JP2006327879A - Method for manufacturing compound semiconductor single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to reduce the defect by the contact of a solid-liquid interface with the basilar part of a crucible by that the radiant heat from a raw material melt is intercepted by a heat insulating material and the convex degree of a convex shape of a solid-liquid interface is balanced in the manufacturing method of a compound semiconductor single crystal by a LEC method. <P>SOLUTION: The radiant heat from a crucible 7 to a base section 9a of a susceptor 9 is intercepted by a heat insulating material 10 disposed inside the base section 9a of the susceptor 9, thereby the solid-liquid interface 12 of a compound semiconductor single crystal and a raw material melt is maintained in a convex shape at the side of the raw material melt and the convex shape of the solid-liquid interface 12 is balanced so that the solid-liquid interface 12 may not come into contact with the basilar part of the crucible 7 while growing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a compound semiconductor single crystal by the LEC method (Liquid Encapsulated Czochralski method), and more particularly, the convex shape of the solid-liquid interface so that the solid-liquid interface does not contact the bottom of the crucible during growth. It relates to balancing technology.

  Compound semiconductors have been widely used in high-speed integrated circuits, opto-electronic integrated circuits, and other electronic devices due to the high quality of single crystals. Among them, the III-V compound semiconductor gallium arsenide (GaAs) has a feature that the electron mobility is faster than that of silicon and a wafer having a specific resistance of 10 7 Ω · cm or more can be easily manufactured. At present, the GaAs single crystal is mainly manufactured by the liquid sealing pulling method (LEC method).

  A method for producing a GaAs single crystal by the LEC method will be described with reference to FIG.

  A GaAs single crystal manufacturing apparatus by the LEC method shown in FIG. 3 includes a chamber 11 that is a pressure vessel, a pulling shaft 1 for pulling up the crystal, and a PBN (Pyrolytic Boron Nitride) that is a container that contains a compound semiconductor material. The structure has a crucible 7 made of boron nitride, a susceptor 9 for receiving the crucible 7, and a crucible shaft 8.

  The susceptor 9 that receives the crucible 7 is formed in a bottomed and uncovered cylindrical shape (cup shape) similar to the crucible 7, and the crucible 7 is accommodated in the susceptor 9. The susceptor 9 is fixed to the upper end of the vertical crucible shaft 8. The lower end of the crucible shaft 8 is connected to rotation / lifting means (not shown) provided outside the chamber 11, so that the susceptor 9 and the crucible 7 can rotate and move up and down around the crucible shaft 8. ing. In the chamber 11, a cylindrical carbon heater 5 is disposed around the susceptor 9. Cylindrical heat shield members 13 and 14 are disposed between the heater 5 and the side wall of the chamber 11, and a disk-shaped heat shield member 15 is disposed between the susceptor 9 and the bottom plate of the chamber 11. . On the upper side of the crucible 7 in the chamber 11, a pull-up shaft 1 is provided coaxially with the crucible shaft 8. The pull-up shaft 1 can be rotated and moved up and down by rotation / lifting means (not shown) provided on the outside upper side of the chamber 11. A seed crystal 2 is attached to the lower end of the pull-up shaft 1 by a holder.

  Regarding the crystal manufacturing method, first, Ga and As and boron trioxide 4 which is a liquid sealant are put in a crucible 7 which is a raw material container, and this is set in a chamber 11. A seed crystal 2 having a target orientation is attached to the tip of the pulling shaft 1.

  After setting the raw material in the chamber 11, the inside of the chamber 11 is evacuated and filled with an inert gas. Thereafter, the heater 5 installed in the chamber 11 is energized to raise the temperature in the chamber 11, and Ga and As are synthesized to produce a GaAs polycrystal. Thereafter, the temperature is further raised to melt GaAs to obtain a GaAs melt (raw material melt) 6.

  Subsequently, the pull-up shaft 1 and the crucible shaft 8 are relatively rotated. In this state, the pulling shaft 1 is lowered until the seed crystal 2 attached to the tip of the pulling shaft 1 comes into contact with the GaAs melt 6. Thereafter, the seed crystal 2 is slowly pulled up while rotating to grow a GaAs single crystal 3.

  During the growth of the GaAs single crystal, the outer diameter control is performed to keep the outer diameter of the GaAs single crystal constant. Further, the crucible shaft 8 is raised by the amount corresponding to the decrease in the liquid level of the GaAs melt 6 due to the growth of the GaAs single crystal so that the liquid level of the GaAs melt is always at a fixed position.

  In the manufacture of GaAs single crystals, as the solid-liquid interface becomes concave, the crystal lattice shifts during the growth of the GaAs single crystal, and polycrystallization is promoted. Therefore, the solid-liquid interface is made convex on the melt side. It is necessary to grow a GaAs single crystal.

Conventionally, in a method for producing a GaAs single crystal using a PBN crucible having a diameter of 15.24 cm (6 inches), when the temperature of the GaAs melt is high, the solid-liquid interface shape becomes concave with respect to the melt. From the standpoint that polycrystals are generated, the temperature of the GaAs melt (that is, the temperature at the bottom of the crucible) should be within a certain temperature range in consideration of the overlapping length of the upper and lower slits of the heater and the melt depth in the crucible. It is known to control the amount of heat generated by the heater so that the shape of the solid-liquid interface is convex with respect to the melt (see, for example, Patent Document 1).
Japanese Patent Publication No. 6-88873

  However, in the case of a single crystal having a large diameter of 100 mm or more to be grown, the solid-liquid interface may become convex, and the solid-liquid interface may come into contact with the crucible bottom. Patent Document 1 does not mention any inconvenience when the convexity of the solid-liquid interface progresses in this way.

  That is, in the case of producing a single crystal having a large diameter of 100 mm or more, the importance of the solid-liquid interface is naturally increased as compared with the single crystal having a small diameter, and a convex surface is required on the raw material melt side. When the known example in FIG. 3 is applied, the solid-liquid interface becomes convex, that is, the degree of convexity increases, and there is a problem that the phenomenon (defect) that the solid-liquid interface contacts the crucible bottom during growth frequently occurs. .

  Accordingly, an object of the present invention is to solve the above-mentioned problems and to block the radiant heat from the raw material melt with a heat insulating material in the method for producing a compound semiconductor single crystal by the LEC method, thereby increasing the convexity of the convex shape of the solid-liquid interface. It is an object of the present invention to provide a method for producing a compound semiconductor single crystal capable of reducing the defects caused by contact between the solid-liquid interface and the crucible bottom.

  In order to achieve the above object, the present invention is configured as follows.

  In the method for producing a compound semiconductor single crystal according to the first aspect of the present invention, a crucible is placed on a susceptor, accommodated in a pressure-resistant container filled with an inert gas, heated, and the raw material melted in the heated crucible. A method for producing a compound semiconductor single crystal by the LEC method, in which a liquid and a liquid sealant are accommodated, and the seed crystal is brought into contact with the raw material melt while the seed crystal and the crucible are moved relatively to grow the compound semiconductor single crystal The solid-liquid interface between the compound semiconductor single crystal and the raw material melt is convex on the raw material melt side by blocking the radiant heat from the crucible to the base portion of the susceptor with a heat insulating material provided inside the base portion of the susceptor. It is characterized by maintaining its shape and preventing its solid-liquid interface from touching the bottom of the crucible during growth.

  According to this feature, the convex shape of the solid-liquid interface is balanced, the convexity of the solid-liquid interface is properly maintained, and the incidence of the event that the solid-liquid interface contacts the bottom of the crucible during growth is drastically reduced. be able to.

  It is sufficient that the heat insulating material is provided inside the base portion of the susceptor. However, depending on the circumstances, the bottomed and uncovered cylindrical (cup-shaped) susceptor includes not only the inside of the base portion but also the peripheral wall. It can also be partially provided inside the part. That is, a heat insulating material can be provided also in a lower region (a region continuing upward from the periphery of the base portion) in the vertical region of the peripheral wall portion. When the heat insulating material is provided in the lower region of the peripheral wall as described above, when the raw material melt decreases and the crucible and the susceptor rise, the lower part of the crucible and the susceptor is excessively heated by the heater, and the balance of the heat flow is lost. The occurrence of such an inconvenient situation can be alleviated.

  According to a second aspect of the present invention, there is provided a method for producing a compound semiconductor single crystal according to the first aspect, wherein the susceptor comprises a base portion in contact with the bottom surface of the crucible and a bottomed, uncovered cylindrical shape comprising a peripheral wall portion in contact with the peripheral surface of the crucible. In addition, the heat insulating material is provided on the inner side only in the base portion, and radiant heat from the crucible to the base portion of the susceptor is blocked.

  According to this feature, the convexity of the solid-liquid interface is properly maintained while being a relatively simple means of providing the heat insulating material only on the base portion (bottom portion) of the bottomed and uncovered cylindrical susceptor. It is possible to easily balance the convex shape of the solid-liquid interface.

  A third aspect of the present invention is the method for producing a compound semiconductor single crystal according to the second aspect, wherein the size and shape of the heat insulating material of the base portion of the susceptor as viewed in plan are the size and shape of the bottom surface of the crucible. It is characterized by being almost identical.

  This feature minimizes the incidence of events where the solid-liquid interface contacts the bottom of the crucible during growth. The third aspect includes a mode in which the diameter d of the heat insulating material of the base portion of the susceptor is substantially the same as the diameter D of the crucible.

<Key points of the invention>
One of the problems in growing a GaAs single crystal is polycrystallization of crystals due to dislocation aggregation. Dislocations have the property of propagating perpendicularly to the solid-liquid interface, which is the boundary surface between the GaAs single crystal and the melt. If the solid-liquid interface has a concave shape on the melt side, a set of dislocations occurs. Therefore, in order to prevent dislocation aggregation, the shape of the solid-liquid interface is controlled so that it always protrudes toward the melt during the growth of the GaAs single crystal.

  However, in the case of producing a single crystal having a large diameter of 100 mm or more, the solid-liquid interface may become too convex. That is, when the known example of FIG. 3 is applied, the degree of convexity of the solid-liquid interface increases, and an event (defect) that the solid-liquid interface contacts the crucible bottom during growth frequently occurs.

  As a result of intensive studies by the present inventors, the cause is that in the pulling method shown in FIG. 3, the radiant heat from the GaAs melt escapes through the PBN crucible to the base portion of the graphite susceptor. It was found that it was difficult to balance the convex surface of the solid-liquid interface so that the liquid interface did not contact the crucible bottom.

  Therefore, in the present invention, in the method for producing a compound semiconductor single crystal by the LEC method, the radiant heat from the GaAs melt is shielded by a heat insulating material to balance the convex shape of the solid-liquid interface, that is, the convexity of the solid-liquid interface. It is easy to maintain the degree appropriately, and defects due to contact between the solid-liquid interface and the crucible bottom are reduced.

  According to the present invention, the radiant heat from the crucible to the base portion of the susceptor is blocked by the heat insulating material provided inside the base portion of the susceptor, so that the solid-liquid interface between the compound semiconductor single crystal and the raw material melt is formed as a raw material. While maintaining the convex shape on the melt side, it becomes easy to balance the convex shape of the solid-liquid interface, that is, maintain the convexity of the solid-liquid interface properly, and the solid-liquid interface is growing. The incidence of events that touch the bottom of the crucible can be drastically reduced.

  Therefore, as an effect of the present invention, an ideal solid-liquid interface shape can be formed, and a high-quality single crystal can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In this embodiment, a raw material of a compound semiconductor placed together with a sealant in a PBN crucible is heated to bring the seed crystal into contact with the melt of the compound semiconductor covered with the liquid sealant. In a method of manufacturing a compound semiconductor single crystal by growing a single crystal of a compound semiconductor by pulling up, radiation heat from a PBN crucible to a base of a graphite susceptor is shielded by a heat insulating material, so that a solid-liquid interface is PBN. This prevents the inconvenience of contact with the bottom of the crucible made of metal and pulls up a good quality single crystal.

  FIG. 1 shows a configuration of a compound semiconductor single crystal manufacturing apparatus according to an embodiment of the present invention.

  This compound semiconductor single crystal manufacturing apparatus has a cylindrical chamber 11 as in the case of the conventional apparatus of FIG. 3, and a PBN crucible 7 serving as a raw material container in the chamber 11, A graphite susceptor 9 for receiving the crucible 7 is provided, and the susceptor 9 is fixed to the upper end of the vertical crucible shaft 8. The lower end of the crucible shaft 8 is connected to rotation / lifting means (not shown) provided on the outside lower side of the chamber 11, so that the crucible 7 and the susceptor 9 can be rotated and raised / lowered about the crucible shaft 8. ing.

  In the chamber 11, a heater made of a coil portion for electromagnetic induction heating or a carbon heater 5 is disposed around the susceptor 9. Cylindrical heat shield members 13 and 14 are disposed between the heater 5 and the side wall of the chamber 11, and a disk-shaped heat shield member 15 is disposed between the susceptor 9 and the bottom plate of the chamber 11. . On the upper side of the crucible 7 in the chamber 11, a pull-up shaft 1 is provided coaxially with the crucible shaft 8. The pull-up shaft 1 can be rotated and moved up and down by rotation / lifting means (not shown) provided on the outside upper side of the chamber 11. A seed crystal 2 is attached to the lower end of the pull-up shaft 1 by a holder.

  In FIG. 1, the susceptor 9 that supports the crucible 7 is formed in a bottomed and uncovered cylindrical shape (cup shape) similar to the crucible 7, and the crucible 7 is accommodated in the susceptor 9. That is, the susceptor 9 has a bottomed and uncovered cylindrical shape (cup shape) composed of a base portion (bottom surface portion) 9a that contacts the bottom surface of the crucible 7 and a peripheral wall portion 9b that stands on the outer peripheral edge and contacts the peripheral wall of the crucible 7. ).

  The crucible 7 contains a GaAs melt 6 that is a raw material melt for growing a compound semiconductor, and boron trioxide 4 that is a liquid sealing agent (sealing agent melt) that covers the upper surface of the GaAs melt 6. Is done. The GaAs melt 6 and boron trioxide 4 are formed by containing a polycrystalline raw material and a sealing agent in a crucible 7 and melting them by heating. For this purpose, a heater composed of a coil portion for electromagnetic induction heating or a carbon heater 5 is provided on the outer periphery of the crucible 7. The crucible 7 is rotated by the rotating shaft 8 connected to the center of the bottom of the crucible 7, and the state of the polycrystalline raw material and the sealing agent in the crucible 7 is made uniform in the circumferential direction.

  The configuration of the above-described part is the same as the conventional one. However, in the manufacturing apparatus shown in FIG. 1, a heat insulating material 10 made of a material having excellent heat shielding characteristics, for example, graphite, is provided inside the base portion 9 a of the susceptor 9 according to the present invention. Thus, the radiant heat from the crucible 7 to the base portion 9a of the susceptor 9 is blocked. In other words, the susceptor 9, which is a holding jig for placing the PBN crucible 7, has a double structure comprising a graphite susceptor body (susceptor 9 in the figure) and a heat insulating material 10 installed inside the base portion 9a. It has become. In other words, the susceptor 9 is made of graphite, and the base portion 9a is thicker than the peripheral wall portion 9b.

  The size and shape of the heat insulating material 10 of the base portion 9 a of the susceptor 9 as viewed in plan are substantially the same as the size and shape of the bottom surface of the crucible 7. Here, the diameter d of the heat insulating material 10 on the base portion 9 a of the susceptor 9 is made substantially the same as the diameter D of the crucible 7. Further, the center of the crucible 7 and the center of the heat insulating material 10 are located on a concentric axis. These are for making the distribution of heat uniform in the bottom of the crucible of the GaAs melt 6.

  In this way, the heat insulating material 10 is provided inside the base portion 9a of the susceptor 9, and the radiant heat from the crucible 7 to the base portion 9a of the susceptor 9 is shielded by the heat insulating material 10, whereby the GaAs single crystal 3 and the GaAs melt ( Convex shape of the solid-liquid interface 12 is maintained so that the solid-liquid interface 12 of the raw material melt 6) is convex on the GaAs melt side and the solid-liquid interface 12 does not contact the bottom of the crucible 7 during growth. Can be balanced.

  This effect becomes remarkable when the diameter d of the heat insulating material 10 is substantially the same as the diameter D of the crucible 7, and the radiant heat from the GaAs melt 6 is uniformly blocked by the heat insulating material 10, and the convex shape of the solid-liquid interface 12 is obtained. Is easily balanced, and the appropriate convexity of the solid-liquid interface 12 is maintained. As a result, the solid-liquid interface 12 does not come into contact with the bottom of the crucible 7, and an ideal solid-liquid interface 12 for growing a single crystal can be formed. In addition, when the diameter d of the heat insulating material 10 is smaller than the diameter D of the crucible 7, the radiant heat flowing from the GaAs melt to the base portion 9 a of the susceptor 9 cannot be sufficiently blocked. Defects that come into contact with the bottom of the garment occur.

  Next, examples of the present invention will be described. Here, a GaAs single crystal 3 having a diameter of about 15.24 cm (6 inches) was prototyped by the LEC method using the compound semiconductor single crystal manufacturing apparatus having the configuration shown in FIG. In order to grow this GaAs single crystal having a diameter of about 15.24 cm (6 inches), the diameter D of the PBN crucible used was 350 mm.

  Crucible 7 was charged with 12,000 g of Ga as a raw material, 13,000 g of As, and 2,000 g of boron trioxide 4 as an As volatilization inhibitor. Further, the seed crystal 2 which is the base of the crystal was attached to the seed holder at the tip of the pulling shaft 1. The seed crystal 2 has a (100) plane in contact with the melted GaAs melt 6.

  After the crucible 7 is set in the chamber 11, the inside of the chamber 11 is evacuated and filled with an inert gas, and then the heater 5 is energized to raise the temperature in the chamber 11, thereby increasing Ga and As. Then, GaAs was synthesized, and the temperature was further raised to melt GaAs. Subsequently, the pull-up shaft 1 was rotated at 10 rpm, and the crucible shaft 8 was rotated at 20 rpm in the direction opposite to the pull-up shaft 1. In this state, the pulling shaft 1 is lowered until the seed crystal 2 comes into contact with the melted GaAs, and then the pulling shaft is raised at a speed of 10 mm / h while gradually lowering the set temperature of the heater 5. A GaAs single crystal 3 was grown.

  During the growth of the GaAs single crystal, the outer diameter control is performed to keep the outer diameter of the GaAs single crystal constant, and the crucible shaft 8 is raised by the amount that the liquid level of the GaAs melt 6 is reduced by the growth of the GaAs single crystal. Then, control was performed so that the liquid surface of the GaAs melt was always at a fixed position.

  In FIG. 2, when the diameter d of the heat insulating material 10 is changed from 50 mm to 350 mm with respect to the diameter D (D = 350 mm) of the crucible 7 in the above manufacturing method, the solid-liquid interface 12 contacts the bottom of the crucible 7. Indicates the occurrence rate (%) at which events occur. As can be seen from FIG. 2, as the diameter d of the heat insulating material 10 approaches the diameter D of the crucible 7, the incidence of events in which the solid-liquid interface 12 contacts the bottom of the crucible 7 decreases. And when the diameter d of the heat insulating material 10 becomes substantially the same as the diameter D of the crucible 7, it can be seen that the occurrence rate of the event that the solid-liquid interface 12 contacts the bottom of the crucible 7 becomes the lowest (almost zero). .

[Other embodiments]
In the above embodiment, the case where a GaAs single crystal is manufactured by the LEC method has been described as an example. However, the present invention can also be applied to a method for manufacturing a single crystal by the LEC method using a material other than GaAs. It is.

  In the said embodiment, although the heat insulating material 10 was provided only in the inner side of the base part 9a of the susceptor 9, as a form provided in part not only inside the base part 9a but inside the surrounding wall part 9b depending on circumstances. Also good. That is, the heat insulating material 10 can be provided also in the lower region (partial region continuing upward from the periphery of the base portion 9a) in the vertical region of the peripheral wall portion 9b. When the heat insulating material 10 is provided in the lower region of the peripheral wall portion 9b in this way, the raw material melt is reduced, and when the crucible 7 and the susceptor 9 are raised for position correction according to this, the crucible 7 and the susceptor 9 The disadvantage that the lower portion is excessively heated by the heater 5 and the balance of the heat flow is lost can be alleviated.

It is a conceptual diagram of the manufacturing apparatus which grows a gallium arsenide single crystal by the manufacturing method of the compound semiconductor single crystal of this invention. It is the figure which showed the relationship in which the incidence (%) which a solid-liquid interface contacts a crucible bottom part changes when the diameter d of a heat insulating material is changed with respect to the diameter D of a crucible. It is a conceptual diagram of the manufacturing apparatus which grows a gallium arsenide single crystal by the manufacturing method of the conventional compound semiconductor single crystal.

Explanation of symbols

1 Pull-up shaft 2 Seed crystal 3 GaAs single crystal 4 Boron trioxide 5 Heater 6 GaAs melt (raw material melt)
7 crucible 8 crucible shaft 9 susceptor 9a base (bottom)
9b peripheral wall part 10 heat insulating material 11 chamber 12 solid-liquid interface 13 heat shield member 14 heat shield member 15 heat shield member

Claims (3)

Place the crucible on the susceptor, place it in a pressure-resistant container filled with inert gas, heat it, store the raw material melt and the liquid sealant in the heated crucible, and seed the raw material melt. In the method of manufacturing a compound semiconductor single crystal by the LEC method in which the seed crystal and the crucible are relatively moved while being in contact with each other to grow a compound semiconductor single crystal,
By blocking the radiant heat from the crucible to the base part of the susceptor with a heat insulating material provided inside the base part of the susceptor, the solid-liquid interface between the compound semiconductor single crystal and the raw material melt has a convex shape on the raw material melt side. A method for producing a compound semiconductor single crystal, characterized by maintaining and preventing the solid-liquid interface from contacting the bottom of a crucible during growth. In the manufacturing method of the compound semiconductor single crystal of Claim 1,
The susceptor has a bottomed and uncovered cylindrical shape composed of a base portion in contact with the bottom surface of the crucible and a peripheral wall portion in contact with the peripheral surface of the crucible, and the heat insulating material is provided only inside the base portion to A method for producing a compound semiconductor single crystal, wherein radiant heat to a base portion is blocked. In the manufacturing method of the compound semiconductor single crystal of Claim 2,
A method for producing a compound semiconductor single crystal, wherein the size and shape of the heat insulating material of the base portion of the susceptor as viewed in plan are substantially the same as the size and shape of the bottom surface of the crucible.

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