JPH02208207A - Production of superconducting thin film and apparatus therefor - Google Patents

Abstract

PURPOSE:To reduce the temperature of a forming process and form a thin film without any damage by irradiating a substrate with evaporation streams from plural evaporation sources and plasma flows, etc., of an oxygen-based gas and simultaneously introducing oxygen gas from the vicinity of the substrate and forming the thin film. CONSTITUTION:A substrate 4 and plural evaporation sources 3 are provided in a vacuum vessel 1. The surface of the above-mentioned substrate 4 is then irradiated with evaporation streams from the evaporation sources 3 and plasma flows or ion flows of an oxygen-based gas from an ion source 2. An oxygen- based gas is simultaneously introduced from an oxygen-based gas introduction pipe 5 in the vicinity of the substrate 4 into the vacuum vessel 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for producing superconducting thin films, particularly oxide superconducting thin films, which are applied to electronic devices.

Conventional technology It has been proposed that the Y-Ba-Cu-0 system is a high-temperature superconductor with a superconducting transition temperature exceeding 90K [M, in Wu
etc., Physical Review Letters (Physica
l Rev-few Letters) Vol, 58
．． No. 9,908-Old 0 (1987)]. This has made it higher than the boiling point of liquid nitrogen (77K), making it promising for practical use. Furthermore, after that, B i -8r-Ca-Cu-0-based materials and Tl-Ba-Ca-Cu-0-based materials were discovered one after another, which become superconductors at a concentration of 100 or more. Although the details of the superconducting mechanism of these oxide superconducting materials are not clear, their transition temperatures may be higher than room temperature, and they are expected to have more promising properties as high-temperature superconductors than conventional binary compounds.

When such oxide superconductors are to be put to practical use as electronic devices, it is strongly desired that they be made into thin films. Methods for thinning oxide superconductors include sputtering,
There are vacuum evaporation methods, etc.

Problems to be Solved by the Invention When a thin film is put to practical use as an element, stabilizing the characteristics of the thin film and lowering the temperature of the formation process are considered to be fundamental issues.

However, in the sputtering method, the film is formed by exposing the substrate to plasma, so the film surface is easily damaged, and the film thickness varies depending on the plasma distribution, so the entire film is not uniform. Therefore, it is difficult to stabilize the characteristics. There are many complicated parameters such as substrate temperature, gas pressure, gas mixture ratio, distance between the substrate and target, and input power, and it is quite difficult to match the film composition. Furthermore, when a single target is used, the target composition changes with the elapse of sputtering deposition time, resulting in poor reproducibility. Newly discovered oxide superconductors vary in their properties due to differences in their composition, so sputtering is also inconvenient in achieving stable properties in this respect.

Furthermore, it has been confirmed that the electrical conductivity of this type of superconducting material is greatly influenced by the content of oxygen, which is a constituent element. In conventional vacuum deposition methods, the oxygen concentration in the deposited film is insufficient. Therefore, in order to supplement oxygen, after film formation, s o o 'c was carried out in an oxygen atmosphere.
The above high temperature heat treatment is performed. When considering integration with semiconductor devices, high process temperatures are disadvantageous because elements and the like may be destroyed. Further, this heat treatment also has the problem that subtle differences in characteristics occur depending on the treatment conditions, and the operation is complicated.

Means for Solving the Problems In order to solve these problems, the present invention employs a vacuum evaporation method that allows the film composition to be adjusted relatively easily, and a plasma flow of an oxygen-based gas that can supply oxygen to the film. Alternatively, regarding a method and apparatus for forming a thin film using a combined method of ion current irradiation, it is possible to supply sufficient oxygen so that there is no shortage of oxygen concentration, supply ion energy with good controllability, and conduct superconducting at low temperatures without damage. A method and apparatus for forming a thin film are provided.

That is, in the method for producing a superconducting thin film according to the present invention, at least two types of evaporation sources are installed in a vacuum chamber, and an evaporation flow from each evaporation source and an oxygen-based gas plasma are placed on a substrate installed in the vacuum chamber. In this method, a thin film is formed by irradiating a current or an ion current, and the oxygen-based gas is introduced from near the substrate to form a thin film.

Another method for producing a superconducting thin film according to the present invention includes installing at least two types of evaporation sources in a vacuum chamber, and placing an evaporation flow from each evaporation source and an oxygen system on a substrate installed in the vacuum chamber. In this method, a thin film is formed by irradiating a gas plasma flow or an ion flow, and the ion flow of the oxygen-based gas is controlled by a DC electric field to form a thin film.

Further, the superconducting thin film manufacturing apparatus of the present invention includes a vacuum chamber having at least two types of evaporation sources and an ion source for generating oxygen-based gas plasma or ions, in which a substrate is set in the vacuum chamber. It has a configuration in which a gas introduction pipe that can introduce oxygen-based gas is installed nearby.

Another superconducting thin film manufacturing apparatus according to the present invention includes a vacuum chamber having at least two types of evaporation sources, and an ion source for generating oxygen-based gas plasma or ions. It has a mechanism that allows control of the voltage using a DC electric field.

Function The method for producing a superconducting thin film according to the present invention uses plasma of an oxygen-based gas with a high electron temperature and a high degree of dissociation or ion irradiation during vapor deposition, so that the formation process temperature can be lowered and damage-free film formation can be achieved. Furthermore, it is possible to provide a method for forming a superconducting thin film that can eliminate insufficient oxygen uptake in the film by increasing the oxygen partial pressure near the substrate surface. This makes it possible to form electronic devices using superconducting thin films with excellent properties.

Another method for producing a superconducting thin film according to the present invention, like the above-mentioned method for producing a superconducting thin film, can lower the formation process temperature and form a film without damage, and can control the energy of ions of the oxygen-based gas to be irradiated. Therefore, it is possible to provide a method for forming a superconducting thin film that can lower the film forming temperature. This makes it possible to form an electronics element in which a superconductor and a semiconductor are integrated.

Since the superconducting thin film manufacturing apparatus according to the present invention is equipped with at least two types of evaporation sources, it is possible to match the composition by evaporating the required amount of each constituent element, and it is possible to dissociate with low electron energy. Equipped with a high-performance ion/plasma irradiation mechanism, it is possible to lower the formation process temperature and form a film without damage, and because the oxygen-based gas introduction tube is installed near the substrate,
It is possible to provide a device that can increase the oxygen partial pressure near the substrate and solve the problem of insufficient oxygen uptake in the film. By using this device, it is possible to form electronic devices using superconducting thin films with excellent properties.

Another superconducting thin film manufacturing apparatus according to the present invention, like the superconducting thin film manufacturing apparatus described above, has the ability to easily adjust the composition, reduce the formation temperature, and form a film without damage. Additionally, it is equipped with a mechanism that can control the energy of the ions of the oxygen-based gas to be irradiated, making it possible to provide an apparatus that can lower the formation temperature. By using this device, it is possible to form an electronics element that integrates a superconductor and a semiconductor.

Example Embodiments of the present invention will be described using the drawings.

The first conceptual diagram of the superconducting thin film manufacturing apparatus according to the present invention is shown below.
As shown in the figure. The vacuum chamber 1 includes an ion source 2 that generates oxygen-based gas plasma or ions, and two or more evaporation sources 3. Further, a gas introduction pipe 5 is provided so that oxygen-based gas can be introduced into the vicinity of the substrate 4 set in the vacuum chamber 1.

When using this apparatus, it is evacuated to about 10<-7 >Torr in the direction of arrow 6 in advance.

FIG. 2 shows a case where a plasma processing apparatus is used as the ion source 2, which generates plasma by applying a magnetic field and microwaves in a dropwise manner under electron cyclotron resonance conditions. Frequency 2.45G generated by microwave power supply 7
A Hz microwave is passed through a waveguide 8 to a plasma generation chamber 9.
to be introduced. In this case, a solenoid-type electromagnet 10 placed around the plasma generation chamber 9 generates a central magnetic field of 875
By applying a magnetic field to 0aUSS, electron cyclotron resonance is generated in the plasma generation chamber 9. The oxygen-based gas is configured to be introduced into the vicinity of the substrate 4 and into the plasma generation chamber θ through gas introduction pipes 5 and 11, respectively. The gas pressure of the oxygen-based gas in the plasma generation chamber 9 is set to 10-6 to 10-'T.

By setting to rr, a highly active 9 high ionization rate oxygen plasma can be obtained. This oxygen plasma is electromagnet 10
is pulled out into the vacuum chamber 1 by the divergent magnetic field.

An example of forming a Gd-Ba-Cu-0 based superconducting thin film using this apparatus will be described. Using (100) plane MgO as the substrate 4, the G of the evaporation source 3 is heated by electron beam heating.
d1 A Gd-Ba-Cu-0 based thin film is formed on the substrate 4 by irradiating a highly active oxygen plasma flow or ion flow from the ion source 2 using electron cyclotron resonance while vapor depositing each metal of Bat Cu. can be formed. In this case, by using a crystal film thickness monitor, the output of the electron beam evaporation control power supply is controlled and the composition of the formed film is
It was set as dBa2CusOx. Temperature of base 4 is 600℃
Oxygen was used as the oxygen-based gas, and was introduced from a distance of 2 cm from the substrate 4 by spraying it against the substrate 4 through the introduction pipe 5. Microwave power 400W1 Oxygen gas flow rate 5 SCCMl Oxygen gas pressure IX 10-'To
Under the conditions of rr, the total deposition rate of each metal was set to 2. OA/
sec. The G d B a a Cu s Ox film formed to a thickness of about 2000 Å under these conditions exhibited superconductivity, and its superconducting transition temperature was 1 at onset 94 and 82 at zero resistance temperature. Further, the formed film showed C-axis orientation and had good crystallinity. For comparison, a film formed only by vacuum evaporation without using an ion source will be described. The formation conditions were as follows: (100) plane MgO was used as the substrate, and the gas pressure I
X 10-'T.

rr oxygen atmosphere, substrate temperature 700°C, total deposition rate 2. The film thickness is approximately 200OA in OA/sec.

As before, although the formed film showed C-axis orientation, the superconducting transition temperature was 93), but it did not reach zero resistance. This was confirmed by comparing the lengths of the C-axes identified by X-ray diffraction, which showed that the oxygen concentration in the film was insufficient compared to those exhibiting superconductivity. Therefore, by forming a film by irradiating oxygen-based gas ions or plasma while depositing metal components, lOO
In addition to achieving a lower crystallization temperature, the introduction of oxygen-based gas near the substrate eliminates the lack of oxygen uptake in the formed film.

Further, an example in which oxygen gas is introduced from the introduction pipe 11 in addition to the introduction pipe 5 will be described. That is, this is a case where oxygen gas is also introduced into the plasma generation chamber θ. In this case as well, (100) plane MgO is used as the substrate 4, microwave power is 400 Wl, total gas pressure of oxygen is
Under the condition of 10-'Torr, the total deposition rate of each metal was set to 2. A GdBa2cusox film with a thickness of about 2000A was formed at an OA/sec.

The substrate temperature was 600° C., the formed film was a C-axis oriented film and exhibited superconductivity, and the superconducting transition temperature was 94 at onset and 85 at zero resistance temperature. As a result, it can be said that the zero resistance temperature is slightly improved.

This is because oxygen gas is also introduced into the plasma generation chamber 9, so the gas pressure inside the plasma generation chamber increases, and oxygen becomes more active in the plasma generation chamber than when oxygen gas is introduced only near the substrate. This is thought to be because the light is decomposed into plasma and ions and irradiated onto the substrate 4.

Next, FIG. 3 shows a conceptual diagram of another superconducting thin film manufacturing apparatus according to the present invention. The vacuum chamber 1 includes an ion source 2 that generates oxygen plasma or ions and two or more evaporation sources 3.
evening. Further, the ion source 2 is electrically floated by an insulator 12 so as not to have the same potential as the vacuum chamber 1, and a DC electric field is applied between it and the substrate 4 by a DC power source 13.

FIG. 4 shows a case where a plasma processing apparatus is used as the ion source 2, which generates plasma by applying a magnetic field and microwaves so as to satisfy the electron cyclotron resonance conditions. The plasma and the second generation are as described above, and the generated oxygen ions are accelerated by a direct current electric field to form the base 4.
can be irradiated. That is, by using the DC power supply 13, it is possible to control the incident energy of oxygen ions.

An example of forming a Gd-Ba-Cu-○ superconducting thin film using the apparatus shown in FIG. 4 will be described. The substrate 4 is made of (100) plane MgO as described above, and each metal of Gd1 Ba and Cu is deposited from the deposition source 3 by electron beam heating.
When irradiating oxygen plasma and ions generated by an ion source 2 using electron cyclotron resonance and extracted by a divergent magnetic field, the extracted oxygen ions are accelerated by a DC electric field. In this case, the substrate temperature was 550° C., oxygen gas was introduced through the introduction pipe 11, and the flow rate was 53 CCM.

Gas pressure I x 10-'Torr, microwave power 400W.

5 between the plasma generation chamber 9 and the base 4 by the DC power supply 12
Approximately 250 OA was deposited by applying an accelerating voltage of 0 V. The formed film was a C-axis oriented film and exhibited superconductivity, with a superconducting transition temperature of 93 K and a zero resistance temperature of 81 K. For comparison, when other conditions are the same and no accelerating voltage is applied, although C-axis orientation is observed, (103), (
110) Planar orientation was also observed, indicating polycrystalline orientation. Although the superconducting transition temperature was 91 at onset, the zero resistance temperature was 45. In order to obtain similar C-axis orientation and superconducting properties, the substrate temperature had to be about 620°C. Therefore, by applying an accelerating voltage of 50 V to oxygen ions, it was possible to lower the temperature of the forming substrate.

Furthermore, an example in which oxygen gas is introduced from the introduction tube 5 in addition to the introduction tube 11 when applying the acceleration voltage in this manner will be described. That is, this is a case in which oxygen gas is introduced into the plasma generation chamber 9 and in a manner such that it is blown onto the base 4 . (100) plane Mg as the base 4
Using O, microwave power 400W, gas pressure I
10-'Torr.

An accelerating voltage of 50 V was applied between the plasma generation chamber 9 and the substrate 4 under the condition that the substrate temperature was 550'C. The formed G d B a 2 Cu a Ox film has a thickness of about 2000A
It exhibited C-axis orientation at a film thickness of , and its superconducting transition temperature was 1 at onset 94 and zero resistance temperature 84.

Therefore, by blowing oxygen gas onto the substrate 4, the oxygen in the formed film was reduced to some extent, and as a result, the zero resistance temperature was improved.

Next, a case where O3 (ozone) or N2O (nitrous oxide) is used as the oxygen-based gas will be described.

O3 was generated by generating O2 at a concentration of 5% using an ozonizer. The difference between O3, N2O and oxygen alone is that, for example, when a microwave plasma source using electron cyclotron resonance is used as the ion source 2, the microwave power can lower the oxygen concentration in the formed film with lower power. This has the effect of being able to supply

For example, when using 5% o3, GdBa2Cu30
8 thin film, substrate temperature 550°C1) - Tal gas pressure I
10''Torr, under the conditions that gas is introduced through introduction tubes 5 and 11 and an accelerating voltage of 50V is applied to the generated ions, the microwave power is a minimum of 200W and the superconducting transition temperature is ONCERA) 94 K1 Zero resistance temperature 8
A film having the characteristics shown in No. 5 was formed. Further, when N2O is used, film properties comparable to those described above can be obtained with a microwave power of 150 W, but when the microwave power is increased to 300 W or more, the superconducting properties deteriorate due to the influence of nitrogen plasma and ions. However, it was confirmed that in the range of 150 to 300 W, there was no effect on the superconducting properties or the orientation of the film.

Furthermore, when the DC voltage applied between the plasma generation chamber 9 and the substrate 4 is set to 100 V when oxygen gas is introduced, the C-axis orientation is exhibited at the substrate temperature of 490°C, and the transition temperature of the superconducting property is One zero resistance section of 79K was obtained in 81. When the DC voltage was 200 V, C-axis orientation was exhibited at a substrate temperature of 400° C., and although the onset temperature was 92, the zero resistance temperature was as low as 48. However, it was confirmed that superconductivity was exhibited even at a substrate temperature of 400°C.

Effects of the Invention The method for producing a superconducting thin film of the present invention uses a combined method of evaporation and plasma ion irradiation that can lower the formation process temperature and form a film without damage. By introducing oxygen at a high partial pressure and supplying sufficient oxygen to the film, it is possible to form a superconducting thin film with excellent properties. By using this superconducting thin film, it is possible to realize an element with stable characteristics.

Another method for producing a superconducting thin film according to the present invention is a combined method of vapor deposition and plasma ion irradiation, and by accelerating the energy of oxygen-based gas ions, the film forming temperature can be lowered. This has widened the range of applications, such as integration with semiconductor devices.

The superconducting thin film manufacturing apparatus of the present invention is equipped with an evaporation source that allows for easy composition adjustment and an ion/plasma irradiation mechanism with low electron energy and high degree of dissociation. In addition, since the oxygen-based gas introduction tube is installed near the substrate, the oxygen partial pressure near the substrate can be increased, and by supplying sufficient oxygen to the film, the characteristics can be improved. Formation of excellent superconducting thin films can be achieved.

Another superconducting thin film manufacturing apparatus of the present invention is similar to the above,
The soil has the function of combining vapor deposition and plasma ion irradiation, and is equipped with a mechanism that can accelerate the energy of the ions of the irradiated oxygen-based gas, making it possible to lower the film formation temperature. By using this device, it is possible to integrate a superconducting element and a semiconductor element.

In particular, there is a possibility that the transition temperature of the oxide superconductor is higher than room temperature, so the practical scope of the present invention is wide and the industrial value of the present invention is extremely high.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the superconducting thin film manufacturing apparatus of the present invention, Figure 2
The figure is a conceptual diagram of a plasma processing apparatus that generates plasma by applying a magnetic field and microwaves so as to set the electron cyclotron resonance conditions as the ion source in Figure 1, and Figure 3 is a conceptual diagram of another embodiment of the present invention. A conceptual diagram of a superconducting thin film manufacturing apparatus. Figure 4 is a conceptual diagram of a plasma processing apparatus that generates plasma by applying a magnetic field and microwaves to satisfy the electron cyclotron resonance conditions as the ion source in Figure 3. It is. 1. Vacuum chamber, 2. Ion source, 3. Evaporation source,
4...Base body, 5-shaped oxygen-based gas introduction tube, 7...Microwave power source, 8...Waveguide, 9...Plasma generation chamber, No. 10 magnet, 11... Oxygen gas introduction pipe, 1
2, φ, insulator, work 3, fist DC voltage source.

Claims (1)

[Scope of Claims] (1) At least two types of evaporation sources are installed in a vacuum chamber, and an evaporation flow from each evaporation source and a plasma flow of oxygen-based gas or In addition to using a method of forming a thin film by irradiating an ion stream,
A method for producing a superconducting thin film, characterized in that the oxygen-based gas is introduced from near a substrate to form a thin film. (2) A method for producing a superconducting thin film according to claim 1, characterized in that the thin film is formed by introducing an oxygen-based gas into an ion source device. (3) The method for producing a superconducting thin film according to claim 1, wherein the thin film is formed by controlling the ion flow of oxygen-based gas using a DC electric field. (4) At least two types of evaporation sources are installed in a vacuum chamber, and the substrate installed in the vacuum chamber is irradiated with an evaporation flow and an oxygen-based gas plasma flow or ion flow from each of the evaporation sources. In addition to using a method of forming a thin film by
A method for producing a superconducting thin film, comprising forming the thin film by controlling the ion flow of the oxygen-based gas using a DC electric field. (5) The method for producing a superconducting thin film according to claim 4, characterized in that the oxygen-based gas is introduced from near the substrate. (8) The method for producing a superconducting thin film according to claim 1 or 4, characterized in that at least one of O_2, O_3, and N_2O is used as the oxygen-based gas. (7) The method for manufacturing a superconducting thin film according to claim 1 or 4, wherein an evaporation method using electron beam heating or resistance heating is used as a method for evaporating the evaporation source. (8) The ion source device is a plasma processing device that generates plasma by applying a magnetic field and microwaves so as to satisfy electron cyclotron resonance conditions. A method for manufacturing superconducting thin films. (9) A method for producing a superconducting thin film according to claim 1 or 4, characterized in that the temperature of the substrate during thin film formation is set to a predetermined temperature of 400 to 700°C. (10) In a vacuum apparatus having a vacuum chamber having at least two types of evaporation sources and an ion source that generates oxygen-based gas plasma or ions, introducing an oxygen-based gas into the vicinity of a substrate set in the vacuum chamber. What is claimed is: 1. A superconducting thin film manufacturing apparatus characterized by having a configuration in which a gas inlet pipe is installed that allows for. (11) The apparatus for producing a superconducting thin film as set forth in claim 10, characterized in that an oxygen-based gas introduction pipe is set within the ion source device. (12) Claim 1, characterized in that it is provided with a mechanism that can control the ion flow of oxygen-based gas using a DC electric field.
The superconducting thin film manufacturing apparatus according to item 0. (13) A vacuum apparatus having a vacuum chamber having at least two types of evaporation sources and an ion source that generates oxygen-based gas plasma or ions is provided with a mechanism that can control the oxygen-based gas ions using a DC electric field. Features: Superconducting thin film manufacturing equipment. (14) The apparatus for producing a superconducting thin film according to claim 13, characterized in that an oxygen-based gas introduction pipe is provided near the base. (15) The apparatus for manufacturing a superconducting thin film according to claim 10 or 13, wherein the evaporation device for the evaporation source is an evaporation device using electron beam heating or resistance heating. (16) Claim 10 or 13, characterized in that the ion source device is constituted by a plasma processing device that generates plasma by applying a magnetic field and microwaves so as to satisfy electron cyclotron resonance conditions.
An apparatus for producing a superconducting thin film as described in 2.