JPH06345589A - Device for growing epitaxially in liquid phase - Google Patents

Abstract

PURPOSE:To fix the growth rate of a single crystal film and obtain a homogeneous single crystal film with a high reproducibility by placing a thermocouple in the hollow hole of a driving shaft and exposing the temp. measuring part on the open end of a supporting rod to control the temp. distribution. CONSTITUTION:The oxides of the elements (Fe2O3, Y2O3) constituting, for example, garnet and a solvent (PbO, B2O3) are filled in a crucible 6. The crucible is placed on a holder 7 and heated to convert the oxides to a homogeneous soln. The soln. is held between a liquidus line and a solidus line to supercool the garnet. A substrate 8 is fixed to a substrate holder 9, the temp. measuring part at the tip of a thermocouple 15 is arranged at the center of the upper surface, and then a rod 11 supporting the holder 9 is lowered into a furnace core tube 1 to preheat the substrate 8. The substrate 8 is dipped in the soln., the temp. is monitored by the thermocouple 15 to form a stabilized temp. region, the dipping depth is fixed, and the substrate is rotated in one direction or the forward and backward directions for a specified time to grow a magnetic garnet single crystal film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for growing a single crystal film on the surface of a base substrate by a liquid phase epitaxial growth method.

[0002]

2. Description of the Related Art Conventionally, magnetic garnet single crystals have been used in magnetostatic wave (MSW) devices such as delay line filters, oscillators, nonlinear devices, and magneto-optical elements such as optical isolators, circulators or switches utilizing the Faraday rotation effect. Widely used. A liquid phase epitaxial growth method is known as a main method for producing the magnetic garnet single crystal.

FIG. 3 shows a schematic sectional view of a conventional liquid phase epitaxial growth apparatus. In the figure, 1 is a vertical cylindrical furnace core tube made of alumina, 2a, 2b and 2c are heaters for resistance heating provided around the furnace core tube 1, and 3 is a furnace body surrounding the furnace core tube 1. Reference numeral 4 is a shutter for suppressing the invasion of air into the furnace core tube 1, 5 is a solution of the raw material of the magnetic garnet film, 6
Is a platinum crucible containing the raw material for the magnetic garnet film, 7
Is a support base for supporting the crucible 6, 8 is a base substrate made of Gd ₃ Ga ₅ O ₁₂ (hereinafter referred to as GGG), 9 is a substrate holder made of platinum or platinum alloy for holding the base substrate 8 horizontally,
Reference numeral 10 is a support rod made of alumina that is driven in the rotation direction and the vertical direction.

The method for growing a single crystal film is as follows.
First, Fe ₂ O ₃ and Y ₂ O ₃ which are oxides of the elements composing the garnet and Pb as a solvent are provided in the platinum crucible 6.
O and B ₂ O ₃ are filled. Next, this crucible 6 is placed on the support 7 in the furnace core tube 1, and then heated and melted at about 1200 ° C. to homogenize. Then, this solution is kept at a temperature between the liquidus and the solidus, that is, a constant temperature of about 900 ° C. to bring the garnet into a supercooled state. Next, the GGG substrate prepared as the base substrate 8 is attached to the substrate holder 9, and the support rod 10 supporting the substrate holder 9 is lowered into the furnace core tube 1 to preheat the base substrate 8. After that, the base substrate 8 is immersed in the raw material solution 5 and is rotated in one direction or forward and reverse at a fixed position for a predetermined time to grow a magnetic garnet single crystal film. Finally, the base substrate 8 is placed above the solution 5.
By rotating at about 500 rpm,
The solution 5 attached to the grown magnetic garnet single crystal film is shaken off.

In the growth of a series of single crystal films, the temperature of the raw material solution is predicted by measuring the temperature distribution with a thermocouple in the absence of the base substrate before growing the single crystal film, and the temperature during the growth is predicted. Is monitored and controlled by a thermocouple (not shown) arranged beside the crucible or at the bottom of the crucible.

[0006]

The temperature of the raw material solution during the growth of the single crystal film fluctuates due to the convection of the solution, and the temperature of the solution around the base substrate is changed by the latent heat generated during the growth on the base substrate. Fluctuates unlike the temperature of the surrounding solution. Also, due to dirt inside the furnace core tube or deterioration of the heating source,
The value does not always show the set value every time.

However, in the conventional liquid phase epitaxial growth apparatus, since the temperature of the raw material solution being grown is indirectly measured by the thermocouple through the crucible, there is a time lag in detecting the temperature fluctuation of the solution. . Therefore, it was unavoidable that the temperature control by feedback was delayed and the temperature fluctuation range of the solution became large. That is, there is a problem that it is difficult to maintain the solution at a constant supercooling degree, and the growth rate changes during the growth to form a single crystal film having poor crystallinity.

Therefore, in order to directly measure the temperature of the raw material solution being grown, for example, a method utilizing light radiation has been studied. However, this method has the drawbacks that the emissivity of the solution is unknown and the temperature cannot be uniquely determined due to various disturbances such as absorption in the air and differences in the reflectance due to contamination in the furnace core tube. ing.

Therefore, an object of the present invention is to accurately monitor the temperature of the solution of the raw material during the growth and feed it back to keep the temperature of the solution constant so as to obtain a uniform single crystal under a constant supercooling degree. An object is to provide a liquid phase epitaxial growth apparatus capable of growing a film.

[0010]

In order to achieve the above object, the present invention provides a container inside a vertical tube-shaped furnace core tube, and heats the furnace core tube with a heater to form a single container inside the container. In a device for dissolving a crystal raw material, immersing a base substrate in this solution, and growing a single crystal film on the surface of the base substrate by a liquid phase epitaxial growth method, the single crystal film growth device is:
A hollow elongated support rod for supporting the underlying substrate, a hollow elongated drive shaft connected to the support rod for rotating and vertically moving the support rod, a slip ring fixed to the drive shaft, and the support. It has a thermocouple inserted in the hollow hole of the rod and the hollow hole of the drive shaft, the temperature measuring portion of the thermocouple is exposed at the open end of the supporting rod, and the other end is connected to a measuring instrument via a slip ring. It is characterized by being.

[0011]

The liquid phase epitaxial growth apparatus of the present invention can directly measure the temperature of the raw material solution during the growth of the single crystal film by the thermocouple.

Therefore, the temperature variation of the solution of the raw material can be immediately detected, and the temperature is controlled by feeding back the variation, whereby the variation of the temperature of the solution can be minimized. As a result, it is possible to suppress variations in the growth rate of the single crystal film. Also, by arranging multiple thermocouples in the center and the peripheral part of the base substrate, it is possible to know the temperature distribution in the base substrate. Based on this, the base substrate is immersed in the position of uniform temperature distribution. A single crystal film can be grown. As a result, it is possible to suppress variations in the growth rate within the base substrate.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a schematic structure of a liquid phase epitaxial growth apparatus according to this example. In the figure, 1
Reference numeral 1 is a hollow support rod made of alumina that is driven in the rotational direction or up and down, 12 is a hollow drive shaft, 13 is a chuck holder that connects the support rod 11 and the drive shaft 12, and 14 is a drive device. A mechanism that does not move and that rotates and vertically drives the drive shaft 12 is provided inside. Reference numeral 15 is a thermocouple, and the temperature measuring portion at the tip thereof is arranged on the surface of the base substrate 8 and then inserted into the support rod 11 and the drive shaft 12. Reference numerals 16a, 16b and 16c are a pair of slip rings for taking out an electromotive force signal from the thermocouple 15 in the rotating drive shaft, 16a is a rotor rotating in synchronization with the drive shaft, and 16b is a rotor 16a and a contact from the rotor 16a A stator 16c for taking out an electromotive force signal, and a stationary support portion 16c for supporting the stator 16b. Further, 17 is a digital voltmeter that monitors an electromotive force signal, 18 is a heating control device that controls each of the heaters 2a, 2b, and 2c of the heating furnace, and 19 is a drive device 14 based on the monitored electromotive force signal, that is, temperature. It is a computer that controls the heating control device 18. Since other parts are the same as the conventional ones, the same numbers are given and the description thereof is omitted.

Next, the operation of the liquid phase epitaxial growth apparatus having the above structure will be described by taking the case of growing a garnet single crystal film as an example.

First, a platinum crucible 6 is filled with Fe ₂ O _{3 and} Y ₂ O ₃ which are oxides of elements constituting garnet and PbO and B ₂ O ₃ as solvents. Next, this crucible 6
After being placed on the support base 7, it is heated to about 1200 ° C. to form a solution and homogenize. Then, this solution is kept at a temperature between the liquidus and the solidus, that is, a constant temperature of about 900 ° C. to bring the garnet into a supercooled state. Next, the substrate holder 9
The GGG substrate prepared as the base substrate 8 is attached to the base substrate 8, the temperature measuring portion at the tip of the thermocouple 15 is arranged at the center of the upper surface of the base substrate 8, and then the supporting rod 10 for supporting the substrate holder 9 is attached to the furnace core tube 1. To preheat the base substrate 8. Then, while immersing the base substrate 8 in the raw material solution 5, the temperature is monitored by a thermocouple to fix the immersion depth in a stable temperature range, and then the garnet is rotated in one direction or in the reverse direction for a predetermined time. Growing a single crystal film. Finally, solution 5
The underlying substrate 8 is rotated at a rotation speed of about 500 rpm above the substrate to shake off the solution 5 adhering to the grown magnetic garnet single crystal film. During the growth of this single crystal film, the temperature of the raw material solution 5 is continuously monitored and input to a computer, and based on this value, arithmetic processing is performed and feedback is given to the drive device 14 and the heating control device 18.

Table 1 shows the film for each growth time when the magnetic garnet single crystal film was produced by the conventional liquid phase epitaxial growth apparatus and when the magnetic garnet single crystal film was produced by the liquid phase epitaxial growth apparatus of the present invention. This is a comparison between the thickness and the grown film thickness distribution on the surface of the underlying substrate. The in-plane film thickness distribution shows the value after 120 minutes of growth, and the peripheral part shows the average of the values at four peripheral positions on the surface of the underlying substrate.

As is clear from Table 1, according to the liquid phase epitaxial growth apparatus of the present invention, the temperature of the solution of the raw material during the growth is directly monitored and the feedback control is performed by the computer to the growth conditions. The growth rate of the single crystal film becomes constant.

[0018]

[Table 1]

In the above embodiment, the thermocouple 15
One is arranged at the center of the upper surface of the base substrate 8, but the present invention is not limited to this, and a plurality of thermocouples can be arranged to monitor the temperature distribution on the base substrate. FIG. 2 shows an example of arranging a total of five thermocouples, one at the center of the base substrate and four at the periphery, to monitor the temperature of the center and the periphery of the base substrate.

Further, although the magnetic garnet single crystal film has been described in the above embodiment, the present invention is not limited to this, and for example, liquid crystal epitaxial growth of single crystal lithium niobate such as an optical device is possible. Also, the device of the present invention can be applied.

[0021]

As is apparent from the above description, according to the liquid phase epitaxial growth apparatus of the present invention, the temperature of the raw material solution can be directly measured by the thermocouple during the growth of the single crystal film. Therefore, it is possible to immediately detect a change in the temperature of the solution of the raw material, and by feeding back the temperature to control the temperature, it is possible to minimize the change in the temperature of the solution. Also,
By arranging multiple thermocouples in the central part and the peripheral part of the base substrate, the temperature distribution on the base substrate can be known, and the base substrate is immersed in a position where the temperature distribution is uniform to grow a single crystal film. be able to.

Therefore, the growth rate of the single crystal film becomes constant under a constant degree of supercooling of the raw material solution during the growth of the single crystal film, and a uniform single crystal film can be obtained with good reproducibility.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of a liquid phase epitaxial growth apparatus of the present invention.

FIG. 2 is a perspective view showing an arrangement example with five thermocouples.

FIG. 3 is a schematic sectional view of a conventional liquid phase epitaxial growth apparatus.

[Explanation of symbols]

 1 furnace core tube 2a, 2b, 2c heater 3 furnace body 5 raw material solution 6 crucible 8 base substrate 9 substrate holder 11 support rod 12 drive shaft 13 chuck holder 14 drive device 15 thermocouple 16a slip ring rotor 16b slip ring Stator 17 Digital voltmeter 18 Heating controller 19 Computer

Claims (1)

[Claims] 1. A container is placed inside a vertical cylindrical furnace core tube, and the furnace core tube is heated by a heater to dissolve the single crystal raw material in the container, and the base substrate is immersed in this solution. In a device for growing a single crystal film on a surface of a base substrate by a liquid phase epitaxial growth method, the single crystal film growth device comprises a hollow elongated support rod for supporting the base substrate and the support rod connected to the support rod. A hollow elongated drive shaft for rotating and vertically driving the rod, a slip ring fixed to the drive shaft, a hollow hole of the support rod and a thermocouple inserted through the hollow hole of the drive shaft, The liquid phase epitaxial growth apparatus, wherein a temperature measuring portion of the thermocouple is exposed at an opening end of the support rod and the other end is connected to a measuring instrument via a slip ring.