to 3000 μm.
The thickness of the thin plate-shaped single crystal to be produced can be produced in the range of 100 μm to 3000 μm, but it is preferably in the range of 100 μm to 500 μm when it is assumed that the single crystal is wound by a winding means. .. However, it can be adjusted to be thinner than 100 μm or thicker than 500 μm by adjusting the melt temperature and the pulling speed.

However, in the case of a thin plate-shaped single crystal thicker than 500 μm, the diameter when the thin plate-shaped single crystal is wound on the winding shaft of the winding means becomes large. In this case, it is also possible to pull it upward and commercialize it without winding it up. In particular, when a silicon thin plate-shaped single crystal for a solar cell is produced, the thickness of the thin plate-shaped single crystal is preferably in the range of 200 μm to 400 μm.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
A melting step of irradiating the upper side surface of the raw material mass for producing a thin plate-shaped single crystal with infrared rays via an infrared irradiation means to melt the surface of the upper side surface of the raw material mass for producing a thin plate-shaped single crystal.
In the melting step, the lower side surface of the thin plate-shaped single crystal is dipped in the melt obtained on the surface of the upper side surface of the raw material mass for producing the thin plate-shaped single crystal via an elevating means, and the thin plate-shaped single crystal is used. A growing step of starting the growing of a single crystal from the lower side surface of the crystal, and
In the growing step, the thin plate-shaped seed single crystal from which the growth of the single crystal was started is pulled upward to continuously produce the thin plate-shaped single crystal, and the continuous manufacturing step.
It is characterized by having at least.
With such a production method, a thin plate-like single crystal having an optimum composition and a uniform additive concentration and a thickness of about several hundred μm can be continuously produced with high accuracy at low cost.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
In the melting step,
The infrared ray emitted from the infrared irradiation means is a laser beam.

In this way, with laser light, a predetermined range of the raw material mass can be accurately heated in a required shape, so that the melt does not spill from the upper side surface of the raw material mass, and the melt pool is ensured. Can continue to form.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
In the melting step,
The shape of the irradiation area of the laser beam is a hollow square shape elongated in the horizontal direction.
The peripheral region excluding the central portion of the upper side surface of the raw material mass for producing a thin plate-shaped single crystal is characterized by irradiating a laser beam so as to form the hollow square-shaped irradiation region.

By irradiating the laser beam so as to match the peripheral region excluding the central portion of the upper side surface of the raw material mass so as to form the hollow square-shaped irradiation area in this way, the central portion of the upper side surface of the raw material mass is irradiated. The peripheral region to be removed is melted first, and the central portion not exposed to the laser beam is melted by heat conduction from the melt in the peripheral region previously melted.

Therefore, the temperature of the central portion can be controlled to be lower than the temperature of the peripheral region. As a result, the contradictory actions of melting the raw material mass and solidifying from the melt can be continued stably and with good controllability.
That is, by having such a temperature distribution in the melt pool on the upper side surface of the raw material mass, the thin plate-shaped single crystal can be stably and continuously grown from the central portion.

Further, the laser beam may be applied to the upper side surface of the raw material mass from an obliquely upper direction or from directly above to a vertical direction, but it depends on the thermal conductivity and thickness of the thin plate-shaped single crystal material. Therefore, it is preferable to adjust the irradiation angle to the optimum angle. For materials with high thermal conductivity, the irradiation angle of the laser beam should be controlled to a large horizontal angle, and for materials with low thermal conductivity, the irradiation angle of the laser beam should be controlled to be small. Is preferable.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
After the continuous manufacturing process
A winding process in which the continuously manufactured thin plate-shaped single crystal is wound into a roll,
It is characterized by further having.
If the winding step is provided in this way, the continuously produced thin plate-shaped single crystal can be reliably wound into a roll shape, and the thin plate-shaped single crystal can be efficiently produced.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
In the melting step,
When the thin plate-shaped single crystal to be produced is a decomposition-melting substance, the composition of the liquid phase (this is called a solvent phase) that coexists in equilibrium with the composition is first prepared in a required amount to produce the thin plate-like single crystal. It is characterized in that it is placed on the upper side surface of the raw material mass.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
In the melting step,
When the thin plate-shaped single crystal to be produced is a solid solution substance containing an additive, a composition of a liquid phase (this is called a solvent phase) that coexists in equilibrium with the composition is first provided in a required amount in the thin plate-like shape. It is characterized in that it is arranged on the upper side surface of a raw material mass for single crystal production.

As a result, when the thin plate-shaped single crystal is first solidified from the solvent phase formed on the upper side surface of the raw material mass, the amount of the solvent phase is reduced and the composition is reduced in the number of crystal components. Therefore, below the solvent phase, the ultimate intensity of the laser beam increases and the temperature rises, so that the raw material mass melts.

As a result, crystallization and melting of the raw material mass proceed at the same time, so that the additive concentration in the obtained product (thin plate-shaped single crystal) becomes the same as the additive concentration in the raw material mass and becomes homogeneous. This scheme is called the "solvent transfer method" and is the only means by which a homogeneous composition single crystal product can be produced by the melt method.

In this way, by first arranging the required amount of the liquid phase composition that coexists in equilibrium with the composition of the produced thin plate-shaped single crystal on the upper side surface of the raw material mass, the thin plate-shaped single crystal having a homogeneous and optimum composition is placed first. Can be manufactured continuously.

Further, the method for producing a thin plate-shaped single crystal of the present invention is:
In the growing process,
It is characterized in that the lower side surface of the thin plate-shaped seed single crystal is immersed in the center of the melt on the surface of the upper side surface of the raw material mass for producing the melted thin plate-shaped single crystal.

The central part of the melt is a part where the melt is continuously accumulated, and if the lower side surface of the thin plate-shaped seed single crystal is immersed in this center, the thin plate-shaped seed single crystal is continuously pulled upward by an elevating means. It is possible to produce a thin plate-shaped single crystal.

According to the thin plate-shaped single crystal manufacturing apparatus and the thin plate-shaped single crystal manufacturing method of the present invention, the surface of the upper side surface of the raw material mass for thin plate-shaped single crystal manufacturing is melted with infrared rays to form a melt, and the melt is formed in the melt. By immersing a thin plate-shaped single crystal and pulling it upward, a thin plate-shaped single crystal with an optimum composition and homogeneity and a thickness of about several hundred μm can be produced at low cost and continuously with high accuracy. Can be manufactured.

FIG. 1 is a schematic view of a thin plate-shaped single crystal manufacturing apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram showing the shape of the irradiation area of the laser beam emitted from the infrared irradiation means. FIG. 3 is a conceptual diagram of a state in which a raw material mass for manufacturing a thin plate-shaped single crystal is viewed from the upper side surface side in the thin plate-shaped single crystal manufacturing apparatus of the present invention. FIG. 4 is another schematic view of the thin plate-shaped single crystal manufacturing apparatus according to the first embodiment of the present invention. FIG. 5 is a diagram for explaining a state of a melt (melt pool) formed on the upper side surface of a raw material mass for manufacturing a thin plate-shaped single crystal in the thin plate-shaped single crystal manufacturing apparatus shown in FIG. FIG. 6 is a diagram for explaining a state of a melt (melt pool) formed on the upper side surface of a raw material mass for manufacturing a thin plate-shaped single crystal in the thin plate-shaped single crystal manufacturing apparatus shown in FIG. FIG. 7 is a schematic perspective view for explaining the states of the raw material mass for producing a thin plate-shaped single crystal, the thin plate-shaped seed single crystal, and the thin plate-shaped single crystal. FIG. 8 is a schematic view of the thin plate-shaped single crystal manufacturing apparatus according to the second embodiment of the present invention. FIG. 9 is a schematic view of another thin plate-shaped single crystal manufacturing apparatus according to the second embodiment of the present invention. FIG. 10 is a schematic view of a thin plate-shaped single crystal manufacturing apparatus according to a third embodiment of the present invention. FIG. 11 is an enlarged view of a main part of the thin plate-shaped single crystal manufacturing apparatus shown in FIG. FIG. 12 is a schematic view showing each step of the thin plate-shaped single crystal manufacturing method of the present invention. FIG. 13 is a schematic view showing each step of the thin plate-shaped single crystal manufacturing method of the present invention.

Hereinafter, the thin plate-shaped single crystal manufacturing apparatus and the thin plate-shaped single crystal manufacturing method of the present invention will be described in more detail with reference to the drawings.
In the thin plate-shaped single crystal manufacturing apparatus and the thin plate-shaped single crystal manufacturing method of the present invention, thin plate-shaped single crystals having an optimum composition and a uniform thickness and a thickness of about several hundred μm can be continuously produced at low cost. It is for manufacturing with high precision.

<Thin plate-shaped single crystal manufacturing apparatus 10>
[First Embodiment]
As shown in FIG. 1, the thin plate-shaped single crystal manufacturing apparatus 10 according to the first embodiment of the present invention first has a raw material mass for manufacturing a thin plate-shaped single crystal on a mounting table 82 arranged below in the chamber 80. (Hereinafter, also referred to as a raw material mass) 12 is provided. The raw material mass 12 has a substantially rectangular parallelepiped shape, and is, for example, a plate-like body such as a book.

Further, an infrared irradiation means 20 for irradiating the upper side surface 14 of the raw material mass 12 of the substantially rectangular parallelepiped with infrared rays 16 to melt the surface of the upper side surface 14 is provided on the upper side of the chamber 80.
The infrared ray 16 emitted from the infrared irradiation means 20 is preferably laser light 16a.

That is, as shown in FIG. 2, the shape of the irradiation area of the laser beam 16a is a hollow square shape elongated in the horizontal direction (vertical direction in FIG. 2), and as shown in FIG. 3, the upper side surface 14 of the raw material mass 12 It is preferable to irradiate the peripheral region excluding the central portion of the above with the laser beam 16a aligned so as to form the horizontally elongated hollow square irradiation region.

Here, the laser light 16a emitted from the infrared irradiation means 20 is incident into the chamber 80 from the window 22 provided on the side of the chamber 80, and is on the raw material mass 12 via the reflector 24 in the chamber 80. It is preferable to irradiate the peripheral region excluding the central portion of the side surface 14. At this time, even if the laser beam 16a irradiates the upper side surface 14 of the raw material mass 12 from an obliquely upward direction as shown in FIG. 1, the upper side surface 14 of the raw material mass 12 is as shown in FIG. On the other hand, the irradiation may be performed in the vertical direction from directly above, but the irradiation angle is controlled to the optimum angle by matching the thermal conductivity of the single crystal material and the thickness of the thin plate-shaped single crystal 40 to be manufactured.

As a result, the peripheral region excluding the central portion of the upper side surface 14 of the raw material mass 12 is melted before the central portion, and the central portion not exposed to the laser beam 16a is the melt 18 in the peripheral region previously melted. It will be melted by heat conduction from.

Therefore, the temperature of the central portion can be controlled to be lower than the temperature of the peripheral region, and by having such a temperature distribution in the melt 18 (melt pool) on the upper side surface 14 of the raw material mass 12, this center The thin plate-shaped single crystal 40 can be stably and continuously grown from the portion.

That is, as shown in FIGS. 5 and 6, by irradiating the peripheral region excluding the central portion of the upper side surface 14 of the raw material mass 12 with the laser beam 16a, the melt 18 is formed deeper in the peripheral region. Therefore, a melt 18 having a temperature shallower and lower than that of the peripheral region is formed in the central portion.

As shown in FIGS. 1, 3, and 4, a preheating means 70 for preheating the raw material mass 12 is provided around the raw material mass 12, and the infrared irradiation means 20 provides an upper side surface of the raw material mass 12. Before melting the surface of 14, it is preferable to heat the raw material mass 12 to near the melting point in advance. If it is heated in advance in this way, the irradiation amount of the infrared ray 16 by the infrared irradiation means 20 can be significantly reduced, and by finely adjusting the position and the irradiation amount, the melt 18 (melt pool) can be used. The range of can be fine-tuned.

On the other hand, above the chamber 80, the lower side surface 34 of the thin plate-shaped seed single crystal 32 is immersed in the melt 18 obtained by being melted by the infrared irradiation means 20 and obtained on the surface of the upper side surface 14 of the raw material mass 12. The elevating means 30 for pulling up the thin plate-shaped seed single crystal 32 from the soaked state is provided.

The elevating means 30 is not particularly limited, but for example, the winding means 50 for continuously winding the manufactured thin plate-shaped single crystal 40 into a roll shape is preferable. As a specific configuration, it has a winding shaft 36 for continuously winding the manufactured thin plate-shaped single crystal 40, and a rotating means 38 for rotating the winding shaft 36.

Here, the size of the lower side surface 34 of the thin plate-shaped seed single crystal 32 is set to be one size smaller than the upper side surface 14 of the raw material mass 12. For example, as a specific relationship between the two sizes, the size of the upper side surface 14 of the raw material mass 12 is several mm in both the thickness direction and the lateral direction than the size of the lower side surface 34 of the thin plate-shaped seed single crystal 32. As mentioned above, it is set large. That is, the size is set so that the lower side surface 34 of the thin plate-shaped seed single crystal 32 can be completely immersed in the melt 18.

Then, as shown in FIG. 7, at the center of the melt 18 obtained on the surface of the upper side surface 14 of the raw material mass 12 by the infrared irradiation means 20, under the thin plate-shaped seed single crystal 32 via the elevating means 30. By immersing the side surface 34, the growth of the single crystal is started from the lower side surface 34 of the soaked thin plate-shaped seed single crystal 32, and further, the thin plate-shaped seed single crystal 32 is continuously pulled upward via the elevating means 30. The thin plate-shaped single crystal 40 will be produced.

The thickness of the thin plate-shaped single crystal 40 to be produced can be adjusted by the melt temperature, the pulling speed of the thin plate-shaped seed single crystal 32, etc. in a steady state, and should be, for example, a thickness of about 100 μm to over 3000 μm. Can be done. However, if the thickness of the thin plate-shaped single crystal 40 exceeds 500 μm, the winding means 50 becomes large. Therefore, if the thickness exceeds 500 μm, the thin plate-shaped single crystal 40 can be pulled upward without being wound into a product. In particular, in the case of producing a silicon thin plate-shaped single crystal for a solar cell, the thickness of the thin plate-shaped single crystal 40 is preferably in the range of 200 μm to 400 μm.

There is a correlation between the melt temperature and the pulling speed. That is, when the melt temperature is high, the amount of cooling required for the growth of the thin plate-shaped single crystal 40 increases, so that the pulling speed is slowed down, and when the melt temperature is low, the pulling speed of the thin plate-shaped single crystal 40 is increased. The productivity of the thin plate-shaped single crystal 40 can be increased by accelerating. However, if the pulling speed is too fast, so-called "cell growth" tends to occur and the crystal characteristics of the thin plate-shaped single crystal 40 deteriorate. Therefore, it is preferable to adjust the pulling speed as appropriate.

The thickness of the thin plate-shaped seed single crystal 32 immersed in the melt 18 may be, for example, about 300 μm to 500 μm. With the thin plate-shaped single crystal 32 having such a thickness, the thin plate-shaped single crystal 40 having a desired thickness can be continuously produced by adjusting the melt temperature and the pulling speed, which is preferable.

Further, in FIGS. 1 and 4, the thickness of the thin plate-shaped single crystal 40 and the thickness of the thin plate-shaped seed single crystal 32 are shown differently, which are shown in the figure of the thin plate-shaped single crystal 40 and the thin plate-shaped seed. It is intentionally made so that the single crystal 32 can be distinguished, and does not particularly limit the relationship between the thicknesses of the two.

At this time, it is preferable to suspend the thin plate-shaped seed single crystal 32 on the winding shaft 36 of the winding means 50 via a plurality of heat-resistant and high-strength thin wires 52 (three in FIG. 7). In particular, in the thin plate-shaped seed single crystal 32, if the thickness of the portion to which the thin wire 52 is attached is set to be equal to or less than the thickness of the thin plate-shaped seed single crystal 32, the thin plate-shaped single crystal 40 is wound around the winding shaft 36. It is possible to reliably prevent the surface of the thin plate-shaped single crystal 40 from coming into contact with the fine wire 52 and causing damage.

The method of attaching the thin wire 52 to the thin plate-shaped seed single crystal 32 is not particularly limited, but for example, several through holes for connecting the thin wire 52 are provided at the end of the thin plate-shaped seed single crystal 32, and the through holes are provided. When the thin wire 52 is connected to the thin plate-shaped seed single crystal 32 by providing concave grooves on both sides of the thin plate-shaped seed single crystal 32, the fine wire 52 fits in the concave groove and is formed from the thin plate-shaped seed single crystal 32. It is also good to prevent the thin wire 52 from protruding outward. By doing so, when the thin plate-shaped single crystal 40 is wound up, it is possible to reliably prevent the surface of the thin plate-shaped single crystal 40 from coming into contact with the fine wire 52 and causing damage.

Further, in the thin plate-shaped single crystal manufacturing apparatus 10, the thin plate-shaped single crystal 40 continuously manufactured between the elevating means 30 and the raw material mass 12 is prevented from shaking so that the growth position does not shift. It is possible to provide an anti-sway member 60 that stays within a predetermined range, and a shielding member 62 that shields the radiant heat generated from the melt 18 so that it does not easily reach the continuously manufactured thin plate-shaped single crystal 40. preferable.

By providing the anti-sway member 60, it is possible to prevent the manufactured thin plate-shaped single crystal 40 from swinging excessively to the left and right and causing the growth position to shift, and it is possible to continuously manufacture the high-quality thin plate-shaped single crystal 40. can.

Further, by providing the shielding member 62, the production speed of the thin plate-shaped single crystal 40 can be increased. That is, the method of melting the raw material and solidifying it as a single crystal is called a melt method, and the growth rate of the single crystal in this melt method is the latent heat of crystallization released when the crystal solidifies into the melt. It is accelerated by efficiently exhausting heat by heat conduction in the contacting single crystal.

Therefore, for example, if the shielding member 62 is provided so as not to block the optical path of the infrared ray 16 (laser light 16a), the amount of radiant heat reaching the thin plate-shaped single crystal 40 is reduced, and the temperature of the thin plate-shaped single crystal 40 is not raised. Therefore, the latent heat of crystallization can be efficiently exhausted, and the production efficiency of the thin plate-shaped single crystal 40 can be improved.

As described above, the thin plate-shaped single crystal 40 can be continuously produced by using the thin plate-shaped single crystal manufacturing apparatus 10, but when the thin plate-shaped single crystal 40 is continuously produced, the raw material mass is produced. The amount of melt 18 obtained on the surface of the upper side surface 14 of the 12 is reduced, and the position of the upper side surface 14 is lowered. If this happens, it is necessary to control the infrared irradiation position by the infrared irradiation means 20 so as to be a desired position.

In the present embodiment, instead of controlling the irradiation position of the infrared ray 16, the mounting table 82 on which the raw material mass 12 is placed is provided with a position controlling means 84 for controlling the vertical position of the mounting table 82.

By providing the position control means 84 in this way, even if the position of the melt 18 on the upper side surface 14 of the raw material mass 12 is lowered due to the pulling up of the continuously manufactured thin plate-shaped single crystal 40, the mounting table 82 can be provided. The position of the melt 18 on the upper side surface 14 of the raw material mass 12 can be kept at the same position as the initial position, and the liquid level position of the melt 18 can always be the same position.

Therefore, it suffices to always irradiate the same position with infrared rays 16, and the thin plate-shaped single crystal 40 can be continuously manufactured with a stable yield and good yield. Here, in the case of irradiating the upper side surface 14 of the raw material block 12 with the laser beam 16a vertically from directly above the raw material block 12, as in the thin plate-shaped single crystal manufacturing apparatus 10 shown in FIGS. 4 and 6. Since the temperature of the melt 18 does not change even if the position of the upper side surface 14 of the raw material mass 12 changes, it is not necessary to control the position of the upper side surface 14 of the raw material mass 12.
The raw material mass 12 used in the above-mentioned thin plate-shaped single crystal manufacturing apparatus 10 is a raw material mass 12 having the composition of the material of the thin plate-shaped single crystal 40 to be manufactured. However, when the material of the thin plate-shaped single crystal 40 is a decomposition-melting substance, even if the raw material mass 12 is melted and solidified as it is by the main thin plate-shaped single crystal manufacturing apparatus 10, the target thin plate-shaped single crystal is obtained. You can't get 40.

The composition of the liquid phase that coexists in equilibrium with the composition of the material of the thin plate-shaped single crystal 40 produced there is placed on the upper side surface 14 of the raw material mass 12 by the amount of the liquid phase, and this is first melted. In this way, the dissolved solvent is placed on the upper side surface 14 of the raw material mass 12.

When the thin plate-shaped single crystal 40 is produced in this way, the same amount of the raw material mass 12 solidified as the single crystal is melted, so that the amount and composition of the solvent do not change from the beginning to the end, and apparently the solvent phase. Seems to be moving while melting the raw material mass 12 and precipitating a single crystal.

This scheme is called the "solvent transfer method". When the thin plate-shaped single crystal 40 obtained by the present thin plate-shaped single crystal manufacturing apparatus 10 is a decomposition-melting substance or a solid solution substance containing an additive, the concentration of the additive in the obtained thin plate-shaped single crystal 40 is made uniform. It is important to use this "solvent transfer method".

[Second Embodiment]
Next, a second embodiment of the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention will be described.
8 and 9 are the thin plate-shaped single crystal manufacturing apparatus 10 according to the second embodiment of the present invention.

The thin plate-shaped single crystal manufacturing apparatus 10 shown in FIGS. 8 and 9 basically has the same configuration as the thin plate-shaped single crystal manufacturing apparatus 10 of the first embodiment shown in FIGS. 1 to 7, and thus has the same configuration. The components are designated by the same reference number, detailed description thereof will be omitted, and differences will be described.

As shown in FIGS. 8 and 9, the thin plate-shaped single crystal manufacturing apparatus 10 according to the second embodiment of the present invention is a gas introduction apparatus in which the inside of the chamber 80 is filled with an atmospheric gas containing an additive in the chamber 80. It differs from the thin plate-shaped single crystal manufacturing apparatus 10 in the first embodiment in that 90 is provided.

The gas introduction device 90 is provided on the upper side of the chamber 80, and the atmospheric gas is introduced from the gas introduction device 90 into the chamber 80 via the introduction pipe 92. Further, a discharge pipe 94 is provided on the lower side of the chamber 80 so that the atmospheric gas can be discharged from the discharge pipe 94 to the outside of the chamber 80.

As a result, the inside of the chamber 80 can be maintained in a state of being filled with an atmospheric gas suitable for producing the thin plate-shaped single crystal 40, and the thin plate-shaped single crystal 40 having a uniform additive concentration and high quality can be continuously produced. Can be manufactured.

The atmosphere gas may be prepared according to the characteristics of the material of the thin plate-shaped single crystal 40 to be manufactured. For example, in the case of producing a thin plate-shaped single crystal of N-type silicon, phosphin (PH ₃ ) is used as the atmosphere gas. It is preferable to introduce high-purity argon gas contained in the optimum concentration into the chamber 80.

Further, as shown in FIG. 9, for example, a window 22 for guiding the infrared ray 16 (laser light 16a) emitted from the infrared ray irradiating means 20 into the chamber 80, and an infrared ray 16 guided into the chamber 80. A reflector 24 or the like for guiding (laser light 16a) to the upper side surface 14 of the raw material mass 12 is covered with a cover member 42, and atmospheric gas is positively introduced into the cover member 42 from the gas introduction device 90. It is also good to do so.

If the atmospheric gas is introduced into the cover member 42 in this way, it is possible to prevent the evaporation generated from the melt 18 from adhering to the window 22, the reflector 24, and the like, and the additive concentration is uniform. It is possible to continuously produce a high-quality thin plate-shaped single crystal 40 with a stable yield and good yield.

[Third Embodiment]
Next, a third embodiment of the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention will be described.
10 and 11 are the thin plate-shaped single crystal manufacturing apparatus 10 according to the third embodiment of the present invention.

The thin plate-shaped single crystal manufacturing apparatus 10 shown in FIGS. 10 and 11 basically has the same configuration as the thin plate-shaped single crystal manufacturing apparatus 10 of the first embodiment shown in FIGS. 1 to 7, and thus has the same configuration. The components are designated by the same reference number, detailed description thereof will be omitted, and differences will be described.

As shown in FIGS. 10 and 11, the thin plate-shaped single crystal manufacturing apparatus 10 according to the third embodiment of the present invention is provided with a plurality of elevating means 30 (two in FIG. 10) above the raw material mass 12. In that respect, it is different from the thin plate-shaped single crystal manufacturing apparatus 10 in the first embodiment.

Specifically, two elevating means 30 (winding means 50) are provided side by side on the upper side of the chamber 80, and thin plate-shaped seed single crystals 32, 32 are provided in the melt 18 on the upper side surface 14 of the raw material mass 12. The thin plate-shaped single crystals 40 and 40 can be manufactured, respectively, by immersing the crystals and pulling them upward by the elevating means 30 and 30 (winding means 50 and 50), respectively.
If a plurality of the elevating means 30 are provided on the upper part of the raw material mass 12 in this way, the production efficiency of the thin plate-shaped single crystal 40 can be significantly improved as compared with the case where the elevating means 30 is one.

<Method for manufacturing thin plate-shaped single crystal>
Next, a thin plate-shaped single crystal manufacturing method using the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention will be described.

First, as shown in FIG. 12A, the raw material lump 12 is placed on the mounting table 82 in the chamber 80 to seal the inside of the chamber 80, and the raw material lump 12 is placed on the upper portion of the upper side surface of the raw material lump 12 in the length direction of the raw material lump 12. The thin plate-shaped seed single crystal 32 is arranged so that the extending directions of the thin plate-shaped seed single crystal 32 and the thin plate-shaped seed single crystal 32 coincide with each other. The thin plate-shaped seed single crystal 32 is suspended from the winding shaft 36 of the winding means 50 via a thin wire 52.

In the chamber 80, the atmosphere is evacuated through an exhaust pipe (not shown), and an atmosphere gas matching the characteristics of the material of the thin plate-shaped single crystal 40 to be manufactured is a gas introduction device (not shown). Is introduced into the chamber 80 via.

Next, the temperature of the raw material mass 12 is raised to near the melting point by the preheating means 70. Next, as shown in FIG. 12B, the upper side surface 14 of the raw material mass 12 is irradiated with infrared rays 16 (laser light 16a) via the infrared irradiation means 20, and the surface of the upper side surface 14 is melted.

The shape of the irradiation area of the infrared ray 16 (laser light 16a) is a hollow square shape elongated in the horizontal direction, and the peripheral region excluding the central portion of the upper side surface 14 of the raw material mass 12 is irradiated with the hollow square shape elongated in the horizontal direction. The laser beam 16a is matched and irradiated so as to form a region.

As a result, the peripheral region excluding the central portion of the upper side surface 14 of the raw material mass 12 is melted before the central portion, and the central portion not exposed to the laser beam 16a is the melt 18 in the peripheral region previously melted. It is melted by heat conduction from.

Next, as shown in FIG. 12 (c), the thin plate-shaped seed single crystal 32 was placed at the center of the melt 18 obtained on the upper side surface 14 of the raw material mass 12 via the elevating means 30 (winding means 50). The lower side surface 34 is immersed, and the growth of the single crystal is started from the lower side surface 34 of the thin plate-shaped seed single crystal 32.

Next, as shown in FIG. 13A, the thin plate-shaped seed single crystal 32 is pulled upward via the elevating means 30 (winding means 50) to continuously produce the thin plate-shaped single crystal 40.
Next, as shown in FIG. 13 (b), the position of the mounting table 82 is moved upward via the position control means 84 with the continuous production of the thin plate-shaped single crystal 40. As a result, even if the position of the melt 18 of the raw material mass 12 is lowered due to the pulling up, the position of the raw material mass 12 is controlled so as to maintain the initial position, and the liquid level position of the melt 18 is always set to the same position. do.
Here, in the case of irradiating the upper side surface 14 of the raw material block 12 with the laser beam 16a vertically from directly above the raw material block 12, as in the thin plate-shaped single crystal manufacturing apparatus 10 shown in FIGS. 4 and 6. Since the temperature of the melt 18 does not change even if the position of the upper side surface 14 of the raw material mass 12 changes, it is not necessary to control the position of the upper side surface 14 of the raw material mass 12 to a fixed position.

Finally, as shown in FIG. 13 (c), the irradiation amount of the infrared ray 16 (laser light 16a) by the infrared ray irradiating means 20 is increased to raise the temperature of the melt 18 and the thin plate-shaped single crystal 40 is separated from the melt 18. When the winding of the thin plate-shaped single crystal 40 continuously produced by the elevating means 30 (winding means 50) is completed and the irradiation of the infrared ray 16 (laser light 16a) by the infrared irradiation means 20 is completed, the thin plate-shaped single crystal is completed. The production of 40 is completed.

[Example 1]
Using the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention, a thin plate-shaped single crystal 40 of N-type silicon to which phosphorus was added was manufactured.

As the raw material mass 12, a cubic raw material mass 12 having a width of 400 mm, a thickness of 50 mm, and a height of 500 mm was used.
On the other hand, as the thin plate-shaped seed single crystal 32, a silicon thin plate-shaped seed single crystal 32 having a (111) plane, a width of 350 mm, a thickness of 0.3 mm, and a height of 100 mm was used. Silicon has a property that a flat surface called a facet tends to appear in the (111) plane direction, and this flat surface is used as the plate surface of the thin plate-shaped seed single crystal 32. The thin plate-shaped seed single crystal 32 was previously attached to the winding shaft 36 of the winding means 50 via three thin wires 52.

First, the raw material mass 12 was placed on the mounting table 82 in the chamber 80, and the chamber 80 was closed to create a vacuum state inside.
Next, an atmospheric gas was introduced into the chamber 80. As the atmosphere gas, high-purity argon gas was used, and a gas to which a required amount of phosphine (PH ₃ ) gas was added in order to add phosphorus was used.

The raw material mass 12 is first heated to near the melting point by the preheating means 70, and after confirming the heating, the width 20 mm and the length 396 mm are formed in the peripheral region excluding the central portion and the outermost peripheral portion of the upper side surface 14 of the raw material mass 12. The laser beam is emitted from the left and right at an angle of 60 degrees from the horizontal direction at a distance of 2 mm from the end portion, and at the same time, both ends of the raw material mass 12 in the length direction are on the center line of the raw material mass 12 and have a width of 6 mm at a distance of 2 mm from the end. The laser beam 16a having the shape of the irradiation area perpendicular to the horizontal direction was irradiated at an angle of 60 degrees from the horizontal direction. The shape of the irradiation area is a hollow square shape that is elongated in the horizontal direction as a whole. As a result, the entire area of the upper side surface 14 was melted.

The lower side surface 34 of the above-mentioned silicon thin plate-shaped seed single crystal 32 is immersed in the center of the melt 18 obtained by rotating the winding shaft 36 of the winding means 50 and melting the thin plate-shaped seed single crystal 32. While growing the thin plate-shaped single crystal 40 from the lower side surface 34, this time, the winding shaft 36 is rotated in the opposite direction, the thin plate-shaped seed single crystal 32 is pulled upward, and the thin plate-shaped single crystal is pulled up on the winding shaft 36 at the upper part. 40 was continuously wound into a roll to produce a long thin plate-shaped single crystal 40 having a length of more than 10 m.

The thin plate-shaped seed single crystal 32 is set on the winding shaft 36 of the winding means 50 by a carbon fiber fine wire 52 having a diameter of about 0.05 mm, and the rotating means 38 determines the rotation direction and rotation speed of the winding shaft 36. By controlling, the thin plate-shaped seed single crystal 32 was moved in the vertical direction.

When the thin plate-shaped seed single crystal 32 is immersed in the center of the melt 18, crystallization starts immediately, and the soaked portion of the thin plate-shaped seed single crystal 32 becomes thick, but if left as it is, the thickened portion melts. And confirmed that it became thinner.

In this state, the thin plate-shaped single crystal 32 is pulled upward, the thickness of the manufactured thin plate-shaped single crystal 40 is confirmed with a camera, and the thickness is adjusted to 0 while adjusting the pulling speed and the irradiation intensity of the laser beam 16a. The winding shaft 36 was rotated under a control of 3 mm, and the thin plate-shaped single crystal 40 was continuously wound around the winding shaft 36.

It was confirmed that when the pulling speed of the thin plate-shaped seed single crystal 32 was slowed down, the thickness of the thin plate-shaped single crystal 40 became thicker, and when the pulling speed was increased, the thickness of the thin plate-shaped single crystal 40 became thin. The melt temperature was adjusted so that the thin plate-shaped single crystal 40 having a thickness of 0.3 mm was continuously pulled up at a speed of 30 mm per minute.

Here, as the thin plate-shaped single crystal 40 is pulled up, the liquid level position of the melt 18 of the raw material mass 12 is lowered, so that the position of the mounting table 82 on which the raw material mass 12 is placed is controlled so as to maintain the initial position. It is controlled to a predetermined position via the means 84 so that the liquid level position of the melt 18 of the raw material mass 12 is always the same as the initial position.

A thin plate-shaped single crystal 40 having a length of more than 10 m, a thickness of 0.3 mm, and a width of 383 to 386 mm produced in this manner is subjected to secondary ion mass spectrometry (SIMS) method. As a result, it was confirmed that the concentration of phosphorus as an additive was uniform in the optimum composition and high quality, and the superiority of the thin plate-shaped single crystal manufacturing apparatus 10 and the thin plate-shaped single crystal manufacturing method of the present invention was obtained. It could be confirmed.

Next, a summary of the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention described above and the thin plate-shaped single crystal manufacturing apparatus using the thin plate-shaped single crystal manufacturing apparatus 10 will be described.
The most important factor that enabled the continuous and stable production of the thin plate-shaped single crystal 40 by the thin plate-shaped single crystal manufacturing apparatus 10 and the thin plate-shaped single crystal manufacturing method of the present invention was the melting of the raw material mass 12 and the obtained. The point is that the single crystallization from the melt 18 can be controlled independently of each other.

That is, heating is required to melt the raw material mass 12 to obtain the melt 18, but cooling is required to solidify and crystallize the melt 18, which are contradictory to each other.
Therefore, in the present invention, the portion where crystallization is performed (central portion of the melt 18) is not directly irradiated with the laser beam 16a, and the portion other than the portion where crystallization is performed (the central portion of the melt 18 is excluded). The peripheral region) is irradiated with laser light 16a to melt the upper side surface 14 of the raw material mass 12, and the heat of the melt 18 is conducted to the portion where crystallization is performed (the central portion of the melt 18) to be above. The melt 18 is also formed in the center of the side surface 14.

As a result, the temperature of the portion where crystallization is performed (central portion of the melt 18) is higher than the temperature of the portion melted by being irradiated with the laser beam 16a (peripheral region excluding the central portion of the melt 18). Is also low, facilitating crystallization.

When the thin plate-shaped seed single crystal 32 is immersed in the center of the melt 18, the heat of the melt 18 is transferred to the lower side surface 34 of the soaked thin plate-shaped seed single crystal 32. The temperature drops and crystallization progresses rapidly. If left for a while, the amount of heat that escapes through the thin plate-shaped seed single crystal 32 becomes a steady state, and the part that has solidified rapidly by then gradually melts due to the heat from the surrounding melt 18 and becomes a steady state. ..

When the thin plate-shaped seed single crystal 32 is pulled upward in this state, the thin plate-shaped seed single crystal 32 moves to the low temperature portion, so that crystallization proceeds on the lower side surface 34 in contact with the melt 18.
When the pulling speed of the thin plate-shaped seed single crystal 32 is increased and crystallization cannot catch up, the thickness of the produced thin plate-shaped single crystal 40 becomes thin, and when the pulling speed is slowed down, crystallization proceeds, so that the thin plate-shaped single crystal 40 The thickness of is increased.

Therefore, if the temperature of the melt 18 is controlled to be low, crystallization becomes easy and the thickness of the thin plate-shaped single crystal 40 becomes thick. Therefore, even if the pulling speed is increased, the thin plate-shaped single crystal 40 having a predetermined thickness is continuously formed. Can be manufactured.

If the pulling speed is increased, the production efficiency of the thin plate-shaped single crystal 40 can be increased, but if the pulling speed is too high, the possibility of cell growth increases. When cell growth occurs, the concentration of phosphorus, which is an additive, fluctuates greatly locally, and the characteristics as a single crystal deteriorate. Therefore, it is important to continuously produce the thin plate-shaped single crystal 40 by increasing the pulling speed as much as possible while suppressing the occurrence of cell growth.

Furthermore, according to the present invention, it has become possible for the first time to produce a high-quality thin plate-shaped single crystal 40 having a homogeneous composition for so-called inconsistent melting substances such as decomposition-melting substances and solid solution single crystals. The thin plate-shaped single crystal 40 having a homogeneous composition of such a disagreement-melting substance has been considered impossible to produce by a conventional method.

That is, in order to produce a homogeneous composition single crystal of these inconsistent melting substances by a so-called melt method in which a raw material is melted to form a melt and then solidified to produce a single crystal, a raw material mass having a target composition is produced. In principle, other than applying the so-called solvent transfer method in which 12 is produced and the dissolution of the raw material mass 12 and the precipitation of single crystals from the solvent proceed simultaneously using a solvent having a solvent composition that coexists in equilibrium with the target composition substance. There is no way to do it.

In the present patent, a required amount of the solvent phase component is arranged on the upper side surface 14 of the raw material mass 12 and then irradiated with infrared rays 16 to melt the solvent to form a solvent solution. Then, the solvent transfer method was applied by simultaneously proceeding with the production of the single crystal from the solvent and the dissolution of the raw material mass 12 in the solvent, so that the thin plate-shaped single crystal 40 having a homogeneous composition could be produced.

Although the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention and the thin plate-shaped single crystal manufacturing apparatus 10 using the thin plate-shaped single crystal manufacturing apparatus 10 have been described above, the present invention is not limited to the above embodiment.

For example, in the above-mentioned thin plate-shaped single crystal manufacturing apparatus 10, the first to third embodiments are described separately, but the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention may be obtained by combining them. Is. That is, for example, a thin plate-shaped single crystal manufacturing apparatus 10 in which the first embodiment is combined with the second embodiment and the third embodiment may be used.

Further, in the above-mentioned thin plate-shaped single crystal manufacturing apparatus 10, the case where the infrared irradiation means 20 is provided so as to irradiate each side of the square shape in parallel is taken as an example, but the present invention is not limited to this. Only one infrared irradiation means 20 may be used.

Further, if the laser beam 16a can be irradiated so as to form a horizontally elongated hollow quadrangular irradiation region that matches the peripheral region excluding the central portion of the upper side surface 14 of the raw material mass 12, the elongated hollow quadrangular shape is formed. The irradiation area may be formed by a plurality of laser beams 16a, and the number and the cross-sectional shape of the laser beams 16a irradiated from one infrared irradiation means 20 are not limited.

That is, the upper side surface 14 of the raw material mass 12 is irradiated with the laser beam 16a having a U-shaped cross section from each of the left and right sides, and the two laser beams 16a and 16a having a U-shaped cross section have a hollow rectangular cross-sectional shape elongated in the horizontal direction. An irradiation area may be formed, or a hollow square-shaped irradiation area elongated in the horizontal direction may be formed by four laser beams having a rod-shaped cross section.

Further, although the thickness of the thin plate-shaped single crystal 40 to be manufactured is described as about 100 μm to 3000 μm, it can be manufactured in principle even if the thickness is larger than this, for example, 5000 μm or more. The thickness is not limited to the above range.

Further, the thickness of the thin plate-shaped seed single crystal 32 immersed in the melt 18 is also described as, for example, about 300 μm to 500 μm, but even if the thickness is outside this range, the thin plate is in principle. The state single crystal 40 can be produced, and the thickness is not limited to the above range.

As described above, the thin plate-shaped single crystal manufacturing apparatus 10 and the thin plate-shaped single crystal manufacturing method of the present invention can be variously modified without departing from the object of the present invention.

10 Thin plate-shaped single crystal manufacturing equipment 12 Raw material mass for manufacturing thin plate-shaped single crystal (raw material mass)
14 Upper side surface 16 Infrared 16a Laser light 18 Melt 20 Infrared irradiation means 22 Window 24 Reflector 30 Elevating means 32 Thin plate-shaped seed single crystal 34 Lower side surface 36 Winding shaft 38 Rotating means 40 Thin plate-shaped single crystal 42 Cover member 50 rolls Taking means 52 Fine wire 54 Supply means 56 Supply pipe 60 Anti-sway member 62 Shielding member 70 Preheating means 80 Chamber 82 Mounting table 84 Position control means 90 Gas introduction device 92 Introduction pipe 94 Discharge pipe

Claims (25)

An infrared irradiation means for irradiating the upper side surface of a raw material mass for producing a thin plate-shaped single crystal with infrared rays and melting the surface of the upper side surface.
An elevating means for immersing the lower side surface of the thin plate-shaped seed single crystal in the melt obtained by melting by the infrared irradiation means and obtaining the surface of the upper side surface, and pulling the thin plate-shaped seed single crystal upward from the soaked state. When,
Equipped with
The lower side surface of the thin plate-shaped single crystal was immersed in the melt obtained on the surface of the upper side surface of the raw material mass for producing the thin plate-shaped single crystal by the infrared irradiation means. The growth of the single crystal is started from the lower side surface of the thin plate-shaped seed single crystal, and further, the thin plate-shaped seed single crystal is pulled upward via the elevating means, so that the thin plate-shaped single crystal is continuously produced. A thin plate-shaped single crystal manufacturing apparatus characterized by being made. The thin plate-shaped single crystal manufacturing apparatus according to claim 1, wherein the infrared rays emitted from the infrared irradiation means are laser light. The shape of the irradiation area of the laser beam is a hollow square shape elongated in the horizontal direction.
The second aspect of claim 2, wherein the laser beam is applied so as to form the hollow square-shaped irradiation region on the peripheral region excluding the central portion of the upper side surface of the thin plate-shaped single crystal manufacturing raw material mass. Thin plate-shaped single crystal manufacturing equipment. The elevating means
It is a winding means for continuously winding the manufactured thin plate-shaped single crystal into a roll shape.
The winding means
A winding shaft that continuously winds the thin plate-shaped single crystal, and
A rotating means for rotating the winding shaft and
Equipped with
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 3, wherein the thin plate-shaped seed single crystal is suspended from the winding shaft. The thin plate-shaped seed single crystal
The thin plate-shaped single crystal manufacturing apparatus according to claim 4, wherein the thin plate-shaped single crystal manufacturing apparatus is suspended from the winding shaft via a plurality of thin wires. In the thin plate-shaped seed single crystal,
The thickness of the part where the thin wire is attached is
The thin plate-shaped single crystal manufacturing apparatus according to claim 5, wherein the size is equal to or less than the thickness of the thin plate-shaped single crystal to be manufactured. On the upper side surface of the raw material mass for producing a thin plate-shaped single crystal,
The thin plate-shaped single according to any one of claims 1 to 6, wherein a required amount of a liquid phase composition that coexists in equilibrium with the composition of the thin plate-shaped single crystal to be produced is first arranged. Crystal manufacturing equipment. Between the elevating means and the raw material mass for producing a thin plate-shaped single crystal,
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 7, further comprising an anti-sway member for preventing the thin plate-shaped single crystal that is continuously manufactured from shaking. Between the elevating means and the raw material mass for producing a thin plate-shaped single crystal,
The invention according to any one of claims 1 to 8, wherein a shielding member is provided so as to prevent the radiant heat generated from the melt from reaching the continuously produced thin plate-shaped single crystal. The thin plate-shaped single crystal manufacturing apparatus according to the above. The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 9, wherein the raw material mass for manufacturing the thin plate-shaped single crystal is a substantially rectangular parallelepiped. The size of the upper side surface of the raw material mass for producing the thin plate-shaped single crystal shall be set to be several mm or more larger in both the thickness direction and the lateral direction than the size of the lower side surface of the thin plate-shaped seed single crystal. The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 10. A mounting table on which the raw material mass for producing a thin plate-shaped single crystal is placed, and
A position control means for controlling the position of the pedestal described above so as to be a predetermined position,
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 11. The elevating means
The claim is characterized in that the lower side surface of the thin plate-shaped seed single crystal is immersed in the center of the melt on the upper side surface of the raw material mass for producing a thin plate-shaped single crystal melted by the infrared irradiation means. Item 2. The thin plate-shaped single crystal manufacturing apparatus according to any one of Items 1 to 12. Around the raw material mass for producing a thin plate-shaped single crystal,
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 13, wherein a preheating means for preheating the raw material mass for manufacturing the thin plate-shaped single crystal is provided. At least the raw material mass for producing a thin plate-shaped single crystal is arranged in the chamber.
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 14, wherein the elevating means is arranged in an upper portion of the chamber. The thin plate-shaped single crystal manufacturing apparatus according to claim 15, further comprising a gas introducing apparatus for filling the inside of the chamber with an atmospheric gas containing an additive. The elevating means
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 16, wherein a plurality of the thin plate-shaped single crystal manufacturing raw material lumps are provided above the raw material mass. The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 17, wherein the thickness of the thin plate-shaped seed single crystal is in the range of 300 μm to 500 μm. A melting step of irradiating the upper side surface of the raw material mass for producing a thin plate-shaped single crystal with infrared rays via an infrared irradiation means to melt the surface of the upper side surface of the raw material mass for producing a thin plate-shaped single crystal.
In the melting step, the lower side surface of the thin plate-shaped single crystal is dipped in the melt obtained on the surface of the upper side surface of the raw material mass for producing the thin plate-shaped single crystal via an elevating means, and the thin plate-shaped single crystal is used. A growing step of starting the growing of a single crystal from the lower side surface of the crystal, and
In the growing step, the thin plate-shaped seed single crystal from which the growth of the single crystal was started is pulled upward to continuously produce the thin plate-shaped single crystal, and the continuous manufacturing step.
A method for producing a thin plate-shaped single crystal, which comprises at least. In the melting step,
The thin plate-shaped single crystal manufacturing method according to claim 19, wherein the infrared rays emitted from the infrared irradiation means are laser light. In the melting step,
The shape of the irradiation area of the laser beam is a hollow square shape elongated in the horizontal direction.
20. Thin plate-shaped single crystal manufacturing method. After the continuous manufacturing process
A winding process in which the continuously manufactured thin plate-shaped single crystal is wound into a roll,
The thin plate-shaped single crystal manufacturing method according to any one of claims 19 to 21, further comprising. In the melting step,
When the thin plate-shaped single crystal to be produced is a decomposition-melting substance, a liquid phase composition that coexists in equilibrium with the composition is first placed in a required amount on the upper side surface of the raw material mass for producing the thin plate-shaped single crystal. The thin plate-shaped single crystal manufacturing method according to any one of claims 19 to 22, wherein the thin plate-shaped single crystal is kept. In the melting step,
When the thin plate-shaped single crystal to be produced is a solid solution substance containing an additive, the composition of the liquid phase coexisting in equilibrium with the composition is first applied in a required amount on the raw material mass for producing the thin plate-shaped single crystal. The thin plate-shaped single crystal manufacturing method according to any one of claims 19 to 22, wherein the thin plate-shaped single crystal is arranged on the side surface. In the growing process,
19. The method for producing a thin plate-shaped single crystal according to item 1.

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