JPH0534317B2 - - Google Patents

Description

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

The purpose of the present invention is to obtain a high quality single crystal.

Other objects of the invention are to facilitate automation of the device;
The goal is 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, since the Bernoulli method uses hydrogen gas, there are safety issues, 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 part 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 light from the halogen lamp is focused onto the center of the quartz tube 3 by the spheroidal mirror 1. At this time, atmospheric gas is simultaneously introduced from the gas inlet 4 and exhausted from the gas outlet 5. Note that air is normally used as the atmospheric gas, but depending on the material, argon,
Nitrogen, carbon monoxide, carbon dioxide, hydrogen, etc. are used.

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 rotated in the same direction or in opposite directions, and the upper and lower shafts simultaneously move downward to grow crystals.

Until now, in crystal growth using the FZ method, no control has been carried out to keep the crystal diameter constant, and only the lamp power has been controlled or the height of the molten zone has been controlled while visually observing the state of the molten zone. I was adjusting.

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 eliminates this drawback, and by making the part of the spheroidal mirror that faces the screen non-reflective, it is possible to eliminate the lamp image and increase the contrast ratio between the growing crystal and the back. As a result, the 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 adjusted to the temperature of the melt or the height of the melt. By feedback, a single crystal with an extremely stable outer diameter was obtained.

Hereinafter, the present invention will be explained in more detail 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. be.

As the camera section 22, either a license sensor or an area sensor such as a video camera can be used, but if high resolution is required, a line sensor is used.

The controller section 25 processes the image from the camera section 22 only when it receives the signal from the timing section 23. Since the cross section of the crystal is not a perfect circle but approximately elliptical, 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 sent to the 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 adjust the gap and adjust the height of the melt.

Note that the lamp power and gap are fed back to the controller 25 via the AD converter 27.

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 unit 29 prints out each constant of the PID, the crystal diameter at that time, etc. at predetermined intervals.

FIG. 3 shows the state of the image projected on the screen in the conventional device.

Here, 41 is a raw material rod, 42 is a grown crystal, 43
is a melting zone, and 44 is an image of a lamp.

In conventional FZ devices, the entire inside of the spheroidal mirror is plated with gold, so the lamp image of the part of the spheroidal mirror facing the screen is projected on the screen, and the contrast ratio between the crystal and the back is improved. This has placed a heavy burden on signal processing in the controller section 25.

Therefore, as shown in FIG.
3, and the image of the lamp 54 is placed on the quartz tube 5.
5 and the lens 56 to prevent it from being projected on the screen.

FIG. 5 shows how the crystal diameter was measured at this time.

Here, 61 is a raw material rod, 62 is a grown crystal, 63
is the melting zone. Now, if the crystal diameter measurement part is A-A' (a part 0.5 to 5 mm above the solid-liquid interface), the control accuracy of the crystal diameter was conventionally around 10 mm ±0.5 mm by visual inspection, but it is ±0.05 mm. At the same time, melt sag is controlled within
Breakage in the molten zone was prevented, making extremely stable crystal growth possible. Moreover, when the crystal diameter changes,
Although color unevenness and bubbles were likely to occur, which caused problems in terms of quality, these defects were eliminated and a single crystal of extremely high quality was obtained. Furthermore, compared to the case where no antireflection plate is attached, the calculation processing of the controller section is reduced, and it is now possible to perform sufficient control with an inexpensive system. Furthermore, visual monitoring shows 3 to 5
The processing of the stand was difficult, but according to the present invention, 20
It became possible to monitor up to 30 units at the same time, making a major contribution to lowering the price of single crystals.

In this embodiment, an example was explained in which an anti-reflection plate was attached as a means to make a part of the spheroidal mirror non-reflective, but it is also possible to use a method such as making the same part matte. The case also showed similar effects. Furthermore, although the case where a line sensor is used in the camera section has been illustrated and explained, similar effects were also shown when an area sensor was used.

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]

Figure 1 shows an overview of the FZ method. FIG. 2 shows a block diagram of a manufacturing system according to the invention. Third
The figure shows the situation of an image projected on a screen in a conventional device. FIG. 4 shows a plan view of the device according to the invention. FIG. 5 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 the floating zone method, in which crystals are deposited on the seed crystal by moving the floating zone at a constant speed, the lamp is With the image erased and the contrast ratio between the growing crystal and the back side increased, a rotation synchronization signal is extracted from the shaft on which the seed crystal is set, and the diameter of a predetermined portion of the crystal is measured using an optical detection method. A method for producing a single crystal, characterized in that the diameter of a grown crystal is controlled by feeding this back to the temperature of the melt or the height of the melt.