JPS61242985A - Apparatus for production of semiconductor single crystal - Google Patents

Abstract

PURPOSE:To suppress the heat dissipation from the circumferential edge of an opening effectively, and to obtain a high-quality single crystal, by using an inner heat-insulation materials having a shape to cover not only the outer circumference of a crucible but also the circumferential edge of the opening, and insulating the crucible in a semiconductor single crystal production apparatus using said heat-insulation material. CONSTITUTION:The semiconductor single crystal production apparatus is furnished with the crucible 6 to hold the semiconductor material 7 for growth, the upper, outer and inner heat-insulation materials 3, 4, 5', and a single crystal pulling up apparatus 10. The crucible 6 has anisotropic thermal conductivity and the heat-dissipation is large at the circumferential edge of the opening part. The inner heat-insulation material 5' has a shape to cover not only the outer circumference of a crucible 6 but also the circumferential edge of the opening of the crucible to suppress the heat-dissipation from the circumferential edge of the opening. The inner heat-insulation material 5' is made of carbon, aluminum nitride, quartz, PBN, etc. The temperature distribution in the crucible 6 is higher at the circumferential part than at the middle part, and a high- quality single crystal can be grown by the use of the crucible.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a semiconductor single crystal manufacturing apparatus, and more particularly to a semiconductor single crystal manufacturing apparatus for growing a single crystal by a pulling method using a crucible made of PBN (pyrolytic boron nitride). .

(Technical Background of the Invention) As one of the methods for manufacturing semiconductor single crystals, the pulling method is a method that is very widely used. In particular, LEC (Liquid E
ncapsulated Czochralski
) method is used. FIG. 7 shows a semiconductor single crystal manufacturing apparatus using the LEC method, which has been commonly used in the past. This device has a heating heater 2 inside a high pressure resistant container 1.
, an upper heat retaining member 3, an outer heat retaining member 4, and an inner heat retaining member 5 are provided. A crucible 6 is placed in the center of the high pressure container 1, and a semiconductor material melt 7 is contained in the crucible 6. The surface of the semiconductor material melt 7 is sealed with a liquid glass sealant 8 to prevent the semiconductor material melt 7 from evaporating. The crucible 6 and the semiconductor material melt 7 are heated by the heater 2 and kept warm by the heat insulating members 3, 4.5. The crucible 6 is placed on a drive shaft 9 that can be moved up and down and rotated, and this rotation provides appropriate convection to the semiconductor material melt 7.

A pulling device 10 is provided at the top of the crucible 6.

This lifting device 10 can move up and down and rotate.

A seed crystal 11 is attached to the lower end of this pulling device 10, and after the seed crystal 11 is brought into contact with the semiconductor material melt 7, the semiconductor single crystal 12 is gradually pulled up while being rotated.

[Problems with background technology]

Although quartz is sometimes used as the material for the crucible 6, a crucible made of PBN is generally used when impurities such as Si are disliked. However, a crucible made of PBN has anisotropy in terms of heat conduction, as shown in FIG. 8(a). That is, the thermal conductivity in the six directions in the figure is much larger than the thermal conductivity in the B direction in the figure. For example, at 800°C, the thermal conductivity in the B direction is 0.007 cal/cm, s
ec, about ℃, while the thermal conductivity in six directions is 0.
．． 15 cal/amsec, ℃. In a quartz crucible, 0.003 cal/cm in both the six directions and the B direction,
sec, °C, it means that the PBN crucible has extreme anisotropy regarding heat conduction.

This is explained by the cross-sectional view of a PBN crucible shown in FIG. 8(b). As can be seen from this figure, the PBN crucible is composed of multiple layers of PBN, and each layer has anisotropy regarding heat conduction between the plane direction of the layer and the direction perpendicular thereto. Therefore, six directions (plane direction of the layer) and B
(direction perpendicular to the plane of the layer) with respect to thermal conduction.

As described above, in a crucible made of PBN, the thermal conductivity in six directions is extremely high, so that the heat in the crucible is mainly dissipated from six directions. This heat dissipation reduces the temperature of the crucible. FIG. 9 is a graph showing the temperature distribution inside a crucible during single crystal growth using a conventional apparatus. Figure (a)
1 shows a crucible made of PBN, and FIG. 3(b) shows a crucible made of quartz. In a quartz crucible, there is less heat dissipation, so the temperature distribution inside the crucible is much higher at the periphery than at the center.

In a PBN crucible, the temperature difference between the periphery and the center becomes considerably small due to heat dissipation.

In order to grow a high-quality single crystal, it is necessary that the temperature at the periphery of the crucible be sufficiently higher than the temperature at the center. This reduces the difference between the temperature of the side of the pulled single crystal and the ambient temperature around it by increasing the temperature of the surrounding area in the crucible, suppressing the escape of heat from the side of the single crystal, This is because it is possible to create an appropriate solid state near the interface between the crystal and the melt, which is necessary to obtain a high-quality single crystal. However, with conventional equipment, it is difficult to raise the temperature of the surrounding area of the crucible to a sufficiently high temperature, which results in a large amount of heat escaping from the sides of the single crystal. It was difficult to obtain a solid state near the interface with the melt.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a semiconductor single crystal manufacturing apparatus that can grow a high quality single crystal by a pulling method.

[Summary of the invention]

The present invention is characterized in that a semiconductor single crystal manufacturing apparatus for growing a single crystal by a pulling method includes a crucible that accommodates a semiconductor material to be grown, a heating device that heats the crucible, and an outer circumferential surface of the crucible and an opening periphery. The present invention is equipped with a heat insulating member to cover the semiconductor material and a pulling device that pulls up the semiconductor material to form a single crystal, thereby suppressing the dissipation of heat from the opening of the crucible and making it possible to grow a high quality single crystal. be.

[Embodiments of the invention]

The present invention will be described below based on illustrated embodiments. 1st
The figure is an explanatory diagram of an embodiment of a semiconductor single crystal manufacturing apparatus according to the present invention. Here, the same components as those of the conventional device shown in FIG. 7 are given the same reference numerals, and the description thereof will be omitted. The difference from the conventional device is the shape of the inner heat retaining member 5'. FIG. 2 is an enlarged view of the vicinity of the crucible 6, and as shown in this figure, the inner heat retaining member 5' has a shape that covers not only the outer peripheral surface of the crucible 6 but also the periphery of the opening. By covering the periphery of the opening with the heat insulating member in this way, it is possible to effectively suppress the dissipation of heat from the periphery of the opening, thereby preventing a drop in the temperature of the crucible. Some examples of the shapes of the inner heat retaining member 5' are illustrated in FIGS. 3(a) to 3(d). The figure (a) shows a shape in which the inner heat retaining member 5' is in contact with the wall surface of the crucible 6 and extends inside the periphery of the opening, and the figure (b) shows the shape between the crucible and the inner heat retainer. A space is provided between the inner heat insulating member 5' and the wall surface of the crucible 6 in consideration of the difference in the coefficient of thermal expansion of
The figure (C) shows a member 5 in which the inner heat retaining member 5' covers the upper end of the periphery of the opening and does not go inside, and the figure (d) shows a member 5 in which the inner heat retaining member 5' covers the outer peripheral surface of the crucible 6. '-1
and a member 5'-2 that covers the periphery of the opening. Materials such as carbon, aluminum nitride, quartz, and PBN may be used for the inner heat retaining member.

FIG. 4 is a graph showing the temperature distribution in the crucible during single crystal growth using the apparatus according to the present invention. As is clear from a comparison with FIG. 9(b), despite the use of a PBN crucible, the temperature distribution is close to that of a conventional quartz crucible. FIG. 5 is a diagram showing the in-phase state near the liquid surface of the semiconductor material melt, that is, near the interface between the crystal and the melt during the pulling process using a PBN crucible. Same figure (
Figure a) is a solid phase diagram of a conventional device, and figure (b) is a solid phase diagram of a device according to the present invention. In the conventional device, heat dissipates from the walls of the crucible so much that the boundary surface waves greatly and fluctuates from the periphery to the center, but in the device according to the present invention, the fluctuation is small compared to this.

FIG. 6 is a graph showing the defect distribution of single crystals produced by the conventional apparatus and the apparatus according to the present invention. The solid line shows the single crystal produced by the apparatus according to the present invention, and the broken line shows the single crystal produced by the conventional apparatus. It can be seen that in the latter case, the dislocation density becomes extremely high near the periphery, but in the former case, the dislocation density is suppressed even near the periphery, and a high-quality single crystal can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, in the semiconductor single crystal manufacturing apparatus using the pulling method, the outer circumferential surface of the crucible and the periphery of the opening are covered with a heat insulating member, so that the dissipation of heat from the opening of the crucible is suppressed, and high quality It becomes possible to grow single crystals.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of a semiconductor single crystal manufacturing apparatus according to the present invention, FIG. 2 is an enlarged view of the vicinity of a crucible in the apparatus shown in FIG. 1, and FIGS. 1 is a diagram showing the shape of a heat-retaining member used in the apparatus shown in FIG. A diagram showing the solid phase state near the liquid surface of the semiconductor material melt during the pulling process using a PBN crucible, and FIG. 6 is a graph showing the defect distribution of single crystals produced by the conventional device and the device according to the present invention. , 7th
The figure is an explanatory diagram of a semiconductor single crystal manufacturing apparatus using the LEC method, which is commonly used in the past. Figures 8 (a) and (b) are explanatory diagrams showing the direction of heat conduction in a PBN crucible. Figure 9 (a) , (b
) is a graph showing the temperature distribution inside the crucible during single crystal growth using a conventional device. 1...High pressure container, 2...Heating heater, 3...
Upper heat insulating member, 4... Outer heat insulating member, 5, 5'...
Inner heat retaining member, 6... Crucible, 7... Semiconductor material melt, 8... Liquid glass sealant, 9... Drive shaft, 1
0... Pulling device, 11... Seed crystal, 12... Semiconductor single crystal. Applicant's agent Seito Inomata 1 Cause Figure 6 Kaya 1

Claims (1)

[Claims] 1. A semiconductor single crystal manufacturing apparatus for growing a single crystal by a pulling method, which comprises: a crucible containing a semiconductor material to be grown; a heating device for heating the crucible; and a heating device for heating the crucible. A semiconductor single crystal manufacturing apparatus comprising: a heat insulating member that covers an outer circumferential surface and a periphery of an opening; and a pulling device that pulls up the semiconductor material to form a single crystal. 2. The pulling method is LEC (Liquid Encapsul)
2. The semiconductor single crystal manufacturing apparatus according to claim 1, wherein the semiconductor single crystal manufacturing apparatus is an a-ted Czochralski method. 3. The semiconductor single crystal manufacturing apparatus according to claim 1 or 2, wherein the crucible is made of PBN (pyrolytic boron nitride). 4. Claim 1, characterized in that the heat insulating member is made of carbon, aluminum nitride, quartz, or PBN.
3. A semiconductor single crystal manufacturing apparatus according to any one of items 1 to 3.