JP3814893B2 - Crystal growth crucible and crystal growth apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crucible for crystal growth and a crystal growth apparatus for manufacturing a compound crystal such as GaP, GaAs, InP, etc. by a vertical Bridgman method or a vertical temperature gradient solidification method while applying a vapor pressure of its constituent elements. In particular, the present invention relates to an improvement of a crystal growth crucible and a crystal growth apparatus that can suppress abnormal growth and stably grow a compound crystal from the seed crystal accommodation position upward.
[0002]
[Prior art]
When producing a compound crystal such as GaP, GaAs, InP, etc. by the vertical Bridgman method or the vertical temperature gradient solidification method, the composition of the compound crystal is actively controlled to suppress dissociation of component elements (As, P) having a high dissociation pressure. Various measures are taken to control the above. For example, as a measure for suppressing dissociation, a liquid sealing agent such as B ₂ O ₃ is placed on the raw material melt in the crystal growth crucible, and the dissociation component element at a predetermined temperature is not higher than the vapor pressure. A method of crystal growth while applying an active gas to the surface of the liquid sealant is employed. As a composition control measure, a crucible for crystal growth is arranged on the upper side in the growth vessel, and a vapor pressure control reservoir containing a component element having a high dissociation pressure is arranged on the lower side in the growth vessel. At the same time, a method of growing crystals while applying vapors of the above component elements having a high dissociation pressure to the raw material melt surface in the crystal growth crucible is employed. The latter method can produce higher quality crystals than the former method, and is used as a method for obtaining high quality crystals.
[0003]
By the way, as a crystal growth apparatus for growing a compound crystal by a vertical Bridgman method or a vertical temperature gradient solidification method while applying a vapor of a component element having a high dissociation pressure, an apparatus having a structure as shown in FIG. 3 has been conventionally used. ing.
[0004]
That is, this crystal growth apparatus includes a vertical growth vessel a arranged substantially vertically as shown in FIG. 3, and a raw material and a seed crystal of a target compound crystal arranged above the growth vessel a. A substantially cylindrical crucible for crystal growth b accommodated with the seed crystal on the lower side, and a component element which is disposed on the lower side of the growth vessel a and has a high dissociation pressure of the compound crystal, and this component element And a reservoir (steam supply unit) c that supplies the vapor of the material to the surface of the raw material melt in the crystal growth crucible, and the action of heaters d1 and d2 arranged around the growth vessel a The upper side of the growth vessel a is set as a high temperature portion, and the lower side of the growth vessel a is set as a low temperature portion, and the reservoir c is arranged at the lowest temperature of the growth vessel a. The vapor pressure control is performed by controlling the temperature of the reservoir c.
[0005]
Further, the growth vessel a is arranged in a pressure vessel e as shown in FIG. 3, the space in the growth vessel a is independent in the pressure vessel e, and an inert gas that balances the internal pressure of the growth vessel a is pressurized. It is supplied into the container e and prevents the growth container a from being damaged by the internal pressure.
[0006]
The growth vessel a is mainly a closed vessel such as a quartz tube, but a semi-shield vessel made of graphite or boron nitride may be applied. When a compound crystal having a crystal growth temperature exceeding the softening point of quartz, such as GaP, is manufactured using a resistance heater, it must be a semi-shielded container. However, when a compound crystal such as GaAs or InP is manufactured, it is hermetically sealed. This is because both containers and semi-shielded containers can be used.
[0007]
The temperature distribution in the vertical direction in the high temperature part of the growth vessel a for growing the compound crystal is set such that the temperature at the upper end of the seed crystal is set to the melting point and the temperature is high above the high temperature part and low below. Further, it is desirable that the temperature gradient is small. For example, in the case of GaP or GaAs, the temperature gradient is set to 2 to 10 ° C./cm. Further, during crystal growth, a soaking zone (a temperature at which a component element having a high dissociation pressure has a vapor pressure equal to the dissociation pressure of the raw material) is provided in the low temperature portion of the growth vessel a, and vapor pressure control is performed.
[0008]
In order to realize these temperature distributions, the high temperature part and the low temperature part in the growth vessel a are temperature-controlled independently of each other. In general, the high-temperature part and the low-temperature part are cylindrical, and the same diameter heaters d1 and d2 are coaxially stacked in several stages, and a material having a low thermal conductivity between the high-temperature part and the low-temperature part ( Heat insulating material) is arranged.
[0009]
Then, the production of the compound crystal is completed by growing the crystal upward from the seed crystal by gradually lowering the temperature from the temperature distribution state in the growth vessel a, and then cooling to room temperature.
[0010]
Further, in the conventional crystal growth apparatus, after melting the raw material in the crystal growth crucible, the upper end of the seed crystal is melted to be seeded, and then the crystal growth crucible is gradually moved downward at a lower set temperature. The solid-liquid interface is moved upward by (vertical Bridgman method) or by gradually lowering the set temperature of the heater d1 in the high temperature part of the growth vessel a (vertical temperature gradient solidification method). That is, the compound crystal is grown upward from the seed crystal accommodation position (normal growth).
[0011]
[Problems to be solved by the invention]
By the way, in the crystal growth process of the compound crystal in the conventional crystal growth apparatus, the temperature difference between the solid-liquid interface and the raw material melt upper surface (solid-gas interface) gradually decreases. At the end of this crystal growth process, a phenomenon may occur in which the temperature of the upper surface of the raw material melt becomes lower than the temperature of the solid-liquid interface. When this phenomenon occurs, crystal nuclei are formed on the upper surface of the raw material melt, and crystals grow from the upper surface of the raw material melt toward the solid-liquid interface (this phenomenon is referred to as abnormal growth). Once this abnormal growth occurs, the normal growth up to that point (the crystal grows upward from the seed crystal accommodation position) and the abnormal growth proceed simultaneously, and crystal growth occurs where the two grown crystals collide. Will end.
[0012]
An abnormally grown crystal is not a product because the growth orientation is naturally different from that of a normally grown crystal. Therefore, when the phenomenon that the temperature of the upper surface of the raw material melt is lower than the temperature of the solid-liquid interface occurs and grows abnormally, the production yield of the compound crystal is lowered.
[0013]
The above-mentioned problems are likely to occur when growing a GaP crystal having a high crystal growth temperature (melting point: 1465 ° C.) and a high atmospheric pressure (phosphorus vapor pressure at the melting point is 35 kg / cm ² ), for example. This is because when the GaP crystal is grown, the gas convection above the raw material melt is intense, and the temperature oscillation on the upper surface of the raw material melt increases.
[0014]
The present invention has been made paying attention to such problems, and the problem is that the temperature of the upper surface of the raw material melt in the vertical Bridgman method or the vertical temperature gradient solidification method is lower than the temperature of the solid-liquid interface. Provided are a crystal growth crucible and a crystal growth apparatus capable of preventing abnormal phenomena and suppressing abnormal growth, allowing stable normal growth upward from a seed crystal, and capable of growing a compound crystal in high yield. There is.
[0015]
[Means for Solving the Problems]
That is, the invention according to claim 1
It is arranged on the upper side in a vertical growth vessel arranged substantially vertically, and the raw material and seed crystal of the compound crystal are accommodated with the seed crystal on the lower side, and the raw material is heated to the melt surface. On the other hand, a vertical Bridgman method for sequentially growing compound crystals from the seed crystal storage position upward while applying vapors of component elements having a high dissociation pressure of the compound crystals supplied from the lower side in the growth vessel, or Assuming a crucible for crystal growth applied to the vertical temperature gradient solidification method,
A substantially cylindrical crucible body having a seed crystal accommodating part on the bottom side and whose inner diameter continuously increases from the lower side to the upper side, and the outer peripheral edge of the crucible body are locked to the inner peripheral wall surface of the crucible body. And a circular partition plate having a vent hole for allowing the vapor of the component element having a high dissociation pressure to pass therethrough, and the locking position of the partition plate is set above the liquid surface of the raw material melt. It is characterized by that.
[0016]
And according to the crucible for crystal growth according to the present invention, the circular partition plate is disposed above the liquid surface of the raw material melt in the crucible body, and the space above the crucible main body and the upper surface of the raw material melt Since the space is partitioned, temperature fluctuations in the upper part of the raw material melt due to high-temperature gas convection above the raw material melt in the crucible body are suppressed.
[0017]
Therefore, the temperature of the upper surface of the raw material melt is kept higher than the temperature of the solid-liquid interface even at the end of the crystal growth process in which the temperature difference between the solid-liquid interface and the upper surface of the raw material melt becomes smaller in the vertical Bridgman method or the vertical temperature gradient solidification method. Therefore, abnormal growth from the upper surface of the raw material melt toward the solid-liquid interface can be suppressed.
[0018]
Further, since the partition plate has a vent hole through which the vapor of the component element having a high dissociation pressure passes, the vapor of the component element having a high dissociation pressure with respect to the raw material melt surface in the crucible body as in the conventional case. Crystals can be grown while being applied.
[0019]
In addition, when the crucible for crystal growth according to the present invention is incorporated in a crystal growth apparatus having a structure in which a high temperature distribution is easily formed in the center portion rather than the outer peripheral portion of the crucible, the vapor pressure of the component element is applied to the raw material melt surface. It is desirable to provide the ventilation hole for making it in the center part of a partition plate. This is because such an arrangement is effective in suppressing the formation of crystal nuclei on the upper surface of the raw material melt. Claims 2 to 3 are made for such technical reasons.
[0020]
That is, the invention according to claim 2
Based on the crucible for crystal growth according to the invention of claim 1,
A plurality of ventilation holes having an inner diameter of 2 mm or less are provided in the central portion of the partition plate,
The invention according to claim 3
A single ventilation hole having an inner diameter equal to or less than a radius of the partition plate is provided at a central portion of the partition plate.
[0021]
Next, the invention according to claim 4 relates to a crystal growth apparatus to which the crystal growth crucible according to the present invention is applied.
[0022]
That is, the invention according to claim 4
A vertical growth vessel arranged substantially vertically, a crucible for crystal growth arranged on the upper side of the growth vessel and containing the raw material and seed crystal of the compound crystal with the seed crystal on the lower side, and the growth vessel And a vapor supply unit that contains a component element having a high dissociation pressure of the compound crystal and supplies a vapor of this component element to the raw material melt surface in the crucible for crystal growth, On the premise of a crystal growth apparatus for growing the above compound crystal by the Bridgeman method or the vertical temperature gradient solidification method,
The said crystal growth crucible is comprised by the crystal growth crucible in any one of Claims 1-3.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0024]
That is, the crystal growth crucible 1 according to the present invention has a seed crystal accommodating portion 10 on the bottom side as shown in FIG. 1A and its inner diameter continuously increases from the lower side to the upper side. A substantially cylindrical crucible main body 11 and a circular partition plate 12 having an outer peripheral edge locked to an inner peripheral wall surface of the crucible main body 11 and having a vent hole 13 through which vapor of a component element having a high dissociation pressure passes. It is composed. The slope angle of the wall surface in the crucible body 11 is arbitrary in principle, but is usually set in the range of 1 to 3 degrees (the conventional wall surface is not tilted and the slope angle is 0 degree).
[0025]
As shown in FIG. 1A, the target compound crystal raw material (usually the target compound crystal is a compound single crystal in the crucible body 11, and in this case, in principle, the compound polycrystal is the above raw material. (In some cases, the component elements before compound synthesis may be used as raw materials.) 2 and seed crystal 3 are charged, and after the partition plate 12 is placed on the charged raw material 2, the crystal is grown. The crucible 1 is set at a predetermined position in the growth vessel 50 of the crystal growing apparatus 5 shown in FIG. FIG. 1B shows a cross section in the crucible body 11 when the upper ends of the raw material 2 and the seed crystal 3 are melted by this temperature rise (at the start of crystal growth). Then, the inner diameter of the crucible body 11 and the size of the partition plate 12 are arranged so that the locking position of the partition plate 12 is disposed above the liquid surface of the raw material melt 2 ′ as shown in FIG. Has been adjusted. Normally, the locking position of the partition plate 12 is set at a location several mm from the liquid level of the raw material melt 2 ′.
[0026]
Examples of the partition plate 12 include those provided with a vent hole 13 only in the central portion, those provided with a plurality of vent holes of 2 mm or less, and the like. A vapor of a component element having a high dissociation pressure supplied from a reservoir 6 disposed on the side is applied. The material of the partition plate 12 is arbitrary as long as it is a material that does not react with the constituent elements and the crucible body 11 and does not generate a problematic impurity, but is preferably the same as the material of the crucible body 11. Good. For example, when quartz is applied as the crucible body, a partition plate made of quartz can be applied, but a partition plate made of P-BN (pyrolytic boron nitride) may be applied.
[0027]
Next, a crystal growth apparatus according to the present invention includes a substantially cylindrical crucible body having a seed crystal accommodating part on the bottom side and an inner diameter continuously increasing from the lower side toward the upper side, and the crucible body. Except for the point that a crucible for crystal growth composed of a circular partition plate having a vent hole through which the outer peripheral edge is locked to the inner peripheral wall surface and the vapor of the component element having a high dissociation pressure passes is incorporated. This is almost the same as the crystal growth apparatus.
[0028]
That is, the crystal growth apparatus 5 according to the present invention includes a vertical growth vessel 50 arranged substantially vertically as shown in FIG. 2, and a raw material and a seed crystal of a compound crystal arranged above the growth vessel 50. The crucible 1 for crystal growth to be accommodated and the component element which is disposed below the growth vessel 50 and has a high dissociation pressure of the compound crystal are accommodated, and the vapor of this component element is contained in the crucible 1 for crystal growth. The main part is constituted by the reservoir 6 supplied to the raw material melt surface, and three cylindrical heaters 71, 71, 71 are provided in the vicinity of the outer periphery of the growth vessel 50 at the location where the crystal growing crucible 1 is disposed. In addition, one cylindrical heater 72 is provided near the outer periphery of the growth vessel 50 at the location where the reservoir 6 is disposed. Similarly to the conventional apparatus, the growth vessel 50 is arranged in the pressure vessel 8 as shown in FIG. 2, and the space in the growth vessel 50 is independent in the pressure vessel 8, and the growth vessel 50 has an internal pressure. An inert gas to be balanced is supplied into the pressure vessel 8 so that the growth vessel 50 is not damaged by the internal pressure.
[0029]
In the crucible for crystal growth and the crystal growth apparatus according to the present invention, a circular partition plate is arranged above the liquid surface of the raw material melt in the crucible main body, and the space above the crucible main body and the raw material melt Since the space between the upper surface of the raw material melt and the upper surface is partitioned, temperature fluctuations in the upper portion of the raw material melt due to high-temperature gas convection above the raw material melt in the crucible body are suppressed. Therefore, the temperature of the upper surface of the raw material melt is kept higher than the temperature of the solid-liquid interface even at the end of the crystal growth process in which the temperature difference between the solid-liquid interface and the upper surface of the raw material melt becomes smaller in the vertical Bridgman method or the vertical temperature gradient solidification method. Therefore, there is an advantage that abnormal growth from the upper surface of the raw material melt toward the solid-liquid interface side can be suppressed.
[0030]
【Example】
Next, the present invention will be described more specifically with reference to examples.
[0031]
The crystal growth apparatus according to this example is used for manufacturing a GaP single crystal and has the same structure as the apparatus shown in FIG.
[0032]
First, the crucible body 11 of the crystal growth crucible 1 is made of P-BN (pyrolytic boron nitride), and the lower end of the cylindrical portion (that is, the shoulder portion where the gradient of the inner wall surface shown by 100 in FIG. 1A suddenly increases). The inner diameter of the upper end is set to 51.0 mm, and the gradient angle of the inner wall surface above the lower end of the cylindrical portion is set to 2 degrees.
[0033]
Similarly to the crucible body 11, the partition plate 12 of the crystal growing crucible 1 is formed of a circular plate having an outer diameter of 56.0 mm, which is formed of P-BN, and has five inner diameters of 2 mm at the center. A vent hole 13 is provided.
[0034]
When 820 g of raw material (GaP polycrystal) is charged into the crystal growing crucible 1, a substantially cylindrical GaP single crystal having a length of 80 mm is obtained, and the engagement position of the partition plate 12 in the crucible body 11 is as follows. And 6 mm above the raw material melt 2 ′.
[0035]
Next, as the growth vessel 50, a graphite semi-shielded vessel provided with a leak hole 51 as shown in FIG. 2 was applied. In addition, the high temperature part for growing the crystal of the growth vessel 50 and the low temperature part for controlling the vapor pressure are arranged by arranging four cylindrical heaters 71, 71, 71, 72 having the same diameter in a coaxial manner. Heated with an equal heater.
[0036]
The control temperatures of the three heaters 71, 71, 71 in the high temperature part are set to 1480 ° C., 1475 ° C., and 1420 ° C. in this order from the top, and the temperature at the upper end position of the seed crystal 3 is set to the melting point (1465 ° C.). The temperature distribution was set, and the temperature distribution was high above the high temperature part and low below. Further, the temperature gradient was 20 ° C./cm at the seed crystal accommodation site and 5 to 10 ° C./cm in the crucible body 11 thereabove. Further, the heater control temperature at the bottom of the reservoir 6 in the low temperature portion was set to 595 ° C., and the temperature in the reservoir 6 was set to 578 ° C.
[0037]
Also, set each partial pressure of phosphorus vapor and Ar gas in the growth vessel 50 (inert gas) to ^{35kg / cm 2, 10kg / cm} 2, also, Ar gas pressure in the pressure vessel 8 (growth vessel external pressure) Was set to 45 kg / cm ² .
[0038]
And, as described above, a GaP single crystal having a substantially cylindrical shape and a length of 80 mm can be produced at a high yield from 820 g of raw material by the crystal growth apparatus according to the embodiment in which the crystal growth crucible 1 is incorporated. It was.
[0039]
【The invention's effect】
According to the crucible for crystal growth according to any one of claims 1 to 3, a circular partition plate is disposed above the liquid surface of the raw material melt in the crucible main body, and the space above the crucible main body and the raw material melt Since the space between the upper surface of the raw material melt and the upper surface is partitioned, temperature fluctuations in the upper portion of the raw material melt due to high-temperature gas convection above the raw material melt in the crucible body are suppressed.
[0040]
Therefore, in the vertical Bridgman method or the vertical temperature gradient solidification method, the temperature of the upper surface of the raw material melt is kept higher than the temperature of the solid-liquid interface even in the final stage of the crystal growth process where the temperature difference between the solid-liquid interface and the upper surface of the raw material melt becomes small. This makes it possible to suppress abnormal growth from the upper surface of the raw material melt toward the solid-liquid interface.
[0041]
In addition, since the partition plate has a vent hole through which the vapor of the component element having a high dissociation pressure passes, the vapor of the component element having a high dissociation pressure is applied to the raw material melt surface in the crucible body as in the conventional case. It is possible to grow crystals while doing so.
[0042]
On the other hand, according to the crystal growth apparatus according to the invention of claim 4, since the crucible for crystal growth according to any one of claims 1 to 3 is incorporated, in the vertical Bridgman method or the vertical temperature gradient solidification method Prevents the phenomenon that the temperature of the upper surface of the raw material melt is lower than the temperature of the solid-liquid interface, suppresses abnormal growth, and allows normal growth upward from the seed crystal to proceed stably. It has the effect of growing crystals.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views of a crystal growth crucible showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a crystal growth apparatus showing an embodiment of the present invention.
FIG. 3 is a cross-sectional view of a crystal growth apparatus according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crystal growth crucible 2 Raw material 2 'Raw material melt 3 Seed crystal 10 Seed crystal accommodating part 11 Crucible body 12 Partition plate 13 Vent

Claims (4)

It is arranged on the upper side in a vertical growth vessel arranged substantially vertically, and the raw material and seed crystal of the compound crystal are accommodated with the seed crystal on the lower side, and the raw material is heated to the melt surface. On the other hand, a vertical Bridgman method in which a compound crystal is sequentially grown from the seed crystal housing position upward while applying a vapor of a component element having a high dissociation pressure of the compound crystal supplied from the lower side in the growth vessel, or In the crucible for crystal growth applied to the vertical temperature gradient solidification method,
A substantially cylindrical crucible body having a seed crystal accommodating part on the bottom side and having an inner diameter that continuously increases from the lower side toward the upper side, and an outer peripheral edge of the crucible body on the inner peripheral wall surface. And a circular partition plate having a vent hole through which the vapor of the component element having a high dissociation pressure passes, and the locking position of the partition plate is set above the liquid surface of the raw material melt. A crucible for crystal growth characterized by The crucible for crystal growth according to claim 1, wherein a plurality of air holes having an inner diameter of 2 mm or less are provided in a central portion of the partition plate. The crucible for crystal growth according to claim 1, wherein a single air hole whose inner diameter is equal to or less than a radius of the partition plate is provided at a central portion of the partition plate. A vertical growth vessel arranged substantially vertically, a crystal growth crucible arranged above the growth vessel and containing a raw material and a seed crystal of the compound crystal with the seed crystal on the lower side, and the growth vessel And a vapor supply unit for containing a component element having a high dissociation pressure of the compound crystal and supplying a vapor of the component element to the raw material melt surface in the crucible for crystal growth. In a crystal growth apparatus for growing the compound crystal by the Bridgeman method or the vertical temperature gradient solidification method,
A crystal growth apparatus, wherein the crystal growth crucible is constituted by the crystal growth crucible according to any one of claims 1 to 3.

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