JPH0535119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an apparatus for growing single crystals of silicon, gallium arsenide, etc. used in semiconductors.

"Prior Art" In order to grow single crystals such as silicon for semiconductors or gallium arsenide, silicon or gallium arsenide placed in a crucible 12 is melted by a graphite heating element 20 as shown in FIG. , the lower end of a crystal puller 4 consisting of a pulling shaft with a seed crystal attached to the lower end, a pulling cable, a pulling chain, etc. is inserted into a molten liquid 11 of gallium silicon, etc. (hereinafter simply referred to as molten liquid). This is done by gently pulling up the lifting device 4 while rotating it.

High-purity nitrogen or inert gas is introduced into the water-cooled metal sealed container 1 from a gas supply port 30 provided at the top of the container 1, and externally from a discharge port 50 provided at the bottom of the container. is being discharged. but,
As the single crystal grows, the level of the molten liquid in the crucible 12 decreases, so in order to minimize changes in conditions such as the temperature of the liquid level and the flow of gas, the position of the liquid level is always kept constant. The lift shaft 14 located at the bottom of the container is raised while being rotated in the opposite direction to the crystal puller 4 in accordance with the drop in the liquid level. This crucible 12 is supported by a susceptor 13 made of graphite,
Further, the heating element 20 is supported by an electrode 21 for power supply.

``Problem to be solved by the invention'' It is possible to remove the reaction gas between the melt and the crucible that is on the upper surface of the melt, and to remove the melt and single crystal from impurity gas generated from graphite material and other parts. For the purpose of blocking, various improvements have been made to the blowing method and flow rate of nitrogen or inert gas, but it is quite difficult to block impure gases generated from graphite materials and other materials from crystals. The present invention aims to eliminate such conventional drawbacks.

"Means for Solving the Problems" The present invention provides a crystal growth chamber located in the center with a partition made of graphite inside a sealed container in which a crystal puller is rotatably and vertically movable from above. Gas inlets are provided between the upper and lower ends of this partition wall and the inner wall of the container, respectively, and the crystal growth chamber is divided into two, with a heating element storage chamber located around the chamber, and gas inlets are provided between the upper and lower ends of this partition wall and the inner wall of the container, respectively. A graphite susceptor that holds the crucible facing the upper vessel is arranged in the container from below so as to be rotatable and vertically movable, and a gas generation prevention film is formed on the surface of the partition wall and the inner and outer surfaces of the susceptor. A heat insulating section and a graphite heating element are installed in the heating element storage chamber, a gas supply port is provided at the top of the container, and an exhaust port is provided at the bottom of the crystal growth chamber and the heating element storage chamber, respectively. A configuration in which the pressure in the crystal growth chamber is set higher than the pressure in the heating element storage chamber is a means for solving the above problem.

``Operation'' The surfaces of the graphite partition walls and susceptor are coated with a film to prevent gas generation.
It is possible to prevent the generation of impure gases that have a negative effect on the growth of single crystals, and since the pressure inside the crystal growth chamber is higher than that in the heating element storage chamber, impure gases generated from the heating element do not flow into the crystal growth chamber. The heating element is discharged from an exhaust port provided in the heating element storage chamber.

``Example'' 1 is a water-cooled metal sealed container that is isolated from the outside world, and has a small-diameter cylindrical portion 2 formed at the top, and a gate valve 3 attached to the outer periphery of this cylindrical portion 2.
A crystal puller 4 consisting of a pull-up shaft, a pull-up cable, a pull-up chain, etc. is connected to a drive source (not shown) at its upper end and is rotatably and vertically movable. The inside of this container 1 is divided into two by a partition wall 5 made of graphite into a crystal growth chamber 6 located at the center and an annular heating element storage chamber 7 located around this crystal growth chamber. Between the upper and lower ends of the partition wall 5 and the inner surface of the container 1, spaced inlet ports 8a and 8b are provided.

The entire surface of the partition wall 5 facing the crystal growth chamber 6 is coated with, for example, silicon carbide (Sic) or silicon nitride (Si ₃ N ₄ ).
It is coated with a film to prevent gas generation.
In addition, a seed crystal 10 is provided at the bottom end of the single crystal growth apparatus 6.
A push-up shaft 14 fixed to the lower part of a graphite susceptor 13 that houses a crucible 12 containing a melt 11 of silicon, gallium arsenide, etc. inside the crystal puller 4 facing the crystal puller 4 to which the crystal puller 4 is attached can be rotated and moved up and down. is installed from below the container 1. Further, the inner and outer surfaces of the susceptor 13 are coated with a film 15 for preventing gas generation.

A heat insulating section 16 is attached to the inner surface of the container 1 in an annular heating element housing chamber 7 located around the crystal growth chamber 6. This heat insulating part 16 may be a graphite cylinder 17 filled with fiber-like graphite 18 as shown in FIGS. 3 and 4, or a graphite cylinder 17a filled with fiber-like graphite 18 as shown in Graphite heating element 2, which is arranged concentrically in multiple layers and will be described later.
There are some that shield heat radiation from 0. The above-described graphite heating element 20 is placed in the heating element housing chamber 7, and is connected to an external power source via electrodes 21,21.

22 is a first exhaust port provided at the bottom of the crystal growth chamber 6; 23 is a second exhaust port provided at the bottom of the heating element storage chamber 7;
The pressure is maintained slightly higher than that in the crystal growth chamber 6.
Inert gas flows into the heating element storage chamber 7 through the inlets 8a and 8b. However, it does not flow in the opposite direction. Reference numeral 30 denotes a gas supply port provided at the top of the container 1 for supplying nitrogen or an inert gas into the container 1.

FIG. 2 shows the flow of gas. The inside of the container 1 is divided into two by a graphite partition wall 5 into a crystal growth chamber 6 and a heating element storage chamber 7. A differential pressure regulator 26 is provided between the exhaust pump 25 and the exhaust pump 25 . This differential pressure regulator 26 sets the pressure in the crystal growth chamber 5 higher than that in the heating element storage chamber 7, and keeps the pressure in the crystal growth chamber 6 constant between a vacuum state and atmospheric pressure. be able to. Note that the pressure inside the crystal growth chamber 6 is measured by an internal pressure gauge 27.
Also, the pressure difference between the crystal growth chamber and the heating element can be read by a differential pressure gauge 28.

Next, to explain the operation of this embodiment, the seed crystal 10 of silicon or gallium arsenide inserted into the melt 11 in the crucible 12 by heating with the graphite heating element 20 is heated by the graphite heating element 20. When the single crystal, which is the seed crystal 10, is rotated and raised while attached to the lower end, the single crystal, which is the seed crystal 10, grows sequentially.

The nitrogen or inert gas supplied from the gas supply port 30 covers the surface of the single crystal or the melt to prevent any adverse effects on the single crystal, and further passes between the partition wall 5 and the susceptor 13 and passes through the first is discharged to the outside from the exhaust port 22.

In this case, since the pressure inside the heating element storage chamber 7 is lower than that inside the crystal growth chamber 6, a part of the gas is divided and flows into the heating element storage chamber 7 through the gas inlets 8a and 8b, and then, It is discharged to the outside from the second exhaust port 23. Therefore, the heating element 20 and the heat insulating part 16
Impure gas generated from the crystal growth chamber 6 does not enter into the crystal growth chamber 6.

"Effect of the invention" The present invention has the following effects.

By providing a graphite partition wall coated with a film for preventing impurity gas generation on the side wall surface of the crystal growth chamber, when the temperature is raised in the pre-stage of the single crystal growth process, the heat capacity of the partition wall is increased. Although the amount of heat is only increased slightly, the temperature increase rate remains the same as in the conventional method.

Since this partition wall is located between the heating element and the crucible after reaching a predetermined temperature, it is in the middle of heat convergence except for a time lag, so there is no temperature difference, but rather the heating element itself It has the advantage that it buffers the temperature unevenness of the single crystal and helps to stabilize the temperature of the single crystal growth area, resulting in good results.

By setting the pressure in the crystal growth chamber higher than that in the heating element housing chamber, it is possible to prevent impurity gases generated from the heating element and the heat insulating section from entering the crystal growth chamber, thereby preventing adverse effects on single crystal growth.

By providing an inert gas generation prevention film on the surface of the graphite partition wall and the inner and outer surfaces of the susceptor, it is possible to prevent the generation of impure gas within the crystal growth chamber.

[Brief explanation of drawings]

Fig. 1 shows an embodiment of the present invention; Fig. 2 is an explanatory diagram showing the gas flow of the device; Fig. 3 is a plan view of the heat insulating section;
The figures are a cross-sectional view taken along the line A-A in Figure 3, a plan view of another heat insulating section, and a cross-sectional view taken along the line B-B in Figure 6.
The figure is a sectional view of a conventional device. DESCRIPTION OF SYMBOLS 1... Container, 4... Crystal puller, 5... Graphite partition, 6... Crystal growth chamber, 7... Heating element storage chamber, 8a, 8b... Gas inlet, 9, 15...
...Coating for preventing impure gas generation, 12... Crucible, 13
...Susceptor made of graphite, 16... Heat insulation part, 20... Heating element made of graphite, 22, 23
...Exhaust port, 30...Gas supply port.

Claims (1)

[Claims] 1. The inside of a sealed container in which a crystal puller is rotatably and vertically movable from above is divided into two by a graphite partition wall into a crystal growth chamber located in the center and a heating element storage chamber located around the crystal growth chamber. , gas inlets are provided between the upper and lower ends of the partition wall and the inner wall of the container, and within this crystal growth chamber there is a graphite crucible that holds a crucible facing the puller with a seed crystal attached to the lower end. A susceptor made of aluminum is placed in the container from below so as to be rotatable and movable up and down, and a film for preventing gas generation is formed on the surface of the partition wall and the inner and outer surfaces of the susceptor. A gas supply port is provided at the top of the container, and an exhaust port is provided at the bottom of the crystal growth chamber and the heating element storage chamber, so that the pressure inside the crystal growth chamber is controlled by the pressure inside the crystal growth chamber. A single crystal growth apparatus characterized in that the pressure is set higher than that of .