JPS61291485A - Single crystal growth apparatus - Google Patents

Abstract

PURPOSE:To stabilize pulling up conditions and pull up a large-diameter single crystal of good quality having a high melting point, by mounting reinforcing beads in the longitudinal direction on the surface of a heat reflecting plate in a single crystal growth apparatus. CONSTITUTION:A single crystal growth apparatus for pulling up a single crystal from a crystal melt in a crucible with a seed crystal. An almost domed metal heat reflecting plate 1 having reinforcing beads 6 in the longitudinal direction on the surface thereof is applied above the crucible. The above-mentioned beads 6 having a thickness of twice or more based on the thickness of the metal of the body and a width of twice or more thereof are effective. The number of the beads 6 is preferably 4 or more in symmetry.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a crystal growth apparatus using a pulling method, and particularly to a heat reflecting plate for a high frequency heating furnace.

[Technical background of the invention and its problems]

When producing a single crystal with a high melting point by the pulling method (Czochralskiy method), a high-frequency heating furnace is often used. In this case, the quality of the crystals obtained is greatly influenced by the temperature distribution at the solid-liquid interface of the crucible.

Typical high-frequency furnaces have large temperature gradients; pulled single crystals tend to break or develop cracks during cooling. As a countermeasure against this problem, a rice heat reflecting plate has conventionally been used on the crucible.

The heat reflecting plate used has a cylindrical shape as shown in FIG. 1 or a truncated conical tube as shown in FIG. 2. However, in the case of a high-frequency heating furnace with a frequency of 1001 d or more, high-frequency eddy current flows through the heat reflector in these closed circuit heat reflectors, making it too effective as an after-heater, and even cracking the heat reflector. Frequent accidents occurred, making the conditions for raising the ship unstable.

in particular (1) Heat radiation from the seed crystal deteriorates.

(2) Long seed crystals are required because the seed crystals dissolve easily.

(3) The temperature on the surface of the melt becomes higher than the temperature of the melt.

There were many inconveniences such as: Further, in the case of a cylindrical heat reflecting plate, the temperature gradient in the radial direction is larger than the temperature gradient in the longitudinal direction in the case of a large-diameter crystal, so that no improvement is achieved by the extra p.

On the other hand, as shown in Figure 3, heat reflecting plates that are approximately dome-shaped and have an open circuit are also used, but in this case, the mechanical strength of the open part is weakened, so expensive precious metals are used. There were drawbacks such as the need to make the heat reflecting plate thicker.

Furthermore, increasing the thickness also worsens heat dissipation, making it difficult to improve heat distribution compared to conventional methods.

Furthermore, recently, single-inverter type oscillators have been used, and the frequency has become lower and loose heat reflectors have been used, but in this case too, the stiffness of the heat reflectors is weak and the pulling conditions are It had the disadvantage of deterioration.

[Purpose of the invention]

The purpose of the present invention was made in view of the above-mentioned points, and it is an object of the present invention to provide a single crystal growth apparatus capable of pulling a high-quality, high-melting-point, large-diameter single crystal in order to improve a heat reflecting plate. be.

[Summary of the invention]

The present invention relates to a crystal growth apparatus that uses a high-frequency heating furnace to pull up crystals in a crucible, and is equipped with a substantially dome-shaped metal heat reflecting plate on the crucible. It is characterized by having longitudinal reinforcing beads on the surface.

[Embodiments of the invention]

In order to achieve the above object, the present invention provides a bead as shown in FIG. 4, thereby making the pulling conditions more stable than in the past. Table 1 shows a comparison between the conventional type and the embodiment of the present invention.

(Margins below) Table 1 The shape of the present invention was effective in either figures a or b of Fig. 5. It would be effective if the bead was at least twice as thick as the metal of the main body, and at least twice as wide. It will be effective if the number of beads is symmetrically placed in four or more places. It was effective to insert it vertically as shown in Figure 4.

The slit width may be 20 m5 or less.

[Comparative Example 1] An oscillator with an oscillation frequency of 120 KHz was used, and a heat reflector was used for Pi-R, h30% 0.5 of the type shown in Fig. 3.
A 3'×1004 L 1Ta03 single crystal was continuously pulled. The results showed that the heat reflector deteriorated after 40 pullings, and in severe cases it rarely came into contact with the single crystal and cracked. The pulling yield was also 75%.

[Example 1] Using an oscillator with an oscillation frequency of 120 KHz, Pt-Rh 30% 0.5 in the shape shown in Fig. 4, etc.) was symmetrically placed on a heat reflector at four locations with a thickness four times the thickness of the heat reflector. Width 10 in thickness
Use one with 5 beads of 11I+, and use LiTaO
3 single crystals were pulled 3′×100L continuously.

As a result, the pulling conditions continued stably up to 60 times. The pulling yield up to 60 times was as good as 90%.

[Comparative Example 2] Using an oscillator with an oscillation frequency of 7 KHz, LiTaO33'
When the crystal was pulled up 50 times, deterioration of the heat reflecting plate was observed, and the crystal could no longer be removed from the heat reflecting plate due to deformation. The pulling yield was also poor at 85%.

[Example 2] An oscillator with an oscillation frequency of 7 KHz was used, a Pt-Rh 30% 0.51 heat reflecting plate of the type shown in Fig. 4(a) was used, and L
A 3′×100L pull-up of 1Ta03 was carried out. The results showed that the pulling was stable even after 80 uses, and the pulling yield was 92.
It was very good.

〔Effect of the invention〕

According to the present invention, by attaching beads or slits to the heat reflection plate of a single crystal growth apparatus, it is possible to stabilize pulling conditions, and furthermore, to reduce the thickness of the heat reflection plate and repair costs. It becomes possible.

It was also found that high-frequency heating at a frequency of ~10 KHz is effective.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing a conventional single crystal growth apparatus;
FIG. 3 is a diagram showing a partially open hemispherical heat reflecting plate, FIG. 4 is a diagram showing a beaded heat reflecting plate according to the present invention, and FIG. 5 is a diagram showing the shape of the bead according to the present invention. be. 1... Heat reflecting plate 2... Crucible 4... Single crystal 6... Bead agent Patent attorney Nori Chika
Kensuke (and 1 other person) Figure 1 Figure 2 Figure 3 (a) Figure 4 (0L) Figure 5

Claims (4)

[Claims] (1) A crystal growth apparatus that uses a high-frequency heating furnace to pull a single crystal from a crystal melt in a crucible with a seed crystal, and is equipped with a substantially dome-shaped metal heat reflecting plate on the crucible, A single crystal growth device characterized in that the surface of the heat reflecting plate has a reinforcing bead in the vertical direction. (2) The dome-shaped heat reflecting plate has a vertical width of 20 mm.
A single crystal growth apparatus according to claim 1, characterized in that it has the following slits. (3) The single crystal growth apparatus according to claim 1, wherein the single crystal is a LiTaO_3 single crystal. (4) The single crystal growth apparatus according to claim 1, wherein the single crystal is a LiNbO_3 single crystal.