JPH068236B2 - Single crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a method for growing an oxide single crystal of the present invention, and particularly to a method for separating a single crystal.

(Prior Art) YAG (yttrium-aluminum-garnet) single crystals or Nd: YAG single crystals doped with neodymium are usually grown by the Chokrumaki method. This Nd: Y
The growth of AG single crystal is high temperature (1970 ℃) and long time (300H)
Need to be trained. Therefore, an ultra-stable system is required. In order to meet this requirement, the refractory structure is complicated, the opening is very small, and the crystals are barely visible. When an expert cuts off the growing crystal from the melt, the tail part of the crystal is not visible, so he used his many years of experience to perform the cutting length and the cutting speed according to a preset manual. .

(Problems to be solved by the invention) Performing the disconnection operation by a preset manual is a simple work, but the disconnection speed is very fast. Therefore, the reproducibility of the separation distance must be provided without an automatic stop device. It's difficult. Furthermore, the specifications prepared in advance do not consider the crystal currently being grown. For this reason, the separation distance is made longer than necessary, and when the crystal deviates from the center of heat retention, distortion or the like occurs, resulting in a significant deterioration in quality. In addition, if the distance is short, the motor is not separated, and a load is applied to the rotating portion of the motor, which often causes an accident such as crystal damage or motor damage.

An object of the present invention is to provide a method for separating a crystal during the growth of a single crystal, which solves this problem.

(Means for Solving Problems) In order to achieve the above object, the present invention provides a high-frequency coil equipped with a vacuum thermocouple for measuring supplied power, and a single crystal raw material in a crucible heated by the high-frequency coil. Load cell for measuring the weight of a single crystal grown from the melt, a crystal pulling motor control unit for controlling the growth rate of the single crystal, and the supplied power so that the output signal of the vacuum thermocouple approaches a predetermined value M. And an analog controller for controlling the output voltage of the load cell from the output voltage from the A / D converter to obtain the increasing speed of the weight of the single crystal, and the crystal diameter control means for changing the M according to a predetermined program. in single crystal growing apparatus according to the Czochralski method comprising a, a sets the length L ₀ of the crystal and the crystal diameter R ₀ to advance the target, the weight of the crystals in the growing suitable Calculated between intervals, when the length L of the crystal during growth while controlling the crystal diameter R during the growth has reached the length L ₀ of the target, the crystal diameter R during growth
To L = nR + m (where n is 0.2 to 0.4 and m is 2
˜5) is calculated, and the growing single crystal is pulled at a high speed by L in the crystal pulling motor control unit to separate the grown crystal.

(Operation) The present invention has obtained a method of automatically and ideally separating the Nd: YAG single crystal by the above-described structure and method.

The present inventors have analyzed in detail the change in diameter of the Nd: YAG single crystal grown to perform ideal separation, particularly the relationship between the separation portion R and the interface L after the crystal separation. And various researches were done. As a result, it was found that the interface L of the interface has a proportional relationship of L = 0.2R to 0.4R as in the embodiment of FIG. Further, the interface L changes depending on the transition of the crystal diameter at the time of separation, that is, depending on whether the crystal is in the thickening direction or the thinning direction. This means that L was large in the fattening direction and was small in the thinning direction. From these facts, the length of separation of the crystal during the growth may be l = 0.2R to 0.4R. However, this result was obtained by the grown Nd: YAG single crystal, and actually, a length of several mm is required. The present inventors conducted a number of experiments in order to obtain l = 0.2R to 0.4R + α. As a result, it has been clarified that if α = 2 mm or more, the separation can be completed completely. However, if α is taken longer than necessary, it causes heat shock to the grown crystal and causes distortion. As a result of experiments, α = 2
I confirmed that ~ 5mm is the best. If a personal computer is used, R; l can be calculated at any time, which is an extremely effective means.

As described above, the method for growing a single crystal of the present invention, in particular, the method for separating a crystal according to the present invention can be used to separate a crystal with good reproducibility, and at the same time, an automatic separation can be performed using a personal computer. The utility value is great.

The present invention will be described below with reference to examples.

(Example 1) Ir crucible 2 (85 ^φ × 100 ^h × of the single crystal growth apparatus of FIG. 2)
1.5 ^t) to Nd: 0.8 to YAG single crystal raw material (high purity _{Al 2 O 3, Y 2 O} 3 at
% Nd was doped, and an appropriate amount was weighed and mixed. ) 21
00g was added and a heat-resistant refractory was installed, and it was installed in the center of the high frequency coil 3. According to a command from the personal computer 5, electric power was applied to the high frequency coil 3 by the analog controller 8 and the high frequency oscillator 9 via the D / A converter 7, and the raw material 1 in the crucible 2 was melted. Next, a YAG single crystal (not Nd-doped) was soaked with a seed crystal <111> in the touch fluid, and it was confirmed that the conditions were optimum, and pulling was started. The pulling speed is
The rotation speed was 12 rpm at 0.6 mm / hr. When the crystal reaches 38 ^φ on the way, shoulders are made and then the diameter is controlled to about 14
Raised 0 mm. At this point, the crystal diameter was 36 ^φ . About 16.
After 5 hours the crystals reached the required length of 150 mm. The crystal diameter at this time was 39 ^φ . Approximately 5.6 seconds at a pulling speed of 3 mm / sec (17 m
m) I pulled up. The interface between the grown crystals was about 14 mm, and the quality was at the highest level.

(Example 2) As in Example 1, a single crystal of Nd: YAG was grown. Foster performed shoulder making when crystals 23 ^phi, crystal diameter in the vicinity of the pulling 160mm while similarly the diameter control thereafter was about 25 ^phi. When the diameter required for pulling up by 10 mm was reached, the diameter was ^23φ . The raising was completed at a pulling rate of 3 mm / sec for about 3 seconds (9 mm) to complete the growth. The grown crystal was 6 mm in thickness at the interface, and a high-quality single crystal was obtained as in Example 1.

(Effect of the Invention) According to the present invention, it is possible to grow a high quality single crystal by performing separation according to a grown crystal, which is particularly effective for automatic growth.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a relationship between a crystal diameter at the time of separating a grown crystal, which is a basis of the present invention, and a trigger of an interface, and FIG. 2 shows a single crystal growing apparatus used in the present invention. Fig. In the figure, 1 is an Ir crucible, 2
Is Nd: YAG single crystal, 3 is a high frequency coil, 4 is a load cell,
5 is a personal computer, 6 is an A / D converter, 7 is D
A / A converter, 8 is an analog controller, 9 is a high frequency oscillator, 10 is a vacuum thermocouple, and 11 is a control unit of a crystal pulling motor.

Claims (1)

[Claims] 1. A high frequency coil equipped with a vacuum thermocouple for measuring supplied power, a load cell for measuring the weight of a single crystal grown from a melt of a single crystal raw material in a crucible heated by the high frequency coil, A crystal pulling motor controller for controlling the growth rate of a single crystal, an analog controller for controlling the supplied power so that the output signal of the vacuum thermocouple approaches a predetermined value M, and an output signal of the load cell for A / D.
A single crystal growth apparatus by the Czochralski method, which comprises a crystal diameter control means for obtaining the increasing rate of the weight of the single crystal from the output voltage through the converter and changing the M according to a predetermined program, The crystal diameter R ₀ and the crystal body length L ₀ are set, the weight of the crystal being grown is calculated at appropriate time intervals, and the length of the crystal being grown is controlled while controlling the crystal diameter R being grown. When the length L reaches the target length L ₀ , L = nR + m (where n
Is 0.2 to 0.4, m is 2 to 5), and the single crystal being grown is pulled at a high speed by L in the crystal pulling motor control unit to separate the grown crystal. How to grow.