JPH026395A - Production of liquid epitaxial magnetic garnet thick film - Google Patents

Abstract

PURPOSE:To prevent cracking in grinding caused by the presence of warpage and improve product yield by dividing the subject thick film, grown in one surface of a garnet substrate and having a specific thickness or above and grinding the divided thick film. CONSTITUTION:A magnetic garnet film is grown on one surface of a nonmagnetic garnet substrate so as to provide >=50mu thickness by a liquid epitaxial method. In this case, the substrate and film are warped as shown in the figure by cooling. The resultant film is previously divided, e.g., into 4 parts, as shown in the figure when a substrate of a disc having a diameter of 2 inches and ground to remove the substrate, etc., and afford the objective magnetic garnet film. Thereby, the objective product is obtained in good yield by the above-mentioned method without cracking of the magnetic garnet thick film in an irregular shape due to warpage in a grinding step.

Description

[Detailed description of the invention] [Summary of the invention] Magnetic garnet 1 for magneto-optical elements with a thickness of 50 μm or more grown epitaxially on one side of a garnet substrate by liquid phase epitaxial (LPE) method - The thick film has thermal expansion with the substrate. Because the coefficients are different, it warps significantly at room temperature.

By dividing this warped single-sided film in advance and then polishing it, it became possible to prevent cracking during polishing, which would lead to a decrease in yield.

[Industrial Application Field] The present invention relates to a magneto-optic garnet for use in magneto-optical elements used in optical isolators, optical circulators, etc. that utilize the Faraday rotation effect.

[Prior Art] Semiconductor lasers are widely used as coherent light sources in optical applications and optical communications, but when the light beam emitted from the semiconductor laser is reflected by an optical system and returns to the semiconductor laser, There is a problem that laser oscillation becomes unstable.

In order to deal with this problem, an optical isolator is provided on the optical output side of the semiconductor laser, and an optical path is set so that the light emitted from the semiconductor laser does not return.

A material with a wavelength of 1.1 μm is used as a magneto-optical element material for an optical isolator to separate the light beam emitted from such a semiconductor laser and the reflected light beam by the Faraday rotation effect.
Bulk single crystals of yttrium-iron-garnet (YIG), which have excellent transparency in the zone and above, have been used, but in recent years liquid-phase epitaxial crystals, which have a Faraday rotation coefficient several times larger than that of YIG and can be mass-produced, have been used. (LPE
) method has been reported to produce many bismuth-substituted iron garnet thick films.

In general, magnetic garnet single crystal films are made by combining rare earth elements and iron oxides, which are garnet components, with PbOBi2O, -B,
It is obtained by immersing a non-magnetic garnet substrate in a melt dissolved in a 03-based flux and epitaxially growing on both sides of the substrate.

However, in the case of a magnetic garnet thick film of 50 μm or more, especially a bismuth-substituted magnetic garnet thick film, the present inventors discovered that in the process of taking out a film produced at a high temperature of around 800°C from the furnace and cooling it to room temperature, I learned that there are problems such as cracks appearing and the entire board breaking completely.

In addition, in the case of the single-sided epitaxial method in which only one side of the substrate is brought into contact with the melt surface and magnetic garnet is grown on only one side of the substrate, although the substrate and film warp as shown in Figure 1 by cooling, the film does not crack. Problems such as the substrate being completely broken when the substrate is completely broken have been eliminated, and we have learned that the single-sided epitaxial method is superior to the double-sided epitaxial method in producing a magnetic garnet thick film for magneto-optical elements with a thickness of 50 μm or more.

[Problems to be Solved by the Invention] However, the thick magnetic garnet film with a thickness of 50 μm or more obtained by the single-sided epitaxial method described above cracks in irregular shapes during the polishing process due to warpage. There is a problem that the product yield is reduced.

[Means for Solving the Problems] The present invention produces a magnetic gannet film by growing a magnetic garnet film on a non-magnetic garnet substrate by a liquid phase epitaxial method and polishing the obtained film to remove the substrate. A liquid phase epitaxial magnetic garnet thickness method, characterized in that a magnetic garnet film is grown on one side of a non-magnetic gannet substrate to a thickness of 50 μm or more, and the obtained thick film is divided in advance and then polished. This is a method for manufacturing a membrane.

In the present invention, the thick film is divided so that the divided film does not break during polishing and is larger than the final product. For example, when a 1-inch or 2-inch substrate is used, it is preferable to divide the area into 4 as shown in FIG. 2, and when a 3-inch substrate is used, it is preferable to divide into 9 as shown in FIG.

According to the present invention, by dividing a warped magnetic garnet single-crystal film into predetermined sizes and then polishing them, cracks during polishing can be prevented, and a decrease in product yield can be prevented.

[Example] Next, the present invention will be specifically explained using examples.

Example 1 Using the melt shown in Table 1, a 2-inch diameter (111)
(G d Ca ) 3 (G a M g Z r
) So, 400t, tm thick (TbL) which exhibits a mirror surface by liquid phase epitaxial growth at 820°C for 30 hours on one side of two substrates (lattice constant 12.496).
A magnetic garnet single crystal film having a composition of uBi)sFe5012 could be obtained.

The radius of curvature of this film was 1.5 m, but by removing the substrate by polishing after dividing it into four parts as shown in Figure 2, and adjusting the film thickness by further polishing, a crack with a thickness of 320 ± 5 μm was formed. We were able to obtain four single-crystal thick films each having a size of a quarter of 2 inches.

Comparative Example 1 Under the same conditions as Example 1, 404 μm thick (TbLuB I
) A magnetic garnet single crystal film having a composition of 3F as 0+2 was obtained.

When this film was polished to remove the substrate without dividing it, it was broken into irregular shapes as shown in FIG.

[Effects] According to the present invention, by dividing a single-sided magnetic garnet single-sided film with a thickness of 50 μm or more in advance and then polishing it, irregularly shaped cracks on the substrate during polishing, which lead to a decrease in product yield, can be eliminated. is prevented.

4 are diagrams showing cracks in the polishing process of a 2-inch substrate in Comparative Example 1.

Claims (1)

[Claims] In a method of manufacturing a magnetic garnet film by growing a magnetic garnet film on a non-magnetic garnet substrate by a liquid phase epitaxial method and polishing the obtained film to remove the substrate, the magnetic garnet film is grown on one side of the non-magnetic garnet substrate. A method for producing a liquid phase epitaxial magnetic garnet thick film, which comprises growing a thick film to a thickness of 50 μm or more, dividing the obtained thick film in advance, and then polishing it.