JP7690184B2 - Thin plate single crystal manufacturing apparatus and thin plate single crystal manufacturing method - Google Patents

Description

The present invention relates to a thin plate single crystal manufacturing apparatus and a thin plate single crystal manufacturing method that can continuously manufacture thin plate single crystals with a thickness of about several hundred μm.

In recent years, there has been a call for a shift from fossil fuels to renewable energy, and a shift from power generation methods that consume petroleum to power generation methods using solar cells that utilize sunlight is underway on a global scale. However, the cost of generating electricity from solar power remains high compared to other power generation methods, and there is a demand for the development of highly efficient, inexpensive solar cells.

Various materials are known as substrate materials that make up solar cells, including semiconductor silicon crystal, amorphous silicon, and compound semiconductor crystal, and development is underway for each of these. Among these, semiconductor silicon crystal is the main substrate material. A standard size for a substrate is about 155 mm square and 0.3 mm thick. This standard size silicon crystal substrate is treated to enable highly efficient solar power generation, and a product in which electrodes are attached to extract the generated electricity is called a "cell," and a product in which many of these cells are arranged in a planar form is called a "module." This module is installed according to the usage environment and used as a solar power generation device.

To reduce the cost of generating electricity from solar cells, it is important to improve the performance of the substrate, which is a main component of the cell and is made of semiconductor silicon crystals, and to develop new manufacturing methods that can reduce the manufacturing costs of substrate materials from current levels.

By the way, the structure of a solar cell that is said to be able to achieve highly efficient power generation as a solar cell is HIT (Heterojunction) which expands the wavelength range of available sunlight by sandwiching a phosphorus-doped N-type silicon single crystal plate between amorphous silicon layers on both sides.
There is a method called the "with Intrinsic Thin-layer" type.

The most efficient method is said to be the combination of this HIT type method, in which all electrodes for extracting the generated electricity are concentrated on the back side, with no electrodes on the front side, and a back contact type method. In the N-type silicon single crystal substrate used here, phosphorus must be added homogeneously in an optimal composition.

Currently, there are two main methods for manufacturing silicon crystal substrates for general-purpose solar cells. The first method is a unidirectional solidification method in which the raw material is melted in a large quartz crucible and solidified from the bottom up, and the resulting large crystal mass is cut into general-purpose sizes to produce crystal substrates.

However, the crystal mass produced by this method is a P-type polycrystal with added boron, and in principle, this unidirectional solidification method cannot produce the N-type single crystal substrate required for the highly efficient solar cells mentioned above.

The second method is to melt the raw material in a quartz crucible, immerse a seed single crystal in the resulting melt, and pull it upwards while thickening it, a process known as the pulling method, to produce a rod-shaped single crystal, which is then cut and processed to produce single crystal substrates of standard sizes.

This pulling method has two major problems. The first problem is that the manufacturing cost is very high.
The manufacturing cost of single crystal ingots obtained by the pulling method increases as the diameter of the single crystal ingot increases. To obtain a substrate of general size, a single crystal ingot with a diameter of about 250 mm is required, but in order to reduce manufacturing costs, a single crystal ingot with a diameter of about 200 mm is used to manufacture a substrate of general size. Therefore, the four corners of the square are chipped, and the efficiency is naturally lower than that of a product with a precise square shape.

The second problem with the pulling method is that it is not possible to homogenize the concentration of phosphorus added to make it N-type. When phosphorus is added to raw silicon and melted, the phosphorus concentration in the molten liquid is homogenous, but the phosphorus concentration in the portion that first solidifies as a single crystal is lower than the phosphorus concentration in the melt. This phenomenon is called the "distribution phenomenon," and the ratio of the phosphorus concentration in the melt to the phosphorus concentration in the solidified material is called the "distribution coefficient."

In the case of silicon, the distribution coefficient of phosphorus is approximately 0.35, so the phosphorus concentration in the first solidified portion is low, and the difference remains in the melt. As a result, as solidification progresses, the phosphorus concentration in the melt increases, and accordingly, the phosphorus concentration in the solidified material also increases according to the distribution coefficient. Therefore, the optimal composition portion is limited to a portion of the obtained single crystal.

Moreover, once about half of the raw material initially melted in the crucible has solidified, the phosphorus concentration becomes too high and it is no longer usable for solar cells. Therefore, the production process is stopped, the atmosphere inside the production furnace is kept at an inert gas atmosphere, the product is removed while maintaining the raw material melt temperature, new granular raw material is replenished into the remaining raw material melt to return it to the original raw material melt composition, and the production of the second single crystal is resumed.

With this manufacturing method, the quartz crucible that holds the raw material melt is worn out, so it can only be used twice, or at most three times if a specially prepared high-quality quartz crucible is used.

The biggest problem with this manufacturing method is that it is not possible to make the phosphorus concentration in the product uniform. High efficiency can be achieved by manufacturing solar cells using only optimal composition products, but the optimal composition products have a low yield rate, so they are expensive, which directly leads to higher power generation costs.

Therefore, if an attempt is made to reduce costs by using a composition with a phosphorus concentration that is either too low or too high compared to the optimum composition, the power generation efficiency of the module will naturally be degraded.
In addition to the above, methods for reducing the manufacturing costs of silicon single crystal substrates for solar cells have been vigorously developed. It goes without saying that there is a high possibility of reducing cutting losses and production costs by manufacturing a thin single crystal plate of a specified thickness from the beginning and then cutting it to a specified size, rather than cutting a large crystal block to produce a thin single crystal plate.

There are three methods for producing silicon thin plate crystals that have been reported so far.
The first method is a method in which a jig with a slit, called a die (DIE), is inserted into the raw material melt melted in a crucible, and a thin plate-shaped seed single crystal is immersed in the raw material melt that comes out of the slit of the die (DIE) due to surface tension, and is pulled upward while being solidified, thereby producing a thin plate-shaped single crystal, and is called the EFG (Edge defined Film-fed Growth) method.

This manufacturing method has been vigorously developed, mainly in the United States, but it has not yet been put to practical use for manufacturing silicon substrates for solar cells. The reasons for this include the lack of materials for jigs that can withstand stable long-term use, the difficulty of controlling the temperature when the raw material melt solidifies, and the difficulty of enlarging the size of the process.

The second method is called the Edge Stabilized Ribbon (ESR) method, and uses a string instead of the die (DIE) mentioned above. In this ESR method, a string is first immersed in the surface of the raw material melt and attached horizontally, and when it is lifted slightly upwards, the raw material melt that is lifted along with the string due to surface tension solidifies and becomes a thin plate-like crystal.

If a string is attached to both sides of the string and they are pulled upward together, the solidified thin plate-like crystals will grow and be pulled upward together. However, with this method, the part that is first lifted by the strings and solidifies is "polycrystalline", and the thin plate that grows along with it is also "polycrystalline" and does not become a "single crystal".

The third method is called the dendritic web growth method. Dendrites have the property that when their growth rate reaches a certain speed, they grow preferentially in the direction with the highest thermal conductivity. This method utilizes this property of dendrites to produce thin plate-like crystals.

This method does not use jigs or strings like the EFG and ESR methods, and it is said that it is possible to grow single crystals if the growth is optimally controlled. However, in reality, single crystals cannot be produced unless the initial dendrites (branched crystals) are made into a single crystal, so there are no examples of this method being used to continuously grow large, long, thin plate-shaped single crystals, and it has not yet been used for industrial production.

On the other hand, as mentioned above, all of the methods for producing thin plate crystals reported so far are methods for producing crystals by holding a silicon melt in a quartz crucible. When raw silicon is melted in a quartz crucible as in these production methods, the silicon melt reacts with the quartz to produce silicon monoxide (SiO), as shown in formula 1.

The silicon monoxide (SiO) produced by the reaction is mixed into the silicon crystal product as a solid solution, and is the main cause of the deterioration of the performance of the single crystal. Therefore, in order to produce high-quality single crystals, a manufacturing method that does not require the use of a quartz crucible is desirable.

Currently, a high-frequency floating zone melting method has been put into practical use as a method for producing silicon single crystals without using a crucible, in which a raw material rod is melted and solidified using high-frequency induction heating to produce single crystals (see, for example, Patent Document 1). This high-frequency floating zone melting method produces high-purity single crystals that do not contain silicon monoxide (SiO) in the product.

However, the raw material rods that can be used in the high-frequency floating zone melting method are specially prepared, highly dense products, and such raw material rods are expensive and the supply is limited, making them unsuitable for solar cells, which are expected to be low-cost. Furthermore, using this high-frequency floating zone melting method, it is extremely difficult to produce thin plate-shaped single crystals, and there have been no reports of such production.

Another method for producing high-purity single crystals without using a crucible is known to use infrared rays. One method for producing single crystals using infrared rays is the infrared floating zone melting method, in which raw material powder is processed into a rod shape, which is then locally heated to melt and solidify it to produce a single crystal rod.

In this infrared floating zone melting method, a molten liquid formed by infrared heating is held on a raw material rod by the surface tension of the molten liquid itself, allowing the raw material to continue to melt and solidify.
In the infrared floating zone melting method, the infrared rays have been irradiated from a horizontal direction in the past, but this method of irradiating from a horizontal direction cannot, in principle, produce single crystals with a large diameter.

The top surface melting method was developed, which melts the top surface of a large diameter seed single crystal placed at the bottom by irradiating it with infrared rays and dripping the molten raw material onto it, making it possible to produce single crystals with a large diameter. This top surface melting method has, in principle, eliminated any limitations on the diameter of single crystals that can be produced, dramatically expanding its range of application.

On the other hand, in addition to the solar cell materials mentioned above, many oxide materials are currently used as industrial single crystal materials, such as the ferroelectric materials lithium niobate and lithium tantalate, the phosphor materials lutetium silicate and gadolinium silicate, and the laser materials yttrium aluminum garnet and gadolinium gallium garnet.

These oxide materials are produced in the form of rod-shaped single crystals by the pulling method, which are then cut and processed into thin plate-shaped single crystals with a thickness of approximately 0.3 mm for use in the manufacture of various devices. However, the pulling method inevitably results in contamination of the product from the crucible material, and due to the distribution phenomenon mentioned above, it is in principle impossible to homogenize the concentration of useful additives in the product. This creates problems for the manufacture of high-quality devices.

Therefore, rather than producing a rod-shaped single crystal and then cutting it into a thin plate-shaped single crystal for use, it is possible to produce a high-performance product at a much lower cost by producing a thin plate-shaped single crystal with the optimal composition and a specified thickness from the beginning.

Patent No. 5279727

However, research and development into the manufacturing method of thin single crystals has not produced sufficient results to date, and the only known examples of manufacturing thin single crystals for industrial use are the manufacture of sapphire single crystal plates and gallium oxide single crystal plates using the EFG method.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a thin plate single crystal manufacturing apparatus and a thin plate single crystal manufacturing method that can manufacture thin plate single crystals having an optimal and homogeneous additive concentration and a thickness of several hundred μm continuously and with high precision at low cost.

The present invention has been invented to solve the problems in the prior art described above,
The thin plate single crystal manufacturing apparatus of the present invention comprises:
an infrared ray irradiating means for irradiating an upper side surface of a raw material lump for producing a thin plate-shaped single crystal (hereinafter also referred to as raw material lump) with infrared rays to melt the surface of the upper side surface;
a lifting means for immersing a lower surface of the thin plate-shaped seed single crystal in the melt obtained on the upper surface of the thin plate-shaped seed single crystal by the infrared irradiation means and lifting the thin plate-shaped seed single crystal upward from the immersed state;
Equipped with
The method is characterized in that the lower side of the thin plate-shaped seed single crystal is immersed in the molten liquid obtained on the upper surface of the raw material block for producing the thin plate-shaped single crystal via the lifting means, and single crystal growth begins from the lower side of the immersed thin plate-shaped seed single crystal, and the thin plate-shaped seed single crystal is further pulled upward via the lifting means, thereby continuously producing thin plate-shaped single crystals.

With this configuration, the number of components constituting the device is small, the additive concentration is optimal and homogeneous, and thin plate-shaped single crystals with thicknesses of several hundred micrometers can be produced continuously and with high precision at low cost. Furthermore, it is possible to produce homogeneous-composition thin plate-shaped single crystals of so-called incongruent melting substances, such as decomposed melting substances and solid solution substances, with high precision.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The infrared ray irradiated from the infrared ray irradiating means is a laser beam.
In this way, laser light can accurately heat a specified area of the raw material block, so that the melt (melt puddle) can be reliably formed without spilling over the upper side of the raw material block.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The shape of the irradiation area of the laser light is a hollow rectangle that is elongated in the horizontal direction,
The method is characterized in that the laser light is irradiated onto the peripheral region excluding the central portion of the upper side of the raw material lump for producing the thin plate-shaped single crystal so as to form the hollow rectangular irradiation region.

In this way, if the laser light is irradiated so as to coincide with the peripheral region of the upper side of the raw material lump, excluding the center, to form a hollow rectangular irradiation area, the peripheral region of the upper side of the raw material lump, excluding the center, will melt first, and the center, which is not hit by the laser light, will melt due to thermal conduction from the molten liquid in the peripheral region that was melted first.

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

Furthermore, the laser light may be irradiated onto the upper surface of the raw material lump from an oblique upward direction or from directly above in a vertical direction, but it is preferable that the irradiation angle be adjustable to an optimal angle depending on the thermal conductivity characteristics of the single crystal material and the thickness of the thin plate-shaped single crystal to be produced.
In order to continuously produce a thin plate-shaped single crystal by melting a raw material lump, it is necessary to simultaneously continue melting the raw material lump and solidifying it into a thin plate-shaped single crystal. However, the melting of the raw material lump requires heating, and the solidification of the thin plate-shaped single crystal requires cooling the melt.

Therefore, in order to enable the stable production of thin plate single crystals, it is essential to continue the opposing actions of "heating" and "cooling" stably with good controllability. This can be achieved by irradiating the raw material lump with the hollow rectangular laser light described above.
That is, by providing such a temperature distribution in the melt pool on the upper side of the raw material lump, a thin plate-shaped single crystal can be stably and continuously grown from the center.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The lifting means is
a winding means for continuously winding up the produced thin plate-like single crystal into a roll,
The winding means is
a winding shaft for continuously winding the thin plate-like single crystal;
A rotating means for rotating the winding shaft;
Equipped with
The thin plate-shaped seed single crystal is configured to be suspended from the winding shaft.

If the winding means is configured in this way, the continuously produced thin plate single crystals can be reliably wound around the winding shaft, and the device does not need to be made larger than necessary. Furthermore, since the produced thin plate single crystals are in a roll shape, they can be easily transported during shipping, improving handleability.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The thin plate-like seed single crystal is
It is characterized in that it is suspended from the winding shaft via a plurality of thin wires.
By suspending the thin plate-shaped seed single crystal in this manner using 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 a winding shaft.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
In the thin plate-shaped seed single crystal,
The thickness of the portion to which the thin wire is attached is
It is preferable that the size is equal to or smaller than the thickness of the thin plate-like single crystal to be produced.

In this way, if the thickness of the thin plate-shaped seed single crystal at the portion where the thin wire is attached is set to a size equal to or smaller than the thickness of the thin plate-shaped single crystal to be produced, it is possible to reliably prevent the surface of the thin plate-shaped single crystal from coming into contact with the thin wire and causing damage when the thin plate-shaped single crystal is wound around the winding shaft.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The upper surface of the raw material block for producing a thin plate-shaped single crystal is
The method is characterized in that a required amount of a liquid phase composition which coexists in equilibrium with the composition of the thin plate-like single crystal to be produced is initially placed.

In this way, if the required amount of liquid phase composition that coexists in equilibrium with the composition of the thin plate single crystal to be produced is placed on the upper surface of the raw material block from the beginning, thin plate single crystals that are homogeneous and have the optimal composition can be continuously produced.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
Between the lifting means and the raw material block for producing a thin plate-shaped single crystal,
The present invention is characterized in that an anti-vibration member is provided to prevent the thin plate-shaped single crystals being continuously produced from vibrating.

If anti-vibration members are provided in this way, the produced thin plate single crystal can be prevented from vibrating too much from side to side. This means that the growth position can be kept within a specified range without shifting, allowing for the continuous and stable production of high-quality thin plate single crystals.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
Between the lifting means and the raw material block for producing a thin plate-shaped single crystal,
It is preferable that a shielding member is provided to prevent radiant heat generated from the melt from reaching the thin plate-shaped single crystal being continuously produced.

The thin plate single crystal solidifies as it is pulled up from the melt, but if the radiant heat emitted from the melt reaches the produced thin plate single crystal, it becomes difficult to increase the production speed of the thin plate single crystal. Therefore, by providing a shielding member, it becomes difficult for the radiant heat from the melt to reach the produced thin plate single crystal, and the production efficiency of the thin plate single crystal can be improved.

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

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The size of the upper side of the raw material block for producing the thin plate-shaped single crystal is set to be several mm or more larger in both the thickness direction and the width direction than the size of the lower side of the thin plate-shaped seed single crystal.

By setting the size of the raw material block and the thin plate-shaped seed single crystal in this way, the entire underside of the thin plate-shaped seed single crystal can be immersed in the melt, and thin plate-shaped single crystals of the desired size can be continuously produced.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
a mounting table for mounting the raw material block for producing the thin plate-shaped single crystal;
a position control means for controlling the position of the mounting table so that the position of the mounting table is at a predetermined position;
The present invention is characterized by comprising:

By making it possible to control the position of the mounting table (especially the vertical position) in this way, even if the liquid level of the molten raw material drops as the thin plate single crystal is pulled up, the position of the raw material can be raised to maintain its original position, and the liquid level can be controlled to always be at the same position. Therefore, it is only necessary to always fix the infrared irradiation position at the same position, and thin plate single crystals can be produced stably and continuously with high yield.
In addition, when the laser light traveling parallel to the raw material lump is irradiated from a direction perpendicular to the upper surface of the raw material lump, the irradiation intensity of the laser light does not change even if the liquid level of the molten raw material lump drops, so there is no need to perform position control to maintain the liquid level of the molten raw material lump constant.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The lifting means is
The method is characterized in that the lower surface of the thin plate-shaped seed single crystal is immersed in the center of the molten liquid on the upper surface of the raw material lump for producing the thin plate-shaped single crystal melted by the infrared ray irradiation means.

The center of the melt is where the melt accumulates continuously, and by immersing the underside of the thin plate-shaped seed single crystal in this center, the thin plate-shaped seed single crystal can be pulled upwards using a lifting means, allowing the thin plate-shaped single crystal to be produced continuously.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The raw material block for producing the thin plate-shaped single crystal is surrounded by:
The apparatus is characterized in that it is provided with a preheating means for preheating the raw material block for producing the thin plate-shaped single crystal.

By preheating the raw material block to near its melting point in this way, it is possible to reduce the amount of infrared radiation emitted by the infrared radiation 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 precision.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
At least the raw material block for producing the thin plate-shaped single crystal is disposed in a chamber,
It is preferable that the lifting means is disposed at an upper portion of the chamber.
If the raw material block is disposed in the chamber in this manner, a thin plate-shaped single crystal can be produced in an atmosphere suited to the single crystal material.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The present invention is characterized by including a gas introduction device that fills the inside of the chamber with an atmospheric gas containing an additive.

By equipping the chamber with a gas introduction device like this, the atmosphere inside can be tailored to the characteristics of the material from which the thin plate single crystal is being produced, making it possible to produce homogeneous, high-quality thin plate single crystals with an optimal additive concentration.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The lifting means is
The present invention is characterized in that a plurality of such nozzles are provided on the upper portion of the raw material block for producing the thin plate-shaped single crystal.

With this configuration, for example, multiple thin plate-shaped seed single crystals can be lined up and immersed in one melt pool, and each can be pulled up to the top by a lifting means, which can dramatically improve the production efficiency of thin plate-shaped single crystals compared to when only one lifting means is used.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The thickness of the thin plate-like seed single crystal is preferably within a range of 300 μm to 500 μm.
With such a thickness, a high purity thin plate single crystal can be continuously produced and wound up to achieve a long length.

The thin plate single crystal manufacturing apparatus of the present invention further comprises:
The thickness of the thin plate-like single crystal is preferably within the range of 100 μm to 3000 μm.
The thickness of the thin plate single crystal produced can be in the range of 100 μm to 3000 μm, but when it is assumed that the crystal will be wound by a winding means, the thickness is preferably in the range of 100 μm to 500 μm. However, the thickness 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 thin plate single crystals thicker than 500 μm, the diameter of the thin plate single crystal when wound around the winding shaft of the winding means becomes large. In this case, it is possible to produce the product by pulling it upwards without winding it. In particular, when manufacturing thin plate single crystals of silicon for solar cells, it is preferable that the thickness of the thin plate single crystal is within the range of 200 μm to 400 μm.

The method for producing a thin plate-like single crystal of the present invention further comprises the steps of:
a melting step of irradiating an upper side surface of the raw material lump for producing a thin plate-shaped single crystal with infrared rays via an infrared ray irradiation means to melt the surface of the upper side surface of the raw material lump for producing a thin plate-shaped single crystal;
a growing step of immersing a lower surface of the thin plate-shaped seed single crystal in the melt obtained on the upper surface of the raw material lump for producing the thin plate-shaped single crystal by using an elevating means, and starting the growth of the single crystal from the lower surface of the thin plate-shaped seed single crystal;
a continuous production step of pulling the thin plate-shaped seed single crystal upward after the single crystal growth has started in the growth step, and continuously producing the thin plate-shaped single crystal;
It is characterized by having at least the following.
This manufacturing method allows for the continuous and highly accurate production of thin plate single crystals having an optimum additive concentration and a homogeneous composition and a thickness of approximately several hundred μm at low cost.

The method for producing a thin plate-like single crystal of the present invention further comprises the steps of:
In the melting step,
The infrared ray irradiated from the infrared ray irradiating means is a laser beam.

In this way, laser light can accurately heat a specific area of the raw material block in the required shape, so the melt does not spill over the upper side of the raw material block, and a melt pool can be reliably formed.

The method for producing a thin plate-like single crystal of the present invention further comprises the steps of:
In the melting step,
The shape of the irradiation area of the laser light is a hollow rectangle that is elongated in the horizontal direction,
The method is characterized in that the laser light is irradiated onto the peripheral region excluding the central portion of the upper side of the raw material lump for producing the thin plate-shaped single crystal so as to form the hollow rectangular irradiation region.

In this way, if the laser light is irradiated so as to coincide with the peripheral region of the upper side of the raw material lump, excluding the center, to form a hollow rectangular irradiation area, the peripheral region of the upper side of the raw material lump, excluding the center, will melt first, and the center, which is not hit by the laser light, will melt due to thermal conduction from the molten liquid in the peripheral region that was melted first.

Therefore, the temperature of the central portion can be controlled to be lower than that of the peripheral portion, which allows the opposing actions of melting the raw material mass and solidifying it from the melt to be continued stably and with good controllability.
That is, by providing such a temperature distribution in the melt pool on the upper side of the raw material lump, a thin plate-shaped single crystal can be stably and continuously grown from the center.

The laser light may be irradiated onto the upper surface of the raw material lump from an oblique upward direction, or vertically from directly above, but it is preferable to adjust the irradiation angle to an optimal angle depending on the thermal conductivity and thickness of the thin plate-shaped single crystal material. In the case of a material with high thermal conductivity, it is preferable to control the irradiation angle of the laser light to a large angle from the horizontal direction, and in the case of a material with low thermal conductivity, it is preferable to control the irradiation angle of the laser light to a small angle from the horizontal direction.

The method for producing a thin plate-like single crystal of the present invention further comprises the steps of:
After the continuous manufacturing process,
a winding step of winding the continuously produced thin plate-like single crystal into a roll;
The present invention is characterized by further comprising:
By including such a winding step, the continuously produced thin plate-shaped single crystal can be reliably wound into a roll, and thus the thin plate-shaped single crystal can be produced efficiently.

The method for producing a thin plate-like single crystal of the present invention further comprises the steps of:
In the melting step,
When the thin plate-shaped single crystal to be produced is a decomposed molten substance, a required amount of a liquid phase (called a solvent phase) composition that coexists in equilibrium with the composition of the decomposed molten substance is first placed on the upper side of the raw material block for producing the thin plate-shaped single crystal.

Furthermore, the method for producing a thin plate-like single crystal of the present invention comprises the steps of:
In the melting step,
When the thin plate-shaped single crystal to be produced is a solid solution material containing an additive, a required amount of a liquid phase (called a solvent phase) composition that coexists in equilibrium with the composition of the solid solution is first placed on the upper surface of the raw material block for producing the thin plate-shaped single crystal.

As a result, when a thin plate-shaped single crystal solidifies from the solvent phase that first forms on the upper surface of the raw material lump, the amount of the solvent phase decreases and the composition becomes less crystalline. Therefore, the intensity of the laser light reaches the lower side of the solvent phase and the temperature rises, which causes the raw material lump to melt.

As a result, crystallization and melting of the raw material mass proceed simultaneously, so the additive concentration in the resulting product (thin plate single crystal) is the same as that in the raw material mass, making it homogeneous. This scheme is called the "solvent transfer method," and is the only means by which single crystal products of homogeneous composition can be produced using the melt method.

In this way, by initially placing the required amount of liquid phase composition that is in equilibrium with the composition of the thin plate single crystal to be produced on the upper surface of the raw material mass, it is possible to continuously produce thin plate single crystals that are homogeneous and have the optimal composition.

The method for producing a thin plate-like single crystal of the present invention further comprises the steps of:
In the growing step,
The method is characterized in that the lower surface of the thin plate-shaped seed single crystal is immersed in the center of the melt on the surface of the upper surface of the molten raw material lump for producing the thin plate-shaped single crystal.

The center of the melt is where the melt accumulates continuously, and by immersing the underside of the thin plate-shaped seed single crystal in this center, the thin plate-shaped seed single crystal can be pulled upwards using a lifting means, allowing the thin plate-shaped single crystal to be produced continuously.

According to the thin plate single crystal manufacturing apparatus and thin plate single crystal manufacturing method of the present invention, the upper surface of the raw material block for manufacturing the thin plate single crystal is melted with infrared rays to form a melt, and a thin plate seed single crystal is immersed in this melt and pulled upward, making it possible to continuously and precisely manufacture thin plate single crystals with a thickness of several hundred micrometers that have an optimal additive concentration and are homogeneous.

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

The thin plate single crystal manufacturing apparatus and the thin plate single crystal manufacturing method of the present invention will be described in more detail below with reference to the drawings.
The thin plate single crystal manufacturing apparatus and method of the present invention are intended to produce thin plate single crystals having an optimal additive concentration and a homogeneous composition, and having a thickness of approximately several hundred μm, continuously and with high precision at low cost.

<Thin Plate Single Crystal Manufacturing Apparatus 10>
[First embodiment]
1, in the apparatus 10 for producing a thin plate-shaped single crystal according to the first embodiment of the present invention, a raw material lump for producing a thin plate-shaped single crystal (hereinafter also referred to as raw material lump) 12 is provided on a mounting table 82 disposed at the bottom inside a chamber 80. The raw material lump 12 has a substantially rectangular parallelepiped shape, for example, a plate-like body like a book.

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

In other words, as shown in FIG. 2, it is preferable to make the shape of the irradiation area of the laser light 16a a horizontally elongated hollow rectangular shape (vertical direction in FIG. 2), and to irradiate the laser light 16a so as to match it to the peripheral area of the upper side surface 14 of the raw material lump 12 excluding the center, so as to form this horizontally elongated hollow rectangular irradiation area, as shown in FIG. 3.

Here, it is preferable that the laser light 16a emitted from the infrared irradiation means 20 enters the chamber 80 through a window 22 provided on the side of the chamber 80 and is irradiated via a reflector 24 in the chamber 80 to the peripheral region of the upper surface 14 of the raw material lump 12 excluding the center. At this time, the laser light 16a may be irradiated from an obliquely upward direction to the upper surface 14 of the raw material lump 12 as shown in FIG. 1, or may be irradiated from directly above in a vertical direction to the upper surface 14 of the raw material lump 12 as shown in FIG. 4, but the irradiation angle is controlled to an optimal angle in accordance with 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 of the upper surface 14 of the raw material lump 12, excluding the center, melts before the center, and the center, which is not hit by the laser light 16a, melts due to thermal conduction from the molten liquid 18 in the peripheral region that melted first.

Therefore, the temperature of the center can be controlled to be lower than the temperature of the peripheral region, and by providing such a temperature distribution to the melt 18 (melt pool) on the upper surface 14 of the raw material lump 12, the growth of a thin plate-shaped single crystal 40 can be performed stably and continuously from the center.

That is, as shown in Figures 5 and 6, by irradiating the peripheral region of the upper surface 14 of the raw material lump 12, excluding the center, with laser light 16a, melt 18 is formed deeper in the peripheral region, and melt 18 at a lower temperature is formed shallower in the center than in the peripheral region.

As shown in Figures 1, 3 and 4, a preheating means 70 for preheating the raw material lump 12 is provided around the raw material lump 12, and it is preferable to preheat the raw material lump 12 to near its melting point before melting the surface of the upper side 14 of the raw material lump 12 with the infrared irradiation means 20. By preheating in this way, the amount of infrared rays 16 irradiated by the infrared irradiation means 20 can be significantly reduced, and the range of the melt 18 (melt pool) can be fine-tuned by fine-tuning the position and amount of irradiation.

On the other hand, above the chamber 80, a lifting means 30 is provided for immersing the lower surface 34 of the thin seed single crystal 32 in the molten liquid 18 obtained on the surface of the upper surface 14 of the raw material lump 12, which is melted by the infrared irradiation means 20, and for lifting the thin seed single crystal 32 upward from the immersed state.

The lifting means 30 is not particularly limited, but is preferably, for example, a winding means 50 that continuously winds the manufactured thin plate single crystal 40 into a roll. Specifically, it has a winding shaft 36 that continuously winds the manufactured thin plate single crystal 40, and a rotating means 38 that rotates the winding shaft 36.

Here, the size of the underside 34 of the thin plate-shaped seed single crystal 32 is set to be slightly smaller than the upper side 14 of the raw material lump 12. For example, as a specific relationship between the sizes of the two, the size of the upper side 14 of the raw material lump 12 is set to be several mm or more larger in both the thickness direction and the lateral direction than the size of the underside 34 of the thin plate-shaped seed single crystal 32. In other words, the size is set so that the entire underside 34 of the thin plate-shaped seed single crystal 32 can be immersed in the melt 18.

Then, as shown in FIG. 7, the lower surface 34 of the thin plate-shaped seed single crystal 32 is immersed in the center of the melt 18 obtained on the surface of the upper surface 14 of the raw material lump 12 by the infrared irradiation means 20 via the lifting means 30, and the growth of a single crystal begins from the lower surface 34 of the immersed thin plate-shaped seed single crystal 32. The thin plate-shaped seed single crystal 32 is then pulled upward via the lifting means 30, and the thin plate-shaped single crystal 40 is continuously produced.

The thickness of the thin plate-shaped single crystal 40 produced can be adjusted in a steady state by the melt temperature and the pulling speed of the thin plate-shaped seed single crystal 32, and can be, for example, from 100 μm to more than 3000 μm. However, if the thickness of the thin plate-shaped single crystal 40 exceeds 500 μm, the winding means 50 will become too large, so if it exceeds 500 μm, it can be pulled upward without being wound to produce a product. In particular, when producing thin plate-shaped single crystals of silicon for solar cells, it is preferable that the thickness of the thin plate-shaped single crystal 40 is within 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 to grow the thin plate single crystal 40 increases, so the pulling speed is slowed down, and when the melt temperature is low, the pulling speed of the thin plate single crystal 40 is increased, thereby increasing the productivity of the thin plate single crystal 40. However, if the pulling speed is too fast, so-called "cell growth" is likely to occur, and the crystal properties of the thin plate single crystal 40 will deteriorate, so it is preferable to adjust the pulling speed appropriately.

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. A thin plate-shaped seed single crystal 32 of this thickness is preferable because it is possible to continuously produce a thin plate-shaped single crystal 40 of the desired thickness by adjusting the melt temperature and pulling speed.

In addition, in Figures 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 to be different, but this is done intentionally so that the thin plate-shaped single crystal 40 and the thin plate-shaped seed single crystal 32 can be distinguished in the figures, 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 from the winding shaft 36 of the winding means 50 via a plurality of (three in FIG. 7) thin wires 52 that are heat-resistant and high-strength. In particular, if the thickness of the portion of the thin plate-shaped seed single crystal 32 to which the thin wires 52 are attached is set to be equal to or less than the thickness of the thin plate-shaped seed single crystal 32, it is possible to reliably prevent the surface of the thin plate-shaped single crystal 40 from coming into contact with the thin wires 52 and causing damage when the thin plate-shaped single crystal 40 is wound around the winding shaft 36.

The method of attaching the thin wire 52 to the thin seed single crystal 32 is not particularly limited, but for example, it is preferable to provide several through holes at the end of the thin seed single crystal 32 for tying the thin wire 52, and provide grooves on both sides of the thin seed single crystal 32 to connect with the through holes, so that when the thin wire 52 is tied to the thin seed single crystal 32, the thin wire 52 fits into the grooves and does not protrude outward from the thin seed single crystal 32. By doing so, it is possible to reliably prevent the surface of the thin seed single crystal 40 from coming into contact with the thin wire 52 and causing damage when the thin seed single crystal 40 is wound up.

In addition, in the thin plate single crystal manufacturing apparatus 10, it is preferable to provide a vibration prevention member 60 between the lifting means 30 and the raw material lump 12 to prevent the continuously manufactured thin plate single crystals 40 from shaking and to keep the growth position within a predetermined range so as not to shift, and a shielding member 62 to block the radiant heat emitted from the melt 18 so that it does not reach the continuously manufactured thin plate single crystals 40.

By providing the anti-vibration member 60, it is possible to prevent the produced thin plate-shaped single crystal 40 from vibrating too much to the left or right, which would cause the growth position to shift, and it is possible to continuously produce high-quality thin plate-shaped single crystal 40.

The provision of the shielding member 62 also makes it possible to increase the production speed of the thin plate-shaped single crystal 40. In other words, the method of melting the raw material and solidifying it into a single crystal is called the melt method, and the growth speed of the single crystal in this melt method is increased by efficiently dissipating the latent heat of crystallization released when the crystal solidifies through thermal conduction within the single crystal in contact with the melt.

Therefore, for example, if a shielding member 62 is provided so as not to block the optical path of the infrared rays 16 (laser light 16a), the amount of radiant heat reaching the thin plate-shaped single crystal 40 is reduced, and the crystallization latent heat can be efficiently discharged by not increasing the temperature of the thin plate-shaped single crystal 40, thereby improving the manufacturing efficiency of the thin plate-shaped single crystal 40.

In this way, by using the thin plate single crystal manufacturing apparatus 10, thin plate single crystals 40 can be manufactured continuously. However, when the thin plate single crystals 40 are manufactured continuously, the amount of melt 18 obtained on the surface of the upper side 14 of the raw material lump 12 decreases, and the position of the upper side 14 drops. When this happens, it is necessary to control the position of infrared irradiation by the infrared irradiation means 20 so that it is the desired position.

In this embodiment, instead of controlling the irradiation position of the infrared rays 16, the table 82 on which the raw material lump 12 is placed is provided with a position control means 84 that controls the vertical position of the table 82.

By providing such a position control means 84, even if the position of the melt 18 on the upper surface 14 of the raw material lump 12 drops as the continuously produced thin plate-shaped single crystal 40 is pulled up, the mounting table 82 can be raised to keep the position of the melt 18 on the upper surface 14 of the raw material lump 12 at the same position as it was initially, and the liquid surface position of the melt 18 can always be kept at the same position.

Therefore, it is only necessary to always irradiate the same position with the infrared rays 16, and it is possible to stably and continuously produce the thin plate single crystals 40 with good yield. Here, when the laser light 16a is irradiated vertically from directly above the upper surface 14 of the raw material lump 12 as in the thin plate single crystal manufacturing apparatus 10 shown in Figures 4 and 6, the temperature of the melt 18 does not change even if the position of the upper surface 14 of the raw material lump 12 fluctuates, so there is no need to control the position of the upper surface 14 of the raw material lump 12.
The raw material lump 12 used in the above-mentioned thin plate single crystal manufacturing apparatus 10 has the same composition as the material of the thin plate single crystal 40 to be manufactured. However, if the material of the thin plate single crystal 40 is a decomposed melting substance, the intended thin plate single crystal 40 cannot be obtained even if the raw material lump 12 is melted and solidified as it is in the thin plate single crystal manufacturing apparatus 10.

The liquid phase composition that is in equilibrium with the composition of the material of the thin plate-shaped single crystal 40 to be produced is placed on the upper surface 14 of the raw material lump 12 in an amount sufficient for the liquid phase, and this is melted first. In this way, the upper surface 14 of the raw material lump 12 is placed with the dissolved solvent.

When the thin plate-shaped single crystal 40 is produced in this manner, the same amount of raw material lump 12 that solidified as the single crystal is melted, so the amount and composition of the solvent remain unchanged from start to finish, and it appears as if the solvent phase is moving while dissolving the raw material lump 12 and precipitating the single crystal.

This scheme is called the "solvent migration method." When the thin plate single crystal 40 obtained by the thin plate single crystal manufacturing apparatus 10 is a decomposed molten material or a solid solution material containing additives, it is important to use this "solvent migration method" to make the additive concentration in the obtained thin plate single crystal 40 homogenous.

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

The thin plate single crystal manufacturing apparatus 10 shown in Figures 8 and 9 is basically the same in configuration as the thin plate single crystal manufacturing apparatus 10 of the first embodiment shown in Figures 1 to 7, so the same components are given the same reference numbers and detailed descriptions are omitted, and only the differences will be described.

As shown in Figures 8 and 9, the thin plate single crystal manufacturing apparatus 10 in the second embodiment of the present invention differs from the thin plate single crystal manufacturing apparatus 10 in the first embodiment in that the chamber 80 is provided with a gas introduction device 90 that fills the chamber 80 with an atmospheric gas containing an additive.

The gas introduction device 90 is provided on the upper side of the chamber 80, and atmospheric gas is introduced from the gas introduction device 90 into the chamber 80 via an introduction pipe 92. In addition, an exhaust pipe 94 is provided on the lower side of the chamber 80, and the atmospheric gas can be exhausted from this exhaust pipe 94 to the outside of the chamber 80.

This allows the chamber 80 to be kept filled with an atmospheric gas suitable for producing thin plate-shaped single crystals 40, and allows for the continuous production of high-quality thin plate-shaped single crystals 40 with a uniform additive concentration.

The atmospheric gas may be prepared according to the characteristics of the material of the thin plate single crystal 40 being manufactured. For example, when manufacturing a thin plate single crystal of N-type silicon, it is preferable to introduce high-purity argon gas containing an optimal concentration of phosphine ( _PH3 ) into the chamber 80 as the atmospheric gas.

Also, as shown in FIG. 9, for example, a window 22 for guiding the infrared rays 16 (laser light 16a) irradiated from the infrared irradiating means 20 into the chamber 80, and a reflector 24 for guiding the infrared rays 16 (laser light 16a) guided into the chamber 80 to the upper surface 14 of the raw material lump 12, etc., may be covered with a cover member 42, and atmospheric gas may be actively introduced into this cover member 42 from a gas introduction device 90.

By introducing the atmospheric gas into the cover member 42 in this manner, it is possible to prevent evaporation products from the melt 18 from adhering to the window 22, reflector 24, etc., and it is possible to stably and continuously produce high-quality thin plate-shaped single crystals 40 with a homogenous additive concentration with good yield.

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

The thin plate single crystal manufacturing apparatus 10 shown in Figures 10 and 11 has basically the same configuration as the thin plate single crystal manufacturing apparatus 10 of the first embodiment shown in Figures 1 to 7, so the same components are given the same reference numbers and detailed descriptions are omitted, and only the differences will be described.

As shown in Figures 10 and 11, the thin plate single crystal manufacturing apparatus 10 in the third embodiment of the present invention differs from the thin plate single crystal manufacturing apparatus 10 in the first embodiment in that multiple lifting means 30 (two in Figure 10) are provided above the raw material block 12.

Specifically, two lifting means 30 (winding means 50) are provided side by side on the upper part of the chamber 80, and thin plate-shaped seed single crystals 32, 32 are immersed in the molten liquid 18 on the upper surface 14 of the raw material lump 12, and then pulled upward by the lifting means 30, 30 (winding means 50, 50), thereby producing thin plate-shaped single crystals 40, 40, respectively.
When a plurality of lifting means 30 are provided above the raw material ingot 12 in this manner, the production efficiency of the thin plate-shaped single crystal 40 can be significantly improved compared to when only one lifting means 30 is provided.

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

First, as shown in FIG. 12(a), the raw material lump 12 is placed on the mounting table 82 in the chamber 80 to seal the chamber 80, and the thin plate-shaped seed single crystal 32 is placed on the upper part of the upper side of the raw material lump 12 so that the length direction of the raw material lump 12 and the extension direction of 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.

The atmosphere in the chamber 80 is evacuated to a vacuum via an exhaust pipe (not shown), and an atmospheric gas that matches the characteristics of the material of the thin plate-shaped single crystal 40 being manufactured is introduced into the chamber 80 via a gas introduction device (not shown).

Next, the temperature of the raw material lump 12 is raised to near its melting point by the preheating means 70. Next, as shown in FIG. 12(b), infrared rays 16 (laser light 16a) are irradiated onto the upper surface 14 of the raw material lump 12 via the infrared irradiation means 20 to melt the surface of the upper surface 14.

The shape of the irradiation area of the infrared rays 16 (laser light 16a) is a horizontally elongated hollow rectangle, and the laser light 16a is irradiated to the peripheral area of the upper surface 14 of the raw material lump 12, excluding the center, so as to form this horizontally elongated hollow rectangular irradiation area.

As a result, the peripheral region of the upper surface 14 of the raw material lump 12, excluding the center, melts before the center, and the center, which is not hit by the laser light 16a, melts due to thermal conduction from the melt 18 in the peripheral region that melted first.

Next, as shown in FIG. 12(c), the lower surface 34 of the thin seed single crystal 32 is immersed in the center of the melt 18 obtained on the upper surface 14 of the raw material lump 12 via the lifting means 30 (winding means 50), and the growth of the single crystal begins from the lower surface 34 of the thin seed single crystal 32.

Next, as shown in FIG. 13( a ), the thin plate-shaped seed single crystal 32 is pulled upward by the lifting means 30 (winding means 50 ), and the thin plate-shaped single crystal 40 is continuously produced.
13(b), as the thin plate single crystal 40 is continuously produced, the position of the mounting table 82 is moved upward via the position control means 84. As a result, even if the position of the melt 18 of the raw material lump 12 drops as it is pulled up, the position of the raw material lump 12 is controlled so as to maintain the original position, and the liquid surface position of the melt 18 is always kept at the same position.
Here, when laser light 16a is irradiated vertically from directly above the upper surface 14 of raw material lump 12 as in the thin plate single crystal manufacturing apparatus 10 shown in Figures 4 and 6, the temperature of the melt 18 does not change even if the position of the upper surface 14 of raw material lump 12 fluctuates, so there is no need to control the position of the upper surface 14 of raw material lump 12 to a constant position.

Finally, as shown in FIG. 13(c), the amount of infrared rays 16 (laser light 16a) irradiated by the infrared irradiating means 20 is increased to raise the temperature of the melt 18 and separate the thin plate-shaped single crystal 40 from the melt 18. The continuously produced thin plate-shaped single crystal 40 is wound up by the lifting means 30 (winding means 50), and irradiation of infrared rays 16 (laser light 16a) by the infrared irradiating means 20 is terminated, completing the production of the thin plate-shaped single crystal 40.

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

The raw material lump 12 used was a cube having a width of 400 mm, a thickness of 50 mm, and a height of 500 mm.
On the other hand, a thin plate-shaped silicon seed single crystal 32 having a (111) plane and a width of 350 mm, a thickness of 0.3 mm, and a height of 100 mm was used as the thin plate-shaped seed single crystal 32. Silicon has a tendency to have flat surfaces called facets in the (111) plane direction, and this flat surface was used as the plate surface of the thin plate-shaped seed single crystal 32. The thin plate-shaped seed single crystal 32 was attached to the winding shaft 36 of the winding means 50 via three thin wires 52 in advance.

First, the raw material lump 12 was placed on the placement table 82 in the chamber 80, and the chamber 80 was closed to create a vacuum inside the chamber.
Next, an atmospheric gas was introduced into the chamber 80. High purity argon gas was used as the atmospheric gas, and a necessary amount of phosphine (PH ₃ ) gas was added to add phosphorus.

First, the raw material lump 12 is heated to near its melting point by the preheating means 70. Once heating is confirmed, the peripheral region of the upper surface 14 of the raw material lump 12, excluding the center and outermost edge, is irradiated with a laser beam 20 mm wide and 396 mm long from the left and right, at an angle of 60 degrees from the horizontal and 2 mm away from the end, and at the same time, both ends of the length of the raw material lump 12 are irradiated with a laser beam 16a having a right-angled irradiation area shape of 6 mm wide, 2 mm away from the end, on the center line of the raw material lump 12, at an angle of 60 degrees from the horizontal. The overall shape of the irradiation area is a hollow rectangle that is elongated horizontally. This melts the entire upper surface 14.

The winding shaft 36 of the winding means 50 is rotated, and the lower surface 34 of the thin silicon seed single crystal 32 is immersed in the center of the melt 18 obtained by melting. A thin single crystal 40 is grown from the lower surface 34 of the thin seed single crystal 32. Then, the winding shaft 36 is rotated in the opposite direction, and the thin seed single crystal 32 is pulled upward. The thin single crystal 40 is continuously wound in a roll around the winding shaft 36 at the top, producing a long thin single crystal 40 with a length of more than 10 m.

The thin seed single crystal 32 was set on the winding shaft 36 of the winding means 50 with a thin carbon fiber wire 52 having a diameter of about 0.05 mm, and the thin seed single crystal 32 was moved up and down by controlling the rotation direction and rotation speed of the winding shaft 36 with the rotating means 38.

When the thin plate-shaped seed single crystal 32 is immersed in the center of the melt 18, crystallization begins immediately, and the immersed portion of the thin plate-shaped seed single crystal 32 thickens, but it was confirmed that if left in this state, the thickened portion melts and becomes thinner.

In this state, the thin plate-shaped seed single crystal 32 was pulled upward, and the thickness of the produced thin plate-shaped single crystal 40 was checked with a camera. The pulling speed and the irradiation intensity of the laser light 16a were adjusted to control the thickness to 0.3 mm, and the winding shaft 36 was rotated, and the thin plate-shaped single crystal 40 was continuously wound around the winding shaft 36.

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

As the thin plate single crystal 40 is pulled up, the liquid surface position of the melt 18 in the raw material lump 12 drops, so the position of the mounting table 82 on which the raw material lump 12 is placed is controlled to a predetermined position via the position control means 84 so that the liquid surface position of the melt 18 in the raw material lump 12 is always kept at the same position as the original position.

The thin plate single crystal 40 thus produced, which was over 10 m long, had a thickness of 0.3 mm, and a width of 383 to 386 mm, was examined using secondary ion mass spectrometry (SIMS) and found to have an optimal, homogeneous concentration of the additive phosphorus, and to be of high quality, confirming the superiority of the thin plate single crystal manufacturing apparatus 10 and thin plate single crystal manufacturing method of the present invention.

Next, a summary of the above-mentioned thin plate single crystal manufacturing apparatus 10 of the present invention and the thin plate single crystal manufacturing method using this thin plate single crystal manufacturing apparatus 10 will be described.
The biggest factor that enables the thin plate-shaped single crystal manufacturing apparatus 10 and thin plate-shaped single crystal manufacturing method of the present invention to continuously and stably produce thin plate-shaped single crystals 40 is that the melting of the raw material lump 12 and the single crystallization from the resulting melt 18 can each be largely controlled independently.

That is, heating is necessary to melt the raw material lump 12 and obtain the melt 18, but cooling is necessary to solidify and crystallize the melt 18, and the two are contradictory.
Therefore, in the present invention, the laser light 16a is not directly irradiated onto the portion where crystallization is to occur (the center of the melt 18), but rather onto the portion other than the portion where crystallization is to occur (the peripheral region excluding the center of the melt 18), thereby melting the upper surface 14 of the raw material lump 12 and conducting the heat of the melt 18 to the portion where crystallization is to occur (the center of the melt 18), thereby forming the melt 18 also in the center of the upper surface 14.

As a result, the temperature of the portion where crystallization is taking place (the center of the melt 18) becomes lower than the temperature of the portion that is melted by irradiation with the laser light 16a (the peripheral region of the melt 18 excluding the center), making crystallization easier.

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 underside 34 of the immersed thin plate-shaped seed single crystal 32, lowering the temperature of the melt in contact with the underside 34 and causing crystallization to proceed rapidly. If left for a while, the amount of heat escaping through the thin plate-shaped seed single crystal 32 reaches a steady state, and the parts that had solidified rapidly up until that point gradually melt due to the heat from the surrounding melt 18, and return to 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 a low temperature area, so that crystallization proceeds on the lower surface 34 in contact with the melt 18 .
When the pulling speed of the thin plate-shaped seed single crystal 32 is increased and the crystallization cannot keep up with the speed, the thickness of the thin plate-shaped single crystal 40 produced becomes thin, whereas when the pulling speed is slowed, the crystallization proceeds and the thickness of the thin plate-shaped single crystal 40 increases.

Therefore, by controlling the temperature of the melt 18 to a low temperature, crystallization becomes easier and the thickness of the thin plate-shaped single crystal 40 increases, so that thin plate-shaped single crystal 40 of a desired thickness can be continuously produced even if the pulling speed is increased.

Increasing the pulling speed can improve the manufacturing efficiency of the thin plate-shaped single crystal 40, but if it is made too fast, the possibility of cell growth increases. If cell growth occurs, the concentration of the additive phosphorus will fluctuate significantly locally, degrading the properties of the single crystal. Therefore, it is important to continuously manufacture the thin plate-shaped single crystal 40 by accelerating the pulling speed as much as possible while suppressing the occurrence of cell growth.

Furthermore, the present invention has made it possible for the first time to produce high-quality thin plate single crystals 40 with homogeneous composition from so-called incongruent melting substances, such as decomposed melting substances and solid solution single crystals. It has been thought impossible to produce such thin plate single crystals 40 with homogeneous composition from incongruent melting substances using conventional methods.

In other words, in order to produce homogeneous single crystals of these incompatible molten substances using the so-called melting method, in which the raw materials are melted to form a melt and then solidified to produce single crystals, there is no other method in principle than to produce a raw material lump 12 of the target composition, and then use a solvent with a solvent composition that coexists in equilibrium with the target composition to simultaneously dissolve the raw material lump 12 and precipitate single crystals from the solvent, known as the solvent transfer method.

In this patent, the required amount of solvent phase components is placed on the upper surface 14 of the raw material lump 12, and then infrared rays 16 are irradiated to melt the lump and form a solvent solution. The production of single crystals from the solvent and the dissolution of the raw material lump 12 into the solvent are simultaneously carried out, applying the solvent transfer method and making it possible to produce a thin plate-shaped single crystal 40 with a homogenous composition.

The thin plate single crystal manufacturing apparatus 10 of the present invention and the thin plate single crystal manufacturing method using this thin plate single crystal manufacturing apparatus 10 have been described above, but the present invention is not limited to the above embodiment.

For example, in the above-mentioned thin plate single crystal manufacturing apparatus 10, the first to third embodiments have been described separately, but these may be combined to form the thin plate single crystal manufacturing apparatus 10 of the present invention. In other words, for example, the thin plate single crystal manufacturing apparatus 10 may be formed by combining the first embodiment with the second and third embodiments.

Furthermore, in the above-mentioned thin plate single crystal manufacturing apparatus 10, the infrared irradiation means 20 is provided so as to irradiate parallel to each side of the rectangular shape, but this is not limited thereto, and only one infrared irradiation means 20 may be provided.

In addition, as long as the laser light 16a can be irradiated so as to form a horizontally elongated hollow rectangular irradiation area that matches the peripheral area excluding the center of the upper surface 14 of the raw material lump 12, this elongated hollow rectangular irradiation area may be formed by multiple laser lights 16a, and the number and cross-sectional shape of the laser light 16a irradiated from one infrared irradiation means 20 are not limited.

That is, laser beams 16a with a U-shaped cross section can be irradiated onto the upper surface 14 of the raw material block 12 from the left and right, and the two laser beams 16a, 16a with a U-shaped cross section can form an irradiation area with a horizontally elongated hollow rectangular cross section, or four laser beams with rod-shaped cross sections can form an irradiation area with a horizontally elongated hollow rectangular cross section.

Furthermore, the thickness of the thin plate-like single crystal 40 to be manufactured has been described as being approximately 100 μm to 3000 μm, but in principle it is possible to manufacture it with a thickness greater than this, for example 5000 μm or more, and the thickness is not limited to the above range.

The thickness of the thin plate-shaped seed single crystal 32 that is immersed in the melt 18 has been described as, for example, about 300 μm to 500 μm, but in principle it is possible to produce a thin plate-shaped single crystal 40 with a thickness outside this range, and the thickness is not limited to the above range.

In this way, the thin plate single crystal manufacturing apparatus 10 and the thin plate single crystal manufacturing method of the present invention can be modified in various ways without departing from the purpose of the present invention.

10 Thin plate single crystal manufacturing apparatus 12 Raw material block for manufacturing thin plate single crystal (raw material block)
Reference Signs List 14 Upper surface 16 Infrared rays 16a Laser light 18 Melt 20 Infrared irradiation means 22 Window 24 Reflecting mirror 30 Lifting means 32 Thin plate-shaped seed single crystal 34 Lower surface 36 Winding shaft 38 Rotating means 40 Thin plate-shaped single crystal 42 Cover member 50 Winding means 52 Thin 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 Inlet pipe 94 Exhaust pipe

Claims (22)

an infrared ray irradiating means for irradiating an upper surface of the raw material lump for producing a thin plate-shaped single crystal with infrared rays to melt the surface of the upper surface;
a lifting means for immersing a lower surface of the thin plate-shaped seed single crystal in the melt obtained on the upper surface of the thin plate-shaped seed single crystal by the infrared irradiation means and lifting the thin plate-shaped seed single crystal upward from the immersed state;
Equipped with
the lower side of the thin plate-shaped seed single crystal is immersed in the melt obtained on the upper surface of the raw material lump for producing the thin plate-shaped single crystal by the infrared irradiation means via the lifting means, so that the growth of a single crystal is started from the lower side of the immersed thin plate-shaped seed single crystal, and the thin plate-shaped seed single crystal is further pulled upward via the lifting means, so that the thin plate-shaped single crystal is continuously produced;
The upper surface of the raw material block for producing a thin plate-shaped single crystal is
An apparatus for producing a thin plate-shaped single crystal, characterized in that a required amount of a liquid phase composition which coexists in equilibrium with the composition of the thin plate-shaped single crystal to be produced is initially placed in the apparatus. The thin plate single crystal manufacturing apparatus according to claim 1, characterized in that the infrared light irradiated from the infrared light irradiating means is laser light. The shape of the irradiation area of the laser light is a hollow rectangle that is elongated in the horizontal direction,
The thin plate single crystal manufacturing apparatus according to claim 2, characterized in that laser light is irradiated to the peripheral region excluding the center of the upper side of the raw material block for manufacturing the thin plate single crystal so as to form the hollow rectangular irradiation area. The lifting means is
a winding means for continuously winding up the produced thin plate-like single crystal into a roll,
The winding means is
a winding shaft for continuously winding the thin plate-like single crystal;
A rotating means for rotating the winding shaft;
Equipped with
4. The thin plate single crystal manufacturing apparatus according to claim 1, wherein the thin plate seed single crystal is suspended from the winding shaft. The thin plate-like seed single crystal is
5. The apparatus for producing a thin plate-shaped single crystal according to claim 4, wherein the crystal is suspended from the winding shaft via a plurality of thin wires. In the thin plate-shaped seed single crystal,
The thickness of the portion to which the thin wire is attached is
6. The apparatus for producing a thin plate-shaped single crystal according to claim 5, wherein the size of the thin plate-shaped single crystal is equal to or smaller than the thickness of the thin plate-shaped single crystal to be produced. Between the lifting means and the raw material block for producing a thin plate-shaped single crystal,
7. The apparatus for producing thin plate-shaped single crystals according to claim 1, further comprising an anti-vibration member for preventing the thin plate-shaped single crystals from vibrating as they are continuously produced. Between the lifting means and the raw material block for producing a thin plate-shaped single crystal,
The thin plate single crystal manufacturing apparatus according to any one of claims 1 to 7 , further comprising a shielding member for blocking radiant heat emitted from the melt so that the radiant heat does not reach the thin plate single crystal being continuously manufactured. 9. The apparatus for producing a thin plate-shaped single crystal according to claim 1 , wherein the raw material block for producing the thin plate-shaped single crystal is substantially rectangular. a mounting table for mounting the raw material block for producing the thin plate-shaped single crystal;
a position control means for controlling the position of the mounting table so that the position of the mounting table is at a predetermined position;
The thin plate single crystal manufacturing apparatus according to any one of claims 1 to 9 , further comprising: The lifting means is
The thin plate-shaped single crystal manufacturing apparatus according to any one of claims 1 to 10, characterized in that the lower surface of the thin plate-shaped seed single crystal is immersed in the center of the molten liquid on the upper surface of the raw material lump for manufacturing the thin plate-shaped single crystal melted by the infrared irradiation means. The raw material block for producing the thin plate-shaped single crystal is surrounded by:
12. The apparatus for producing a thin plate single crystal according to claim 1 , further comprising a preheating means for preheating the raw material lump for producing the thin plate single crystal. At least the raw material block for producing the thin plate-shaped single crystal is disposed in a chamber,
13. The apparatus for producing a thin plate-shaped single crystal according to claim 1, wherein the lifting means is disposed at an upper portion of the chamber. 14. The thin plate single crystal manufacturing apparatus according to claim 13 , further comprising a gas introduction device for filling the chamber with an atmospheric gas containing an additive. The lifting means is
15. The apparatus for producing a thin plate single crystal according to claim 1, wherein a plurality of the apparatuses are provided above the raw material block for producing the thin plate single crystal. 16. The apparatus for producing a thin plate-shaped single crystal according to claim 1, wherein the thickness of the thin plate-shaped seed single crystal is within a range of 300 μm to 500 μm. a melting step of irradiating an upper side surface of the raw material lump for producing a thin plate-shaped single crystal with infrared rays via an infrared ray irradiation means to melt the surface of the upper side surface of the raw material lump for producing a thin plate-shaped single crystal;
a growing step of immersing a lower surface of the thin plate-shaped seed single crystal in the melt obtained on the upper surface of the raw material lump for producing the thin plate-shaped single crystal by using an elevating means, and starting the growth of the single crystal from the lower surface of the thin plate-shaped seed single crystal;
a continuous production step of pulling the thin plate-shaped seed single crystal upward after the single crystal growth has started in the growth step, and continuously producing the thin plate-shaped single crystal;
and
In the melting step,
When the thin plate-shaped single crystal to be produced is a decomposed melt substance, a required amount of a liquid phase composition that coexists in equilibrium with the composition of the decomposed melt substance is initially placed on the upper side of the raw material block for producing the thin plate-shaped single crystal. a melting step of irradiating an upper side surface of the raw material lump for producing a thin plate-shaped single crystal with infrared rays via an infrared ray irradiation means to melt the surface of the upper side surface of the raw material lump for producing a thin plate-shaped single crystal;
a growing step of immersing a lower surface of the thin plate-shaped seed single crystal in the melt obtained on the upper surface of the raw material lump for producing the thin plate-shaped single crystal by using an elevating means, and starting the growth of the single crystal from the lower surface of the thin plate-shaped seed single crystal;
a continuous production step of pulling the thin plate-shaped seed single crystal upward after the single crystal growth has started in the growth step, and continuously producing the thin plate-shaped single crystal;
and
In the melting step,
When the thin plate-shaped single crystal to be produced is a solid solution material containing additives, a required amount of a liquid phase composition that coexists in equilibrium with the composition is first placed on the upper surface of the raw material block for producing the thin plate-shaped single crystal. In the melting step,
19. The method for producing a thin plate-shaped single crystal according to claim 17 or 18 , wherein the infrared rays irradiated from the infrared ray irradiating means are laser light. In the melting step,
The shape of the irradiation area of the laser light is a hollow rectangle that is elongated in the horizontal direction,
The method for producing a thin plate-shaped single crystal according to claim 19 , characterized in that laser light is irradiated to the peripheral region excluding the center of the upper side of the raw material lump for producing the thin plate-shaped single crystal so as to form the hollow rectangular irradiation area. After the continuous manufacturing process,
a winding step of winding the continuously produced thin plate-like single crystal into a roll;
The method for producing a thin plate-shaped single crystal according to any one of claims 17 to 20, further comprising: In the growing step,
A method for producing a thin plate-shaped single crystal according to any one of claims 17 to 21, characterized in that the lower surface of the thin plate-shaped seed single crystal is immersed in the center of the molten liquid on the surface of the upper surface of the molten raw material lump for producing the thin plate-shaped single crystal.

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