KR100766720B1 - Focusing tube of saw type - Google Patents

Abstract

A serrated focusing tube for use in single crystal growth of silicon carbide is provided to suppress polycrystalline growth of a process gas and prevent the process gas from entering a single crystal region by focusing the process gas sublimated from silicon carbide powder. A serrated focusing tube for use in single crystal growth of silicon carbide through sublimation technique includes a focusing portion(10) provided with rectangular grooves(20) for focusing a process gas moving towards a surface of a seed crystal, a seat portion(40) for installing the focusing tube in a furnace, and a passage(30) through which the process gas moves towards the seed crystal.

Description

Serrated focusing tube {Focusing tube of saw type}

1 is a cross-sectional view showing a crucible equipped with a conventional focusing tube.

Figure 2 is a three-dimensional view showing the toothed focusing tube according to the present invention.

Figure 3 is a cross-sectional view showing a crucible equipped with a toothed focusing tube according to the present invention.

Figure 4 is a silicon carbide photo grown after using a crucible equipped with a conventional focusing tube.

5 is a schematic diagram of a process of reducing the diameter of the seed crystals by sublimation of the seed crystals by the heating of the focusing tube in the crucible equipped with a conventional focusing tube.

6 is a schematic diagram of a process in which polycrystals invade where seed crystals are sublimated in a crucible equipped with a conventional tube.

Figure 7 is a silicon carbide single crystal ingot photo grown in a crucible equipped with a toothed focusing tube according to the present invention.

<Explanation of symbols for main parts of the drawings>

10: focusing part 70: crucible lower lid

10a: focusing tube 80: seed crystal

20: tooth groove 90: silicon carbide powder

30: passage part 100: silicon carbide single crystal grown in seed crystal

40: seating portion 110: sublimed seed crystal single crystal

50: crucible upper lid 120: grown silicon carbide

60: crucible body 130: intruded polycrystalline silicon carbide

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a sawtooth focusing tube which prevents polycrystalline intrusion and seed crystals from being sublimated and reduced in diameter as a silicon carbide single crystal growth method using a sublimation method. More specifically, a serrated focusing tube is mounted inside the crucible where seed crystal is located to focus the sublimated raw material gas from silicon carbide powder to prevent polycrystalline growth and invasion into the single crystal region, and to induce high frequency induction heating. The present invention relates to a toothed focusing tube which minimizes eddy current generation by the seed and prevents seed crystals from being sublimated.

The methods of growing silicon carbide single crystals include liquid phase deposition (LPE), sublimation (CVD), and chemical vapor deposition (CVD). Among them, the most popular sublimation method is seeding by sublimation of a solid material into a gas phase. It is a method of growing single crystals by inducing recrystallization by diffusing to crystals.

Briefly, the silicon carbide powder as a raw material is charged into the graphite crucible and the seed crystal is placed on the crucible (Fig. 1). The most commonly used heating method for growing silicon carbide single crystal is high frequency induction heating. In general, a coil used for growing silicon carbide single crystal is a circular multi-coil. The center of the coil is called the hot zone, and the heating depth of the hot zone is slightly deeper than the outer shell so that the temperature is relatively higher. By placing the center of the crucible higher than the hot zone to form a relative temperature gradient, the silicon carbide powder sublimes, at which time the sublimed raw material gas moves to a relatively low temperature seed crystal surface to recrystallize and grow into a single crystal.

At this time, the focusing tube (10a of FIG. 1) is mounted as a method for improving the growth rate of the silicon carbide single crystal and preventing the intrusion of polycrystal. This is due to the characteristic of the focusing tube narrowing as it moves to the seed crystal surface so that the source gas can be focused. That is, the source gas collides with the inner wall of the focusing tube, which narrows as it moves to the seed crystal surface, and is concentrated at the center. Due to this phenomenon, a large amount of source gas can be collected on the seed crystal surface, thereby increasing the growth rate of the single crystal. On the other hand, in the region other than the seed crystal (50 in FIG. 1), the minimum amount of source gas is moved to grow the polycrystal with low growth rate. Therefore, it is impossible to infiltrate the polycrystal into the single crystal region having a relatively higher growth rate, thereby preventing the intrusion of the polycrystalline region into the single crystal region.

However, in the conventional focusing tube (10a of FIG. 1), a large amount of heat exists due to heat generated by high frequency induction heating, conduction heat from the crucible body, and radiant heat. That is, the high frequency induction heating causes the focusing tube to generate heat, and conduction heat and radiant heat from the crucible body are transferred to the focusing tube, thereby forming the focusing tube at a higher temperature than the surroundings. This phenomenon causes the seed crystals to sublimate (10a, 80 in Fig. 5) due to the relatively high heat of the focusing tube, which not only reduces the diameter of the seed crystals (110 in Fig. 4) but also penetrates polycrystals into the single crystals to be grown later. (10a, 80, 120, 130 in Fig. 6). In addition, the thermal shock received at this time may cause the separation of the seed crystals and lower the seed crystal crystalline.

An object of the present invention was invented to solve the above problems, by using a sawtooth focusing tube having a rectangular groove (20 in Fig. 2) to focus the raw material gas to the surface of the seed crystal to improve the single crystal growth rate and polycrystal invasion By providing a single crystal ingot that can contribute to the expansion of the diameter of the single crystal and the increase of the wafer yield, and at the same time, a rectangular groove is formed in the focusing tube focusing section to suppress the eddy current generated by the high frequency induction heating, The purpose of the sawtooth focusing tube (FIG. 2) is to significantly reduce the heat generated in the negative portion and to reduce the sublimation phenomenon and thermal shock of the adjacent seed crystal (80 in FIG. 3).

The present invention provides a serrated focusing tube (FIG. 2) in which a source gas is focused on a seed crystal (80 in FIG. 3) surface in order to achieve the above object, which occurs inside the crucible (50, 60, 70 in FIG. 3). A passage portion (30 in FIG. 2) in which the source gas moves to the seed crystal, a focusing portion (10 in FIG. 2) for focusing the source gas in the seed crystal, and a rectangular groove (20 in FIG. 2) to prevent the heat generation phenomenon of the focusing portion. And a sawtooth focusing tube (FIG. 2), characterized in that the sawtooth focusing tube comprises a seating portion (40 in FIG. 2) seated on the inner wall of the crucible.

With reference to the accompanying drawings, it will be described an embodiment of the present invention in more detail. However, the present invention is not limited to the embodiments described below, but may be implemented in various other forms, and the present embodiments are provided to make the disclosure of the present invention complete. The same reference numerals in the drawings refer to the same.

Figure 3 shows the internal cross section of the crucible to which the serrated focusing tube according to the present invention is grown during silicon carbide single crystal growth.

Referring to the drawings, the crucible lower lid (70 in FIG. 3) is fixed to the crucible body (60 in FIG. 3), and then silicon carbide powder (90 in FIG. 3) is charged. A serrated focusing tube (FIG. 2) is mounted on the top of the crucible body (FIG. 3) and the seed crystal (80 in FIG. 3) and the crucible upper lid (50 in FIG. 3) are fixed to the crucible body. This is mounted in a silicon carbide single crystal growth furnace (not shown). At the time of mounting, the crucible is put into the growth furnace to which the circular multi-coil type is applied, and the silicon carbide powder is sublimed by forming a temperature gradient by mounting the center of the crucible at a position higher than the hot zone. At this time, the generated raw gas is moved to the surface of the seed crystal having a relatively low temperature and recrystallized to grow into a single crystal.

In this process, the preferred growth temperature for growing silicon carbide single crystal is from 2000 degrees Celsius to 2300 degrees Celsius in the upper crucible and 2200 degrees to 2500 degrees Celsius in the lower crucible. In addition, the growth pressure of the silicon carbide single crystal is preferably between 1 millibar (mbar) and 350 millibar (mbar).

Under the above growth conditions, silicon carbide powder (90 in FIG. 3) begins to sublimate in the lower part of the crucible, and the generated source gas collides with the narrower focusing part through the passage part and is concentrated to the center of the seed crystal. This causes a lot of source gas to collect on the surface of the seed crystals to increase the growth rate of the single crystal. On the other hand, since the minimum amount of source gas is moved to a region other than the seed crystal (50 in FIG. 3), the growth rate of the polycrystal is lowered, thereby preventing penetration into the relatively high growth single crystal. At the same time as the above phenomenon, the focusing tube focusing section has a rectangular groove with a predetermined interval, so that the high frequency induced area is reduced by the rectangular groove even when the eddy current is generated due to the high frequency induction heating, thereby suppressing the heating phenomenon due to the eddy current. That is, the high-frequency induction heating causes eddy currents to form in the sawtooth focusing tube to reduce heat generation, and the heat conducted in the crucible also decreases due to the rectangular groove, so that the sawtooth focusing tube forms a temperature similar to the surroundings. This has little effect on adjacent seed crystals, so that sublimation of seed crystals does not occur (10a, 80 in Fig. 5), which causes the diameter of the seed crystals to be reduced (110 in Fig. 4), thereby invading polycrystals (10a in Fig. 6). , 80, 120, 130) can be prevented. In addition, since the local thermal shock is significantly reduced, it is possible to obtain a high quality silicon carbide single crystal (Fig. 7) ingot because it prevents seed crystal departure phenomenon and crystalline degradation of seed crystal.

The rectangular grooved toothed focusing tube of the present invention is provided with grooves at regular intervals, thereby preventing sublimation of seed crystals due to heat generation of focusing tubes generated during growth of conventional silicon carbide single crystals, and by reducing diameter of seed crystals. To prevent polycrystalline growth and to invade into the single crystal region. Further, by suppressing polycrystalline growth in silicon carbide single crystal growth, there is an effect that the wafer yield and quality of the silicon carbide single crystal ingot can be improved.

Claims (1)

In the sawtooth focusing tube applied when the silicon carbide single crystal is grown by sublimation, a rectangular grooved focusing unit focusing the source gas moving to the seed crystal surface, and a seating unit where the sawtooth focusing tube is seated inside the crucible; Serrated focusing tube, characterized in that it comprises a passage for moving the source gas of the inner wall of the crucible to the seed crystal

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