Apparatus for manufacturing thin plate-like single crystal, and thin plate-like single crystal

Abstract

[Problem] To provide: an apparatus for manufacturing a thin plate-like single crystal, which is capable of consecutively manufacturing high-quality thin plate-like single crystals even from a low-thermal-conductivity material; and a thin plate-like single crystal manufactured by said apparatus. [Solution] An apparatus for manufacturing a thin plate-like single crystal comprises: a laser light irradiation device which irradiates, with laser light, the upper face of a raw material block held by a holding unit to melt the surface on the upper face and form a melted region; and a lifting device which immerses a thin plate-like single-crystal seed in the melted region formed on the upper face and pulls the thin plate-like single-crystal seed upward. The apparatus for manufacturing a thin plate-like single crystal comprises a rotation device which rotates the holding unit. The laser light emitted from the laser light irradiation device is main linear laser light. The laser light irradiation device is configured such that the optical axis of the main linear laser light is included in a plane orthogonal to a rotation direction of the holding unit, or is configured such that the optical axis of the main linear laser light is included in a plane which is slightly inclined toward the single-crystal seed side with respect to the plane orthogonal to the rotation direction of the holding unit.

Description

Thin plate single crystal manufacturing apparatus and thin plate single crystal

[0001] The present invention relates to a thin plate single crystal manufacturing apparatus for manufacturing thin plate single crystals using raw material blocks made of various materials such as metals, semiconductors, and insulators, and to a thin plate single crystal manufactured by this thin plate single crystal manufacturing apparatus.

[0002] Typical single crystal materials currently in demand in the semiconductor IC and other device markets include silicon and ferroelectric materials such as lithium niobate and lithium tantalate. Most of these single crystal materials are provided to the device manufacturing industry in the form of wafers (thin single crystal plates). Most wafers are produced by using a method known as the pulling method, in which large, round rod-shaped single crystals measuring several hundred millimeters in diameter and several meters in length are produced in a crucible. These are then cut into thin plates approximately several hundred micrometers thick and polished.

[0003] Most of the single crystal materials currently available on the market are produced by the pulling method, but this method has the following inherent drawbacks.

[0004] The first drawback is the need to use a crucible to hold the raw material melt, which increases the cost of single crystal production if the crucible material is expensive. Also, the crucible material may be mixed into the single crystal product as an impurity or may form a solid solution, degrading the performance of the single crystal product.

[0005] The second drawback is that the pulling method is a unidirectional solidification method, and the concentration of useful additives in the resulting single crystal ingot is not uniform. To overcome this drawback, the double crucible method was developed, but there are no known examples of this method being successfully commercialized.

[0006] The main manufacturing method for semiconductor silicon single crystals, a typical single-crystal material, is the pulling method using a quartz crucible. Essentially, crucible materials are required to be non-reactive with the raw material melt and be usable up to temperatures approximately 100°C higher than the melting point of the raw material. However, quartz materials react with the silicon raw material melt to form silicon monoxide. Furthermore, quartz materials tend to soften at temperatures higher than approximately 1,000°C, and quartz crucibles have already softened to the point where they cannot stand on their own at temperatures near 1,450°C, the melting point of silicon. Therefore, it is extremely difficult to use them at temperatures approximately 100°C higher than the melting point.

[0007] As such, it is extremely inappropriate to use a quartz crucible as a crucible for producing silicon single crystals, and its use should be avoided in principle, but the reality is that quartz crucibles are used out of necessity because no other alternative materials have been found. As a result, the single crystal products contain various problems, as described below.

[0008] To produce single crystals using the pulling method, the raw material must be completely melted and then solidified. High-purity silicon raw material is produced using the Siemens process, and the raw material produced using this process contains a large amount of acicular single crystals. Acicular single crystals have high crystalline perfection, and it is known that melting them requires higher temperatures and longer times than melting ordinary powdered raw materials.

[0009] Although it is possible to melt needle-shaped silicon single crystals by maintaining the quartz crucible at a temperature close to the melting point of silicon for a long period of time, the quartz crucible generates silicon monoxide through a chemical reaction with the silicon melt. Although the reaction of the generated silicon monoxide stops when the amount reaches a level determined by the solubility, the silicon monoxide evaporates from the surface of the silicon melt, and the silicon monoxide generation reaction continues to compensate for the amount lost through the evaporation of silicon monoxide. The area of ​​the quartz crucible in contact with the liquid surface gradually wears away and becomes thinner, resulting in the development of holes.

[0010] For the above reasons, the pulling operation must be started even when a large amount of acicular single crystal remains in the raw material melt. In the case of silicon, the volume of the solid is larger than that of the melt, and the specific gravity of the solid is smaller than that of the melt, so the acicular single crystal gradually moves above the melt due to buoyancy.

[0011] These remaining needle-like single crystals are likely to adhere to the surface of the single crystal at the solid-liquid interface at the bottom of the single crystal being manufactured. At the site where the needle-like single crystals have adhered, there is little chance that the orientation of the single crystal being manufactured and the orientation of the attached needle-like single crystals will exactly match, resulting in a mismatch, and the growth of negative crystals formed at the facets will begin.

[0012] When the size of the negative crystals reaches a certain size, they continue to grow in the closing direction, and eventually become voids formed entirely by facets, remaining in the single crystal. The number of needle-shaped single crystals remaining in the melt gradually decreases, and as melting progresses, the size of the needle-shaped single crystals also decreases, and soon all the needle-shaped single crystals remaining in the raw material melt disappear, and the formation of negative crystals also stops.

[0013] The reason why a large number of voids are found in the initial growth portion of silicon single crystals produced by the pulling method, but gradually disappear, is due to the above reasons. The commonly held theory that "the voids observed in silicon single crystals are lattice vacancies that have moved through the single crystal due to temperature differences and accumulated in one place" is impossible to explain the mechanism by which tens of millions of vacancies accumulate in one place, and must be said to be an absurd and outrageous argument.

[0014] The problem with quartz crucibles, which will be discussed next, is that quartz reacts with molten silicon to produce silicon monoxide, and some of the silicon monoxide produced ends up being mixed into the silicon single crystal being produced as a solid solution.

[0015] This is the biggest problem with silicon single crystals produced by the current pulling method.

[0016] Quartz is silicon dioxide, and its chemical formula is SiO2. This SiO2 chemically reacts with molten silicon to produce silicon monoxide (SiO) as shown in the following formula 1:

[0017] The silicon monoxide produced is mixed into the silicon melt and forms a solid solution in the solidified single crystal. Therefore, strictly speaking, silicon single crystals produced by the pulling method should be called "silicon-silicon monoxide solid solution," and it should be noted that calling them high-purity silicon single crystals does not reflect the actual situation.

[0018] As described above, the single crystal product produced by melting high-purity silicon raw material in a quartz crucible and using the pulling method should more accurately be called a "silicon silicon monoxide solid solution," but in the following explanation it will be referred to as a "silicon single crystal."

[0019] The amount of silicon monoxide mixed into the silicon single crystal to form a solid solution gradually decreases as the temperature drops below about 1,000°C. As this amount of silicon monoxide decreases, the excess silicon monoxide precipitates in the solid. In other words, a large amount of silicon monoxide, which is a heterogeneous component, precipitates in the silicon single crystal solid formed by strong covalent bonds.

[0020] This phenomenon is common in naturally occurring minerals and is named "exsolution." Typical minerals that exhibit exsolution include luminous minerals such as star ruby, star sapphire, and cat's eye. The precipitated components generally precipitate along the plane with the widest interplanar spacing of the parent single crystal. In the case of silicon single crystals, they also precipitate along the (111) plane with the widest interplanar spacing.

[0021] If this exsolution of silicon monoxide occurs, the physical properties of the single crystal, such as its resistance, will fluctuate significantly. Furthermore, a large number of fine cracks will form around the exsolution site. When wet oxidation is performed, the silicon adjacent to the fine cracks will react with the oxidizing solution and be converted to oxide. The oxide is dissolved and removed by treatment with hydrofluoric acid, resulting in the formation of numerous grooves along the (111) plane after treatment with hydrofluoric acid.

[0022] This is the cause of a defect structure that appears in silicon-silicon monoxide solid solution single crystals called "oxidized induced stacking faults (OSFs)." To prevent this from occurring, the amount of silicon monoxide in solid solution must be kept below a trace amount that does not cause exsolution.

[0023] However, it is practically impossible to suppress the silicon monoxide content in silicon single crystals produced by the pulling method using a quartz crucible to such a small amount, and if one wishes to produce truly high-purity, high-quality silicon single crystals, there is no other way than to adopt a method other than the pulling method.

[0024] Furthermore, semiconductor silicon single crystals are used as P-type or N-type semiconductors by adding boron or phosphorus, but the amount of boron or phosphorus added in the single crystal ingot produced by the pulling method is not uniform, and the boron or phosphorus added is thin in the initial growth portion and gradually becomes denser as the growth proceeds. In particular, since the distribution coefficient of phosphorus in N-type silicon doped with phosphorus is small, about 0.35, when the growth has progressed to about half of the raw material melt, the phosphorus concentration in the product often becomes too dense and cannot meet specifications.

[0025] For this reason, efforts are being made to halt growth, remove the product, and then replenish the remaining raw material melt with the amount of raw material that was consumed before restarting growth of a second crystal.However, even with this, the optimal concentration portion in the product is limited, and the current situation is that the yield of single crystal products with the optimal composition that the device industry desires is low.

[0026] Silicon single crystals produced by the pulling method are generally considered to be dislocation-free single crystals with the highest purity and perfection ever produced by humankind. However, in reality, the concentration of additives is not uniform, and they contain exsolution structures that are much larger than minute defects such as dislocations and have a significant impact on physical properties.

[0027] Furthermore, when cutting a large round bar-shaped single crystal into thin plates, a large amount of cutting loss occurs, which results in multiple problems, such as wasting the expensive single crystal produced.

[0028] The cost of generating electricity from solar cells, which aim to make effective use of solar energy, remains higher than any other power generation method, including nuclear, hydroelectric, and thermal power generation. To reduce power generation costs, it is necessary to reduce the manufacturing costs of high-quality wafers, which are the main components, and to improve the solar conversion efficiency.

[0029] Instead of cutting and processing large single crystals produced by the pulling method to produce wafers, new manufacturing equipment and methods have been explored that can produce homogeneous thin single crystals with optimal additive concentrations from the start, thereby dramatically reducing the cost of wafer production.

[0030] A method called the Edge-defined Film-fed Growth (EFG) method has been developed as a method for producing thin-plate single crystal silicon, and a large amount of public funds have been invested in this method, mainly in the United States, with the aim of putting it into practical use.

[0031] However, in the case of silicon, a material that can withstand long-term stable use as the material for the raw material melt supply jig called a die, which is a main component of the EFG method, has not been found, and practical application has not been achieved. The only known practical examples of the EFG method are gallium oxide plates and sapphire plates that use iridium or molybdenum as dies.

[0032] In light of this situation, the present inventor has recently developed a new manufacturing device for producing large, thin plate-shaped single crystals. This device is capable of irradiating the upper surface of a raw material lump with a line-shaped laser beam and producing large, high-purity, thin plate-shaped single crystals from the melt obtained on the upper surface of the raw material lump. This device is of great significance.

[0033] This thin-plate single crystal manufacturing apparatus makes it possible to manufacture large, high-quality thin-plate single crystals with a width of 300 mm or more that are homogeneous in dopant concentration and free of impurities, which was previously impossible to produce using conventional pulling methods or radio-frequency floating zone methods. This allows for a dramatic reduction in the manufacturing costs of high-quality, large-diameter wafers (Patent Document 1).

[0034] Japanese Patent Application Laid-Open No. 2023-025811

[0035] This thin plate single crystal manufacturing apparatus continuously produces thin plate single crystals by irradiating the upper surface of a raw material lump with a line-shaped laser beam to form a molten region on the upper surface of the raw material lump, and then immersing a thin plate-shaped seed single crystal in this region and pulling it up. This thin plate single crystal manufacturing apparatus does not require the use of a crucible to hold the raw material melt, and can produce thin plate single crystals with a homogeneous concentration of additives. It is an innovative apparatus that can produce thin plate single crystals with high purity, high quality, and low cost.

[0036] However, it has been found that depending on the single crystal material, it may be difficult to manufacture a thin plate-shaped single crystal.

[0037] First, in the thin plate single crystal manufacturing equipment, a shielding plate is used to prevent the reflected laser light from hitting the thin plate single crystal during manufacturing and heating the thin plate single crystal.However, if the single crystal material is a highly thermally conductive material such as a metal material, a melting zone of a size taking into account the placement of the shielding plate can be formed on the upper surface of the raw material block without any problems.

[0038] However, in the case of materials with low thermal conductivity, such as oxides, although a melted region can be formed in the area irradiated with laser light, the melted region does not spread to areas other than the irradiated area that are not irradiated with laser light, and it is difficult to ensure a melted region of a size that takes into account the placement of the shielding plate, which can make it difficult to produce thin plate-shaped single crystals.

[0039] That is, as shown in Fig. 8(a), laser beams 112a and 112b are irradiated from an oblique direction onto upper surface 102 of raw material lump 100 via two laser beam irradiators (not shown), thereby forming melted regions 120a and 120b. When raw material lump 100 is made of a material with high thermal conductivity, such as a metal material, melted regions 120a and 120b formed at the irradiated portions of raw material lump 100 with laser beams 112a and 112b expand as the intensity of laser beams 112a and 112b increases, due to a rise in the surrounding temperature caused by thermal conduction, as shown in Fig. 8(b).

[0040] When the two melted regions 120a and 120b each expand further, the two melted regions 120a and 120b merge into one large melted region 120. This allows the melted region 120 to be large enough to easily accommodate the placement of the shielding plates 140a and 140b, as shown in Figure 8(c).

[0041] In addition to the irradiation with the laser beams 112a and 112b, spot-shaped laser beams 116a and 116b are irradiated onto both ends in the width direction of the insertion portion of the seed single crystal 130 on the upper surface 102 of the melted region 120, thereby pulling the seed single crystal 130 upward and regulating the expansion of the width of the thin plate-shaped single crystal 134, thereby making it possible to stably produce the thin plate-shaped single crystal 134 from the center portion of the melted region 120 via the joint portion 132. In the figure, reference numeral 110a denotes the exit port of the laser beam 112a, reference numeral 110b denotes the exit port of the laser beam 112b, reference numeral 114a denotes the exit port of the spot-shaped laser beam 116a, and reference numeral 114b denotes the exit port of the spot-shaped laser beam 116b.

[0042] On the other hand, as shown in FIG. 9( a), in the case of a material with low thermal conductivity such as an oxide, even if the irradiation intensity of the laser beams 112 a and 112 b is increased, the spread of the two melted regions 120 a and 120 b is small, and it is difficult to form melted regions large enough to enable the installation of the shielding plates 140 a and 140 b.

[0043] Therefore, if the left and right distance is narrowed in the region of the upper surface 102 of the raw material lump 100 where the laser beams 112a, 112b are incident, as shown in Figure 9(b), the left and right molten regions 120a, 120b can expand and connect to form a single molten region 120. However, even if a single connected molten region 120 is forcibly formed in this way, the formed molten region 120 is small, and it is therefore difficult to insert shielding plates 140a, 140b and a seed single crystal 130 to produce a stable thin plate-shaped single crystal 134, as shown in Figure 9(c).

[0044] In addition, in Figure 9(a), if the irradiation intensity of the laser beams 112a and 112b is further increased to form melted regions 120a and 120b of the required size, evaporation becomes more intense from the areas of the upper surface 102 of the raw material block 100 where the laser beams 112a and 112b are irradiating, and even with this method, it may be difficult to stably produce a thin plate-shaped single crystal 134.

[0045] Therefore, the present invention aims to provide a thin plate single crystal manufacturing apparatus that can continuously produce high-quality, large thin plate single crystals even from materials with low thermal conductivity such as oxides, and thin plate single crystals manufactured using this thin plate single crystal manufacturing apparatus.

[0046] The present invention has been invented to solve the problems of the prior art described above, and provides an apparatus for producing a thin plate-shaped single crystal comprising at least: a holding section for holding a raw material lump in an upright position; a laser light irradiating device for irradiating a laser light onto an upper side of the raw material lump held by the holding section, thereby melting the surface of the upper side and forming a melted region; and a lifting device for immersing a thin plate-shaped seed single crystal into the melted region formed on the upper side of the raw material lump and lifting the seed single crystal upward from the immersed state, wherein the seed single crystal is immersed in the melting region via the lifting device, thereby starting single crystal growth from the lower side of the immersed seed single crystal, and the seed single crystal is further lifted upward via the lifting device, thereby continuously producing a thin plate-shaped single crystal, the apparatus for producing a thin plate-shaped single crystal comprising: a rotation device for rotating the holding section; and the laser light irradiating device, wherein the laser light irradiated from the laser light irradiating device is a main line-shaped laser light, The optical axis of the main line-shaped laser beam is configured to be included within a plane perpendicular to the rotation direction of the holding part rotated by the rotating device, or the optical axis of the main line-shaped laser beam is configured to be included within a plane that is slightly inclined toward the seed single crystal with respect to the plane perpendicular to the rotation direction of the holding part rotated by the rotating device.

[0047] With this configuration, the light reflected from the surface of the melt formed by irradiating the raw material lump with the main line-shaped laser beam will not be irradiated onto the thin plate-shaped single crystal being produced.

[0048] In addition, when attempting to produce a large, thin plate-shaped single crystal, it is necessary to form a large molten region, and the output of the laser light irradiation device (for example, a laser oscillation device) used is also required to be increased.

[0049] If it is difficult to manufacture such a high-power laser light irradiation device, multiple low-power main line-shaped laser beams can be irradiated onto the same position (irradiation area) on the upper surface of the raw material block from both the outer and inner sides of the raw material block (in other words, from one side and the other side in the width direction of the thin plate-shaped single crystal to be manufactured), thereby forming a large melting area equivalent to that obtained when a high-power laser light irradiation device is used.

[0050] When forming a large melted region by irradiating a low-power main linear laser beam from both the outer and inner sides of the raw material block (in other words, from both sides in the width direction of the thin plate-shaped single crystal being produced), it is necessary to arrange the laser beam so that the reflected light from the melt surface of the main linear laser beam irradiated from the outer side does not hit the exit port of the main linear laser beam located on the inner side.

[0051] The reason is that if the reflected light irradiates the emission port of the main linear laser light on the inner periphery side, it may cause fluctuations in the output value or may even be destroyed.

[0052] To avoid such a situation, the optical axis of the main linear laser beam is included within a plane that is slightly inclined toward the seed single crystal (thin plate-shaped single crystal), so that the reflected light from the melt surface of the main linear laser beam irradiated from the exit port located on the outer periphery can pass through while avoiding the exit port of the main linear laser beam located on the inner periphery.

[0053] In this case, the tilt angle of the main linear laser beam arranged on the outer periphery side may be adjusted in accordance with the size and position of the exit port of the main linear laser beam arranged on the inner periphery side, and is not particularly limited, and the tilt angle is a maximum of 10 degrees, preferably a maximum of 7 degrees, and more preferably a maximum of 5 degrees. Within this tilt angle, the reflected light can pass through while avoiding the exit port of the main linear laser beam arranged on the inner periphery side.

[0054] Furthermore, the inclination angle can be increased by moving the position (irradiation area) where the main line-shaped laser light is irradiated away from the position of the seed single crystal (thin plate-shaped single crystal); however, if the position (irradiation area) where the main line-shaped laser light is irradiated away from the position of the seed single crystal (thin plate-shaped single crystal), the temperature of the melt in the melting area decreases as it moves away from the irradiation area, and therefore the temperature of the melt at the insertion position of the seed single crystal will decrease.

[0055] Therefore, in order to stably produce a thin plate single crystal with a large tilt angle, it is necessary to increase the temperature of the position (irradiation area) irradiated with the main line-shaped laser beam, which may cause inconvenience such as intensified evaporation from the melt. Therefore, in reality, it is desirable to limit the tilt angle to a maximum of about 5 degrees.

[0056] Furthermore, with this configuration, even if the raw material block is made of a material with low thermal conductivity such as an oxide, a molten area of ​​the desired size can be formed on the upper surface of the raw material block without using a shielding plate as in the conventional method, thereby making it possible to continuously produce high-quality, large, thin-plate-shaped single crystals.

[0057] Furthermore, since there is no need to use a shielding plate as in the conventional method, the size of the melting region can be made smaller with the thin plate single crystal manufacturing apparatus of the present invention than the size of the melting region that was previously required for stable production of thin plate single crystals.

[0058] Furthermore, while thin plate-shaped single crystals have conventionally been produced using cubic raw material blocks, the present invention makes it possible to more reliably produce thin plate-shaped single crystals continuously by using, for example, cylindrical raw material blocks.

[0059] In other words, by rotating the holding portion with a rotating device, the main linear laser light can be irradiated onto the upper surface of the cylindrical raw material block to form a melted area of ​​sufficient size to produce a thin plate-shaped single crystal, thereby enabling the safe and continuous production of long thin plate-shaped single crystals.

[0060] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention forms a melted region by irradiating a main linear laser beam onto the upper surface of a high-purity raw material block. Since the size of the melted region formed is constant, the so-called solvent migration method is automatically applied while the raw material block continues to melt and solidify into a single crystal, and the concentration of additives in the single crystal product becomes homogeneous.

[0061] Furthermore, by increasing the size of the raw material block and irradiating it with a corresponding main line-shaped laser beam, it is easy to increase the width of the resulting thin plate-shaped single crystal, and it is also easy to produce a thin plate-shaped single crystal with a width of, for example, 1 m.

[0062] Furthermore, since it is easy to form multiple molten zones on the upper surface of the cylindrical raw material mass and produce thin plate-shaped single crystals from each of the formed molten zones, it becomes possible to produce multiple thin plate-shaped single crystals, thereby achieving a dramatic reduction in wafer production costs.

[0063] Furthermore, in the thin plate single crystal manufacturing apparatus of the present invention, the optical axis of the main linear laser beam is contained in a plane perpendicular to the rotation direction of the holder, or is contained in a plane slightly inclined toward the seed single crystal with respect to the plane perpendicular to the rotation direction of the holder, so that when the main linear laser beam is irradiated onto the upper surface of the raw material lump to form a melted region, the light of the main linear laser beam irradiated onto the upper surface of the raw material lump reflected from the melt surface of the melted region formed on the upper surface of the raw material lump does not strike the thin plate single crystal being manufactured. This eliminates the need to install a shielding plate as in the conventional method, and enables reliable continuous manufacturing of thin plate single crystals without unnecessarily widening the melted region.

[0064] The invention of this thin plate single crystal manufacturing apparatus means that the long-desired production of high-quality, large thin plate single crystals with homogeneous composition has now been realized, and its contribution to related industries will be immeasurable.

[0065] The thin plate single crystal manufacturing apparatus of the present invention is characterized in that the raw material lump is a cylindrical raw material lump.

[0066] If the raw material block is cylindrical in shape, a melting zone of the size required to produce a thin plate-shaped single crystal can be formed as the raw material block is rotated by the rotating device, and the shape of the melting zone of that size can be continuously maintained, making it possible to stably produce ultra-long thin plate-shaped single crystals.

[0067] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention is characterized in that, when the raw material block is held in the holding section, the main line-shaped laser light is irradiated onto the upper side of the raw material block from diagonally above the raw material block.

[0068] In this way, the laser beam irradiation device that irradiates the main line-shaped laser beam does not get in the way of the thin plate-shaped single crystal being produced, so that thin plate-shaped single crystal can be produced continuously.

[0069] Furthermore, the reflected light of the main linear laser light from the surface of the melt is located in a plane perpendicular to the upper surface of the raw material lump, or in a direction away from the seed single crystal, just like the irradiated main linear laser light, so the reflected light does not hit the thin plate-shaped single crystal being produced, and thin plate-shaped single crystals can be produced with high yield.

[0070] Furthermore, when producing a large thin plate single crystal, a high-power laser beam irradiation device (e.g., a laser oscillator) is required, but in reality, it may be difficult to use such a high-power laser beam irradiation device. Therefore, when using multiple low- or medium-power laser beam irradiation devices to ensure the required irradiation amount and producing a large thin plate single crystal, if the emission ports of multiple main line-shaped laser beams are arranged biasedly, for example, toward the outer periphery of the raw material ingot (in other words, one side in the width direction of the thin plate single crystal), spatial cramping may occur.

[0071] In such a case, it is sufficient to arrange the exit ports of the main linear laser beam on both the outer and inner sides of the raw material lump (in other words, on both sides in the width direction of the thin plate-shaped single crystal to be produced). When the exit ports of the main linear laser beam are arranged on both the outer and inner sides of the raw material lump (in other words, on both sides in the width direction of the thin plate-shaped single crystal to be produced), the optical axis of the main linear laser beam should be included in a plane slightly inclined toward the seed single crystal (thin plate-shaped single crystal) so as to prevent the reflected light of the main linear laser beam irradiated from the outer side from being reflected by the melt surface of the melted region formed on the upper side of the raw material lump from directly hitting another exit port of the main linear laser beam arranged on the inner side. This allows for stable production of large thin plate-shaped single crystals.

[0072] Furthermore, as will be described later, if a secondary line-shaped laser beam is irradiated onto the upper surface of the raw material block from diagonally above the block at an appropriate interval in addition to the main line-shaped laser beam, a soaking zone can be formed within the formed melting zone, and if a seed single crystal is immersed in this soaking zone to produce a thin plate-shaped single crystal, thin plate-shaped single crystals can be produced continuously and stably with a high yield.

[0073] The thin plate single crystal manufacturing apparatus of the present invention is characterized in that a preheating device for preheating the raw material ingot is disposed around the holding section.

[0074] By providing such a preheating device, the raw material lump can be preheated to near its melting point, thereby significantly reducing the irradiation dose of the main linear laser beam and reducing the temperature fluctuation range of the raw material lump when the raw material lump is irradiated with the main linear laser beam to form a melted region, thereby preventing undesirable phenomena such as cracking of the raw material lump that have conventionally occurred due to sudden temperature fluctuations.

[0075] The thin plate single crystal manufacturing apparatus of the present invention is characterized by comprising a vertical movement device for moving the holding part in the vertical direction.

[0076] The vertical movement device compensates for the lowering of the upper surface of the raw material lump during the production of the thin plate single crystal, thereby maintaining the vertical position of the melted region on the upper surface of the raw material lump constant. This makes it possible to efficiently and continuously produce high-quality, ultra-long thin plate single crystals with a homogeneous composition while maintaining constant irradiation conditions, such as the irradiation angle of the main linear laser beam irradiated from the laser beam irradiation device.

[0077] The thin plate single crystal manufacturing apparatus of the present invention is characterized in that the lifting device is a winding and storing device that continuously winds up the manufactured thin plate single crystal in a roll and stores it.

[0078] Such a winding and storage device can reliably wind up continuously produced thin plate single crystals without increasing the size of the thin plate single crystal production apparatus more than necessary. Furthermore, if the produced thin plate single crystals are in the form of a roll, they can be easily transported during shipping, improving handleability.

[0079] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention is characterized in that the lifting device is a cutting and storing device that pulls up the thin plate single crystal being continuously manufactured, cuts it into predetermined lengths, and stores it.

[0080] With this cutting and storage device, the thin plate single crystals obtained can be cut into predetermined lengths, for example, every 2 m, and stored without interrupting the continuous production of ultra-long thin plate single crystals.

[0081] Methods for cutting a continuously pulled thin plate single crystal without interrupting the pulling process include, for example, a method of cutting by irradiating a line-shaped laser beam, and a method of melting and cutting the thin plate single crystal by bringing a rod of high-melting point material heated to a temperature above the melting point of silicon into contact with the thin plate single crystal.

[0082] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention further comprises a secondary laser light irradiating device that assists the laser light irradiating device, wherein the laser light irradiated from the secondary laser light irradiating device is a secondary line-shaped laser light, and wherein the optical axis of the secondary line-shaped laser light is included within a plane perpendicular to the rotation direction of the holding part rotated by the rotating device, or wherein the optical axis of the secondary line-shaped laser light is included within a plane that is slightly inclined toward the seed single crystal with respect to the plane perpendicular to the rotation direction of the holding part rotated by the rotating device.

[0083] If a secondary laser beam irradiator that assists the laser beam irradiator is further provided, a soaking zone can be formed within the melting zone formed on the upper surface of the raw material lump by the irradiated secondary linear laser beam. This allows for stable and continuous production of high-quality, large, thin plate-shaped single crystals. As with the above-described laser beam irradiator, a high-power secondary laser beam irradiator (e.g., a laser oscillator) is required for producing large, thin plate-shaped single crystals. However, if it is difficult to manufacture such a high-power secondary laser beam irradiator, multiple low-power secondary linear laser beams can be irradiated from both the outer and inner sides of the raw material lump (in other words, from both sides in the width direction of the thin plate-shaped single crystal) to the same position (irradiation zone) on the upper surface of the raw material lump to form a large melting zone.

[0084] In this way, when forming a large melted region by irradiating low-power sub-linear laser light from both the outer and inner sides of the raw material block (in other words, from both sides in the width direction of the thin plate-shaped single crystal being produced), the sub-linear laser light should be positioned so that the reflected light from the melt surface of the sub-linear laser light irradiated from the outer side does not hit the exit port of the sub-linear laser light positioned on the inner side.

[0085] The inclination angle of the secondary linear laser light arranged on the outer periphery side can be adjusted to match the size and position of the exit port of the secondary linear laser light arranged on the inner periphery side, and is not particularly limited.The inclination angle is a maximum of 10 degrees, preferably a maximum of 7 degrees, and more preferably a maximum of 5 degrees.Within this inclination angle, the reflected light can pass through, avoiding the exit port of the secondary linear laser light arranged on the inner periphery side.

[0086] Furthermore, the inclination angle can be increased by moving the position (irradiation area) where the secondary line-shaped laser light is irradiated away from the position of the seed single crystal (thin plate-shaped single crystal); however, if the position (irradiation area) where the secondary line-shaped laser light is irradiated away from the position of the seed single crystal (thin plate-shaped single crystal), the temperature of the melt in the melting area decreases as it moves away from the irradiation area, and therefore the temperature of the melt at the insertion position of the seed single crystal will decrease.

[0087] Therefore, in order to stably produce a thin plate single crystal with a large tilt angle, it is necessary to increase the temperature of the position (irradiation area) irradiated with the sub-line laser beam, which may cause inconvenience such as intensified evaporation from the melt. Therefore, in reality, it is desirable to limit the tilt angle to a maximum of about 5 degrees.

[0088] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention is characterized in that, when the raw material block is held in the holding section, the secondary line-shaped laser light is irradiated onto the upper side of the raw material block from diagonally above the raw material block.

[0089] In this way, the secondary laser beam irradiating device for irradiating the secondary line-shaped laser beam does not get in the way of the thin plate-shaped single crystal being produced, so that the thin plate-shaped single crystal can be produced continuously.

[0090] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention is characterized in that, with a seed single crystal immersed in the melting zone of the raw material lump as a boundary, a main line-shaped laser beam is irradiated on one side of the seed single crystal in the thickness direction, and a sub-line-shaped laser beam is irradiated on the other side of the seed single crystal in the thickness direction.

[0091] With this configuration, a soaking zone can be formed within the melting zone by combining the main line-shaped laser beam and the sub line-shaped laser beam, and from the soaking zone formed, high-quality, large-sized thin plate single crystals can be stably and continuously produced.

[0092] The thin plate single crystal manufacturing apparatus of the present invention is characterized in that a reflected light shielding cylinder is provided at the center of the holding part rotated by the rotating device.

[0093] The provision of such a reflected light shielding cylinder makes it possible to efficiently block the laser light (reflected light) reflected by the surface of the molten region formed when the main linear laser light is irradiated onto the upper surface of the cylindrical raw material lump from outside the outer periphery of the cylindrical raw material lump, thereby facilitating the stable production of thin plate single crystals over long periods of time.

[0094] The thin plate single crystal manufacturing apparatus of the present invention is characterized in that the seed single crystal has a facet.

[0095] If the seed single crystal inserted into the melting zone formed on the upper surface of the cylindrical raw material mass is a seed single crystal having a facet surface, and a thin plate-shaped single crystal is formed on the facet surface of this seed single crystal, a thin plate-shaped single crystal having a crystallographically flat plane can be produced.

[0096] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention is characterized in that the plane that includes the optical axis of the main line-shaped laser light and is slightly inclined toward the seed single crystal is inclined by a maximum of 10 degrees toward the seed single crystal with respect to a plane perpendicular to the rotation direction of the holding part.

[0097] Furthermore, the thin plate single crystal manufacturing apparatus of the present invention is characterized in that the plane that includes the optical axis of the secondary line-shaped laser beam and is slightly inclined toward the seed single crystal is inclined by a maximum of 10 degrees toward the seed single crystal with respect to a plane perpendicular to the rotation direction of the holding part.

[0098] The inclination angle of the plane slightly inclined toward the seed single crystal, which includes the optical axes of the main linear laser beam and the sub linear laser beam arranged on the outer periphery side, can be adjusted to match the size and position of the exit ports of the main linear laser beam and the sub linear laser beam arranged on the inner periphery side, and is not particularly limited.

[0099] The inclination angle is a maximum of 10 degrees, preferably a maximum of 7 degrees, and more preferably a maximum of 5 degrees, and within this inclination angle, the reflected light can pass through while avoiding the exit ports of the main line-shaped laser light and the sub line-shaped laser light located on the inner side.

[0100] Furthermore, the inclination angle can be increased by moving the position (irradiation area) where the main line-shaped laser light and the sub line-shaped laser light are irradiated away from the position of the seed single crystal (thin plate-shaped single crystal); however, if the position (irradiation area) where the main line-shaped laser light and the sub line-shaped laser light are irradiated away from the position of the seed single crystal (thin plate-shaped single crystal), the temperature of the melt in the melting area decreases as it moves away from the irradiation area, and therefore the temperature of the melt at the insertion position of the seed single crystal will decrease.

[0101] Therefore, in order to stably produce a thin plate single crystal with a large tilt angle, it is necessary to increase the temperature of the position (irradiation area) where the main line-shaped laser beam and the sub line-shaped laser beam are irradiated, which may cause inconvenience such as intensified evaporation from the melt. Therefore, in reality, it is desirable to keep the tilt angle at a maximum of about 5 degrees.

[0102] The thin plate single crystal of the present invention is characterized by being produced by the above-mentioned thin plate single crystal production apparatus.

[0103] Thin plate single crystals produced by such thin plate single crystal production equipment have crystallographically flat surfaces and are of high quality.

[0104] The thin plate-like single crystal of the present invention is characterized in that the thickness of the thin plate-like single crystal is in the range of 30 to 5,000 μm.

[0105] Thus, thin plate-like single crystals having a thickness in the range of 30 to 5,000 μm, more preferably in the range of 30 to 2,500 μm, and even more preferably in the range of 30 to 1,500 μm, can be continuously produced and long lengths can be achieved.

[0106] The thin plate single crystal manufacturing apparatus of the present invention can be used with raw material blocks made of various materials such as metals, semiconductors, and insulators, especially with materials with low thermal conductivity such as oxides, without the need for a shielding plate as in the past. By configuring the rotating raw material block so that the optical axis of the main linear laser beam is contained within a plane perpendicular to the rotation direction of the raw material block, or so that the optical axis of the main linear laser beam is contained within a plane slightly inclined toward the seed single crystal relative to the plane perpendicular to the rotation direction of the raw material block, a melted zone of desired size can be formed. Furthermore, by irradiating the formed melted zone with a secondary linear laser beam, a soaked zone can be formed within the melted zone. By pulling the thin plate single crystal from this soaked zone, high-purity, high-quality, and homogeneous thin plate single crystals can be continuously produced inexpensively and with good operability.

[0107] Fig. 1 is a schematic diagram of a thin plate single crystal manufacturing apparatus according to an embodiment of the present invention, with Fig. 1(a) being a schematic front view and Fig. 1(b) being a schematic side view of part A in Fig. 1(a). Fig. 2 is an explanatory diagram for explaining the situation when a melted region is formed by irradiating a main line-shaped laser beam and a thin plate single crystal is manufactured in the thin plate single crystal manufacturing apparatus of the present invention. Fig. 3 is an explanatory diagram for explaining the situation when a melted region formed by irradiating a main line-shaped laser beam is irradiated with a sub-line-shaped laser beam to form a soaked region and a thin plate single crystal is stably manufactured in the thin plate single crystal manufacturing apparatus of the present invention. FIG. 4 is an explanatory diagram for producing a thin plate-shaped single crystal by inserting a seed thin plate-shaped single crystal into a soaking zone of a melting zone formed by irradiating a main linear laser beam and a sub-linear laser beam. FIG. 4( a) is an explanatory diagram for producing a single thin plate-shaped single crystal 52, FIG. 4( b) is an explanatory diagram for simultaneously producing two thin plate-shaped single crystals 52, FIG. 4( c) is an explanatory diagram for simultaneously producing four thin plate-shaped single crystals 52, and FIG. 4( d) is an explanatory diagram for simultaneously producing eight thin plate-shaped single crystals 52. FIG. 5 is an explanatory diagram for explaining the optical paths of the main linear laser beam irradiated from the laser beam irradiation device and the reflected light reflected by the formed liquid surface. FIG. 6 is an explanatory diagram for explaining a state in which the optical axis of the main linear laser beam is included in a plane slightly inclined toward the seed single crystal with respect to a plane perpendicular to the rotation direction of the holder. FIG. 7 is a schematic diagram showing another embodiment of the lifting device. Fig. 8 is a schematic diagram showing the steps from the formation of a melted region on the upper surface of a raw material lump made of a material with high thermal conductivity to the production of a thin plate-shaped single crystal in a conventional thin plate-shaped single crystal manufacturing apparatus. Fig. 9 is a schematic diagram showing the steps from the formation of a melted region on the upper surface of a raw material lump made of a material with low thermal conductivity to the production of a thin plate-shaped single crystal in a conventional thin plate-shaped single crystal manufacturing apparatus.

[0108] The thin plate single crystal manufacturing apparatus of the present invention will be described in more detail below with reference to the drawings.

[0109] The thin plate single crystal manufacturing apparatus of the present invention is capable of continuously and inexpensively manufacturing high-quality, large thin plate single crystals, even from materials with low thermal conductivity such as oxides. <Thin Plate Single Crystal Manufacturing Apparatus 10> As shown in Figures 1(a) and 1(b), the thin plate single crystal manufacturing apparatus 10 of the present invention comprises a chamber 20 and a holding section 30 disposed therein, and a raw material lump (in this embodiment, a cylindrical raw material lump 60) for manufacturing the thin plate single crystal is held in an upright position in this holding section 30.

[0110] A laser beam irradiation device (not shown) is provided outside the chamber 20 for irradiating the upper side surface 62 of the cylindrical lump of raw material 60 with the main line-shaped laser beam 12 to melt the surface of the upper side surface 62 and obtain a melted region 90. Reference numeral 32 denotes an exit port of the main line-shaped laser beam 12.

[0111] Furthermore, a secondary laser beam irradiating device (not shown) is provided outside the chamber 20 for irradiating the melted region 90 formed by the irradiation of the main line-shaped laser beam 12 with a secondary line-shaped laser beam 14 to form a soaked heat region 91. Reference numeral 36 denotes an exit port of the secondary line-shaped laser beam 14.

[0112] The main line-shaped laser beam 12 emitted from the exit port 32 and the sub line-shaped laser beam 14 emitted from the exit port 36 are configured to be directly incident into the chamber 20 through a window 22 provided in the side of the chamber 20, but they may be incident in any manner into the chamber 20. For example, the main line-shaped laser beam 12 emitted from the exit port 32 and the sub line-shaped laser beam 14 emitted from the exit port 36 may be incident into the chamber 20 through a window 22 provided in the side of the chamber 20 via a reflecting mirror (not shown).

[0113] Furthermore, in the thin plate single crystal manufacturing apparatus 10 of the present invention, the holder 30 that holds the cylindrical raw material lump 60 is provided with a rotation device 40. The rotation device 40 has a shaft 46 attached to a stand 42 connected to the holder 30, and is configured so that the holder 30 rotates when the shaft 46 is rotated.

[0114] The speed and direction of rotation of holding unit 30 by rotation device 40 can be controlled by control unit 48. Shaft 46 of rotation device 40 also functions as an up-and-down movement device 86 that moves holding unit 30 up and down, so that when thin plate-shaped single crystals 52 are continuously produced by irradiating upper surface 62 of cylindrical raw material lump 60 with main linear laser beam 12 to form melted zone 90, then irradiating this melted zone 90 with sub linear laser beam 14 to form soaking zone 91, and immersing thin plate-shaped seed single crystal 50 in this soaking zone 91 and pulling it up, even if the height of melted zone 90 gradually changes, the vertical position of melted zone 90 can always be kept constant by moving cylindrical raw material lump 60 up and down.

[0115] The rotating device 40 is not particularly limited as long as it is unlikely to vibrate during rotation, the rotation speed can be set within the range of at least 0.01 to 60 rpm, the rotation direction can be switched, and the melt formed in the melting area 90 on the upper surface 62 of the cylindrical raw material lump 60 does not spill out from the upper surface 62, and a known electric motor or the like can be used.

[0116] Furthermore, a preheating device 70 is arranged around the holding section 30 (in this embodiment, located to the side and below the cylindrical raw material block 60 when the cylindrical raw material block 60 is held in the holding section 30) to preheat the cylindrical raw material block 60 held in the holding section 30.

[0117] When melting the cylindrical lump of raw material 60 , it is preferable to preheat the cylindrical lump of raw material 60 to near its melting point using this preheating device 70 before irradiating it with the main line-shaped laser beam 12 .

[0118] This preheating allows a significant reduction in the irradiation dose of the main linear laser beam 12, thereby reducing manufacturing costs. Furthermore, when the cylindrical lump of raw material 60 is irradiated with the main linear laser beam 12 to melt it, the temperature fluctuation range of the cylindrical lump of raw material 60 can be reduced. This makes it possible to prevent undesirable phenomena such as cracks occurring in the cylindrical lump of raw material 60 due to sudden temperature fluctuations.

[0119] By maintaining a uniform temperature throughout the cylindrical raw material block 60 using the preheating device 70, the shape of the molten region 90 formed by irradiation with the main line-shaped laser beam 12 can be maintained in an optimal shape for producing the thin plate-shaped single crystal 52.

[0120] Such a preheating device 70 may be a resistance heating furnace using materials such as silicon, carbon, molybdenum, etc. Also, high frequency induction heating, infrared irradiation, etc. may be used.

[0121] Furthermore, above the chamber 20, there is provided an elevating device 80 which immerses the underside of the seed single crystal 50 in the soaking zone 91, pulls the seed single crystal 50 upward from the immersed state, and further continuously pulls up the produced thin plate-like single crystal 52 together with the seed single crystal 50. In the figure, reference numeral 54 denotes the joint between the seed single crystal 50 and the thin plate-like single crystal 52.

[0122] Any type of lifting device 80 may be used, but for example, a winding and storage device 82 can be used which continuously winds up and stores the thin plate-shaped single crystal 52 manufactured together with the thin plate-shaped seed single crystal 50 via the joint 54 in a roll shape.

[0123] The winding and storage device 82 has a winding reel 84 that continuously winds up and stores the produced thin plate-like single crystal 52, and a rotating device 83 that rotates the winding reel 84. In the figure, reference numeral 85 denotes a rotating roller that serves as a guide when the thin plate-like single crystal 52 is continuously wound onto the winding reel 84. With this winding and storage device 82, when the produced thin plate-like single crystal 52 has a thickness of several hundred μm, it is possible to continuously wind up a long thin plate-like single crystal 52 reaching a length of several kilometers.

[0124] In the thin plate single crystal manufacturing apparatus 10 of the present invention, it is preferable that the optical axes of the main linear laser beam 12 and the secondary linear laser beam 14 are included in a plane perpendicular to the rotation direction of the holding portion 30 rotated by the rotation device 40, and that the main linear laser beam 12 and the secondary linear laser beam 14 are irradiated onto the upper surface 62 of the cylindrical raw material block 60 from diagonally above in a plane perpendicular to the upper surface 62 of the cylindrical raw material block 60.

[0125] Alternatively, as described below, it is preferable that the optical axes of the main linear laser beam 12 and the sub-linear laser beam 14 are included within a plane that is slightly inclined toward the seed single crystal 50 with respect to a plane perpendicular to the rotation direction of the holding portion 30 rotated by the rotating device 40, and that the main linear laser beam 12 and the sub-linear laser beam 14 are irradiated onto the upper surface 62 of the cylindrical raw material block 60 from diagonally above within a plane perpendicular to the upper surface 62 of the cylindrical raw material block 60.

[0126] In this embodiment, since the holding unit 30 is rotated by the rotation device 40, it is preferable to use a cylindrical raw material lump (cylindrical raw material lump 60).

[0127] When a cylindrical lump of raw material 60 is used as in this embodiment, it is preferable to provide a reflected light shielding cylinder 34 in the center of the cylindrical lump of raw material 60 so that the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 are irradiated onto a desired range on the upper surface 62 of the cylindrical lump of raw material 60. This reflected light shielding cylinder 34 is preferably located directly above the shaft 46.

[0128] Next, the formation of the molten region 90 on the upper surface 62 of the cylindrical raw material lump 60 using the thin plate single crystal manufacturing apparatus 10 of the present invention will be described.

[0129] 2(a) and 2(b), a melted region 90 can be formed by irradiating the upper surface 62 of a cylindrical lump of raw material 60 with the main linear laser beam 12. Furthermore, as shown in FIGS. 3(a) and 3(b), a soaking region 91 can be formed within the melted region 90 by irradiating the melted region 90 obtained by irradiating the main linear laser beam 12 with the sub linear laser beam 14.

[0130] At this time, when the cylindrical lump of raw material 60 is slowly rotated (counterclockwise in this embodiment) by the rotating device 40, the melted region 90 expands in the direction of rotation.

[0131] The size of the expanding melted region 90 depends on the irradiation intensity of the main line-shaped laser beam 12, the rotation speed of the cylindrical lump of raw material 60, and the temperature of the cylindrical lump of raw material 60. As shown in Figures 3(a) and 3(b), a seed single crystal 50 is inserted into a soaking region 91 formed within the formed melted region 90 by irradiating the sub line-shaped laser beam 14, and the thin plate-shaped single crystal 52 is pulled upward via a joint 54 while growing, thereby producing a long thin plate-shaped single crystal 52.

[0132] The thin plate single crystal manufacturing apparatus 10 of this embodiment shown in Figures 1 to 3 is configured to continuously manufacture one thin plate single crystal 52 as shown in Figure 4(a), but it may also be configured to simultaneously manufacture two thin plate single crystals 52 as shown in Figure 4(b), four thin plate single crystals 52 as shown in Figure 4(c), or eight thin plate single crystals 52 as shown in Figure 4(d).

[0133] That is, as shown in Figures 4(b) to 4(d), if multiple manufacturing units for thin plate-shaped single crystals 52, each of which is a set of a laser light irradiation device, a sub-line-shaped laser light irradiation device, and an elevating device 80, are provided so that multiple thin plate-shaped single crystals 52 can be pulled up simultaneously, it becomes possible to manufacture multiple thin plate-shaped single crystals 52 simultaneously, thereby significantly reducing the manufacturing cost of the thin plate-shaped single crystals 52.

[0134] There is no particular limit to the number of thin plate-shaped single crystals 52 that can be simultaneously produced, and by arranging the production units required to produce one thin plate-shaped single crystal 52 in the number of pieces that can be spatially arranged, it is possible to simultaneously produce a plurality of thin plate-shaped single crystals 52, for example, as shown in Figures 4(b) to 4(d).

[0135] Next, in the thin plate single crystal manufacturing apparatus 10 of the present invention, the reason why the optical axes of the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 should be included in a plane perpendicular to the rotation direction of the holding unit 30, and further why the optical axes of the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 should be included in a plane slightly inclined toward the seed single crystal 50 with respect to the plane perpendicular to the rotation direction of the holding unit 30 will be explained using the main line-shaped laser beam 12 as an example.

[0136] That is, as shown in Figure 5 (a), the main linear laser beam 12 needs to be a main linear laser beam 12 that is perpendicular to the rotation direction of the holding unit 30, but if this main linear laser beam 12 is irradiated onto the upper surface 62 of the cylindrical raw material block 60 from diagonally above in a plane perpendicular to the upper surface 62 of the cylindrical raw material block 60, the main linear laser beam 12 will be reflected by the melt surface in the melting area 90.

[0137] In Figure 5 (a), a main linear laser beam 12 is irradiated onto a predetermined position (irradiation area) on the upper surface 62 of the cylindrical raw material block 60 from diagonally above the outer periphery of the cylindrical raw material block 60, forming a melted area 90, and reflected light 18 reflected by the molten liquid surface of this melted area 90 travels diagonally above the inner periphery of the cylindrical raw material block 60.

[0138] Therefore, if the main linear laser beam 12 is positioned in a plane perpendicular to the rotation direction of the holding section 30 (the cylindrical raw material block 60 held in the holding section 30), the reflected light 18 from the melt surface within the melting area 90 of this main linear laser beam 12 will similarly travel in a plane perpendicular to the rotation direction of the cylindrical raw material block 60, making it less likely that the reflected light 18 will hit the thin plate-shaped single crystal 52 being produced, and allowing the thin plate-shaped single crystal 52 to be produced continuously with good yield.

[0139] 5(b), when the thickness of the main line-shaped laser beam 12 is constant as in the thin plate single crystal manufacturing apparatus 10 of the present invention, the optical path of the reflected light 18 overlaps with the optical path at the time of irradiation while maintaining the same thickness, thereby preventing the reflected light 18 from impinging on the thin plate single crystal 52 being manufactured. Therefore, in the thin plate single crystal manufacturing apparatus 10 of the present invention, it is preferable that the thickness of the main line-shaped laser beam 12 is as constant as possible.

[0140] In this respect, the sub line-shaped laser beam 14 is similar to the main line-shaped laser beam 12 .

[0141] 5(b), the present specification mainly illustrates a case in which the optical axis of the main line-shaped laser beam 12 and the optical axis of the sub line-shaped laser beam 14 are included in a plane perpendicular to the rotation direction of the holder 30 (cylindrical raw material lump 60 held by the holder 30). In other words, the illustration shows that, when the rotation direction is the front, the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 are irradiated vertically downward and the reflected beam 18 is emitted vertically upward.

[0142] However, as shown in Figure 6, the optical axis of the main line-shaped laser beam 12 and the optical axis of the sub line-shaped laser beam 14 may be included in a plane that is slightly inclined toward the seed single crystal 50 with respect to a plane perpendicular to the rotation direction of the holding portion 30.

[0143] The inclination angle θ of the plane including the optical axis of the main line-shaped laser beam 12 arranged on the outer periphery side can be adjusted to match the size and position of the exit port of the main line-shaped laser beam 12 arranged on the inner periphery side, and is not particularly limited, and the inclination angle θ is a maximum of 10 degrees, preferably a maximum of 7 degrees, and more preferably a maximum of 5 degrees. As long as the inclination angle θ is within this inclination angle θ, the reflected light 18 can pass through while avoiding the exit port of the main line-shaped laser beam 12 arranged on the inner periphery side.

[0144] Furthermore, the inclination angle θ can be increased by moving the position (irradiation area) where the main line-shaped laser beam 12 is irradiated away from the position of the seed single crystal 50 (thin plate-shaped single crystal 52); however, if the position (irradiation area) where the main line-shaped laser beam 12 is irradiated away from the position of the seed single crystal 50 (thin plate-shaped single crystal 52), the temperature of the melt in the melting area 90 decreases as it moves away from the irradiation area, and therefore the temperature of the melt at the insertion position of the seed single crystal 50 decreases.

[0145] Therefore, to stably produce thin plate single crystal 52 with a large tilt angle θ, it is necessary to raise the temperature of the position (irradiation area) irradiated with main line-shaped laser beam 12, but doing so may cause inconveniences such as intense evaporation from the melt. Therefore, in reality, it is desirable to keep tilt angle θ at a maximum of about 5 degrees. Although Fig. 6 shows only the optical axis of main line-shaped laser beam 12, the tilt angle θ of the plane including the optical axis of sub line-shaped laser beam 14 is also the same as the tilt angle θ of the plane including the optical axis of main line-shaped laser beam 12.

[0146] That is, if the optical axes of the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 are included in a plane that is slightly inclined toward the seed single crystal 50 with respect to a plane perpendicular to the rotation direction of the holder 30 (the cylindrical raw material lump 60 held by the holder 30), the reflected light 18 will travel in a direction away from the seed single crystal 50. This makes it possible to reliably prevent the reflected light 18 from hitting the thin plate-shaped single crystal 52 to be manufactured. The symbol θ in Figure 6 represents the inclination angle.

[0147] In Figures 1 and 5(a), the case is shown in which the exit port 32 for the main linear laser beam 12 is arranged only on the outer periphery of the cylindrical raw material lump 60, and the reflected light 18 reflected by the melting zone 90 travels toward the inner periphery of the cylindrical raw material lump 60. However, although not shown, it is also possible to arrange the exit port 32 for the main linear laser beam 12 on both the outer and inner sides of the cylindrical raw material lump 60 (in other words, on both sides in the width direction of the thin plate-shaped single crystal 52 to be produced) and irradiate the main linear laser beam 12 at the same position (irradiation zone) from both sides, thereby producing a large thin plate-shaped single crystal 52.

[0148] In this case, by appropriately adjusting the positions of the exit port 32 for the main linear laser beam 12 arranged on the outer periphery of the cylindrical lump of raw material 60 and the exit port 32 for the main linear laser beam 12 arranged on the inner periphery of the cylindrical lump of raw material 60, as well as the inclination angle θ of the exit port 32 for the main linear laser beam 12 arranged on the outer periphery of the cylindrical lump of raw material 60 toward the seed single crystal 50 (thin plate single crystal 52 side), it is possible to prevent the reflected light 18 of the main linear laser beam 12 irradiated from the outer periphery on the surface of the melt in the molten region 90 from irradiating the exit port 32 for the main linear laser beam 12 arranged on the inner periphery. This makes it possible to stably produce large thin plate single crystals 52.

[0149] Of course, it is possible to arrange the outlet 32 ​​for the main linear laser beam 12 on both the outer and inner sides of the cylindrical raw material block 60 (in other words, on both sides of one width direction and the other width direction of the thin plate-shaped single crystal 52 to be produced), and it is also possible to arrange the outlet 36 for the secondary linear laser beam 14 on both the outer and inner sides of the cylindrical raw material block 60 (in other words, on both sides of one width direction and the other width direction of the thin plate-shaped single crystal 52 to be produced).

[0150] Furthermore, due to the structure of the thin plate single crystal manufacturing apparatus 10, the seed single crystal 50 (thin plate single crystal 52) is located directly beside the exit 32 of the main line-shaped laser beam 12 and directly beside the exit 36 ​​of the sub-line-shaped laser beam 14, so there is almost no room to significantly tilt the positions of the exit 32 of the main line-shaped laser beam 12 and the exit 36 ​​of the sub-line-shaped laser beam 14 toward the seed single crystal 50 (thin plate single crystal 52), and a slight tilt is the limit.

[0151] Here, there is no need to choose either whether the optical axis of the main line-shaped laser beam 12 and the optical axis of the sub line-shaped laser beam 14 are included in a plane perpendicular to the rotation direction of the holding unit 30, or whether the optical axis of the main line-shaped laser beam 12 and the optical axis of the sub line-shaped laser beam 14 are included in a plane slightly inclined toward the seed single crystal 50 with respect to a plane perpendicular to the rotation direction, which is the movement direction of the holding unit 30.

[0152] For example, the optical axis of the main line-shaped laser beam 12 may be included in a plane perpendicular to the rotation direction, and the optical axis of the sub line-shaped laser beam 14 may be included in a plane slightly inclined toward the seed single crystal 50 with respect to the plane perpendicular to the rotation direction.

[0153] Next, the enlargement of the size of the melted region 90 of the cylindrical raw material lump 60 while rotating the cylindrical raw material lump 60 (counterclockwise in this embodiment) by the rotating device 40 will be described.

[0154] If the single crystal material of the cylindrical raw material block 60 is a material with low thermal conductivity such as an oxide, a melted region 90 is formed by irradiation with the main linear laser beam 12, but the size of the melted region 90 is unlikely to expand even if the irradiation intensity of the main linear laser beam 12 is increased.

[0155] Therefore, if the irradiation intensity of the main linear laser beam 12 is increased too much in an attempt to form a melted region 90 of sufficient size to produce a thin plate-shaped single crystal 52, the temperature of the melted region 90 may rise too much, resulting in intense evaporation from the melted region 90.

[0156] 2(a) and 2(b), when the upper surface 62 of the cylindrical lump of raw material 60 is irradiated with the main linear laser beam 12, the area of ​​the upper surface 62 of the cylindrical lump of raw material 60 irradiated with the main linear laser beam 12 gradually melts, forming a melted region 90. Then, when the cylindrical lump of raw material 60 is slowly rotated (counterclockwise in this embodiment) by the rotation device 40, the melted region 90 can be expanded.

[0157] By immersing a thin plate-shaped seed single crystal 50 in the melting zone 90 expanded by the rotational movement of this cylindrical raw material block 60 and lifting it upward, crystallization begins from the underside of the seed single crystal 50, and thin plate-shaped single crystals 52 can be continuously produced via the joint 54.

[0158] Incidentally, when pulling up the thin plate-shaped single crystal 52 from the melting region 90, it is preferable that the temperature of the melting region 90 be uniform. If the temperature of the melting region 90 is not uniform, the growth of the thin plate-shaped single crystal 52 may shift toward the low temperature side, or the thickness of the thin plate-shaped single crystal 52 may become uneven.

[0159] 3( a) and 3(b), by using the sub-line laser beam 14 in addition to the main line laser beam 12, a uniform temperature region (uniformly heated region 91) can be formed within the melting region 90. By immersing the thin plate-shaped seed single crystal 50 in this uniformly heated region 91 and lifting it upward, crystallization starts from the lower surface of the seed single crystal 50, and thin plate-shaped single crystals 52 can be continuously and stably produced via the joint 54.

[0160] That is, the melted region 90 formed by the main linear laser beam 12 expands in the rotational direction as the cylindrical lump of raw material 60 rotates (counterclockwise in this embodiment), but the temperature of the melted region 90 gradually decreases due to heat radiation. Therefore, the sub-linear laser beam 14 is irradiated into the melted region 90 to form a soaked region 91 within the melted region 90, thereby facilitating the stable production of the thin plate single crystal 52.

[0161] 1 to 6, when actually manufacturing the thin plate-shaped single crystal 52, it is preferable to irradiate the ends of both sides of the thin plate-shaped single crystal 52 in the width direction with small-output spot-like laser light 116a, 116b, as shown in FIG. 8(c), to raise the temperature of the irradiated portions and define the size of the thin plate-shaped single crystal 52 in the width direction, but this is not shown in the figures to simplify the explanation.

[0162] That is, by irradiating spot-shaped laser beams 116a and 116b to the ends of both sides of the thin plate-shaped single crystal 52 in the width direction via a spot-shaped laser beam irradiation device (not shown), separately from the main line-shaped laser beam 12, or separately from the main line-shaped laser beam 12 and the sub line-shaped laser beam 14, the thin plate-shaped single crystal 52 can be manufactured with greater precision.

[0163] In this way, by adjusting the irradiation intensity of the main line-shaped laser beam 12 and the sub line-shaped laser beam 14, the rotation speed of the holding part, the temperature of the cylindrical raw material block 60, etc. to suit the single crystal material of the cylindrical raw material block 60, it is possible to continuously produce high-quality, large, thin plate-shaped single crystals 52 even from materials with low thermal conductivity such as oxides.

[0164] As described above, by using the thin plate single crystal manufacturing apparatus 10 of the present invention, it is possible to continuously manufacture thin plate single crystals 52, but as the thin plate single crystals 52 are continuously manufactured, the position of the upper surface 62 of the cylindrical raw material lump 60 will drop. If this happens, it is necessary to control the irradiation positions of the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 so that they are at desired positions.

[0165] In this embodiment, as shown in Figure 1, the shaft 46 of the rotating device 40 attached to the holding portion 30 that holds the cylindrical raw material lump 60 is equipped with an up-and-down movement device 86 that adjusts the vertical position of the holding portion 30.Therefore, even if the position of the upper surface 62 of the cylindrical raw material lump 60 drops as the continuously produced thin plate-shaped single crystals 52 are pulled up, the holding portion 30 can be raised to maintain the position of the upper surface 62 of the cylindrical raw material lump 60 at the same position as its original position, and the liquid surface position of the melt in the melting zone 90 can always be kept at the same position.

[0166] Therefore, it is only necessary to control the vertical movement device 86 so that the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 are always irradiated at the same position on the upper surface 62 of the cylindrical raw material block 60, and thin plate-shaped single crystals 52 can be produced continuously with stability and high yield.

[0167] According to the present invention, a melted region 90 is formed while rotating a cylindrical raw material lump 60 using a rotating device 40, and a main linear laser beam 12 and a secondary linear laser beam 14 are irradiated onto the upper surface 62 of the cylindrical raw material lump 60 perpendicular to the direction of rotation of the cylindrical raw material lump 60.Therefore, a thin plate single crystal manufacturing apparatus 10 can be provided that can form a melted region 90 of the required size for a cylindrical raw material lump 60 made of various materials such as metals, semiconductors, and insulators, without using a shielding plate as in the conventional method, even in the case of materials with low thermal conductivity such as oxides.

[0168] In addition, if the output of a commercially available laser light irradiation device (e.g., a laser oscillator device) is insufficient to produce a large thin plate-shaped single crystal 52, multiple laser light irradiation devices (not shown) can be used, with the outlets 32 of each main line-shaped laser beam 12 positioned on both the outer and inner sides of the cylindrical raw material lump 60 (in other words, on both sides in the width direction of the thin plate-shaped single crystal 52 to be produced), and the main line-shaped laser beam 12 emitted from both sides can be irradiated onto the same position (irradiation area) to form a melted area 90 of the desired size, thereby producing a large thin plate-shaped single crystal 52.

[0169] In such a case, by irradiating the multiple main line-shaped laser beams 12 so that their optical axes are contained within a plane inclined toward the seed single crystal 50 (thin plate-shaped single crystal 52) with respect to a plane perpendicular to the horizontal direction, it is possible to avoid the reflected light 18 directly hitting the exit port 32 of another main line-shaped laser beam 12 arranged on the inner side.

[0170] Therefore, with the present thin plate single crystal manufacturing apparatus 10, it is possible to continuously manufacture large, high-purity, high-quality thin plate single crystals 52 at low cost and with good operability.

[0171] Although the thin plate single crystal manufacturing apparatus 10 of the present invention has been described above, the thin plate single crystal manufacturing apparatus 10 of the present invention is not limited to the above-described embodiment.

[0172] For example, as shown in FIG. 7, the lifting device 80 may serve as a cutting and storage device 88 that pulls up the produced thin plate-shaped single crystal 52, cuts it into pieces of a predetermined length, and stores them.

[0173] The cutting and storage device 88 is configured so that the thin plate single crystal 52 can be pulled upward via a plurality of rollers 92, and then cut to a predetermined length in a cutting section 94. The cut thin plate single crystal 52 of the desired length is sent further upward to a storage section 96 and stored one by one. With the cutting and storage device 88 configured in this manner, the thin plate single crystal 52 can be cut and stored in lengths of, for example, about 2 m, allowing the thin plate single crystal 52 produced by the thin plate single crystal production apparatus 10 of the present invention to be suitably used in existing semiconductor-related equipment.

[0174] The rotation device 40 may also have a function of vibrating or slightly rocking the holding part 30. By adding such an operation, vibration is applied to the melting region 90, and when the thin plate-shaped single crystal 52 is produced, non-uniformity in the concentration of additives formed near the solid-liquid interface can be reduced, thereby suppressing cell growth and enabling the pulling speed when producing the thin plate-shaped single crystal 52 to be increased, thereby reducing the cost of producing the thin plate-shaped single crystal 52.

[0175] Furthermore, the positioning of the exit port 32 for the main line-shaped laser beam 12 may be biased toward the outer periphery of the cylindrical raw material lump 60, or may be positioned on both the outer and inner peripheries, depending on the output of the laser beam irradiation device (not shown) required for the thin plate-shaped single crystal 52 to be produced.

[0176] Furthermore, even when both the main line-shaped laser beam 12 and the sub line-shaped laser beam 14 are used, they may be biased toward the outer periphery of the cylindrical raw material lump 60, or may be provided on both the outer and inner peripheries, or a mixture of these.

[0177] In other words, for example, the main line-shaped laser beam 12 may be biased toward the outer periphery of the cylindrical raw material block 60, and the sub line-shaped laser beam 14 may be provided on both the inner and outer periphery of the cylindrical raw material block 60, and the design can be modified as appropriate.

[0178] Furthermore, in the above embodiment, the thin plate single crystal 52 is mainly produced using both the main line-shaped laser beam 12 and the sub-line-shaped laser beam 14, but this is not limited to this, and the thin plate single crystal 52 may also be produced using only the main line-shaped laser beam 12 without using the sub-line-shaped laser beam 14, as shown in Figures 2(a) and 2(b).

[0179] In addition, various modifications are possible within the scope of the purpose of the present invention, such as the use of the technical content described in the thin plate single crystal manufacturing apparatus and thin plate single crystal manufacturing method already filed by the applicant (for example, JP 2023-025811 A).

[0180] REFERENCE SIGNS LIST 10 Thin plate single crystal manufacturing apparatus 12 Main line-shaped laser beam 14 Sub-line-shaped laser beam 18 Reflected light 20 Chamber 22 Window 30 Holding section 32 Exit port 34 Reflected light shielding tube 36 Exit port 40 Rotating device 42 Stand 46 Shaft 48 Control section 50 Seed single crystal 52 Thin plate single crystal 54 Joining section 60 Cylindrical raw material lump 62 Upper surface 70 Preheating device 80 Lifting device 82 Winding and storage device 83 Rotating device 84 Winding reel 85 Rotating roller 86 Up and down movement device 88 Cutting and storage device 90 Melting area 91 Soaking area 92 Roller 94 Cutting section 96 Storage section 100 Raw material lump 102 Upper surface 110a Exit port 110b: Exit port 112a: Laser beam 112b: Laser beam 114a: Exit port 114b: Exit port 116a: Spot-shaped laser beam 116b: Spot-shaped laser beam 120: Melted region 120a: Melted region 120b: Melted region 130: Seed single crystal 132: Bonding portion 134: Thin plate-shaped single crystal 140a: Shielding plate 140b: Shielding plate θ: Tilt angle

Claims

1. A thin plate single crystal manufacturing apparatus comprising at least: a holding unit that holds a raw material lump in an upright position; a laser light irradiator that irradiates a laser light onto the upper side of the raw material lump held by the holding unit to melt the surface of the upper side and form a melted region; and a lifting device that immerses a thin plate-shaped seed single crystal into the melted region formed on the upper side of the raw material lump and lifts the seed single crystal upward from the immersed state; by immersing the seed single crystal in the melting region via the lifting device, single crystal growth begins from the lower side of the immersed seed single crystal, and by lifting the seed single crystal upward via the lifting device, thin plate-shaped single crystals are continuously manufactured; the thin plate-shaped single crystal manufacturing apparatus comprises a rotation device that rotates the holding unit; and the laser light irradiated from the laser light irradiator is a main line-shaped laser light, and is configured so that the optical axis of the main line-shaped laser light is included in a plane perpendicular to the rotation direction of the holding unit rotated by the rotation device. Alternatively, the thin plate single crystal manufacturing apparatus is characterized in that the optical axis of the main line-shaped laser beam is included within a plane that is slightly inclined toward the seed single crystal with respect to a plane perpendicular to the rotation direction of the holding part rotated by the rotation device.

2. The thin plate single crystal manufacturing apparatus according to claim 1, wherein the raw material lump is a cylindrical raw material lump.

3. The thin plate single crystal manufacturing apparatus as described in claim 1, characterized in that, when the raw material block is held in the holding section, the main line-shaped laser light is configured to irradiate the upper surface of the raw material block from diagonally above the raw material block.

4. The thin plate single crystal manufacturing apparatus according to claim 1, characterized in that a preheating device for preheating the raw material ingot is disposed around the holding section.

5. The thin plate single crystal manufacturing apparatus according to claim 1, further comprising a vertical movement device for moving the holding part in the vertical direction.

6. The thin plate single crystal manufacturing apparatus according to claim 1, characterized in that the lifting device is a winding and storing device that continuously winds up the manufactured thin plate single crystal in a roll and stores it.

7. The thin plate single crystal manufacturing apparatus according to claim 1, characterized in that the lifting device is a cutting and storing device that pulls up the thin plate single crystal being continuously manufactured, cuts it into predetermined lengths, and stores it.

8. The thin plate single crystal manufacturing apparatus according to claim 1, further comprising a secondary laser light irradiating device that assists the laser light irradiating device, wherein the laser light irradiated from the secondary laser light irradiating device is a secondary line-shaped laser light, and wherein the optical axis of the secondary line-shaped laser light is included within a plane perpendicular to the rotation direction of the holding part rotated by the rotating device, or wherein the optical axis of the secondary line-shaped laser light is included within a plane that is slightly inclined towards the seed single crystal with respect to the plane perpendicular to the rotation direction of the holding part rotated by the rotating device.

9. The thin plate single crystal manufacturing apparatus as described in claim 8, characterized in that, when the raw material block is held in the holding section, the secondary line-shaped laser light is configured to irradiate the upper surface of the raw material block from diagonally above the raw material block.

10. A thin plate single crystal manufacturing apparatus as described in claim 8, characterized in that a main line-shaped laser beam is irradiated on one side of the seed single crystal in the thickness direction, and a sub-line-shaped laser beam is irradiated on the other side of the seed single crystal in the thickness direction, with the seed single crystal immersed in the melting zone of the raw material lump as the boundary.

11. The thin plate single crystal manufacturing apparatus according to claim 1, wherein a reflected light shielding cylinder is provided at the center of the holder rotated by the rotation device.

12. The thin plate single crystal manufacturing apparatus according to claim 1, wherein the seed single crystal has a facet surface.

13. The thin plate-shaped single crystal according to claim 1, characterized in that the plane containing the optical axis of the main line-shaped laser beam and slightly inclined toward the seed single crystal is a plane inclined at a maximum of 10 degrees toward the seed single crystal with respect to a plane perpendicular to the rotation direction of the holding part.

14. A thin plate-shaped single crystal as described in claim 8, characterized in that the plane containing the optical axis of the secondary line-shaped laser beam and slightly inclined toward the seed single crystal is a plane inclined by a maximum of 10 degrees toward the seed single crystal with respect to a plane perpendicular to the rotation direction of the holding part.

15. A thin plate single crystal produced by the thin plate single crystal production apparatus according to any one of claims 1 to 14.

16. The thin plate-shaped single crystal according to claim 15, wherein the thickness of the thin plate-shaped single crystal is within the range of 30 to 5,000 μm.

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