JP2005089793A - Method for manufacturing thin film, method for manufacturing wire rod with thin film, and vapor deposition apparatus with pulsed laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin film, which forms the thin film on a substrate with a large area and a wide wire rod and solves a problem that a vapor deposition method with a conventional pulsed laser beam forms a practically-uniform thin film on just a narrow region. <P>SOLUTION: In the vapor deposition method with the pulsed laser beam for forming the thin film on the substrate through irradiating a target with a laser beam to form plasma and depositing the vaporized target material on the substrate, this film-forming method comprises condensing the laser beam 33 on the target 31 so as to form a linear shape, and arranging the substrate to be film-formed within a range of plus and minus 45 degrees from the Y axis when viewed from a Z direction, when the origin is supposed to be located in the center of the linear laser beam on the irradiated surface of the target 31, the Z axis to be a long side direction, an X-axis to be a short side direction and the Y axis to be the normal direction with respect to a target face. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thin film manufacturing method for forming a thin film such as a superconducting material on a substrate by vapor deposition using laser light.

  Superconducting elements and superconducting wires have been developed that have a structure in which a thin film of a superconducting material is formed on a substrate. For forming such a superconducting thin film, various sputtering methods, laser ablation methods, MBE methods and the like are known, and a pulse laser deposition method (PLD method) using laser light is one of them. For example, Non-Patent Document 1 shows a PLD method as a method for manufacturing a high-temperature superconducting thin film wire.

  The outline of the PLD method will be described with reference to FIG. Laser light 11 from the pulse laser 10 is condensed by a lens 12 and irradiated onto a target 13 which is a superconducting material. Here, the laser light is condensed on the target by an optical system such as a lens and is focused on a circle or a rectangle. On the target surface irradiated with the laser light, the target material is turned into plasma by the energy of the laser light and scattered, and a light emitting portion called plume 14 is formed. The plume 14 has a substantially spindle shape that is rotated with the normal direction of the target material surface as an axis from the irradiation point of the laser beam. By disposing the substrate 15 on which the thin film is to be deposited inside the plume or in the vicinity of the plume tip, the scattered particles can be epitaxially grown on the substrate to form a thin film.

In such a PLD, the target material irradiated with the laser light is consumed, so that it is necessary to sequentially supply new target material in order to continuously manufacture the thin film. For this reason, the laser light is scanned or the target is moved so as to sequentially shift the irradiation point of the laser light on the target. A method of rotating a cylindrical target is also considered as the target movement.
Fujino et al. "Development of high-temperature superconducting thin film wire by ISD method", SEI Technical Review, No.155, September 1999, p131-132

  In the conventional method, a substrate on which a thin film is to be formed is disposed, for example, near the plume tip. However, as the plume has a spindle shape, the density of scattered particles and the degree of activity vary depending on the location, and the range where practically uniform thin film formation is possible (hereinafter referred to as “thin film formation region” in this application) is limited. Therefore, a uniform film cannot be obtained when the substrate area is larger than the plume size. In order to form a thin film on a large-area substrate, there is a method of scanning the substrate. However, it is difficult to control the amount of material to be scattered and the amount of material to be deposited in the target scanning and the substrate scanning. It is very difficult to form an area film. In the case of producing a long thin film wire, a thin film is continuously formed by sequentially feeding substrates on a tape, but it is difficult to form a wide wire.

  Further, there is a problem in the scanning of the target for sequentially changing the irradiation point. Since the surface of the target irradiated with laser light while scanning is in the form of a groove, if the next adjacent part is irradiated with the laser light, a certain amount of scattering cannot be produced unless the groove is overlapped with the groove. . Therefore, it is necessary to leave a certain interval in scanning, and it is difficult to effectively use the entire surface of the target.

  In order to solve the above problems, it is conceivable to simultaneously use a material having a large area of the target by spreading and irradiating the laser beam. When the beam is expanded and irradiated, the plume itself is also expanded, and as a result, a thin film can be formed simultaneously or uniformly on a large-area substrate.

  For this reason, in the pulsed laser deposition method in which a thin film is formed on a substrate by depositing a target material that has been turned into plasma by irradiating the target with laser light, the laser light is focused in a line on the target. When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface. In addition, a thin film manufacturing method is characterized in that a thin film is formed on the substrate disposed in a range of 45 degrees from the Y axis when viewed from the Z direction.

  As a result, the thin film formation region can be remarkably widened as compared with the conventional case, and the efficiency of thin film production can be improved. Moreover, the target surface can be used efficiently.

  Here, the line shape means a substantially rectangular irradiation range having a short side and a long side in the irradiated portion on the target, and may be a shape close to an ellipse. It is preferable in terms of uniform plume formation to have a short side in the laser light irradiation direction and a long side in a direction orthogonal to the irradiation direction.

  Further, the second problem solving means is to arrange the substrate at the tip position height of the plume generated in the upper part of the target surface when the target is turned into plasma by laser irradiation and scattered. This is preferable in that a thin film having relatively good characteristics can be formed efficiently.

  As a third problem solving means, when a high-temperature superconducting thin film wire is manufactured, a wire rod (referred to as a “wire substrate”) as a substrate is successively fed into the thin film formation region to continuously form the substrate on the wire substrate. Although a thin film is formed, in the manufacturing method using the above-mentioned line-shaped laser light irradiation, a plurality of wire substrate substrates can be simultaneously fed into the thin film forming area by utilizing the fact that a thin film forming area can be secured widely. It was set as the manufacturing method of the thin film wire characterized.

  This is due to the fact that a thin film forming region is widely obtained, and is effective in improving the manufacturing capability of the thin film wire, that is, in reducing the manufacturing time or in mass production.

  In addition, as a fourth application, the fourth problem solving means can form a thick thin film by repeatedly feeding the same wire, not the plurality of wires to be fed, as separate wires.

  As a result, a thick film can be formed by repeatedly forming a thin film on the same substrate, so that the current that can be applied according to the thickness of the film, such as a superconducting wire, can be increased. The production efficiency can be dramatically improved.

  Although the above has described the manufacturing method, the thin film and the thin film wire using the apparatus can be manufactured by configuring the pulse laser deposition apparatus itself so that the above method is possible.

  When a thin film such as a superconducting thin film is formed on a substrate by using the above-described line-shaped laser light, it becomes easy to form a more uniform thin film simultaneously with a larger area than in the past. In addition, by using the target widely, the target surface can be used without waste in laser light scanning on the target, and efficient production is possible. Therefore, when manufacturing a rare earth-based high-temperature superconducting thin film element or wire generally called RE123, it is particularly effective in that a large-area high-temperature superconducting thin-film element or a wide high-temperature superconducting thin-film wire can be manufactured. It is. Furthermore, even in the manufacture of a narrow wire, a plurality of wires can be formed at the same time, so that there is a special effect in reducing the cost by shortening the manufacturing time. In addition, a thin film wire having a large thickness can be efficiently manufactured by repeatedly forming the same wire.

  The inventor has developed a technique for forming a plume that expands in a line to form a plume that expands in a line and forms a film in a wide region. Among them, the present inventor does not have a plume that is formed by spreading laser light in a line shape and irradiating a planar target with a spindle-shaped plume formed in the case of single point irradiation. Focused on the formation of a unique shape. That is, when the shape of the laser beam irradiation range is substantially rectangular, the origin is at the center of the irradiation range, the Z axis is in the long side direction, the X axis is in the short side direction, and the Y axis is in the normal direction of the target surface In the plume generated from the target irradiated in a line shape, when viewed in the XY plane from the Z-axis direction, the spread from the origin is larger than that in the case of point irradiation, and the thin film formation region can be widened.

  This will be described with reference to FIG. FIG. 1A shows the case of conventional point irradiation, and FIG. 1B shows the case of line irradiation. In each case, plumes 22 and 32 generated by irradiating laser beams 23 and 33 to the targets 21 and 31 are shown. In the figure, (upper surface) is a top view showing the shape of the formed plume as viewed from the Y-axis direction in the XZ plane, and (side) is a side view of the plume as viewed from the Z-axis direction in the XY plane. , (Beam) is a diagram showing the shape of the laser beam at the irradiation point, and is schematically represented as a schematic shape for explaining the difference. In the point irradiation of FIG. 1A, the laser light is irradiated to one point in a rectangular shape close to a square, and the resulting plume has a spindle shape with the Y axis as the center. Therefore, it becomes a substantially circular shape in the top view. In the line irradiation of FIG. 1B according to the present invention, the laser beam is irradiated in a line shape. Here, the line shape means that the ratio b / a of the width (long side) b in the Z-axis direction and the width (short side) a in the X-axis direction of the irradiation range is 4 or more, preferably 6 or more. And The laser beam 33 is irradiated at an angle θ of 30 degrees or more in the side view. The plume 32 of FIG. 1B has two characteristics that the divergence angle α from the Y axis is large and the top end of the plume is flat compared to the plume 22 of FIG. Is shown in Of course, in the Z-axis direction in the top view, the plume range is expanded as the irradiation range is extended to b. Therefore, from FIG. 1B, the thin film formation region not only extends in the Z-axis direction but also extends in the X-axis direction. As a result, a substantially uniform film can be formed on the substrate by placing the substrate within a range of 45 degrees to the left and right from the Y axis in the side view. Therefore, compared with the point irradiation, the thin film formation region can be widened not only in the Z direction but also in the X direction, and a large area film can be formed.

  An example of a method for forming a line-shaped laser beam is shown in FIG. FIG. 2 shows a configuration of an optical system for irradiating a laser beam in a target shape with a top view and a side view. Assume that the output 40 of the pulse laser device to be used is a rectangular beam (rectangular beam). When such a beam is condensed by a single convex lens, so-called defocusing tends to occur due to factors such as different vertical and horizontal spreads of the rectangular beam. Further, it cannot be condensed into a desired shape by arbitrarily changing the aspect ratio. Therefore, the beam is condensed into a target shape by the two cylindrical lenses 42 and 43. The cylindrical lens 43 condenses the beam 40 in the direction seen from the top view and does not converge in the direction seen from the side view. On the other hand, the cylindrical lens 42 condenses the beam 40 in the direction seen from the side view and does not converge in the direction seen from the top view. In the combination of these two lenses, the focal length of each lens, that is, the condensing angle is arbitrarily selected to individually collect the vertical and horizontal directions of the rectangular beam, and the desired beam shape on the target, that is, the irradiation position. The width (a and b in FIG. 1) can be created. Here, when the shape of the beam output from the pulse laser is substantially circular, the line beam on the target has an elliptical shape. In this case, the major axis of the ellipse is b and the minor axis is a. It can be handled in the same way as the rectangular line shape shown in.

  Furthermore, a concave lens and a convex lens can be combined as a means for performing arbitrary light collection. FIG. 4 is a diagram for explaining the configuration, and shows one direction of the rectangular beam. The laser beam 50 is once expanded by the concave lens 51, and then condensed by the convex lens 52 and irradiated onto the target 53. This makes it possible not only to change the width of light collection, but also to arbitrarily design the distance from the lens to the target.

  FIG. 5 shows the application. In FIG. 5, the target 65 is disposed in the vacuum container 66. Since the pulse laser device is placed outside the vacuum vessel, the laser beam needs to be irradiated through an incident window 61 provided in the vacuum vessel 66. Here, according to the conventional condensing method, it is necessary to arrange the lens 62 in the vacuum container as shown in FIG. 5A depending on the size of the container and the degree of condensing. However, by using the optical system as described with reference to FIG. 4, the focal length is appropriately designed, so that the combined lens optical system of the concave lens 63 and the convex lens 64 is removed from the vacuum container as shown in FIG. It becomes easy to condense on the target. For the optical system design such as the selection of the lens, an appropriate one may be selected from the conditions such as the size of the vacuum vessel, the size of the laser beam, the focal length of the usable lens, the condensing size on the desired target, It is not particularly limited.

  FIG. 6 shows a method of manufacturing a thin film wire according to the present invention. Only a configuration in which a plurality of wires are fed into the thin film formation region will be described without showing a laser beam and an optical system. In FIG. 6, a region indicated by diagonal lines represents a thin film formation region generated on the target 71. The wire substrate 70 fed from the left side of the figure passes through the thin film formation region, and a thin film is formed on the substrate. The wire substrate is again fed into the thin film formation region by a feed mechanism constituted by two rollers 72 and 73, and a second thin film is formed. Similarly, after repeating the thin film formation from the third time (up to the fourth time in the figure), the thin film is sent out to the right side of the figure. In this way, a thick thin film can be efficiently formed by feeding the same wire substrate multiple times into the same thin film forming region generated from one target and repeating the thin film formation multiple times. This is particularly effective in the present invention in which the thin film formation region can be dramatically expanded as compared with the conventional manufacturing method.

  Apart from this configuration, a plurality of wire substrates can be fed in parallel to the same thin film formation region. In that case, efficient production by multiple simultaneous production and low-cost production by it are possible.

  An experimental example in which the present invention is implemented will be described with reference to FIG. FIG. 3B shows the implementation of the present invention, and FIG. 3A shows the implementation of a conventional example for comparison. The basic apparatus configuration is as shown in FIG. 6 described as a conventional example, and the contents of each are shown below.

[Comparative Example] A Kr-F excimer laser was used as a pulse laser. The laser output was a rectangle of 40 mm × 15 mm, and was condensed to 6 mm × 4 mm on the target surface by a lens. A HoBCO (HoBa ₂ Cu ₃ O _x ) target as a high-temperature superconductive material was irradiated with laser light at an energy of 20 W and an energy density of 3 J / cm ² to form a HoBCO film on a lanthanum aluminate substrate. Here, the film formation time was adjusted so that the film thickness was 0.5 μm. The shape of the plume generated at this time is as shown in FIG. 1A. The height of the plume tip is 80 mm from the target on the Y axis (normal line), and the plume radius at the Y axis 40 mm height position is 20 mm (width 40 mm). )Met.

Here, taking a measurement point on the X-axis direction and the Y-axis in the plume tip height as indicated by a ₇ from a ₀ in FIG. 3 (a), a superconducting thin film formed at a substrate at each location Table 1 shows the result of measuring the critical current density. On the Y axis, a thin film with better characteristics can be formed at the plume tip than in the plume, and a thin film with good characteristics can be obtained within a radius of about 4 cm at the plume tip height. .

[Example] A Kr-F excimer laser was used as a pulse laser. The laser output was a rectangle of 40 mm × 15 mm, and was condensed to 0.6 mm × 40 mm on the target surface by two cylindrical lenses. A HoBCO (HoBa ₂ Cu ₃ O _x ) target is irradiated with laser light at an energy of 20 W, an energy density of 3 J / cm ² , and an angle of 45 degrees so that the HoBCO film has a thickness of 0.5 μm on the lanthanum aluminate substrate. The film formation time was adjusted. The shape of the plume generated at this time is as shown in FIG. 1B. The position of the plume tip on the Y axis (normal line) is 60 mm from the target, and the tip has a substantially flat extension in the X axis direction. The axial width was about 60 mm.

Here, take the measurement points from b ₀ to the X-axis direction in the plume tip height as indicated by b ₈ in FIG. 3 (b), the critical current density of the superconducting thin film formed at a substrate at each location The results of measuring are shown in Table 2. It can be seen that the range in which a thin film with good characteristics can be obtained is larger than that of the comparative example. That is, when the level corresponding to the film formation at the plume tip position in the comparative example is considered as good film formation, in the example, good film formation is possible in a wide range up to the point b ₆ which is 60 mm in the X direction. is made of. This indicates that film formation in the range equivalent to the height at the plume tip height position or in the range of ± 45 degrees from the normal line with respect to the irradiation point is suitable. The plume can be satisfactorily formed in the Z-axis direction in the range of 40 mm which is the laser beam irradiation width + 20 mm on both sides which is the plume expansion, and 80 mm. Therefore, the thin film formation region covers an area of 4800 mm ² . This is about four times as large as the radius of 40 mm in the comparative example, that is, about 1200 mm ² .

It is a figure explaining the characteristic (b) of the manufacturing method of this invention compared with a prior art example (a). It is a figure explaining the method of the linear condensing of this invention. It is a figure explaining the Example (b) of this invention with the comparative example (a). It is a figure which illustrates the structure of the optical system which condenses a laser beam. It is a figure which shows the application of the optical system which condenses a laser beam. It is a figure which shows the manufacturing method of the thin film wire by this invention. It is a figure explaining the laser vapor deposition method as a prior art.

Explanation of symbols

10 Pulse laser 11, 23, 33, 40, 50, 60 Laser beam 12 Lens 13, 21, 31, 41, 53, 65, 71 Target 14, 22, 32 Plume 15 Substrate 42, 43 Cylindrical lens 51, 63 Concave lens 52 , 64 Convex lens 61 Entrance window 66 Vacuum container 70 Wire substrate 72, 73 Roller

Claims (7)

In a pulsed laser deposition method in which a thin film is formed on a substrate by depositing a target material that has been turned into plasma by irradiating the target with laser light.
The laser beam is collected in a line on the target,
When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface, the Z direction A method for producing a thin film, comprising: arranging the substrate in a thin film forming region in a range of 45 degrees from the Y axis as viewed from the Y axis.   2. The method of manufacturing a thin film according to claim 1, wherein the substrate is arranged in the vicinity of a height of a tip position of a plume generated in an upper portion of the target surface by laser light irradiation. In a pulsed laser deposition method in which a thin film is formed on a substrate by depositing a target material that has been turned into plasma by irradiating the target with laser light.
The laser beam is collected in a line on the target,
When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface, the Z direction From the Y axis to the thin film formation region in the range of 45 degrees positive and negative,
A method of manufacturing a thin film wire, comprising feeding a plurality of wire-like substrates in parallel. In a pulsed laser deposition method in which a thin film is formed on a substrate by depositing a target material that has been turned into plasma by irradiating the target with laser light.
The laser beam is collected in a line on the target,
When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface, the Z direction From the Y axis to the thin film formation region in the range of 45 degrees positive and negative,
A method for producing a thin film wire, characterized in that a wire-like substrate is repeatedly sent in multiple times. In a pulse laser deposition apparatus for forming a thin film on a substrate by depositing a target material that has been converted into plasma by irradiating the target with laser light,
Means for condensing the laser beam in a line on the target;
When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface, the Z direction A pulse laser deposition apparatus, wherein the substrate is disposed in a thin film forming region in a range of 45 degrees positive and negative from the Y axis as viewed from the top. In a pulsed laser deposition apparatus that forms a thin film on a substrate by depositing on the substrate a target material that has been turned into plasma by irradiating the target with laser light,
Means for condensing the laser beam in a line on the target;
When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface, the Z direction From the Y axis to the thin film formation region in the range of 45 degrees positive and negative,
A pulse laser deposition apparatus comprising means for feeding a plurality of wire-like substrates in parallel. In a pulsed laser deposition apparatus that forms a thin film on a substrate by depositing on the substrate a target material that has been turned into plasma by irradiating the target with laser light,
Means for condensing the laser beam in a line on the target;
When the origin is set at the center of the line-shaped laser beam at the irradiation position on the target and the Z axis is taken in the long side direction, the X axis is taken in the short side direction, and the Y axis is taken in the normal direction of the target surface, the Z direction From the Y axis to the thin film formation region in the range of 45 degrees positive and negative,
A pulse laser vapor deposition apparatus comprising means for repeatedly feeding a wire-like substrate a plurality of times.

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