JP5152128B2 - Method for producing compound semiconductor crystal - Google Patents

Description

  The present invention relates to a method for producing a compound semiconductor crystal, and more particularly to a method for producing a compound semiconductor crystal in which crystals are grown by the LEC method.

  A semiconductor material such as a substrate such as an IC or LSI is manufactured by thinly cutting a compound semiconductor crystal. There are various methods for producing this compound semiconductor crystal, and the LEC method is known as a commonly used method (see, for example, Patent Document 1).

  The LEC method referred to here simply puts a raw material and a liquid sealant in a crucible, melts them, contacts a seed crystal with this raw material melt, In this method, a single crystal compound semiconductor crystal is obtained by pulling up the seed crystal while sealing outflow.

  This LEC method is certainly used as a method for producing a compound semiconductor crystal. However, in the production process of a compound semiconductor crystal, crystal growth conditions such as the temperature of the raw material melt vary between crystal growths. The problem of fluctuating may arise.

  For example, as the crystal growth progresses, the remaining amount of the melt in the crucible decreases, the crystal growth interface protrudes into the raw material melt and comes into contact with the bottom of the crucible, and the growth cannot be continued. Even if the temperature fluctuation generated with the progress is small, there is a problem that the whole melt is solidified and the crystal and the crucible are fixed.

  In order to solve this problem, the present applicant provides an inclusion between the crucible and the susceptor that supports the crucible, and uses the heat stored in the inclusion during melting of the raw material to cause temperature fluctuations in the raw material melt. Has been developed (for example, see Patent Document 2).

JP-A-6-56582 JP 2009-23867 A

  On the other hand, factors that cause the crystal growth conditions to fluctuate between crystal growths are considered in addition to those described above, and examples include a change in the thermal conductivity of the crucible due to a change in the crucible wall thickness.

  As a material for the crucible, pBN (pyrolytic Boron Nitride) is generally used. However, since the wettability between boron trioxide generally used as a liquid sealant and the crucible made of pBN is good, trioxide is used. Boron tends to adhere to the inner peripheral surface of the crucible. Due to this fixing, the inner peripheral surface of the crucible is worn out. Further, every time this crucible is used for manufacturing a compound semiconductor crystal, this wear occurs, and as a result, the thickness of the crucible gradually becomes thinner.

By reducing the thickness of the crucible, the thermal conductivity of the heater for melting the raw material is increased, and the crystal growth conditions fluctuate each time the crucible is used. Furthermore, since the inner peripheral surface of the crucible is worn, the interface position between the raw material melt and boron trioxide before crystal growth fluctuates, so that the heat flow fluctuates in addition to the thermal conductivity. Become. Due to these fluctuations, the reproducibility of the temperature distribution in the raw material melt may not be obtained.

  In particular, after manufacturing a compound semiconductor crystal, the performance of the manufactured compound semiconductor crystal is measured, and the manufacturing process is modified so that the deviation from the compound semiconductor crystal obtained in the manufacturing process of the next compound semiconductor crystal is small. When a control method to be added (hereinafter also referred to as Run-to-Run) is used, the reproducibility of the compound semiconductor crystal manufacturing process is important in order to reduce the deviation. In spite of the importance of reproducibility, the crucible wall thickness is reduced as described above, so that the thermal conductivity and heat flow of the crucible fluctuate, and the reproducibility of the temperature distribution in the raw material melt is reduced. There is a risk that it will not be obtained. As a result, it becomes difficult to obtain a single crystal with good reproducibility by Run-to-Run, and it may be difficult to obtain a stable single crystal yield.

  An object of the present invention is to provide a method for producing a compound semiconductor crystal that ensures reproducibility of crystal growth conditions and obtains a stable single crystal yield.

The first aspect of the present invention includes a housing step of storing a raw material and a liquid sealant in a crucible supported by a susceptor, a melting step of heating the crucible and melting the raw material and the liquid sealant, A crystal growth step of bringing a seed crystal into contact with the raw material melt in the crucible, pulling up the seed crystal and growing the crystal to obtain a compound semiconductor crystal, and between the crucible and the susceptor before the crystal growth step And a correction step of correcting the thickness of the heat amount adjusting portion provided in advance so as to increase the thickness according to the amount of wear on the inner peripheral surface of the crucible.

A second aspect of the present invention is characterized in that, in the invention described in the first aspect, the heat amount adjusting portion before and after the correction step is made of the same material as the crucible.

A third aspect of the present invention is characterized in that, in the invention described in the first or second aspect, the calorific value adjustment part before and after the correction step is similar or identical to the crucible bottom shape.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, when the heat quantity adjustment part before and after the correction process is cylindrical, the heat quantity adjustment part before and after the correction process is outside of the heat quantity adjustment part. The diameter is the same as the outer diameter of the crucible.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the thickness of the calorific value adjusting part before and after the correction step is made thicker than the crucible bottom part thickness. And

A sixth aspect of the invention, Ri by the repeating compound manufacturing method of a semiconductor crystal according to the second, the sum of the wall thickness of the thick and the crucible bottom of the heat adjuster, at least each of the correction It is characterized by being constant in the process.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the compound semiconductor crystal which ensures the reproducibility of crystal growth conditions and obtains the stable single crystal yield can be provided.

It is a schematic sectional drawing of the LEC method crystal growth furnace in one Embodiment of this invention. It is a schematic sectional drawing of the LEC method crystal growth furnace in another embodiment of this invention. It is a schematic sectional drawing of the LEC method crystal growth furnace in another embodiment of this invention. It is a schematic sectional drawing of the LEC method crystal growth furnace in another embodiment of this invention. It is a schematic sectional drawing which shows the structure of the manufacturing apparatus of the conventional compound semiconductor crystal.

The present inventors have studied various methods for producing a compound semiconductor crystal that can ensure the reproducibility of the production process.
As a result, the inventors have previously provided a heat amount adjusting portion between the susceptor and the crucible, and even if the crucible wall thickness is reduced, the heat amount adjusting portion according to the amount of wear on the inner peripheral surface of the crucible. It was found that the thermal conductivity of the crucible can be maintained if the thickness is corrected.

  Below, the manufacturing method and the manufacturing apparatus of the semiconductor crystal which concern on one Embodiment of this invention are demonstrated. In the present embodiment, a manufacturing apparatus and a manufacturing method for manufacturing a GaAs single crystal by the LEC method (Liquid Encapsulated Czochralski method), which is one of manufacturing methods of a compound semiconductor crystal, will be described.

FIG. 1 is a schematic cross-sectional view showing a compound semiconductor crystal manufacturing apparatus according to an embodiment of the present invention.
As shown in FIG. 1, a growth furnace 100 composed of a pressure vessel is provided with a pulling shaft 1 for pulling up a single crystal, and a seed crystal 2 is attached to the tip of the pulling shaft 1.

  The pulling shaft 1 is inserted into the furnace from above the growth furnace 100 and is opposed to a crucible 3 installed in the furnace. The crucible 3 is supported by a pedestal 5 that can be rotated and moved up and down via a susceptor 4.

A single crystal raw material 6 and a liquid sealing material 7 are accommodated in the crucible 3. Examples of the raw material 6 include group III raw materials and group V raw materials, and examples of the liquid sealing material 7 include boron trioxide (B ₂ O ₃ ). As will be described later, the raw material 6 and the liquid sealing material 7 are melted in the crucible 3.

  The crucible 3 may be made of any material as long as it can be used for the production of a compound semiconductor crystal. Examples thereof include pBN, silicon, and materials containing these. In this embodiment, the crucible is made of pBN. The case will be described.

Further, the shape of the crucible 3 may be the same shape as that of a normal crucible, that is, a shape having an open top and a bottom 33 and a side 34. The side portion 34 may have a cylindrical shape or a shape formed by combining a plurality of plates. The shape of the bottom 33 may be a spherical shape having a predetermined curvature or a planar shape, but is preferably a spherical shape from the viewpoint of uniform temperature distribution. Further, in the bottom 33, an inner peripheral surface (hereinafter also referred to as a crucible bottom upper surface 331) that accommodates the raw material 6 and the liquid sealant 7 and an outer peripheral surface (hereinafter referred to as a crucible bottom lower surface 332) supported by the susceptor 4. ) May be similar or the same shape, or different shapes. For example, the crucible bottom upper surface 331 may be spherical and the crucible bottom lower surface 332 may be planar or vice versa.

  Here, in this embodiment, before the step of growing a single crystal from the seed crystal 2, a calorific value adjusting unit 11, which will be described in detail later, is provided between the crucible 3 and the susceptor 4. The thickness of the heat quantity adjusting unit 11 is corrected according to the crucible wear amount described later.

  The susceptor 4 is preferably made of the same material as the crucible 3. In this embodiment, since the material of the crucible 3 is pBN, it is preferable that the material of the susceptor 4 is also pBN. As will be described in detail later, it is easy to make the thermal conductivity constant when manufacturing a plurality of compound semiconductor crystals while performing Run-to-Run.

  The shape of the susceptor 4 may be the same shape as that of the susceptor 4 used for manufacturing a compound semiconductor crystal, that is, a shape that supports the bottom surface 332 of the crucible bottom. A shape that can accommodate the entire crucible 3 supported by the adjusting portion 11 is preferable. Specifically, when the crucible 3 has a cylindrical shape and the outer diameter of the heat amount adjusting unit 11 and the outer diameter of the crucible 3 are substantially the same, the outer diameter of the crucible 3 and the inner diameter of the susceptor 4 are substantially matched. It is desirable that the entire crucible 3 supported by the heat amount adjusting unit 11 and the heat amount adjusting unit 11 can be accommodated. This is because it becomes easy to make the thermal conductivity constant, and the temperature distribution of the raw material melt when the raw material 6 is melted can be made constant. In the present embodiment, a case will be described in which the crucible 3 and the susceptor 4 are cylindrical, and the crucible bottom upper surface 331 and lower surface 332 and the upper surface of the susceptor 4 are spherical.

The pedestal 5 is inserted into the growth furnace 100 from below the growth furnace 100 while being concentric with the pulling shaft 1, and the susceptor 4 is fixed to the upper end of the pedestal 5.
Further, the pedestal 5 and the pulling shaft 1 are rotated by a rotating device (not shown) provided separately, and are raised and lowered by a lifting device (not shown).

  Further, the growth furnace 100 is provided with a heater 8 and a temperature controller (not shown) for controlling the temperature of the heater 8 as heating means for melting the raw material 6 and the liquid sealing material 7. Further, a thermocouple 9 is provided as a temperature detecting means for detecting the temperature of the raw material 6 and the liquid sealing material 7 in the crucible 3.

  The heater 8 is installed in the furnace so as to surround the susceptor 4 along the outer periphery of the cylindrical susceptor 4 while being concentric with the susceptor 4. The thermocouple 9 is installed at the upper end in the shaft of the pedestal 5.

  The above is the configuration of the compound semiconductor crystal manufacturing apparatus. Next, a method for producing a compound semiconductor crystal will be described.

(Containment process)
First, the raw material 6 and the liquid sealant 7 are accommodated in the crucible 3 supported by the susceptor 4. At this time, the inside of the furnace is maintained in an inert gas atmosphere having a predetermined pressure. The pressure of the inert gas is set to such a level as to prevent dissociation of the group V material from the material 6 when the group III and group V materials are accommodated in the crucible 3 as the material 6.

(Melting process)
Next, the heater 8 is heated by the temperature controller. The crucible 3 is heated by the heating of the heater 8 to melt the raw material 6 and the liquid sealant 7 in the crucible.
Specifically, first, the temperature of the crucible 3 is caused to reach the melting temperature of the liquid sealing material 7 by the heating of the heater 8 to melt the liquid sealing material 7. The liquid sealant is melted before the raw material is melted, so that the liquid sealant contacts the bottom side of the inner peripheral surface of the crucible. Further, the temperature of the heater 8 reaches the melting temperature of the raw material 6 to melt the raw material 6. At this time, since the specific gravity of the melt of the raw material 6 is larger than the specific gravity of the liquid sealing material 7, the surface of the raw material melt is covered with the liquid sealing material 7. Thereby, dissociation of the V group element from the melt of the raw material 6 can be prevented.

(Crystal growth process)
After melting the raw material 6 and the liquid sealant 7, the seed crystal 2 fixed to the tip of the pulling shaft 1 is lowered by the lifting device, and passes through the liquid sealant 7 to contact the melt of the raw material 6. Then, while gradually lowering the temperature of the heater 8 by feedback control of the temperature controller, the pulling shaft 1 is slowly pulled up together with the seed crystal 2 by the lifting device in this state. By doing so, the crystal grows, and the growth crystal 10 that is a single crystal is pulled up through the liquid sealing material 7.

  When the grown crystal 10 is pulled up, the pulling shaft 1 and the pedestal 5 are both relatively rotated by the rotating device. Further, in order to control the outer diameter of the growth crystal 10 to be constant, the amount of weight increase per unit time of the growth crystal 10 is detected, and the outer diameter of the growth crystal 10 is calculated from this by calculating the crystal outer diameter. Thus, the heater 8 is feedback controlled by the temperature controller.

  Further, if the melt in the crucible 3 decreases as the crystal outer diameter grows, the liquid surface position inevitably decreases. When the liquid level is lowered, the positional relationship between the heater 8 and the crystal growth interface changes, and it becomes difficult to efficiently heat the melt. For this reason, the amount of decrease in the liquid level is calculated from the amount of crystal growth, and the lifting device is controlled based on the calculation result. Specifically, the pedestal 5 is gradually raised to adjust the position of the crucible 3 in accordance with the lowering of the liquid level, and the liquid level of the melt is always adjusted to a fixed position with respect to the tropics of the heater 8. Control is executed.

(Wear measurement process)
After the crystal growth step, if necessary, the amount of wear on the inner peripheral surface 31 of the crucible that has been in contact with the liquid sealant 7 is measured.
As described above, the liquid sealing agent 7 adheres to the inner peripheral surface 31 of the crucible, so that the inner peripheral surface 31 of the crucible is worn out. As the thickness of the crucible 3 is reduced due to this wear, the thermal conductivity of the heater 8 for melting the raw material 6 increases with respect to the heat, and the reproducibility of the temperature distribution in the raw material melt is lost. Every time 3 is used, the crystal growth conditions change. As a result, it becomes difficult to obtain a single crystal with good reproducibility. In addition, the deterioration of reproducibility due to this wear is particularly affected by wear at the bottom of the crucible.

Therefore, in the present embodiment, the amount of wear of the crucible inner peripheral surface 31 is measured as a preparatory preparation for preventing a change in thermal conductivity due to wear of the crucible inner peripheral surface 31 in the correction step described later. To do. As the measuring method, an existing method capable of examining the amount of wear may be used. For example, an ultrasonic thickness meter that measures the thickness according to the time required for the ultrasonic wave to reciprocate in the measurement object may be used.
In addition, this process does not need to be performed when using the method in which the amount of wear of the crucible inner peripheral surface 31 can be predicted. For example, the wear amount may be calculated in advance from the furnace pressure, the raw material melt amount, the set temperature of the heater 8, the time spent for the crystal growth process, the material of the crucible, the outer diameter / inner diameter, the wall thickness, and the like.

(Correction process)
In the present embodiment, the thickness of the calorific value adjusting unit 11 provided in advance between the crucible 3 and the susceptor 4 before the crystal growth step is obtained in the predicted wear amount or the wear measurement step. Correct according to the amount of wear. That is, the thickness of the heat quantity adjusting unit 11 is corrected so as to compensate for the wear of the crucible 3 due to the crystal growth process. Thereby, the thermal conductivity before the crystal growth process, that is, before the crucible 3 is worn out, and the thermal conductivity in the crystal growth process when a compound semiconductor crystal is newly manufactured after manufacturing the compound semiconductor crystal are made equal. As a result, the reproducibility of the temperature distribution in the raw material melt can be ensured. As a result, a stable single crystal yield can be obtained in the manufacturing process of the chemical semiconductor crystal.

  In the above-described configuration, when the production of the compound semiconductor crystal is repeated, when using Run-to-Run, in which the reproducibility of the production process of the compound semiconductor crystal is important, the temperature distribution in the raw material melt is well reproduced. As a result, the deviation between a plurality of compound semiconductor crystals can be reduced, which is more effective.

  A specific correction method performed in the correction step is, for example, that at least a part of the heat amount adjusting unit 11 provided in advance before the crystal growth step is used for the predicted wear amount or the wear measurement. There is a method of correcting by replacing at least a part of the calorie adjustment unit to which the wall thickness corresponding to the amount of wear obtained in the process has been added to form a new calorie adjustment unit. For example, the new heat amount adjustment unit having a thickness corresponding to the amount of wear of the crucible 3 (for example, the thickness obtained by adding the thickness removed from the crucible bottom upper surface 331) and the entire heat amount adjustment unit 11 before correction are replaced. May be.

  At this time, as shown in FIG. 2, not only the thickness obtained by adding the shaved thickness on the crucible bottom upper surface 331 but also the thickness obtained by adding the shaved thickness on the side portion 34 of the crucible inner peripheral surface 31. You may replace | exchange the new heat amount adjustment part which has, and the whole heat amount adjustment part before correction | amendment.

  Further, as shown in FIG. 3, a part 111 of the heat amount adjusting unit 11 is detachably attached to the crucible side heat amount adjusting unit 11a and the susceptor side heat amount adjusting unit 11b, and only the part 111 is placed on the top surface of the crucible bottom. Substituting a part of the calorie adjustment part reflecting the shaved thickness in 331, the sum of the wall thickness of the crucible 3 before the crystal growth process and the calorie adjustment part 11, the crucible 3 after the correction process, and a new one You may comprise so that the sum of the wall thickness with a proper calorie | heat amount adjustment part may be made the same. At this time, the crucible side heat amount adjusting unit 11 a and the susceptor side heat amount adjusting unit 11 b may be fixed integrally with the crucible 3 and the susceptor 4.

  By exchanging at least a part of the calorie adjusting part 11 in this way with a part of the calorie adjusting part whose thickness is adjusted, that is, a part of the calorie adjusting part to which the thickness corresponding to the wear amount is added, the calorie adjustment The correction process can be performed more easily than exchanging the entire portion 11. Furthermore, if a part of the calorific value adjusting unit 11 having various thicknesses is prepared in advance, the calorific value adjusting unit 11 can be easily corrected every time a semiconductor crystal is manufactured.

  As a preferred example, in the cylindrical heat amount adjusting portion 11, the crucible side heat amount adjusting portion 11a and the susceptor side heat amount adjusting portion 11b are detachable from the crucible 3 and the susceptor 4, and a portion 111 other than these portions is a circle. It is good also as a plate-shaped part. If this method is used, the amount of heat can be adjusted by replacing the disk-shaped portion having a thickness corresponding to the amount of wear with only the portion 111 sandwiched between the crucible 3 and the portion in contact with the susceptor during the correction process. The part 11 can be easily corrected.

Further, as another specific correction method, the calorific value adjustment unit 11 provided in advance before the crystal growth step corresponds to the predicted wear amount or the wear amount obtained in the wear measurement step. There is a method of correcting as a new heat quantity adjusting unit by adding a part 112 of the heat quantity adjusting unit having a disk shape with a thickness instead of replacing it. As shown in FIG. 4, the portions 11a and 11b in contact with the crucible 3 and the susceptor 4 in the heat quantity adjusting unit 11 are detachable from the crucible 3 and the susceptor 4, and the portions 111 and 112 other than these portions are used in this embodiment. Is a disk-shaped part. According to this method, the amount of heat is obtained by sandwiching a disk-shaped portion 112 having a thickness corresponding to the amount of wear between the crucible side heat amount adjusting unit 11a and the susceptor side heat amount adjusting unit 11b during the correction process. The adjustment unit 11 can be easily corrected.
Note that this method may be combined with the specific first correction method described above. That is, a disc-shaped portion having a predetermined thickness may be sandwiched between the crucible side heat amount adjusting unit 11a and the susceptor side heat amount adjusting unit 11b while replacing a part of the heat amount adjusting unit 11.

  Here, in the calorie | heat amount adjustment part 11 before and behind the said correction | amendment process, it is preferable to use the same material as the crucible 3. FIG. As described above, since it is required to suppress the change in the thermal conductivity of the crucible 3 before and after the crystal growth process, if the calorific value adjusting portion 11 is made of the same material as the crucible 3, the crucible 3 This is because, even if worn out, the heat quantity adjusting unit 11 can be corrected in accordance with the amount of wear without considering the difference in thermal conductivity due to the difference in material between the heat quantity adjusting unit 11 and the crucible 3.

  Furthermore, it is desirable that the heat quantity adjusting unit 11 is made of the same material as the crucible 3 and at the same time the heat quantity adjusting unit 11 is made of the same material as the susceptor 4. As described above, the thermocouple 9 for detecting the temperature of the raw material melt that controls the temperature of the heater 8 is provided at the upper part in the shaft of the pedestal 5 that supports the lower surface of the susceptor 4. If the crucible 4, the heat amount adjusting unit 11 and the susceptor 4 are made of the same material, by making the total value of these thicknesses constant, the difference in material between the crucible 4, the heat amount adjusting unit 11 and the susceptor 4 This is because the thermal conductivity can be kept almost constant without considering the difference in thermal conductivity.

  Moreover, about the shape of the calorie | heat amount adjustment part 11, what is necessary is just to match | combine with the shape of the crucible 3 and the susceptor 4, and a cylindrical shape may be sufficient as a whole shape, and a rectangular parallelepiped shape may be sufficient as it. On the other hand, the shape of the upper surface and the lower surface may be a planar shape, a shape obtained by partially deforming the planar shape, or a spherical shape. However, as shown in FIG. It is also preferable to make the shape in close contact with the crucible 3. With such a shape, it is possible to eliminate a gap between the crucible 3 and the calorie adjusting unit 11, and to suppress a variation in thermal conductivity due to a difference in thickness between the calorie adjusting unit 11 and the crucible 3. Because.

  Similarly, it is also preferable that the heat amount adjusting unit 11 before and after the correction process has a shape that can be in close contact with the susceptor 4. This is because a gap can be eliminated between the two, and fluctuations in thermal conductivity before and after the crystal growth process in the crucible 3, the heat amount adjusting unit 11, and the susceptor 4 can be suppressed.

  In particular, it is more preferable that these preferable shapes are put together to make the heat amount adjusting portion 11 before and after the correction step similar or identical to the shape of the crucible bottom portion 33. With such a shape, there is almost no gap between the heat amount adjusting unit 11 and the crucible 3 and the susceptor 4, so that the thermal conductivity can be maintained more constant.

As described above, in this embodiment, the crucible bottom upper surface 331 and the lower surface 332 are described as having a spherical shape. Specifically, the curvature radius of the bottom upper surface 332 of the crucible 3 and the aforementioned It is preferable to make the curvature radius of the upper surface of the heat amount adjusting unit 11 before and after the correction process the same. In addition to this, it is preferable that the radius of curvature of the susceptor upper surface 41 and the radius of curvature of the lower surface of the heat quantity adjusting unit 11 before and after the correction process are the same. With such a shape, there is almost no gap between the heat amount adjusting unit 11 and the crucible 3 and the susceptor 4, so that the thermal conductivity can be maintained more constant.

  Further, the outer diameter of the heat quantity adjusting unit 11 before and after the correction step may be the same as the outer diameter of the crucible outer peripheral surface 32. This is because by adopting such a configuration, the heat amount adjusting unit supports the entire crucible bottom lower surface 332, and fluctuations in thermal conductivity can be suppressed. Furthermore, since both have the same outer diameter, both can be accommodated in a susceptor having a constant inner diameter, and the manufacturing process becomes easy.

Moreover, it is also preferable to make the thickness of the heat quantity adjusting unit 11 thicker than the thickness of the crucible bottom 33. By adopting such a configuration, the influence of the thickness of the calorie adjusting portion 11 becomes more dominant in the thermal conductivity. Therefore, even if the thickness of the crucible bottom 33 is reduced and thinned, the heat conduction This is because fluctuations in sex can be suppressed.
Further, the thickness of the heat quantity adjusting unit 11 as a whole need not be constant in the vertical direction, but is preferably constant from the viewpoint of keeping the thermal conductivity constant and facilitating the correction process.

  In addition, when a plurality of compound semiconductor crystals are manufactured by repeating the method of manufacturing a compound semiconductor crystal, the sum of the thickness of the calorific value adjusting unit 11 and the thickness of the crucible bottom 33 is constant in at least each correction step. It is preferable that When using Run-to-Run where the reproducibility of the manufacturing process of the compound semiconductor crystal is important, the heat conduction is achieved by making the sum of the thickness of the heat quantity adjusting unit 11 and the thickness of the crucible bottom 33 constant. This is because fluctuations in sex can be suppressed.

  The above correction similar to that of the crucible bottom 33 is performed in consideration of the thickness of the crucible inner peripheral surface 31 as well as the thickness obtained by adding the thickness of the crucible bottom top surface 331. 34 may be performed.

  As described above, according to the present embodiment, it is possible to provide a compound semiconductor crystal manufacturing method that ensures reproducibility of crystal growth conditions and obtains a stable single crystal yield. The compound semiconductor crystal manufactured according to this embodiment is suitable for a semiconductor device using a semiconductor material such as IC or LSI.

  In the present embodiment, the growth crystal 10 is a GaAs single crystal, but it may be a silicon single crystal. In addition, although the case where the material of the crucible 3 is pBN has been described, the wear of the inner peripheral surface of the crucible 3 occurs even when other materials such as silicon are used, the above technical idea is applied. sell. In the present embodiment, the heat amount adjusting unit 11 is provided in advance. However, the heat amount adjusting unit 11 having a thickness corresponding to the crucible wear amount may be provided after the crystal growth step.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 which is a schematic cross-sectional view of an LEC crystal growth furnace.

Example 1
A pBN crucible 3 having a diameter of 300 mm and a bottom wall thickness of 4 mm was filled with 40 kg of a GaAs polycrystalline raw material and 3 kg of boron trioxide as a liquid sealing material 7 and placed in a growth reactor 100 as a pressure vessel.

The pBN crucible 3 containing the raw material 6 was stored in a graphite susceptor 4. At this time, a pBN-made heat quantity adjusting unit 11 having a thickness of 5 mm was accommodated between the susceptor 4 and the crucible 3, and the total thickness of the pBN was 9 mm by totaling the thickness of the crucible bottom 33.
The pBN heat quantity adjusting section 11 is the same as the outer diameter and bottom shape of the crucible 3, and the upper surface thereof has the same curved surface shape as the bottom surface 332 of the crucible and the lower surface has a curved surface shape with the susceptor upper surface 41. Were the same.

  The susceptor 4 in which these were accommodated was placed on a graphite pedestal 5 that can be rotated and moved up and down.

  After charging the raw material 6 and the liquid sealant 7 to the crucible 3, the atmosphere in the growth furnace 100 was evacuated by evacuation and then filled with an inert gas.

  Next, the temperature in the crucible 3 was raised to 1238 ° C. or higher, which is the melting point of GaAs, and the GaAs polycrystalline raw material as the raw material 6 was melted. At this time, the pressure in the furnace was 0.5 MPa.

  Next, the pulling shaft 1 is lowered, the tip of the seed crystal 2 is brought into contact with the raw material melt 6, and the temperature is sufficiently adjusted, and then the set temperature of the heater 8 is lowered by a temperature controller at a rate of 3 ° C./h. The seed crystal 2 was pulled up at a speed of 8 to 12 mm / h. During crystal growth, the seed crystal 2 and the crucible 3 were rotated by the pulling shaft 1 and the pedestal 5. At this time, the rotation speed of the seed crystal 2 was 5 rpm clockwise, and the rotation speed of the crucible 3 was 20 rpm counterclockwise.

  When the growth of the crystal shoulder was completed and the diameter became about 160 mm, automatic control of the outer diameter of the grown crystal 10 was started by the outer diameter controller. This is because the weight of the grown crystal is measured in real time by a load cell (not shown) installed on the pulling shaft 1 and the outer diameter of the crystal is monitored from the increase in weight per unit time and the moving amount of the pulling shaft 1. Then, feedback is performed to a temperature controller that controls the temperature of the heater 8 so that the outer diameter becomes a set value. As described in the embodiment, during crystal growth, the amount of melt gradually decreases and the liquid level position decreases as the amount of crystal growth increases. In order to correct this, the amount of decrease in the liquid level was calculated from the load cell output, and control was performed to automatically raise the crucible 3 so that the liquid level was always at a fixed position with respect to the heater 8.

  The temperature of the heater 8 was raised at the time when the grown crystal was pulled until the charged raw material 6 contained a predetermined weight, and after forming the tail shape of the crystal, the crystal was separated from the raw material melt and cooled to room temperature.

  The crucible 3 made of pBN taken out from the growth furnace 100 through this series of crystal growth processes is in contact with the boron trioxide 7 and the boron trioxide 7 is fixed, so that the inner peripheral surface 31 of the crucible is peeled off almost uniformly. The thickness of the crucible 3 was reduced by 0.1 mm. In order to manufacture another new compound semiconductor crystal, that is, to perform the second crystal growth, the crucible 3 having a reduced thickness was used again. At this time, in order to correct the scraped thickness of 0.1 mm, which is the amount of wear, the heat amount adjusting unit 11 made of pBN is changed from the thickness of 5.0 mm to 5.1 mm to adjust the crucible 3 and the heat amount. It arrange | positioned so that the total thickness with the part 11 might be set to 9.0 mm. A second crystal growth was performed under the same manufacturing conditions as the first except for the change of the calorific value adjustment unit 11. As a result, a second single crystal could be obtained.

  Similarly, after the third time, the thickness of the crucible 3 made of pBN was reduced and the thickness of the calorific value adjusting unit 11 was increased, and crystal growth was continuously performed 20 times. As a result, a single crystal was obtained in all crystal growth.

Furthermore, when the above experiment was conducted while changing the thickness of the crucible 3, a single crystal was stably obtained in crystal growth under the following conditions.
-The sum of the thickness of the bottom of the crucible and the thickness of the calorie adjusting portion is 5 mm or more.
-When the thickness of the bottom of the crucible is 1 mm or more and crystal growth is continuously performed, the crucible is replaced when the thickness of the bottom of the crucible falls below 1 mm.
-The thickness of the calorie adjustment part with respect to the thickness of the bottom part of the crucible is set within a range of 1 to 10 times.

  It should be noted that a desired single crystal could be obtained by providing a calorific value adjusting portion at a location corresponding to the crucible bottom 33 as in the present embodiment. However, in the case of growing a crystal with higher reproducibility, It is preferable to form a calorie adjusting portion also in the side portion 34.

  In this embodiment, the correction process is performed for each crystal growth process. However, depending on the reproducibility of crystal growth required and the quality of the single crystal, the correction process may be performed every time the predetermined thickness decreases. . Thereby, the frequency | count of a correction | amendment process can be reduced and productivity can be improved.

(Comparative example)
Hereinafter, as shown in FIG. 5, a comparative example in which GaAs crystal growth is performed using the LEC growth furnace 100 without providing a heat quantity adjustment unit will be described.
In the comparative example, the crystal growth was performed 10 times under exactly the same conditions as in the previous example, except that the growth furnace 100 was changed to the one shown in FIG. went. In the first four crystal growths, a single crystal was obtained, but in the 5th to 6th days, a polycrystal was generated in the middle of the straight body portion, and a single crystal could not be obtained.
Furthermore, in the 7th to 10th growth, polycrystals were generated at the stage of forming the shoulder, and a single crystal could not be obtained over the entire length. As a result, only four single crystals were obtained out of the total 10 crystal growths.

1 Pulling shaft 2 Seed crystal 3 pBN crucible 31 Crucible inner peripheral surface 32 Crucible outer peripheral surface 33 Crucible bottom 331 Crucible bottom upper surface 332 Crucible bottom lower surface 34 Crucible side 4 Susceptor 41 Susceptor upper surface 5 Pedestal 6 Raw material 7 Liquid sealant 8 Heater 9 Thermocouple 10 Growing crystal 11 Heat amount adjusting unit 11a Crucible side heat amount adjusting unit 11b Susceptor side heat amount adjusting unit 111 Part of removable heat amount adjusting unit 112 Part of heat amount adjusting unit to be added

Claims (6)

An accommodating step for accommodating the raw material and the liquid sealant in the crucible supported by the susceptor; a melting step for heating the crucible to melt the raw material and the liquid sealant; and a seed for the raw material melt in the crucible A crystal growth step of bringing a crystal into contact and pulling up the seed crystal to grow a crystal to obtain a compound semiconductor crystal;
A correction step of correcting the thickness of the heat amount adjusting portion provided in advance between the crucible and the susceptor before the crystal growth step so as to increase in accordance with the amount of wear on the inner peripheral surface of the crucible. A method for producing a compound semiconductor crystal, comprising: The method for producing a compound semiconductor crystal according to claim 1, wherein the heat amount adjusting portion before and after the correction step is made of the same material as the crucible. 3. The method of manufacturing a compound semiconductor crystal according to claim 1, wherein the heat amount adjusting portion before and after the correction step is similar to or the same shape as the shape of the bottom of the crucible. When said correction step before and after the heat adjuster a cylindrical shape, said correction step the outer diameter of the heat adjuster before and after any one of claims 1 to 3, characterized in that the same as the outer diameter of the crucible The manufacturing method of the compound semiconductor crystal of description. The method of manufacturing a compound semiconductor crystal according to any one of claims 1 to 4 , wherein the thickness of the heat amount adjusting portion before and after the correction step is made thicker than the thickness of the bottom portion of the crucible. Ri by the repeating the process for the preparation of a compound semiconductor crystal according to claim 2, the sum of the wall thickness of the wall thickness of the heat adjuster the crucible bottom, characterized in that the constant in at least each of the correction step A method for producing a compound semiconductor crystal.

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