JP2013079437A - Film forming method and film forming apparatus using laser ablation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology, by which a film having fewer droplets and fewer surface irregularities is formed on a substrate.SOLUTION: A film forming apparatus includes: a first laser source for ablation which emits pulsed laser beams for knocking out or evaporating constituent particles from a target; and a second laser source which emits continuous-wave laser beams for spot heating of or around the area where the first laser source performed convergent irradiation of laser beams on the target surface, outside a treatment container. Using the film forming apparatus, temperature of the target surface of and around the ablation area is raised by performing convergent irradiation of continuous-wave laser beams on the target surface from the second laser source through an irradiation window provided in the treatment container, and a film is formed on a substrate by performing convergent irradiation of pulsed laser beams on the ablation area from the first laser source through the irradiation window provided in the treatment container.

Description

  The present invention relates to a film forming method and a film forming apparatus using laser ablation.

  Pulsed laser deposition (PLD) is a thin film that irradiates a target material with a pulsed laser and deposits atoms, molecules or fine particles released from the target material by ablation (evaporation erosion). This is a fabrication technique and is applied to the fabrication of semiconductors and oxide superconducting thin films. In addition, when a thin film is produced from a target, there is little compositional deviation between the target and the thin film, so that the PLD method is superior to other thin film production processes when transferring a complicated chemical composition. .

The PLD method can not only transfer complex target compositions such as oxides, nitrides, and sulfides, but also has higher energy of atoms and molecules to be ablated than other film formation methods, so even if a metal target is used. It is suitable for producing high-quality thin films, and has the advantage that ceramic thin films such as oxides, nitrides, and sulfides can be produced from metal targets by controlling the film formation atmosphere. ing.
However, since the laser ablation process is caused by the vaporization phenomenon of the target material in the vicinity of the target surface, the liquid phase on the target surface is also blown to the substrate side, and coarse particles (droplets) adhere to the thin film. There's a problem. Since these droplets tend to deteriorate the properties of the thin film, how to suppress the generation of droplets is a problem in the PLD method.

  As a technique for reducing the influence of droplets on the above-described thin film, a target serving as a thin film source is installed on a target holder provided in a vacuum chamber, and a laser light source for irradiating the target with a laser beam is provided. A laser deposition apparatus in which a heating device for individual target heating is provided on a holding table is known. (See Patent Document 1)

JP-A-10-36959

The technique described in Patent Document 1 eliminates a local temperature difference between the inside and the surface of the target by heating the target from below to a desired temperature with a heater or a high-frequency heating coil. A thin film is formed by reducing only the temperature difference between the irradiated portion of the laser and the surrounding temperature, generating only fine particles, and depositing them on the substrate side.
However, in an apparatus for forming a thin film by laser ablation, in order to improve the utilization efficiency of the target or improve the quality of the obtained film, the laser beam should not be ablated repeatedly at the same position of the target during laser ablation. A mechanism for shifting the irradiation position of the laser beam on the target by reciprocating the target or rotating the target is provided.

In this way, in the laser vapor deposition apparatus equipped with a mechanism for shifting the irradiation position of the target, if a mechanism for heating the target from its lower side is provided, the target moving mechanism and the rotating mechanism bearings and shafts are easily damaged, This causes a problem that the aging of the device tends to progress. Therefore, in the PLD apparatus, there is a need for a structure in which only the target is heated and the other portions are not heated as much as possible.
Further, when considering the maintenance of the PLD apparatus, a mechanism capable of performing maintenance outside the apparatus is desired rather than complicating the internal structure of the apparatus. For example, a structure in which the target can be heated from the outside of the vacuum chamber, rather than being heated by a heater or lamp provided in the vacuum chamber is preferable.

  The present invention has been made in view of the above-described conventional situation, adopts a configuration in which only the target inside the apparatus can be partially heated from the outside of the apparatus, and facilitates maintenance of the apparatus. It is an object of the present invention to provide a film forming method and a film forming apparatus using laser ablation in which a bumping phenomenon in a laser beam irradiation portion on the surface is suppressed and droplets are prevented from being generated on a thin film.

  In order to solve the above-described problems, the present invention provides a film forming method in which laser light is focused on a target surface and constituent particles of the target are knocked out or evaporated to deposit the constituent particles of the target on a substrate. A first laser light source for ablation that emits a pulsed laser beam that strikes or evaporates constituent particles from the target, and the first laser light source focuses the laser beam on the surface of the target. Using a film forming apparatus having an irradiation region and a second laser light source that emits continuous wave laser light that spot-heats the periphery of the region outside the processing container, the second laser light source is applied to the surface of the target. A continuous wave laser beam is condensed and irradiated through an irradiation window provided in the processing vessel to add the target surface in the ablation region and its peripheral region. At the same time, pulsed laser light is condensed and irradiated from the first laser light source to the ablation region through the irradiation window provided in the processing container, and the constituent particles of the target are knocked out or evaporated to form a film on the substrate. It is characterized by doing.

A film of target constituent particles can be formed on a substrate by knocking or evaporating target constituent particles from the surface of the target with a pulsed laser beam from a first laser light source. At this time, since the pulsed laser light alternately repeats a high energy state and a state without energy, if a liquid phase is generated on the target surface, the laser light in the high energy state causes bumping in the liquid phase portion. It may be blown away.
In this regard, even if the intense energy of the pulsed laser beam is transmitted from the irradiation area of the target surface to the deep part or the peripheral part, and a bumping occurs in these parts, the continuous wave laser beam from the second laser light source However, since the target irradiation region and its peripheral region are always heated in advance to reduce the temperature difference, the occurrence of bumping in the laser ablation region can be suppressed, and the coarse particles can be prevented from jumping out to the substrate side.

In addition, regarding the cracking and peeling of the target caused by irradiating the target with pulsed laser light from the first laser light source, a continuous wave laser from the second laser light source is irradiated around and around the irradiated part of the pulsed laser light. Since light is suppressed by heating, droplets generated in the film in the prior art due to cracking or peeling of the target can also be suppressed.
Further, since the liquid phase portion generated on the target surface is constantly heated by the continuous wave laser beam from the second laser light source, coarse particles that are about to jump out of the liquid phase portion generated on the target surface are emitted from the second laser light source. It is possible to always sublimate with a continuous wave laser beam.
By these combined effects, a smooth and uniform film free from irregularities due to droplets can be generated in the film formed on the substrate.

In order to solve the above problems, the present invention uses a target for generating an oxide superconductor on a base material having a laminated structure including a metal base body and an intermediate layer formed on the base body. Then, the target surface is spot-heated by condensing and irradiating infrared continuous-wave laser light from the second laser light source, and pulsed from the first laser light source to the ablation region inside the spot heating region. In this case, the oxide superconducting layer is formed on the intermediate layer by condensing and irradiating the laser beam and ejecting or evaporating the constituent particles from the target.
It is possible to obtain an oxide superconducting conductor having a smooth oxide superconducting layer with few surface irregularities on the surface above which no droplets are formed. If it is a smooth oxide superconducting layer having no droplets, it has excellent crystal orientation and superconducting properties.

In order to solve the above problems, the present invention is characterized in that the target surface is heated to 360 to 630 ° C. by continuous wave laser light from the second laser light source.
When the temperature of the target is higher than the above range, the laser power threshold required for ablation decreases, the deposition amount increases, and the supersaturation degree increases and the film quality tends to decrease as the deposition amount increases. Further, if the target is heated too much, compositional deviation may become remarkable.

  In order to solve the above problems, the film forming apparatus of the present invention condenses and irradiates the surface of the target with laser light, knocks out or evaporates the constituent particles of the target, and deposits the constituent particles of the target on the substrate. A film forming apparatus for storing the target; and a first container that is provided outside the processing container and emits pulsed laser light for ablation that strikes or evaporates constituent particles from the target. And a first laser light source that emits a continuous wave laser beam that spot-heats a region where the laser beam is focused and irradiated on the surface of the target. An irradiation window that transmits the pulsed laser light from the first laser light source to the processing container; Characterized in that a radiation window which transmits a continuous wave laser beam from the second laser light source.

A film of target constituent particles can be formed on a substrate by knocking or evaporating target constituent particles from the surface of the target with a pulsed laser beam from a first laser light source.
At this time, since the pulsed laser light alternates between a high energy state and a state without energy, if the heat on the target surface diffuses inside the target and the liquid phase part bumps inside the target, the target surface melts. There is a possibility that the portion may be blown off and adhered to the film as a droplet.
In this regard, even if the intense energy of the pulsed laser beam is transmitted from the irradiation area of the target surface to the deep part or the peripheral part, and a bumping occurs in these parts, the continuous wave laser beam from the second laser light source However, since the target irradiation region and its peripheral region are always heated in advance to reduce the temperature difference, the occurrence of bumping in the laser ablation region can be suppressed, and the coarse particles can be prevented from jumping out to the substrate side.

In addition, coarse particles that are about to jump out of the liquid phase portion generated on the target surface can be sublimated by continuous wave laser light from the second laser light source. By these, in the film | membrane formed on a base material, the production | generation of a droplet can be suppressed and the smooth film | membrane without the unevenness | corrugation resulting from a droplet can be produced | generated.
The film forming apparatus condenses and irradiates the target in the processing container with the pulsed laser light from the first laser light source through the first irradiation window, and from the second laser light source through the second irradiation window. The continuous wave laser beam can be focused and irradiated on the target in the processing container. Since all of these laser beams can heat only the target surface in the processing container from the outside of the processing container, the temperature of the equipment provided in the processing container, for example, the mechanical parts constituting the support mechanism of the target and the substrate is controlled. Since it is not raised, there is no adverse effect on the life and performance of the support mechanism.

In order to solve the above problems, the film forming apparatus of the present invention is characterized in that the second laser light source is a laser light source that emits continuous wave laser light in an infrared region.
If it is a continuous wave laser beam in the infrared region, the spot region on the target surface can be reliably heated, and coarse particles that attempt to jump out from the liquid phase portion generated on the target surface are continuously emitted from the second laser light source. Sublimation with wave laser light is possible.

In order to solve the above problems, in the film forming apparatus of the present invention, the substrate support mechanism includes a supply reel on which a tape-shaped base material is mounted, a take-up reel that winds the tape-shaped base material, the supply reel, A plurality of turning reels provided between the take-up reels are provided, and the plurality of turning reels oppose a target mounted on the target holder with a tape-like substrate supplied therebetween. It is characterized by being arranged in a lane shape.
While the tape-like substrate is moved in a lane shape between the plurality of turning reels, the constituent particles from the target can be deposited to form a film over the entire length of the tape-like substrate.

  According to the present invention, a target constituent particle film can be formed on a substrate by striking or evaporating target constituent particles from the target surface with a pulsed laser beam from a first laser light source. At this time, since the position irradiated with the pulsed laser beam and its periphery can be continuously heated by the continuous wave laser beam from the second laser light source, the temperature difference between the portion irradiated with the pulsed laser beam and the surrounding portion can be determined. It can be made small, the scattering of coarse particles due to bumping, which causes the generation of droplets, can be suppressed, and the generation of droplets due to cracking or peeling of the target can also be suppressed. Therefore, in the film formed on the base material, it is possible to generate a high-quality film having a smooth surface free from irregularities due to droplets.

1 is a front view showing a schematic configuration of a film forming apparatus according to a first embodiment of the present invention. The side view which shows schematic structure of the film-forming apparatus shown in FIG. The perspective view which shows the principal part of schematic structure of the film-forming apparatus shown in FIG. The perspective view which shows an example structure of the oxide superconducting conductor made into object when forming into a film with the film-forming apparatus shown in FIG. The electron micrograph which shows the surface state of the thin film sample obtained in the Example. The electron micrograph which shows the surface state of the thin film sample obtained in the comparative example. The front view which shows schematic structure of the film-forming apparatus of 2nd Embodiment which concerns on this invention.

Hereinafter, embodiments in which a film forming method and a film forming apparatus according to the present invention are applied to a thin film for an oxide superconducting conductor will be described with reference to the drawings.
1 is a front view showing a schematic configuration of a film forming apparatus according to a first embodiment of the present invention, FIG. 2 is a side view showing the schematic configuration of the film forming apparatus, and FIG. 3 shows a main part of the film forming apparatus. It is a perspective view. FIG. 4 shows an example structure of the oxide superconducting conductor 1 to be manufactured using the film forming apparatus A of the present embodiment shown in FIGS.
The oxide superconducting conductor 1 of this example has a diffusion prevention layer 3, an intermediate layer 4, a cap layer 5, an oxide superconducting layer 6 and a stabilizing layer 7 laminated in this order above a tape-shaped base body 2. Become. The oxide superconducting conductor 1 is used as an oxide superconducting wire by covering its peripheral surface with an insulating coating layer (not shown).

  The base body 2 applied to the oxide superconducting conductor 1 can be used as a base body of a normal oxide superconducting conductor and has only to be high strength. It is preferably in the form of a sheet or thin plate, and is preferably made of a heat-resistant metal. Examples thereof include various heat-resistant metal materials such as nickel alloys such as hastelloy. Among various refractory metals, a nickel alloy is preferable. Especially, if it is a commercial item, Hastelloy (trade name made by US Haynes Co., Ltd.) is suitable. Any type can be used. An oriented base material body such as a Ni-W alloy in which a texture is introduced into a Ni alloy may be used. What is necessary is just to adjust the thickness of the base-material main body 2 suitably according to the objective, Usually, it can be set as the range of 10-500 micrometers.

The diffusion preventing layer 3 has a function of preventing the elements constituting the base body 2 from diffusing to the upper oxide superconducting layer 6 side. Thereby, characteristic deterioration of the oxide superconducting layer 6 and the like due to the diffusing element can be suppressed.
A bed layer may be provided between the diffusion preventing layer 3 and the intermediate layer 4. The bed layer has high heat resistance and is used for reducing interfacial reactivity, and is used for obtaining the orientation of a film disposed thereon. Such a bed layer is, for example, a rare earth oxide such as yttria (Y ₂ O ₃ ), and is exemplified by a compositional formula (α ₁ O ₂ ) _2x (β ₂ O ₃ ) _(1-x). it can. More specifically, Er ₂ O ₃ , CeO ₂ , Dy ₂ O ₃ , Er ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O ₃ , La ₂ O _{3 and the} like can be exemplified, and from these materials It may be a single layer structure or a multilayer structure. The bed layer is formed by a film forming method such as a sputtering method, and has a thickness of 10 to 100 nm, for example. Further, since the crystallinity of the bed layer is not particularly limited, it may be formed by a film forming method such as a normal sputtering method.

The intermediate layer 4 controls the crystal orientation of the oxide superconducting layer 6 and prevents diffusion of the metal element in the base body 2 into the oxide superconducting layer 6. Furthermore, it functions as a buffer layer that alleviates the difference in physical properties (thermal expansion coefficient, lattice constant, etc.) between the substrate body 2 and the oxide superconducting layer 6, and the material has physical properties different from those of the substrate body 2. A metal oxide showing an intermediate value with the oxide superconducting layer 6 is preferable. Specifically, preferred materials for the intermediate layer 4 include Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd _2. Examples thereof include metal oxides such as O ₃ , Zr ₂ O ₃ , Ho ₂ O ₃ , and Nd ₂ O ₃ .
The intermediate layer 4 may be a single layer or a multilayer structure. For example, the metal oxide layer (metal oxide layer) is preferably formed by an IBAD method (ion beam assisted vapor deposition method) or the like and has a crystal orientation. The outermost layer (the layer closest to the oxide superconducting layer 6) preferably has at least crystal orientation.

The cap layer 5 is epitaxially grown on the surface of the intermediate layer 4, and then undergoes a process of grain growth (overgrowth) in the lateral direction (plane direction), and crystal grains are selectively grown in the in-plane direction. Those formed are preferred. Such a cap layer 5 may have a higher degree of in-plane orientation than the intermediate layer 4.
The material of the cap layer 5 is not particularly limited as long as it can exhibit the above functions, but specific examples of preferable materials include CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , and Zr _2. Examples thereof include O ₃ , Ho ₂ O ₃ and Nd ₂ O ₃ . When the material of the cap layer 5 is CeO ₂ , the cap layer may include a Ce—M—O-based oxide in which part of Ce is substituted with another metal atom or metal ion.

The cap layer 5 can be formed by a PLD method (pulse laser deposition method), a sputtering method, or the like, but it is preferable to use the PLD method from the viewpoint of obtaining a high film formation rate. The film formation conditions for the CeO ₂ layer by the PLD method can be performed in an oxygen gas atmosphere at a substrate temperature of about 500 to 1000 ° C. and about 0.6 to 100 Pa. In order to form the cap layer 5, in this embodiment, the cap layer 5 can be formed by a PLD method, which will be described later, using a film forming apparatus A having a configuration described later. Of course, the cap layer 5 may be formed by a film forming method other than the PLD method.
The thickness of the CeO ₂ cap layer 5 may be 50 nm or more, but is preferably 100 nm or more in order to obtain sufficient orientation. However, if it is too thick, the crystal orientation deteriorates, so that it can be in the range of 50 to 5000 nm, more preferably in the range of 100 to 5000 nm.

The oxide superconducting layer 6 can be widely applied to an oxide superconductor having a generally known composition, such as REBa ₂ Cu ₃ O _y (RE is Y, La, Nd, Sm, Er, Gd, etc. of a material consisting represents a rare earth element), specifically, it can be exemplified Y123 (YBa2Cu3Oy) or _{Gd123 (GdBa 2 Cu 3 O y} ). Further, other oxide superconductors, for _{example, Bi 2 Sr 2 Ca n-} 1 Cu n for _{O 4 + 2n + δ} becomes may be used in compositions such as those made of other oxide superconductors having high critical temperatures representative Of course.
In the present embodiment, the oxide superconducting layer 6 can be formed by a PLD method to be described later using a film forming apparatus A having a configuration described later. The oxide superconducting layer 6 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

  The stabilization layer 7 formed so as to cover the upper surface of the oxide superconducting layer 6 is made of Ag and is formed by a vapor phase method such as a sputtering method, and its thickness is set to about 1 to 30 μm. . A second stabilization layer (not shown) may be provided on the stabilization layer 7. The second stabilization layer is made of a highly conductive metal material, and functions as a bypass for commutating current together with the stabilization layer 7 when the oxide superconducting layer 6 transitions from the superconducting state to the normal conducting state. The metal material composing the second stabilization layer is not particularly limited as long as it has good conductivity, but copper alloys such as copper, brass (Cu—Zn alloy), Cu—Ni alloy, stainless steel, etc. It is preferable to use a material made of a relatively inexpensive material, such as copper. Among them, copper is preferable because it has high conductivity and is inexpensive. When the oxide superconducting conductor 1 is used for a superconducting fault current limiter, the second stabilization layer is made of a high resistance metal material, and for example, a Ni-based alloy such as Ni—Cr can be used. The thickness of the second stabilizing layer is not particularly limited and can be adjusted as appropriate, but is preferably 10 to 300 μm.

In the present embodiment, the cap layer 5 or the oxide superconducting layer 6 of the oxide superconducting conductor 1 can be manufactured by using a film forming apparatus A described below.
The film forming apparatus A of the present embodiment directs a jet (plume) of constituent particles struck or evaporated from the target 11 by laser light onto the substrate body, and forms a thin film on the substrate body by deposition of the constituent particles. This is an apparatus for performing a laser vapor deposition method (PLD method).
In the film forming apparatus A of the present embodiment, the cap layer 5 is formed on the base body 2 from the state where the intermediate layer 4 is formed, and the oxide superconducting layer 6 is formed on the cap layer 5. It can be used for either or both of film formation.

As shown in FIGS. 2 and 3, the film forming apparatus A includes a traveling device 10 for traveling the tape-shaped base body 2 in the longitudinal direction thereof, and a target 11 installed below the traveling device 10. As shown in FIG. 1 for irradiating the target 11 with laser light, a first laser light source 12 and a second laser light source 13 provided outside the processing container (vacuum chamber) 18 are provided.
The traveling device 10 includes, for example, turning member groups 16 and 17 that are aggregates of turning reels for guiding the tape-like base body 2 that travels along the film forming region 15, and these turning member groups. 16 and 17 is configured as an apparatus capable of guiding the substrate body 2 so as to form a plurality of lanes of the substrate body 2 in the film forming region 15 around the substrate body 2.

  The traveling device 10 and the target 11 are accommodated in a processing container 18, and the processing container 18 is a container that partitions the outside and the film formation space, has airtightness, and has a high vacuum inside. Therefore, the structure has pressure resistance. An exhaust means 19 for exhausting the gas in the processing container is connected to the processing container 18, and in addition, a gas supply means for introducing a carrier gas and a reactive gas is formed in the processing container. The supply means is omitted, and only the outline of each device is shown.

  The base body 2 is wound around a supply reel 20 provided inside the processing vessel 18 so that the necessary length can be fed out. The substrate body 2 fed out from the supply reel 20 is alternately turned into a turning member group 16 in which a plurality of turning reels 16a are coaxially arranged adjacently and a turning member group 17 in which a plurality of turning reels 17a are arranged coaxially adjacently. After being wound and disposed so as to form a plurality of lanes between the turning member groups 16 and 17, they are drawn out from the turning member group 17 and wound around the take-up reel 21.

Further, turning member groups 16 and 17 and a rectangular box-shaped heater box 23 surrounding the periphery thereof are provided inside the processing container 18, and the base body 2 fed out from the supply reel 20 is an inlet portion 23 a of the heater box 23. The base body 2 pulled out from the turning member group 17 is wound on the take-up reel 21 side through the outlet 23b of the heater box 23. ing. The heater box 23 is provided in the apparatus of the present embodiment in order to control the temperature of the film forming region 15, but the heater box 23 may be omitted.
A target 11 is provided below an intermediate position between the turning member groups 16 and 17. The target 11 is mounted on and supported by the target holder 25. The target holder 25 is rotatably supported by a support rod 26 attached to the center of the lower surface thereof, and is further shown in FIG. 2 by a reciprocating mechanism (not shown). It is supported so as to be able to reciprocate horizontally in the Y ₁ and Y ₂ directions. By the rotational movement and reciprocation of the target holder 25 by these mechanisms, the position of the laser beam irradiated onto the surface of the target 11 can be changed as appropriate as will be described later.

  On the lower surface of the heater box 23 above the target 11, an opening 23 c is formed between the turning member groups 16 and 17 so as to correspond to the width of the traveling lane formed by the base body 2. Further, in the heater box 23, a heating device 27 such as a hot plate is disposed inside the opening 23c, and the base body 2 that travels in a plurality of lanes between the turning member groups 16 and 17 is disposed on the back surface thereof. It can be heated to a desired temperature from the side. The heating device 27 may be of any configuration as long as it can heat the base body 2 from the rear surface side, but a general heater composed of a metal disk incorporating a current-carrying electric heater can be used. .

When the cap layer 5 is formed as the target 11, a plate material of an oxide sintered body such as CeO ₂ constituting the cap layer 5 can be used.
When the oxide superconducting layer 6 is formed, the target 11 is composed of a composite oxide that has the same or approximate composition as the oxide superconducting layer 6 to be formed, or a complex oxide that contains many components that easily escape during film formation. A plate material such as a sintered body or an oxide superconductor can be used. Therefore, the target of the oxide superconductor is RE-123 series oxide superconductor (REBa ₂ Cu ₃ O _7-x : RE is a rare earth element such as Y, La, Nd, Sm, Eu, Gd) or the like. A material having the composition described above can be used. The RE-123-based oxide is preferably Y123 (YBa ₂ Cu ₃ O _7-x ) or Gd123 (GdBa ₂ Cu ₃ O _7-x ), but other oxide superconductors such as Bi _2. It is preferable to use the same composition as that of an oxide superconductor having a high critical temperature represented by a composition such as Sr ₂ Ca ₂ Cu ₃ O _y or a similar composition.

  As shown in FIG. 1, in the processing container 18, a first irradiation window 30 is formed on the side wall 18 </ b> A on one side of the target 11 with the target 11 as the center so as to face the target 11, and the target 11 on the side wall 18 </ b> B on the other side. A second irradiation window 31 is formed so as to face. The first laser light source 12 for ablation is disposed outside the first irradiation window 30 via a condensing lens 32 and a reflecting mirror 33, and the condensing lens 34 is disposed outside the second irradiation window 31. A second laser light source 13 for heating the target is disposed.

The first laser light source 12 for ablation may be a laser light source that exhibits a good energy output as a pulse laser, such as an excimer laser or a YAG laser. As the output of the first laser light source 12, for example, a laser light source having an energy density of about 1 to 5 J / cm ² can be used.
The second laser light source 13 for heating can squeeze the continuous wave laser light for heating to a range of about 2 mm to 10 mm with a condenser lens like an infrared laser, and the target surface is about 200 ° C. to 800 ° C. Those that can be spot-heated in the range of are used. As the laser light source 13 for the continuous wave laser beam in the infrared region, a laser light source capable of adjusting the output up to about 10 to 100 W, for example, can be used.
In the film forming apparatus A shown in FIG. 1, an infrared radiation thermometer 36 for measuring the temperature of the laser light irradiation region on the target surface is installed inside the processing container 18 and obliquely above the target 11. Has been.

In order to form the cap layer 5 or the oxide superconducting layer 6 using the film-forming apparatus A having the above-described structure, the diffusion prevention layer 3 and the intermediate layer 4 have been described above on the tape-shaped base body 2. Various tape-shaped substrates formed by the film-forming method, or tape-shaped substrates formed by the various film-forming methods described above on the substrate body 2 up to the diffusion preventing layer 3, the intermediate layer 4, and the cap layer 5. A substrate is used.
After these tape-shaped base materials are wound around the take-up reel 21 from the supply reel 20 via the turning member groups 16 and 17 as shown in FIG. 2 or FIG. 3, and the target 11 is mounted on the target holder 25 Then, the inside of the processing container 18 is depressurized. After reducing the pressure to a target pressure, the surface of the target 11 is focused and irradiated with pulsed laser light from the first laser light source 12, and a continuous wave laser light for heating is applied from the second laser light source 13 to the surface of the target 11. Condensed and irradiated. When continuous wave laser light is focused and irradiated from the second laser light source 13 onto the surface of the target 11, the continuous wave laser light is collected in a wider area surrounding the focused irradiation area from the first laser light source 12. The continuous wave laser light from the second laser light source 13 is condensed and irradiated so that the light can be irradiated. The focused spot diameter of each laser beam can be achieved by adjusting the condenser lenses 32 and 34.

For example, as an example, the pulsed laser light from the first laser light source 12 is focused and irradiated onto a spot diameter of 20 μm to 50 μm, and the continuous wave laser light from the second laser light source 13 is about 5 mm to 20 mm. The spot diameter can be focused and irradiated.
When the first laser light source 12 is used to collect and radiate laser light having an energy density of about 0.5 to 50 J / cm ² that can generate a plume suitable for film formation from the target 11, the second laser light source 13 is used. It is preferable to set the surface of the target 11 to a spot width that can be heated to, for example, about 360 to 630 ° C. with an infrared continuous wave laser.
When the heating temperature of the target 11 is higher than the above range, the threshold of laser power necessary for ablation decreases, the deposition amount increases, and as the deposition amount increases, the degree of supersaturation increases and the film quality tends to decrease. Moreover, when the target 11 is heated too much, the compositional deviation of the film may become remarkable. When the heating temperature of the target 11 is less than 360 ° C., the film becomes rich in droplets, so that the characteristics may be rapidly deteriorated.

When the pulsed laser beam from the first laser light source 12 is condensed and irradiated on the surface of the target 11, the constituent particles on the surface portion of the target 11 are beaten or evaporated to jet the constituent particles from the target 11 (plume). 29, and the cap layer 5 or the oxide superconducting layer 6 can be formed by depositing the target particles above the tape-like substrate body 2 running in a lane shape.
In addition, the pulsed laser light from the first laser light source 12 is condensed and irradiated, and at the same time, the continuous heating for heating from the second laser light source 13 so as to surround the pulsed laser light condensing irradiation region and its surroundings. By condensing and irradiating the wave laser beam, the focused irradiation region of the pulsed laser beam and the target 11 in the surrounding area are heated.

When a plume 29 is generated by condensing and irradiating the surface of the target 11 with a pulsed laser beam from the first laser light source 12, droplets are generated in the film generated above the base body 2 In the ablation process, the heat of the target surface generated by the irradiation of the laser light diffuses inside the target 11 and bumps (expands) inside the target, so that coarse particles near the surface are blown off to form a film as a droplet. It can be presumed that the cause is taken in. In addition, since the temperature difference between the ablation region and the peripheral region becomes large, the target 11 is cracked, chipped, or peeled off, and as a result, the film is mixed with droplets and fragments. it is conceivable that.
Therefore, by raising the target temperature before ablation, the temperature difference between the target surface and the interior during ablation, or the temperature difference between the surrounding parts can be reduced, preventing bumping, Peeling can also be prevented.

In view of these points, the range of about 2 to 4 cm is heated to a range of 360 to 630 ° C. with respect to a region where the pulsed laser light from the first laser light source 12 is focused and irradiated on the surface of the target 11. As a result, the above-described bumping, peeling, and peeling can be more reliably prevented, the unevenness caused by the droplets generated in the film can be reduced, and a smooth film can be obtained.
If this film is the cap layer 5, it can be made a film having excellent surface orientation and no surface irregularities, so that the crystal orientation of the oxide superconducting layer 6 formed thereon can be improved. The superconducting properties of the oxide superconducting layer 6 can be improved.
In addition, when the above-described smooth film is the oxide superconducting layer 6, the oxide superconducting layer 6 exhibiting excellent superconducting characteristics on the cap layer 5 can be obtained.

In addition, when irradiating the surface of the target 11 with pulsed laser light from the first laser light source 12 and continuous wave laser light from the second laser light source 13, a plume 29 composed of uniform fine particles is always generated. In addition, the target 11 can be moved by combining the rotational movement of the target holder 25 and the reciprocating back and forth movement, and the film can be operated while sequentially scanning each laser beam over the entire surface of the target 11.
Since the tape-shaped base body 2 is long, in order to form a homogeneous film over the entire length direction, the above-described rotational movement or reciprocating back-and-forth movement operation of the target 11 is required. Therefore, a mechanism for rotationally driving the target holder 25 or moving back and forth is provided inside the processing apparatus 18 (not shown), but both the first laser light source 12 and the second laser light source 13 are processing containers. 18 is configured to irradiate the target 11 in the processing container 18 with laser light through the irradiation windows 30 and 31, so that these rotational driving mechanisms and reciprocating mechanisms in the processing container 18 are provided. The laser light has no extra heating.
Accordingly, the mechanical parts such as shafts and bearings provided in the rotary drive mechanism and the reciprocating mechanism are not heated excessively, so that these mechanisms are not damaged by heat, and the life and performance of these mechanical parts are not adversely affected. .

  When irradiating the surface of the target 11 with a pulsed laser beam and a continuous wave laser beam for heating while scanning, the target 11 is not moved by an optical system moving operation such as a reflecting mirror or a condenser lens. The irradiation position of the pulsed laser beam and the heating continuous wave laser beam may be moved on the target, and the entire surface of the target 11 may be irradiated sequentially to form a film. In this case, the irradiation position of both laser beams is moved synchronously while irradiating the pulsed laser beam and the continuous wave laser beam for heating to the same position on the surface of the target 11, thereby moving the entire area of the surface of the target 11. The target material can be efficiently used to generate a plume for a long time, and can be used for film formation in the entire length direction of a long tape-shaped substrate. In addition, a groove is dug as a trace after the constituent particles are blown in the portion irradiated with the laser beam of the target 11. When the constituent particles are blown by irradiating the portion of the groove with the laser light again, the obtained film is formed. Since there is a risk of composition shift and film quality deterioration, it is preferable to scan and use the entire surface of the target 11 as described above.

In the present embodiment, the example in which the film forming method and the film forming apparatus according to the present invention are applied to the film formation of the cap layer 5 and the oxide superconducting layer 6 of the oxide superconducting conductor 1 has been described. It goes without saying that the film forming method and the film forming apparatus can be used for forming a film on a substrate such as a semiconductor substrate.
For example, instead of the film forming apparatus A having the configuration shown in FIG. 1, the film forming method according to the present invention can be carried out using the film forming apparatus B shown in FIG.
A film forming apparatus B shown in FIG. 7 is configured by omitting the traveling apparatus 10 provided in the film forming apparatus A of the previous form, and configured so that the substrate 40 can be mounted on the bottom surface of the heating apparatus 27. Device. Other configurations are the same as those of the film forming apparatus A of the previous embodiment.

  As in the film forming apparatus B shown in FIG. 7, the constituent particles are knocked out or evaporated from the target 11 using the laser beams from the first laser light source 12 and the second laser light source 13 to form a film on the substrate 40. Even in this case, as in the case of the film forming apparatus A described above, a film having a smooth surface with few droplets can be obtained as a film that can be formed on the substrate 40.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.
"Example 1"
A diffusion prevention layer (thickness 80 nm) of amorphous Al ₂ O ₃ is formed on a tape-shaped base body having a width of 10 mm, a thickness of 0.1 mm, and a length of 100 mm made of Hastelloy C-276 (trade name of Haynes, USA). , Y ₂ O ₃ bed layer (thickness 30 nm), MgO intermediate layer (thickness 10 nm) by ion beam assisted deposition, and LaMnO ₃ cap layer (thickness 300 nm) by PLD method A shaped substrate was prepared.

Next, an epi-Y ₂ O ₃ layer was formed on the cap layer. (The epi-Y ₂ O ₃ layer means a Y ₂ O ₃ layer having the same orientation as that of the cap layer grown epitaxially with respect to the cap layer as the underlayer.) The epi-Y ₂ O ₃ layer is 1 to 3, an excimer laser (KrF: 248 nm) is used as the first laser light source for ablation, and an energy density of 3.0 J / cm ² (150 mJ) is used. ), TS (distance between target base materials): 5.5 cm, linear velocity 8 m / h when moving the tape base material, pulse laser repetition frequency 200 Hz, oxygen partial pressure PO ₂ = 20 mTorr of processing vessel, hot plate The tape-shaped substrate was heated under the conditions of a heating temperature of 900 ° C. The laser for heating the target used continuous wave laser light in the infrared region (wavelength: 808 nm), and the spot diameter was set to 15 mm by narrowing the laser light with a condenser lens. The surface temperature of the target (Y ₂ O ₃ plate material) was measured with an infrared radiation thermometer provided inside the processing container.

  In this embodiment, since the optical axis of the first laser light source for ablation is fixed, the ablation position of the target is shifted only by the rotational movement (spinning) of the target and the reciprocating horizontal movement, and the target becomes uneven. The position was adjusted so that it was not ablated. Therefore, the temperature rise also changes depending on the rotation speed and the reciprocating horizontal movement speed of the target. Therefore, an optimum laser beam output may be selected according to the temperature rise. For example, an infrared laser beam having an output of 100 W or more may be used. Absent. In addition, when the pulse laser beam for ablation is scanned by a reflection mirror, the laser beam for heating from the second light source is scanned and the laser beam for ablation from the first light source is reflected by the mirror. The ablation position may be heated by scanning the heating laser beam.

In Table 1 below, when an infrared laser light source for heating is used, the target temperature at the center of the spot of the heating laser beam and the surface roughness of the deposited Y ₂ O ₃ thin film (the droplets present on the surface) Avoiding measurement in the range of 10 × 10 nm ² ) and the number of droplets, and when YBCO thin film (YBa ₂ Cu ₃ O _7-x superconducting layer) is vapor-deposited by PLD under the same conditions on the formed Y ₂ O ₃ thin film The results of measuring the crystallinity and superconducting properties of the oxide superconducting layer are shown.
The sample on which the YBCO thin film was formed was subjected to oxygen annealing in a furnace at 500 ° C. for 10 hours, then cooled in the furnace and taken out to obtain an oxide superconducting conductor.

In this example, the temperature at the time of film formation slightly increases without using the heating laser beam due to the heat of the hot plate provided in the film forming apparatus. By heating to the peripheral region, the number of droplets of the epi-Y ₂ O ₃ layer was reduced, and the surface of the epi-Y ₂ O ₃ layer was planarized.
In addition, since the superconducting properties and crystallinity of the YBCO thin film formed thereon are also improved, in addition to pulsed laser light, heat treatment with a continuous wave laser for heating is performed using an epi-Y ₂ O ₃ layer. In the case of forming a film, it has been found that any of the cases where an oxide superconducting layer is formed thereon has a great effect.
In addition, from the test result shown in Table 1, when irradiating a continuous wave laser beam in the infrared region from the second laser light source, the surface temperature with a small number of droplets is set by setting the target temperature in the range of 360 ° C. to 630 ° C. It can be seen that a Y ₂ O ₃ film having a small RMS value can be formed, and in this case, a YBCO layer having a high critical current density and good crystal orientation can be produced.
This is because if the heating temperature of the target is lower than the above range, it is assumed that the heating effect by the laser light emitted from the second laser light source is small, and conversely, if the target temperature is higher than the above range, it is necessary for ablation. It can be assumed that the laser power threshold decreased, the deposition amount increased, and the degree of supersaturation increased and the film quality tended to decrease as the deposition amount increased. Further, if the target is heated too much, the compositional deviation of the film may become remarkable.

FIG. 5 shows a SEM photograph image of the surface of the Y ₂ O ₃ layer obtained in the sample No. 6 shown in Table 1, and FIG. 6 shows Y ₂ obtained in the sample No. 1 shown in Table 1. It shows a SEM photograph of the surface of the O ₃ layer.
As apparent from the comparison between FIG. 5 and FIG. 6, the surface of the Y ₂ O ₃ layer of the sample formed while irradiating the continuous wave laser beam for heating is clearly smooth, whereas the continuous for heating A state in which innumerable irregularities due to innumerable droplets are formed on the surface of the Y ₂ O ₃ layer of the sample formed without irradiating the wave laser beam is shown.

  INDUSTRIAL APPLICABILITY The present invention can be used to form a high-quality film that can be used as an oxide superconducting conductor used in various power devices such as a superconducting power transmission line, a superconducting motor, and a current limiter.

  A, B ... film forming apparatus, 1 ... oxide superconducting conductor, 2 ... base material body, 3 ... diffusion preventing layer, 4 ... intermediate layer, 5 ... cap layer, 6 ... oxide superconducting layer, 7 ... stabilization layer, DESCRIPTION OF SYMBOLS 10 ... Conveyance apparatus, 11 ... Target, 12 ... 1st laser light source, 13 ... 2nd laser light source, 15 ... Film-forming area | region, 16 ... Turning member group, 16a ... Turning reel, 17 ... Turning member group, 17a ... Turning reel, 18 ... processing vessel, 18A, 18B ... side wall, 19 ... exhaust device, 20 ... supply reel, 21 ... take-up reel, 23 ... heater box, 25 ... target holder, 29 ... plume (jet), 30, 31 ... irradiation window, 40 ... substrate.

Claims (6)

A film forming method of condensing and irradiating the surface of a target with a laser beam, striking or evaporating constituent particles of the target, and depositing the constituent particles of the target on a substrate, wherein the constituent particles are hit from the target A first laser light source for ablation that emits pulsed laser light to be emitted or evaporated, a region in which the first laser light source condenses and irradiates laser light onto the surface of the target, and a periphery of the region are spot-heated Using a film forming apparatus equipped with a second laser light source that emits continuous wave laser light outside the processing container,
At the same time, the target laser in the ablation region and its peripheral region is heated by condensing and irradiating continuous wave laser light from the second laser light source to the surface of the target through an irradiation window provided in the processing container. A laser characterized in that a pulsed laser beam is focused and irradiated from a light source to an ablation region through an irradiation window provided in the processing container to strike or evaporate constituent particles of the target and form a film on a substrate. Film formation method using ablation.   Using a target for generating an oxide superconductor, an infrared region from the second laser light source is applied to a base material having a laminated structure including a metal base body and an intermediate layer formed on the base body. The target surface is spot-heated by condensing and irradiating continuous wave laser light, and the target is obtained by condensing and irradiating pulsed laser light from the first laser light source to the ablation region inside the spot-heating region. 2. The film formation method using laser ablation according to claim 1, wherein the constituent particles are beaten or evaporated to form an oxide superconducting layer on the intermediate layer.   3. The film forming method using laser ablation according to claim 1, wherein the target surface is heated to 360 to 630 ° C. by continuous wave laser light from the second laser light source. A film forming apparatus for condensing and irradiating the surface of a target with a laser beam, striking or evaporating constituent particles of the target, and depositing the constituent particles of the target on a substrate,
A processing container for storing the target; a first laser light source that is provided outside the processing container and emits pulsed laser light for ablation that knocks or evaporates constituent particles from the target; and the processing container A region where the first laser light source is focused and irradiated with laser light on the surface of the target, and a second laser light source that emits continuous wave laser light that spot-heats the periphery of the region,
An irradiation window for transmitting pulsed laser light from the first laser light source and an irradiation window for transmitting continuous wave laser light from the second laser light source are provided in the processing container. Deposition device.   The film forming apparatus according to claim 4, wherein the second laser light source is a laser light source that emits a continuous wave laser beam in an infrared region.   The substrate support mechanism includes a supply reel on which a tape-shaped base material is mounted, a take-up reel that winds up the tape-shaped base material, and a plurality of turning reels that are installed between the supply reel and the take-up reel. The plurality of turning reels are arranged so that a tape-like base material supplied therebetween is arranged in a lane shape so as to face a target mounted on the target holder. The film forming apparatus according to claim 4 or 5.