JPH06316485A - Liquid phase epitaxial growth method - Google Patents

Abstract

PURPOSE:To improve the crystallinity of a grown single crystal film and reduce nonuniformity in film thickness at the time of growing a single crystal film on the surface of a substrate by liq. phase epitaxial growth method by setting a temp. gradient between the upper and lower part of the melt. CONSTITUTION:A substrate is dipped in a crucible in which a single crystal material is melted, epitaxial growth method is conducted for a specified time, and a single crystal thin film is grown on the surface of the substrate by this liq. phase epitaxial growth method as follows. Namely, a temp. gradient is provided so that the temp. of the upper part of the melt 7 is higher than the liq. phase temp., and the temp. of the lower part is lower than the liq. phase temp. The substrate 8 dipped in the melt 7 is gradually lowered to form a single crystal film on the substrate 8 surface.

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

A conventional method for growing a magnetic garnet single crystal by a liquid phase epitaxial growth method is a platinum crucible held in a vertical heating furnace under predetermined conditions, in which PbO and B are used as oxides and solvents of elements constituting garnet. Fill with ₂ O ₃ and homogenize at about 1200 ° C. to melt. next,
After maintaining this melt in a supercooled state, that is, at a temperature near the liquidus line (about 900 ° C.), a Gd ₃ Ga ₅ O ₁₂ (GGG) substrate as a base substrate is placed in the melt. The magnetic garnet single crystal film is grown on the surface of the underlying substrate by immersing and performing epitaxial growth for a predetermined time while reversing or rotating at a fixed position.

[0004]

However, when a garnet single crystal film is grown by the method as described above, the growth rate of the garnet single crystal film is increased immediately after the base substrate is immersed in the melt and at other times. different. That is, the growth rate is high immediately after the immersion in the melt, but the growth rate decreases with the passage of time. Therefore, there is a problem that the crystallinity of the single crystal film at the initial stage of growth is poor, the single crystal film is distorted a lot, and the film thickness becomes nonuniform. Therefore, an object of the present invention is to provide a liquid phase epitaxial growth method capable of improving the crystallinity of a grown single crystal film and reducing the nonuniformity of the film thickness.

[0005]

In order to achieve the above object, the liquid phase epitaxial growth method of the present invention employs a temperature so that the upper part of the melt is higher than the liquidus temperature and the lower part of the melt is lower than the liquidus temperature. A single crystal film is grown on the surface of the base substrate by applying a gradient and gradually lowering the base substrate while being immersed in the melt.

[0006]

When the base substrate is immersed in the melt, the upper part of the melt is higher than the liquidus temperature, so that the single crystal film does not grow epitaxially on the surface of the base substrate. When the underlying substrate is gradually lowered, the underlying substrate eventually reaches a portion below the liquidus temperature, so that a single crystal film is grown on the surface of the underlying substrate. Since the growth of the single crystal film is gradually started after being immersed in the melt as described above, the growth rate becomes almost constant, the crystallinity does not deteriorate as in the conventional case, and the nonuniformity of the film thickness also decreases.

[0007]

EXAMPLE FIG. 1 shows a liquid phase epitaxial growth apparatus for growing a magnetic garnet single crystal film which is an example of the present invention. Inside the vertical cylindrical core tube 1 made of alumina, a platinum crucible 3 having a bottom surface supported by a support 2 is arranged, and the crucible 3 is filled with a raw material of a magnetic garnet single crystal film and a solvent. Has been done. On the outside of the core tube 1, upper, middle,
Lower three-stage resistance heaters 4, 5, 6 are provided, and the crucible 3 is arranged inside the middle heater 5. The crucible 3 in the core tube 1 is heated by the radiant heat of the heaters 4 to 6, the garnet raw material and the solvent are dissolved to form a melt 7, and the atmosphere in the core tube 1 is maintained at a predetermined temperature. The heating method is not limited to the resistance heating method,
An induction heating method may be used.

The melt 7 in the crucible 3 is provided with a temperature gradient such that its upper portion is higher than its liquidus temperature and its lower portion is lower than its liquidus temperature. As a method of giving a temperature gradient, for example, the temperature of the heaters 4, 5, 6 is set so that the heater 4 side is sequentially higher than the heater 6 side, or the crucible 3 is used.
It is possible to use a method in which the heater 5 for heating the above is divided into upper and lower parts so that the current in the upper part is higher than that in the lower part, and further the temperature adjusting member is provided in the crucible 3.

The disk-shaped base substrate 8 is detachably and horizontally held by a substrate holder 9 made of platinum or platinum alloy fixed to the lower end of an alumina support rod 10. The upper end portion of the support rod 10 is connected to a drive device (not shown), and the drive device can drive the support rod 10 in the vertical direction and at the same time reverse the direction. On the upper end of the furnace core tube 1, a shutter 11 made of quartz glass for suppressing invasion of cold air into the furnace is placed, and the support rod 10 is inserted through the center of the shutter 11.

Next, a method for growing a magnetic garnet single crystal film according to the present invention will be described. First, the raw material (Fe ₂ O ₃ , Y ₂ O ₃ ) for the garnet single crystal film and the solvent (PbO, B ₂ O ₃ ) were mixed in the crucible 3 and homogenized at 1200 ° C. to be melted by heating. A temperature gradient was applied to the melt 7 at 940 ° C. higher than the liquidus temperature on the surface of the melt and 890 ° C. below the liquidus temperature at the bottom of the crucible 3, and then the melt 7
Immerse the base substrate 8 made of a GGG substrate in the
Was gradually lowered while reversing at 100 rpm to grow a magnetic garnet single crystal film on the surface of the base substrate 8. After completion of the growth, the base substrate 8 was pulled up from the melt 7 while being rotated at a high speed, and the adhered melt on the magnetic garnet single crystal film was shaken off by centrifugal force to complete the growth.

FIG. 2 shows changes in the growth rate of the single crystal film in the conventional method and changes in the growth rate of the single crystal film in the method of the present invention. As is clear from the figure, in the conventional method, the growth rate is very high in the initial stage of immersion in the melt, and the growth rate decreases with the lapse of the growth time, whereas in the method of the present invention, the growth rate is almost constant. I understand.

Table 1 shows a comparison of crystallinity of single crystal films.
The full width at half maximum of the X-ray rocking curve of the single crystal film of the conventional method and the method of the present invention is shown, and Table 2 shows the change in the film thickness of the single crystal film.

[Table 1]

[0013]

[Table 2]

As is clear from Tables 1 and 2, the single crystal film obtained by the method of the present invention has better crystallinity than the conventional one,
It can be seen that the variation in film thickness is small. Therefore, when this single crystal film is used in a magnetostatic wave device, good characteristics are obtained.

Although the magnetic garnet single crystal has been described in the above embodiments, the present invention is not limited to this, and is also applied to liquid phase epitaxial growth of lithium niobate, which is a single crystal for optical devices, for example. be able to.

[0016]

As is apparent from the above description, according to the present invention, the upper part of the melt is higher than the liquidus temperature and the lower part of the melt is below the liquidus temperature during the liquid phase epitaxial growth. Since a temperature gradient is provided and the underlying substrate being grown is gradually lowered, the growth rate is substantially constant, and a single crystal film having good crystallinity and a uniform film thickness can be manufactured.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a liquid phase epitaxial growth apparatus according to the present invention during immersion.

FIG. 2 is a diagram showing a change in growth rate with time between the method of the present invention and the conventional method.

[Explanation of symbols]

 1 core tube 3 crucible 7 melt 8 base substrate 9 substrate holder 10 support rod

Claims (1)

[Claims] 1. A liquid phase epitaxial growth method for growing a single crystal film on a surface of a base substrate by immersing the base substrate in a crucible in which a single crystal raw material is melted and performing epitaxial growth for a predetermined time. By giving a temperature gradient so that the upper part of the melt is higher than the liquidus temperature and the lower part of the melt is lower than the liquidus temperature, by gradually lowering the underlying substrate while it is immersed in the melt,
A liquid phase epitaxial growth method characterized by growing a single crystal film on the surface of a base substrate.