JP2813691B2 - Laser deposition target - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target for producing a laser-deposited film for realizing a thin film in which fine foreign matter does not exist on the film surface in the laser vapor deposition method.

[0002]

Since manufacturing is reported BACKGROUND ART Several films by ruby laser in 1965, Nd: YAG laser, a thin film has been produced using a variety of laser CO ₂ laser. Since then, the power of laser oscillators has been improved and the wavelength has been shortened, the materials that can be thinned have been widened, and the quality of the thin films has also been improved. In particular, a laser vapor deposition method capable of vapor deposition under a high oxygen pressure attracts attention as a method for producing an LnBa ₂ Cu ₃ O _x oxide superconductor (Ln: Y and lanthanide element) thin film having Tc90K discovered in 1987. In addition, it has been evaluated that the method is an optimum means for producing an oxide thin film because it is easy to realize formation of a high Tc film. In recent years, it has also been used for producing a ferroelectric thin film because of its simplicity.

The laser vapor deposition method will be described with reference to FIG. In the figure, 1 is a laser beam, 2 is a laser beam irradiation part, 3 is a sintered body target, 4 is a gas introduction pipe, 5
Is a substrate, 6 is oxygen in the atmosphere, 7 is plasma-like atoms and lower oxides generated by laser irradiation, 8 is scattered matter generated from a target causing grains, and 9 is generated from a target causing grains. Melt, etc., 10 is a lens, 1
1 is a deposition chamber, 12 is a view port, and 13 is a substrate heater. For example, the excimer laser beam 1 is condensed by the lens 10 and is
And irradiates the sintered target 3. A part of the irradiated sintered body target 3 is excited by the excimer laser beam 1, turned into plasma in oxygen gas, and deposited on the substrate 5 heated on the opposite substrate heater 13. This is a method of obtaining a thin film. The laser vapor deposition method has the advantages that vapor deposition can be performed at a high oxygen pressure and that the composition of the thin film does not deviate from the target composition.

[0004]

However, in the laser deposition method, the target 3 is irradiated with the laser beam 1.
However, there is a disadvantage that particles having a diameter of about 1000 to 1 μm generated from the particles adhere to the thin film. It goes without saying that thin film crystals are extremely important in recent electronic devices and optical devices. In particular, it is well known that not only a thin film single layer structure but also a multilayer structure using different materials is essential for device application. However, when grains are present on the thin film, when the thin films are stacked in multiple layers on top of the thin film, if the grains have conductivity, it causes a short circuit between the layers. In addition, in the case of insulating properties, there is a very important problem that the electrical wiring is broken by grains.

[0005] When the target is irradiated with high-energy laser light, some of the microcrystals of the target are scattered and some of the microcrystals are melted, and the scattered melt is deposited on the substrate. Formed on reaching. This will be described with reference to FIG. In the figure, 1 is a laser beam, 2 is a laser beam irradiating section, 3 is a sintered target, 7 is a plasma-like atom, ion, lower oxide, etc. generated by laser irradiation, 8 is a target which causes grains. Scattered matter generated, 9 is a melt generated from a target that causes grains, 14 is a crystal irradiated with laser light, 15 is decomposed into atoms, ions, etc. on the surface of the crystal irradiated with laser light. A portion 16 is a portion adjacent to the crystal irradiated with the laser light, and a portion 17 absorbs the irradiated laser light as heat.

FIG. 4 shows a laser beam 1
Is a schematic drawing of the irradiated portion 2 to which the light is irradiated.
The sintered body target 3 depends on the sintering conditions,
Very generally, it is an aggregate in which microcrystals of about 1 μm in diameter are coarsely packed. When this microcrystal is irradiated with the laser beam 1, the irradiated surface 15 of the microcrystal 14 receives the photon energy and is explosively decomposed into atoms, ions 7 and the like. At this time, the part 1 next to the irradiated microcrystal 14
6 is a flying object that is blown away by an explosion and causes particles 8
Becomes On the other hand, photon energy is absorbed in the irradiated microcrystals 14. As described above, since the photon energy is high near the surface, it is decomposed into atoms, ions 7 and the like, but inside the microcrystal 14, the photon energy is converted into heat energy and heats the remaining portion 17 of the microcrystal 14. At this time, in the target 3 made of a sintered body, the microcrystal 14 has a small area in contact with its neighbor, so that heat does not escape. This is a reasonable idea based on the general tendency that the thermal conductivity of the sintered body is several orders of magnitude worse than that of the crystalline body. As a result, heat is trapped in the microcrystals 14, and the microcrystals are melted and released from the target, and become the melt 9 causing grains. The present invention has been proposed in order to improve the above-mentioned drawbacks, and an object of the present invention is to provide a target for producing a laser-deposited film capable of easily obtaining a thin film in which fine foreign matter does not exist on the thin-film surface in the laser deposition method. Is to do. The most important feature of the present invention is to use a crystal as a target in the laser deposition method. The conventional manufacturing technique is different in that grains in which the fine crystals of the sintered body target are scattered and grains in which the fine crystals are melted are generated and reach the substrate.

[0007]

Means for Solving the Problems As described above, the present inventors have analyzed that the cause of grain generation in the laser vapor deposition method lies in the target itself, that is, that it is due to the sintered body, He came up with the idea that the target to be used should not be an aggregate of microcrystals. Therefore, the target for producing a laser vapor deposition film according to the present invention uses a crystal of the material to be thinned as the target. The size of the focal point of the excimer laser light is about 2 mm × 1 mm. Crystals composed of single crystal grains of this size are not readily available. Therefore, a necessary condition for achieving the same effect as that of a target made of a single crystal is that the distance of the space between crystal grains (the distance between voids and the like) is larger than the size of the focal point of the laser beam. . In other words, even if it is not a single crystal but a polycrystal, it is good if there is no space in the focus region of the laser beam. This will be described with reference to FIG. In FIG. 5A, 1 is a laser beam, 19 is a target of a sintered body, and there is a space between particles constituting the sintered body. Because of this void, even if this is used as a target, a favorable thin film cannot be obtained. In (b), the target 18 is a single crystal, and is a preferable target. In (c), reference numeral 20 denotes a polycrystal, each of which is composed of a single crystal and has the same density as a single crystal, and is a preferable target. Such a target is produced by a melt powder melt growth method (a method of growing a powder by melting it at a high temperature) or the like. Conventionally, a target prepared by a coprecipitation method, which is said to have a relatively high density, has a single crystal bulk of 9%.
The density was about 5%. However, according to the present invention,
Among the above crystals, the single crystal has less fluctuation of the structure.
It is characterized by using the crystal body
I have. That is, in order to achieve the above object, the present invention is a target used in a laser vapor deposition thin film manufacturing method of irradiating a converged laser beam to a target to form a plasma, and depositing a thin film of the target material on a substrate. A gist of the present invention is a target for producing a laser-deposited film, wherein the target is made of a single crystal .

[0008]

In the present invention, since the target is made of a crystalline body, there are no microcrystals which are easily separated from the target and the surface. Therefore, when the laser beam is applied to the target, part of the microcrystal does not scatter around the irradiated portion. Also, in the irradiated portion, the photon energy that could not decompose the target material into atoms, ions 7 and the like becomes heat, but the heat is diffused and propagated inside the target, so that the heat is partially collected and melted. It creates an object, melts the inside of the irradiated part and does not scatter it.

[0009]

Next, an embodiment of the present invention will be described. It should be noted that the embodiments are merely examples, and it is needless to say that various changes or improvements can be made without departing from the spirit of the present invention.

Embodiment 1 In this embodiment, a so-called oxide high-temperature superconductor YBa ₂ Cu is used.
In the thin film formation of the ₃ O _x, with a crystal of the _YBa 2 _Cu 3 _{O x} to the target. FIG. 1 shows a first embodiment of the present invention.
In the figure, 1 is a laser beam, 2 is a laser beam irradiation section, 7 is a plasma atom, lower oxide, etc. generated by the laser beam irradiation, and 14 is a laser beam irradiation A crystal, 15 is a surface of the crystal, 16 is a portion adjacent to the crystal irradiated with laser light, 17 is a portion absorbing laser light as heat, and 18 is a YBa ₂ Cu ₃ O _x crystal target having an oxygen-deficient perovskite structure. It is.

Next, in order to operate this apparatus, for example, an ArF excimer laser beam is condensed by using a lens as the laser beam 1, and a crystal target 18 is disposed at a focal point thereof. In this embodiment, YBa ₂ Cu ₃ O
_x crystals were used. When the crystal target 18 is irradiated with the laser beam 1, the surface 15 of the irradiated portion receives photon energy and is explosively decomposed into atoms, ions 7, and the like. At this time, since the portion 16 next to the irradiated microcrystal 14 is a part of a large crystal, it is strongly bonded to another portion and is not blown off by an explosion. Further, as described above, the photon energy is high near the surface and is decomposed into atoms, ions 7 and the like.
Inside is converted photon energy to heat energy,
Inside 1 of irradiation part surface 15 decomposed into atoms and ions
Heat 7 Since the target in the present embodiment is made of a single crystal, the thermal conductivity is much better than that of a conventional target made of a sintered body. Does not occur. The resulting thin film is a thin film without particles. In fact, when a sintered target was used, the number of grains having a diameter of 1 μm was about 10 ⁷ / cm ² , but in the case of the present example using a single crystal target, several grains / cm ² or less. And was hardly detected. In this embodiment, ArF excimer laser light is used as laser light for laser deposition, and YF is used as a target.
Although the description has been made using the Ba ₂ Cu ₃ O _x crystal, excimer light such as KrF or XeCl or YA is used as the laser light.
It is also effective in G laser or the like, as the target e.g. BiSrCaCuO _x system, is the same with a crystal of TlBaCaCuO _x system or the like.

Embodiment 2 In this embodiment, not a thin film having an oxygen-deficient perovskite structure but a distorted perovskite structure (GdFe crystallographically)
PrGaO ₃ having an (O ₃ structure) will be described. FIG. 2 is a view for explaining a second embodiment of the present invention. In the figure, 1 is a laser beam, 2 is a laser beam irradiation section, 4 is a gas introduction pipe, 5 is a substrate, 6 is oxygen in the atmosphere, 7 Is a plasma-like atom generated by laser irradiation, a lower oxide, etc., 10 is a lens, 11 is a deposition chamber, 12 is a view port, 1
Reference numeral 3 denotes a substrate heater, and reference numeral 18 denotes a PrGaO ₃ single crystal target having a distorted perovskite structure. The difference from the first embodiment lies in the crystal structure of the target. Sintered body P
When the rGaO ₃ target was used, the number of grains was about 10 ⁶ / cm ^{2 on the} surface of the thin film. However, when the PrGaO ₃ single crystal target was used, it was confirmed that there was no undetectable grain. _YBa 2 _Cu 3 _{O x} and with oxygen-deficient Perousukaito group structure in the embodiment of the present invention, (the crystallographically GdFeO ₃ structure) Perousukaito structure distorted Having described the embodiment in detail PrGaO ₃ having,
Even with a complex oxide having a cubic perovskite structure or a complex oxide having a quasi-ilmenite structure, which is the basis of these materials, it is not possible to obtain a good thin film without fine particles by using a crystalline target. it is obvious. The point is that the target is a crystal. In other words, the main factor for realizing a thin film without particles as minute foreign matter is whether to use a crystal for the target, not the crystal structure and the material. Although the vapor deposition in a gas atmosphere has been described here, the same effect can be obtained by using the crystal according to the present invention as a target in the vapor deposition of a semiconductor regardless of whether or not it is in a gas atmosphere.

[0013]

As described above, in the present invention, since the single crystal is used as the target, the irradiated portion and the portion around the irradiated portion are strongly connected,
There is no scattering around the irradiated part. Since the diffusion of heat from the portion that absorbs the laser light as heat is fast, there is an effect that it does not melt and scatter, and as a result, there is an advantage that a film without particles can be realized.

[Brief description of the drawings]

FIG. 1 shows a state in which a target according to an embodiment of the present invention is irradiated with laser light.

FIG. 2 shows an apparatus used in the present invention.

FIG. 3 shows a conventionally used device.

FIG. 4 shows a state where a target is irradiated with laser light in a conventional example.

FIGS. 5A to 5C are explanatory diagrams of the operation, and show respective examples.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser light 2 Laser irradiation part 3 Sintered body target 4 Gas introduction pipe 5 Substrate 6 Atmospheric oxygen 7 Plasma-like atoms, ions, lower oxides, etc. 8 Scattered matter generated from a target causing 9 grains Melt generated from the target causing the cause 10 Lens 11 Vapor deposition chamber 12 Viewport (laser light introduction window) 13 Substrate Peter 14 Irradiated microcrystal 15 Surface of irradiated part 16 Peripheral part of irradiated part 17 Irradiated Part where the laser light inside the broken part is absorbed as heat 18 crystal target (single crystal target) 19 sintered body 20 polycrystal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-214098 (JP, A) JP-A-4-119968 (JP, A) V. Reddl et al. , "Densification and microstructure studies on Y-Ba-Cu-O superconducting oxide", Supercond. Sci. Technol. , Vol. 1, No. 3, 1988, p. 148-152 (58) Field surveyed (Int.Cl. ⁶ , DB name) C30B 23/08 H01L 21/203 H01L 21/363 C30B 28/00-35/00

Claims (1)

(57) [Claims] 1. A target used in a laser vapor deposition thin film manufacturing method of irradiating a converged laser beam onto a target to generate plasma and depositing a thin film of the target material on a substrate, wherein the target is a single crystal.
A target for producing a laser-deposited film, comprising a body .