JPS61151087A - Thin film structure for zone melting - Google Patents

Abstract

PURPOSE:To prevent the formation of spheres of the molten liquid of an oxide thin film in the growth of single crystal, by applying the oxide thin film to effect the growth of single crystal, a specific metallic thin film and the second oxide thin film in the order to a substrate. CONSTITUTION:A substrate is coated with the first oxide thin film for the growth of single crystal and composed of a material different from the material of the substrate, a metallic thin film formed on the first oxide thin film and having higher melting point than the first oxide thin film, and the second oxide thin film formed on the metallic thin film and resistant to decomposition at the melting point of the first oxide thin film. The metallic thin film is selected to prevent the reaction of the oxide thin film for the single crystal growth with the oxide thin film for the improvement of the heating efficiency. The metallic material is a material having high melting point, e.g. Ir, Pt, Mo, etc., when the oxide thin film to effect the growth of single crystal is garnet, etc., and the oxide thin film to improve the heating efficiency is e.g. Al2O3, SiO2, ZrO2, etc.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a thin film structure for a zone melting method;
In particular, the present invention relates to a thin film structure for zone melting, which is suitable for forming oxide single crystal thin films on substrates made of different materials.

[Background of the invention]

S O such as amorphous Sin, preparation of Si single crystal thin film on top, etc.
BACKGROUND ART A technology for forming single crystal thin films on substrates made of different materials, typified by Silicon on In5ulator (I) technology, is one of the fundamental technologies for the development of new electronic devices. One of the SOI technologies is zone melting of thin films using laser light, etc.
.

H, Ta+mura and T, Tokuyau
+a, Jpn, J, Appl, Phys, 19°L23
(1980)], this zone melting method has the advantage that a single crystal thin film with a wide area can be obtained without requiring a seed crystal. Zone melting is also used when a seed crystal is not required or when the substrate material cannot be used as a seed crystal, such as when forming a single crystal thin film of a functional oxide material used as an optical isolator on a dissimilar substrate. law is appropriate. However, since a thin film with a thickness of several micrometers or less is melted, the melt becomes spherical, and there is a problem that the melt zone is easily interrupted. In particular, in the case of oxide melt, the surface tension is large, and the melt tends to become spherical on a substrate with poor wetting. SiC2 or Si,N
, a thin film (called a cap) is formed to prevent the molten Si from becoming spherical (Z, A, Weinberg, V
,R,Delins,T,0. Sedgwick, S.
A.

Cohen, C.F., A11otta, and G.J.
, C1ark: Appl, Phys.

Lett, 43.1105 (1983)).

In other words, when a Si thin film is single crystallized by the zone melting method using laser light, etc., the cap used to prevent the melt from becoming spheroidal transmits the laser light and is stable at the melting point of Si (1412°C). , and the material must not react with Si. In the case of Si, since an argon laser (wavelength: 0.6943 μm) is usually used for heating, SiO is suitable as the cap material.

However, in zone melting of oxide thin films, Sin
, cannot be used as a cap material. That is, since many oxides have high melting points, laser light is suitable as a heating and melting means, and a CO□ laser is used to heat materials that are transparent to visible light. When heating oxide thin film material with CO, laser (wavelength 10.6 μm),
S i O, in addition to absorbing laser light, reacts with oxides, so it could not be used as a cap material in the zone melting method.

[Purpose of the invention]

An object of the present invention is to provide a thin film that can stably prevent a melt of an oxide thin film from becoming spheroidal when an oxide thin film formed on a different material is single-crystallized by a zone melting method. It's about providing structure.

[Summary of the invention]

Heating experiments and phase diagram studies have revealed that metals are the best materials that do not react with molten oxides. However, metals reflect laser light,
There was a problem of low heating efficiency. Therefore, in the present invention, a metal that does not melt even at the melting point of the material and does not oxidize is deposited on the oxide film to be grown as a single crystal.

In order to increase heating efficiency, an oxide thin film was formed on the metal that efficiently absorbed laser light and remained stable until the oxide thin film material for single crystal growth was melted. The metal thin film is an oxide thin film grown as a single crystal, and is selected so as not to react with the oxide thin film used to increase heating efficiency. As the metal material, when the oxide thin film to be grown as a single crystal is garnet or the like, a high melting point material such as iridium, platinum, rheonium, or molybdenum is selected. In addition, as an oxide thin film that increases heating efficiency, A C20, Si o
,, Z r O,.

There are MgAQ204 etc.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

Example 1 As shown in FIG. 1, iridium (I
r) 200n+++ is deposited by vacuum evaporation method, and a 10 μm thin film of neodymium gallium garnet (Nd, Ga, 01
□) 3 was sputter deposited. The sputtering conditions were: RF power: 200W, substrate temperature: water cooling, sputtering gas: Ar(
The pressure was 5 Pa).

Note that the iridium 2 is used to prevent the substrate 1 and the oxide thin film 3 from reacting. However, oxide thin film 3
It is not necessary when growing a single crystal by melting only the upper surface of the crystal. Furthermore, 200n of iridium 4 was added by vacuum evaporation method.
A 50 μm thick AΩ20.5 film, which is an oxide thin film for increasing heating efficiency, was sputter-deposited thereon. The sputtering conditions were the same as those for the deposition of the oxide thin film 3. A thin film having such a structure is irradiated with C0 laser light 6,
Heated. The cross-sectional shape 7 of the laser beam 6 on the film surface was in the shape of two circles with a major axis of 100 μm, as shown in FIG. The output of the laser beam 6 is 32W, and at that time A
The surface temperature of Q, O35 was 1800°C. 2 thin films
It was moved at a speed of 0 km/h.

After heating, AQ, 0.5 and iridium 4 were removed by etching with aqua regia, and the surface of neodymium gallium garnet 3 was etched with phosphoric acid.

Light etching was performed using a 1:1 mixture of sulfuric acid, and the film was evaluated. As a result, the neodymium gallium garnet 3 was polycrystalline, but the width of the strip scanned by the laser beam 6 was 2.
The center portion of 0 μm was made up of large crystal grains, and the length of the crystal grains was 2.3 m. The surface orientation was tilted 7 degrees from (110) to (211). However, when combined with other experimental examples, the rectangular single crystal part with a width of 20 μm and a length of 1 m was left in place, and the other parts were removed using ion milling technology. niB
Y3 Fe s O12 containing i was heated to a high temperature (approximately 6
Perform sputter deposition at 00°C) with RF power: 2
00W, Ar gas: 5Pa), and epitaxial growth was performed. Then, a waveguide type optical isolator was fabricated.

Example 2 Iridium 9 was deposited to a thickness of 200 nm on a sapphire substrate 8 having a plane orientation of (1102) by vacuum evaporation as in Example 2.
On top of this, neodymium gallium garnet with a thickness of 20 μm was sputter-deposited (the sputtering conditions were the same as in Example 1), and using a grid-like photomask with a width of 20 μm, photolithography technology and ion milling technology were used. As shown in FIG. 2, a lattice-shaped neodymium-gallium-garnet film 10 with a width of 20 μm was formed at intervals of 80 μm. On top of this, as in Example 1, an iridium film 11
and AQ, O, film 12 was formed.

The CO2 laser beam was focused on the neodymium gallium garnet grid and scanned under the same conditions as in Example 1. As a result, it was possible to form a single crystal of a portion with a width of 20 μm and a length of 3.2 mm.

Example 3 The thin film structure of this example is shown in FIG.

Platinum 13 is deposited to a thickness of 0.5 μm on a quartz substrate 18, and a thin oxide film of Bii, SiO is grown on top of the platinum 13 as a single crystal.
□. No. 14 was sputter-deposited to a thickness of 20 μm (sputtering conditions were the same as in Example 1). On top of this, platinum 15 was deposited to a thickness of 0.2 μm, and a 5-inch oxide thin film was deposited to further increase heating efficiency.
216 was sputter-deposited to a thickness of 2 μm. A part of such a thin film structure is etched into a strip shape using a reactive ion etching method to form Biyu, Sin, and the like. An opening was made so that 14 was exposed. This part has a film thickness of 50 μm and a plane orientation of (100).
B i iz S i Ox. Seed crystal 17 was placed. A strip heater 19 made of a tungsten wire with a diameter of 0.5 m was placed on the seed crystal 17, heated with electricity, and after confirming that the seed crystal 17 was melted, the quartz substrate 18 was placed on the strip heater 19 at a speed of 6 m/h. I moved it against. During the movement, the current of the strip heater 19 was adjusted so that the surface temperature of the Si0□ 16 was 1020°C. A single crystal thin film having the same plane orientation as the crystal and the seed crystal was obtained with an area of 1010 x 20''.

It should be noted that single-crystal portions could be similarly formed in other oxide thin films such as Ga, Gd, and 01□.

〔Effect of the invention〕

As described above in the Examples, according to the thin film structure of the present invention, the oxide thin film could be made into a single crystal by the laser heating zone melting method without interrupting the melting zone. Single crystallization is also effective even when the heating source is not a laser beam.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the thin film cross-sectional structure and laser light irradiation, Figure 2
The figure shows the external appearance and cross-sectional view of the thin film structure. FIG. 3 is an external view showing the structure of the thin film and the state of heating. 1... Sapphire single crystal substrate, 2... Iridium,
3...Neodymium gallium garnet, 4...
Iridium, 5...AQ, O,,6...laser light,
7... Cross-sectional shape of laser beam 6, 8... Sapphire substrate, 9... Iridium, 10... Neodymium gallium garnet film, 11... Iridium film, 12...
・・AQ□O8 film. 13...Platinum, 1.4...B112Sin2°, 1
5...Platinum, 16...SiO,, 17...Seed crystal, 118...Quartz base f3111D! 2 Kutomi 3 B Procedural Amendment (Method) Showa 64
) to 2

Claims (1)

[Claims] 1. A predetermined substrate and a substrate material formed on the substrate are thin films of different materials, and a first oxide thin film to be grown as a single crystal and a first oxide thin film formed on the first oxide thin film. , having at least a metal thin film having a melting point higher than the melting point of the first oxide thin film, and a second oxide thin film formed on the metal thin film that does not decompose at the melting point of the first oxide thin film. Thin film structure for zone melting method characterized by: