JP2019112264A - Evaluation method, evaluation device and evaluation program of growth state of single crystal, production method of single crystal, and single crystal production apparatus - Google Patents

Abstract

To evaluate accurately a state related to melting of a seed crystal.SOLUTION: In an evaluation method of a growth state of a single crystal, when a seed crystal is brought into contact with a raw material melt formed by melting a raw material, and the seed crystal is rotated and simultaneously lifted to thereby grow the single crystal, a state related to melting of the seed crystal is evaluated based on a fluctuation range of a measured weight relative to a measured weight of the seed crystal measured at a melting time of the seed crystal by bringing the seed crystal into contact with the raw material melt.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an evaluation method, an evaluation apparatus, an evaluation program, a method of manufacturing a single crystal, and an apparatus for manufacturing a single crystal of a growth state of a single crystal.

Single crystal materials are used in various industrial products. For example, an oxide single crystal substrate processed from a single crystal of lithium tantalate (LiTaO ₃ : hereinafter abbreviated as LT) or lithium niobate (LiNbO ₃ : abbreviated as LN) which is a ferroelectric substance is It is mainly used as a material of surface acoustic wave devices (SAW filters) for removing electrical signal noise in mobile communication devices.

  Industrially, LT and LN single crystals, which are materials for SAW filters, are grown mainly by the Czochralski method (hereinafter abbreviated as "Cz method"). In the Cz method, as shown in FIGS. 6 and 7, a single crystal piece to be a seed crystal SC is brought into contact with the surface of the raw material melt L in a crucible and the seed crystal SC is rotated upward while rotating the seed crystal SC. This is a method of growing a cylindrical single crystal CR in the same orientation as the seed crystal SC by pulling it up. In the Cz method, the rotation speed and pulling speed of the seed crystal SC depend on the type of crystal CR (single crystal) to be grown and the temperature environment at the time of growth, and it is necessary to select appropriately according to these conditions. In addition, since it is necessary to dissipate upward the solidification latent heat generated by crystallization of the melt at the growth interface through the seed crystal SC during single crystal growth, under a temperature gradient in which the temperature decreases upward from the growth interface There is a need to do. In addition, in order to prevent the shape of the growth crystal (crystal to be grown) from bending or twisting, the raw material melt L also extends horizontally from the growth interface to the wall of the crucible and from the growth interface. It should be done under a temperature gradient where the temperature rises vertically towards the bottom of the weir.

  For example, in the case of LT single crystal growth, since the melting point of LT crystal is as high as 1650 ° C., using a crucible made of iridium (Ir) which is a high melting point metal, high-frequency induction heating type electric furnace (single crystal growth They are grown using a furnace (sometimes abbreviated "growing furnace"). Generally, the pulling speed during growth is about several mm / H, and the rotational speed is about several r.p.m. Moreover, it is general to set it as the mixed gas atmosphere of nitrogen-oxygen whose oxygen concentration is about several% at the time of growth inside the furnace. Under such conditions, after growing the crystal CR to a desired size, the grown crystal CR is separated from the melt by performing operations such as changing the pulling rate and gradually raising the melt temperature. The power of the growth furnace is lowered at a predetermined rate to gradually cool, and after the temperature in the growth furnace becomes around room temperature, the crystal CR is taken out from the growth furnace. The crystal CR taken out is subjected to crystal growth and cooling in an environment of a growth furnace with a temperature gradient, so that thermal strain (residual strain) caused by a temperature difference is inherent in the crystal CR. In order to remove the residual strain, annealing and slow cooling are performed in a soaking furnace. This process is called annealing.

  In ferroelectrics such as LT and LN crystals, when the temperature of the crystal falls below the Curie temperature, positive or negative electrical polarity is generated in the crystal due to spontaneous polarization, but the crystal after annealing has its direction of polarity Are not aligned in the crystal. Therefore, the crystal after annealing is subjected to poling treatment in order to make the electrical polarity uniform. In the poling process, a positive and negative pair of electrodes are attached in the crystal's electrical polarity direction, and after raising the temperature to the Curie temperature or higher, a voltage is applied to the crystal and the crystal temperature is maintained while maintaining the voltage application. It is processing to lower to the Curie temperature or less. Since the Curie temperature of the LT crystal is about 600 ° C., poling treatment of the LT crystal is performed by applying a voltage after setting the crystal temperature to 600 ° C. or more. Since the Curie temperature of the LN crystal is about 1140 ° C., the poling treatment is performed with the crystal temperature of 1140 ° C. or higher. The crystal after poling treatment is sliced almost perpendicularly to the growth orientation, and is processed into a single crystal substrate with a thickness of about several hundred microns by a subsequent polishing process, and used as a material of the SAW filter.

  Most of the SAW filters used in mobile communication devices use an LT substrate processed with a substrate principal surface orientation of around 42 ° RY and an LN substrate processed with a principal surface orientation of around 128 ° RY. Here, for example, as shown in FIG. 9, 42 ° RY is a direction rotated by 42 ° in the Z-axis direction from the Y-axis in the YZ plane with the X-axis as the rotation axis. A substrate processed perpendicular to such an orientation is called a substrate with a main surface orientation of 42 ° RY. The LT and LN crystals are trigonal. The definition of the X, Y, Z directions for the symmetry of the crystal is shown in FIG.

  In the Cz method, for example, as shown in FIG. 6, the seed crystal is connected to the pulling shaft 28 via a seed holder (seed crystal holding portion 38). The seed crystal SC is brought into contact with the surface of the raw material melt L in the crucible 10, and the crystal growth is started by pulling up the seed crystal SC while rotating the seed crystal SC.

  When single crystals CR such as LT and LN are grown using such a configuration, when crystals are taken out from the growth furnace, often the polycrystalization of grown crystals CR and grown crystals CR become seed crystals There was a situation where it dropped from the contact part (connection part) of SC. At the tip of the seed crystal SC brought into contact with the surface of the raw material melt L in the crucible, a curved meniscus M formed by the surface of the raw material melt L is formed by interfacial tension as shown in FIG. In order to suppress polycrystallization of the grown crystal CR, for example, the output of the high-frequency induction heating furnace is adjusted, and the meniscus diameter MD formed at the tip portion of the seed crystal SC (minimum diameter when meniscus is formed) After the raw material melt L and the tip portion of the seed crystal SC are fitted to each other, the pulling of the seed crystal SC is started. It is known that this meniscus diameter MD is related to the melting amount of the seed crystal SC. The amount of melting of the seed crystal SC by visually confirming the meniscus diameter MD of the crystal formed at the tip of the seed crystal SC based on the image taken by the camera installed in the observation window at the top of the high frequency induction heating furnace Had to judge. However, according to visual confirmation in the photographed image, the melting amount of the seed crystal SC varies widely, and when the melting amount of the seed crystal SC is large, the crystal CR which is grown falls from the contact portion of the seed crystal SC, If the melting amount of the seed crystal SC is too small, the incidence of polycrystallization of the grown crystal CR increases, and as a result, the product substrate can not be processed from the grown crystal CR, which lowers productivity and increases cost. It was a factor. That is, in the growth of single crystal CR by the Cz method or the like, problems occur in the growth of single crystal CR depending on the state related to melting of the seed crystal SC as described above.

  Further, Patent Document 1 below discloses a method of calculating and starting from the measured weight change of the seed crystal, what has conventionally been determined visually with respect to the timing of starting pulling in the Cz method. According to Patent Document 1, after the meniscus is stabilized, the pulling axis is raised at a speed of 20 to 300 mm per hour, and when the amount of change in measured weight at that time becomes a predetermined size, pulling is started. It is described that crystal growth can be initiated at the same optimum temperature each time.

  However, in the method of Patent Document 1, the seed crystal is pulled after the meniscus is stabilized, and the growth state of the crystal is judged according to the change in weight, and the size of the meniscus diameter as described above, etc. The state concerning melting of the seed crystal and the polycrystallization or drop of the crystal that occurs accordingly can not be grasped. Further, since the method of Patent Document 1 is a method of determining the start timing of pulling for the growth of a single crystal after the meniscus is stabilized, it relates to the melting of the seed crystal such as the size of the meniscus diameter as described above. It is not possible to grasp the state or the polycrystallization or the drop of the crystal which occurs depending on the state. Further, in the method of Patent Document 1, when growing the initial crystal, if the above-mentioned change in measured weight does not reach a predetermined change in weight, it is essential to pull up the seed crystal after the meniscus is stabilized. At that time, since the crystal is grown from the seed crystal, it is necessary to melt the grown crystal again, and as a result, there is a problem that the productivity is lowered.

  Therefore, in the growth of a single crystal by the Cz method or the like, it is required to accurately evaluate the state concerning melting of the seed crystal as described above.

Japanese Examined Patent Publication No. 6-99229

  The present invention has been made in view of such problems, and an object thereof is to accurately evaluate a state concerning melting of a seed crystal.

  Then, in order to solve the above-mentioned subject, the present inventor made the seed crystal tip part of the crystal which fell from the contact part of the seed crystal made to contact the raw material melt surface in a crucible, and the polycrystallized crystal, and a single crystal. The amount of melting of the tip of the seed crystal is observed in detail, and the relationship between the measured weight of the seed crystal at the time of melting of the tip of the seed crystal and the neck diameter of the taken out crystal is found. As a result of attempting modification, the present invention has been completed.

  In the first aspect of the present invention, the seed crystal is brought into contact with the raw material melt obtained by melting the raw material, and the seed crystal is raised while rotating the seed crystal to bring the seed crystal into contact with the raw material melt. Thus, there is provided a method of evaluating the growth state of a single crystal, which evaluates the state concerning melting of the seed crystal based on the fluctuation range of the measured weight in the measured weight of the seed crystal measured when the seed crystal melts. .

  In a second aspect of the present invention, in the first aspect, there is provided an evaluation method according to claim 1, comprising measuring the weight of a seed crystal.

  In a third aspect of the present invention, in the first or second aspect, there is provided an evaluation method comprising determining a fluctuation range based on the measured weight of a seed crystal measured when the seed crystal is melted. Ru.

  In the fourth aspect of the present invention, in any of the first to third aspects, the evaluation of the state regarding melting of the seed crystal includes making an evaluation regarding the melting amount of the seed crystal based on the fluctuation range. An evaluation method is provided.

  In the fifth aspect of the present invention, in any of the first to fourth aspects, the evaluation of the state concerning melting of the seed crystal is an evaluation regarding the ease of falling of the grown single crystal based on the fluctuation range. And assessing the susceptibility of the grown single crystal to polycrystallization on the basis of the fluctuation range.

  In the sixth aspect of the present invention, in any of the first to fifth aspects, the fluctuation range is such that the measured weight immediately after contacting the seed crystal with the raw material melt is higher than the actual weight of the seed crystal. An evaluation method is provided, which is the difference between the time value and the value in the stable region where the variation per unit time of measured weight immediately after contacting the seed crystal with the raw material melt is less than a predetermined value. Ru.

  A seventh aspect of the present invention provides an evaluation method according to any one of the first to sixth aspects, wherein the single crystal is lithium tantalate or lithium niobate.

  In an eighth aspect of the present invention, in the seventh aspect, the single crystal is lithium tantalate, and the fluctuation range is more than 0.5 g and less than 0.9, in a state regarding melting of the seed crystal, An evaluation method is provided that includes evaluating that the grown single crystal does not fall and does not polycrystallize.

  According to a ninth aspect of the present invention, a seed crystal is brought into contact with a raw material melt obtained by melting a raw material, and the seed crystal is raised while rotating to grow crystals, and any of the second to eighth aspects. The evaluation method provides a method for producing a single crystal, including evaluating an evaluation of a state related to melting of a seed crystal.

  In the tenth aspect of the present invention, the seed crystal is brought into contact with the raw material melt obtained by melting the raw material, and the seed crystal is raised while rotating the seed crystal to grow the single crystal. Of the growth state of a single crystal provided with an evaluation unit for evaluating the state related to the melting of the seed crystal based on the fluctuation range of the measured weight in the measured weight of the seed crystal measured when the seed crystal melts An apparatus is provided.

  In the eleventh aspect of the present invention, when bringing a seed crystal into contact with a raw material melt obtained by melting a raw material in a computer and raising the seed crystal while rotating the seed crystal to grow a single crystal, the seed crystal is melted. A process of evaluating the state regarding melting of the seed crystal based on the fluctuation range of the measured weight in the measured weight of the seed crystal measured when the seed crystal melts by being brought into contact with the liquid, a single crystal A training status assessment program is provided.

  According to a twelfth aspect of the present invention, there is provided an apparatus for bringing a seed crystal into contact with a raw material melt obtained by melting a raw material in a crucible, and raising the seed crystal while rotating to grow a single crystal. The heating part which heats and melts the raw material, the rotating pulling shaft which holds the seed crystal and raises and lowers while rotating the seed crystal, the weight of the seed crystal, and the weight of the growing single crystal containing the seed crystal over time The seed crystal is melted using the measurement results of the weight measurement unit that measures the temperature, the heating control unit that controls the temperature of the heating unit, the drive control unit that controls the rotation and elevation of the rotation pulling unit, and the measurement results of the weight measurement unit A single crystal manufacturing apparatus is provided, which includes the evaluation device according to a tenth aspect for evaluating a state related to and a specific processing unit that executes a predetermined process preset according to the evaluation result of the evaluation device.

  The evaluation method, the evaluation apparatus, and the evaluation program of the growth state of the single crystal of the present invention can accurately evaluate the state related to the melting of the seed crystal.

  Further, since the method and apparatus for producing a single crystal according to the present invention includes the above-described evaluation method or apparatus, it is possible to suppress variations in the melting state of the seed crystal by accurately evaluating the state related to melting of the seed crystal. The optimization of the melting state of the seed crystal can be achieved, and as a result, the growth defects of the grown crystal such as falling and polycrystallization which occur depending on the state related to the melting of the seed crystal are suppressed, Productivity and cost can be reduced. In addition, since the method of producing a single crystal of the present invention can stably control the melting of the seed crystal by adjusting the fluctuation width C (see FIG. 2) quantitatively, high quality single crystals can be obtained. It can be manufactured easily and stably.

(A) to (C) are flowcharts showing the evaluation method of the growth state of the single crystal according to the embodiment. It is a figure which shows an example of the measurement weight at the time of melting of a seed crystal. It is a figure which shows the investigation result of this embodiment. It is a figure which shows an example of the evaluation apparatus of this embodiment. It is a flowchart which shows an example of the manufacturing method of the single crystal of this embodiment. It is a figure which shows an example of the single-crystal manufacturing apparatus of this embodiment. It is explanatory drawing of the meniscus of the front-end | tip part of the seed crystal at the time of single crystal growth. It is explanatory drawing of the front-end | tip part of the seed crystal in the grown single crystal. It is explanatory drawing of the single crystal of lithium tantalate. It is explanatory drawing of the symmetry of the single crystal of lithium tantalate.

  Hereinafter, the present invention will be described with reference to the drawings. However, the present invention is not limited to this. Further, in the drawings, in order to explain the embodiment, the scale is appropriately changed and expressed such that a part is described in a large or emphasized manner. In the following drawings, directions in the drawings may be described using an XYZ coordinate system. In this XYZ coordinate system, the vertical direction is taken as the Z direction, and the horizontal direction is taken as the X direction and the Y direction. In each of the X direction, the Y direction, and the Z direction, the tip side of the arrow is referred to as the + side (eg, + X side), and the opposite side is referred to as the − side (eg, −X side).

[Method of evaluating growth state of single crystal]
FIGS. 1A to 1C are flowcharts showing an example of a method of evaluating the growth state of a single crystal according to the embodiment (sometimes referred to as “evaluation method” or “this evaluation method”).

  This evaluation method is an evaluation method of a growth state of a single crystal, which evaluates a state related to melting of the seed crystal SC, as shown in FIGS. 1 (A) to (C).

  Hereinafter, the present evaluation method will be described in detail in comparison with the conventional method.

[Conventional method]
As described above, when the front end portion of the seed crystal SC is brought into contact with the surface of the raw material melt L in the crucible and pulled up, polycrystallization or growth of the crystal CR to be grown is frequently caused due to the contact state. Problems such as the crystal CR falling from the connection portion with the seed crystal occur. Therefore, conventionally, the state (meniscus state) of the meniscus M formed at the front end of the seed crystal SC is visually observed based on the image captured by the camera (video camera) installed in the observation window at the top of the high frequency induction heating furnace After confirmation, the melting amount of the tip of the seed crystal SC was determined. In particular, in order to suppress the polycrystallization of the crystal CR to be grown as described above, it was visually judged so as to reduce the meniscus diameter MD (see FIG. 7). However, the appearance of the meniscus state changes due to the angle of the camera and the eccentricity at the time of rotation of the seed crystal SC, etc., so that the crystal CR can not be stably grown. When crystal growth is performed in such a state, when the meniscus diameter MD is expanded, the frequency of the grown crystal CR becoming polycrystalline increases, and when the meniscus diameter MD is excessively reduced, the tip of the seed crystal SC The frequency of occurrence of the drop of the crystal CR grown from (connected portion, contact portion) increased.

[Study on melting amount of seed crystal according to conventional method]
When observing the grown crystal CR in which the meniscus diameter MD is expanded and a polycrystal is generated, on the contrary, the crystal CR in which the meniscus diameter MD is reduced and a drop is generated, and the seed crystal SC used for the growth It was found that the tip of the seed crystal SC of the crystal CR had a small amount of melting, and the tip of the seed crystal SC of the grown crystal CR where the drop occurred had a large amount of melting.

  When the tip of the seed crystal SC contacts the surface of the raw material melt L, the meniscus M is generated by melting and the meniscus diameter tends to decrease as the melting amount (dissolution amount) of the seed crystal SC increases. Therefore, the state of the grown crystal CR taken out after being grown, the neck diameter ND, and the melting amount of the tip portion of the seed crystal SC were investigated. With respect to the state of the grown crystal, it was a good crystal, polycrystallized crystal, and a dropped crystal. The neck diameter ND was taken as the minimum diameter of the neck portion N of the crystal CR when the growth was completed. The minimum diameter of the neck portion N (neck diameter ND (see FIG. 8)) is approximately the same as the meniscus diameter MD at the time of crystal growth. In the present investigation, "seed crystal diameter-neck diameter ND" was calculated. Also, in this study, the melting amount of the tip of the seed crystal SC can not be confirmed during the growth, so the load cell (weight measurement) installed above the pulling shaft (rotation pulling shaft 28, see FIG. 6) The measured weight of the crystal CR containing the seed crystal SC is measured using the part 30 (see FIG. 6), and the seed crystal SC measured when the seed crystal SC melts by being brought into contact with the raw material melt L The fluctuation range C (see FIG. 2) of the measured weight D1 in the measured weight D1 was taken as an amount related to the melting amount of the seed crystal SC. In the present specification, "the measured weight of the seed crystal measured when the seed crystal melts by being brought into contact with the raw material melt" may be referred to as "the measured weight when melting the seed crystal".

  The fluctuation range C will be described below. FIG. 2 is a graph showing the change of the measured weight D1 at the time of melting of the seed crystal SC. As for the measured weight (relative value) shown in FIG. 2, the value of the measured weight obtained by measuring the weight of the grown crystal containing the seed crystal SC is attached to the rotating shaft of the seed crystal SC and brought into contact with the raw material melt L. It is a converted value (relative value) converted so that the value of the measured weight in the not-omitted state becomes “0 g”. Further, in FIG. 2, the tip portion of the seed crystal SC is brought into contact with the raw material melt L at the location of the arrow A. At this time, due to the surface tension of the raw material melt L, the measured weight of the seed crystal SC once increases. Thereafter, the tip of the seed crystal SC is melted to generate a meniscus M. During this time, the measured weight of the seed crystal SC gradually decreases. After that, there is almost no change in the measured weight of the seed crystal SC, and the stable region B becomes almost constant. Generally, the stable region B is confirmed, and pulling of the seed crystal SC is started. Arrow D in FIG. 2 indicates the timing at which the pulling is started. In this investigation, this stable region B was in a state where the change in measured weight of the seed crystal SC was within 0.1 g for 10 minutes or more. Further, in the present investigation, when the fluctuation width C is caused by bringing the measured weight of the seed crystal SC in the stable region B and the seed crystal SC into contact with the raw material melt L at the location of arrow A, the weight once increases due to surface tension. The difference (difference) from the measured weight of the seed crystal SC was used. The fluctuation range C changes depending on various conditions such as the temperature of the raw material melt L, the atmosphere in the growth furnace, and the like. The fluctuation range C is obtained by bringing the seed crystal SC into contact with the raw material melt L at the location of the arrow A, and measuring the seed crystal SC in the stable region B from the measured weight of the seed crystal SC whose measurement weight once increased by surface tension. It may be a value obtained by subtracting the weight or may be an absolute value of this value.

  The survey results are shown in FIG. FIG. 3 shows data on crystals of LT, and in FIG. 3, the vertical axis indicates a fluctuation range C, and the horizontal axis indicates “seed crystal diameter-neck diameter ND”. From the investigation results shown in FIG. 3, the melting amount (variation width C) of the tip portion of the seed crystal SC of the crystal CR grown by the above-described conventional method has a large variation, and the "seed crystal diameter-neck diameter ND" There is a variation of -0.2 mm to +5.3 mm with respect to the seed crystal diameter. That is, according to the results of this investigation, in the growth of single crystal CR by the conventional method, the amount of melting of the seed crystal SC, variation in the melting state of the seed crystal SC such as "seed diameter-neck diameter ND" (neck diameter ND) As a result, it was found that the above-described defects in growth defects of the single crystal due to the drop and polycrystallization of the growth crystal described above frequently occurred.

  Further, as shown in the approximation result from the investigation result shown in FIG. 3, “seed crystal diameter−neck diameter ND” and “neck diameter ND” are relative to fluctuation width C (an amount related to the melting amount of seed crystal SC) It was found that there is a high linear correlation. From this result, the diameter (meniscus diameter MD, neck diameter ND) of the portion where the meniscus M is formed is accurately estimated by the fluctuation range C (an amount related to the melting amount of the seed crystal SC). We found that we could evaluate the condition accurately. In addition, the inventor found that the fluctuation range C (the amount regarding the melting amount of the seed crystal SC) is the same amount as the melting amount of the seed crystal SC. The inventor has also found that the drop of the grown crystal CR from the tip of the seed crystal SC and the generation cause of polycrystals in the grown crystal CR are the meniscus diameter MD (neck diameter ND), that is, the melting amount of the tip of the seed crystal SC. It was found to be related to (the fluctuation range C). In addition, the inventor has found that the grown single crystal is easy to fall and hard to fall when the melting amount (the fluctuation range C) of the tip portion of the seed crystal SC is within a predetermined range (condition), and it is easy to polycrystallize. It has been found that it is possible to find that it is difficult to make it happen, and it is possible to accurately determine the condition of the fluctuation range C which is hard to fall (not) and the condition of the fluctuation range C which is hard to polycrystallize (not). Then, as a result of further studies and improvements, the inventor found an evaluation method and the like of the present invention. Thus, based on the investigation results shown in FIG. 3, the inventor is able to accurately and easily evaluate the state regarding the melting of the seed crystal SC by the fluctuation range C (the amount regarding the melting amount of the seed crystal SC). I found that. Moreover, the inventor is able to stably grow high-quality single crystals by adjusting the growth conditions so that the fluctuation range C falls within the predetermined range based on the above-mentioned investigation results, that is, a novel The growth conditions (production method) of single crystals were found out. For example, the inventor found from the above survey results that, in the case of the growth of a single crystal of LT, the fluctuation range C is more than 0.5 g and less than 0.9, preferably 0.6 g or more and 0.8 g or less It has been found that by adjusting the growth conditions, high quality single crystals can be stably grown.

  Hereinafter, this evaluation method will be described in detail. In this evaluation method, as shown in FIG. 1 (A), in step S1, the seed crystal SC is brought into contact with the raw material melt L in which the raw material is melted, and raised while rotating the seed crystal SC. When growing the seed crystal SC, by contacting the seed crystal SC with the raw material melt L, the seed crystal is measured based on the fluctuation range C of the measurement weight D1 in the measurement weight D1 of the seed crystal SC measured when melting the seed crystal SC. This is a method of evaluating the growth state of a single crystal, which evaluates the state concerning melting of SC.

  The method of producing a single crystal (growth method) which can use this evaluation method is to bring the seed crystal SC into contact with the raw material melt L obtained by melting the raw material, and raise the single crystal CR by rotating the seed crystal SC. It is a method of nurturing, for example, Cz method. In addition, about the detail of the manufacturing method of the single crystal which uses this evaluation method, it demonstrates later in the part of "the manufacturing method of a single crystal" of this embodiment.

  The single crystal CR and the seed crystal SC that can be used in the present evaluation method are not particularly limited and are arbitrary. For example, the composition, size, etc. of the seed crystal SC and the single crystal CR are arbitrary. Further, the single crystal growth apparatus that can be used in the present evaluation method is not particularly limited, and, for example, a known single crystal growth apparatus capable of performing the Cz method can be used. For example, in the embodiment described later A single crystal manufacturing apparatus can be used.

  Step S1 of this evaluation method is performed by step S2 to step S4 shown in FIG. 1 (B), for example.

  In step S1 of this evaluation method, for example, in step S2, first, the measured weight of the seed crystal SC is measured. The measuring method of the measurement weight of the seed crystals SC is not particularly limited, and a known method can be used. For example, the measurement weight of the seed crystal SC can be measured by using a weight sensor such as a load cell installed above the rotating pulling shaft that pulls up the seed crystal SC and the growing single crystal CR while rotating (eg, the weight measuring unit 30 in FIG. 6). Etc.) by measuring the measured weight of the single crystal CR containing the seed crystal SC over time. The measurement of the measured weight of the seed crystal SC is performed during the growth of the single crystal CR. The weight sensor is not particularly limited. Further, the measurement frequency (frequency of sampling) of the measured weight of the seed crystal SC is not particularly limited, but is set so as to be able to detect, for example, data (including) the fluctuation range C described above.

  The data of the measured weight of the seed crystal SC used in the present evaluation method is the measured weight D1 of the seed crystal SC measured when the seed crystal SC is melted by bringing the seed crystal SC into contact with the raw material melt L Data of when measured weight D1), including data indicating fluctuation range C (see FIG. 2). For example, in the data of the measured weight D1 when melting the seed crystal, the measured weight immediately after contacting the seed crystal SC with the raw material melt L is higher than the actual weight of the seed crystal SC as shown in FIG. It is preferable that it is continuous data of the measured weight of the seed crystal SC from the state (arrow A) to the state of the stable region B immediately after contacting the seed crystal SC with the raw material melt L. Thereby, the fluctuation range C can be determined more reliably. The data of the measurement weight D1 at the time of melting of the seed crystal can generally be obtained in a known general single crystal growth apparatus. The fluctuation range C and the stable region B will be described in the next step S3 (see FIG. 1 (B)).

  Subsequently, in step S3 of FIG. 1B, the fluctuation range C is obtained based on the measured weight D1 at the time of melting the seed crystal measured in step S2. In the present embodiment, the fluctuation range C is the measured weight of the seed crystal SC when the measured weight of the seed crystal SC immediately after contacting the seed crystal SC with the raw material melt L is higher than the actual weight of the seed crystal SC. And the measured weight of the seed crystal SC in the stable region B immediately after contacting the seed crystal SC with the raw material melt L (see FIG. 2). Further, the stable region B is set to a portion where the variation per unit time of the measured weight of the seed crystal SC immediately after contacting the seed crystal SC with the raw material melt L is equal to or less than a predetermined value. The predetermined value of the variation per hour of the measured weight of the seed crystal SC is not particularly limited without departing from the spirit of the present invention, but, for example, as in the above-described present survey, the seed crystal SC is It can be made the state (condition) which is less than 0.1 g of change of measurement weight. The fluctuation range C described above can be obtained at a measured weight D1 when melting a seed crystal at the time of growing a general single crystal.

  For example, the fluctuation range C in step S3 may be obtained by a computer or a human. However, it is preferable to obtain it by a computer from the viewpoint of work efficiency, manufacturing efficiency, and the like. Above all, the fluctuation range C is preferably determined by a computer during the growth of the single crystal CR. When the fluctuation range C is determined by a computer, the fluctuation range C can be determined in real time when growing the single crystal CR. The fluctuation range C is measured weight of the seed crystal SC immediately after bringing the seed crystal SC into contact with the raw material melt L from the measured weight D1 at melting of the seed crystal by a general known method using, for example, a computer And the pattern indicating the measured weight of the seed crystal SC in the stable region B can be extracted, and the difference between the measured weights can be calculated. For example, the fluctuation range C can be obtained using the evaluation device 1 (evaluation program P) of the present embodiment described later. When the fluctuation range C is determined, processing of data of the measured weight D1 (for example, statistical processing for determining an average value, an approximate value, and the like) may be performed.

  Further, the timing for obtaining the fluctuation range C in step S3 is preferably during the growth of the single crystal CR, and it is preferable to obtain the fluctuation range C before starting the pulling of the seed crystal SC. Above all, it is preferable to obtain the fluctuation range C at or immediately after the stable region B. For example, it is preferable to automatically detect the stable region B using a computer and then obtain it immediately. When the fluctuation range C is determined at the above timing, even if the evaluation result determined by the fluctuation range C does not satisfy the predetermined condition, for example, the seed crystal SC is pulled up and the heater output etc. is adjusted to adjust the temperature of the raw material melt L etc. It is possible to easily re-breed by changing the breeding conditions of

  Subsequently, in step S4 of FIG. 1 (B), a state regarding melting of the seed crystal SC is evaluated based on the obtained fluctuation range C. The state concerning melting of the seed crystal SC is the melting amount of the seed crystal SC, the state of the meniscus M in the seed crystal SC (diameter of the portion where the meniscus M is formed (meniscus diameter MD, neck diameter ND), seed crystal diameter-neck diameter ND)), a state relating to the ease of falling of the grown single crystal CR, a state relating to the ease of polycrystallization of the grown single crystal CR, and the like. In step S4, for example, evaluation of the state regarding melting of the above-mentioned seed crystal SC is performed by step S5 and step S6 of FIG. 1 (C).

  In step S5 of FIG. 1 (C), based on the fluctuation range C, the state regarding the ease of falling of the grown single crystal CR is evaluated. In step S5, for example, the variable width C is grown from the variable width C based on information indicating the preset relationship between the variable width C and the state relating to the ease of falling of the single crystal CR to be grown as shown in FIG. Evaluate the state regarding the ease of fall of single crystal CR. The information indicating this relationship is a condition appropriately determined according to the composition of the single crystal CR, the growth condition of the CR of the single crystal, and the like, which can be arbitrarily set, and can be prepared by preliminary experiments. In the case of the example of FIG. 3 (LT crystal), for example, in the case where the fluctuation width C (absolute value) is 0.9 g or more which is an example of predetermined information (conditions) set in advance, The crystal CR is evaluated as easily falling (falling), and when it is less than 0.9 g, the grown single crystal CR is evaluated as hard to fall (does not fall). In step S5, the evaluation of the easiness of falling of the single crystal CR to be grown (inconvenient, presence or absence of falling) may be performed quantitatively or stepwise. For example, in the case of the example of FIG. 3 or the like in step S5, the growing single crystal CR is further dropped depending on the magnitude of the amount of fluctuation C out of the predetermined value set in advance. If it is easy (not easy), it may be evaluated quantitatively or stepwise.

  Further, in step S6 of FIG. 1 (C), based on the fluctuation range C, the state regarding the ease of polycrystallization of the grown single crystal CR is evaluated. In step S6, for example, based on information indicating the relationship between the preset fluctuation width C as shown in FIG. 3 and the state regarding the ease of polycrystallization of the single crystal CR to be grown, the growth from the fluctuation width C is performed. Evaluation of the ease of polycrystallization of single crystal CR. The information indicating this relationship is a condition appropriately determined according to the composition of the single crystal CR, the growth condition of the CR of the single crystal, and the like, which can be arbitrarily set, and can be prepared by preliminary experiments. In the case of the example of FIG. 3 (LT crystal), for example, if the fluctuation range C (absolute value) is 0.5 g or less, which is an example of predetermined information (conditions) set in advance, step S6 It is evaluated that the crystal CR tends to be polycrystallized (polycrystallizes), and when it exceeds 0.5 g, it is evaluated that the grown single crystal CR is difficult to polycrystallize (not polycrystallized). In step S6, evaluation of ease of polycrystallization (inconsistencies, presence or absence of polycrystallization) of the single crystal CR to be grown may be performed quantitatively or stepwise. For example, in the case of the example of FIG. 3 or the like in step S6, the single crystal CR to be grown is more polycrystallized depending on the magnitude of the amount by which the fluctuation range C deviates from the predetermined value set in advance. It may be evaluated quantitatively or stepwise if it is easy to In the present evaluation method, it is preferable to include performing step S5 and performing step S6. Thus, it is possible to evaluate the growth state of the single crystal relating to the ease of dropping the grown single crystal and the ease of polycrystallization of the grown single crystal.

  In step S4 of FIG. 1 (B), as described above, since the fluctuation range C is an amount related to the melting amount of the seed crystal SC, the melting amount of the seed crystal SC is evaluated based on the fluctuation range C. It can also be done. In step S4 of FIG. 1B, based on the fluctuation width C, the state of the meniscus M in the seed crystal SC (the diameter of the portion where the meniscus M is formed (meniscus diameter MD, neck diameter ND), seed crystal diameter An evaluation can also be made with regard to the neck diameter ND)). In this evaluation, for example, the relationship between the fluctuation width C and the diameter of the portion where the meniscus M is formed (the meniscus diameter MD, the neck diameter ND, the seed crystal diameter-the neck diameter ND) as shown in FIG. On the basis of the information indicating, the diameter of the portion where the meniscus M is formed (the meniscus diameter MD, the neck diameter ND, and the seed crystal diameter−neck diameter ND) can be obtained from the fluctuation range C. Information indicating this relationship can be prepared by preliminary experiments and the like. As described above, since the fluctuation range C has a high linear correlation with the diameter (meniscus diameter MD, neck diameter ND) of the portion where the meniscus M is formed, the state of the meniscus M in the seed crystal SC (meniscus M It is possible to evaluate the diameter (meniscus diameter MD, neck diameter ND) of the portion in which the above is formed. And at least one of these various evaluations may not be performed.

  In addition, step S4 (steps S5 and S6) may include determining whether the growth state of the single crystal is normal or abnormal by comparing with predetermined conditions set in advance. For example, in the case of the example shown in FIG. 3 (LT crystal), in step S5 and step S6, the predetermined condition set in advance is such that the fluctuation width C (absolute value) exceeds 0.5 g and is less than 0.9 g. If the variation width C is in this range, the growth state of the single crystal CR is determined to be normal, while if the variation width C is outside this range, the growth is Because the single crystal CR is polycrystallized or the single crystal CR to be grown falls, it is determined that the growth state of the single crystal CR is abnormal. Thus, by determining whether the growth state of the single crystal CR is normal or abnormal, the growth state of the single crystal CR can be grasped more easily. The above-mentioned predetermined conditions set in advance are conditions appropriately determined according to the composition of the single crystal CR, the growth conditions of the single crystal CR, and the like, and can be set arbitrarily. The above-described predetermined conditions set in advance can be set by a preliminary experiment or the like.

  For example, the evaluation of the state relating to the melting of the seed crystal SC in step S4 may be carried out by a computer or a human being, but carrying out by a computer is from the viewpoint of work efficiency and manufacturing efficiency etc. ,preferable. Above all, the evaluation of the state concerning melting of the seed crystal SC is preferably performed automatically by a computer during growth of a single crystal. When the above evaluation is performed using a computer, the above evaluation can be performed in real time at the time of growing a single crystal CR. The evaluation of the state relating to the melting of the seed crystal SC described above can be performed, for example, using a computer by a generally known method. For example, the fluctuation range C can be obtained using the evaluation device 1 (evaluation program P) of the present embodiment described later.

  In addition, the timing of the evaluation of the state related to the melting of the seed crystal SC in step S4 is preferably during the growth of the single crystal CR, and is preferably performed before starting the pulling of the seed crystal SC. Above all, it is preferable to obtain the above evaluation during or immediately after the stable region B. For example, after using the computer to automatically detect the stable region B and obtain the fluctuation range C and obtain the fluctuation range C, It is preferable to carry it out immediately. When the above evaluation is carried out at the above timing, even if the result of the above evaluation does not satisfy the predetermined condition, for example, the seed crystal SC is pulled up and the heater output etc. is adjusted, and the growth conditions such as the temperature of the raw material melt L Can be easily and quickly retrained. In addition, when the above evaluation is performed before starting pulling of the seed crystal SC, since pulling of the crystal is not started (implemented) as shown in Patent Document 1, the crystal formed at the tip of the seed crystal SC is There is no need to dissolve it.

  As described above, in the evaluation method of the present embodiment, the seed crystal SC is brought into contact with the raw material melt L in which the raw material is melted, and the seed crystal SC is raised while rotating the seed crystal SC to grow single crystal CR. Evaluation of the state concerning melting of the seed crystal SC based on the fluctuation width C of the measured weight D1 in the measured weight D1 of the seed crystal SC measured when the seed crystal SC melts by contacting the SC with the raw material melt L do. In this configuration, since the above evaluation is performed based on the fluctuation range C which can be determined quantitatively, it is possible to accurately evaluate the state regarding the melting of the seed crystal SC. In this evaluation method, for example, the evaluation on the state regarding melting of the seed crystal SC such as the state regarding the ease of falling of the growing single crystal CR, the state regarding the ease of polycrystallization of the growing single crystal CR, etc. Can be done. Further, according to the present evaluation method, it is possible to suppress the variation in the melting state of the seed crystal SC and to optimize the melting state of the seed crystal SC by accurately evaluating the state related to the melting of the seed crystal. As a result, it is possible to suppress the growth failure of the single crystal such as the falling of the grown crystal and the polycrystallization which occur depending on the state concerning the melting of the seed crystal SC, and to achieve the significant improvement of the productivity and the cost reduction. In addition, the present evaluation method does not have to improve the device or the device which requires high cost, and can be implemented simply and at low cost.

  In the above description, although the example of performing the present evaluation method by measuring the weight of the seed crystal SC in step S2 has been described, the present evaluation method does not require measurement of the seed crystal SC in step S2. Alternatively, the fluctuation range C may be obtained by step S3 using measured weight data of the existing seed crystal SC as shown in FIG. 3, and the state of melting of the seed crystal may be evaluated by step S4.

  Moreover, the above-mentioned example is an example and this evaluation method is not limited to the above-mentioned example. For example, the present evaluation method may include notifying in step S14 which will be described later in the section “Method of Manufacturing Single Crystal”. Further, in the above description, the present evaluation method has been described focusing on the example of the crystal of LT shown in FIGS. 2 and 3, but the present evaluation method is not limited to the above example, and crystals other than the above example It is obvious that it is applicable in.

[Evaluation equipment / evaluation program]
Next, an evaluation apparatus of the growth state of single crystal (hereinafter referred to as “evaluation apparatus”) and an evaluation program of the growth state of single crystal (hereinafter referred to as “evaluation program”) of the present embodiment will be described. In addition, about the structure similar to the structure mentioned above, the description is abbreviate | omitted or simplified suitably, and the applicable structure is suitably applied also by this evaluation apparatus and evaluation program.

  FIG. 4: is a figure which shows the evaluation apparatus of this embodiment notionally. The evaluation apparatus and the evaluation program of the present embodiment can execute the above-described evaluation method of the present embodiment.

  The evaluation apparatus 1 of this embodiment brings the seed crystal SC into contact with the raw material melt L obtained by melting the raw material, and raises the seed crystal SC while raising the single crystal CR while rotating the seed crystal SC. Evaluation to evaluate the state concerning melting of the seed crystal SC based on the fluctuation width C of the measured weight D1 in the measured weight D1 of the seed crystal SC measured when the seed crystal SC melts by contacting with the melt L The unit 3 is provided.

  The evaluation device 1 includes, for example, a CPU, a main memory, a storage device (storage unit 2) such as a hard disk, a communication device performing communication by wire or wireless, an input device such as a keyboard, a touch panel or a mouse, a display device such as a display, a sequencer It is comprised by the computer provided with etc. The evaluation device 1 executes various processes in accordance with the program stored in the storage unit 2. This program includes, for example, the evaluation program P of the present embodiment.

  In the evaluation program P of this embodiment, the seed crystal SC is brought into contact with the raw material melt L in which the raw material is melted, and the seed crystal SC is raised while rotating the seed crystal SC to grow a single crystal CR. Evaluation of the state concerning melting of the seed crystal SC based on the fluctuation width C of the measured weight D1 in the measured weight D1 of the seed crystal SC measured when the seed crystal SC melts by contacting the SC with the raw material melt L (Step S1 in FIG. 1A) is executed. The process of step S1 by the evaluation program P is the process of steps S3 to S6 described above. The evaluation program P may be used separately from the evaluation device 1 of the present embodiment. For example, the evaluation program P of the present embodiment may be provided by being stored (recorded) in a computer readable storage medium (recording medium).

  In the evaluation device 1 of the present embodiment, the evaluation unit 3 executes the main evaluation program P stored in the storage unit 2 to carry out a process (step S1) for evaluating a state related to the melting of the seed crystal SC. The evaluation device 1 performs, for example, the processing from step S3 to step S6 described above. In addition, information necessary for the implementation of the present embodiment, such as preset conditions or values used for the above-described evaluation and the measurement weight D1 are stored in the storage unit 2.

  Thus, the evaluation device 1 and the evaluation program P of the present embodiment can implement the evaluation method of the present embodiment. In this configuration, since the above evaluation is performed based on the fluctuation range C which can be determined quantitatively, it is possible to accurately evaluate the state regarding the melting of the seed crystal SC. The evaluation apparatus 1 and the evaluation program P of the present embodiment can be applied to the existing general single crystal manufacturing apparatus after the addition, have high versatility, and can be suitably used. Further, according to the evaluation apparatus 1 and the evaluation program P of the present embodiment, the dispersion of the melting state of the seed crystal is suppressed by evaluating the melting state of the seed crystal with high accuracy, and the melting state of the seed crystal is optimized. As a result, it is possible to suppress the growth defects of the single crystal such as the falling and polycrystallization of the grown crystal, which occur depending on the state concerning melting of the seed crystal, and to achieve the significant improvement of the productivity and the cost reduction. be able to. Further, the evaluation device 1 and the evaluation program P of the present embodiment do not have to improve the device or the device that requires high cost, and can be implemented easily and at low cost.

  In the above description, although the evaluation apparatus 1 and the evaluation program P have described the example of performing the processing from step S3 to step S6, the present invention is not limited to this example, and one of the processing from step S3 to step S6 The above process may not be performed. In addition, the evaluation device 1 and the evaluation program may carry out a process of displaying the evaluation result such as step S4 (step S5 and step S6), or the evaluation device 1 may perform the process of step S4 (step S5 and step S6) or the like. A display device may be provided to display information such as evaluation results, and configurations (functions) such as the identification processing unit 44, the notification instruction unit 43, and the notification unit 32 of the single crystal manufacturing apparatus 20 of the present embodiment described later. Or the same configuration (function) as the control unit 31 of the single crystal manufacturing apparatus 20.

[Method of producing single crystal]
Next, the method for producing a single crystal of the present embodiment (hereinafter, referred to as “production method”) will be described. FIG. 5 is a flowchart showing an example of the present manufacturing method. In the present manufacturing method, the seed crystal SC is brought into contact with the raw material melt L obtained by melting the raw material, and the seed crystal SC is rotated and raised to grow the crystal CR (step S10). Evaluating the evaluation of the state regarding melting of the seed crystal SC (step S1). In addition, the description is suitably abbreviate | omitted or simplified about the structure similar to the structure mentioned above, and the applicable structure is suitably applied also with the manufacturing method of this single crystal.

  Step S10 is performed, for example, by a known Czochralski method. The type and size of the single crystal to be grown are not particularly limited, and are arbitrary. In the present step S10, the shoulder and the straight body in the single crystal are grown.

  In step S10 of the present manufacturing method, for example, first, in step S11, the seed crystal SC is brought into contact with the raw material melt L.

  Subsequently, step S1 (from step S2 to step S4) of the above-described present evaluation method is performed to evaluate the state relating to the melting of the seed crystal SC. The measurement of the weight of the seed crystal SC in step S2 is started before step S11. As described above, this step S1 is preferably performed before starting the above-described timing, for example, the pulling of the seed crystal SC.

  Subsequently, in step S12, a predetermined process set in advance is performed according to the result of the evaluation. Step S12 may be performed by a human or a computer (control device) or the like, but is preferably performed automatically by a computer or the like. Step S12 is automatically performed by, for example, a single crystal manufacturing apparatus 20 described later. In step S12, for example, it is determined whether the evaluation result satisfies a predetermined condition set in advance, and a predetermined process set in advance is performed according to the determination result. In step S12, for example, in step S13, as described above, it is determined whether or not the evaluation result in step S4 is evaluated as "abnormal".

  If it is determined that the evaluation result in step S4 is evaluated as "normal" (NO in step S13), pulling up of the seed crystal SC is started in step S16, and the seed crystal SC is raised while rotating in step S17. To grow single crystal CR. Thereby, good quality single crystal CR can be manufactured.

  When it is determined that the evaluation result in step S4 is evaluated as "abnormal" (YES in step S13), information indicating the evaluation result is notified in step S14. As a result, the worker can quickly grasp the growing state, and as a result, the worker can quickly carry out processing (cancellation of the growth) on single crystal growth, and the growth state is normal. You can also confirm that there is. This notification is automatically performed by control of a computer device or the like. The means (method) of the notification is not particularly limited and is arbitrary. For example, this notification may be output to a display device such as a display of a predetermined message indicating that the evaluation result is abnormal, transmission of an electronic mail to a predetermined e-mail address of a predetermined message, a predetermined telephone of a predetermined message This is performed by notifying by output to (mobile phone), output of predetermined voice, or the like. This notification may be performed by outputting a drive pattern (lighting or blinking) of a lighting device (alarm device) such as a lamp (emergency light) or a predetermined sound (for example, a warning). In addition, the manufacturing method of the single crystal of this embodiment does not need to be equipped with step S14.

  Subsequently, in step S15, growth of the single crystal is stopped. Step S15 is preferably performed automatically. For example, step S15 automatically performs a process of pulling up the seed crystal SC brought into contact with the raw material melt L from the raw material melt L. Thus, unnecessary processing (work) can be suppressed. For example, in step S15, it can implement by controlling the rotation pulling-up axis | shaft 28 of the single-crystal manufacturing apparatus 20 of this embodiment demonstrated later, for example.

  Subsequently, the process returns to step S11, and the process of bringing the seed crystal SC into contact with the raw material melt L is performed again. As described above, for example, the seed crystal SC can be pulled up and the heater output and the like can be adjusted to change the growth conditions such as the temperature of the raw material melt L, and the regrowth can be performed easily and quickly. Further, in this case, since pulling up of the crystal is not started (implemented) as shown in Patent Document 1, it is not necessary to dissolve the single crystal CR formed at the tip of the seed crystal SC. In addition, in the manufacturing method of the single crystal of this embodiment, it is not necessary to perform this process.

  As described above, since the method of producing a single crystal of the present embodiment includes the evaluation method of the present embodiment, variations in the melted state of the seed crystal are suppressed by accurately evaluating the state related to the melting of the seed crystal, It is possible to optimize the melting state of the seed crystal, and as a result, suppress the growth failure of the single crystal such as the falling of the grown crystal and the polycrystallization, which occur depending on the state related to the melting of the seed crystal, It is possible to improve the quality and reduce the cost. In addition, the method of manufacturing a single crystal according to the present embodiment can be implemented easily and at low cost without the need for improvement of the device or the device which requires high cost.

  In the above description, although the present manufacturing method shows an example in which the present evaluation method is carried out when growing a single crystal, the present invention is not limited to this example. For example, growth conditions (examples obtained in advance by the present evaluation method) The seed crystal SC is brought into contact with the raw material melt L using conditions of fluctuation range C, and the seed crystal SC is raised while rotating to grow the crystal CR (by the rotation pull method such as the Cz method) The single crystal CR may be manufactured by growing a single crystal). That is, that the present manufacturing method includes the evaluation of the state relating to the melting of the seed crystal SC by the evaluation method of the present embodiment (step S1) also means that the evaluation result of step S1 is used. For example, in the present manufacturing method, the growth conditions (e.g., the temperature of the raw material melt L, etc.) are adjusted so as to adjust the fluctuation range C so that the growth conditions become (determined) growth conditions obtained by performing the present evaluation method in advance. The seed crystal SC is brought into contact with the raw material melt L and raised while rotating the seed crystal SC to grow the crystal CR (growing a single crystal by a rotation pulling method such as the Cz method) By this method, single crystal CR may be manufactured, or a single crystal after growth may be selected (sorted) based on the condition (sorting condition) of fluctuation range C determined based on the evaluation result, single It may be a method of manufacturing the crystal CR, etc. In the example of these present manufacturing methods, it is not necessary to evaluate the step S1.

  Such a method for producing a single crystal according to the present embodiment can be carried out, for example, by the single crystal production device 20 according to the present embodiment to be described next, but a single crystal production device that can be used is this example. It is not limited and is optional.

[Single crystal manufacturing equipment]
Next, the single crystal production apparatus of the present embodiment will be described. FIG. 6: is a figure which shows notionally the single-crystal manufacturing apparatus of this embodiment. In addition, the description is suitably abbreviate | omitted or simplified about the structure similar to the structure mentioned above, and the applicable structure is suitably applied also to this single-crystal manufacturing apparatus.

  The single crystal production apparatus 20 of the present embodiment is an apparatus for bringing the seed crystal SC into contact with the raw material melt L obtained by melting the raw material in the crucible 10, and raising the single crystal CR while rotating the seed crystal SC to grow single crystals CR. The method for producing a single crystal of the present embodiment described above can be implemented, including the evaluation device 1 of the present embodiment described above. That is, the single crystal production apparatus 20 may be configured to include the evaluation apparatus 1 (evaluation program P) of the present embodiment in a known single crystal production apparatus.

  The single crystal manufacturing apparatus 20 includes, for example, a crucible 10, a crucible table 21, a heat insulating material 22, a refractory 23, a heating unit 24, a power supply 25, a support 26, a chamber 27, and a rotating pulling shaft 28. And a lifting and lowering shaft drive unit 29, a weight measurement unit 30, a control unit 31, and a notification unit 32.

  The crucible 10 is a metal container for storing and holding the raw material MT and growing a single crystal CR. The heating unit 24 heats the crucible 10 to melt the raw material MT. The raw material MT is filled in the crucible 10 in advance. The heating unit 24 is an induction coil 35 that heats the crucible 10 and the after heater 34. The power supply 25 supplies high frequency power to the induction coil 35. The power supply 25 is connected to the control unit 31, and the control unit 31 controls the high frequency power supplied to the induction coil 35. Thus, the heating unit 24 can heat the crucible 10 at a predetermined temperature to melt the raw material. Although the above-mentioned single crystal manufacturing apparatus 20 shows an example of a high frequency heating method (high frequency induction heating furnace) using an induction coil, it may be a heating method using a resistance heater instead of the high frequency heating method.

  The crucible 10 is placed on a crucible table 21. A heat insulating material 22 is provided to surround the crucible 10 and the crucible table 21. In addition, a refractory 23 is provided on the outside of the heat insulating material 22 and covers the entire circumference of the heat insulating material 22 and the crucible 10. An induction coil 35 is disposed outside the side surface of the refractory 23. In FIG. 6, the central portion 35a of the induction coil 35 is indicated by a broken line so that the internal structure around the crucible 10 can be seen. The refractory 23 on the outside of which the induction coil 35 is provided is mounted on the support 26. Also, a chamber 27 covers the periphery of the induction coil 35. Further, above the crucible 10, a rotating and pulling shaft 28 is provided. The rotating and pulling shaft 28 holds the seed crystal SC, and raises and lowers the seed crystal SC while rotating it. The rotating and pulling shaft 28 is in the shape of a rod extending in the vertical direction (Z direction). The rotating pulling shaft 28 has a seed crystal holding portion 38 holding the seed crystal SC at its lower end. The rotational pull-up shaft 28 can rotate around the vertical axis (Z-axis) and move up and down in the + Z direction and the −Z direction by the drive of the rotational pull-up shaft drive unit 29. The rotating and pulling shaft drive unit 29 is connected to the control unit 31, and the drive (operation) thereof is controlled by the control unit 31. A weight measurement unit 30 is provided above the rotating and pulling shaft 28 (in the + Z direction). The weight measurement unit 30 is, for example, a weight sensor such as a load cell. The weight measurement unit 30 measures the weight of the seed crystal SC and the single crystal CR being grown. The weight measurement unit 30 measures the weight during one rotation of the growing single crystal CR with time. The weight measurement unit 30 is connected to the control unit 31 and controls the measurement result of the measured weight of the seed crystal SC and the single crystal CR being grown (a signal indicating the measurement result, eg, measurement weight data of FIG. 2). Output to A power supply 25 and a control unit 31 are provided outside the periphery of the chamber 27. Further, in FIG. 6, as related components, a seed crystal SC, a single crystal CR, and a crystal raw material MT (raw material melt L) are shown.

  The notification unit 32 executes the notification in step S14 described above based on the command of the notification instruction unit 43 of the control unit 31. For example, the notification unit 32 displays the processing result of the evaluation device 1 (the value of the fluctuation range C, the value of the stable region B, the time or the time), the various evaluation results by the evaluation device 1, the display of specific information such as predetermined messages The output to the device, transmission of an E-mail to a predetermined e-mail address such as the specific information, the output of the specific information to a predetermined terminal, a portable terminal, a telephone (mobile phone), the output of a predetermined voice, etc. Make a notification. The notification unit 32 may be performed by outputting a drive pattern (lighting or blinking) of a lighting device (alarm device) such as a lamp (emergency light) or a predetermined sound (for example, a warning).

  The control unit 31 controls each unit of the single crystal manufacturing apparatus 20. The control unit 31 includes the evaluation device 1 of the present embodiment, and controls each part of the single crystal production device 20 based on the evaluation result of the evaluation device 1 of the present embodiment. The control unit 31 includes, for example, a storage unit 2, a heating control unit 41, a drive control unit 42, the evaluation device 1 of the present embodiment described above, a notification instructing unit 43, and a specifying processing unit 44. The control unit 31 includes, for example, a CPU, a main memory, a storage device (storage unit 2) such as a hard disk, a communication device performing communication by wire or wireless, an input device such as a keyboard, a touch panel or a mouse, and a display device such as a display. It consists of a computer, sequencer, etc. The control unit 31 executes various processes in accordance with the program stored in the storage unit 2. This program includes the evaluation program P (see FIG. 5) of the above-described embodiment. The evaluation device 1 may be configured by a computer device other than the control unit 31. Further, the control unit 31 may be used alone (provided) as a control device for controlling a growth apparatus for growing a single crystal by a rotational pulling method. That is, the control unit 31 can be applied as a single unit to a known single crystal growth apparatus.

  The heating control unit 41 controls the temperature of the heating unit 24. The heating control unit 41 controls the power supply 25 to control the high frequency power supplied to the induction coil 35, thereby controlling the temperature at which the heating unit 24 heats the crucible 10. The drive control unit 42 controls the rotation and elevation of the rotating and pulling shaft 28 by controlling the driving (operation, for example, the rotational speed, the elevation and lowering speed) and the like of the rotating and pulling shaft drive unit 29.

  In the evaluation device 1, as described above, the evaluation unit 3 evaluates the state related to the melting of the seed crystal SC based on the evaluation program P of the present embodiment.

  The notification instruction unit 43 causes the notification unit 32 to execute notification in accordance with the evaluation result of the evaluation device 1. The notification instruction unit 43 causes the notification unit 32 to automatically execute the process (notification) of step S14 of FIG. 5 according to the evaluation result of the evaluation device 1. For example, according to the configuration (aspect) of the notification unit 32, the notification instruction unit 43 processes the evaluation device 1 (the value of the fluctuation range C, the value and time of the stable region B, various evaluation results by the evaluation device 1) Output of specific information to a display device such as a display of a predetermined message, transmission of an E-mail to a predetermined e-mail address, Output of a predetermined terminal such as the above specific information, a portable terminal or a telephone (mobile phone), predetermined The informing unit 32 is made to output a voice of the above, a drive pattern (lighting, blinking) of a lighting device (alarm device) such as a lamp (emergency light), or outputting a predetermined sound (for example, a warning).

  The identification processing unit 44 executes a predetermined process set in advance in accordance with the evaluation result of the evaluation device 1. The identification processing unit 44 determines, for example, whether the above evaluation result satisfies a predetermined condition set in advance, and performs a predetermined process set in advance according to the determination result. The identification processing unit 44 automatically performs a predetermined process set in advance, for example, by executing the process of step S12 (step S13 to step S16) of FIG. 5 described above. For example, when the evaluation result is evaluated as “abnormal”, for example, as in step S13 described above, the specific processing unit 44 stops the growth of the single crystal and is evaluated as “normal”. In the case, processing such as starting pulling up of the seed crystal SC is performed.

  The single crystal production apparatus 20 can carry out the method for producing a single crystal of the present embodiment shown in FIG. 5 with the above-described configuration, and produce a good quality single crystal CR.

  As described above, since the apparatus for producing a single crystal of the present embodiment can carry out the evaluation method of the present embodiment, the condition relating to the melting of the seed crystal SC is accurately evaluated to produce a high quality single crystal CR. can do. The apparatus for manufacturing a single crystal according to the present embodiment can be implemented easily and at low cost without the need for improvement of the apparatus or the apparatus requiring high cost.

  As described above, the method of evaluating the growth state of the single crystal, the evaluation apparatus, and the evaluation program of the present embodiment can accurately evaluate the state related to the melting of the seed crystal.

  In addition, since the method and apparatus for manufacturing a single crystal according to the present embodiment includes the above-described evaluation method or apparatus, it is possible to suppress variations in the melting state of the seed crystal by accurately evaluating the state related to melting of the seed crystal. And optimize the melting state of the seed crystal, and as a result, suppress the growth failure of the single crystal such as the falling of the grown crystal and the polycrystallization which occur depending on the state related to the melting of the seed crystal, Productivity and cost reduction can be achieved. In addition, since the method of producing a single crystal of the present embodiment can stably control the melting of the seed crystal by adjusting the fluctuation range C quantitatively, high quality single crystal can be easily and stably It can be manufactured.

  Further, according to the evaluation method, evaluation apparatus, evaluation program, single crystal production method, and single crystal production apparatus of single crystals of the present embodiment, single crystals such as lithium tantalate and lithium niobate are particularly preferred. Also, in the production of a large single crystal having a large size, a remarkable effect is exerted as compared with the conventional method, and it is possible to obtain a high single crystallization rate, thereby achieving significant improvement in productivity and cost reduction. In addition, the evaluation method, the evaluation apparatus and the evaluation program of the growth state of the single crystal of the present embodiment can be implemented simply and at low cost without the need for improvement of the apparatus or apparatus requiring high cost. it can.

  Hereinafter, the present invention will be described in detail based on examples and comparative examples, but the present invention is not limited to the examples.

Example 1
Using a high frequency induction heating furnace as shown in a part of FIG. 6, LT single crystals were grown under various conditions, and the investigation results shown in FIG. 3 were obtained. The LT single crystal is grown by charging the LT raw material in an Ir crucible and immersing the tip of the seed crystal in the raw material melt after melting the raw material and pulling it up while rotating, diameter φ 6 inches, straight barrel length 120 mm LT single crystals were obtained. The weight of the obtained single crystal was about 20 kg. In addition, the seed crystal whose diameter is 10 mm was used for the seed crystal.

  From the obtained results, as described above, it was confirmed that the evaluation method of the present embodiment can accurately evaluate the state regarding melting of the seed crystal. Moreover, it was confirmed that the method of producing a single crystal of the present embodiment can stably produce high quality single crystals.

Example 2
The output operation of the high-frequency induction heating furnace is performed so that the melting amount (variation range C, absolute value) of the tip of the seed crystal exceeds 0.5 g which is the variation range determined by the evaluation method of this embodiment and is less than 0.9 g. Then, the temperature of the raw material melt L was adjusted to grow LT single crystals. Except for this, LT single crystal was grown under the same conditions as in Example 1 to obtain a LT single crystal.

  As a result of performing 50 runs repeatedly under the same conditions, polycrystal generation of the grown crystal was 2 runs. Among the 50 runs of growth, the number of single crystals obtained was 47, and the single crystallization rate was 94% because there were defects other than the occurrence of polycrystal generation.

  From the obtained results, it was confirmed that the conditions obtained by the evaluation method of the present embodiment can stably produce single crystals excellent in quality.

[Example 3]
In the high frequency induction heating furnace, the seed crystal front end melting amount (variation range C, absolute value) is 0.9 g to 1.1 g which is a condition under which polycrystallization is difficult to be determined by the evaluation method of this embodiment. The output operation was performed, the temperature of the raw material melt L was adjusted, and LT single crystal growth was performed. An LT single crystal was obtained under the same conditions as in Example 1 except for the above to obtain a LT single crystal.

  As a result of repeating 50 runs of LT crystals of φ 6 inch, straight barrel length 120 mm, and crystal weight of about 20 kg under similar conditions, there was no occurrence of 1 run of polycrystals of grown crystals, but from the seed crystal tip The fall was 15 run. Since defects other than the drop from the tip of the seed crystal occurred, the number of single crystals obtained in the 50 runs of growth was 33, and the single crystallization rate was 66%.

  From the obtained results, it was confirmed that the conditions obtained by the evaluation method of the present embodiment have high accuracy.

Comparative Example 1
The melting amount (variation range C) of the tip of the seed crystal is not determined, and the meniscus state of the tip of the seed crystal to be formed is visually observed based on the image taken by the camera installed in the observation window at the top of the high frequency induction heating furnace The crystal was grown under the same conditions as in Example 1 except that the output operation of the high-frequency induction heating furnace was performed while checking and the temperature was adjusted so as to reduce the meniscus diameter, to obtain an LT single crystal.

  As a result of repeating 50 runs of LT crystals having a diameter of 6 inches, a straight barrel length of 120 mm, and a crystal weight of about 20 kg under the same conditions, 50 generations of polycrystalline crystals were generated. The drop from the seed crystal tip was 9 run. Among the 50 runs of growth, the number of single crystals obtained was 23 and the single crystallization rate was 46% because of the occurrence of defects other than polycrystal generation and crystal fall.

  From the obtained results, it was confirmed that the conventional single crystal manufacturing method has many variations in quality, and there are many falling and polycrystallization of the grown single crystal.

  As mentioned above, it is confirmed from the Example and the comparative example that the evaluation method of this embodiment can evaluate the state regarding melt | dissolution of a seed crystal precisely.

  As mentioned above, although the embodiment of the present invention was described, the technical scope of the present invention is not limited to the above-mentioned embodiment. It is apparent to those skilled in the art that various changes or modifications can be added to the above-described embodiment. Moreover, the form which added such a change or improvement is also contained in the technical scope of this invention. In addition, one or more of the requirements described in the above-described embodiment and the like may be omitted. Further, the requirements described in the above-described embodiment and the like can be combined as appropriate. In addition, the disclosures of all the documents cited in the above-described embodiments and the like are incorporated as part of the description of the text as far as the laws and regulations permit. In addition, the order of each process (step, step) shown in the present embodiment can be realized in any order, as long as the output of the previous process is not used in the subsequent process. Further, even if the operations in the above-described embodiment are described using “first”, “next”, “following” and the like for convenience, it is not essential to carry out in this order.

  The present invention, as described above, is effective in producing a single crystal, particularly, lithium tantalate and lithium niobate single crystal, using the Cz method. According to the present invention, by determining the melting amount of the front end of the seed crystal by the weight difference at the time of melting, polycrystallization and falling from the front end of the seed crystal are suppressed, and in particular, lithium tantalate, lithium niobate, etc. It is possible to obtain a large oxide single crystal at a high single crystallization rate, and a significant improvement in productivity and cost reduction can be achieved.

DESCRIPTION OF SYMBOLS 1 ... Evaluation apparatus 2 ... Storage part 3 ... Evaluation part B ... Stability area C ... Fluctuation width L ... Raw material melt M ... Meniscus N ... Neck part P ... Evaluation program 10 ... Crucible (坩 堝)
20: single crystal manufacturing apparatus 21: crucible base 22: heat insulating material 23: refractory 24: heating unit 25: power supply 26: support base 27: chamber 28: rotation pulling shaft 29: rotation pulling shaft drive unit 30: weight measuring unit 31 ... control unit 32 ... notification unit 34 ... after heater 38 ... seed crystal holding unit 41 ... heating control unit 42 ... drive control unit 43 ... notification instructing unit 44 ... identification processing unit CR ... single crystal (crystal)
D1 Measured weight MD Meniscus diameter MT Raw material ND Neck diameter SC Seed crystal

Claims (12)

  The seed crystal is brought into contact with a raw material melt obtained by melting the raw material, and the seed crystal is raised by rotating the seed crystal to grow a single crystal by bringing the seed crystal into contact with the raw material melt. The evaluation method of the growth state of the single crystal which evaluates the state regarding melt | dissolution of the said seed crystal based on the fluctuation range of the said measurement weight in the measured weight of the said seed crystal measured when melt | dissolving.   The evaluation method according to claim 1, comprising measuring the weight of the seed crystal.   The evaluation method according to claim 1, further comprising: determining the fluctuation range based on a measured weight of the seed crystal measured when the seed crystal is melted. The evaluation of the state concerning melting of the seed crystal is
The evaluation method according to any one of claims 1 to 3, further comprising evaluating the melting amount of the seed crystal based on the fluctuation range. The evaluation of the state concerning melting of the seed crystal is
Evaluating the ease of fall of the grown single crystal based on the fluctuation range;
The evaluation method according to any one of claims 1 to 4, comprising: evaluating the susceptibility of the grown single crystal to be polycrystallized on the basis of the fluctuation range. The fluctuation range is
A value when the measured weight immediately after bringing the seed crystal into contact with the raw material melt is higher than the actual weight of the seed crystal;
The difference between the measured weight and the value at the time of a stable region where the fluctuation per hour of the measured weight immediately after bringing the seed crystal into contact with the raw material melt is a predetermined value or less. The evaluation method according to any one of the above.   The evaluation method according to any one of claims 1 to 6, wherein the single crystal is lithium tantalate or lithium niobate. The single crystal is lithium tantalate,
When the fluctuation range is more than 0.5 g and less than 0.9, it is evaluated that the grown single crystal does not fall and does not polycrystallize in the state related to melting of the seed crystal. The evaluation method according to claim 7, comprising Bringing a seed crystal into contact with a raw material melt obtained by melting the raw material, and raising the seed crystal while rotating to grow the crystal;
A method for producing a single crystal, comprising: evaluating a state related to melting of the seed crystal by the evaluation method according to any one of claims 2 to 8.   The seed crystal is brought into contact with a raw material melt obtained by melting the raw material, and the seed crystal is raised while rotating the seed crystal to grow a single crystal by contacting the seed crystal with the raw material melt. An evaluation device of a growth state of a single crystal, comprising: an evaluation unit that evaluates a state related to melting of the seed crystal based on a fluctuation range of the measured weight in the measured weight of the seed crystal measured when is melted. On the computer
The seed crystal is brought into contact with a raw material melt obtained by melting the raw material, and the seed crystal is raised while rotating the seed crystal to grow a single crystal by contacting the seed crystal with the raw material melt. A program for evaluating the growth state of a single crystal, which executes a process of evaluating a state related to melting of the seed crystal based on the fluctuation range of the measured weight in the measured weight of the seed crystal measured when W melts. . A seed crystal is brought into contact with a raw material melt obtained by melting a raw material in a crucible, and the seed crystal is rotated and raised to grow a single crystal.
Said crucible,
A heating unit which heats the crucible and melts the raw material;
A rotating pulling shaft that holds the seed crystal and raises and lowers the seed crystal while rotating the seed crystal;
A weight measurement unit that measures with time the weight of the seed crystal and the weight of a growing single crystal containing the seed crystal;
A heating control unit that controls the temperature of the heating unit;
A drive control unit that controls rotation and elevation of the rotation pulling unit;
11. The evaluation device according to claim 10, wherein a state related to melting of the seed crystal is evaluated using the measurement result of the weight measurement unit;
A specific processing unit that executes a predetermined process preset according to the evaluation result of the evaluation device;
An apparatus for producing a single crystal, comprising:

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