JPH01197385A - Substrate holder - Google Patents

Abstract

PURPOSE:To grow a uniform epitaxial film in a short period of time on both faces of a substrate by using metallic materials consisting of at least >=1 kinds of Pt, Au and Ph to form a planar member having a desired number of through- hole parts and a perpendicular bar shaped part. CONSTITUTION:The desired number of the through-hole parts 1-4 are provided to the planar member 100 formed by using the metallic material consisting of at least one kind selected from the Pt, Au and Rh. The hole parts 1-4 on the front face 101 side of the planar member 100 are formed to the diameter smaller than the diameter of the substrates 200 and claws 103 consisting of the above-mentioned metallic material are welded to the circumference of the hole parts 1-4 on the front face 101 side. The bar-shaped member consisting of the above-mentioned metallic material is perpendicularly welded to the center of the rear face 102 of the planar member 100, by which the substrate holder is obtd. The substrates 200 are mounted in the hole parts 1-4 of the planar member 100 of such substrate holder and are dipped in a flux 22, by which an oxide crystal is epitaxially grown in the liquid phase on both faces of the substrates 200.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a substrate holder, and more particularly to a holder for substrates of oxide crystals, particularly galanet crystals, grown by liquid phase epitaxial growth.

BACKGROUND OF THE INVENTION Oxide epitaxial films are used for various purposes in the fields of optical communication and optical measurement.

In addition, B1-substituted garnet has become more productively produced by using the liquid phase epitaxial method (LPE method) than the conventional flow zone method (FZ method) or flux method, and in recent years it has been used for semiconductors. It is increasingly being applied to optical isolators that suppress reflected return light that causes laser noise.

As a crystal for an optical isolator, it is necessary that the absolute value of the Faraday rotation angle is 1θl=45 degrees. Bi
For substitutional garnet, the wavelength used is 1.3 to 1.56.
In the case of the μm band, it is necessary to obtain crystals with a film thickness of several hundred μm to 1 fl.

Conventionally, a garnet substrate was attached to a substrate holder as shown in FIG. 4, and a growth apparatus as shown in FIG. 6 was used to grow LPE on one or both sides of the substrate.

Problems to be Solved by the Invention When garnet crystals are grown on both sides of a substrate by LPE, the surface of the substrate opposite to the holder (hereinafter referred to as the surface) grows almost flat, whereas the surface of the substrate on the holder side grows almost flat. The problem was that the surface (hereinafter referred to as the back surface) was extremely uneven and the film thickness was not constant.

Since the absolute value 1θ1 of the Faraday rotation angle is proportional to the film thickness, the non-uniformity of the film thickness becomes the non-uniformity of 1θ1. Normally, as a crystal for optical isolators, after growing a film with a slightly thicker layer so that 1θ1 is larger than 45 degrees, polishing is performed to make 1θ1=4
The film thickness is usually adjusted to 5 degrees.

However, when the non-uniformity of the film thickness is large, the film must be grown so that 1θ1 reaches 46 degrees at the thinnest part, which requires a correspondingly longer growth time.

In addition, when growing a multilayered crystal on both sides of a substrate as shown in Japanese Patent Application Laid-Open No. 60-208730, it is difficult to grow the crystals on both sides of the substrate due to non-uniformity of the film thickness, deviation of the temperature characteristics from the designed value, and
This results in variations in characteristics such as a deviation from θl=45 degrees, which poses a practical problem.

Next, when growing only on one side of the substrate, the film thickness grows almost uniformly, but the growth time is about 2 times longer than when growing on both sides of the substrate.
There was a problem in that it required twice as much.

A means to solve problems In order to solve the above problems, the present invention uses platinum and gold.

Made of at least one metal material such as rhodium,
Flat plate member and middle lL? An oxide crystal consisting of a rod-like member extending vertically from the part to the plate-like member, having a desired number of holes passing through the plate-like member, and further having means for fixing a substrate around the holes. This is a substrate holder for liquid phase epitaxial use.

Effect: With such a structure of the present invention, an epitaxial film can be grown uniformly on a substrate in a short time.

Example Embodiments of the present invention will be described using FIGS. 1 to 3.

FIG. 1 is a diagram showing a substrate holder according to the present invention. A platinum disk 1oO with a diameter of 72m and a thickness of 1.611II+,
Hole 1 to hold four 11nch boards 2oo
4 is provided. In order to prevent the substrate 200 from falling, the diameter of holes 1 to 4 on the surface 101 side of the disk is 11 nch.
It is smaller than 0, with a diameter of 21 cm. Connect board 2oo to hole 1~
4, a platinum claw 103 was welded to the disk 1oO, and a platinum h6 of 6 μm 8wsφ was welded to the center of the disk 10o so as to serve as the central axis of rotation, thereby creating a substrate holder. .

The cutouts 1 to 4 of this substrate holder 100 have 11 nch diameter 60 mm.
0 pm thick Ca-Mg-Zr substituted GGG lattice constant a=
12. Attach four substrates 200 of 497 people and use a Pbo-B2O2-Bi2o3 flux 22 as shown in FIG.
FIG. 3 shows the results of growing O12 to about 86 μm on one side and about 170 μm on both sides. The film thickness distribution is shown with the thinnest portion being 0. The variation in film thickness on the surface 201 of the crystal of the substrate 200 is 4 μm as shown in FIG. 3(8), which is approximately the same value as before using the present invention. Next, the variation in film thickness on the back surface 102 is 6 μm as shown in FIG.

Next, (B t YbGd )3F e,
Q.2 was grown to about 360 μm. At this time, the variation in film thickness was within 10 μm on both the front and back surfaces.

The crystal grown through the above steps was divided into four equal parts using a dicing saw, and mirror polished to a thickness accuracy of ±1 μm. As a result, the absolute value of the Faraday rotation angle of each crystal was determined to be 101 = 46 ±
It was possible to set it to 0.7deg. As a result, due to the non-uniformity of the film thickness, the chip size required for the optical isolator (2Tla angle to 6trr!R angle or 2mφ to 6Wlφ
) It became possible to significantly reduce the number of man-hours compared to the case where the thickness was changed between chips and mirror polishing was performed so that 1θl = 4sdeg after cutting.

The reason why a thicker than usual substrate of 600 μm was used in this example was to prevent cracking due to the difference in thermal expansion coefficient between the substrate and the epitaxial film, as shown in Japanese Patent Application No. 62-230129, and (BtGd) 3(FeGa)601
The reason for epitaxially growing two layers of 2 and (BiYbGd)3Fe6012 is to improve the temperature characteristics as a practical optical isolator, as shown in Japanese Patent Application No. 61-299438.

The reason why an epitaxial film with excellent film thickness uniformity can be grown in a short period of time according to the present invention will be explained below. LP
By the E method, the substrate 20 is placed on the substrate holder as shown in FIG.
When epitaxial growth is performed on both sides by attaching 0, the growth is uniform on the front surface 201 because there is nothing to disturb the flow of the melt, whereas on the back surface 202, the flow of the melt is disturbed by the feet 61 of the substrate holder. As a result, the growth becomes non-uniform and unevenness occurs in the thickness of the grown film. Figure 6 shows (G d Ca ) (G a
A MgZr)sO12 (Ca-Mg-Zr substituted GGG) substrate 200 is fixed to a substrate holder as shown in FIG.
12 is a diagram showing the non-uniformity of the film thickness on the front surface 201 and the back surface 202 when grown to about 85 pm on one side and about 170 μm on both sides. The thinnest part is shown as 0. This shows that while the film thickness actually varies by about 5 μm on the front surface, it varies by about 60 μm on the back surface, and there is a large variation in film thickness, especially near the feet of the substrate holder. .

Based on the above, the flow of the melt is hardly disturbed at the tabs 62 on the surface, so the film thickness distribution is small, whereas the flow of the melt is agitated at the feet 61 of the substrate holder, and the flow of the melt is disturbed. It is thought that the distribution of film thickness becomes large because of this. Therefore, in order to reduce the film thickness distribution and to eliminate stirring of the melt by the feet of the substrate holder, it is effective to align the feet of the substrate holder with the center of rotation.

In this embodiment, the material of the substrate holder is platinum, but gold, rhodium, or an alloy containing at least two of these and platinum, which can withstand high temperatures and air atmosphere, may be used.

Effects of the Invention According to the present invention, it is possible to grow an epitaxial film with good uniformity on both the front and back surfaces of the substrate, and the growth time is approximately half that of the case where the epitaxial film is grown on only one side of the substrate. In addition, compared to the conventional method of growing epitaxial films on both sides of a substrate, the uniformity of the film thickness is improved, which reduces the growth time. Especially in the case of a multilayer structure, the number of steps for mirror polishing is significantly reduced, making it easier for the industry. The value is high.

[Brief explanation of the drawing]

FIG. 1 (8) is a cross-sectional view showing how a substrate is grown using a substrate holding plate holder in an embodiment of the present invention, and FIG. 3 (8) and (B) are FIG. 4 is a diagram showing variations in film thickness when using the conventional epitaxial film. 31... Crucible, 22... Fluxing agent, 1o
O... Disk of substrate holder, 101...
Surface of the substrate holder, 102... Back surface of the substrate holder, 103... Claw portion. Name of agent: Patent attorney Toshio Nakao and 1 other person21
- Rutsu Small Figure 2 22- Melting 1 Figure 3 (A) (B) (Unit: μm) Figure 4 Figure 5 ↑ 61 (A) (B) Falcon position: Am

Claims (1)

[Claims] It is made of at least one kind of metal material such as platinum, gold, and rhodium, and consists of a flat member and a rod-like member protruding perpendicularly from the center, and the flat member has a penetrating hole,
A substrate holder having means for fixing a substrate around the hole, and in which liquid phase epitaxial growth of an oxide crystal is performed on the main surface of the substrate.