JPH0471871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal growth apparatus mainly used for producing high-purity silicon single crystal rods, and more particularly to a crystal growth apparatus designed to suppress heat loss due to radiation during crystal growth.

In explaining the contents of the present invention, first, a conventionally commonly used high-purity silicon single crystal growth apparatus will be explained.

FIG. 1 is a cross-sectional front view showing a single crystal growth apparatus using a conventional pulling method (CZ method). In the figure, 1 is a metal wall that constitutes a crystal growth chamber. 1-1 is the upper lid, 1-2 is the body, and 1-3 is the lower flange, all of which are forcibly cooled with cooling water.
12 is a cooling water inlet/outlet.

2 is a carbon crucible, 3 is a quartz crucible, 4 is a silicon melt, 5 is a seed crystal, and 6 is a single crystal. Reference numeral 7 denotes a pulling shaft or wire, and a seed crystal 5 is attached to the tip of the pulling shaft or wire, which is configured to be movable up and down and rotatable. 8 is a rotatable crucible holder;
9-1 is a gas inlet, 9-2 is a gas outlet or an exhaust port for reducing pressure, 10 is a heater electrode, 1
1 is for internal observation. Reference numeral 13 denotes a heating resistor (or high frequency coil), which is connected to an external power source through a heater electrode 10. 14 is an external heat insulating cylinder provided outside the heating resistor 13, and 15 is a holding cylinder for the carbon crucible 2.

Next, let's talk about the functions. Silicon melt 4 in carbon crucible 2 heated by heating element 13
The temperature of the (melt liquid) is precisely controlled by a pyrometer through the window 11. In this state, the seed crystal 5 attached to the tip of the shaft 7 is brought into gentle contact with the melt surface. A single crystal 6 is generated by cooling from the seed crystal 5, and the single crystal 6 grows by pulling up the shaft 7. At this time, the inside of the crystal growth chamber is observed through the window 11 to control the diameter and shape of the single crystal.

FIG. 2 is a cross-sectional front view showing a conventional single crystal growth apparatus using the floating zone melting method (FZ method). 1 in the diagram
Structural parts 1 to 12 are the same as those in FIG. However, unlike the crucible pedestal shown in FIG. 1, 8 is a shaft that holds the seed crystal 5. Further, the body of the metal wall 1 is water-cooled. 16 is raw material polycrystal,
17 is a high frequency coil, and 18 is its electrode. Its functions will be described below.

An induced current is generated in the raw material polycrystalline 16 by the high frequency coil 17, and the silicon melt 4 (molten zone) is generated by the heat generation, and the molten zone is formed by the surface tension between the raw material polycrystalline 16 and the single crystal 6. is retained. In this state, the single crystal 6 and the raw material polycrystal 16 are moved relative to the high frequency coil 17, thereby growing the single crystal 6. At that time, the dimensions of the single crystal 6 are controlled by the moving speed of the material and the high frequency current.

In the conventional single crystal growth equipment using the pulling method and floating zone melting method described above, a lot of heat is lost through radiation from the heating element and the surface of the melt, and excessive power is required. . In particular, in the case of a single crystal growth apparatus using the pulling method, the initial material polycrystal is placed in a crucible, the crucible is heated by heating from a heating element, and the polycrystal is melted by heat conduction and radiation. In this case, the surface (upper part) of the material crystal loses heat through radiation and is difficult to melt, and sometimes it adheres to the inner surface of the crucible, so it is necessary to heat the entire material to a higher temperature, which increases contamination from the crucible material. There were also problems. Also, during crystal growth, heat loss occurs due to thermal radiation from the surface over a long period of time, resulting in excessive power consumption. In addition, this heat radiation is absorbed by the inner surface of the device, resulting in an increase in the temperature of the wall of the device, and a large amount of cooling water is required to cool it.

In order to suppress the loss of radiant heat during crystal growth, a single crystal growth apparatus using a pulling method is disclosed in JP-A-58-36998, in which a reflecting plate is provided above the crucible. However, with this device, the molten surface inside the crucible is in the shadow of the reflector, so the window (11
It becomes impossible to observe the melt surface from the point (indicated by ), making pulling control difficult. Further, there is a problem in that the single crystal is damaged due to falling of foreign matter (SiO) attached to the reflector. Furthermore, since the reflector is not cooled, there is a problem of single crystal contamination due to the reflector, and even if the reflector is water-cooled, if water leaks, there is a risk that the water will enter the crucible and cause an explosion. There are safety issues. Therefore, the heat loss prevention technology disclosed in Japanese Patent Application Laid-Open No. 58-36998 lacks feasibility.

The present invention was made in view of such circumstances, and
It is an object of the present invention to provide a crystal growth apparatus that suppresses loss of radiant heat during crystal growth and is free from the risk of adversely affecting crystal growth. The structure and operation of the crystal growth apparatus of the present invention will be explained in detail below.

FIG. 3 is a sectional front view showing an embodiment in which the present invention is applied to a single crystal growth apparatus using a pulling method. In the figure, 19-1 is formed by directly lining the inner surface of the upper lid 1-1 of the metal wall 1 constituting the crystal growth chamber with a metal having a high heat reflectance, such as silver, gold, aluminum, etc. by pasting or plating. It is a reflective layer. The reflective layer is sufficiently cooled by the forced water-cooled upper cover 1-1 and does not become a source of contamination within the apparatus. Silver is the most suitable material for the reflective layer. In the case of silicon semiconductors, gold tends to create deep energy levels that degrade the properties of the semiconductor material, while aluminum has an unstable surface and is easily reactive to reactive gases, making it an acceptor (P-type) for silicon. Since it is an impurity and has an abnormally fast diffusion rate, it has the disadvantage of decreasing purity. On the other hand, silver has the advantage of having low solubility in silicon, hardly affecting its properties and purity when sufficiently water-cooled, and being easy to process.

This reflective layer efficiently returns radiant heat from the silicon melt surface, the crucible, and the heating element to the melt surface by reflection to enhance the heat retention effect and prevent the temperature of the upper lid 1-1 from rising.

Similarly, reference numeral 19-2 is a reflective layer lining the inner surface of the body portion 1-2 to prevent loss of radiant heat from the heating element to the side surfaces. 19-3 is a lining provided on the inner surface of the lower flange 1-3, which prevents radiant heat loss from the bottom of the pulling furnace and enhances the heat retention effect.
Reference numeral 20 in the figure indicates a reflective layer lined on the inner surface of the crucible pedestal 8 in order to prevent heat radiation from the bottom surface of the crucible 2 and to keep the bottom surface of the crucible 2 warm.

If the present invention is applied to a crystal growth apparatus using the pulling method, it is possible to save power during melting raw materials by preventing loss of radiant heat, and at the same time shorten melting time, and also significantly reduce power during crystal growth, resulting in energy savings. It can enhance the effect. In addition, a reflective layer that prevents loss of radiant heat is directly lined on the inner surface of the metal wall, preventing obstacles from protruding into the apparatus, making it impossible to prevent the melt surface inside the crucible from being observed through the window.
Perform lifting control without any trouble. Furthermore, since the metal wall is water-cooled and the reflective layer is cooled sufficiently, there is no risk of contaminating the single crystal, and even if the water used to cool the metal wall leaks, it will not cause an explosion. Furthermore, even if foreign matter adhering to the surface of the reflective layer falls, there is no risk of damaging the single crystal.

FIG. 4 is a sectional front view showing an embodiment in which the present invention is applied to a single crystal growth apparatus using a floating zone melting method. In the figure, 19-2 is a reflective layer lined on the inner surface of the water-cooled body of the metal wall 1 constituting the crystal growth chamber, and the energy-saving effect is achieved in the same way as in the case of the single-crystal growth apparatus using the above-mentioned pulling method. It can be fried, and the water-cooled body can be expected to provide sufficient cooling, so the reflective layer will not become a source of contamination.

Although the above description has been made regarding a crystal growth apparatus for silicon, the present invention is also applicable to crystal growth apparatuses for other types of materials, and can also be applied to normal pressure, reduced pressure, or pressurized conditions. You can. Additionally, the reflective layer needs to line the water-cooled metal wall, but not all of it.

As described above, the crystal growth apparatus of the present invention uses radiant heat on the inner surface of the metal wall that surrounds the high-temperature crystal growth chamber in the apparatus and is forcibly cooled by cooling water. The reflective layer with high reflectance is directly lined and forcedly cooled by the metal wall, which reduces the loss of radiant heat and saves energy.It also prevents the reflective layer from becoming a source of contamination, resulting in high-quality crystals. This has the effect of making it possible to manufacture it economically. In addition, even in single crystal growth equipment using the pulling method, the reflective layer does not interfere with pulling control, and even if foreign matter attached to the reflective layer falls, it does not destroy the single crystal, and furthermore, the metal wall Since the cooling water is used to cool the reflective layer, there is no need for a cooling mechanism, and even if the water leaks, it will not cause an explosion, providing excellent safety.

[Brief explanation of the drawing]

Figures 1 and 2 show the conventionally commonly used pulling method (CZ method) and floating zone melting method (FZ method), respectively.
FIGS. 3 and 4 are cross-sectional front views showing an embodiment of the present invention applied to a single-crystal growth apparatus using a pulling method and a floating zone melting method, respectively. be. 1...Metal wall, 1-1...Top lid, 1-2...
Body part, 1-3... lower flange, 2... carbon crucible, 3... quartz crucible, 4... silicon melt, 5... seed crystal, 6... single crystal, 7... pulling shaft, 8 ... Crucible pedestal, 9-1 ... Gas inlet, 9-2 ... Gas outlet, 10 ... Heater electrode, 11 ... Observation window, 12 ... Water inlet and outlet of cooling water pipe, 13... Heating resistor (or high frequency coil), 14... Heat insulating tube, 15... Crucible support tube, 16... Raw material polycrystal, 17... High frequency coil, 18... High frequency coil electrode, 19-
1, 19-2, 19-3, 20... Reflective layer.

Claims (1)

[Claims] 1. In a metal crystal growth apparatus, a reflective layer with high radiant heat reflectivity is directly lined on the inner surface of the metal wall that surrounds the high-temperature crystal growth chamber in the apparatus and is forcibly cooled with cooling water. A crystal growth apparatus characterized in that forced cooling is performed by the metal wall.