JPH06102589B2 - Single crystal manufacturing method and manufacturing apparatus - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a technique for producing a single crystal, and in particular, a liquid sealing pulling method for pulling and producing a single crystal from a conductive raw material melt by applying a magnetic field. The present invention relates to a method and an apparatus for producing a single crystal.

[Technical background of the invention and its problems]

Conventionally, a single crystal substrate used in the semiconductor industry has been produced by cutting out an ingot produced from a raw material melt by a pulling method (CZ method). With the recent trend toward higher density and higher integration of semiconductor integrated circuits, there is a strong demand for higher uniformity of the semiconductor single crystal serving as the substrate.

However, II created by liquid encapsulation pulling method
Group IV compound single crystal substrates do not have sufficient uniformity to make high density integrated circuits. That is, in the liquid sealing pulling method, there is intense thermal convection in the raw material melt contained in the crucible, and the interface between the melt and the prepared crystal is extremely unstable. For this reason, the substrate cut out from the formed crystal has low uniformity, and thus it is difficult to produce a high-density integrated circuit using this substrate with high yield.

On the other hand, as a method for solving the above-mentioned problems, a method of applying a horizontal magnetic field to the raw material melt to suppress thermal convection of the raw material melt to produce a single crystal with good uniformity has recently attracted attention. However, with this method, the appropriate range of the applied magnetic field is narrow, and it is extremely difficult to effectively suppress thermal convection.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a highly uniform III-V group compound single crystal capable of effectively suppressing thermal convection in a raw material melt. Another object of the present invention is to provide a method for producing a single crystal, which enables easy production.

Another object of the present invention is to provide an apparatus for producing a single crystal for carrying out the above method.

[Outline of Invention]

The essence of the present invention is to apply a magnetic field in which thermal vibration is sufficiently small and a proper range of magnetic field application strength is sufficiently wide, based on the knowledge of thermal vibration characteristics with respect to magnetic field application.

That is, according to the present invention, a liquid capsule layer is formed on a raw material melt made of a III-V semiconductor contained in a crucible, a horizontal magnetic field is applied to the raw material melt, and the raw material melt is seeded. In a method for producing a single crystal by pulling the seed crystal vertically by bringing the crystals into contact with each other and pulling the seed crystal in a vertical direction, thermal vibration is large in the direction in which the magnetic field strength increases with respect to the thermal vibration characteristics accompanying changes in the magnetic field strength. The first region, the second region where the thermal vibration becomes small, the third region where the thermal vibration becomes large again.
When the region (4) and the fourth region in which the thermal vibration is reduced again are set, the strength of the magnetic field applied to the raw material melt is set to the magnitude of the above-mentioned fourth region.

The present invention also relates to a crucible containing a raw material melt composed of a III-V semiconductor and a liquid capsule layer formed thereon, a heater for heating the raw material melt in the crucible, and a horizontal member for the raw material melt. A magnet for applying a magnetic field in a direction, wherein a single crystal is pulled up to produce a single crystal by bringing a seed crystal into contact with the raw material melt and pulling the seed crystal to produce a raw material melt by applying the magnetic field. With respect to the thermal vibration characteristics of the
, The second region where the thermal vibration becomes small, the third region where the thermal vibration becomes large again, and the fourth region where the thermal vibration becomes small again, the magnitude of the exciting current of the magnet is set to The strength of the magnetic field applied to the liquid is set so as to be the above-mentioned fourth region.

〔The invention's effect〕

According to the present invention, since the III-V group compound single crystal can be pulled in a stable region in the raw material melt in which thermal vibration is small, it is possible to manufacture a high-quality single crystal with good uniformity. . In addition, unlike the method of pulling in the second region, since the appropriate range of the applied magnetic field is wide, the requirements for the stability of the magnetic field are not strict, and the single crystal can be easily manufactured.

Example of Invention

First, before describing the embodiments, the basic principle of the present invention will be described.

The inventors of the present invention have scrutinized the changes in thermal vibrations in the raw material melt with respect to the applied magnetic field strength, and have obtained the characteristics shown in FIG. Here, the horizontal axis represents time t, the vertical axis represents melt temperature [° C.], and ↑ represents approximate magnetic field strength [Oe]. Also, the thick line in the figure indicates the temperature of the central portion inside the crucible containing the raw material melt, and the thin line indicates the temperature of the peripheral portion. GaAs was used as the raw material melt. As shown in Fig. 2, the temperature is measured at the center of the crucible 21 and at 35 [m from the center.
m], the thermocouples 24 as temperature sensors
(24a, 24b) covered with a quartz tube 25 (25a, 25b) was inserted into the raw material melt 22 of the capsule layer 23.

As can be seen from the characteristics shown in FIG. 1, the thermal vibration is large in the region where the magnetic field strength is small, and becomes smaller as the magnetic field strength approaches 1200 [Oe]. The thermal vibration becomes minimum when the magnetic field strength is around 1200 [Oe], and the thermal vibration becomes large again when the magnetic field strength exceeds 1300 [Oe]. The characteristics up to this point are well known. Therefore, conventionally, crystal pulling was performed in the region of magnetic field strength around 1200 [Oe] where the thermal vibration is the smallest. When the inventors of the present invention further increased the magnetic field strength, the thermal vibration becomes small again when the magnetic field strength exceeds 3000 [Oe], and the thermal vibration becomes extremely small when the magnetic field strength exceeds 3500 [Oe]. It has been found. Then, it was found that even if the region where this thermal vibration is small reaches tens of thousands [Oe], it continues. Therefore, if the single crystal is pulled in this region, it is presumed that the single crystal can be manufactured with good uniformity.

Here, the temperature characteristics of the central portion of the raw material melt shown in FIG. 1 can be summarized with respect to thermal vibration, and can be expressed as schematically shown in FIG. This is divided into regions according to the magnitude of thermal vibration as follows. That is, 1150
The first region where the thermal vibration is large up to a magnetic field strength of about [Oe], the second region where the magnetic vibration is small about 1150 to 1250 [Oe], the magnetic field strength is about 1250 to 3000 [Oe] It is divided into a third region where the thermal vibration becomes large again and a fourth region where the thermal vibration exceeding the magnetic field strength of 3000 [Oe] becomes small again.

Here, it should be noted that although the thermal vibration is certainly small in the second region, its range is extremely narrow.
This means that when pulling a single crystal in the second region, it is highly dependent on the magnetic field strength and other growth conditions (crucible temperature, rotation speed, etc.) and lacks reproducibility. On the other hand, thermal vibration is small and the range is sufficiently wide in the fourth region. Therefore, when pulling the single crystal in the fourth region, it is possible to always manufacture the single crystal in a state in which thermal vibration is small, irrespective of some variation in magnetic field strength. In other words, the growth condition dependency is low, and improvement in reproducibility can be expected.

Although not shown in FIG. 1, the temperature difference between the central portion and the peripheral portion of the raw material melt tends to increase as the magnetic field strength reaches tens of thousands [Oe]. If this temperature difference becomes too large, the dislocation density of crystals will increase. According to the experiments conducted by the present inventors, it was possible to manufacture a single crystal within a range in which the dislocation density of the crystal was sufficiently small up to a magnetic field strength of about 10,000 [Oe]. The characteristics shown in FIG. 3 are Ga
This is the case of As, and if the growth conditions and the single crystal to be manufactured are different (especially, the electric conductivity of the raw material melt is different), the characteristics are also different. However, the first to fourth regions do not appear, and therefore, even if the manufactured III-V compound single crystal is changed, the single crystal may be pulled up in the fourth region at that time.

Hereinafter, one embodiment of the present invention will be manufactured with reference to the drawings. FIG. 4 is a sectional view showing a schematic structure of a single crystal manufacturing apparatus according to the same embodiment.

In the figure, 41 is a high-pressure container made of stainless steel or the like, and in this container 41, a crucible 42, a crucible receiver 43, a heater 44, a heat shield 45, etc. are housed, and a magnet 51 is provided outside the container 41. , 52 are provided. The crucible 42 is made of PBN, for example, and is formed in a bottomed cylindrical shape.
In the crucible 42, metal Ga and metal A, which are the base of the raw material melt 61,
s and, for example, B ₂ O _{3 serving as} a base of the liquid capsule layer 62 are contained. Then, the seed crystal 63 attached to the lower end of the crystal pulling shaft 46 penetrating the upper wall of the container 41 is brought into contact with the raw material melt 61, and then the pulling shaft 46 is pulled up to form GaAs.
The single crystal 64 is to be pulled up and manufactured.

The crucible 42 is supported by a crucible receiver 43. The crucible receiver 43 is configured by combining a cylindrical body 43a, a bottom plate 43b, and a pedestal 43c. That is, the cylindrical body 43a is disposed in close contact with the crucible 42 so as to surround the outer peripheral surface of the crucible 42, and the bottom plate 43a
The b is arranged so as to contact the bottom of the crucible 42. The pedestal 43c supports the bottom plate 43b.
Here, unlike the conventional carbon, the cylindrical body 43a, the bottom plate 43b, and the pedestal 43c that form the crucible receiver 43 are formed from a sintered compact of AlN (aluminum nitride). That is,
Y ₂ O ₃ as a binder is mixed with AlN green compact, and the mixture is sintered at a temperature of 1800 [° C] to form a cylindrical body.
43a, a bottom plate 43b and a pedestal 43c are formed.

A rotation shaft 47 that penetrates the bottom wall of the container 41 is attached to the pedestal 43c of the crucible receiver 43. Then, by rotating the rotating shaft 47 by a rotating mechanism (not shown), the crucible is
42 is supposed to rotate.

A cylindrical heater 44 made of carbon or the like is disposed coaxially with the crucible 42 on the outer peripheral portion of the crucible 42 so as to be separated from the crucible 42. The heater 44 heats and melts the raw material and the capsule material in the crucible 42 to form the raw material melt 61 and the liquid capsule layer 62 thereon. Also, the heater 44
A heat shield 45 is arranged outside the. The heat shield 45 is composed of a side ring 45a, a top plate 45b and a bottom plate 45c. The side ring 45a is formed in a cylindrical shape having a diameter and height larger than that of the heater 44, and is arranged coaxially with the heater 44. The top plate 45b is formed in a disc shape having an opening at the center thereof through which the crucible 42 is inserted, and is arranged above the side ring 45a. The bottom plate 45c is the top plate 45b
It has the same shape as that of and is disposed below the side ring 45a. Then, the side ring 45a, the top plate 45b, and the bottom plate 45c that form the heat shield 45.
Like the crucible receiver 43, is formed of an AlN sintered compact.

Further, the magnets 51, 52 are made of superconducting magnets and generate a strong magnetic field.
Are arranged to face each other in the horizontal direction. Then, by these magnets 51, 52, the raw material melt 61 in the crucible 42 is
A magnetic field in the horizontal direction is applied to.

Next, a method of manufacturing a GaAs single crystal using the above device will be described.

First, the crucible 42 was charged with 3 [kg] as a GaAs raw material so that the ratio of Ga to As was 1: 1 in molar ratio, and further B
₂ O ₃ capsule material was charged. Then Ar in the container 41
Gas was introduced to bring the inside of the container 41 into a pressurized state (70 atm).
The heater 44 heats the crucible 42 to heat and melt the raw material and the capsule material in the crucible 42 so that the liquid capsule layer 62 is located on the raw material melt 61. Then, the inside of the container 41 is
At atmospheric pressure, a magnetic field was applied in the horizontal direction by the magnets 51 and 52 so that the magnetic field strength in the raw material melt 61 was about 3500 [Oe]. In other words, the fourth region where the thermal vibration of the raw material melt is small is set.

In this state, the raw material melt 61 was seeded and adjusted to the optimum condition temperature, and then the seed crystal 63 was brought into contact with the GaAs raw material melt 61 through the liquid capsule layer 62. When the seed crystal 63 and the raw material melt 61 are sufficiently mixed, the pulling speed is 9 [mm / hr] and the pulling rotation is 1
A GaAs seed crystal having a diameter of 3 inches and 2.7 [kg] was pulled and manufactured under pulling conditions such as 0 [rpm] and crucible rotation 15 [rpm].

A wafer was cut from the GaAs single crystal thus manufactured, and 15
When growth fringes were observed with a mixed acid of H ₂ SO ₄ : 1H ₂ O ₂ : 1H ₂ O, the results shown in FIGS. 5 (a) and 5 (b) were obtained. In addition,
FIG. 5 (a) is a microscope photograph of the surface condition of the wafer prepared in this example, and FIG. 5 (b) is a microscope photograph of the wafer prepared without applying a magnetic field. As is clear from FIG. 5, the single crystal according to the method of this example in which a magnetic field is applied is extremely uniform as compared with the conventional method in which a magnetic field is not applied. Further, when a minute FET was formed using the single crystal prepared in this example and its characteristics were evaluated, a favorable result was obtained with a threshold dispersion ΔVth = 20 to 30 [mV].

As described above, according to the present embodiment, the GaAs single crystal is pulled up by applying a horizontal magnetic field corresponding to the fourth region where the thermal vibration of the raw material melt shown in FIG. It is possible to manufacture a high-quality and high-quality GaAs single crystal. Further, unlike the case of pulling up in the second region, the dependence on growth conditions (especially magnetic field strength) was low, and reproducibility was sufficiently large.

In this embodiment, the crucible receiver 43 and the heat shield 45 are made of AlN.
Since it is formed by the method described above, the contamination of the raw material melt by the oxidation product is reduced, and the quality of the crystal is improved, as compared with the conventional one formed of carbon. Furthermore, due to the reduction of porous and adsorptive carbon products, the content of oxygen, water vapor, etc. in the atmosphere is reduced, and it is possible to extend the life and stabilize the heat generation characteristics of other devices used, such as heaters. There are also advantages.

The present invention is not limited to the above embodiment. For example, the strength of the applied magnetic field is not limited to 3500 [Oe], but may be within the range of the magnetic field strength corresponding to the fourth region. The growing single crystal is not limited to GaAs but may be a III-V group semiconductor such as InP, GaP, GaSb.
However, since the magnetic field strength in the range of the fourth region changes depending on the type of single crystal grown, it is necessary to change the magnetic field strength depending on the type of single crystal. Also, the magnet for applying the magnetic field is not limited to the superconducting magnet,
Any magnetic field that can apply a magnetic field corresponding to the fourth region may be used. In addition, various modifications can be made without departing from the scope of the present invention.

[Brief description of drawings]

1 to 3 are each for explaining the basic principle of the present invention. FIG. 1 is a characteristic diagram showing a temperature change of a raw material melt with respect to a magnetic field strength, and FIG. 2 is a temperature for obtaining the above characteristic. FIG. 3 is a schematic diagram showing an example of arrangement of sensors, FIG. 3 is a schematic diagram showing thermal vibration characteristics with respect to magnetic field strength, and FIG. 4 is a sectional view showing a schematic configuration of a single crystal manufacturing apparatus according to an embodiment of the present invention. (A) and (b) are for explaining the effect of the above-mentioned embodiment and are micrographs showing the surface condition of the metal structure. 41 ... High-pressure container, 42 ... Crucible, 43 ... Crucible receiver, 44 ... Heater, 45 ... Heat shield, 46 ... Pulling shaft, 47 ... Rotating shaft, 51, 52
… Superconducting magnet, 61… Raw material melt, 62… Liquid capsule layer, 63… Seed crystal, 64… Pulled single crystal.

Front page continuation (72) Inventor Shoichi Washizuka, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research Institute Co., Ltd. Incorporated company Toshiba Research Institute (72) Inventor Masakatsu Kojima 72 Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Horikawa-cho factory (56) Reference JP-A-59-121183 (JP, A) JP Sho 58-120592 (JP, A) Japanese Patent Sho 58-50951 (JP, B2)

Claims (4)

[Claims] 1. A liquid capsule layer is formed on a raw material melt made of a III-V semiconductor contained in a crucible, a horizontal magnetic field is applied to the raw material melt, and a seed crystal is added to the raw material melt. In a method for producing a single crystal by pulling the seed crystal in a vertical direction by bringing the seed crystal into contact with a single crystal, in the direction of increasing the magnetic field strength with respect to the thermal vibration characteristics associated with the change in the magnetic field strength, In the first region, the second region where the thermal vibration is reduced, the third region where the thermal vibration is increased again, and the fourth region where the thermal vibration is reduced again, the strength of the magnetic field applied to the raw material melt is set. A method for producing a single crystal, characterized in that the size is set to be the fourth region. 2. The method for producing a single crystal according to claim 1, wherein the single crystal is GaAs and the strength of the magnetic field is set to 3000 to 10000 [0e]. 3. A crucible containing a raw material melt composed of a III-V semiconductor and a liquid capsule layer formed thereon,
A heater for heating the raw material melt in the crucible and a magnet for applying a horizontal magnetic field to the raw material melt are provided, and a seed crystal is brought into contact with the raw material melt to pull up the seed crystal. In a single crystal manufacturing apparatus for pulling up and manufacturing a crystal, a first region in which thermal vibration is large and a second region in which thermal vibration is small in a direction in which the magnetic field strength is increased with respect to the thermal vibration characteristics of the raw material melt due to the magnetic field application. When the third region in which the thermal vibration becomes large again and the fourth region in which the thermal vibration becomes small again, the magnet has a magnitude such that the intensity of the magnetic field applied to the raw material melt becomes the fourth region. An apparatus for producing a single crystal, which is for purifying the magnetic field of. 4. The magnet according to claim 3, wherein the magnet generates a magnetic field having a magnetic field strength of 3000 to 10000 [0e] applied to the raw material melt. A method for producing the single crystal described.