JP3704710B2 - Method of setting seed crystal deposition temperature and silicon single crystal manufacturing apparatus - Google Patents

Description

【Technical field】
[0001]
The present invention relates to a method for manufacturing a silicon single crystal using the Czochralski method (hereinafter sometimes referred to as CZ method) and a manufacturing apparatus therefor, and more specifically, to a crucible in a furnace of a manufacturing apparatus. Efficient and wasteful determination of the appropriate temperature of the silicon melt when the seed crystal is deposited on the silicon melt obtained by melting the filled polycrystalline silicon material and melting the polycrystalline silicon material The present invention relates to a seed crystal deposition temperature setting method that enables a silicon crystal growth step without any defects, and a silicon single crystal manufacturing apparatus that is suitably used for carrying out this method.
[Background]
[0002]
First, a method and apparatus for growing a single crystal by the CZ method will be briefly described. An apparatus for growing a single crystal used in a general CZ method includes a crucible for containing a silicon melt in a chamber (furnace) of a manufacturing apparatus, and this crucible is a high-purity silicon melt. In order to protect the crucible made of quartz, the inner side in contact with the raw material melt has a double structure in which a crucible made of graphite is arranged on the outer side to protect the inner crucible.
[0003]
Around the crucible containing the raw material, a heater made of graphite or the like is attached for melting the polycrystalline silicon raw material filled in the crucible and holding the molten silicon melt at a predetermined temperature. Yes. A heat insulating material made of graphite is placed on the outside of the heater, and plays a role of heat insulation in the manufacturing apparatus furnace and protection of the manufacturing apparatus furnace wall made of metal.
[0004]
In addition, in order to obtain a desired crystal shape and quality during single crystal growth, crystal growth is performed by adjusting various conditions while rotating the crucible and the seed crystal in opposite directions during single crystal growth. For this reason, a crucible rotating mechanism is attached to the lower end of the crucible shaft supporting the crucible in the manufacturing apparatus furnace, while the seed crystal is rotated upward while rotating the seed crystal above the manufacturing apparatus. It is equipped with a wire rotation winding mechanism for rotating and winding the pulling wire to which the crystal is connected.
[0005]
In order to manufacture a silicon single crystal using this single crystal manufacturing apparatus by the CZ method, first, a polycrystalline silicon raw material is put in a crucible in a single crystal manufacturing apparatus furnace, and this is heated to 1400 by a heater arranged around the crucible. It melts by heating to a high temperature of ℃ or higher to form a silicon melt. Then, after confirming that the polycrystalline silicon raw material was completely melted, adjust the operating conditions such as the position of the crucible filled with the raw material melt and the amount of inert gas flowing in the furnace to the single crystal growth conditions, The temperature of the finished silicon melt is lowered to a temperature suitable for single crystal growth, and the furnace environment is adjusted.
[0006]
And, when the melt temperature is stabilized at a temperature suitable for growing a single crystal, gently seed the seed crystal on the surface of the silicon melt, and then gradually wind up while rotating the pulling wire by the wire rotation mechanism, A single crystal rod is grown below the seed crystal.
[0007]
In the growth of such a silicon single crystal rod, the process after the seed crystal is immersed in the melt has the functions of various detection devices to grasp the control mechanism of the manufacturing equipment and the crystal growth status in the furnace. Thus, after growing a predetermined single crystal rod, until the single crystal is separated from the melt, crystal growth is automatically advanced with almost no operator involved, and labor saving is achieved.
[0008]
However, other than these, for example, in the melting process of the polycrystalline silicon raw material, it is necessary to control the melting conditions in a complicated manner depending on the state of the raw material melted in the crucible. Is often promoted.
[0009]
For this reason, the process is automatically advanced after the seed crystal is deposited in the raw material melt, whereas in the other processes, particularly the polycrystalline silicon melting process, the operator monitors the equipment near the manufacturing equipment. Since it is necessary to advance the process while making adjustments, it is regarded as a problem in automating single crystal manufacturing operations and increasing the efficiency of the process.
[0010]
When melting the polycrystalline silicon raw material filled in the crucible in the production equipment furnace, the raw material is superheated by a heater and kept at a high temperature to melt, but the equipment is used to completely melt the raw material in the crucible. It is often difficult to make a judgment based on the experience of the operator. In addition, in order to complete the completion of melting, the worker continues heating with a heater for a predetermined time after it is determined that the melting has ended, so that there is no unmelted raw material in the melt. At present, the raw material is often melted at the expense of the properties.
[0011]
It is necessary to completely melt the polycrystalline silicon raw material before moving to the single crystal growth process because the raw material floats on the surface of the melt during the growth of the single crystal rod, and the growth of the single crystal is excluded. This is because the temperature of the silicon melt is not stable due to the presence of undissolved residue in the liquid, and crystal growth is not smoothly performed.
[0012]
For these reasons, in order to completely melt the polycrystalline silicon raw material, the worker can dissolve the raw material in the melt even after all of the raw material on the surface of the melt is dissolved and there is no polycrystalline silicon floating in the silicon melt. In such a case, the above-described problem occurs during single crystal growth. Therefore, the melting time is increased and the melt is heated to a high temperature for a certain period of time to eliminate undissolved material in the raw material melting step.
[0013]
However, the determination of whether or not the melting of the polycrystalline silicon raw material has been completed depends greatly on the shape of the polycrystalline silicon raw material, the amount of raw material charged into the crucible, the size of the crucible, etc. It is a difficult task even for a worker who has done so.
[0014]
Recently, large crucibles with a diameter of more than 50 cm have been used to produce long, large-diameter silicon single crystal rods, and the polycrystalline silicon that fills them is more than 100 kg. While it becomes difficult to grasp the timing of the end of melting, the time until the end of the melting process is longer.
[0015]
Furthermore, the fact that it takes time to melt the polycrystalline material not only simply increases the production time of the single crystal and decreases the productivity, but also exposes the crucible made of quartz to a high temperature exceeding 1400 ° C. for a long time. As a result, the durability of the crucible is weakened and the inner surface of the quartz crucible in contact with the melt is roughened, causing slip dislocation during the growth of the single crystal, or the crucible deterioration is accelerated, making it difficult to operate for a long time. For example, it may cause problems in quality and yield of crystals.
[0016]
For this reason, it is not desirable to unnecessarily increase the melting time of the raw material. Appropriately determining the completion of the melting of the polycrystalline silicon raw material also affects the subsequent processes and places a heavy burden on the operator. .
[0017]
In addition, after melting the polycrystalline silicon raw material to form a silicon melt, it is also possible to stabilize the melt temperature to a desired value so that the melt temperature can be lowered and the seed crystal can be deposited on the surface of the silicon melt. Rely on worker experience.
[0018]
In order to grow a single crystal below the seed crystal by depositing the seed crystal in the silicon melt, the temperature of the raw material melt is lowered after the melting of the polycrystalline silicon raw material is completed, and the temperature of the silicon melt is changed to the single crystal. It is necessary to stabilize at a temperature suitable for growth. However, it is extremely difficult to stabilize the melt at a temperature suitable for growing this silicon single crystal. Until now, the temperature of the molten metal surface is detected by various machines and controlled to reach the desired temperature. However, even if an optical thermometer or the like is used, it is possible to detect the temperature in the manufacturing apparatus furnace with high accuracy without error, and the amount of the melt contained in the crucible or in the manufacturing apparatus furnace It is very difficult because it is easily affected by a hot zone or the like, and in many cases, it is also left to the operator's judgment to determine the melt surface temperature when the seed crystal is deposited on the silicon melt.
[0019]
In the production of a silicon single crystal using the CZ method, if the melt temperature when the seed crystal is deposited in the melt does not match the conditions for properly growing the single crystal, A single crystal rod cannot be grown.
[0020]
For example, if the melt temperature when the seed crystal is deposited in the melt is lower than the desired temperature, the seed crystal is solidified on the melt surface around the seed crystal as soon as the seed crystal is deposited in the melt. Even if the single crystal is forcibly grown in a state, seed drawing cannot be performed normally, and the single crystal cannot be stably grown. On the other hand, when the temperature of the melt is higher than a desired value, the tip of the seed crystal is melted even if the seed crystal is deposited in the melt, and the seed crystal can be deposited in the silicon melt. There is a problem that it is impossible to grow a single crystal unless the melt temperature is lowered.
[0021]
Therefore, if the temperature does not reach an appropriate value when the seed crystal is deposited on the melt, the heat generated by the heater is adjusted again to stabilize the melt temperature to the desired value. become. However, this work requires changing the temperature of the large amount of silicon melt in the crucible and waiting until the melt temperature stabilizes, which not only causes a large loss in manufacturing time but also places a burden on the crucible. Since it also affects the isochronous process in which slip dislocation is brought about during the growth, it is preferable to adjust the temperature of the melt to a condition suitable for single crystal production at a time if possible.
[0022]
However, the work that relies on the experience of the operator has a large variation, and the work for setting the melt temperature to an appropriate temperature is a time-consuming work. In particular, recently, crucibles have become larger for the production of long, large-diameter crystals, and the amount of silicon melt to be accommodated tends to increase. It is becoming increasingly difficult to adjust the melt temperature appropriately, and automation is becoming increasingly difficult. It has become one of the desired tasks.
DISCLOSURE OF THE INVENTION
[Problems to be solved by the invention]
[0023]
The present invention was made to solve these problems, and in the production of a silicon single crystal using the CZ method, when the polycrystalline silicon raw material housed in the crucible is heated and melted by a heater, Suitable for growing the single crystal by detecting the melt surface temperature of the melted silicon material and detecting that the polycrystalline silicon material is completely melted, and lowering the silicon melt temperature after the melting is completed. An object of the present invention is to provide a seed crystal deposition temperature setting method and a silicon single crystal manufacturing apparatus capable of efficiently obtaining the melt temperature, reducing process loss, and saving work and reducing the burden of work. To do.
[Means for Solving the Problems]
[0024]
In order to solve the above problems, a first aspect of a method for detecting the end of melting of a polycrystalline silicon raw material is that a crucible in a single crystal manufacturing apparatus is filled with the polycrystalline silicon raw material and heated to heat the polycrystalline silicon raw material. This is a method for detecting the end of melting of a polycrystalline silicon raw material in the production of a silicon single crystal using the Czochralski method in which a seed crystal is deposited in a silicon melt after the melting of the silicon and a single crystal is grown below the seed crystal. When the polycrystalline silicon raw material accommodated in the crucible is melted by the optical means when the silicon melt surface temperature is melted, the fluctuation range of the measured silicon melt surface temperature becomes a value equal to or less than a predetermined value. Is the first melting end point at which the melting of the polycrystalline silicon raw material is completed, and the completion of the melting of the polycrystalline silicon raw material is detected by this first melting end point.
[0025]
If such a detection method is used to detect the end of melting of the polycrystalline silicon material housed in the crucible, it can be known that the polycrystalline silicon material in the crucible has been melted. By using such a method for detecting the end of melting of the polycrystalline silicon raw material, in order to make the melting more reliable as compared with the case where the end of melting of the raw material is confirmed by manually observing the inside of the manufacturing apparatus furnace. It is no longer necessary to heat the crucible wastefully for a long time, and it is not necessary for the operator to look into the furnace frequently, so that it is possible to improve the efficiency and productivity of the work. In addition, since the end of melting of the polycrystalline silicon raw material can be known by the apparatus, it is possible to determine the end of stable melting regardless of the operator's experience, so that the process becomes stable and the operator's proficiency It leads to shortening of period.
[0026]
In the second aspect of the method for detecting the end of melting of the polycrystalline silicon raw material, the crucible in the single crystal manufacturing apparatus is filled with the polycrystalline silicon raw material, and the polycrystalline silicon raw material is melted by heating the heater. A method for detecting the end of melting of a polycrystalline silicon raw material in the production of a silicon single crystal using the Czochralski method of depositing a seed crystal and growing a single crystal below the seed crystal, which is contained in the crucible The melt surface temperature when the polycrystalline silicon raw material is melted is measured by an optical means, and when the measured fluctuation range of the melt surface temperature of the silicon becomes less than a predetermined value, the melt temperature is further increased for a predetermined time of 5 minutes or more. In the meantime, if the fluctuation range of the melt surface temperature is less than or equal to a predetermined value, the time when the predetermined time has elapsed is defined as a second melting end point at which the melting of the polycrystalline silicon raw material is completed. Melting And detecting the end of melting the polycrystalline silicon material by Ryoten.
[0027]
Even if the fluctuation range of the temperature is detected from the measured value of the molten metal surface temperature and the value becomes smaller than the predetermined value, if the error of the measured value is taken into account, it is continuously melted. By observing the liquid surface temperature data and ending melting of the polycrystalline raw material when the fluctuation range is stable for a predetermined time below a predetermined value, detection can be made more reliable. False detection can be prevented.
[0028]
If the time for continuously observing the melt surface temperature is too short after the fluctuation range of the melt temperature is equal to or less than a predetermined value, the probability of false detection of the end of melting of the raw material increases. It is preferable to continue the measurement for 5 minutes or more. On the other hand, it is not preferable to measure for a long time because the process is prolonged, and should be kept within 30 minutes at the longest, and the optimum value should be around 10 minutes.
[0029]
In addition, after the fluctuation range of the melt temperature becomes less than or equal to the predetermined value, the fluctuation range becomes more than the predetermined value within the time during which the melt surface temperature is continuously observed. Alternatively, the measurement may be performed again from that point, or a method may be employed in which the end of melting of the melt is detected after the molten state is maintained until a predetermined time or a predetermined condition is satisfied.
[0030]
In the third aspect of the method for detecting the end of melting of the polycrystalline silicon raw material, the crucible in the single crystal manufacturing apparatus is filled with the polycrystalline silicon raw material, and the polycrystalline silicon raw material is melted by heating the heater. A method for detecting the end of melting of a polycrystalline silicon raw material in the production of a silicon single crystal using the Czochralski method of depositing a seed crystal and growing a single crystal below the seed crystal, which is contained in the crucible The temperature of the silicon melt surface when the polycrystalline silicon raw material is melted is measured by optical means, and when the fluctuation range of the measured silicon melt surface temperature becomes a predetermined value or less, the melt temperature is further measured for 5 minutes or more. In the meantime, when the measured temperature of the silicon melt obtained by melting the polycrystalline silicon reaches a predetermined temperature or more, the third melting end point at which the melting of the polycrystalline silicon raw material is completed is defined as the third melting end point. Melting And detecting the end of melting the polycrystalline silicon material by the end point.
[0031]
During the melting of the polycrystalline silicon raw material, the melt is always heated by the heater, and the melt temperature continues to rise little by little. In particular, when the melting of the polycrystalline raw material is completed, the melt temperature surely rises. Therefore, if the temperature rises more than necessary, deterioration of the crucible wall is promoted, which is not preferable. Therefore, as one parameter for determining the end of melting of the polycrystalline silicon raw material, when the silicon melt surface temperature is continuously observed after the fluctuation range of the silicon melt temperature becomes a predetermined value or less, the polycrystalline silicon is If the melting temperature of the melted silicon melt reaches the specified temperature (the upper limit of the melt heating temperature) or higher, the crucible heats more than necessary if the conditions for melting the polycrystalline silicon raw material are taken into account. In addition, the reliability of detecting the end of melting can be increased.
[0032]
In the fourth aspect of the method for detecting the end of melting of the polycrystalline silicon raw material, the crucible in the single crystal manufacturing apparatus is filled with the polycrystalline silicon raw material, and the polycrystalline silicon raw material is melted by heating the heater. A method for detecting the end of melting of a polycrystalline silicon raw material in the production of a silicon single crystal using the Czochralski method of depositing a seed crystal and growing a single crystal below the seed crystal, which is contained in the crucible An imaging device for imaging the surface of the silicon melt is provided, the image signal of the silicon melt surface imaged by the imaging device is binarized, and the polysilicon raw material is converted into silicon by the binarized signal. The point of time when it is detected that the material is not floating on the melt surface is defined as a fourth melting end point at which the melting of the polycrystalline silicon raw material is completed, and the melting end of the polycrystalline silicon raw material is determined by the fourth melting end point. Characterized in that it out. In order to detect that the polycrystalline silicon raw material has completely dissolved, it is also possible to detect the level of the silicon melt using an imaging device such as a TV camera and binarize the imaging signal. You can also.
[0033]
The surface of the polycrystalline silicon raw material has a gloss unique to the metal, and shows an illuminance different from that of the silicon melt when the radiant heat from a heater or the like is reflected. Taking advantage of this characteristic, the surface of the silicon melt in the crucible is captured by an imaging device. For example, if the image signal is a predetermined intensity (threshold value) or more, “1 (bright portion)”, a value lower than that If it is a signal, binarization processing is performed to output “0 (dark part)”, and if there is no portion showing illuminance of “1” in the imaged screen, it is determined that the raw material melt has completely dissolved. Is possible. Since the polycrystalline silicon raw material has a specific gravity lighter than that of the silicon melt, it floats on the surface until it is completely melted. If it can be detected from the screen that the signal with high illuminance equal to or higher than the threshold value has disappeared, it is possible to know that the melting of the raw material has almost ended.
[0034]
Furthermore, any one of the first to third melting end points described above and both the melting end point and the fourth melting end point are detected, and polycrystalline silicon is detected by the melting end point detected later in time. The end of melting of the raw material can also be detected.
[0035]
That is, the temperature of the silicon melt after the temperature fluctuation of the silicon melt has fallen below the predetermined value, or the temperature fluctuation has been below the predetermined value has continued for a predetermined time, or the temperature fluctuation has fallen below the predetermined value. When the temperature reaches a predetermined temperature or higher, and the imaging screen of the silicon melt surface is binarized to detect that the polycrystalline silicon lump has disappeared from the melt surface. If the end of melting of the polycrystalline silicon raw material is detected based on the detected end point of melting, it is possible to automatically detect the end of melting with higher accuracy. Further, if the end of melting of the raw material is detected by such a method, erroneous detection and malfunction are prevented, and the detection method is highly reliable and safe.
[0036]
Next, the first aspect of the method for setting the seed crystal deposition temperature according to the present invention is that the crucible in the single crystal manufacturing apparatus is filled with the polycrystalline silicon raw material and the heater is heated to melt the polycrystalline silicon raw material. A method for setting a seed crystal deposition temperature in the production of a silicon single crystal using the Czochralski method in which a seed crystal is deposited in a silicon melt and a single crystal is grown below the seed crystal, The melt surface temperature when the accommodated polycrystalline silicon raw material is melted is measured by optical means, and if the fluctuation range of the measured melt surface temperature becomes a predetermined value or less, the minimum melt surface temperature measurement value at that time The value is the first minimum melt surface temperature, and the first minimum melt surface temperature is the seed crystal landing temperature when the seed crystal is deposited on the melt.
[0037]
If the seed crystal deposition temperature when the seed crystal is deposited in the melt is set by such a method, the temperature of the melt is too low when the seed crystal is deposited in the melt. To reduce the problems such as solidification on the liquid surface or melting the seed crystal due to the melt temperature being too high, so that the seed crystal cannot be deposited in the melt. The time required for adjusting the silicon melt temperature can be shortened.
[0038]
In particular, it is difficult for even a skilled worker to adjust the temperature of the silicon melt at the time of landing the seed crystal in the melt, and this is a time-consuming work. In addition, while adjusting the melt temperature to a desired value, it is necessary to observe the inside of the furnace frequently, and it is a process that takes man-hours and work load, but the method of the present invention is used. This makes it possible to accurately know the seed crystal deposition temperature at the end of melting, so it is possible to reduce the burden on the operator and shorten the process time without requiring time to automate the temperature lowering operation and adjust the temperature. Become.
[0039]
And the 2nd aspect of the setting method of the seed crystal landing temperature of this invention is a silicon | silicone after filling the crucible in a single-crystal manufacturing apparatus with a polycrystalline silicon raw material, heating a heater and melting a polycrystalline silicon raw material. A method for setting a seed crystal deposition temperature in the production of a silicon single crystal using the Czochralski method in which a seed crystal is deposited in a melt and a single crystal is grown below the seed crystal, and is contained in the crucible. The melt surface temperature when the polycrystalline silicon raw material is melted is measured by optical means, and when the fluctuation range of the measured silicon melt surface temperature becomes a predetermined value or less, the melt temperature is further measured for 5 minutes or more. In this period, the minimum value of the silicon melt surface temperature is set as the second minimum melt surface temperature, and the seed crystal landing liquid when the second minimum melt surface temperature is made to land on the melt. It is characterized by temperature. With such a configuration, the seed crystal landing temperature can be determined more reliably than the above-described method.
[0040]
If the seed crystal landing temperature is set by such a method, the certain liquid landing temperature can be known with less error.
[0041]
In addition, after the time when the fluctuation range of the measured silicon melt surface temperature becomes a value equal to or less than the predetermined value, if the time for continuously measuring the silicon melt temperature is shorter than necessary, an error may be induced. It should be at least 5 minutes at least. On the other hand, if it is too long, useless time will be consumed, causing problems such as deterioration of the crucible wall. Should be within 30 minutes. Preferably, the time is about 10 minutes, and the loss of process time can be reduced.
[0042]
The first aspect of the silicon single crystal production apparatus of the present invention is:Filling the crucible in the single crystal manufacturing apparatus with polycrystalline silicon raw material, heating the heater to melt the polycrystalline silicon raw material, and then seeding the silicon melt with the seed crystal to grow the single crystal below the seed crystal An apparatus for producing a silicon single crystal by the Czochralski method, the melt surface temperature measuring means for optically measuring the liquid surface temperature of the silicon melt contained in the crucible, and the melt surface temperature measuring means The maximum and minimum values of the melt surface temperature are obtained from the connected temperature data, and the difference between the maximum and minimum values is compared with the data input in advance as the fluctuation range of the melt surface temperature. Is less than the value of the previously input data, the operation condition control device that determines the end of melting of the polycrystalline silicon raw material and sends a heater power control signal, and the heater power control signal from this operation condition control device Base Data Based on the data from the melt surface temperature measuring means that optically measures the liquid surface temperature of the silicon melt contained in the crucible, which includes a heater power control device for lowering the power to the seed crystal deposition temperature. Obtain the temperature fluctuation range of the melt surface, and control the heater power using the minimum melt surface temperature measurement value when the temperature fluctuation range is smaller than the value input in the controller as the seed crystal deposition temperature It is characterized by sending a signal.
[0043]
By using such an apparatus, it is possible to automatically detect the completion of the melting of the raw material in the crucible and shift to a silicon melt cooling operation without the need for an operator. As a result, wasteful heating of the melt in the melting process can be suppressed, the burden on the operator for determining the end of melting is reduced, and the process time is stabilized.
[0044]
Further, the temperature fluctuation range of the melt surface is obtained based on the data from the melt surface temperature measuring means, and the melt surface temperature when the temperature fluctuation range becomes smaller than the value input in the control device. The heater power control signal is sent with the minimum value of the measured value as the seed crystal temperature, and at the same time that the melt end of the raw material melt is detected, the seed crystal landing temperature after the melt cooling operation can be known. Therefore, the minimum value of the measured melt surface temperature is set as the seed crystal deposition temperature, and if the temperature of the melt is lowered to reach this temperature, the desired seed crystal deposition temperature is automatically obtained. As a result, it is possible to reduce the burden of the operation operation for adjusting the melt temperature to the seed crystal deposition temperature after the silicon melt lowering operation.
[0045]
Of the present inventionThe second aspect of the silicon single crystal manufacturing apparatus is:Filling the crucible in the single crystal manufacturing apparatus with polycrystalline silicon raw material, heating the heater to melt the polycrystalline silicon raw material, and then seeding the silicon melt with the seed crystal to grow the single crystal below the seed crystal An apparatus for producing a silicon single crystal by the Czochralski method, the melt surface temperature measuring means for optically measuring the liquid surface temperature of the silicon melt contained in the crucible, and the melt surface temperature measuring means The maximum and minimum values of the melt surface temperature are obtained from the connected temperature data, and the difference between the maximum and minimum values is compared with the data input in advance as the fluctuation range of the melt surface temperature. Is less than the value of the previously input data, the operation condition control device that determines the end of melting of the polycrystalline silicon raw material and sends a heater power control signal, and the heater power control signal from this operation condition control device Base The heater power control device for lowering the power of the crystal to the seed crystal deposition temperature, the imaging device for imaging the liquid level of the silicon melt accommodated in the crucible, and the binarized image captured by the imaging device An image processing device for processing, and when the image signal subjected to binarization processing by the image processing device is equal to or lower than a threshold value, it can be determined that the melting of the polycrystalline silicon raw material has ended, and The temperature fluctuation width of the melt surface is obtained based on data from the melt surface temperature measuring means for optically measuring the liquid surface temperature of the silicon melt contained in the crucible, and this temperature fluctuation width is input into the controller. The heater power control signal is sent with the minimum value of the measured melt surface temperature when the temperature is smaller than the set value as the seed crystal deposition temperature.
[0046]
According to this apparatus, in detecting the end of melting of the polycrystalline silicon raw material,The first apparatus for producing the silicon single crystal 1 In addition to the automatic detection function of the end of material melting according to the aspect ofThe liquid level of the silicon melt contained in the crucible is captured as an image by an imaging device such as a TV camera or a CCD camera, and the illuminance of the raw material lump floating on the melt surface and the illuminance of the silicon melt surface are binarized. The end of melting can be detected with high accuracy by the function of detecting the end of melting and the fact that the illuminance signal of the polycrystal silicon block disappears from the segmented and captured images.
[0047]
thisAccording to the apparatus, any of the first to fourth melting end points described above can be detected, and detection with extremely high reliability and safety can be performed.
[0048]
The detected value of the seed crystal deposition temperature may be slightly deviated from the true value due to the influence of the structure in the manufacturing apparatus furnace, the amount of silicon melt contained in the crucible, and the like. In such a case, it is possible to configure a more reliable device by appropriately correcting the detected value to improve the accuracy.
[0049]
The technical idea of the present invention will be described in more detail. When melting polycrystalline silicon raw material, it is necessary to heat the inside of the production equipment furnace to a high temperature, and it is very difficult to directly measure the temperature of the silicon melt. Generally, radiation thermometers, two-color thermometers, etc. Measurement is performed from outside the manufacturing apparatus using the optical temperature measuring means. However, when the polycrystalline raw material is melted, there is reflection of light from the surface of the polycrystalline silicon due to reflection of heat generated from the heater. Thus, it is difficult to measure the true temperature until the melting of the polycrystalline silicon raw material is completed. Therefore, the melt temperature is usually measured after the melting of the polycrystalline raw material.
[0050]
On the other hand, when the polycrystalline silicon raw material is completely melted, reflection from the polycrystalline raw material that disturbs the measurement of the optical measurement system is eliminated, so that the temperature measurement value of the silicon melt is stable and normal measurement is performed. After that, when the melting is continued without changing the heater power, the melt temperature gradually rises while maintaining a predetermined temperature fluctuation.
[0051]
The eye of the method for detecting the end of melting of the polycrystalline silicon raw material is that the measurement temperature varies when the polycrystalline raw material is in the melt, and the temperature of the silicon melt is stabilized to some extent after the raw material is completely melted. By detecting the difference in the detection temperature variation at the time, it is detected that the polycrystalline silicon raw material has been melted. The detection value of the melt temperature when the polycrystalline raw material is in the melt varies widely, and it can be clearly distinguished from the temperature fluctuation after the end of melting, so that it can be used to detect the melting of the raw material. Then, the end of melting can be reliably detected by the apparatus without depending on the visual observation of the operator.
[0052]
The melt temperature just before the end of melting of the polycrystalline silicon raw material is a state in which the unmelted silicon polycrystal and the melt are mixed in the crucible, and the temperature of the melt at this time is approximately the melting point of silicon. (1420 ° C). After the temperature lowering step, it is desirable that the melt temperature when the seed crystal is deposited on the melt is close to the melting point of this silicon, and the melt temperature and the seed crystal immediately after the melting end are deposited on the melt. As a result of repeatedly measuring and investigating the relationship with the melt temperature suitable for the above, it was found that the minimum value of the melt temperature measurement value after the end of the melting was close to the seed crystal deposition temperature.
[0053]
The silicon melt in the crucible always generates thermal convection by heating from the heater. Under the influence of this convection, the silicon melt repeats temperature fluctuations with a certain width, but in the melt temperature fluctuation immediately after the melting of the raw material, the minimum melt temperature measured at that time is the melting point of silicon, that is, the seed crystal. Is the value closest to the melt temperature when the liquid is deposited on the melt.
[0054]
In particular, in the method of measuring the temperature of the melt using an optical measuring device from outside the manufacturing apparatus furnace, the melt is heated by a shielding object such as glass or a heater between the measuring devices, or the raw material to be melted. It is easily affected by the amount, etc., and it is extremely difficult to measure the absolute temperature of the melt surface and adjust the liquid temperature to the seed crystal deposition temperature. Therefore, if the seed crystal deposition temperature is determined by the method of the present invention, the seed crystal deposition temperature is relatively detected, so that measurement errors caused during temperature measurement can be suppressed to a small level. The temperature can be precisely matched to the intended seed crystal deposition temperature.
[0055]
In order to more reliably detect the end of melting of the polycrystalline silicon raw material lump, the silicon melt surface in the crucible is photographed with a television camera using an image sensor such as a CCD element or a photoelectric tube, and the photographing signal is electrically detected. If it is determined that the melting of the polycrystalline silicon raw material has been completed after detecting that the raw material lump floating on the melt surface has disappeared from the screen, the detection method and apparatus can be made highly reliable.
[0056]
When the polycrystalline silicon raw material is melted, the specific gravity of the raw material is lighter than that of the melt, so that many raw material lumps are always melted while floating on the melt surface. Therefore, if the silicon melt surface is observed, it can be determined whether the polycrystalline silicon is completely melted or not melted.
[0057]
In particular, the polycrystalline silicon raw material has a metallic luster, and the polycrystalline silicon raw material floating on the surface of the silicon melt reflects the radiant heat from a heater or the like with high illuminance, so that the melt portion and the suspended matter are reflected. It is easy to distinguish the brightness of the part, and it is determined whether the polycrystalline silicon raw material is floating on the melt by performing a binarization process that divides the image captured by the imaging device into a dark part and a bright part Can do.
[0058]
The end of melting of the polycrystalline silicon raw material is detected by using the results of both the presence / absence of suspended matter on the melt by the binarization process and the measured value of the temperature fluctuation resulting from the temperature measurement of the melt surface. This leads to improved detection accuracy and further reliability.
BEST MODE FOR CARRYING OUT THE INVENTION
[0059]
Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking as an example the growth of a silicon single crystal by the CZ method. However, the present invention is not limited to these. For example, the method and apparatus of the present invention can naturally be used even when the MCZ method for growing a single crystal while applying a magnetic field to a raw material melt is used.
[0060]
FIG. 1 is a schematic cross-sectional view showing one embodiment of a single crystal production apparatus of the present invention. The single crystal manufacturing apparatus 12 in FIG. 1 has a manufacturing apparatus furnace main body 14 in which a raw material melt is accommodated and single crystals are grown, and an upper chamber 21 in which the grown single crystals are accommodated. A crucible C made of quartz on the inside and graphite on the outside via a support shaft 15 is provided at the center of the furnace body 14 so as to be rotatable and vertically movable. The crucible C is filled with a polycrystalline silicon raw material, and is melted by heating a heater 18 disposed around the crucible C to form a silicon melt M. Further, a heat insulating material 20 for protecting the furnace body 14 of the manufacturing apparatus and enhancing the heat retaining effect in the furnace is disposed on the outer periphery of the heater 18.
[0061]
On the other hand, a wire winding device 25 for winding and unwinding the wire 23 suspended in the furnace is provided above the upper chamber 21 of the manufacturing apparatus 12, and the seed attached to the seed holder 26 at the lower end of the wire 23. The crystal 28 can be moved up and down and rotated as necessary. In the illustrated example, a wire-type CZ method single crystal manufacturing apparatus is taken as an example, but this is the same with a shaft-type single crystal manufacturing apparatus that pulls a single crystal with a shaft (metal rod or the like) instead of the wire 23. .
[0062]
An optical temperature measuring device 22 that is an optical means for measuring the silicon melt surface temperature is attached to the outside of the viewing window 30 of the furnace body 14. The surface temperature of the polycrystalline silicon raw material or raw material melt M accommodated in the crucible C in the furnace can be measured by the temperature measuring device 22. This temperature measuring device 22 is connected to an operating condition control device 38 such as an operating condition control computer for appropriately controlling the growth environment in the furnace during single crystal growth, and the silicon flux measured by the temperature measuring device 22 is measured. The temperature of the liquid is taken in and processed by the operating condition control device 38 as needed. As an optical means for measuring the silicon melt surface temperature, a conventionally known one can be used in addition to the optical temperature measuring device 22 described above.
[0063]
And based on the result processed by this operation condition control device 38, the electric power of the heater 18 is controlled to a desired value by the heater power control device 40, and the melt temperature in the crucible C is adjusted to a temperature corresponding to the process. To do.
[0064]
FIG. 2 shows an example of a processing flow for detecting the end of melting of the polycrystalline silicon raw material according to the present invention using the operation condition control device 38. Hereinafter, the processing procedure in the method of the present invention will be described in detail with reference to FIG.
[0065]
The operation condition control unit 38 includes operation condition data for growing a single crystal in advance and a set value T1 of a temperature fluctuation range used for detecting the end of melting of the polycrystalline silicon raw material through an input device such as a keyboard. In order to prevent the melt temperature from excessively rising due to the time during which the melt surface temperature is continuously measured when the temperature falls below the set value T1, that is, the temperature fluctuation observation time t2 until the determination and the heater heating after the melting of the raw material is completed. The upper limit value T2 of the melt heating temperature to be set and the time to wait for the raw material to melt to some extent after the supply of electric power to the heater 18 is started, that is, the waiting time t1 until the start of determination is input (step). 100).
[0066]
As the set value T1 of the temperature fluctuation range, 30 ° C to 100 ° C, preferably 40 ° C to 60 ° C is used. If this fluctuation range exceeds 100 ° C., the end of melting cannot be detected completely, and if it does not reach 30 ° C., the end of melting cannot be detected despite the fact that melting has actually ended. Too much.
[0067]
The temperature fluctuation observation time t2 until the above determination is preferably 5 minutes or more at least because it may cause an error if it is shorter than necessary. On the other hand, if it is too long, useless time will be consumed. The time to continue the measurement of the temperature of the silicon melt should be within 30 minutes because it causes problems such as deterioration of the crucible wall, and is preferably about 10 minutes for efficient and loss of process time. Less.
[0068]
The upper limit value T2 of the melt heating temperature may be set to a temperature exceeding the melting point of silicon (1420 ° C.), for example, about 1480 ° C. to 1600 ° C., specifically about 1500 ° C. is appropriate. .
[0069]
First, electric power is supplied to the heater 18 to start melting the polycrystalline silicon material (step 101). After a time t1 until the raw material in the crucible C melts to some extent (step 102), the temperature measuring device 22 starts measuring the temperature T of the raw material melt M in the crucible C (step 103). The maximum value Tmax and the minimum value Tmin of the dispersion of the melt temperature T are obtained from the measurement data, and the difference between the maximum value Tmax and the minimum value Tmin is inputted in advance as the actual fluctuation range ΔT of the melt temperature T (step 104). The actual fluctuation range ΔT is larger than the fluctuation range setting value T1 (NO in step 105). Then, the process returns to step 103 and the melt temperature T is set. Continue measurement.
[0070]
Thereafter, when the melting progresses and the actual fluctuation range ΔT of the melt temperature becomes smaller than the preset fluctuation range setting value T1 (YES in step 105) [this time point is defined as the first melting end point. It is also possible to proceed to the end of melting of the polycrystalline raw material (step 108). ], The process proceeds to the next step, the temperature measurement of the melt temperature T is continued for a predetermined time t2 of 5 minutes or more set in advance, and the actual temperature fluctuation width ΔT during that time and the preset setting The temperature fluctuation width T1 is compared (step 106), and if ΔT <T1 (YES in step 106), the time when the predetermined time t2 has elapsed is determined as the second melting end point, and the polycrystalline raw material At the end of melting (step 108), the amount of heater power is reduced to lower the temperature of the raw material melt (step 109).
[0071]
The minimum temperature Tmin of the melt temperature T measured while the actual temperature fluctuation width ΔT is equal to or less than the set temperature fluctuation width T1 is stored in the operation condition control device 38 as the seed crystal landing temperature ST. (Step 107) If the temperature lowering operation of the melt M after the end of melting is controlled so as to stabilize at the seed crystal deposition temperature ST at this time in a short time, the temperature lowering operation can be efficiently advanced.
[0072]
That is, the melt temperature T is compared with the measured melt temperature minimum value Tmin (step 110). If T ≦ Tmin (YES in step 110), the temperature lowering process of the raw material melt is terminated (step 111). ), Seed crystals are deposited on the raw material melt (step 112). If T ≦ Tmin is not satisfied in step 110 (NO in step 110), the process returns to step 109 to lower the temperature of the raw material melt.
[0073]
The actual temperature fluctuation range ΔT (measured temperature maximum value Tmax−minimum value Tmin) after the actual temperature fluctuation range ΔT of the melt M becomes equal to or less than the set temperature fluctuation range T1 and before the set time t2 elapses. When the temperature exceeds the set temperature fluctuation range T1 (NO in step 106), the process returns to step 103 and waits for the set time t2 to elapse while measuring the melt temperature T from that point (steps described later). When 106a is omitted).
[0074]
On the other hand, since the melt M is continuously heated by the heater 18 until the end of melting is detected, there is a problem that the measurement is inadvertently continued. In order to prevent this, after the actual temperature fluctuation width ΔT of the melt M becomes equal to or less than the set temperature fluctuation width T1, if ΔT <T1 is not satisfied in step 106, that is, the actual temperature fluctuation width of the melt M. When ΔT exceeds the set temperature fluctuation range T1 (NO in step 106), the set upper limit value T2 of the melt temperature T is compared with the melt temperature T (step 106a), and a temperature measuring device is obtained. When the temperature measured by the temperature 22 exceeds the predetermined temperature (upper limit value T2) (YES in step 106a), this time is determined as the third melting end point, and the raw material is not waited for the set predetermined time t2 to elapse. If the setting is made so as to proceed to the end of melting (step 108) and the temperature lowering step (step 109) of the melt M, the end detection of the melting step becomes more reliable. If the melt temperature T does not reach the upper limit value T2 in step 106a (NO in step 106a), the process returns to step 103 in the same manner as described above, and the predetermined time set while measuring the melt temperature T. Wait for t2 to elapse.
[0075]
2 shows a flow in which the step of comparing the melt temperature T and the upper limit value T2 (step 106a) is executed only when ΔT <T1 is not satisfied in step 106 (NO in step 106). However, the comparison process of the melt temperature T and the upper limit value T2 is not limited to the processing flow of FIG. That is, after ΔT <T1 in step 105 (YES in step 105), the variation range of the melt temperature is equal to or less than the predetermined value while the measurement of the melt temperature is continued for the set predetermined time t2. However, since the melt temperature may increase, it is necessary to set the upper limit value T2 of the melt temperature T and to determine the third melting end point when reaching the temperature. Therefore, even when the fluctuation range of the melt temperature is equal to or less than the predetermined value during the predetermined time t2, the above-described comparison process between the melt temperature T and the upper limit value T2 is executed and is performed by the temperature measuring device 22. When the measured temperature of the melt exceeds a predetermined temperature (upper limit value T2), this time is determined as the third melting end point, and the melting of the raw material is completed without waiting for the elapse of the predetermined time t2 (step 108). And it sets so that it may transfer to the temperature fall process (step 109) of the melt M.
[0076]
In the method of the present invention, when the average value of the melt temperature measurement value after the actual temperature fluctuation range ΔT becomes ΔT <T1 exceeds 1500 ° C., It is preferable to do this.
[0077]
The silicon single crystal manufacturing apparatus of the present invention can adopt the configuration shown in FIG. 4 in addition to the configuration shown in FIG. Since the basic configuration of the manufacturing apparatus 12a in FIG. 4 and the manufacturing apparatus 12 in FIG. 1 are the same, the differences will be described below, and the re-explanation of other configurations will be omitted. 4, the same members as those shown in FIG. 1 are denoted by the same reference numerals. In the manufacturing apparatus 12a of FIG. 4, in addition to the configuration of the manufacturing apparatus 12 of FIG. 1, an imaging viewing window 30a is opened outside the furnace body 14, and the outside of the imaging viewing window 30a is accommodated in the crucible C. A television camera which is an image pickup device 42 for picking up an image of the silicon melt surface is attached. The image (signal) of the silicon melt M captured by the television camera 42 is sent to the image treatment device 44 connected to the subsequent stage of the television camera 42, and the polycrystalline silicon floating on the silicon melt surface and the melt surface. A binarization process is performed to convert the silicon raw material lump into an electric signal that becomes “0 value” or “1 value”.
[0078]
Normally, the threshold value is set in the image processing device 44 so that the input signal intensity is “1 value” when the intensity is greater than or equal to a predetermined illuminance, and “0 value” when the intensity is less than that. Compared with the threshold value, the signal conversion is performed with the raw material lump having a metallic luster and high illuminance as “1 value” and the silicon melt having a lower illuminance than the raw material lump as “0 value”. FIG. 5 shows a photographic screen image of the silicon melt surface after binarization when the polycrystalline silicon raw material lump is “1 value” and the silicon melt is “0 value”. FIG. 5A shows a state where the raw material lump is suspended in the silicon melt. In FIG. 5A, when the polycrystalline silicon raw material remains undissolved, it floats on the melt, and when the imaging screen is binarized, the raw material lump having a metallic luster can be recognized as white. FIG. 5B shows a state where all the raw material lump floating on the silicon melt surface is melted and only the silicon melt surface is photographed. In FIG. 5B, when the polycrystalline silicon raw material is completely melted, the binarized screen appears as a black image.
[0079]
The signal output from the image processing device 44 then enters the operating condition control computer 38, which is an operating condition control device, and is subjected to arithmetic processing together with the temperature of the silicon melt M measured by the temperature measuring device 22. It is also desirable to adopt an apparatus configuration that allows subsequent control of the manufacturing apparatus 12a based on the result.
[0080]
In addition, without using the temperature information of the silicon melt measured by the temperature measuring device 22, only the signal output from the image processing device 44 is put into the operation condition control computer 38 for calculation, and the manufacturing apparatus is based on the result. Control of 12a can also be performed. An example of the processing flow of the method for detecting the end of melting of the polycrystalline silicon raw material in this case is shown in FIG. In FIG. 6, first, a threshold value is set (step 200). Next, the silicon melt surface is imaged by the television camera 42 (step 201). The imaging data is sent to the image processing device 44 to perform binarization processing (with unmelted material → 1 value, without unmelted material → 0 value) (step 202). This binarization processing signal is sent to the operating condition control computer 38, the binarized screen is analyzed, and it is further determined whether or not all of the binarized screens are “0 value” (step 203). When all of the binarized screens are not “0 value”, that is, when “1 value” exists, the imaging of the silicon melt surface is performed again (step 201). When all of the binarization screens are “0 value”, this point is set as the fourth melting end point at which the melting of the polycrystalline silicon raw material is completed, and the melting of the polycrystalline silicon raw material is performed by the fourth melting end point. The end is detected, and the process proceeds to the melting end process (step 204).
[0081]
Furthermore, in order to make the detection result at this time more reliable, the configuration shown in FIG. 4 can be used, and the processing flow shown in FIG. 7 can be used.
[0082]
The processing flow for determining the end of melting shown in FIG. 7 is obtained by adding a binarization processing analysis step (step 300) of imaging data of the melt surface between step 105 and step 106 in the processing flow of FIG. It is. In this binarization processing analysis step, in order to more reliably detect that the polycrystalline silicon material contained in the crucible has completely melted, an image signal of the silicon melt surface from the TV camera 42 or the like is used. The binarization processing is performed by the image processing device 44, and based on the binarized signal, it is determined whether or not unmelted material exists on the surface of the polycrystalline silicon raw material, and then the subsequent processing flow is performed. I am trying to proceed.
[0083]
First, in the processing flow of FIG. 7, after the actual temperature fluctuation range ΔT satisfies the condition of ΔT <T1 with respect to the temperature fluctuation range setting condition T1 (YES in Step 105), the floating on the raw material melt surface is performed. Determine the presence or absence of an object. In the binarization processing analysis step (step 300), when the binarized signal after image processing is set to “raw material melt = 0” and “polycrystalline silicon raw material = 1”, the image signal of the taken silicon melt surface When all satisfy “0”, it is determined that all raw materials have been melted (YES in step 300), and the process proceeds to the subsequent processing flow.
[0084]
At this time, if the field of view of the TV camera is narrow and it is not possible to take a picture of the entire melt surface in the crucible at one time, the melting of the crucible is continued using the crucible rotation for more than one revolution. It is necessary to perform a judgment process over the entire surface of the liquid. If all the values are “0” on the binarization screen obtained by photographing the entire surface of the melt, it is determined that there is no raw material melt lump on the raw material melt surface.
[0085]
When the above conditions cannot be satisfied and a “1 value” signal indicating the presence of the raw material lump is input even in a part of the image signal (NO in step 300), the raw material melt temperature measurement (step Return to 103) and wait for the temperature to stabilize.
[0086]
In the processing flow of FIG. 7, the determination of the raw material lump floating in the silicon melt M is provided after step 105, but it may be positioned before step 105 or after steps 106 and 106a.
[0087]
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the method of the present invention, but the present invention is not construed as being limited thereto.
[0088]
Example 1
The method of the present invention was carried out using the same manufacturing apparatus as in FIG. First, a quartz crucible having a diameter of 60 cm is set in the manufacturing apparatus, 120 kg of polycrystalline silicon raw material is filled in the crucible, and 150 kw of electric power is supplied to the heater of the manufacturing apparatus to supply the polycrystalline silicon raw material. Was melted. At this time, the following conditions were input to the operation condition apparatus as determination conditions for detecting the end of the polycrystalline raw material, and the end of melting of the raw material melt was detected.
1) Waiting time from the start of charging to the end of melting determination (t1): 3 hours
2) Set value of temperature fluctuation range for determining the end of melting (T1): 50 ° C.
3) Time to maintain the actual temperature fluctuation range below the set value t1 in order to determine the end of melting (t2): 10 minutes
4) After the actual temperature fluctuation width becomes equal to or less than the set value T1 of the melting end condition, the upper limit value of the melt temperature (T2) forcibly determined to be the end of melting: 1500 ° C.
[0089]
As a result, the actual temperature fluctuation range becomes T1 or less after 230 minutes from the start of melting, and thereafter the actual temperature fluctuation range is maintained at T1 or less for 10 minutes. did. The measured temperature minimum value (Tmin) of the melt temperature during this determination is 1425 ° C., and the temperature is lowered with this temperature as the seed crystal deposition temperature. When the melt temperature is stabilized at the value of Tmin, the seed temperature is Crystals were deposited in the melt.
[0090]
The seed crystal settled in the melt without any problem, and it was possible to proceed to the next step again without adjusting the melt temperature. At this time, the time from the determination of the end of melting until the seed crystal was deposited in the melt was 50 minutes. FIG. 3 shows measured values of the melt temperature from the start of the melt temperature measurement until the seed crystal is deposited in the melt.
[0091]
(Comparative Example 1)
Using the same apparatus as in Example 1, the same amount of polycrystalline silicon was filled in a crucible of the same size and melted manually by the operator. It took 4 hours and 30 minutes to determine the end of melting. Further, it took 65 minutes to lower the melt temperature and stabilize it to the seed crystal deposition temperature.
[0092]
According to this result, it was confirmed that by using the method of the present invention, it was possible to automate the process from melting to cooling, which has been performed by the worker so far, and appropriate determination was performed by the apparatus also in the melting process and the cooling process. Therefore, it is thought that the process time was shortened.
[0093]
The present invention is not limited to the embodiment described above. The above-described embodiment is merely an example, and has substantially the same configuration as the technical idea described in the claims of the present invention, and any of the same effects can be obtained. Of course, it is included in the technical scope of the present invention.
[0094]
For example, in the apparatus of the present invention, after the end of melting of the polycrystalline silicon raw material is detected, the operation is automatically shifted to the temperature lowering operation of the melt temperature, but when the end of melting is detected, the buzzer or lamp is turned on to notify the operator. Such a simple device may be used. Even an apparatus that only detects the end of melting of a raw material can sufficiently obtain the effect because an artificial factor can be eliminated.
[0095]
Further, in the present invention, the initial melting in the single crystal growth process in which the raw material is charged into the crucible and melted to grow the single crystal has been described as an example. Of course, the present invention can also be applied to refilling raw material melting for single crystal production in a multiple pulling method in which a plurality of single crystals are grown from one crucible. In the method and apparatus of the present invention, the CZ method for growing a single crystal without applying a magnetic field to the raw material melt has been described as an example, but a single crystal rod is grown while applying a magnetic field to the raw material melt. Needless to say, the same effect can be obtained in the production of a single crystal using the MCZ method.
[Industrial applicability]
[0096]
As described above, in the production of a silicon single crystal using the CZ method, if the method for detecting the end of melting of the polycrystalline silicon raw material is used, the melting end point of the polycrystalline raw material is determined by the apparatus regardless of the experience of the operator. Will be able to judge. This stabilizes the work in the melting process of the single crystal production using the CZ method, and at the same time saves work and reduces the burden on the operator. In addition, since the melting of the polycrystalline raw material can be accurately detected and the melt temperature when the seed crystal is deposited in the silicon melt can be detected, the time from melting to immersing the seed crystal in the melt is shortened. It also leads to improved single crystal productivity.
[0097]
At the same time, since the time from the melting of the polycrystalline silicon raw material to the immersion of the seed crystal in the melt is shortened, heating of the crucible is reduced more than necessary, thereby suppressing the deterioration of the inner wall of the crucible. It is possible to cope with long-time operation. In particular, the effect is sufficiently exhibited in the long-time operation required for growing a long large-diameter single crystal.
[Brief description of the drawings]
[0098]
FIG. 1 is a schematic cross-sectional view showing an embodiment of an apparatus for producing a silicon single crystal according to the present invention.
FIG. 2 is a flowchart showing an example of a processing procedure of a method for detecting the end of melting of a polycrystalline silicon raw material.
FIG. 3 is a graph showing measured values of melt temperature from the start of melt temperature measurement in Example 1 until the seed crystal is deposited in the melt.
FIG. 4 is a schematic cross-sectional view showing another embodiment of the silicon single crystal production apparatus of the present invention.
FIG. 5 is a drawing showing a screen image of the silicon melt surface after binarization when the polycrystalline silicon raw material mass is “1” and the silicon melt is “0”; Is a state where the raw material lump of silicon melt is floating, and (b) is a state where all the raw material lump floating on the silicon melt surface is melted and only the silicon melt surface is photographed.
FIG. 6 is a flowchart showing another example of the processing procedure of the method for detecting the end of melting of a polycrystalline silicon raw material.
FIG. 7 is a flowchart showing another example of the processing procedure of the method for detecting the end of melting of a polycrystalline silicon raw material.
[Explanation of symbols]
[0099]
12: Single crystal manufacturing apparatus, 14: Furnace body, 15: Support shaft, 18: Heater, 20: Heat insulating material, 21: Upper chamber, 22: Temperature measuring device, 23: Wire, 25: Wire winding device, 26 : Seed holder, 28: seed crystal, 30: viewing window, 38: operating condition control device, 40: heater power control device.

Claims (4)

Filling the crucible in the single crystal manufacturing apparatus with polycrystalline silicon raw material, heating the heater to melt the polycrystalline silicon raw material, and then seeding the silicon melt with the seed crystal to grow the single crystal below the seed crystal A method for setting the seed crystal deposition temperature in the production of a silicon single crystal using the Czochralski method, and measuring the melt surface temperature when the polycrystalline silicon raw material contained in the crucible melts by optical means When the measured fluctuation range of the melt surface temperature becomes a predetermined value or less, the minimum value of the melt surface temperature measurement at that time is set as the first minimum melt surface temperature, and the first minimum melt surface temperature is set. Is a seed crystal deposition temperature when the seed crystal is deposited in the melt. Filling the crucible in the single crystal manufacturing apparatus with polycrystalline silicon raw material, heating the heater to melt the polycrystalline silicon raw material, and then seeding the silicon melt with the seed crystal to grow the single crystal below the seed crystal A method for setting the seed crystal deposition temperature in the production of a silicon single crystal using the Czochralski method, and measuring the melt surface temperature when the polycrystalline silicon raw material contained in the crucible melts by optical means Then, when the measured fluctuation range of the melt surface temperature of the silicon melt becomes less than the predetermined value, the melt temperature measurement is continued for 5 minutes or more. A seed crystal landing temperature setting method, characterized in that a liquid surface temperature is used, and the second minimum melt surface temperature is a seed crystal landing temperature when the seed crystal is deposited on the melt. Filling the crucible in the single crystal manufacturing apparatus with polycrystalline silicon raw material, heating the heater to melt the polycrystalline silicon raw material, and then seeding the silicon melt with the seed crystal to grow the single crystal below the seed crystal An apparatus for producing a silicon single crystal by the Czochralski method, the melt surface temperature measuring means for optically measuring the liquid surface temperature of the silicon melt contained in the crucible, and the melt surface temperature measuring means The maximum and minimum values of the melt surface temperature are obtained from the connected temperature data, and the difference between the maximum and minimum values is compared with the data input in advance as the fluctuation range of the melt surface temperature. Is less than the value of the previously input data, the operation condition control device that determines the end of melting of the polycrystalline silicon raw material and sends a heater power control signal, and the heater power control signal from this operation condition control device Base A heater power control device for lowering the power to the seed crystal deposition temperature, and based on data from a melt surface temperature measuring means for optically measuring the liquid surface temperature of the silicon melt contained in the crucible. Obtain the temperature fluctuation range of the melt surface, and use the minimum value of the melt surface temperature measurement value when this temperature fluctuation range is smaller than the value input in the control device as the seed crystal deposition temperature to set the heater power An apparatus for producing a silicon single crystal, wherein a control signal is sent. Filling the crucible in the single crystal manufacturing apparatus with polycrystalline silicon raw material, heating the heater to melt the polycrystalline silicon raw material, and then seeding the silicon melt with the seed crystal to grow the single crystal below the seed crystal An apparatus for producing a silicon single crystal by the Czochralski method, the melt surface temperature measuring means for optically measuring the liquid surface temperature of the silicon melt contained in the crucible, and the melt surface temperature measuring means The maximum and minimum values of the melt surface temperature are obtained from the connected temperature data, and the difference between the maximum and minimum values is compared with the data input in advance as the fluctuation range of the melt surface temperature. Is less than the value of the previously input data, the operation condition control device that determines the end of melting of the polycrystalline silicon raw material and sends a heater power control signal, and the heater power control signal from this operation condition control device Base The heater power control device for lowering the power of the crystal to the seed crystal deposition temperature, the imaging device for imaging the liquid level of the silicon melt accommodated in the crucible, and the binarized image captured by the imaging device An image processing device for processing, and when the image signal subjected to binarization processing by the image processing device falls below a threshold value, it can be determined that the melting of the polycrystalline silicon raw material has ended, and The temperature fluctuation range of the melt surface is obtained based on the data from the melt surface temperature measuring means that optically measures the liquid surface temperature of the silicon melt contained in the crucible, and this temperature fluctuation range is input into the controller. An apparatus for producing a silicon single crystal, characterized in that a heater power control signal is sent with the minimum value of the measured melt surface temperature when the temperature is smaller than the set value as a seed crystal deposition temperature.

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