JPH05193937A - Device for forming thin oxide superconducting film on both surfaces of one sheet of substrate - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the previously formed thin oxide superconducting film by coating the specific region of a heater surface with the above device having a substrate holder contg. the heater and a vacuum chamber housing a target holder. CONSTITUTION:The target 4 held on the target holder 5 is irradiated with a laser beam from a laser device 10 via a window 9 of the vacuum chamber 8 by using, for example, a laser vapor deposition device, by which the thin oxide superconducting film is formed on a substrate 2 heated by the heater 1 built in the substrate holder 3. At least the region of the heater 1 surface in direct contact with the substrate 2 held on the thin oxide superconducting film 3 is coated with a shielding member 11 of, for example, thin MgO film stable to the oxide superconducting film. As a result, the thin oxide superconducting film does not react with the heater 1 surface and is not deteriorated even if the thin film loaded on the rear surface and the heater 1 are held in contact with each other at the time of forming the thin oxide superconducting film on the other surface of the substrate already loaded with the thin oxide superconducting film on one surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconducting thin film forming apparatus. More particularly, the present invention relates to the construction of a novel apparatus that can be used to deposit oxide superconducting thin films on both sides of a substrate.

[0002]

2. Description of the Related Art Conventionally known superconducting materials have generally become superconductors only at extremely low temperatures below the liquefying temperature of helium, so that the fields in which they can actually be used have been extremely limited. However, since it was found in 1986 that a complex oxide such as [La, Ba] ₂ CuO ₄ or [La, Sr] ₂ CuO ₄ was a superconducting material having a high critical temperature, Y-Ba-
It was successively confirmed that Cu-O-based or Bi-Sr-Ca-Cu-O-based composite oxides exhibited superconducting properties in an extremely high temperature range. Since this type of superconducting material having a high critical temperature can use inexpensive liquid nitrogen as a cooling medium, the application of superconducting technology is being considered as a practical problem.

Initially, these composite oxide superconducting materials were synthesized as a sintered body by the solid-phase reaction method, but due to the progress of research thereafter, today, a high quality material is obtained by synthesizing them as a thin film. Is becoming available.
In particular, the laser vapor deposition method is the most promising film formation method at present because it can form an oxide thin film exhibiting high superconducting properties without performing post-treatment such as annealing after film formation.

On the other hand, a microwave device is no exception in that a phenomenon peculiar to superconductivity acts advantageously. That is, for example, in a strip line, the attenuation constant due to the conductor resistance increases in proportion to the square root of the frequency. Dielectric loss also increases in proportion to the increase in frequency, but in the recent strip line, the loss of the strip line is mainly due to the resistance of the conductor due to the improvement of the dielectric material, especially in the region of 10 GHz or less. There is. Therefore, reducing the resistance of the conductor layer in the strip line significantly improves the performance of the microwave line.

Further, the strip line can be used not only as a simple transmission line but also as a microwave device such as an inductance element, a filter, a resonator, a delay line or the like by performing appropriate patterning. Therefore, the improvement of the strip line directly leads to the improvement of the characteristics of these microwave devices. Therefore, various microwave devices in which the conductor line is formed of an oxide superconductor have been proposed.

By the way, the microwave transmission line is different from the transmission line for DC or low frequency signals and is composed of a pair of conductors and a dielectric. Although various specific configurations have been proposed, when an oxide superconducting thin film is used as a conductor layer, the substrate that is the base of the thin film is regarded as a dielectric layer, and oxide superconducting thin films are formed on both sides of the substrate. A loading configuration has been proposed. According to such a configuration, by using the oxide superconducting thin film loaded on one surface as a ground conductor and appropriately patterning the oxide superconducting thin film loaded on the other surface, various micro-types as described above can be obtained. Wave devices can be created.

[0007]

However, when an oxide superconducting thin film is formed on both surfaces of a single substrate, the film forming process is sequentially performed on each surface of the substrate. Moreover, there is a problem that the superconducting property of the oxide superconducting thin film is finally deteriorated, and the double-sided structure as described above has not been actually realized.

Therefore, the present invention solves the above-mentioned problems of the prior art, and a method for forming an oxide superconducting thin film exhibiting excellent superconducting properties on both surfaces of a single substrate, in particular,
A novel method capable of forming an oxide superconducting thin film on the other surface of a substrate having one surface already loaded with an oxide superconducting thin film without degrading the previously formed oxide superconducting thin film. Its purpose is to provide.

[0009]

That is, according to the present invention,
In a film forming apparatus for an oxide superconducting thin film, which comprises a substrate holder containing a heater and a vacuum chamber accommodating a target holder for holding a target, a region of the surface of the heater that is in direct contact with at least the substrate held by the substrate holder However, a film forming apparatus for an oxide superconducting thin film is provided, which is characterized in that the oxide superconducting thin film is coated with a stable material.

[0010]

The film forming apparatus for an oxide superconducting thin film according to the present invention comprises:
The main feature is the configuration of the heater built in the substrate holder.

The cause of deterioration of the characteristics of the previously formed oxide superconducting thin film in the conventional apparatus for forming the oxide superconducting thin film on both surfaces of the substrate was examined in detail. It was found that the oxide superconducting thin film already formed was contaminated by the heater used for heating.

That is, in the thin film forming process, the substrate is generally heated by a heater. A heater for heating the substrate is usually incorporated in the substrate holder, and in order to improve the heating efficiency, the substrate and the heater are in close contact with each other. However, it has been found that, in a high temperature environment during film formation, the surface of the heater usually made of stainless steel or the like reacts with the thin film loaded on the back surface of the substrate to deteriorate the characteristics.

Therefore, in the film forming apparatus according to the present invention, by covering the surface of the heater with a material that does not react with the oxide superconducting thin film, the above-mentioned deterioration of the oxide superconducting thin film is effectively prevented. is doing.

The material that can be used for coating the heater is an oxide superconducting thin film so that the material itself does not react with or contaminate the oxide superconducting thin film. On the other hand, it is preferable to be made of a material that is stable even in a high temperature environment. Specifically, Mg
O, it can be exemplified SrTiO _3, ZrO ₂ or the like.

The structure of the apparatus according to the present invention as described above is as follows:
In addition to the laser vapor deposition method, it can be applied to an apparatus for carrying out various film forming methods such as a sputtering method, a vacuum vapor deposition method and an ion plating method.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a specific example of the structure of a film forming apparatus according to the present invention.

As shown in the figure, this apparatus is basically a laser vapor deposition apparatus, and includes a substrate holder 3 which contains a heater 1 and holds a substrate 2, and a target holder 5 which holds a target 4. The target 4 can be irradiated with laser light through a vacuum chamber 8 that is housed and equipped with an exhaust unit 6 and an air supply unit 7, and an optically transparent window 9 provided in the vacuum chamber 8. A laser device 10 arranged outside the vacuum chamber 8 is provided. Furthermore, in this film forming apparatus, the surface of the heater 1 built in the substrate holder 3 is
It is covered with an O thin film 11.

In the film forming apparatus constructed as described above, since the surface of the heater 1 is covered with the MgO thin film 11 having a thickness of 10 μm, the oxide superconducting thin film loaded on the back surface of the substrate and the heater are not separated from each other. The oxide superconducting thin film does not deteriorate even if the film forming process is performed in the contact state.

[Manufacturing Example] Using the apparatus shown in FIG.
A Y ₁ Ba ₂ Cu ₃ O _7-x thin film was formed on both surfaces of _one substrate.
An MgO (100) substrate was used as the substrate.

Prior to the formation of the oxide superconducting thin film, 1 ×
The film-forming surface of the substrate was cleaned by treating it at 750 ° C. for 10 minutes under a vacuum of 10 ⁻⁶ Torr. Then, a Y ₁ Ba ₂ Cu ₃ O _7-x thin film was formed on _one surface of the substrate by a laser deposition method. The film forming conditions were as shown in Table 1 below.

[0022]

[Table 1]

Subsequently, the substrate 2 was turned upside down and set on a substrate holder, and then a Y ₁ Ba ₂ Cu ₃ O _7-x thin film was formed under the same film forming conditions.

Further, a sample for comparison was prepared by using an ordinary film forming apparatus in which the heater was not coated. The materials used and the film forming conditions were exactly the same as those in the above-described preparation example.

The characteristics of the oxide superconducting thin films on the front and back sides of the pair of samples produced as described above were measured. The measurement results are shown in Table 2. In Table 2, "Table"
Means an oxide superconducting thin film formed earlier, and "back" means an oxide superconducting thin film formed later.

[0026]

[Table 2]

As can be seen from Table 2, in the oxide superconducting thin film formed by using the film forming apparatus according to the present invention, the characteristics of the thin film shown in the table and the film formed later are formed. The characteristics of the back thin film are almost the same.

[0028]

As described above, if the film forming apparatus according to the present invention is used, an oxide superconducting thin film having uniform characteristics can be formed on the front and back of one substrate. Such an oxide superconducting thin film can be used as a material for various microwave devices by regarding the substrate as a dielectric layer.

[Brief description of drawings]

FIG. 1 is a diagram showing a specific configuration example of a film forming apparatus according to the present invention.

[Explanation of symbols]

1 ... Heater, 2 ... Substrate, 3 ... Substrate holder, 4 ... Target, 5 ... Target holder, 6 ... Exhaust means, 7 ... Air supply means,
8 ... Vacuum chamber, 9 ... Window, 10 ... Laser device, 11 ... MgO thin film

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H01L 39/24 ZAA B 8728-4M (72) Inventor Thread ▲ Saki ▼ Hideo Kunyo Kita, Itami City, Hyogo Prefecture 1-1-1 Sumitomo Electric Industries, Ltd. Itami Works

Claims (1)

[Claims] 1. A film forming apparatus for an oxide superconducting thin film, comprising: a substrate holder containing a heater; and a vacuum chamber accommodating a target holder for holding a target, the substrate being held on at least the substrate holder on the surface of the heater. A film forming apparatus for an oxide superconducting thin film, characterized in that a region in direct contact with the oxide superconducting thin film is covered with a material stable to the oxide superconducting thin film.