JPH0534318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel single crystal manufacturing method using the FZ method.

An object of the present invention is to obtain high-quality single crystals by stably growing crystals.

Another object of the invention is to facilitate automation of the apparatus and to obtain inexpensive single crystals.

Conventionally, the Bernoulli method and the pulling method are known as single crystal manufacturing methods using the melt method. However, the Bernoulli method has safety problems because it uses hydrogen gas, and the pulling method requires an expensive crucible and has problems such as concerns about contamination.

Therefore, the FZ method is attracting attention because it does not require a crucible, there is no need to worry about contamination, and it does not require the use of dangerous gases.

Figure 1 shows an overview of the FZ method.

Here, 1 is a spheroidal mirror, 2 is a halogen lamp, 3 is a quartz tube, 4 is a gas inlet, 5 is a gas outlet, 6 is a raw material rod, 7 is a seed crystal, 8 is a molten zone, and 9 is an upper shaft , 10 is a lower shaft.

A raw material rod 6 is set on the upper shaft 9, and a seed crystal 7 is set on the lower shaft 10.

The power of the halogen lamp 2 is increased, and the spheroidal mirror 1 focuses the light from the halogen lamp onto the center of the quartz tube 3. At this time, the gas inlet 4
Atmospheric gas is introduced from the gas outlet port 5, and the atmospheric gas is exhausted from the gas outlet port 5. Note that air is normally used as the atmospheric gas, but argon, nitrogen, carbon monoxide, carbon dioxide, water, etc. may be used depending on the material.

In the light condensing section, the tip of the raw material rod 6 and the tip of the seed crystal 7 are brought into molten contact to form a molten zone 8.
At this time, the upper shaft 9 and the lower shaft 10 are
Crystals are grown by rotating in the same or opposite directions and moving the upper and lower shafts simultaneously.

Until now, in crystal growth using the FZ method, there has been no control to maintain a constant crystal diameter, and the only method has been to control the lamp power or adjust the height of the molten zone while visually observing the state of the molten zone. Was.

As a result, the outer diameter of the crystal fluctuates, and in extreme cases, the melt sag or breakage occurs in the molten zone, making it impossible to obtain a high-quality single crystal.

Furthermore, the number of devices that one person can monitor is limited, and the cost of crystals has become expensive.

The present invention aims to eliminate such drawbacks by extracting a rotation synchronization signal from a shaft on which a seed crystal is set, measuring the diameter of a predetermined portion of the crystal using an optical detection method, and determining the temperature of the melt or the diameter of a predetermined portion of the crystal. By feedback to the height of , a single crystal with an extremely stable outer diameter was obtained.

The present invention will be explained in more detail below with reference to Examples.

Embodiment 1 FIG. 2 shows a block diagram of a system based on the present invention.

Here, 21 is an optical system, 22 is a camera section, 23 is a timing section, 24 is a key input section, 25 is a controller section, 26 is a DA converter, 27 is an AD converter, 28 is a display section, 29 is a printer section, 30 is a lamp power control section, and 31 is a gap adjustment section.

Although a line sensor or a video camera can be used as the camera section 22, a line sensor is used when high resolution is required.

The controller section 25 processes the image from the camera section 22 only when it receives the signal from the timing section 23. This is because, as shown in FIG. 3, the cross section of the crystal is not a perfect circle but almost an ellipse, so a rotation synchronization signal is extracted from the lower shaft 10 and the diameter of a predetermined portion of the crystal is measured.

The signal processed by the controller section 25 is DA
After passing through the converter 26, a lamp power control unit 30 adjusts the lamp power and controls the temperature of the melt. Alternatively, the gap adjustment 31 is used to perform gap adjustment to adjust the height of the melt.

Note that the lamp power and gap are determined by AD converter 2.
7, the feedback is sent back to the controller 25 again.

On the other hand, the key input section 24 inputs various initial constants, and the display section 28 displays the lamp power and the like at that time. Further, the printer section 29 prints out various constants of the PID, the crystal diameter at that time, etc. at predetermined intervals.

Figure 4 shows how the crystal diameter was measured.

Here, 41 is a raw material rod, 42 is a grown crystal, and 43 is a molten zone. Now, let the crystal diameter measurement part be A-A'. (Select a location 0.5 to 5 mm above the solid-liquid interface.) Then, conventional visual inspection would not be able to control the crystal diameter accurately.
What used to be around 10 mm ±0.5 mm was controlled to within ±0.05 mm, and at the same time, it was possible to prevent melt dripping and breakage in the molten zone, making it possible to grow extremely stable crystals.

Moreover, when the crystal diameter varied, color unevenness and bubbles were likely to occur, which was a problem in terms of quality, but these defects were eliminated and a single crystal of extremely high quality was obtained.

Furthermore, conventional visual monitoring required only 3 to 5 units, but the present invention makes it possible to monitor 2.0 to 30 units at the same time, greatly contributing to lowering the price of single crystals.

As detailed above, the present invention can be applied not only to gemstone single crystals such as ruby, sapphire, and alexandrite, but also to industrial single crystals such as YIG, YAG, and GGG, and provides high-quality and inexpensive single crystals. It is something.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of the FZ method. FIG. 2 shows a block diagram of a manufacturing system according to the invention. FIG. 3 is a diagram showing a cross section of the crystal. FIG. 4 is a diagram showing how the crystal diameter is measured according to the present invention.

Claims (1)

[Claims] 1. Light emitted from a high-temperature light source such as a halogen lamp is focused using a reflecting mirror or lens, and in the focusing section, a raw material rod and a seed crystal are combined via a molten zone to form a floating zone. In a floating zone method (hereinafter abbreviated as FZ method) in which crystals are deposited on the seed crystal by moving the floating zone at a constant speed,
A rotation synchronization signal is extracted from the shaft on which the seed crystal is set, the diameter of a predetermined portion of the crystal is measured using an optical detection method, and this is fed back to the temperature or height of the melt to grow the crystal. A method for producing a single crystal, characterized by controlling the diameter of the crystal.