Thin plate single crystal manufacturing apparatus and thin plate single crystal manufacturing method

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

Technical Field

[0001] The present invention relates to a thin-plate single-crystal manufacturing apparatus and a thin-plate single-crystal manufacturing method capable of continuously manufacturing thin-plate single-crystals having a thickness of about several hundred μm.

Background Art

[0002] In recent years, there has been a call for the conversion from fossil fuels to renewable energy, and the conversion from a power generation method that consumes oil to a power generation method using solar cells that utilize sunlight has been progressing on a global scale. However, the power generation cost of solar power generation is still high compared to other power generation methods, and the development of highly efficient and inexpensive solar cells is desired.

[0003] As substrate materials constituting solar cells, various materials such as semiconductor silicon crystals, amorphous silicon, and compound semiconductor crystals are known, and development is being advanced for each of them. Among them, semiconductor silicon crystals are the main substrate materials. The general-purpose size of the substrate is about 155 mm square and 0.3 mm thick. A product obtained by subjecting a silicon crystal substrate of this general-purpose size to a process enabling highly efficient solar power generation and attaching electrodes for extracting the generated power is called a "cell", and a product in which a large number of these cells are arranged in a planar shape is called a "module". This module is installed according to the use environment and used as a solar power generation device.

[0004] To reduce the power generation cost of solar cells, it is important to improve the performance of the substrate made of semiconductor silicon crystal, which is a main component of the cell, and to develop a new manufacturing method capable of reducing the manufacturing cost of the substrate material compared to the current situation.

[0005] By the way, as a structure of a solar cell capable of achieving high-efficiency power generation, there is a method called the HIT (Heterojunction with Intrinsic Thin-layer) type in which an N-type silicon single-crystal plate doped with phosphorus is sandwiched from both sides by amorphous silicon layers to expand the wavelength range of available sunlight. with Intrinsic Thin-layer) type.

[0006] The method called the HIT type is adopted, and a combined back-contact type method in which all the electrodes for extracting the generated electricity are collected on the back side and the electrodes are excluded from the front side is said to achieve the highest efficiency. In the N-type single-crystalline silicon substrate used here, phosphorus must be added homogeneously in an optimal composition.

[0007] There are two methods for manufacturing the current main general-purpose silicon crystal substrates for solar cells. The first method is the directional solidification method in which the raw materials are melted in a large quartz crucible and solidified from the bottom upward, and the obtained large crystal ingot is cut into general-purpose sizes to manufacture the crystal substrate.

[0008] However, the crystal ingot manufactured by this method is a P-type polycrystal doped with boron, and in principle, it is impossible to manufacture the N-type single-crystalline substrate required for the above-mentioned highly efficient solar cells by this directional solidification method.

[0009] The second method is to melt the raw materials in a quartz crucible, immerse a seed single crystal in the obtained melt, pull it upward while thickening it, manufacture a round bar-shaped single crystal by the so-called pulling method, and cut the manufactured round bar-shaped single crystal to manufacture a general-purpose size single-crystalline substrate.

[0010] This pulling method has two major problems. The first problem is that the manufacturing cost becomes high. The manufacturing cost of the single-crystalline rod obtained by the pulling method increases as the diameter of the single-crystalline rod increases. To obtain a general-purpose size substrate, a single-crystalline rod with a diameter of about 250 mm is required, but in order to reduce the manufacturing cost, a single-crystalline rod with a diameter of about 200 mm is used to manufacture a general-purpose size substrate. Therefore, the shape has notches at the four corners of the square, and of course, the efficiency is lower than that of a product with an accurate square shape.

[0011] The second problem with the Czochralski method is that it is impossible to homogenize the phosphorus content added to make it N-type. The phosphorus concentration in the melt obtained by adding phosphorus to raw silicon and melting it is uniform, but the phosphorus concentration in the part that first solidifies as a single crystal is lower than the phosphorus concentration in the melt. This phenomenon is called the "segregation phenomenon," and the ratio of the phosphorus concentration in the melt to the phosphorus concentration in the solidified product is called the "segregation coefficient."

[0012] In the case of silicon, since the segregation coefficient of phosphorus is about 0.35, the phosphorus concentration in the part that first solidifies is low, and the difference remains in the melt. Therefore, as solidification progresses, the phosphorus concentration in the melt becomes higher, and accordingly, the phosphorus concentration in the solidified product also becomes higher according to the segregation coefficient. Therefore, the optimal composition part is limited to a part of the obtained single crystal.

[0013] Moreover, when about half of the raw material melted in the crucible has solidified, the phosphorus concentration becomes too high and cannot be used for solar cells. Therefore, the manufacturing operation of the single crystal is stopped, the atmosphere in the manufacturing furnace is maintained in an inert gas atmosphere, the product is taken out while maintaining the raw material melt temperature, new granular raw material is replenished to the remaining raw material melt to return to the original raw material melt composition, and a manufacturing method is adopted in which the production of the second single crystal is restarted.

[0014] In this manufacturing method, the quartz crucible that holds the raw material melt is consumed, so the number of repeated uses is limited to 2 times, or at most 3 times even if a specially prepared high-quality quartz crucible is used.

[0015] What is most problematic with this manufacturing method is that the phosphorus concentration in the product cannot be made uniform. High efficiency can be achieved by manufacturing solar cell wafers only from the optimal composition products, but since the yield of the optimal composition products is low, the price becomes high, which directly leads to an increase in the power generation cost.

[0016] Therefore, if products with a phosphorus concentration that is too low or too high compared to the optimal composition products are used to reduce costs, 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 also been vigorously carried out. Of course, it is highly likely that manufacturing thin single crystals with a predetermined thickness from the beginning and then cutting them into a predetermined size can reduce cutting losses and production costs compared to cutting large crystal blocks to produce thin single crystals.

[0017] There are three types of methods for manufacturing silicon thin plate crystals reported so far. The first method is a method called the EFG (Edge defined Film-fed Growth) method, in which a jig called a die with a slit 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 upward by surface tension from the slit of the die and solidified while being pulled upward to manufacture a thin plate-shaped single crystal.

[0018] Although this manufacturing method has been vigorously developed mainly in the United States, it has not yet been put into practical use for manufacturing silicon substrates for solar cells. The reasons include that no material for the jig that can stably withstand long-term use has been found, it is difficult to control the temperature during the solidification of the raw material melt, and it is difficult to increase the size.

[0019] The second method is a method named the ESR (Edge Stabilized Ribbon) method, which uses a string instead of the above-mentioned die. In this ESR method, first, the string is immersed in the surface of the raw material melt and attached horizontally, and when it is lifted slightly upward, the raw material melt that is lifted along with the string by surface tension solidifies into a thin plate-shaped crystal.

[0020] When strings are connected to both sides of the string and they are pulled upward together, the solidified thin plate-shaped crystal also grows upward while being pulled upward together. However, in this method, the part that is first lifted by the string and solidified is "polycrystalline", and the thin plate that grows accordingly is also "polycrystalline" and does not become "single crystal".

[0021] The third method is a method named the Dendritic web growth method. Dendrites (dendritic crystals) have the property of preferentially growing in the direction of high thermal conductivity when the growth rate reaches a certain rate. This method is a method for producing thin plate-like crystals by utilizing this property of dendrites (dendritic crystals).

[0022] This method does not use jigs or strings like the EFG method or the ESR method, and it is said that single crystals can be grown if growth is optimally controlled. However, in reality, single crystals cannot be produced unless the first dendrite (dendritic crystal) is made single, so there are no examples of continuously growing large and long thin plate-like single crystals by this method, and it has not reached industrial production.

[0023] 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 silicon melt in a quartz crucible. When the raw material silicon is melted in a quartz crucible as in these production methods, as shown in Equation 1, silicon melt and quartz react to generate silicon monoxide (SiO).

[0024]

Equation

[0025] The silicon monoxide (SiO) generated by the reaction is mixed as a solid solution into the silicon crystal, which is the product, and becomes a major factor in the performance degradation of the single crystal. Therefore, a production method that does not require the use of a quartz crucible is desirable for producing high-quality single crystals.

[0026] Currently, as a method for producing silicon single crystals without using a crucible, the high-frequency floating zone melting method, which melts and solidifies a raw material rod using high-frequency induction heating to produce a single crystal, has been put into practical use (for example, Patent Document 1). By this high-frequency floating zone melting method, a high-purity single crystal containing no silicon monoxide (SiO) can be obtained.

[0027] However, the raw material rods that can be used in the high-frequency floating zone melting method are specially prepared high-density products. Such raw material rods are expensive and have a limited supply, and are not suitable for solar cells that are expected to have low costs. Furthermore, in this high-frequency floating zone melting method, it is extremely difficult to manufacture thin plate single crystals, and there are no reports of successful production.

[0028] As another method of manufacturing high-purity single crystals without using a crucible, a method using infrared rays is known. As a method of manufacturing single crystals using infrared rays, there is known an infrared floating zone melting method in which raw material powder is processed into a rod shape, locally heated to be melted and solidified to produce a single crystal rod.

[0029] 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 melting and solidification of the raw material are continued. In addition, in this infrared floating zone melting method, conventionally, a method of irradiating infrared rays from the horizontal direction has been adopted. However, in this irradiation method from the horizontal direction, it is impossible in principle to manufacture a single crystal with a large diameter.

[0030] Therefore, an upper surface melting method has been developed in which infrared rays are irradiated onto the upper surface of a large-diameter seed single crystal arranged at the bottom to melt it, and a raw material melt obtained by melting the raw material is dropped here to enable the production of a large-diameter single crystal. With this upper surface melting method, there is no longer a principle limit to the diameter of the single crystal that can be manufactured, so its scope of application has expanded dramatically.

[0031] On the other hand, as current industrial single crystal materials, in addition to the materials for solar cells described above, many oxide materials such as lithium niobate and lithium tantalate which are ferroelectric materials, lutetium silicate and gadolinium silicate which are phosphor materials, yttrium aluminum garnet and gadolinium gallium garnet which are laser materials are used.

[0032] These oxide materials are used in the manufacture of various devices by producing round bar-shaped single crystals by the Czochralski method and cutting them into thin plate-shaped single crystals with a thickness of about 0.3 mm. However, in the Czochralski method, contamination from the crucible material into the product cannot be avoided, and moreover, due to the aforementioned segregation phenomenon, the concentration of useful additives in the product cannot be homogenized in principle. For this reason, it is inconvenient for the manufacture of high-quality devices.

[0033] Therefore, it is possible to manufacture high-performance products at much lower cost by manufacturing and using thin plate-shaped single crystals with a predetermined thickness and an optimal composition from the beginning, rather than manufacturing round bar-shaped single crystals and then cutting them into thin plate-shaped single crystals for use.

Prior Art Documents

Patent Documents

[0034]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0035] However, the research and development results in the conventional thin plate-shaped single crystal manufacturing methods so far are not sufficient, and examples of manufacturing thin plate-shaped single crystals for industrial use are only known to the extent of manufacturing sapphire single crystal plates and gallium oxide single crystal plates by the EFG method.

[0036] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a thin plate-shaped single crystal manufacturing apparatus and a thin plate-shaped single crystal manufacturing method capable of manufacturing a thin plate-shaped single crystal with an optimal composition and uniform additive concentration, a thickness of about several hundred μm, at low cost and continuously with high precision.

Means for Solving the Problems

[0037] The present invention has been invented to solve the problems in the above-described prior art, The thin plate-shaped single crystal manufacturing apparatus of the present invention, An infrared irradiation means for irradiating the upper surface of a raw material mass for producing a thin plate single crystal (hereinafter also referred to as a raw material mass) with infrared rays to melt the surface of the upper surface, a lifting means for dipping the lower surface of a thin plate seed single crystal into the melt obtained on the surface of the upper surface melted by the infrared irradiation means and pulling up the thin plate seed single crystal upward from the dipped state, is provided, By dipping the lower surface of the thin plate seed single crystal into the melt obtained on the surface of the upper surface of the raw material mass for producing a thin plate single crystal by the infrared irradiation means via the lifting means, crystal growth of the single crystal is started from the lower surface of the dipped thin plate seed single crystal, and further, by pulling up the thin plate seed single crystal upward via the lifting means, it is configured to continuously produce a thin plate single crystal. It is characterized by that.

[0038] With such a configuration, the number of members constituting the apparatus is small, the additive concentration is homogeneous with an optimal composition, and a thin plate single crystal having a thickness of about several hundred μm can be manufactured at low cost and continuously with high precision. Furthermore, a homogeneous composition thin plate single crystal of a so-called incongruent melting substance such as a decomposition melting substance or a solid solution substance can be manufactured with high precision.

[0039] Further, the thin plate single crystal manufacturing apparatus of the present invention, is characterized in that the infrared rays irradiated from the infrared irradiation means are laser light. If it is laser light in this way, a predetermined range of the raw material mass can be accurately heated, so that the melt does not spill from the upper surface of the raw material mass, and the melt (melt pool) can be surely formed continuously.

[0040] Further, the thin plate single crystal manufacturing apparatus of the present invention, the shape of the irradiation region of the laser light is a horizontally elongated hollow square shape, and the laser light is irradiated so as to form the hollow square-shaped irradiation region on the peripheral region excluding the central portion of the upper surface of the raw material mass for producing the thin plate single crystal.

[0041] If the laser light is irradiated so as to match the peripheral region of the upper surface of the raw material block excluding the central portion, excluding the central portion of the upper surface of the raw material block, the peripheral region is melted first, and the central portion not irradiated with the laser light is melted by heat conduction from the melt of the previously melted peripheral region.

[0042] 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 the hollow rectangular irradiation region of the laser light, for example, linear laser light may be irradiated from four directions.

[0043] Furthermore, the laser light may be irradiated from an obliquely upward direction or vertically from directly above with respect to the upper surface of the raw material block, but it is preferable that the irradiation angle can be adjusted to an optimum angle according to the heat conduction characteristics of the single crystal material and the thickness of the thin plate-like single crystal to be manufactured. By the way, in order to melt the raw material block and continuously manufacture a thin plate-like single crystal, it is necessary to continuously carry out the melting of the raw material block and the solidification as a thin plate-like single crystal simultaneously. However, heating is required for melting the raw material block, and cooling of the melt is required for solidifying the thin plate-like single crystal.

[0044] Therefore, in order to enable stable production of the thin plate-like single crystal, it is essential to continuously carry out the opposite actions of "heating" and "cooling" stably with good controllability. By irradiating the raw material block with the above-described hollow rectangular laser light, this can be realized. That is, by giving such a temperature distribution to the melt pool on the upper surface of the raw material block, the growth of the thin plate-like single crystal can be stably and continuously carried out from this central portion.

[0045] In addition, the thin plate-like single crystal manufacturing apparatus of the present invention The elevating means is a winding means for continuously winding the manufactured thin plate-like single crystal into a roll shape, The winding means is a winding shaft for continuously winding the thin plate-like single crystal, rotating means for rotating the winding shaft, comprising, characterized in that the thin plate-shaped seed single crystal is configured to be suspended from the winding shaft.

[0046] If the winding means is configured in this way, the continuously manufactured thin plate-shaped single crystal can be surely wound around the winding shaft, and the apparatus is not enlarged more than necessary. Further, since the manufactured thin plate-shaped single crystal is in a roll shape, it can be easily transported at the time of shipment, and the handleability can be improved.

[0047] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention, wherein the thin plate-shaped seed single crystal, is characterized in that it is suspended from the winding shaft via a plurality of thin wires. If the thin plate-shaped seed single crystal is suspended with heat-resistant and high-strength thin wires in this way, the continuously manufactured thin plate-shaped single crystal can be surely wound around the winding shaft.

[0048] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention, in the thin plate-shaped seed single crystal, the thickness of the portion where the thin wire is attached is, preferably not more than the thickness of the thin plate-shaped single crystal to be manufactured.

[0049] In this way, in the thin plate-shaped seed single crystal, if the thickness of the portion where the thin wire is attached is set to be not more than the thickness of the thin plate-shaped single crystal to be manufactured, when the thin plate-shaped single crystal is wound around the winding shaft, it is possible to surely prevent the surface of the thin plate-shaped single crystal from coming into contact with the thin wire and being damaged.

[0050] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention, on the upper surface of the raw material mass for manufacturing the thin plate-shaped single crystal, a necessary amount of a composition of a liquid phase that coexists in equilibrium with the composition of the thin plate-shaped single crystal to be manufactured is initially arranged.

[0051] Thus, if a necessary amount of the composition of the liquid phase that is in equilibrium coexistence with the composition of the thin plate-like single crystal to be produced is arranged on the upper surface of the raw material mass from the beginning, a homogeneous and optimally composed thin plate-like single crystal can be continuously produced.

[0052] Further, the thin plate-like single crystal manufacturing apparatus of the present invention Between the lifting means and the raw material mass for manufacturing the thin plate-like single crystal, A shaking prevention member for preventing the shaking of the continuously manufactured thin plate-like single crystal is disposed, which is characterized in that.

[0053] If the shaking prevention member is disposed in this way, it is possible to suppress the over-shaking of the manufactured thin plate-like single crystal to the left and right. Therefore, the growth position can be kept within a predetermined range without deviation, and high-quality thin plate-like single crystals can be continuously and stably manufactured.

[0054] Further, the thin plate-like single crystal manufacturing apparatus of the present invention Between the lifting means and the raw material mass for manufacturing the thin plate-like single crystal, It is preferable that a shielding member is provided to shield the radiant heat emitted from the melt so that it is difficult for the radiant heat to reach the continuously manufactured thin plate-like single crystal.

[0055] The thin plate-like single crystal solidifies while being pulled up from the melt. However, if the radiant heat emitted from the melt reaches the manufactured thin plate-like single crystal, it becomes difficult to increase the manufacturing speed of the thin plate-like single crystal. Therefore, by providing the shielding member, it becomes difficult for the radiant heat of the melt to reach the manufactured thin plate-like single crystal, and the manufacturing efficiency of the thin plate-like single crystal can be increased.

[0056] Further, the thin plate-like single crystal manufacturing apparatus of the present invention The raw material mass for manufacturing the thin plate-like single crystal is characterized in that it is substantially a rectangular parallelepiped. With such a shape, a melt (melt pool) can be continuously provided on the surface of the upper surface of the raw material mass by irradiating infrared rays.

[0057] Further, the thin plate-like single crystal manufacturing apparatus of the present invention The size of the upper surface of the raw material mass for manufacturing the thin plate single crystal is set to be several millimeters or more larger than the size of the lower surface of the thin plate seed single crystal in both the thickness direction and the lateral direction.

[0058] If the sizes of the raw material mass and the thin plate seed single crystal are set in this way, the entire lower surface of the thin plate seed single crystal can be immersed in the melt, and a thin plate single crystal of a desired size can be continuously manufactured.

[0059] Further, the thin plate single crystal manufacturing apparatus of the present invention includes a mounting table for mounting the raw material mass for manufacturing the thin plate single crystal, and position control means for controlling the position of the mounting table to a predetermined position. It is characterized by comprising the above.

[0060] If the position of the mounting table (particularly the vertical position) can be controlled in this way, even if the liquid level position of the melt of the raw material mass drops as the thin plate single crystal is pulled up, the position of the raw material mass can be raised to maintain the initial position, and the liquid level position can always be controlled to the same position. Therefore, it is only necessary to always fix the infrared irradiation position to the same position, and the thin plate single crystal can be continuously manufactured stably and with good yield. When the parallel laser beam is irradiated from the perpendicular direction to the upper surface of the raw material mass, since the irradiation intensity of the laser beam does not change even if the liquid level position of the melt of the raw material mass drops, it is not necessary to perform position control to keep the liquid level position of the melt of the raw material mass constant.

[0061] Further, the thin plate single crystal manufacturing apparatus of the present invention wherein the elevating means is configured to immerse the lower surface of the thin plate seed single crystal in the central portion of the melt on the upper surface of the raw material mass for manufacturing the thin plate single crystal melted by the infrared irradiation means.

[0062] The central part of the melt is a part where the melt continuously accumulates. If the lower surface of the thin plate-shaped seed single crystal is immersed in this central part, the thin plate-shaped single crystal can be continuously manufactured by pulling up the thin plate-shaped seed single crystal upward by the lifting means.

[0063] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention Around the raw material mass for manufacturing the thin plate-shaped single crystal, There is provided preheating means for preheating the raw material mass for manufacturing the thin plate-shaped single crystal, which is characterized in that.

[0064] If the raw material mass is preheated to near the melting point in this way, it becomes possible to reduce the amount of infrared rays irradiated 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, the thin plate-shaped single crystal can be continuously manufactured stably and with high precision.

[0065] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention At least the raw material mass for manufacturing the thin plate-shaped single crystal is disposed in the chamber, It is preferable that the lifting means is disposed above the chamber. If the raw material mass is disposed in the chamber in this way, the thin plate-shaped single crystal can be manufactured in an atmosphere suitable for the single crystal material.

[0066] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention It is characterized by comprising a gas introduction device for filling the inside of the chamber with an atmosphere gas containing an additive.

[0067] If the gas introduction device is provided in this way, the inside of the chamber can be made into an atmosphere suitable for the characteristics of the material of the thin plate-shaped single crystal to be manufactured, and thereby a high-quality thin plate-shaped single crystal with an optimal composition and uniform additive concentration can be manufactured.

[0068] Further, the thin plate-shaped single crystal manufacturing apparatus of the present invention The lifting means It is characterized in that a plurality of them are provided on the upper part of the raw material mass for producing the thin plate single crystal.

[0069] If configured in this way, for example, by arranging and immersing a plurality of thin plate seed single crystals in one melt pool and pulling them up to the upper part by respective lifting means, the manufacturing efficiency of the thin plate single crystal can be remarkably improved compared with the case where there is one lifting means.

[0070] Further, the thin plate single crystal manufacturing apparatus of the present invention It is preferable that the thickness of the thin plate seed single crystal is within the range of 300 μm to 500 μm. With such a thickness, a high-purity thin plate single crystal can be continuously manufactured and elongated by winding it up.

[0071] Further, the thin plate single crystal manufacturing apparatus of the present invention It is preferable that the thickness of the thin plate single crystal is within the range of 100 μm to 3000 μm. The thickness of the manufactured thin plate single crystal can be manufactured within the range of 100 μm to 3000 μm, but when assuming winding by winding means, it is preferably within the range of 100 μm to 500 μm. However, by adjusting the melt temperature and the pulling speed, it can also be adjusted to be thinner than 100 μm or thicker than 500 μm.

[0072] However, in the case of a thin plate single crystal thicker than 500 μm, the diameter when winding the thin plate single crystal around the winding shaft of the winding means becomes large. In this case, it is also possible to pull it up upward without winding and commercialize it. In particular, when manufacturing a silicon thin plate single crystal for a solar cell, the thickness of the thin plate single crystal is preferably within the range of 200 μm to 400 μm.

[0073] Further, the thin plate single crystal manufacturing method of the present invention A melting step of irradiating infrared rays to the upper surface of the raw material mass for producing the thin plate single crystal through infrared ray irradiation means and melting the surface of the upper surface of the raw material mass for producing the thin plate single crystal, In the melting step, the lower surface of the thin-plate seed single crystal is immersed in the melt obtained on the upper surface of the raw material mass for producing the thin-plate single crystal through an elevating means, and a growth step of starting the growth of the single crystal from the lower surface of the thin-plate seed single crystal is carried out. In the growth step, the thin-plate seed single crystal in which the growth of the single crystal has started is pulled upward, and a continuous production step of continuously producing a thin-plate single crystal is carried out. It is characterized by having at least the above. With such a manufacturing method, a thin-plate single crystal having an optimum composition and a homogeneous additive concentration and a thickness of about several hundred μm can be manufactured continuously with high precision at low cost.

[0074] Further, the method for manufacturing a thin-plate single crystal of the present invention In the melting step, The infrared ray irradiated from the infrared ray irradiation means is characterized by being a laser beam.

[0075] If it is a laser beam in this way, a predetermined range of the raw material mass can be accurately heated in a required shape. Therefore, the melt does not spill from the upper surface of the raw material mass, and the melt pool can be continuously and surely formed.

[0076] Further, the method for manufacturing a thin-plate single crystal of the present invention In the melting step, The shape of the irradiation region of the laser beam is a horizontally elongated hollow square shape, The laser beam is irradiated so as to form the hollow square-shaped irradiation region on the peripheral region excluding the central portion of the upper surface of the raw material mass for producing the thin-plate single crystal.

[0077] If the laser beam is irradiated so as to form a hollow square-shaped irradiation region in this way, the peripheral region excluding the central portion of the upper surface of the raw material mass is melted first, and the central portion not irradiated with the laser beam is melted by heat conduction from the melt in the peripheral region that has been melted first.

[0078] 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 stably and continuously controlled with good controllability. That is, by providing such a temperature distribution in the melt pool on the upper surface of the raw material mass, the growth of the thin plate-like single crystal can be stably and continuously carried out from this central portion.

[0079] Furthermore, the laser beam may be irradiated from an obliquely upward direction or vertically from directly above with respect to the upper surface of the raw material mass. However, it is preferable to adjust the irradiation angle to an optimal angle according to the thermal conductivity and thickness of the thin plate-like single crystal material. In the case of a material with a high thermal conductivity, it is preferable to greatly control the angle of the laser beam irradiation from the horizontal direction. In the case of a material with a low thermal conductivity, it is preferable to slightly control the angle of the laser beam irradiation from the horizontal direction.

[0080] In addition, the method for manufacturing a thin plate-like single crystal of the present invention After the continuous manufacturing process, A winding step of winding the continuously manufactured thin plate-like single crystal into a roll shape, It is further characterized by having. If it has such a winding step, the continuously manufactured thin plate-like single crystal can be surely wound into a roll shape, and the thin plate-like single crystal can be efficiently manufactured.

[0081] In addition, the method for manufacturing a thin plate-like single crystal of the present invention In the melting step, When the thin plate-like single crystal to be manufactured is a decomposition-melting substance, a composition of a liquid phase (referred to as a solvent phase) that coexists in equilibrium with its composition is first placed in a required amount on the upper surface of the raw material mass for manufacturing the thin plate-like single crystal.

[0082] Furthermore, the method for manufacturing a thin plate-like single crystal of the present invention In the melting step, When the thin plate single crystal to be manufactured is a solid solution substance containing an additive, a composition of a liquid phase (referred to as a solvent phase) that coexists in equilibrium with the composition is first placed in a required amount on the upper surface of the raw material mass for manufacturing the thin plate single crystal.

[0083] As a result, when a thin plate single crystal solidifies from the solvent phase first formed on the upper surface of the raw material mass, the amount of the solvent phase decreases and the composition has less crystal components. Therefore, the intensity of the laser light reaching the lower side of the solvent phase increases and the temperature rises, so the melting of the raw material mass progresses.

[0084] As a result, crystallization and melting of the raw material mass proceed simultaneously, so the additive concentration in the obtained product (thin plate 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 capable of manufacturing a single crystal product with a homogeneous composition by the melt method.

[0085] In this way, by first placing a required amount of the composition of the liquid phase that coexists in equilibrium with the composition of the thin plate single crystal to be manufactured on the upper surface of the raw material mass, a thin plate single crystal with a homogeneous and optimal composition can be continuously manufactured.

[0086] Further, the method for manufacturing a thin plate single crystal of the present invention in the growth step, immerses the lower surface of the thin plate seed single crystal in the center of the melt on the surface of the upper surface of the melted raw material mass for manufacturing the thin plate single crystal.

[0087] The center of the melt is a site where the melt continuously accumulates. If the lower surface of the thin plate seed single crystal is immersed in this center, a thin plate single crystal can be continuously manufactured by pulling up the thin plate seed single crystal upward by a lifting means.

Advantages of the Invention

[0088] According to the thin-plate single-crystal manufacturing apparatus and the thin-plate single-crystal manufacturing method of the present invention, the surface of the upper surface of the raw material mass 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, so that a thin-plate single-crystal having an optimal composition and uniform additive concentration and a thickness of about several hundred μm can be manufactured continuously with high precision at low cost.

Brief Description of the Drawings

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BEST MODE FOR CARRYING OUT THE INVENTION

[0090] Hereinafter, 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 with reference to the drawings. The thin-plate single crystal manufacturing apparatus and the thin-plate single crystal manufacturing method of the present invention are for manufacturing a thin-plate single crystal having an optimal composition and a homogeneous additive concentration and a thickness of about several hundred μm at low cost and continuously with high precision.

[0091] <Thin-plate single crystal manufacturing apparatus 10> [First Embodiment] As shown in FIG. 1, the thin-plate single crystal manufacturing apparatus 10 according to the first embodiment of the present invention is provided with a raw material block for manufacturing a thin-plate single crystal (hereinafter also referred to as a raw material block) 12 on a mounting table 82 disposed below in a chamber 80. This raw material block 12 has a substantially rectangular parallelepiped shape and is, for example, a plate-like body like a book.

[0092] In addition, an infrared ray irradiation means 20 for irradiating infrared rays 16 to the upper surface 14 of the substantially rectangular parallelepiped raw material block 12 and melting the surface of the upper surface 14 is provided on the upper side of the chamber 80. The infrared rays 16 irradiated from the infrared ray irradiation means 20 are preferably laser light 16a.

[0093] That is, as shown in FIG. 2, the shape of the irradiation region of the laser light 16a is an elongated hollow rectangular shape in the horizontal direction (the vertical direction in FIG. 2), and as shown in FIG. 3, the center of the upper surface 14 of the raw material block 12 is excluded. It is preferable to irradiate the laser light 16a so as to form the elongated hollow rectangular irradiation region in the peripheral region.

[0094] Here, the laser beam 16a irradiated from the infrared irradiation means 20 is incident into the chamber 80 from a window 22 provided on the side portion of the chamber 80, and is preferably irradiated onto the peripheral region excluding the central portion of the upper surface 14 of the raw material mass 12 through the mirror 24 in the chamber 80. At this time, the laser beam 16a may be irradiated from an obliquely upward direction with respect to the upper surface 14 of the raw material mass 12 as shown in FIG. 1, or may be irradiated vertically from directly above with respect to the upper surface 14 of the raw material mass 12 as shown in FIG. 4. However, 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-like single crystal 40 to be manufactured.

[0095] As a result, the peripheral region excluding the central portion of the upper surface 14 of the raw material mass 12 is melted earlier than the central portion, and the central portion where the laser beam 16a does not hit is melted by the heat conduction from the melt 18 in the peripheral region that has been melted earlier.

[0096] Therefore, the temperature of the central portion can be controlled to be lower than the temperature of the peripheral region. By providing such a temperature distribution in the melt 18 (melt pool) on the upper surface 14 of the raw material mass 12, the growth of the thin plate-like single crystal 40 can be stably and continuously performed from this central portion.

[0097] That is, as shown in FIGS. 5 and 6, by irradiating the laser beam 16a onto the peripheral region excluding the central portion of the upper surface 14 of the raw material mass 12, the melt 18 is formed deeper in the peripheral region, and the melt 18 having a lower temperature and shallower depth is formed in the central portion than in the peripheral region.

[0098] Note that a preheating means 70 for preheating the raw material mass 12 is provided around the raw material mass 12 as shown in FIGS. 1, 3, and 4. It is preferable to preheat the raw material mass 12 to near the melting point in advance before melting the surface of the upper surface 14 of the raw material mass 12 by the infrared irradiation means 20. By preheating in this way, the irradiation amount of the infrared rays 16 by the infrared irradiation means 20 can be significantly reduced later, and the range of the melt 18 (melt pool) can be finely adjusted by finely adjusting the position and the irradiation amount.

[0099] On the other hand, above the chamber 80, there is provided a lifting means 30 that immerses the lower surface 34 of the thin-plate seed single crystal 32 in the melt 18 obtained on the surface of the upper surface 14 of the raw material mass 12 melted by the infrared irradiation means 20, and then pulls the thin-plate seed single crystal 32 upward from the immersed state.

[0100] The lifting means 30 is not particularly limited, but for example, it is preferably a winding means 50 that continuously winds up the manufactured thin-plate single crystal 40 in a roll shape. As a specific configuration, it has a winding shaft 36 that continuously winds up the manufactured thin-plate single crystal 40 and a rotating means 38 that rotates the winding shaft 36.

[0101] Here, the size of the lower surface 34 of the thin-plate seed single crystal 32 is set to be slightly smaller than the upper surface 14 of the raw material mass 12. For example, as a specific relationship between the sizes of the two, the size of the upper surface 14 of the raw material mass 12 is set to be several millimeters or more larger than the size of the lower surface 34 of the thin-plate seed single crystal 32 in both the thickness direction and the lateral direction. That is, it is set to a size that allows the entire lower surface 34 of the thin-plate seed single crystal 32 to be immersed in the melt 18.

[0102] Then, as shown in FIG. 7, by immersing the lower surface 34 of the thin-plate seed single crystal 32 in the center of the melt 18 obtained on the surface of the upper surface 14 of the raw material mass 12 by the infrared irradiation means 20 through the lifting means 30, crystal growth of the single crystal is started from the lower surface 34 of the immersed thin-plate seed single crystal 32, and further, by pulling the thin-plate seed single crystal 32 upward through the lifting means 30, a thin-plate single crystal 40 is continuously manufactured.

[0103] The thickness of the thin-plate single crystal 40 to be manufactured can be adjusted by, for example, the melt temperature and the pulling speed of the thin-plate seed single crystal 32 in the steady state, and can be set to a thickness of, for example, about 100 μm to more than 3000 μm. However, when the thickness of the thin-plate single crystal 40 exceeds 500 μm, the winding means 50 becomes large-sized. Therefore, when it exceeds 500 μm, it can also be pulled upward without being wound to obtain a product. In particular, when manufacturing a silicon thin-plate single crystal for a solar cell, the thickness of the thin-plate single crystal 40 is preferably in the range of 200 μm to 400 μm.

[0104] 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 single crystal 40 increases, so the pulling speed is slowed down. When the melt temperature is low, the pulling speed of the thin-plate single crystal 40 is increased to improve 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 characteristics of the thin-plate single crystal 40 deteriorate. Therefore, it is preferable to appropriately adjust the pulling speed.

[0105] The thickness of the thin-plate seed single crystal 32 immersed in the melt 18 may be, for example, about 300 μm to 500 μm. With a thin-plate seed single crystal 32 having such a thickness, a thin-plate single crystal 40 having a desired thickness can be continuously manufactured by adjusting the melt temperature and the pulling speed, which is preferable.

[0106] In FIGS. 1 and 4, the thickness of the thin-plate single crystal 40 and the thickness of the thin-plate seed single crystal 32 are shown as different. This is deliberately done so that the thin-plate single crystal 40 and the thin-plate seed single crystal 32 can be distinguished in the figure, and in particular, it does not limit the relationship between the thicknesses of the two.

[0107] At this time, it is preferable to suspend a plurality of (three in FIG. 7) thin-plate seed single crystals 32 on the winding shaft 36 of the winding means 50 via a plurality of heat-resistant and high-strength thin wires 52. In particular, in the thin-plate seed single crystal 32, if the thickness of the portion where the thin wire 52 is attached is equal to or less than the thickness of the thin-plate seed single crystal 32, when the thin-plate single crystal 40 is wound around the winding shaft 36, it is possible to reliably prevent the surface of the thin-plate single crystal 40 from contacting the thin wire 52 and being damaged.

[0108] The method of attaching the thin wire 52 to the thin-plate seed single crystal 32 is not particularly limited. For example, several through-holes for tying the thin wire 52 are provided at the ends of the thin-plate seed single crystal 32, and concave grooves are provided on both surfaces of the thin-plate seed single crystal 32 so as to communicate with the through-holes. When the thin wire 52 is tied to the thin-plate seed single crystal 32, the thin wire 52 is fitted into the concave grooves so that the thin wire 52 does not protrude outward from the thin-plate seed single crystal 32. By doing so, it is possible to reliably prevent the surface of the thin-plate single crystal 40 from contacting the thin wire 52 and being damaged when the thin-plate single crystal 40 is wound.

[0109] In addition, in this thin-plate single crystal manufacturing apparatus 10, between the lifting means 30 and the raw material mass 12, there is provided a vibration damping member 60 that prevents the vibration of the continuously manufactured thin-plate single crystal 40 and keeps the growth position within a predetermined range so as not to shift, and a shielding member 62 that shields the radiant heat emitted from the melt 18 so that it is difficult to reach the continuously manufactured thin-plate single crystal 40.

[0110] By providing the vibration damping member 60, it is possible to suppress the manufactured thin-plate single crystal 40 from swinging too much to the left and right and causing a shift in the growth position, and it is possible to continuously manufacture high-quality thin-plate single crystals 40.

[0111] Moreover, by providing the shielding member 62, the production speed of the thin plate single crystal 40 can be increased. That is, the method of melting the raw material and solidifying it as a single crystal is called the melt method. In this melt method, the growth rate of the single crystal can be increased by efficiently exhausting the latent heat of crystallization released when the crystal solidifies through heat conduction in the single crystal in contact with the melt.

[0112] Therefore, for example, if the 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 single crystal 40 can be reduced, and the latent heat of crystallization can be efficiently exhausted without raising the temperature of the thin plate single crystal 40, thereby increasing the production efficiency of the thin plate single crystal 40.

[0113] In this way, by using the present thin plate single crystal manufacturing apparatus 10, the thin plate single crystal 40 can be continuously manufactured. However, when continuously manufacturing the thin plate single crystal 40, the melt 18 obtained on the upper surface 14 of the raw material mass 12 decreases, and the position of the upper surface 14 will drop. In this case, it is necessary to control the irradiation position of the infrared rays by the infrared ray irradiation means 20 to be a desired position.

[0114] In the present embodiment, instead of controlling the irradiation position of the infrared rays 16, the mounting table 82 on which the raw material mass 12 is mounted is provided with position control means 84 for controlling the vertical position of the mounting table 82.

[0115] By providing the position control means 84 in this way, even if the position of the melt 18 on the upper surface 14 of the raw material mass 12 drops as the continuously manufactured thin plate 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 mass 12 at the same initial position, and the liquid level position of the melt 18 can always be kept at the same position.

[0116] Therefore, the infrared ray 16 should always be irradiated at the same position, and the thin-plate single crystal 40 can be stably and continuously manufactured with a good yield. As in the thin-plate single crystal manufacturing apparatus 10 shown in FIGS. 4 and 6 here, when the laser beam 16a is vertically irradiated from directly above the raw material mass 12 onto the upper surface 14 of the raw material mass 12, even if the position of the upper surface 14 of the raw material mass 12 fluctuates, the temperature of the melt 18 does not change. Therefore, it is not necessary to control the position of the upper surface 14 of the raw material mass 12. The raw material mass 12 used in the above-described thin-plate single crystal manufacturing apparatus 10 is a raw material mass 12 having the composition of the material of the thin-plate single crystal 40 to be manufactured. However, when the material of the thin-plate single crystal 40 is a decomposable and fusible substance, even if this raw material mass 12 is melted and solidified as it is in this thin-plate single crystal manufacturing apparatus 10, the target thin-plate single crystal 40 cannot be obtained.

[0117] Therefore, a composition of a liquid phase that is in equilibrium coexistence with the composition of the material of the thin-plate single crystal 40 to be manufactured is placed on the upper surface 14 of the raw material mass 12 in an amount corresponding to the amount of the liquid phase, and this is melted first. In this way, a state is obtained in which the solvent dissolved on the upper surface 14 of the raw material mass 12 is loaded.

[0118] When the thin-plate single crystal 40 is manufactured in this way, since the same amount of the raw material mass 12 that has solidified as a single crystal melts, the amount and composition of the solvent do not change from the beginning to the end, and it appears as if the solvent phase is moving while dissolving the raw material mass 12 and precipitating the single crystal.

[0119] This scheme is called the "solvent movement method". When the thin-plate single crystal 40 obtained by this thin-plate single crystal manufacturing apparatus 10 is a decomposable and fusible substance or a solid solution substance containing an additive, it is important to use this "solvent movement method" to make the additive concentration in the obtained thin-plate single crystal 40 uniform.

[0120] [Second Embodiment] Next, a second embodiment of the thin-plate single crystal manufacturing apparatus 10 of the present invention will be described. FIGS. 8 and 9 show the thin-plate single crystal manufacturing apparatus 10 according to the second embodiment of the present invention.

[0121] The thin-plate single-crystal manufacturing apparatus 10 shown in FIGS. 8 and 9 basically has the same configuration as the thin-plate single-crystal manufacturing apparatus 10 of the first embodiment shown in FIGS. 1 to 7. Therefore, the same reference numerals are assigned to the same constituent members, and the detailed description thereof is omitted, and the differences will be described.

[0122] The thin-plate single-crystal manufacturing apparatus 10 in the second embodiment of the present invention is different from the thin-plate single-crystal manufacturing apparatus 10 in the first embodiment in that, as shown in FIGS. 8 and 9, in the chamber 80, a gas introduction device 90 for filling the inside of the chamber 80 with an atmosphere gas containing an additive is provided.

[0123] The gas introduction device 90 is provided on the upper side of the chamber 80, and the atmosphere gas is introduced into the chamber 80 from the gas introduction device 90 through the introduction pipe 92. Further, a discharge pipe 94 is provided on the lower side of the chamber 80, and the atmosphere gas can be discharged from the discharge pipe 94 to the outside of the chamber 80.

[0124] Thereby, the inside of the chamber 80 can be maintained in a state filled with an atmosphere gas suitable for manufacturing the thin-plate single-crystal 40, and the thin-plate single-crystal 40 with a uniform additive concentration and high quality can be continuously manufactured.

[0125] The atmosphere gas may be prepared according to the characteristics of the material of the thin-plate single-crystal 40 to be manufactured. For example, when manufacturing a thin-plate single-crystal of N-type silicon, it is preferable to introduce a high-purity argon gas containing phosphine (PH 3 ) at an optimum concentration into the chamber 80.

[0126] Further, as shown in FIG. 9, for example, a window 22 for guiding infrared rays 16 (laser beam 16a) irradiated from the infrared ray irradiation means 20 into the chamber 80, a reflecting mirror 24 for guiding the infrared rays 16 (laser beam 16a) guided into the chamber 80 to the upper surface 14 of the raw material mass 12, etc. may be covered with the cover member 42, and the atmosphere gas may be positively introduced from the gas introduction device 90 into the cover member 42.

[0127] If the atmosphere gas is introduced into the cover member 42 in this way, it is possible to prevent the evaporation products generated from the melt 18 from adhering to the window 22, the reflecting mirror 24, etc., and it is possible to stably and continuously manufacture the thin plate-like single crystal 40 with a homogeneous additive concentration and high quality with a good yield.

[0128] [Third Embodiment] Next, a third embodiment of the thin plate-like single crystal manufacturing apparatus 10 of the present invention will be described. FIGS. 10 and 11 show the thin plate-like single crystal manufacturing apparatus 10 in the third embodiment of the present invention.

[0129] The thin plate-like single crystal manufacturing apparatus 10 shown in FIGS. 10 and 11 basically has the same configuration as the thin plate-like single crystal manufacturing apparatus 10 in the first embodiment shown in FIGS. 1 to 7. Therefore, the same reference numerals are given to the same constituent members and the detailed description thereof is omitted, and the differences will be described.

[0130] The thin plate-like single crystal manufacturing apparatus 10 in the third embodiment of the present invention is different from the thin plate-like single crystal manufacturing apparatus 10 in the first embodiment in that, as shown in FIGS. 10 and 11, a plurality (two in FIG. 10) of elevating means 30 are provided above the raw material mass 12.

[0131] Specifically, two elevating means 30 (winding means 50) are arranged side by side horizontally at the upper part of the chamber 80. The thin plate-shaped seed single crystals 32, 32 are immersed in the melt 18 on the upper surface 14 of the raw material mass 12, and by pulling them upward with the elevating means 30, 30 (winding means 50, 50) respectively, the thin plate-shaped single crystals 40, 40 can be manufactured respectively. If a plurality of elevating means 30 are provided above the raw material mass 12 in this way, the manufacturing efficiency of the thin plate-shaped single crystal 40 can be significantly improved compared to the case where there is only one elevating means 30.

[0132] <Method for manufacturing thin plate-shaped single crystal> Next, a method for manufacturing a thin plate-shaped single crystal using the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention will be described.

[0133] First, as shown in Fig. 12(a), the raw material mass 12 is placed on the mounting table 82 in the chamber 80, the inside of the chamber 80 is sealed, and the thin plate-shaped seed single crystal 32 is arranged above the upper surface of the raw material mass 12 so that the length direction of the raw material mass 12 coincides with the extending direction of the thin plate-shaped seed single crystal 32. The thin plate-shaped seed single crystal 32 is suspended from the winding shaft 36 of the winding means 50 via the thin wire 52.

[0134] The atmosphere inside the chamber 80 is evacuated through an exhaust pipe (not shown), and an atmosphere gas suitable for the characteristics of the material of the thin plate-shaped single crystal 40 to be manufactured is introduced into the chamber 80 through a gas introduction device (not shown).

[0135] Next, the temperature of the raw material mass 12 is raised to near the melting point by the preheating means 70. Then, as shown in Fig. 12(b), infrared rays 16 (laser light 16a) are irradiated onto the upper surface 14 of the raw material mass 12 through the infrared ray irradiation means 20 to melt the surface of the upper surface 14.

[0136] The shape of the irradiation area of the infrared rays 16 (laser light 16a) is an elongated hollow square shape in the horizontal direction, and the laser light 16a is aligned and irradiated so as to form this elongated hollow square-shaped irradiation area in the peripheral area excluding the central part of the upper surface 14 of the raw material mass 12.

[0137] As a result, the peripheral region of the upper surface 14 of the raw material mass 12 excluding the central portion is melted earlier than the central portion, and the central portion not irradiated by the laser beam 16a is melted by heat conduction from the melt 18 in the peripheral region that has been melted earlier.

[0138] Next, as shown in FIG. 12(c), the lower surface 34 of the thin plate-shaped seed single crystal 32 is immersed in the central portion of the melt 18 obtained on the upper surface 14 of the raw material mass 12 via the elevating means 30 (winding means 50), and the growth of the single crystal is started from the lower surface 34 of the thin plate-shaped seed single crystal 32.

[0139] Next, as shown in FIG. 13(a), the thin plate-shaped seed single crystal 32 is pulled upward via the elevating means 30 (winding means 50) to continuously manufacture the thin plate-shaped single crystal 40. Next, as shown in FIG. 13(b), as the thin plate-shaped single crystal 40 is continuously manufactured, the position of the mounting table 82 is moved upward via the position control means 84. Thereby, even if the position of the melt 18 of the raw material mass 12 drops as it is pulled up, the position of the raw material mass 12 is position-controlled so as to maintain the initial position, and the liquid level position of the melt 18 is always kept at the same position. Here, as in the thin plate-shaped single crystal manufacturing apparatus 10 shown in FIGS. 4 and 6, when the laser beam 16a is irradiated vertically from directly above the raw material mass 12 onto the upper surface 14 of the raw material mass 12, the temperature of the melt 18 does not change even if the position of the upper surface 14 of the raw material mass 12 fluctuates. Therefore, it is not necessary to control the position of the upper surface 14 of the raw material mass 12 to a fixed position.

[0140] Finally, as shown in FIG. 13(c), the irradiation amount of the infrared rays 16 (laser beam 16a) by the infrared ray irradiation means 20 is increased to raise the temperature of the melt 18, the thin plate-shaped single crystal 40 is separated from the melt 18, the winding of the thin plate-shaped single crystal 40 continuously manufactured by the elevating means 30 (winding means 50) is completed, and when the irradiation of the infrared rays 16 (laser beam 16a) by the infrared ray irradiation means 20 is terminated, the manufacture of the thin plate-shaped single crystal 40 is completed.

Example

[0141] [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.

[0142] As the raw material ingot 12, a cubic raw material ingot 12 with 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 seed single crystal 32, a thin-plate seed single crystal 32 of silicon 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 was used as the plate surface of the thin-plate seed single crystal 32. The thin-plate seed single crystal 32 was previously attached to the winding shaft 36 of the winding means 50 via three thin wires 52.

[0143] First, this raw material ingot 12 was placed on the mounting table 82 in the chamber 80, the chamber 80 was closed, and the internal atmosphere was made into a vacuum state. Next, an atmosphere gas was introduced into the chamber 80. As the atmosphere gas, high-purity argon gas was used, and a gas obtained by adding a necessary amount of phosphine (PH 3 ) gas for adding phosphorus was used.

[0144] This raw material ingot 12 was first heated to near the melting point by the preheating means 70. After confirming the heating, a laser beam with a width of 20 mm and a length of 396 mm was irradiated from the left and right at an angle of 60 degrees from the horizontal direction, 2 mm away from the end portion, to the peripheral region excluding the central portion and the outermost peripheral portion of the upper surface 14 of this raw material ingot 12. At the same time, laser beams 16a having a right-angled irradiation region shape with a width of 6 mm and separated by 2 mm from the end on the center line of the raw material ingot 12 were irradiated from the horizontal direction at an angle of 60 degrees to both end portions in the length direction of the raw material ingot 12. The shape of the irradiation region is an elongated hollow square shape in the horizontal direction as a whole. Thereby, the entire upper surface 14 was melted.

[0145] Rotate the winding shaft 36 of the winding means 50, immerse the lower surface 34 of the above-mentioned thin plate-shaped seed single crystal 32 of silicon into the central part of the melt 18 obtained by melting, and while growing the thin plate-shaped single crystal 40 from the lower surface 34 of the thin plate-shaped seed single crystal 32, this time rotate the winding shaft 36 in the reverse direction, pull up the thin plate-shaped seed single crystal 32 upward, and continuously wind the thin plate-shaped single crystal 40 around the winding shaft 36 in a roll shape at the upper part to manufacture a long thin plate-shaped single crystal 40 with a length exceeding 10 m.

[0146] Note that the thin plate-shaped seed single crystal 32 is set on the winding shaft 36 of the winding means 50 by a carbon fiber thin wire 52 with a diameter of about 0.05 mm, and the thin plate-shaped seed single crystal 32 is moved in the vertical direction by controlling the rotation direction and rotation speed of the winding shaft 36 by the rotation means 38.

[0147] When the thin plate-shaped seed single crystal 32 is immersed in the central part of the melt 18, crystallization immediately starts. Although the immersed part of the thin plate-shaped seed single crystal 32 becomes thick, it was confirmed that if left as it is, the thickened part melts and becomes thin.

[0148] In this state, pull up the thin plate-shaped seed single crystal 32 upward, confirm the thickness of the manufactured thin plate-shaped single crystal 40 with a camera, control the thickness to 0.3 mm while adjusting the pulling speed and the irradiation intensity of the laser beam 16a, rotate the winding shaft 36, and continuously wind the thin plate-shaped single crystal 40 around the winding shaft 36.

[0149] Note that it was confirmed that when the pulling speed of the thin plate-shaped seed single crystal 32 is slowed down, the thickness of the thin plate-shaped single crystal 40 becomes thick, and when the pulling speed is increased, the thickness of the thin plate-shaped single crystal 40 becomes thin. The melt temperature was adjusted so that the thin plate-shaped single crystal 40 with a thickness of 0.3 mm continuously pulled up at a speed of 30 mm per minute.

[0150] Here, as the thin plate-shaped single crystal 40 is pulled up, the liquid level position of the melt 18 of the raw material block 12 drops. Therefore, the position of the mounting table 82 on which the raw material block 12 is placed is controlled to a predetermined position via the position control means 84 so as to maintain the initial position, and the liquid level position of the melt 18 of the raw material block 12 is always made the same as the initial position.

[0151] When the thin-plate single crystal 40 with a length exceeding 10 m, a thickness of 0.3 mm, and a width of 383 - 386 mm manufactured in this way was confirmed using the secondary ion mass spectrometry (SIMS) method, it was confirmed that the concentration of phosphorus as an additive was homogeneous and of high quality at the optimal composition, and the superiority of the thin-plate single crystal manufacturing apparatus 10 and the thin-plate single crystal manufacturing method of the present invention could be confirmed.

[0152] Next, an overview of the thin-plate single crystal manufacturing apparatus 10 of the present invention described above and the thin-plate single crystal manufacturing method using this thin-plate single crystal manufacturing apparatus 10 will be described. The most significant factor enabling the continuous and stable production of the thin-plate single crystal 40 by the thin-plate single crystal manufacturing apparatus 10 and the thin-plate single crystal manufacturing method of the present invention is that the melting of the raw material mass 12 and the crystallization from the obtained melt 18 can be generally controlled independently.

[0153] That is, heating is required to melt the raw material mass 12 to obtain the melt 18, while cooling is required to solidify and crystallize the melt 18, and the two are contradictory. Therefore, in the present invention, the laser beam 16a is not directly irradiated on the portion where crystallization occurs (the central portion of the melt 18), but on the portion other than the portion where crystallization occurs (the peripheral region excluding the central portion of the melt 18), so as to melt the upper surface 14 of the raw material mass 12 and conduct the heat of the melt 18 to the portion where crystallization occurs (the central portion of the melt 18), thereby forming the melt 18 also at the central portion of the upper surface 14.

[0154] As a result, the temperature of the portion where crystallization occurs (the central portion of the melt 18) becomes lower than the temperature of the portion that is melted by the irradiation of the laser beam 16a (the peripheral region excluding the central portion of the melt 18), facilitating crystallization.

[0155] When the thin-plate-shaped seed single crystal 32 is immersed in the central part of the melt 18, the heat of the melt 18 is transmitted to the lower surface 34 of the immersed thin-plate-shaped seed single crystal 32. Therefore, the temperature of the melt in contact with the lower surface 34 becomes low, and crystallization proceeds 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 portion that has solidified rapidly until then gradually melts due to the heat from the surrounding melt 18 and reaches a steady state.

[0156] When the thin-plate-shaped seed single crystal 32 is pulled upward in this state, the thin-plate-shaped seed single crystal 32 will move to the low-temperature part. Therefore, crystallization proceeds on the lower surface 34 in contact with the melt 18. If the pulling speed of the thin-plate-shaped seed single crystal 32 is increased and crystallization cannot catch up, the thickness of the manufactured thin-plate-shaped single crystal 40 becomes thin. If the pulling speed is decreased, crystallization proceeds, so the thickness of the thin-plate-shaped single crystal 40 increases.

[0157] Therefore, if the temperature of the melt 18 is controlled to be lower, crystallization becomes easier and the thickness of the thin-plate-shaped single crystal 40 becomes thicker. Thus, even if the pulling speed is increased, a thin-plate-shaped single crystal 40 with a predetermined thickness can be continuously manufactured.

[0158] Note that increasing the pulling speed can improve the manufacturing efficiency of the thin-plate-shaped single crystal 40. However, if it is made too fast, the possibility of cell growth increases. When cell growth occurs, the concentration of phosphorus, which is an additive, fluctuates greatly locally, and the characteristics of the single crystal deteriorate. Therefore, it is important to continuously manufacture the thin-plate-shaped single crystal 40 at the fastest possible pulling speed while suppressing the occurrence of cell growth.

[0159] Furthermore, the present invention has made it possible for the first time to manufacture a high-quality thin-plate-shaped single crystal 40 with a homogeneous composition for so-called incongruent melting substances such as decomposition and melting substances and solid solution single crystals. Such a thin-plate-shaped single crystal 40 with a homogeneous composition of an incongruent melting substance has been impossible to manufacture by the conventional method.

[0160] That is, in order to produce a homogeneous composition single crystal of these incongruent melting substances by the 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 12 of the target composition must be produced in advance. In principle, there is no method other than applying the so-called solvent transfer method in which the dissolution of the raw material mass 12 and the precipitation of a single crystal from the solvent are advanced simultaneously using a solvent having a solvent composition that coexists in equilibrium with the target composition substance.

[0161] In this patent, after arranging a required amount of the solvent phase component on the upper surface 14 of the raw material mass 12, infrared rays 16 are irradiated to melt it and form a solvent solution. Then, by simultaneously advancing the production of a single crystal from the solvent and the dissolution of the raw material mass 12 into the solvent, the solvent transfer method is applied, making it possible to produce a thin plate-shaped single crystal 40 with a homogeneous composition.

[0162] As described above, the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention and the thin plate-shaped single crystal manufacturing method using this thin plate-shaped single crystal manufacturing apparatus 10 have been described. However, the present invention is not limited to the above-described embodiments.

[0163] For example, in the above-described thin plate-shaped single crystal manufacturing apparatus 10, the first to third embodiments have been separately described, but these may be combined to form the thin plate-shaped single crystal manufacturing apparatus 10 of the present invention. That is, for example, a thin plate-shaped single crystal manufacturing apparatus 10 formed by combining the second and third embodiments with the first embodiment may also be used.

[0164] Furthermore, in the above-described thin plate-shaped single crystal manufacturing apparatus 10, the case where the infrared irradiation means 20 is provided so as to be able to irradiate parallel to each side of the rectangular shape is taken as an example, but it is not limited to this, and only one infrared irradiation means 20 may be used.

[0165] Also, if the laser beam 16a can be irradiated so as to form a horizontally elongated hollow rectangular irradiation region that matches the peripheral region excluding the central portion of the upper surface 14 of the raw material mass 12, this horizontally elongated hollow rectangular irradiation region may be formed by a plurality of laser beams 16a, and the cross-sectional shape of the laser beam 16a irradiated from the infrared irradiation means 20 in terms of number or one is not limited.

[0166] That is, the laser beam 16a having a U-shaped cross section is irradiated onto the upper surface 14 of the raw material mass 12 from the left and right respectively, and an irradiation region having a horizontally elongated hollow rectangular cross-sectional shape may be formed by two U-shaped cross-sectional laser beams 16a, 16a, or an irradiation region having a horizontally elongated hollow rectangular shape may be formed by four laser beams having a bar-shaped cross section.

[0167] Furthermore, although the thickness of the thin plate single crystal 40 to be manufactured is described as being about 100 μm to 3000 μm, it is also possible to manufacture in principle even with a thickness greater than this, for example, 5000 μm or more, and the thickness is not limited to the above range.

[0168] Also, regarding the thickness of the thin plate seed single crystal 32 immersed in the melt 18, although it is described as being about 300 μm to 500 μm, it is also possible to manufacture the thin plate single crystal 40 in principle even with a thickness outside this range, and the thickness is not limited to the above range.

[0169] Thus, the thin plate single crystal manufacturing apparatus 10 and the thin plate single crystal manufacturing method of the present invention can be variously modified without departing from the object of the present invention.

Explanation of Signs

[0170] 10 Thin plate single crystal manufacturing apparatus 12 Raw material mass for manufacturing thin plate single crystal (raw material mass) 14 Upper surface 16 Infrared ray 16a Laser beam 18 Melt 20 Infrared irradiation means 22 Window 24 Mirror 30 Lifting means 32 Sheet-like seed single crystal 34 Lower surface 36 Winding shaft 38 Rotating means 40 Sheet-like single crystal 42 Cover member 50 Rewinding means 52 Fine wire 54 Feeding means 56 Feed pipe 60 Anti-vibration 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

1. An infrared irradiation means for irradiating infrared rays onto the upper surface of a raw material mass for manufacturing a thin plate single crystal and melting the surface of the upper surface; A lifting means for immersing the lower surface of a thin plate seed single crystal in the melt obtained on the surface of the upper surface melted by the infrared irradiation means and then pulling up the thin plate seed single crystal upward from the immersed state; Comprising: By immersing the lower surface of the thin plate seed single crystal into the melt obtained on the surface of the upper surface of the raw material mass for manufacturing a thin plate single crystal by the infrared irradiation means through the lifting means, crystal growth of the single crystal is started from the lower surface of the immersed thin plate seed single crystal, and further by pulling up the thin plate seed single crystal upward through the lifting means, it is configured to continuously manufacture a thin plate single crystal, On the upper surface of the raw material mass for manufacturing the thin plate single crystal, A thin plate single crystal manufacturing apparatus characterized in that a necessary amount of a composition of a liquid phase that coexists in equilibrium with the composition of the thin plate single crystal to be manufactured is initially arranged.

2. The thin plate single crystal manufacturing apparatus according to claim 1, wherein the infrared rays irradiated from the infrared irradiation means are laser light.

3. The shape of the irradiation region of the laser light is a horizontally elongated hollow square shape, The thin plate single crystal manufacturing apparatus according to claim 2, wherein the laser light is irradiated so as to form the hollow square-shaped irradiation region on the peripheral region of the upper surface of the raw material mass for manufacturing the thin plate single crystal excluding the central portion.

4. The lifting means is A winding means for continuously winding up the manufactured thin plate single crystal in a roll shape, The winding means is A winding shaft for continuously winding up the thin plate single crystal, A rotating means for rotating the winding shaft, Comprising: The thin plate single crystal manufacturing apparatus according to any one of claims 1 to 3, characterized in that the thin plate seed single crystal is configured to be suspended from the winding shaft.

5. The thin plate seed single crystal is The thin plate single crystal manufacturing apparatus according to claim 4, characterized in that it is suspended from the winding shaft via a plurality of thin wires.

6. In the thin plate seed single crystal, The thickness of the portion where the thin wire is attached is The thin plate single crystal manufacturing apparatus according to claim 5, characterized in that it is not larger than the thickness of the thin plate single crystal to be manufactured.

7. Between the lifting means and the raw material mass for manufacturing the thin plate single crystal, A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 6, characterized in that a shaking prevention member for preventing shaking of the continuously manufactured thin-plate single crystal is provided.

8. Between the lifting means and the raw material mass for manufacturing the thin-plate single crystal, A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 7, characterized in that a shielding member is provided for shielding the radiant heat emitted from the melt so as to be difficult to reach the continuously manufactured thin-plate single crystal.

9. A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 8, characterized in that the raw material mass for manufacturing the thin-plate single crystal is substantially a rectangular parallelepiped.

10. A mounting table for mounting the raw material mass for manufacturing the thin-plate single crystal, Position control means for controlling the position of the mounting table to a predetermined position, A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 9, characterized by comprising.

11. The lifting means is A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 10, characterized in that the lower surface of the thin-plate seed single crystal is immersed in the center of the melt on the upper surface of the raw material mass for manufacturing the thin-plate single crystal melted by the infrared irradiation means.

12. Around the raw material mass for manufacturing the thin-plate single crystal, A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 11, characterized in that preheating means for preheating the raw material mass for manufacturing the thin-plate single crystal is provided.

13. At least the raw material mass for manufacturing the thin-plate single crystal is disposed in the chamber, A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 12, characterized in that the lifting means is disposed above the chamber.

14. A thin-plate single-crystal manufacturing apparatus according to claim 13, characterized by comprising a gas introduction device for filling the inside of the chamber with an atmospheric gas containing an additive.

15. The lifting means is A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 14, characterized in that a plurality of the lifting means are provided above the raw material mass for manufacturing the thin-plate single crystal.

16. A thin-plate single-crystal manufacturing apparatus according to any one of claims 1 to 15, characterized in that the thickness of the thin-plate seed single crystal is in the range of 300 μm to 500 μm.

17. A melting step of irradiating the upper surface of the raw material mass for manufacturing the thin-plate single crystal with infrared rays through the infrared irradiation means to melt the surface of the upper surface of the raw material mass for manufacturing the thin-plate single crystal, In the melting step, the lower surface of the thin-plate seed single crystal is immersed in the melt obtained on the upper surface of the raw material mass for producing the thin-plate single crystal through lifting means, and a growth step of starting the growth of the single crystal from the lower surface of the thin-plate seed single crystal is carried out. In the growth step, the thin-plate seed single crystal in which the growth of the single crystal has started is pulled upward, and a continuous production step of continuously producing a thin-plate single crystal is carried out. It has at least In the melting step, When the thin-plate single crystal to be produced is a decomposed melt substance, a composition of a liquid phase in equilibrium coexistence with its composition is first placed in a required amount on the upper surface of the raw material mass for producing the thin-plate single crystal. A method for producing a thin-plate single crystal is characterized in that.

18. A melting step of irradiating infrared rays to the upper surface of the raw material mass for producing a thin-plate single crystal through infrared irradiation means and melting the surface of the upper surface of the raw material mass for producing the thin-plate single crystal; In the melting step, the lower surface of the thin-plate seed single crystal is immersed in the melt obtained on the upper surface of the raw material mass for producing the thin-plate single crystal through lifting means, and a growth step of starting the growth of the single crystal from the lower surface of the thin-plate seed single crystal is carried out. In the growth step, the thin-plate seed single crystal in which the growth of the single crystal has started is pulled upward, and a continuous production step of continuously producing a thin-plate single crystal is carried out. It has at least In the melting step, When the thin-plate single crystal to be produced is a solid solution substance containing an additive, a composition of a liquid phase in equilibrium coexistence with its composition is first placed in a required amount on the upper surface of the raw material mass for producing the thin-plate single crystal. A method for producing a thin-plate single crystal is characterized in that.

19. In the melting step, The thin-plate single crystal manufacturing method according to claim 17 or 18, wherein the infrared rays irradiated from the infrared irradiation means are laser light.

20. In the melting step, The shape of the irradiation area of the laser light is a horizontally elongated hollow square shape, The thin-plate single crystal manufacturing method according to claim 19, wherein the laser light is irradiated so as to form the hollow square-shaped irradiation area on the peripheral area excluding the central part of the upper surface of the raw material mass for producing the thin-plate single crystal.

21. After the continuous production step, A winding step of winding the continuously produced thin-plate single crystal into a roll shape, The thin-plate single crystal manufacturing method according to any one of claims 17 to 20, further comprising.

22. In the growth step, The method for manufacturing a thin-plate single crystal according to any one of claims 17 to 21, characterized in that the lower surface of the thin-plate seed single crystal is immersed in the central portion of the melt on the surface of the upper surface of the melted raw material mass for manufacturing the thin-plate single crystal.

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