JP2021127275A - Single crystal growth device, single crystal growth method, and single crystal - Google Patents

Abstract

To provide a single crystal growth device capable of safely and reliably melting a material single crystal in a crucible at high efficiency, a single crystal growth method, and a single crystal produced by the device and the method.SOLUTION: A single crystal growth device 100 is provided. The device 100 comprises a crystal growth furnace 1 including a rotation mechanism 20 for rotating a crucible 8 and a heater 10 for heating the crucible 8. The crucible 8 houses at least any of molten liquid L of silicon and a raw material of the molten liquid L, and the rotation mechanism 20 is constituted so that the crucible 8 can intermittently rotate. In a step of melting a silicon raw material in the crucible and obtaining the molten liquid L before single crystal growth, vibration is given to the raw material by rotary-driving the crucible 8 accompanied with rapid start and rapid stop, thereby the raw material affixed to an inner wall of the crucible is shaken off to a bottom face of the crucible or in the molten liquid L.SELECTED DRAWING: Figure 1

Description

The present invention relates to the technical field of semiconductor manufacturing, and more specifically to a single crystal growth apparatus, a single crystal growth method, and a single crystal of silicon as a semiconductor material.

In the single crystal growth apparatus and single crystal growth method, the CZ method (Czochralski method) is generally used for the production of materials for semiconductor silicon wafers and material single crystals that serve as material wafers for silicon single crystal solar cells. The MCZ method in which a magnetic field is applied has been used.

In both the CZ method and the MCZ method, a polycrystalline raw material of silicon is filled in a quartz turret, power is supplied to the heater in a reduced pressure atmosphere using argon gas as an inert gas, and a large amount is provided in the protective carbon rug. While setting and rotating a quartz crucible filled with crystal raw materials, heat and melt it from the outside of the ruts using a carbon heater to completely melt the raw material polycrystalline, and then melt the seed crystals suspended on the pull-up shaft. This is a crystal growth method in which the seed crystal is immersed in the liquid surface and pulled upward while rotating the seed crystal while adjusting the temperature. As one of the prior arts of a method for melting polycrystalline silicon, for example, Patent Document 1 listed below can be mentioned.

In paragraph (0012), as yet another object of the invention, Patent Document 1 can efficiently dissolve the raw material in the crucible without forming a bridge even when the cut rod is loaded in the crucible. It is described to provide a method for melting polycrystalline silicon. Further, in paragraph (0015), the advantage of the additional charge of melting the polycrystalline silicon initially loaded in the crucible and then adding a new polycrystalline silicon in the crucible from above to dissolve it is described. It is stated that the amount of polycrystalline silicon initially loaded is reduced and additional charging is performed because of the bridging of the raw material. In the patent document 1, it is described in paragraph (0019) that as the silicon raw material to be initially loaded in the crucible, rod-shaped polycrystalline silicon, that is, one containing a cut rod is preferable. Further, since the cut rod has good thermal conductivity, when the present invention is applied to melting the raw material in a state where the cut rod is loaded, the cut rod is preferentially melted by heating from the bottom of the rubbish by the second heating means. , It is described that the melting time as a whole becomes very short due to the increase in the temperature at the center of the rutsubo.

Here, to summarize the above, the risk of bridging is reduced by reducing the amount of polycrystalline silicon to be initially loaded and performing additional charging. Furthermore, it is recommended to use rod-shaped polycrystalline silicon with good thermal conductivity to increase the bulk specific density and reduce the risk of bridging. Further, it is described that the melting time is reduced by heating from the bottom of the crucible by the second heating means and optimizing the power supply ratio thereof.
That is, it is intended to use rod-shaped polycrystalline silicon having good thermal conductivity, thereby reducing the risk of bridging due to an increase in bulk specific density and a decrease in the initial charge amount due to additional charging.

However, originally, even if the initial charge is raised in a mountain shape from the upper end of the crucible opening and charged, the melting level after melting is lower than the crucible opening by less than 70% in the depth direction. Therefore, the charging efficiency is poor. If it is raised in a mountain shape and charged, it will be in a state where the bridge is applied during melting, and once the bridge is applied, it will be difficult to dissolve, and even if the bridge can be dissolved, the liquid will splash when the bulk raw material silicon falls at the same time. In addition, there was a problem that the raw material silicon was welded to the wall surface of the rutsubo due to liquid splashing, and the raw material silicon was welded to each other.

Japanese Patent No. 6452098

As described above, the bridge countermeasure in the prior art could not avoid the bridge unless the initial charge amount was lowered and the additional charge was applied. Further, it is necessary to adjust the heater power distribution and the like as described in Patent Document 1.
On the other hand, conventionally, in order to grow a seed crystal stably, a gentle start and a smooth movement at a constant speed have been required for the rotation of the crucible.

Since the process of melting the raw material single crystal in the rutsubo is followed by the process of growing the seed crystal, the driving mechanism for rotating the rutsubo that emphasizes the stable growth of the seed crystal is also used in the process of melting the raw material single crystal. It is used as it is.

However, since the raw material crystal is not in the form of particles and is an aggregate of agglomerates, it is not uniformly agitated by the rotational drive of the crucible, and the melting mode of each agglomerate is also non-uniform. Therefore, the raw material polycrystalline near the inner wall surface of the crucible may stick to the inner wall surface of the crucible. Further, other lumps may be fixed one after another to the lumps fixed to the inner wall of the crucible, forming a gap between the lumps and the melting surface and connecting them in a bridge shape (see FIG. 2). In such a situation, it becomes necessary to further raise the heating temperature by the heater, which lowers the processing efficiency. In addition, when a lump that is considerably separated from the melt surface suddenly falls into the melt, The liquid splashes and adheres to the in-furnace parts such as the flow pipe, shortening the life of the single crystal growth apparatus. In the worst case, the silicon melt adhering to the surface of the parts in the furnace may fall on the growing single crystal and produce a defective product.

The present invention has been made in view of the above problems in the prior art, and is a single crystal growth apparatus, a single crystal growth method, and a single crystal growth method capable of melting a raw material single crystal in a rutsubo with high efficiency and safety and reliability. The main purpose is to provide a single crystal produced by the above-mentioned equipment and method.

According to the first aspect of the present invention, a single crystal growth apparatus is provided.
The apparatus includes a crystal growth furnace including a rotating mechanism for rotating the crucible and a heater for heating the crucible.
The crucible contains at least one of a silicon melt and a raw material for the melt.
The rotation mechanism is configured to allow intermittent rotation of the crucible.

Further, according to the second aspect of the present invention, a single crystal growth method using a single crystal growth furnace is provided, and the method is described.
A step of heating the crucible while intermittently rotating a crucible containing a silicon raw material to melt the raw material.
A step of suspending a seed crystal, immersing it in a melt in a crucible obtained by melting the raw material, and pulling up the seed crystal while rotating the crucible to grow the seed crystal.
To be equipped.

Further, according to the third aspect of the present invention, the single crystal obtained by the above-mentioned single crystal growth method is provided.

Further, according to the fourth aspect of the present invention.
Provided is a single crystal growth method characterized by reducing the amount of crucible dissolved in a melt by shortening the dissolution time of raw materials and reducing the uptake of light elements and heavy metals from the crucible into the solution. ..

Further, according to the fifth aspect of the present invention.
Provided is a single crystal growth apparatus characterized by reducing the amount of crucible dissolved in a solution by shortening the dissolution time of raw materials and reducing the uptake of light elements and heavy metals from the crucible into melting.

Furthermore, according to the sixth aspect of the present invention.
Provided is a single crystal characterized by being formed by melting in which the amount of the crucible dissolved in the melt is reduced by shortening the dissolution time of the raw material and the uptake of light elements and heavy metals from the crucible is reduced.

According to the single crystal growth apparatus according to one aspect of the present invention, since the rotation mechanism configured to enable the intermittent rotation of the crucible is provided, the raw material vibrates due to the intermittent rotation of the crucible when the raw material is melted in the crucible. Is given, and the raw material is shaken off to the bottom surface of the crucible or into the melt by the vibration. This makes it possible to safely and reliably melt the raw materials in the crucible with high efficiency.

Further, according to the single crystal growth method according to another aspect of the present invention, since the crucible is heated while being rotated intermittently, the raw material is shaken into the bottom surface of the crucible or the melt by the vibration applied to the raw material by the intermittent rotation. Be dropped. At the same time, the melting level increases and the raw material silicon is immersed in the melting, so that heat conduction is good and the melting time is shortened. Since the undissolved raw material silicon is sequentially and smoothly immersed in the molten interior, the melting time is accelerated. This makes it possible to safely and reliably melt the raw materials in the crucible with high efficiency.
According to still another aspect of the present invention, since the above single crystal growth method is used, a high quality single crystal can be reliably provided with high efficiency.

This is an example of a block diagram showing a schematic configuration of a single crystal growth apparatus according to an embodiment of the present invention. This is an example of a diagram for explaining the rotation drive of the crucible by the rotation mechanism shown in FIG. This is an example of a graph for explaining an example of a method of predicting the melting time of a raw material by the single crystal growth apparatus shown in FIG. This is an example of a graph for explaining an example of a method of determining the completion of melting of a raw material by the single crystal growth apparatus shown in FIG.

Hereinafter, some embodiments of the present invention will be described with reference to the drawings. The same or corresponding elements / members are designated by the same reference numerals in the drawings, and duplicate description thereof will be omitted as appropriate. In addition, the shape and size of each member in the drawing may not match the actual scale and ratio in order to be appropriately enlarged / reduced / omitted in order to facilitate explanation. Also, in the explanation of the drawings, it should be noted that the terms "upper" and "lower" may not match the direction of gravitational acceleration because the terms "upper" and "lower" are used for convenience in the vertical direction of the paper. In addition, the term "substantially" is used to the effect that measurement error is also included.

In addition, terms such as the first, second, etc. used below are merely identification symbols for distinguishing the same or corresponding components, and the same or corresponding components are the first, second, etc. It is not limited by the terminology of.

Further, the connection does not mean only the case where each component is physically directly contacted with each other in the contact relationship between the components, but other components are interposed between the components and other components are intervened. It is a concept that includes the case where each component is in contact with the structure.

(1) Single Crystal Growth Device FIG. 1 is an example of a schematic diagram showing a schematic configuration of a single crystal growth device according to an embodiment of the present invention. The single crystal growth apparatus 100 shown in the figure includes a single crystal growth furnace 1 in which a crucible 8 can be installed including a heater 10 and a rotation mechanism 20. Observation windows WD10 and WD20 are provided near the top of the single crystal growth furnace 1. In addition, in FIG. 1, in order to show the internal structure simply, only the outline shape of the appearance of the single crystal growth furnace 1 is shown by a broken line.

The single crystal growth apparatus 100 further includes a heater power supply 5, a temperature sensor 11, a conversion unit 21, a temperature display unit 3, a camera 32, a signal processing unit 62, a furnace temperature sensor 42, and a control unit 4. including. The camera 32 is installed in the vicinity of the observation window WD20, images the rutsubo 8 and other internal parts of the furnace through the observation window WD20, and outputs an analog image signal. In the present embodiment, the camera 32 corresponds to, for example, the "imaging element" described in the claims, and the analog image signal corresponds to, for example, the "first signal".
The camera 32 is connected to the signal processing unit 62, and the signal processing unit 62 converts an analog image signal into a digital signal.

The temperature sensor 11 is arranged in the vicinity of the observation window WD10. The temperature sensor 11 is attached so as to be able to scan from the inner wall of the rutsubo 8 to the center of the bottom surface or the center of the raw material polycrystal, or to the side surface of the single crystal during single crystal growth, and detects the amount of light from the object. The temperature sensor 11 is connected to the conversion unit 21. The conversion unit 21 converts the light amount information from the temperature sensor 11 into an electric signal and supplies it to the temperature display unit 3 to display the temperature, and also sends the electric signal to the control unit 4. In the present embodiment, the temperature sensor 11 and the conversion unit 21 correspond to, for example, the "temperature sensor" defined in the claims, and the electric signal to which the light amount information is converted corresponds to, for example, the "second signal".

The control unit 4 is connected to a conversion unit 21, a signal processing unit 62, a temperature display unit 3, and a heater power supply 5, receives a signal input from the conversion unit 21, processes it, and displays the processing result on the temperature display unit 3. In addition to the above, a command signal is generated according to the processing result and supplied to the heater power supply 5, and the temperature in the furnace is adjusted by the amount of electric power supplied to the heater 10. The control unit 4 is also connected to a rotation mechanism 20 and an elevating mechanism (not shown), generates a control signal according to a single crystal growth method described in detail later and supplies the control signals to these mechanisms, and rotates the crucible 8 and pulls up the single crystal. Control the speed. The specific method of controlling the rotation of the crucible 8 will be described in detail later.

A storage device MR is connected to the control unit 4, and a data table used for the single crystal growth method of the embodiment described later, such as an upper limit value of a set temperature and various threshold values, is stored in the storage device MR.

A crucible support shaft 52 is pivotally attached to the bottom of the single crystal growth furnace 1 so as to extend in the vertical direction, and the crucible support shaft 52 supports the crucible 8 and the rotation mechanism 20 described in detail later. The crucible 8 is rotated by the rotation of the crucible support shaft 52. The crucible support shaft 52 is also connected to a crucible elevating mechanism (not shown), and the melt level decreases as the crystal grows. Therefore, the crucible 8 is automatically raised via the crucible support shaft 52 by that amount. As a result, the position (height) of the melt surface is always kept at a constant position (height). In the present embodiment, the crucible support shaft 52 corresponds to, for example, a "support portion" defined in the claims.
The heater 10 is installed between the crucible 8 and the inner wall surface of the single crystal growth furnace 1, and is supplied with electric power from the heater power source 5 to heat the melt L through the space in the furnace and the crucible 8.
The furnace temperature sensor 42 is provided in a region near the heater 10, measures the temperature near the heater 10, and sends a measurement signal to the control unit 4.

The heater power supply 5 includes a power control device (not shown), which is a variable power supply in which an AC power supply is converted into a direct current via a rectifying element such as a thyristor or an IGBT. The heater power supply 5 has a function of adjusting an input voltage signal, and for example, the output power is adjusted to 0 to the maximum power with an input voltage signal of 0 to 5 V. The control unit 4 can adjust the power applied to the heater 10 of the single crystal growth furnace 1 by generating and sending a control signal as a signal to be added or subtracted from the input signal to the power control device.

The temperature inside the single crystal growth furnace 1 is measured by the temperature sensor 42 inside the furnace, and a measurement signal is sent to the control unit 4. The control unit 4 adjusts the set temperature based on the measurement signal from the furnace temperature sensor 42. For example, in the process of growing a single crystal, the temperature inside the furnace can be kept constant in order to control the shape of the single crystal, and the temperature set value can be arbitrarily increased or decreased. On the other hand, in the step of melting the raw material polycrystalline in the crucible 8 in order to obtain the melt L, the temperature setting value can be appropriately changed according to the melting mode of the raw material, as will be described in detail later.

The crucible 8 is formed of, for example, quartz (silicon dioxide) and contains a silicon melt L. In the present embodiment, as the crucible 8, a flat bottom type or a hemispherical bottom double structure in which the bottom surface and the side surface thereof are covered with a graphite crucible can be adopted. This graphite crucible has the purpose of protecting the deformation of the quartz crucible due to heating from the heater 10. Here, as the quartz crucible constituting the crucible 8, for example, it is preferable to use a liquid crucible in which at least the inner wall thereof is subjected to a liquid repellent treatment to form a repellent silica glass on the inner wall. In that case, in the process of single crystal growth, the contact nucleus of the crucible with the inner surface having the liquid property is larger than that of the normal quartz crucible whose interface is wet, and the crystal growth from the crucible side occurs. It can be suppressed. Therefore, in the conventional single crystal growth, it is possible to avoid the phenomenon that the crystal growth from the rutsubo is connected to the growing single crystal and the single crystal falls.

The rotation mechanism 20 includes a rotation driving means such as a motor (not shown), is connected to the crucible support shaft 52, is connected to the control unit 4, receives a control signal from the control unit 4, and receives the crucible support shaft 52. It is rotationally driven, and the crucible 8 is rotated through this. The rotation mechanism 20 is a characteristic component in the present embodiment, and is configured so that two modes, an intermittent rotation mode and a constant speed stable rotation mode, can be switched.

The constant-speed stable rotation mode is a function mainly adopted after the melting of the raw material single crystal is completed and the process shifts to the single crystal growth process, and is substantially the same as the rotation drive adopted in the conventional technology. This is the method of.

On the other hand, the intermittent rotation mode is a drive method adopted in the melting step of the raw material single crystal, and the crucible 8 is intermittently rotated clockwise or counterclockwise around the crucible support shaft 52.
Hereinafter, the method for growing a single crystal using the above-mentioned single crystal growth apparatus 100 will be described as an embodiment of the single crystal growth method according to the present invention.

(2) Single crystal growth method (A) Raw material polycrystalline melting step (i) Intermittent rotation by a rotation mechanism In FIG. 2, the rutsubo 8 into which the raw material polycrystalline is charged is, for example, by the rotation mechanism 20 in the intermittent rotation mode. Clockwise (hereinafter, appropriately referred to as "forward rotation") rotating intermittently in CW1 to CW4, or counterclockwise (hereinafter, appropriately referred to as "reverse rotation") intermittently rotating in CC4 to CC1. It is shown. The rotation directions can be arbitrarily combined, and the rotation may be forward rotation for a certain period of time and then reverse rotation for a certain period of time, or vice versa. Further, forward rotation and reverse rotation may be alternately performed, for example, CW1 → CC1 → CW2 → CC2 → CW3 → CC3 → CW4 → CC4, and any other combination can be selected. In the present embodiment, clockwise and counterclockwise correspond to, for example, the first rotation direction and the second rotation direction, or the second rotation direction and the first rotation direction specified in the claims.

In addition, the rotation angle and rotation speed in each rotation operation can be arbitrarily selected. Further, the time interval between each rotation operation can be freely set. By such intermittent rotation, the lumps of the raw material polycrystalline charged into the crucible 8 are shaken off to the bottom surface of the crucible 8 or the melt L, and it becomes easy to stir in a short time as compared with the prior art.

The rotating mechanism 20 can also perform rapid start and stop to further increase the efficiency of stirring. The acceleration and deceleration of the rapid start and rapid stop can also be freely set according to the oral and weight of the crucible 8, the torque of the rotary drive mechanism provided in the rotary mechanism 20, and the like. Due to such rapid start and rapid stop, the raw material polycrystalline vibrates, and it is further facilitated to shake off to the bottom surface / melt. Then, the raw material polycrystalline that has been shaken off pushes up the melting level and transfers heat to the raw material polycrystalline at the upper part, so that the melting rate can be increased.

Of course, the rapid start and rapid stop operations can be repeated, not only once, so that, as illustrated in FIG. 2, for example, a block of raw material polycrystalline is formed on one wall surface of the crucible. It is fixed, and other lumps are fixed one after another to the lumps stuck to the inner wall of the crucible and are fixed to the inner wall of the opposite crucible, forming a gap between the melt surface and connecting in a bridge shape. Even in such a case, the raw material polycrystalline can be appropriately shaken off and melted efficiently in a short time.

For such intermittent rotation, rapid start and rapid stop, for example, a stepping motor or the like that operates in synchronization with pulse power is used as a rotation driving means, and the control unit 4 uses a desired rotation angle, rotation interval, rotation direction, and so on. It can be implemented by generating and supplying a control signal so that acceleration / deceleration can be obtained.

As described above, conventionally, it has been considered that smooth continuous driving at a constant speed is indispensable for the rotation of the crucible. This is certainly appropriate in the growth process after dipping the seed crystal into the melt, but it is very inferior in terms of the efficiency of raw material stirring in the raw material polycrystalline melting process, which is the preparatory process for crystal growth. In order to promote melting, only the method of raising the heater temperature is adopted, and there is a problem in thermal efficiency. As mentioned above, when a lump piece separated from the melt surface suddenly falls. In addition to the problem that the internal parts are contaminated due to the occurrence of liquid splashing, there is a risk that the silicon adhering to the internal parts may fall onto the growing single crystal and produce a defective product.
According to the present embodiment, the intermittent rotation of the crucible 8 by the rotation mechanism 20 allows the raw material polycrystalline to be melted in a short time with high efficiency, and the melt can be safely obtained.

(Ii) Temperature control and rotation control In the melting step of the raw material polycrystalline, the melting mode of each block of the raw material polycrystalline is different and never uniform. Therefore, the temperature of the melt L is adjusted so that the high temperature portion of the heater temperature is located at the bottom of the crucible 8 because the melting level rises as each agglomerate is immersed in the melt L. However, as the melting progresses, the melting level rises, so it is necessary to sequentially lower the position of the crucible 8 accordingly. Since the rate of increase of the melting level is higher than the conventional rate of increase, the rate of lowering the position of the crucible 8 is also relatively high. Therefore, although the speed of lowering the position of the crucible 8 is programmatically controlled, the speed of lowering the position of the crucible 8 can be set faster in proportion to the dissolution rate.

In the single crystal growth apparatus 100 of the present embodiment, since the temperature sensor 11 measures the temperature at the melt surface and the region near the melt surface (raw material surface), the control unit 4 processes the output signal from the temperature sensor 11. By monitoring the temperature change with the passage of time and comparing the temperature obtained by the measurement with a predetermined threshold value, it is possible to realize appropriate temperature control by generating a control signal and supplying it to the heater power supply 5. can.

FIG. 3 schematically shows an example of a graph showing the temperature of the melt L in the melting step of the raw material polycrystalline with the passage of time. In the melting process, the temperature sensor 11 measures each part on the circumference of the rutsubo 8 at the temperature measurement position of the rutsubo 8 as the rutsubo 8 rotates, and in the graph, the part where the temperature rises is the molten surface. The high temperature part close to melting or melting, and the low temperature part shows the undissolved polycrystal part. As the crucible 8 rotates, the temperature distribution in the circumferential direction inside the crucible can be measured. As the dissolution progresses, the number of undissolved polycrystal parts floating in the melt gradually decreases, the molten surface part of the high temperature part (melted part) expands, and many constant temperature parts are measured at high temperature. Only when the melted polycrystal part passes directly under the sensor, the temperature drops sharply from the high temperature constant temperature, and when it becomes the melted part, it becomes a constant high temperature part. The constant high temperature portion indicates that the temperature is around 1420 ° C., which is the melting temperature of silicon, and indicates that undissolved polycrystals remain in the melt.
Here, when the undissolved polycrystal is completely dissolved, it leads to an increase in the melting temperature shown in FIG. 4, so it is necessary to suppress the increase in the melting temperature (TL1 to TL2) as much as possible.
Therefore, the heater power at the time of melting is supplied to the heater at the temperature of the temperature setting process in which the power is known in advance (the temperature at which the seed crystal is familiar with the melting and does not melt down, and the seed crystal does not grow). Reduce to power value. That is, preventing the melting power from finally exceeding 1450 ° C. and raising the temperature to the temperature range in which the quartz crucible is melted at the completion of melting leads to minimizing the melting of the quartz crucible.

In the present embodiment, for example, after setting the upper limit value T of the temperature as shown in FIG. 3, intermittent rotation is performed with respect to the crucible 8 while heating by the heater 10, and for example, the detection temperature is the upper limit value T (melting of silicon). When the temperature reaches 1420 ° C. (for example, reference numeral P1 in FIG. 3), it is detected that a molten portion in the crucible is formed.
Next, as the rotation progresses (for example, when the reference numeral B1 in FIG. 3 is detected), a rapid start and a rapid stop are performed to induce vibration, thereby shaking the raw material polycrystal. Due to this vibration, the lumps that did not fall on the wall surface of the crucible 8 due to the frictional force are shaken off to the liquid surface. The interval and number of such rapid starts and rapid stops can be appropriately selected according to the size of the crucible 8, the size of the raw material polycrystalline lump piece, and the like.
As the upper limit value T, for example, a temperature of 1420 ° C. suitable for crystal growth may be set.

Further, for example, as shown by reference numeral B1 in FIG. 3, the rapid start and rapid stop may be stopped and the rotation may be returned to the intermittent rotation when the temperature that had been falling starts to rise. The default state in the melting step is not limited to intermittent rotation, but may be normal continuous rotation.
The steps of increasing the amount of heating → rapid start and rapid stop of the rotary drive are continued until the temperature of the melt surface stabilizes (see, for example, the TL1 portion in FIG. 4).

Further, for example, the raw material polycrystal in the crucible 8 is imaged by the camera 32, and the obtained image signal is analyzed by the control unit 4, so that the position of each block piece in the rotation direction of the crucible 8 and (the crucible 8 The distance (height) to the bottom surface or the liquid surface of the melt L can be calculated. Based on the obtained position information and distance (height) information, the settings such as the rotation angle, the rotation speed, and the acceleration and deceleration in the intermittent rotation may be appropriately changed.

Further, since the surface temperature of each block can be measured by the temperature sensor 11, by combining this temperature measurement data with the position data of each block, a temperature distribution map corresponding to the degree of melting of each block can be obtained. It can be prepared, and the dissolved portion and the undissolved portion of the raw material polycrystal can be identified from this map. Therefore, if the specified undissolved portion is used as the main target for shaking off and the rotation direction, rotation interval, rotation angle, rotation speed, acceleration, deceleration, etc. of the intermittent rotation are set, the melt can be obtained more efficiently. can. Reducing the dissolution time of the raw material leads to a reduction in the amount of dissolution of the crucible wall, which makes it possible to reduce the uptake of light elements and heavy metals from the crucible into the molten melt.
The single crystal formed from the molten melt that reduces the uptake of light elements and heavy metals is high because it can improve the lifetime characteristics by reducing the heavy metals and reduce carbon contamination during the production of oxygen and crucible as light elements. A quality single crystal is obtained.

(Iii) Detection of End Timing of Melting Process According to the single crystal growth apparatus 100 of the present embodiment, the end timing of the melting process can be predicted by processing the image signal output from the camera 32 that images the inside of the furnace. can.

More specifically, first, the camera 32 images the raw material polycrystal in the crucible, and the output signal from the camera 32 is processed by the control unit 4, so that all of the raw material polycrystals are required to melt. You can predict the time. Here, the output signal from the camera 32 corresponds to, for example, a second signal defined in the claims.

When almost all the raw material polycrystals are melted, the melt temperature stabilizes, for example, as shown in the substantially left half of the graph of FIG. Then, when the last raw material polycrystal is melted, for example, as shown in the substantially right half of the graph of FIG. 4, it is known that the melt temperature rises sharply immediately after that. Therefore, when the time-temperature graph is monitored by data processing by the control unit 4, the tangent line of the temperature graph is obtained by, for example, differential calculation, the slope is compared with the prepared threshold, and the slope value exceeds this threshold. Can be regarded as the end of the melting process. Since the predicted time until the melting of all the raw materials has already been obtained, the calculation and the threshold comparison may be performed from the timing when the melt temperature starts to stabilize near the end of the predicted time. The threshold data can be changed as appropriate according to the actual value.

(B) Seed Crystal Dipping and Growth Step When the melting step of the raw material polycrystalline is completed and the process shifts to the single crystal growth step, the seed chuck 6 is suspended from the top of the single crystal growth apparatus 100, and the seed crystal is hung at the tip thereof. Is attached and immersed (dipping) in the melt L by an elevating mechanism (not shown). The seed chuck is also connected to another rotation mechanism (not shown) to rotate the seed crystal in a predetermined direction (see AR1 in FIG. 1). In this step, the rotation mechanism 20 connected to the barnardia japonica is switched to the constant speed stable rotation mode by the command signal from the control unit 4, and is rotationally driven so as to perform smooth constant speed rotation.
After that, the seed crystal is continuously grown by a known method, the diameter is expanded to form the shoulder portion, and then the straight body portion and the tail portion are formed and then pulled up to obtain a single crystal.

According to the single crystal growth apparatus 100 of the above-described embodiment, since the rotation mechanism 20 that enables intermittent rotation of the crucible is provided, vibration is applied to the raw material in the melting step of the raw material polycrystalline, and the crucible bottom surface or the inside of the melt L is provided. Since it is shaken off, it becomes possible to efficiently melt the raw material single crystal in the crucible. When intermittent rotation is performed with rapid start and rapid stop, the melting efficiency of the raw material single crystal is further increased, and contamination of the internal parts of the furnace due to liquid splashing is prevented, so that the melt can be obtained safely and reliably. be able to. In addition, the amount of polycrystalline silicon initially loaded into the crucible can be reduced, and the time and effort required for additional charging can be reduced.

Similarly, according to the single crystal growth method according to the above-described embodiment, in the melting step of the raw material polycrystalline, the crucible is heated while being rotated intermittently, so that the raw material is placed on the bottom surface of the crucible or in the melt due to the vibration caused by the intermittent rotation. Be shaken off. As a result, the raw material single crystal in the crucible can be efficiently melted. When rapid start and rapid stop are performed in intermittent rotation, the melting efficiency of the raw material single crystal is further increased, and contamination of the internal parts of the furnace due to liquid splashing is prevented, so that the melt should be obtained safely and reliably. Can be done. Reducing the dissolution time of the raw material leads to a reduction in the amount of the crucible composition dissolved in the melt melt from the inner wall of the crucible (and thus the bottom surface of the crucible). It is possible to reduce the uptake of heavy metals.

Further, by using the single crystal growth method according to the above embodiment, the melt does not adhere to the in-core parts due to liquid splashing during the single crystal growth step, so that the melt can be transferred from the in-core parts to the single crystal. There is no dripping. As described above, according to the present embodiment, it is possible to provide a high quality single crystal with high efficiency, safely and surely.
In addition, single crystals formed from molten melts that reduce the uptake of light elements and heavy metals in the crucible composition by reducing the dissolution time of the raw materials have improved lifetime characteristics by reducing the heavy metals, and oxygen and crucibles can be used as light elements. Since carbon contamination during production can be reduced, a high quality single crystal can be obtained.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but these are for the sake of easy understanding of the invention and do not limit the scope of claims of the present invention. No.

For example, in the above embodiment, the control unit 4 enables the rotation control of the rutsubo and the setting control of the beater temperature, but the temperature data obtained from the temperature sensor and the image of the raw material polycrystalline obtained from the camera are not limited to this. It is possible to control manually while observing.

A person skilled in the art can realize the present invention by making various changes without departing from the scope and purpose of the present invention. For example, by incorporating the features of one embodiment into another embodiment, another Two embodiments can be obtained. Those skilled in the art can make various changes, equivalent substitutions, improvements, etc. in accordance with the gist of the present invention without departing from the scope of claims.

1 Single crystal growth furnace 4 Control unit 8 Crucible 10 Heater 11 Temperature sensor 20 Rotation mechanism 21 Conversion unit 32 Camera 52 Crucible support shaft 100 Single crystal growth device CC1 to CC4
CW1 to CW4
L melt

Claims (20)

A rotation mechanism that rotates the crucible,
A heater that heats the crucible and
Equipped with a crystal growth furnace including
The crucible contains at least one of a silicon melt and a raw material for the melt.
The rotation mechanism is configured to allow intermittent rotation of the crucible.
Single crystal growth device. The single crystal growth apparatus according to claim 1, wherein the rotation mechanism executes the intermittent rotation by rapid start and rapid stop. The rotation of the crucible by the rotation mechanism includes a first rotation direction centered on a support portion that supports the crucible, a second rotation direction opposite to the first rotation direction, and the first rotation direction and the second rotation direction. The single crystal growth apparatus according to claim 2, further comprising at least one of any combination of rotation directions. The single crystal growth apparatus according to claim 3, wherein the rotation mechanism is capable of rotating the crucible at an arbitrary angle and speed in both the first rotation direction and the second rotation direction. An image sensor that captures the crucible and outputs the first signal,
A control unit that controls the rotation of the crucible by the rotation mechanism and controls the electric power to the heater based on the first signal.
The single crystal growth apparatus according to any one of claims 1 to 4, further comprising. The control unit processes the first signal to detect the position of the raw material in the rotation direction of the crucible and the distance from the bottom surface of the crucible or the liquid surface of the melt, and based on the detection result. The single crystal growth apparatus according to claim 5, wherein the rotation mechanism is controlled and the electric power to the heater is controlled. A temperature sensor that measures the temperature of the melt and outputs a second signal is further provided.
The single crystal growth apparatus according to claim 5, wherein the control unit predicts the melting time of the raw material by processing the first signal, and determines the completion of melting by processing the second signal. .. The single crystal growth apparatus according to any one of claims 1 to 7, wherein the crucible contains a quartz crucible in which a liquid-soluble silica glass is formed on an inner wall. In a single crystal growth method using a single crystal growth furnace, a step of heating the crucible while intermittently rotating a crucible containing a silicon (silicon) raw material to melt the raw material, and a step of melting the raw material.
A step of suspending a seed crystal, immersing it in a melt in a crucible obtained by melting the raw material, and pulling up the seed crystal while rotating the crucible to grow the seed crystal.
To prepare
Single crystal growth method. The single crystal growth method according to claim 9, wherein the intermittent rotation includes a rapid start and a rapid stop of the rotation. The rotation of the crucible is in the first rotation direction centered on the support portion that supports the crucible, the second rotation direction opposite to the first rotation direction, and the first rotation direction and the second rotation direction. The single crystal growth method according to claim 10, further comprising at least one of any combinations. The intermittent rotation is performed at intervals of any angle in both clockwise and counterclockwise directions around the support portion that supports the rutsubo so that the liquid level of the melt is horizontal. The single crystal growth method according to claim 11, wherein the single crystal growth method is performed at an arbitrary rotation speed at each interval. The process of imaging the crucible and acquiring the first signal,
A step of controlling the rotation of the crucible based on the first signal, and
A step of changing the setting of the heating temperature of the crucible based on the first signal, and
The single crystal growth method according to any one of claims 9 to 12, further comprising. The first signal is processed to detect the position of the raw material in the rotation direction of the crucible and the distance from the bottom surface of the crucible or the liquid surface of the melt, and rotation control and temperature control are performed based on the detection results. The single crystal growth method according to claim 13, further comprising a step of performing the above. The step of measuring the temperature of the melt and acquiring the second signal, and
A step of processing the first signal and the second signal, predicting the melting time of the raw material, and determining the completion of melting of the raw material.
The single crystal growth method according to claim 13 or 14, further comprising. The single crystal growth method according to any one of claims 9 to 15, wherein the crucible contains a quartz crucible in which a liquid-soluble silica glass is formed on an inner wall. A single crystal obtained by the single crystal growth method according to any one of claims 9 to 16. A single crystal growth method characterized by reducing the amount of crucible dissolved in a melt by shortening the dissolution time of raw materials, and reducing the uptake of light elements and heavy metals from the crucible into the melt. A single crystal growth apparatus characterized by reducing the amount of crucible dissolved in a melt by shortening the dissolution time of raw materials and reducing the uptake of light elements and heavy metals from the crucible into melting. A single crystal characterized by being formed by melting in which the amount of the crucible dissolved in the melt is reduced by shortening the dissolution time of the raw material, and the uptake of light elements and heavy metals from the crucible is reduced.

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