JP2005097032A - Apparatus for growing semiconductor single crystal and heater for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for growing a semiconductor single crystal, which has a heater structure, enabling reduction of the quantity of radiation to the single crystal exposed in an inert gas without using a shielding body, and further enabling the heat insulation of the single crystal located in a liquid encapsulating agent from a raw material melt. <P>SOLUTION: In the apparatus, the quantity of radiation to the single crystal exposed in the inert gas is reduced by partitioning an area in the up-and-down direction of a heater 6 into an upper heater part 62 and a lower heater part 61 across a part corresponding to the surface of the liquid encapsulating agent 2, and then making the heater cross sectional area of the upper heater part 62 larger than that of the lower heater part 61 so as to partially suppress the calorific value. Further, the side face of the single crystal 1 located in the liquid encapsulating agent is kept warm by inclining the inside wall of the upper heater part 62 of the heater 6 so that the inside wall approaches to the liquid encapsulating agent 2 side toward upper side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a compound semiconductor single crystal growth apparatus and its heater.

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 these, gallium arsenide, which is a group III-V compound semiconductor, has a feature that 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 single crystal of GaAs is manufactured mainly by a liquid-encapsulated Czochralski method (hereinafter referred to as “LEC method”).

In this LEC method, as shown in FIG. 2, a PBN (pyrolytic boron nitride) container (crucible 5) containing a polycrystalline raw material is placed in a pressure resistant container 21 filled with an inert gas 8. Then, the PBN container 5 is heated to use the polycrystalline raw material as the raw material melt 3, and the seed crystal 4 and the PBN crucible 5 are moved relative to each other while the seed crystal 4 is in contact with the raw material melt 3. It is a way to grow. When a material having a very high dissociation pressure, such as As (arsenic), is used as a raw material, the surface of the raw material is stable even at high temperatures, and has characteristics such as a fluid that does not hinder the growth of a single crystal. Cover with a liquid sealant 2 made of ₂ O ₃ .

  A method for producing a GaAs single crystal will be specifically described.

  A GaAs single crystal manufacturing apparatus 20 of the LEC method shown in FIG. 2 includes a pressure vessel 21 as a furnace body portion, a pulling shaft 23 for pulling up the single crystal, a PBN crucible 5 as a raw material container, and the PBN. It has a structure having a crucible shaft 24 for receiving a crucible and a graphite heater 22 as a heating means installed around the crucible 5. Here, the heater 22 is designed to be longer than the crucible 5.

The preparation method of the GaAs single crystal by LEC method, in FIG. 2, the PBN crucible 5 which is a container of raw material, the Ga and As compound semiconductor material, boron trioxide is volatile prevention material of As (B ₂ O ₃ ) is put and set in the pressure vessel 21. Further, the seed crystal 4 that is the base of the single crystal is attached to the tip of the pulling shaft 23. After setting the raw materials, the high-pressure vessel 21 is evacuated and filled with an inert gas (vacuum / gas replacement).

  Thereafter, the heater 22 installed around the crucible 5 in the high-pressure vessel 21 is energized, the temperature in the high-pressure vessel 21 is raised, and Ga and As are synthesized and melted to obtain a GaAs melt 3. .

  Next, the PBN crucible 5 is moved so that the position of the uppermost surface of the GaAs melt 3 coincides with the center position of the heat generating portion of the heater 22.

  Next, while rotating the pulling shaft 23 and the crucible shaft so that the rotation directions are reversed, the pulling shaft 23 is lowered until the seed crystal 4 attached to the tip contacts the GaAs melt 3. Subsequently, by gradually lowering the temperature in the high-pressure vessel 21 by adjusting the output of the heater 22, the pull-up shaft 23 is raised at a constant speed, so that the seed crystal 4 (seeding part) gradually goes to the straight body part. Grow thick single crystals. When the target crystal diameter is reached, the GaAs single crystal 1 is manufactured while controlling the outer shape of the straight body portion in order to keep the diameter constant.

  By the way, when manufacturing a GaAs single crystal by the above LEC method, it is preferable to prevent the crystal from being polycrystallized and make the single crystal portion as long as possible. If the single crystal portion is long, more wafers can be sliced from one material, the preparation time and the number of preparations of the pulling furnace can be reduced, and the number of characterizations can be reduced. Moreover, the ratio with respect to the cost of the consumables (crucible, liquid sealing agent) used for raising can be lowered.

  There are mainly two causes of the above-mentioned polycrystallization. One is that the solid-liquid interface shape is uneven, and thermal stress is concentrated on that part, resulting in dislocations. The other is crystal Surface roughness of the crystal, that is, the crystal surface is heated to a high temperature due to radiant heat, and As (arsenic) is dissociated and left Ga (gallium) reaches the solid-liquid interface through the surface.

  In order to eliminate the former cause, attempts have been made to improve the amount of heat generated by the heater and the shape of the heater and hot zone. For example, in a silicon single crystal pulling furnace, paying attention to the relationship between the length of the vertical overlap of the upper and lower slits of the heater and the inner diameter of the heater, the silicon single crystal is grown under certain conditions (For example, see Patent Document 1).

As a solution to the latter cause, attempts have been made to provide a cylinder or plate around the single crystal to block radiant heat, or to blow a gas onto the cylinder, plate or single crystal. For example, in Japanese Patent Laid-Open No. 9-52790 (Patent Document 2), as shown in FIG. 4, a shield 30 is provided between the inner surface of the crucible 5 and the side surface of the grown single crystal 1. The single crystal 1 is surrounded so as to block radiant heat from the crucible 5 toward the single crystal 1, and the high temperature gas is allowed to escape upward from the vent hole 32.
JP 11-116390 A JP-A-9-52790

  However, the conventional techniques have the following problems.

  As described above, the conventional heater 22 retains the single crystal side surface in the liquid sealant from the raw material melt for the purpose of suppressing the heating of the raw material melt in the crucible 5 and the heat dissipation from the single crystal side surface. Therefore, it is designed longer than the crucible 5. Therefore, as shown in FIG. 3, the portion of the grown single crystal 1 exposed from the liquid sealant 2 in the inert gas 8 is heated by the heat radiation 7 from the heater 22, and As (arsenic) from the crystal. ) 9 is dissociated, whereby Ga (gallium) 10 is melted and polycrystal 11 is formed, which is a starting point for polycrystallization.

  On the other hand, in Patent Document 1, as a partition for reducing the amount of heat radiation 7 to the exposed portion of the single crystal 1, a measure is taken to provide a shield 30 between the single crystal and the heater as shown in FIG. However, there is a limit to the effect of shielding heat radiation from the heater by such a shield, and a complete shielding effect cannot be obtained.

  Therefore, the object of the present invention is to solve the above problems, reduce the amount of heat radiation to the single crystal exposed in the inert gas without using a shield, and further from the raw material melt into the liquid sealant. It is an object of the present invention to provide a semiconductor single crystal growth apparatus having a heater structure capable of keeping a single crystal positioned and a heater thereof.

  In order to achieve the above object, the present invention is configured as follows to reduce the amount of heat radiation to a single crystal exposed in an inert gas.

  A semiconductor single crystal growth apparatus according to the invention of claim 1 includes a crucible containing a polycrystalline raw material and a liquid sealant, a pressure vessel containing the crucible and filled with an inert gas, a polycrystalline raw material in the crucible, In order to heat the liquid sealant into a melt, a cylindrical graphite heater provided on the outer periphery of the crucible so as to surround the crucible, and a seed crystal brought into contact with the raw material melt are supported, and the raw material melt In the semiconductor single crystal growth apparatus having a pull-up axis for pulling up the single crystal grown from the upper and lower regions of the heater, the region corresponding to an arbitrary position from the surface of the liquid sealant to the upper end surface of the crucible is defined as a boundary. The upper heater part is divided into the lower heater part, the heater cross-sectional area of the upper heater part is made larger than that of the lower heater part, and the heat to the single crystal exposed in the inert gas is suppressed by partially suppressing the heat generation amount. Reduce the amount of radiation Characterized in that was.

  Here, a large sectional area of the upper heater portion of the heater means that the heat generation resistance in this portion is small. Accordingly, for example, by making the cross-sectional area of a portion (upper heater portion) located above the surface of the liquid sealant in the heater larger than the lower portion (lower heater portion), Heat generation at the exposed portion (heater exposed portion) protruding above the upper end surface of the crucible can be suppressed, and the amount of heat radiation that the heater per unit length has on the single crystal can be reduced.

  The semiconductor single crystal growth apparatus used in the present invention is not limited, but is particularly suitable as a compound semiconductor manufacturing apparatus such as a GaAs compound single crystal.

  According to a second aspect of the present invention, in the semiconductor single crystal growth apparatus according to the first aspect, the inner wall of the upper heater portion of the heater is inclined so as to approach the liquid sealant side as it goes upward.

  Thus, by tilting the surface of the upper heater part (heater part for heating the exposed part) toward the liquid sealant, the heat per unit length of the heat given to the single crystal exposed in the inert gas by the heater The amount of radiation can also be reduced as compared with the prior art. Moreover, since the heater shape of the upper heater portion is inclined toward the liquid sealant, it is possible to keep the side surfaces of the single crystal located in the liquid sealant from the raw material melt.

  According to a third aspect of the present invention, in the semiconductor single crystal growth apparatus according to the first or second aspect of the present invention, the boundary of dividing the vertical region of the heater into an upper heater portion and a lower heater portion is the position of the surface of the liquid sealant It is characterized in that it is determined at a location corresponding to.

  By setting in this way, the conditions for the heating of the raw material melt and the heat retention of the single crystal side surface in the raw material melt from the liquid sealant are not changed significantly from the conventional one, and the single unit exposed in the inert gas is not changed. The amount of heat radiation to the crystal can be reduced as compared with the prior art, thereby suppressing polycrystallization due to As dissociation.

  A heater for a semiconductor single crystal growth apparatus according to a fourth aspect of the present invention is a cylinder provided around the crucible on the outer periphery of the crucible so as to heat the polycrystalline raw material and the liquid sealant in the crucible into a melt. In a heater for a semiconductor single crystal growth apparatus designed to be longer than the crucible in the vertical length of the graphite heater, when installed around the crucible, liquid in the vertical area of the heater The heater cross-sectional area of the upper heater part located above the surface of the sealant is made larger than that of the lower heater part located below it, and the inner wall of this upper heater part is liquid sealed toward the upper side. It is characterized by having a shape inclined so as to approach the agent side.

  Thus, by increasing the cross-sectional area of the heater (upper heater part) located above the liquid sealant surface, the heater heat generation in the upper heater part is suppressed, and the heater per unit length Can reduce the amount of heat radiation that affects the single crystal. In addition, by tilting the surface of the upper heater portion toward the liquid sealant, the side surface of the single crystal located in the liquid sealant from the raw material melt can be kept warm.

  As described above, according to the present invention, the following excellent effects can be obtained.

  According to the invention of claim 1, the vertical region of the heater is divided into an upper heater portion and a lower heater portion with a location corresponding to an arbitrary position from the surface of the liquid sealant to the upper end surface of the crucible as a boundary, Since the heater cross-sectional area of the upper heater part is made larger than that of the lower heater part, the amount of heat generated is partially suppressed, and the amount of heat radiation to the single crystal exposed in the inert gas is reduced. For example, it is possible to prevent dissociation of As and the resulting polycrystallization due to the flow of Ga, and the amount of heat radiation is reduced, so that the cooling effect on the single crystal part is promoted, and the crystal growth interface is used as a raw material. Since it can be improved so as to have a convex shape on the melt side, a high-quality single crystal with less dislocation accumulation can be produced.

  According to the invention of claim 2, since the inner wall of the upper heater portion is inclined toward the liquid sealant side, the amount of radiation given to the single crystal exposed by the heater per unit length in the inert gas is reduced. It can be reduced as compared with the prior art, and the effect of keeping the side surface of the single crystal located in the liquid sealant from the raw material melt can be obtained.

  According to the invention of claim 3, since the boundary for dividing the vertical region of the heater into the upper heater portion and the lower heater portion is determined at a position corresponding to the position of the surface of the liquid sealant, The amount of heat radiation from the liquid sealant to the single crystal exposed in the inert gas is reduced compared to the conventional one, without significantly changing the conditions for heat retention from the liquid sealant to the side surface of the single crystal in the raw material melt. Thus, for example, polycrystallization caused by dissociation of As can be suppressed.

  A heater for a semiconductor single crystal growth apparatus according to a fourth aspect of the present invention has a heater cross-sectional area of an upper heater portion located above the surface of the liquid sealant in a region in the vertical direction of the heater. Is larger than the lower heater part located at the top, and the inner wall of the upper heater part is inclined so as to approach the liquid sealant side as it is on the upper side. The amount of heat radiation that the heater per unit length has on the single crystal can be reduced, and the side surface of the single crystal located in the liquid sealant can be kept warm from the raw material melt. .

In short, as an effect of the present invention, by reducing the amount of heat radiation to a single crystal exposed in an inert gas, for example, for producing a GaAs single crystal,
(1) It is possible to prevent dissociation of As from the single crystal and polycrystallization due to the accompanying Ga flow-out,
(2) The amount of heat radiation is reduced, the cooling effect on the crystal part is promoted, the crystal growth interface is improved to a convex shape on the melt side, and a high-quality single crystal with less dislocation accumulation can be manufactured. .

  Hereinafter, the present invention will be described based on the illustrated embodiments.

  The LEC GaAs single crystal manufacturing apparatus shown in FIG. 1 is the same as that described above with reference to FIGS. 2 and 3 except for the shape of the heater. That is, this GaAs single crystal manufacturing apparatus is made of a PBN crucible 5 which is a raw material container containing Ga and As (polycrystalline raw material) as compound semiconductor raw materials and boron trioxide (liquid sealant) as a volatilization preventive material for As. A pressure vessel 21 which is a furnace body portion containing the crucible 5 and filled with the inert gas 8, a crucible shaft 24 for receiving the PBN crucible 5 in the pressure vessel 21, and a polycrystalline raw material in the crucible 5 In order to heat the liquid sealant and make it into a melt, a graphite heater 6 as a heating means installed around the crucible 5 and a seed crystal 4 brought into contact with the raw material melt 3 are supported. The structure has a pulling shaft 23 for pulling up the single crystal 1 grown from the raw material melt 3. Here, the heater 6 is designed to be longer than the crucible 5 like the conventional heater 22.

  The heater 6 has a cylindrical shape as a whole (including a case of a substantially cylindrical shape), and a heater portion (lower heater portion) 61 positioned below the surface of the liquid sealant 2 is used as a boundary. The heater part (upper heater part) 62 located in the upper part is comprised.

  As can be seen from FIG. 1, in the heater 6, the thickness of the lower heater portion 61 of the heater 6 does not change in the vertical direction and is the same thickness in the vertical direction. The thickness of the heater portion 62 becomes thicker toward the upper portion, and the heater cross-sectional area becomes larger. In the case of this embodiment, for the upper heater portion 62 above the surface of the liquid sealing agent 2, the inner wall surface 62 a gradually approaches the inner side from the height position corresponding to the surface of the liquid sealing agent 2. The overhanging wall is inclined toward the liquid sealant side so as to approach the side of the liquid sealant 2 and the single crystal 1 during the growth of the single crystal. The outer wall of the upper heater portion 62 is the same vertical wall as the lower heater portion 61.

  The lower heater portion 61 on the side of the raw material melt 3 has the same cross section as that of the conventional heater, so that the heating of the raw material melt 3 is under the same conditions as the conventional heater 22. The heater shape of the upper heater portion 62 located above the liquid sealant 2 has a cross-sectional area larger than that of the lower heater portion 61. Therefore, the resistance per unit length of the heater is reduced, and FIG. As shown by the difference in thickness of the arrows, the amount of heat radiation 7a from above the liquid sealant 2 is reduced compared to the amount of heat radiation 7 on the raw material melt side.

  As a result, the heat radiation amount to the single crystal exposed in the inert gas can be reduced without significantly changing from the conventional conditions for the heating of the raw material melt and the heat retention of the crystal side surface in the raw material melt from the liquid sealant 2. This can be reduced as compared with the prior art, thereby suppressing polycrystallization due to As dissociation.

  Further, since the heater shape (inner wall surface 62a) of the upper heater portion 62 is inclined toward the liquid sealing agent 2, the heater 6 per unit length is exposed in the inert gas 1 The amount of heat radiation given to can also be reduced as compared with the prior art. Then, the side surface of the single crystal 1 located in the liquid sealant 2 from the raw material melt 3 can be kept warm by inclining the surface (inner wall surface 62a) of the upper heater portion 62 toward the liquid sealant 2 side. It becomes.

  That is, according to the above embodiment, the amount of heat radiation to the single crystal 1 exposed in the inert gas 8 is reduced, and the temperature of the single crystal 1 located in the liquid sealant 2 from the raw material melt 3 is maintained. It is possible to construct a heater structure that achieves both.

  In the above embodiment, the boundary between the lower heater portion 61 and the upper heater portion 62, that is, the starting end portion that increases the cross-sectional area of the heater 6 as the upper heater portion 62 is a location corresponding to the surface of the liquid sealant 2. The present invention is not limited to this, and is divided into a lower heater portion 61 and an upper heater portion 62 at a location corresponding to an arbitrary point from the surface of the liquid sealant 2 to the upper end portion of the crucible 5. Thus, the cross-sectional area of the heater 6 can be increased as the upper heater portion 62. For example, only the heater portion 63 extending upward from the upper end surface of the crucible 5 is inclined so that the cross-sectional area is increased more than the heater portion below it, and the inner wall 62a is located on the inner side toward the upper side. be able to.

It is the schematic which showed the shape and positional relationship of the single crystal manufacturing apparatus in this invention, and its heater. It is the schematic which showed the conventional single crystal manufacturing apparatus. It is the schematic which showed the conventional single crystal manufacturing apparatus, its heater shape, and positional relationship. It is the figure which showed the conventional single crystal manufacturing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single crystal 2 Liquid sealing agent 3 Raw material melt 4 Seed crystal 5 Crucible 6 Heater 8 Inert gas 10 Ga
11 Polycrystalline 21 Pressure vessel 23 Pulling shaft 24 Crucible shaft 61 Lower heater portion 62 Upper heater portion 62a Inner wall surface

Claims (4)

A crucible containing a polycrystalline raw material and a liquid sealing agent, a pressure vessel containing this crucible and filled with an inert gas, and heating the polycrystalline raw material and the liquid sealing agent in the crucible into a melt, A semiconductor having a cylindrical graphite heater provided on the outer periphery of a crucible so as to surround the crucible, and a pulling shaft for supporting a seed crystal brought into contact with the raw material melt and pulling up a single crystal grown from the raw material melt In single crystal growth equipment,
The vertical region of the heater is divided into an upper heater portion and a lower heater portion with a location corresponding to an arbitrary position from the surface of the liquid sealant to the upper end surface of the crucible as a boundary,
The semiconductor is characterized in that the heater sectional area of the upper heater part is made larger than that of the lower heater part, the amount of heat generated is partially suppressed, and the amount of heat radiation to the single crystal exposed in the inert gas is reduced. Single crystal growth equipment. The semiconductor single crystal growth apparatus according to claim 1.
An apparatus for growing a semiconductor single crystal, wherein the inner wall of the upper heater portion of the heater is inclined so as to approach the liquid sealant side as it goes upward. The semiconductor single crystal growth apparatus according to claim 1 or 2,
A semiconductor single crystal growth apparatus characterized in that a boundary for dividing a vertical region of the heater into an upper heater portion and a lower heater portion is set at a position corresponding to the position of the surface of the liquid sealant. A cylindrical graphite heater provided around the crucible on the outer periphery of the crucible to heat the polycrystalline raw material and liquid sealant in the crucible to form a melt, whose vertical length is longer than that of the crucible In the heater for the designed semiconductor single crystal growth equipment,
When installed around the crucible, the heater cross-sectional area of the upper heater part located above the surface of the liquid sealant in the vertical area of the heater is lower than the lower heater part located below it. The heater for a semiconductor single crystal growth apparatus is characterized in that the inner wall of the upper heater portion is inclined so as to approach the liquid sealant side as it goes upward.

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