JP3163651B2 - Superconducting thin film forming method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a superconducting thin film, and more particularly to a method and an apparatus for forming a high-temperature composite oxide superconducting material on a large-area thin film by a magnetron sputtering method. Things.

[0002]

2. Description of the Related Art Bednotes and Muellers were 30
Composite oxide superconducting material showing superconducting state at K (La, Ba) ₂
I found CuO ₄ . In 1987, Chu and others discovered YBa ₂ Cu ₃ O _y having a superconducting critical temperature Tc of the order of 90 K,
In 1988, a critical temperature of over 100K was shown by Tatsu Maeda
Bi-based composite oxide superconducting materials have been discovered. In this specification, a composite oxide exhibiting a superconducting critical temperature of 30 K or more is referred to as a high-temperature composite oxide superconducting material. These high-temperature composite oxide superconducting materials were obtained as sintered bodies by powder metallurgy. However, since the superconducting properties, particularly the critical current density, of the sintered body do not increase, methods for forming thin films of these materials have been studied. Generally, thin films of these composite oxide-based superconducting materials are formed on a single crystal substrate of SrTiO ₃ or MgO by various vapor deposition methods such as a vacuum vapor deposition method, a sputtering method, and an MBE method. A method for thinning a superconducting material is known. At present, there have been proposed methods of applying the thin film to various devices, elements, and circuit configurations, rather than merely confirming the superconducting properties of the thin film by making the thin film. Therefore, there is a demand for stable supply of an oxide superconducting thin film having characteristics guaranteed for use in such research and development. Further, there is a demand for thin films of various dimensions suitable for various uses, especially for large-area composite oxide superconducting thin films. The present applicant, when forming an oxide superconducting thin film by a sputtering method, prevents the thin film being formed from being adversely affected by secondary electrons or high energy charged particles emitted from a target during the film formation. for,
A method for preventing the target and the substrate from facing each other in the front has already been proposed. However, the oxide superconducting thin film formed over a large area by the above-described method or the conventional film forming method by the present applicant, for example, the sputtering method which is the most common film forming method, has a distribution in the film quality within one thin film. Therefore, it has been difficult to form circuits and elements in one thin film.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a novel method for efficiently depositing a superconducting thin film having uniform properties over a large-area substrate, and a method for this method. And a device for carrying out the operation.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for forming a thin film of a high-temperature composite oxide superconducting material over a large area on a substrate by magnetron sputtering, comprising an elongated magnetron corresponding to the longitudinal length of the thin film. On the electrode, an elongated target substantially corresponding to the above-mentioned longitudinal length of the magnetron electrode is fixed, and an elongated substrate having a predetermined length in the longitudinal direction is fixed at a predetermined angle with respect to the surface of the target. And the target and the substrate are arranged in a state where they are aligned in the longitudinal direction with each other, and sputter particles jumping out of the target are deposited on the substrate while moving the substrate in a direction crossing the longitudinal direction of the target during sputtering. To provide a method.

The present invention further provides a magnetron sputtering apparatus for forming a large-area thin film of a high-temperature composite oxide superconducting material on a substrate, wherein the magnetron electrode serving also as a target holder has a length in the longitudinal direction of the thin film. The substrate holder holding the substrate has an elongated shape corresponding to the longitudinal length of the magnetron electrode, and the target and the substrate have an elongated shape corresponding to the magnetron electrode and the substrate holder, respectively. ,
Apparatus characterized in that the surface of the substrate is arranged at an angle to the surface of the target, and further, means for moving the substrate in a direction transverse to the longitudinal direction of the target during sputtering is provided. I will provide a.

One feature of the present invention is that when a thin film is formed by a sputtering method, the thin film being formed is not adversely affected by secondary electrons or high-energy charged particles emitted from a target during the film formation. In this case, the target and the substrate do not face each other in front. That is, the relative position of the substrate with respect to the target is set such that the substrate forms a certain angle in the range of 70 to 90 degrees with respect to the target so that the surface of the target and the surface of the substrate do not face each other.

However, in such an arrangement, since the distance from the target to the substrate differs depending on the position on the substrate, when the width of the substrate is large, the film quality tends to be distributed. Therefore, in the present invention, the width of the substrate is narrowed with respect to the length in the longitudinal direction, that is, the shape of the substrate is minimized by making the shape of the substrate long and narrow, for example, a long rectangle, thereby minimizing the deviation of the film quality distribution in the width direction of the substrate. A substantially uniform thin film is formed on the entire surface. Although the shape of the substrate and the target is not particularly limited, it is generally preferable that the shape is a quadrangle, particularly an elongated long rectangle.

In a particularly preferred embodiment of the present invention, the displacement of the distribution of sputter particles in the width direction on the substrate is further compensated by moving the substrate in a direction transverse to the longitudinal direction of the target during sputtering. By using this method, an extremely large-area oxide superconducting thin film can be formed on a large substrate having an arbitrary width. In this case, there is no limitation on the width of the substrate.

The present invention can be applied to any known high-temperature composite oxide superconducting material. Specifically, (La, Ba) ₂
High-temperature composite oxide superconducting materials of CuO ₄ system, YBa ₂ Cu ₃ O _y system, Bi system, and Ta system can be given.

[0010] The magnetron sputtering method used in the present invention is known. It is preferable to use the following ranges as the film forming conditions: Gas pressure during film formation: 0.1 Torr to 1 Torr Substrate temperature: 550 to 750 ° C. Applied power during film formation: 3 W / cm ^{2 to} 8 W / cm ² In general, a thin film formed under film forming conditions outside these ranges may have extremely low superconducting properties or may not be a superconducting thin film.

[0011]

According to the present invention, a sputtering target is mounted on a long magnetron electrode to perform sputtering, thereby widening the distribution of sputter particles and depositing the wide sputter particles on a substrate. A wide thin film of the composite oxide superconducting material can be formed. By making the target and the substrate long rectangular, and arranging the target surface and the substrate surface so that they are perpendicular to each other, it is possible to form a long oxide superconducting thin film with uniform film quality. Become. In addition, by forming a film while moving the substrate in a direction substantially perpendicular to the surface of the target from which sputtered particles fly, an oxide superconducting thin film having an extremely large area can be formed on a substrate having an arbitrary size. . Hereinafter, an example of an apparatus used to carry out the method of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram of one embodiment of a film forming apparatus used to carry out the method of the present invention. The film forming apparatus shown in FIG. 1 includes a magnetron electrode 2 also serving as a target holder disposed in a vacuum chamber 1, and a substrate holder 3 having a built-in heater 3 a disposed on a side of the magnetron electrode 2. . The vacuum chamber 1 has an exhaust hole 4 for connecting the inside thereof to an exhaust system, a gas supply hole 5 for supplying a sputtering gas therein, and an oxygen gas for supplying oxygen gas to the vicinity of the deposition surface of the substrate held by the substrate holder 3. Oxygen supply nozzle 6. A nut 33 is fixed to the back of the substrate holder 3, and the nut 33 is screwed to the screw rod 32. The screw rod 32 can be rotated by a rotating mechanism (not shown) provided in a stand 31 disposed behind the substrate holder 3. Therefore, when the screw rod 32 is rotated, the substrate holder 3 and thus the substrate 9 move up and down. FIG. 2 is a perspective view showing a relative positional relationship between the magnetron electrode 2 and the substrate holder 3. In FIG. 1, the magnetron electrode 2 and the substrate holder 3 extend in a direction perpendicular to the plane of the drawing. In the embodiment shown in FIG. 2, the magnetron electrode 2 is an elongated rectangle, on which an elongated target 8 of substantially the same shape is mounted. Similarly, the substrate holder 3 is also rectangular, on which an elongated substrate 9 of substantially the same shape is held. The size of the magnetron electrode 2 is, for example, 200 mm ×
Can be 70mm.

At the time of sputtering, a target 8 is fixed on the magnetron electrode 2, a substrate 9 is fixed on the substrate holder 3, and once the inside of the vacuum chamber 1 is evacuated, an inert gas such as argon gas is introduced, and the heater 3a The target 8 is sputtered while blowing oxygen gas from the oxygen supply nozzle 6 toward the film-forming surface of the substrate 9 in a state where the substrate 9 is heated to a predetermined temperature by energizing the substrate 9 to deposit a target material on the substrate. Film. Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0014]

EXAMPLE 1 Using a film forming apparatus shown in FIG. 1, YBa ₂ Cu ₃ O _7-x (x = ±
The composite oxide superconducting thin film of 1) was formed. The size of the target 8 fixed on the magnetron electrode 2 is 190 mm x 60 mm
The size of the substrate fixed on the substrate holder 3 is 180 mm
The film was formed on a (20) plane on a MgO single crystal substrate of × 20 mm. Table 1 summarizes the magnetron sputtering film forming conditions.

[0015]

[Table 1] Target composition (atomic ratio): Y: Ba: Cu = 1: 2: 2.8 Sputtering gas: Ar + O_Two  O_Two/ (Ar + O_Two) = 20% (volume ratio) Gas pressure: 0.5 [Torr] Substrate temperature: 650 [° C] Applied power: 600 [W], 4.2 [W / cm^Two] Thickness: 3000 [Å] Superconductivity of each part on the thin film of the sample formed under these conditions
The properties were measured. The measurement results are shown in Table 2. In addition,
The measurement positions, that is, the measurement parts (a) to (f) are shown in FIG.
It is.

[0016]

[Table 2] Measurement position Critical temperature Tc Critical current density Jc [K] [A / cm ² ] a 88 2.3 × 10 ⁶ b 89 3.5 × 10 ⁶ c 87 1.9 × 10 ⁶ d 90 4.0 × 10 ⁶ e 89 3.4 × 10 ⁶ f 86 1.8 × 10 ⁶ (Note) Critical temperature Tc: Temperature at which the electrical resistance of the sample falls below the measurement limit. Critical current density Jc: Critical current density at 77K. Table 2 shows that by using the present invention, a long and thin composite oxide superconducting thin film having uniform film quality can be formed on a long substrate.

Embodiment 2 An oxide superconducting thin film was manufactured using the same apparatus and material as in Embodiment 1 under the same film forming conditions as in Embodiment 1. In this embodiment, a substrate 9 having a size of 180 mm × 60 mm was used. An MgO single crystal substrate (film formation surface was a (100) surface) was used, and a film was formed while reciprocating the substrate 9 in the vertical direction. Actually, the substrate holder 3 of the apparatus shown in FIGS. 1 and 2 was reciprocated up and down at a moving speed of 10 mm / sec. Table 3 shows the superconducting properties of each part on the thin film of the sample formed under these conditions. In addition,
The measurement position, ie, the measurement part, is shown in FIG.

[0018]

[Table 3] Measurement position Critical temperature Critical current density Tc [K] Jc [A / cm ² ] g 86 1.9 × 10 ⁶ h 88 2.8 × 10 ⁶ i 89 3.1 × 10 ⁶ j 85 1.6 × 10 ⁶ k 88 2.7 × 10 ⁶ l 87 2.2 × 10 ⁶ The results in Table 3 indicate that a composite oxide superconducting thin film with uniform film quality in the width direction can be formed on the entire long substrate by reciprocating the substrate 9 up and down. Is shown.

Example 3 Using the same apparatus as in Example 1, and performing the same operation,
_{A 2} Cu ₃ O _7-x thin film was formed. However, in this embodiment, the size of the target 8 is 140 mm × 60 mm, and the MgO single crystal substrate 9
The dimensions of (the surface on which the film was formed) were 180 mm × 60 mm, and the film was formed while the substrate 9 was reciprocated vertically. In addition, a plurality of samples were prepared by changing the substrate temperature in a temperature range from 500 ° C. to 750 ° C. every 50 ° C. Other film forming conditions are summarized in Table 4.

[0020]

[Table 4] Target composition (atomic ratio): Y: Ba: Cu = 1: 2: 2.8 Sputtering gas: Ar + O ₂ O ₂ / (Ar + O ₂ ): 20% (volume ratio) Gas pressure: 0.5 [Torr] Applied power : 600 [W], 4.2 [W / cm ² ] Film thickness: 3000 [Å] Substrate moving speed: 10 [mm / sec] The superconducting characteristics of each part on the thin film of the sample formed under the above film forming conditions were measured. . The measurement results are summarized in Table 5. The measurement positions are shown in FIG.

[0021]

[Table 5] Measurement position characteristics Substrate temperature [° C] 550 600 650 700 750 a Tc 72 83 86 84 68 Jc ─ 9.2 × 10 ⁵ 1.9 × 10 ⁶ 7.1 × 10 ⁶ ｂ b Tc 69 81 88 82 64 Jc ─ 8.1 × 10 ⁵ 2.8 × 10 ⁶ 9.1 × 10 ⁵ ─ c Tc 70 86 89 83 61 Jc ─ 1.7 × 10 ⁶ 3.1 × 10 ⁶ 9.3 × 10 ⁵ ｄ d Tc 67 82 85 83 65 Jc ─ 9.0 × 10 ⁵ 1.6 × 10 ⁶ 8.1 × 10 ⁵ ─ e Tc 74 85 88 81 62 Jc ─ 1.2 × 10 ⁶ 2.7 × 10 ⁶ 8.9 × 10 ⁵ ｆ f Tc 71 80 87 80 59 Jc ─ 6.5 × 10 ⁵ 2.2 × 10 ⁶ 6.2 × 10 ⁵ ─ ( Note) Tc: Critical temperature: Temperature at which the electrical resistance of the sample falls below the measurement limit. The unit is absolute temperature [K]. Jc: Critical current density: Critical current density at 77K The unit is [A / cm ² ].

Example 4 Example 3 was repeated except that the substrate temperature was fixed at 650 ° C.
A plurality of samples were formed by changing the gas pressure during film formation as shown in Table 6. Other film forming conditions are the same as those of the third embodiment. Table 6 summarizes the measured superconducting properties of the fabricated samples. The measurement position is the same as that of the third embodiment in FIG.

[0023]

[Table 6] Measurement position Characteristics Gas pressure [Torr] 0.05 0.2 0.5 1.0 2.0 a Tc 52 81 86 84 78 Jc ─ 8.9 × 10 ⁵ 1.9 × 10 ⁶ 7.2 × 10 ⁶ 1.2 × 10 ⁴ b Tc 48 83 88 87 74 Jc 9.8 9.8 × 10 ⁵ 2.8 × 10 ⁶ 2.8 × 10 ⁶ ─ c Tc 39 84 89 86 71 Jc ─ 1.2 × 10 ⁶ 3.1 × 10 ⁶ 2.5 × 10 ⁶ ｄ d Tc 49 83 85 82 73 Jc ─ 9.1 × 10 ⁵ 1.6 × 10 ⁶ 1.0 × 10 ⁶ ─ e Tc 50 85 88 84 72 Jc ─ 2.1 × 10 ⁶ 2.7 × 10 ⁶ 1.7 × 10 ⁶ ｆ f Tc 32 83 87 85 76 Jc ─ 1.0 × 10 ⁶ 2.2 × 10 ⁶ 2.2 × 10 ⁶ ─

Example 5 Example 3 was repeated except that the substrate temperature was fixed at 650 ° C.
A plurality of samples were prepared by changing the applied power during film formation as shown in Table 7. Other film forming conditions were the same as in Example 3. Table 7 summarizes the measured superconducting properties of the fabricated samples. The measurement position is the same as FIG.

[0025]

Table 7 Measurements position characteristic applied power (W) 300 450 600 800 1000 a Tc 38 81 86 87 81 Jc ─ 8.1 × 10 5 1.9 × 10 6 2.3 × 10 6 6.8 × 10 5 b Tc 41 83 88 86 77 Jc ─ 1.2 × 10 ⁶ 2.8 × 10 ⁶ 2.1 × 10 ⁶ ─ c Tc 37 85 89 88 80 Jc ─ 1.5 × 10 ⁶ 3.1 × 10 ⁶ 3.3 × 10 ⁶ 6.1 × 10 ⁵ d Tc 36 84 85 89 78 Jc ─ 1.3 × 10 ⁶ 1.6 × 10 ⁶ 3.7 × 10 ⁶ 1.8 × 10 ⁴ e Tc 42 86 88 87 79 Jc ─ 2.0 × 10 ⁶ 2.7 × 10 ⁶ 2.9 × 10 ⁶ 9.8 × 10 ⁴ f Tc 50 84 87 88 80 Jc ─ 2.0 × 10 ⁶ 2.2 × 10 ⁶ 3.1 × 10 ⁶ 5.3 × 10 ⁵

[0026]

By using the film forming method of the present invention, an oxide superconducting thin film having a uniform film quality can be formed on the entire surface of a long substrate. By applying the film forming method of the present invention, a large-area oxide superconducting thin film can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a film forming apparatus that can be used to carry out the method of the present invention. FIG. 2 is a perspective view showing a relative positional relationship between a target holder and a substrate holder in the film forming apparatus shown in FIG. FIG. 3 is a diagram showing a measurement position of a sample made in one embodiment of the present invention. FIG. 4 is a diagram showing a measurement position of a sample made in another embodiment of the present invention.

【reference number】

DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber, 2 ... Magnetron electrode, 3 ... Substrate holder, 4 ... Exhaust hole, 5 ... Sputter gas supply hole, 6 ... Oxygen gas supply hole 8 ... Target , 9 ... substrate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-134825 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 29/22 C23C 14 / 08,14 / 35 C01G 1/00 C01B 13/14

Claims (2)

(57) [Claims] 1. A method for forming a large-area thin film of a high-temperature composite oxide superconducting material on a substrate by a magnetron sputtering method, comprising: forming a thin film of the high-temperature composite oxide superconducting material on an elongated magnetron electrode corresponding to a longitudinal length of the thin film; An elongated target substantially corresponding to the length in the longitudinal direction is fixed, and an elongated substrate having a predetermined length in the longitudinal direction is fixed at an angle of 70 to 90 degrees with respect to the surface of the target with respect to the surface of the target. And the target and the substrate are arranged in a state where they are arranged in the longitudinal direction with respect to each other, and sputter particles jumping from the target are deposited on the substrate while moving the substrate in a direction crossing the longitudinal direction of the target during sputtering. how to. 2. A magnetron sputtering apparatus for forming a large-area thin film of a high-temperature composite oxide superconducting material on a substrate, wherein a magnetron electrode serving also as a target holder has an elongated shape corresponding to the longitudinal length of the thin film. Having a shape, the substrate holder holding the substrate has an elongated shape corresponding to the longitudinal length of the magnetron electrode, the target and the substrate have an elongated shape corresponding to the magnetron electrode and the substrate holder, respectively, The surface is arranged so as to form a certain angle with respect to the surface of the target within a range of 70 to 90 degrees, and further, means for moving the substrate in a direction transverse to the longitudinal direction of the target during sputtering is provided. An apparatus characterized by the above.