Laser deposition method and apparatus, and product thereof.

BACKGROUND OF THE INVENTION

1. Field of the invention:

This invention relates to laser deposition tech­nology in which laser light is irradiated to a target so that an emitting material emitted from the target is deposited on a substrate.

2. Description of the Related Art:

Heretofore, a variety of films and particularly thin films have been used as anti-reflection films of optical parts, such as camera lens, and also in sur­face coatings of ornaments. As great advances have recently been made in electronics, the irradiation of thin films to the wiring of semiconductor devices, ICs, LSIs, etc. as well as to magnetic recording materials has been on the rise.

Further, upon progress of study on thin films, it has turned out that various peculiar effects such as tunneling effect could be achieved with thin films and also that shaping the material into a thin film could cause the structure of the material to change, depending on which various new functions and features could be provided. Accordingly the significance of films is increasing throughout various fields.

Known film manufacturing technologies are ex­emplified by a vacuum deposition method in which par­ticles of a film material are caused to evaporate in high vacuum and the evaporated particles are deposited over a substrate, and a sputtering method in which ions are irradiated to a target (an object to which ion is to be irradiated) to cause atoms and molecules of the target surface to evaporate and then to be deposited over a substrate; and any suitable method may be adopted depending on the kind of a film to be produced.

By utilizing plasma and ions in the conventional film production, the following effects can be ob­tained: <ul id="ul0001" list-style="none"><li>(1) It is possible to clean the substrate sur­face on which a film is to be formed, caus­ing an improved degree of close adhesive­ness.</li><li>(2) It is possible to control the property, such as crystallinity, of a film to be formed.</li></ul>

Following are methods for positively utilizing the above effects of plasma and ions: <ul id="ul0002" list-style="none"><li>(a) Ion plating method, in which evaporated par­ticles are ionized in plasma, are ac­celerated by electromagnetic field and are then deposited on the substrate.</li><li>(b) Cluster ion beam method, in which a cluster is formed of about 1,000 atoms or molecules by adiabatic expansion, is ionized and is then accelerated and deposited over the sub­strate.</li><li>(c) Ion beam method, in which ions formed in an ionization unit is irradiated to the target.</li><li>(d) Ion beam enhanced deposition method, in which particles are evaporated by ion beam, are ionized and is then deposited on the substrate.</li></ul>

However, the above methods have several problems on preparations of thin films.

In ion plating method (a) and ion beam method (c), particles are evaporated and ionized by gaseous plasma and discharge of inert gas such as argon. Therefore, these methods cannot be used in high vacuum so that impurities contained in the film can be mini­mized only inadequately. This is partly because inert gas contains impurities, which can be mixed in the film and partly because inert gas itself can be mixed in the film as impurities.

Further, in ion plating method (a), cluster ion beam method (b) and ion beam enhanced deposition meth­od (d), an evaporation source and ionization unit for evaporating a material are provided independently of each other, thus making the entire apparatus bulky and complex.

In addition, in any of the methods (a) through (d), since most of the ions of film material to be evaporated is has almost singly charged, it is im­possible to produce a film of a peculiar character­istic in which multiply charged ions are selectively utilized. Also, there have been many restrictions to the material to be evaporated so that a film having a desired quality could not be formed.

Furthermore, in the case of a multilayer film composed of a plurality of superimposed films or a mixed film formed of mixture of a plurality of materials, evaporation sources are needed one for each material to be evaporated, which makes the entire ap­paratus very bulky.

Another known method is a laser deposition meth­od in which laser light is focused and irradiated to a target to evaporate an emitting material from the target so that evaporated particles is deposited on the substrate. This prior art is exemplified by Japa­nese Patent Laid-Open Publications Nos. 116373/1984 and 43929/1989. In these prior laser deposition meth­ods, since there is provided no means for selecting the emitting material emitted only in a predetermined direction, a film having an undesired characteristic would also be formed.

Amorphous materials in a state of thermodynami­cally unequilibrium are not entirely crystalline and have only short-range order in its structure, having characteristics good in corrosion resistance, abrasion resistance, etc.

Further, amorphous iron or iron alloy has a good magnetic characteristic, such as a high magnetic permeability and a low coercive force, so that materials suitable for use in various kinds of applied art such as transformers and magnetic heads. Con­sequently, researches and studies have in recent years been made on amorphous materials.

Heretofore, for forming an amorphous film, a vacuum deposition method, a sputtering method and a liquid quenching method are known.

In the vacuum deposition method, a sample is heated and evaporated in a vacuum chamber by, for ex­ample, a heater, and is deposited and cooled on a sub­strate to form an amorphous film.

In the sputtering method, a plasma of argon or nitrogen gas is formed in a vacuum chamber to sput (strike out) sample particles with the plasma parti­cles so that the sample particles are deposited and cooled on a substrate.

In the liquid quenching method, a sample is melted by heating at a temperature higher than its melting point, and the melted sample is then cooled quickly.

However, according to the liquid quenching meth­od, there is a limit in the cooling speed (supremum speed of about 10⁷ K/sec), and hence only limited kinds of metals or alloys can be made amorphous.

According to the vacuum deposition method, since the energy of the sample particles during deposition is relatively low, the cooling speed of the sample particles deposited on the substrate is small so that only limited kinds of metals or alloys can be made amorphous.

According to the sputtering method, the cooling speed of the sample particles on the substrate is higher than that in the vacuum deposition method, but residual gas in the atmosphere will be mixed into a prospective film during sputtering, thus deteriorating the film quality. Therefore it is difficult to form a good quality amorphous film. Forming a single-metal or alloy amorphous film requires a high cooling speed of, for example, higher than 10¹⁰K/sec for Fe (iron) [Publication by H. A. Davies: proc. of 3rd intern. conf. on Rapidly Quenched Metals (1978) 1]. For this reason, according to the conventional methods, such good quality amorphous film could not be achieved.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a laser deposition method and apparatus by which the structure of a film can be controlled, so as to be a desired one, by selecting the emitting material emitted only in a predetermined direction and also by adjusting the velocity and quantity of the emitting material, which is selectively caused to pass at need, depending on physical and chemical states and distributions thereof.

Another object of this invention to provide a single-metal or alloy amorphous film and a method of production thereof.

According to a first aspect of this invention, there is provided a laser deposition apparatus com­prising: a reducing chamber formed airtightly for keeping its interior in a pressure-reduced state; a target holder disposed in the interior of the reducing chamber for holding a target; a laser for outputting laser light; a focusing means for focusing the laser light from the laser to irradiate the focused laser light to the target, so as to cause an emitting material to emit from the target and so as to generate laser induced plasma; a substrate holder for holding a substrate to which the emitting material emitted from the target is to be deposited; and a direction selec­ ting means disposed in a traveling path of the emit­ting material passing through the target holder and the substrate holder, the direction selecting means being capable of selecting, from the emitting material emitted from the target, a part of the emitting material that is emitted toward the range of a predetermined angle.

According to a second aspect of the invention, there is provided a laser deposition method compris­ing: placing a target and a substrate in a reducing chamber which interior is kept in a pressure-reduced state; focusing laser light and then applying it over the target to cause an emitting material to emit from the target and to generate laser induced plasma; se­lecting, from the emitting material emitted from the target, a part of the emitting material that is emitted only in a predetermined direction; and attach­ing the selected emitting material to the substrate.

For deposition, firstly the target capable of emitting a deposition material is attached to a target holder while the substrate on which surface a film is to be formed is attached to a substrate holder. Then gas in the airtight chamber is evacuated by a vacuum pump, for example, to keep the interior of the airtight chamber in a pressure-reduced state.

Subsequently, laser light is irradiated to the target from a laser. Preferably, the laser should radiate pulsed laser light, such as excimer laser, or laser light chopped from the continuous laser light. This laser light is focused on the surface of the target by an optical system, such as an optical lens, thus irradiating the laser light of a predetermined high energy.

By this irradiation of laser, ions or electrons and neutral atoms are emitted from the target, and then laser induced plasma is produced. The density of laser induced plasma, for example, can be easily ad­justed by varying, for example, the focusing degree of the optical system.

The emitting material emitted from the target are scattered in all directions, while a part of the emitting material flies toward the substrate and is deposited to the surface of the substrate.

The apparatus of this invention includes a se­lectively transmitting means for controlling the emit­ting material, which is to be deposited on the sub­strate, depending on the physical state of velocity, mass, etc. of the emitting material and also on the chemical state of kind (singly charged and multiply charged ions, electrons, neutral atoms, etc.) of the emitting material. The selectively transmitting means may be a filter (an aperture), in the form of a shielding plate having an opening. They may also be a filter in the form of a shielding plate having an opening for repeatedly opening and closing the opening at a predetermined time interval to select a part of the emitting material passing through the opening only at a predetermined time.

With this selectively transmitting means, only a part of the emitting material having passed the open­ing of the shielding plate is allowed to reach the surface of the substrate.

On the other hand, the emitting material emitted from the target varies in physical state such as velocity, mass, etc. and in direction of emission, depending on the chemical state such as the kind of the emitting material, thus causing a spatial com­ponent distribution of the emitting material based on this variation. The characteristic of the deposited film can be controlled by spatial selection by, for example, a shield plate having an opening. For exam­ple, by this spatial selection, it is possible to con­trol the proportion of crystal phase, such as α phase and β phase, of a tungsten deposition film.

Further, by locating, in a path from the target to the substrate, a velocity filter by rotating a disk having an opening of an predetermined angle, it is possible to select only the emitting material which reaches the velocity filter in a predetermined time. Namely, as laser light is irradiated to the target, the emitting material reaches the velocity filter in the order of velocity. Therefore, by opening and closing the velocity filter in synchronism with ir­radiation of laser light and by opening the velocity filter only for a predetermined time after irradiation of laser light, it is possible to select only the emitting material which has a velocity corresponding to that time. For example, using molybdenum for the target, fine particles can be removed or only ions can be selected.

If a charged particle controlling means for con­trolling spatial and timewise distribution of charged particles in the emitting material by adjusting the emitting state such as by applying a predetermined voltage between the target and the substrate, it is possible to control, for example, the crystallinity of a deposited film by adjusting the velocity, order and quantity when the emitting material, which is emitted from the target, reaches the substrate, according to the chemical state of the emitting material. For ex­ample, if voltage is irradiated in such a manner that the potential of the target is a positive or negative value with respect to the substrate, an electromag­netic field is formed in the traveling path of the emitting material so that ions having charge are ac­celerated or decelerated by this field. This varies the velocity, order and quantity according to the chemical state of the emitting material, which is deposited to the substrate, so that the crystal struc­ture of the film to be formed on the substrate surface will be changes. By varying the voltage irradiated between the target and the substrate, it is possible to control the property, such as crystal structure, of the deposited film.

For example, if the potential of the target is less than -1 kV or more than 1 kV with tungsten used for the target, it is possible to form a film of small crystal particles on the substrate. If it is about 300 V, it is possible to a tungsten film which is very good in crystallinity.

As described above, according to the laser deposition method and apparatus of this invention, the proportion of crystal phases and the crystal structure of the deposited film can be controlled. Therefore, a film having a desired proportion of crystal phases and a desired crystal structure can be obtained with simple construction, and a film having a new structure selectively using multifly charged ions can be ob­tained. Accordingly, in various fields using films, it is possible to achieve new functions and features and to improve various functions.

According to a third aspect of the invention, an amorphous metal film formed on a surface of a sub­strate by deposition, wherein the metal film has a noncrystalline structure such that the result of X-ray diffraction shows a broad pattern, the metal film com­prising a metal having a critical cool speed of higher than 10⁷ K/sec. The amorphous metal film comprises a single metal or an alloy and includes a noncrystalline state composed of a noncrystalline film and a partial crystal structure.

According to a fourth aspect of the invention, there is provided a method of producing an amorphous metal film, comprising: placing an alloy or single-­metal target and a substrate in a vacuum chamber whose interior is kept in a high vacuum state; irradiating laser light to a surface of the target to evaporate a high-speed evaporation material from the target; ap­plying an electric field between the target and the substrate, depending on a critical cooling speed needed for making the evaporation material on the sub­strate amorphous and depending on impact energy of the high-speed evaporation material against the substrate; and cooling the evaporation material on the substrate at the critical cooping speed and accelerating a charged component in the evaporation material to in­ crease the impact energy against the substrate so that agitation occurs in atom arrangement of the film to form a noncrystalline metal film on the substrate.

According to a fifth aspect of the invention, there is provided an apparatus for producing an amor­phous metal film on a substrate, comprising: a vacuum chamber whose interior is kept in a high vacuum state; a target holder disposed in the vacuum chamber for holding an alloy or a single-metal target; a substrate holder disposed in the vacuum chamber in confronting relation to the target holder for holding the sub­strate; a laser irradiating means for irradiating laser light to a surface of the target, which is held by the target holder, to generate a high-speed evaporation material; and a voltage applying means for applying an electric field between the target and the substrate for maintaining a critical cooling speed needed to make the evaporation material on the sub­strate amorphous and also maintaining impact energy of the high-speed evaporation material against the sub­strate.

Since the laser is capable of concentrating en­ergy on the target at high density, the emitting velocity of the evaporation material is greater than in the conventional art and the temperature (energy) of the evaporation material is higher than in the con­ ventional art. Therefore it is possible to increase the cooling speed (the temperature of the evaporation material is room temperature) of the evaporation material on the substrate. Further, the evaporation material can be formed in high vacuum, it is possible to prevent impurities from mixing in the film.

If the evaporation material contains positively or negatively charged particles, the application of electric field can increase the energy of the charged component of the evaporation material and increase the cooling speed of the charged component, and can break the chemical bond in the deposited film and put the high-energy evaporation material thereinto to agitate the atom arrangement of the film, thus easily making the film structure amorphous. Accordingly, an amor­phous film of a single metal or alloy requiring a high cooling speed, for example, an amorphous magnetic film such as of Fe (iron) having a good magnetic character­istic can be produced.

As discussed above, by utilizing laser light, it is possible to obtain an amorphous single-metal or al­loy film.

The amorphous metal or alloy film, for example, an amorphous iron film is excellently resistant to corrosion and abrasion and has a good magnetic charac­teristic, such as high magnetic flux density, high magnetic permeability and low coercive force, so that materials suitable for use in various kinds of applied art such as transformers and magnetic heads.

The above and other advantages, features and ad­ditional objects of this invention will be manifest to those versed in the art upon making reference to the following detailed description and the accompanying drawings in which several preferred embodiments in­corporating the principles of this invention are shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

<ul id="ul0003" list-style="none"><li>FIG. 1 is a schematic cross-sectional view show­ing main parts of a laser deposition apparatus accord­ing to a first embodiment of this invention;</li><li>FIG. 2 is a characteristic view of X-ray dif­fraction of a tungsten film according to the first em­bodiment;</li><li>FIG. 3 is a diagram schematically showing one example of a target according to the first embodiment;</li><li>FIG. 4 is a characteristic view of X-ray dif­fraction of an Fe-Cu film according to the first em­bodiment;</li><li>FIG. 5 is a view similar to FIG. 1, showing main parts of a modified laser deposition apparatus accord­ing to a second embodiment;</li><li>FIG. 6 is a schematic perspective view showing the construction of the second embodiment;</li><li>FIG. 7 is a schematic perspective view showing a modified construction of the second embodiment;</li><li>FIG. 8 is a graph showing the velocity distribu­tion of materials emitted from a target;</li><li>FIG. 9 is a view similar to FIGS. 1 and 5, show­ing main parts of another modified laser deposition apparatus according to a third embodiment;</li><li>FIG. 10 is a characteristic view of X-ray dif­fraction of a tungsten film according to the third em­bodiment;</li><li>FIG. 11 is a view similar to FIGS. 1, 5 and 9, showing main parts of still another modified laser deposition apparatus according to a fourth embodiment;</li><li>FIGS. 12 and 13 show an amorphous metal film producing apparatus embodying this invention;</li><li>FIG. 14, (A), (B) and (C), is pattern diagrams showing the result of X-ray diffraction of a sample amorphous pure iron film;</li><li>FIG. 15 is a characteristic diagram showing saturated magnetic densities of sample amorphous pure iron film and iron alloy film; and</li><li>FIG. 16 is a pattern diagram showing the result of X-ray diffraction of a sample amorphous tungsten film.</li></ul>

DETAILED DESCRIPTION

Various embodiments of this invention will now be described with reference to the accompanying draw­ings.

First Embodiment

FIGS. 1 through 4 show a laser deposition appa­ratus according to a first embodiment of this inven­tion. As shown in FIG. 1, an airtight chamber 10 is a pressure-resistant chamber which is tightly closed to shield its interior from the exterior space. To the airtight chamber 10, a vacuum pump 12 is connected via a pressure regulator 14; by operating the vacuum pump 12, it is possible to cause the interior of the airtight chamber 10 to assume a pressure-reduced state. Usually, the internal pressure of the airtight chamber 10 is detected beforehand by means of a pres­sure detector (not shown), and the pressure regulator 14 can be controlled to keep the interior of the airtight chamber 10 at a predetermined pressure. Thus, the interior of the airtight chamber 10 can be made in a predetermined pressure-reduced state by the vacuum pump 12 and the pressure regulator 14.

Further, to the airtight chamber 10 a gas source 20 is connected via a valve 16 and a gas flow regulator 18 so that a desired gas from the gas source 20 can be introduced a predetermined amount at a time into the airtight chamber 10. Then the interior of the airtight chamber 10 can be kept in a predetermined gas atmospheric state.

A laser 30 radiates predetermined laser light 32, using pulsed excimer laser, for example. The laser light 32 passes a focusing lens 34 (optical sys­tem) and is then introduced into the airtight chamber 10 via a transmission window 36 formed in the airtight chamber 10.

Inside the airtight chamber 10, a rotary table 40 is mounted to support thereon a target 42. Specif­ically, to the rotary table 40 a secondary motor 44 is fixed. A target holder 46, to which the target 42 is secured, is fixed to a main shaft of the secondary motor 44.

Therefore, when applying laser light 32 to the target 42 by the focusing lens 34, it is possible to control the density of applying power of laser light, which is to be irradiated to the target 42, by adjust­ing the distance between the focusing lens 34 and the target 42. It is thereby possible to control the quantity and composition, e.g. ion quantity of the emitting material containing multiply charged ions of the emitting material and proportion of multiply charged ions, of the emitting material emitted from the target 42. In this invention, laser light is ir­radiated to the target 42 to generate plasma, and the density of this plasma also can be controlled by ad­justing the density of irradiated power of laser light.

In order to prevent the concentrated damage on the target 42 by the irradiation of laser to a fixed point, the secondary motor 44 is driven to rotate the target holder 46. Namely, by rotating the target holder 46 to rotate the target 42, the laser light focused by the focusing lens 34 is irradiated to indi­vidual portions of the target 42. Thus the target can be prevented from the concentrated damage on the target.

Further, by rotating the rotary table 40 about its axis of rotation, it is possible to vary the angle of the laser light from the focusing lens 34 with respect to the target 42. Thus it is possible to con­trol the direction of the emitting material emitted from the target 42.

A substrate holder 50 is disposed inside the airtight chamber 10 in such a position as to confront the target 42. A substrate 52 over which a film is to be formed by deposition is attached to the substrate holder 50.

In the first embodiment, a shielding plate 60 is provided on the front side of the substrate 52 as a selectively transmitting means serving as a deposition control means. This shielding plate 60 has an opening 62 so that the emitting material emitted from the target 42 is restricted to that passing through the opening 62; that is, the traveling path of the emit­ting material is restricted spatially to select the emitting material emitted in a predetermined direc­tion. Therefore, the material to be deposited on the surface of the substrate 52 is limited only that emitted from the target 42 in the direction of the opening 62. The components of the emitting material emitted from the target 42 have a predetermined dis­tribution, and therefore a desired components of the emitting material can be selected according to the position of the opening 62 of the shielding plate 60 and can be deposited over the substrate 52.

Two temperature control units 70, 72 are respec­tively attached to the target holder 46 and the sub­strate holder 50 for controlling the respective temperatures of the target 42 and the substrate 52.

In the laser deposition apparatus of this em­bodiment, when laser light 32 is focused and ir­radiated to the target 42, laser induced plasma is produced and the emitting material is emitted from the target 42. This emitting material is composed of neutral particles, cluster, liquid particles, fine grains, ions including multiply charged ions of them, electrons, etc. The emitting material is emitted in a predetermined direction, depending on its components. Therefore, the material emitted from the target 42 has a particular spatial distribution depending on its components; it is possible to select a desired com­ponent according to the position of the opening 62 or the angle of the rotary table 40.

Example 1

The experiment was actually conducted under the following conditions, using the apparatus of the first embodiment.

In this example, the target 42 was tungsten (W); the substrate 52, glass; the laser 30, KrF excimer laser (wavelength of 249 nm, pulse width of 16 nsec, pulse energy of 250 mJ); the repeating period of laser, 25 Hz; the total pulse number of irradiation of laser the target 42, 30,000 pulses; the area of ir­radiation of laser to the target 42, 6x10⁻³cm²; the rotational velocity of the motor 44, 20 rpm; the inci­dent angle of laser light 32 with respect to the target 42, 45°; the temperature of the target 42 and the substrate 52, room temperature; the pressure of the airtight chamber 10, less than 1x10⁻⁵Torr. Any particular gas from the gas source 20 was not intro­duced into the chamber 10.

Further, the distance between the target 42 and the substrate 52 was 30 mm, and the shielding plate 60 was disposed in close contact with the substrate 52.

Under the foregoing conditions, the laser light 32 was focused and irradiated onto the target 42 to generate there laser induced plasma. Then from the target 42, neutral particles, cluster, ions including polyvalent ions and electrons were emitted in all directions. The emitting material flied also toward the substrate 52 and is deposited on the substrate 42.

The shielding plate 60 having the opening 62 was disposed in front of the substrate 52. Since the spa­tial distribution (emitting direction) of ions in plasma varies depending on their number of charge, it was possible to control the ratio of ions of individu­al number of charge (e.g., +1 charge, +2 charge, +3 charge) reaching the substrate, by selecting a partic­ular direction by varying the position of the opening 62. Also, since the neutral atoms, cluster, fine grains, liquid drops are different in spatial distrib­ution, it was possible to control the ratio of charged particles and neutral particles reaching the sub­strate, by selection of a particular direction.

FIG. 2 shows the results of X-ray diffraction of the tungsten deposition film deposited on the sub­strate 52. In FIG. 2, the horizontal coordinate stands for diffraction angle 2Θ of X-ray, and the vertical coordinate stands for intensity of diffracted X-ray.

In the case where the largeness of the opening 62 was 30 mm (solid angle was 0.663 steradian), the tungsten deposited film has peak in incident angle corresponding to α phase and β phase, there existing mixed crystals of α phase and β phase. On the other hand, in the case where the largeness of the opening 62 was 5 mm (solid angle was 0.022 steradian), only the component, of the emitting material, which was high in ion (including multiply charged ion) quantity and plasma density in particular was deposited. Therefore, the tungsten deposited film was α single phase. Thus, by using the spatial distribution of components of the emitting material, it was possible to select only a particular component by varying the largeness of the opening 62. Therefore, it was un­derstood that the property of a film could be control­led. CoKα was used for the X-ray source.

The tungsten film thus obtained is suitable for use as wiring materials for IC and the like. At that time, the resistivity of the film should preferably be small. The resistivity of β phase is larger than that of α phase. However, the existence of this β phase is not desirable when the tungsten film is used as wiring materials. According to this invention, since only the emitting material emitted in a predetermined direction was selected, undesirable β phase could be removed and a film of only α phase could be formed.

Further, by utilizing its high melting point, the tungsten film can be used for coating the surface of heat-resistant part or member. In using a tungsten film, its crystallinity and crystal structure are fac­tors which dominate conductivity, heat resistance and corrosion resistance; the apparatus of this embodi­ment, which can control these factors, can perform very important role in utilizing a tungsten film.

Example 2

The experiment was conducted under the following conditions which are different from those in Example 1, using the apparatus of this embodiment.

As shown in FIG. 3, the target 42 was a split type composed of copper (Cu) and ion (Fe). The sub­strate 52 was glass; the laser 32, ArF excimer laser (wavelength of 193 nm, pulse width of 16 nsec, pulse energy of 200 mJ); the repeating period of laser, 25 Hz; the total pulse number of irradiation of laser to the target 42, 30,000 pulses; the area of irradiation of laser over the target 42, 6x10⁻³cm²; the incident angle of laser light 32 with respect to the target 42, 45°; the temperature of the target 42 and the sub­strate 52, room temperature; the pressure of the airtight chamber 10, less than 1x10⁻⁵Torr.

Under the foregoing conditions, the laser light 32 was irradiated onto the target 42 to generate there laser induced plasma. Then from the target 42, the emitting material and ions (including polyvalent ions) and electrons of iron and copper were alternately gen­erated. This is true partly because the target 42 was composed of iron and copper as shown in FIG. 3, and partly because iron and copper were alternately ir­radiated by laser light 32 as the motor 44 was rotated. By controlling the rotational velocity of the target 42, various kinds of multilayer films can be formed. Namely, the film thickness is determined depending on the irradiating time; if the rotating velocity of the target 42 is increased, the frequency of irradiation alternately over iron and copper is also increased. As a result, the number of layers of a film is increased while the thickness of each layer is reduced.

FIG. 4 shows the results of X-ray diffraction when a multilayer deposited film composed of iron and copper was formed on the substrate 52 in close contact with the shielding plate 60 as the target 42 was rotated at various velocitys. The largeness of the opening 62 was 5 mm, and the distance between the target 42 and the substrate 52 was 30 mm.

As is apparent from FIG. 4, when the multilayer film was composed of 1,840 layers, 460 layers, 92 layers or 20 layers of iron and copper as the rota­tional velocity was varied, it turned out that these multilayer films were different in construction. Spe­cifically, the crystal structure of a multilayer film was varied according to the rotational velocity of the target 42. Regarding iron, there stably existed in a multilayer film ε phase, which can be obtained only in a high-temperature and high-pressure state. There­fore, it will be understood that a film in a special construction. Every deposited film was has a common thickness of 1,380 A.

Further, if the target 42 is a split type of two or more kinds of materials, a mixed film can be formed according to the materials. By selecting a suitable proportion (area ratio) of separate materials of the target 42, it is possible to easily control the ratio of mixture of a multilayer film.

According to the first embodiment, it is pos­sible to select, from the emitting material emitted from the target 42, a suitable component of the material to form a desirable deposited film.

If a reactive gas is introduced from the gas source 20 into the airtight chamber 10 and deposition takes place in the reactive gas, it is possible to in­ crease the reactivity between ions, including polyvalent ions, of the emitting material and the gas so that reactive deposition can be performed in which the reactant is deposited on the substrate. For reac­tive gas, O₂, O₃, N₂, CH₄, C₂H₂ or other kind of gas may be selected depending on the kind of a film to be formed.

For manufacturing the target 42, various kinds of metals, alloy, ceramics, alumina, organic materials, liquid or gas may be absorbed in other solid surface. Accordingly, a desired film can be formed by selecting one from these various kinds of materials.

In this embodiment, since the apparatus has a temperature control unit 70, the target can be kept at a predetermined temperature. Therefore, it is pos­sible to prevent the target from cracking due to rapid temperature rise, so that scattering of gas or liquid from the solid material, in which the gas or liquid is absorbed, is prevented. Further, it is possible to control the crystal structure of a film by controlling the temperature of the substrate.

Generally, by selecting the method of super­imposing layers to form a multilayer, the materials to be superimposed, and the mixing ratio, it is possible to obtain a variety of properties which are possessed by non of materials existing in nature. If a multi­layer film having a new property is obtained, it is expected that the film might perform a definitely novel function.

In addition, a multilayer film having a special magnetic property can be used for optomagnetic record­ing material by making the film strong in vertical anisotropy.

Second Embodiment

FIGS. 5 through 7 show a laser deposition appa­ratus according to a second embodiment. Like reference numerals designate similar parts throughout FIGS. 1 through 7.

For a significant feature of the second embodi­ment, as a selectively transmitting means which is a deposition means, there is provided a velocity filter 80 for repeatedly shielding between the target 42 and the substrate 52 at a predetermined time interval to select on the emitting material passing there in a predetermined time. The velocity filter 80 is com­posed of a motor 82 and a rotary disk 84. The rotary disk 84 has an opening 86 of a predetermined angle of opening.

Specifically, in this example, as shown in FIGS. 5 and 6, the rotary disk 84 has a fan-shaped opening 86 which opens through an angle of Θ. The location of the velocity filter is such that the rotary disk 84 is disposed near the substrate side of the shielding plate 60.

Further, the target 42, the substrate 52 and other related parts are supported on the rotary table 40. In this embodiment, like the first embodiment, by rotation of the rotary table 40, it is possible to ad­just the angle of the laser light 32 with respect to the target 42 so that the target toward the substrate 52 can be spatially selected.

In this apparatus, a pulse laser generator 30 such as excimer laser focuses and irradiates pulse laser light to the target 42. Like the first embodi­ment, the emitting material is emitted from the target 42 to generate here laser induced plasma. Of the emitting material, that flew toward the substrate 52 passes a predetermined opening 62 of the shielding plate 60.

In this embodiment, the velocity filter 80 is located behind the shielding plate, the rotary disk 84 of the velocity filter 80 is rotated in synchronism with the pulse ocsillating period of the laser 30. Therefore, selection can be made on the timewise dis­tribution of the emitting material so that a desired component can be selected.

Specifically, by selectively varying, for exam­ ple, the width (angle of opening Θ) of the opening 86 of the rotary disk 84 of the velocity filter 80, the number of rotations of the rotary disk 84, the disk diameter, the repeating period of pulse laser, the distance between the target 42 and the velocity filter 80, it is possible to select, from the emitting material emitted from the target 42, only that emitted at a particular velocity. Therefore, selection of components utilizing timewise component distribution from the emitting material can be achieved.

Assuming that the velocity of the material (par­ticles) emitted from the target 42 is v (cm/sec) and the distance between the target 42 and the velocity filter 80 is d (cm), the time t_a taken for the material emitted from the target 42 to reach the velocity filter 80 is expressed by the following equa­tion: t_a = d/v

On the contrary, assuming that the rotational velocity of the rotary disk 82 in the velocity filter 80 is ω (rpm) and the angle Θ (degree) of the opening 86, the time t_p taken for the material emitted from the target 42 by irradiation of one pulse laser light 32 to reach the velocity filter 80 is expressed by the following equation: t_p = (60/ω)·Θ/360

Further, assuming that the repeating period T (pulses/sec) of the laser light 32 is identical with the rotational period ω (rpm) of the velocity filter 80, the time t_p is expressed by the following equa­tion: t_p = Θ/360T

Therefore, if the time t_a taken for the emitted material to reach the velocity filter 80 is equal to the time t_p taken for the emitted material to pass the velocity filter 80, it is possible to select only the material that is emitted at a velocity higher than the velocity v, for deposition on the substrate 52.

For this purpose, the distance d between the target 42 and the velocity filter 80 may be set by the following equation: d = (1/360)·v·Θ/T

The selection utilizing spatial component dis­tribution by the opening 62 of the shielding plate 60 is identical with that in the first embodiment.

In the illustrated example, laser to be ir­radiated is pulse-like, but alternatively may be con­tinuous. If the laser is ocsillated continuously, the construction of FIG. 6 should be modified as shown in FIG. 7. Namely, in the case of continuous laser light, a plurality of rotary disks 84 are used in the velocity filter 80, and the velocity filter 80 of FIG. 7 as that of FIG. 5 is supported on the rotary disks 80.

As shown in FIG. 7, the rotary disk 84 has a fan-shaped opening 86 which opens through an angle Θ. The location of the velocity filter 80 is such that the rotary disk 84 is disposed near the substrate side of the shielding plate 60.

In this example, the target 42, the substrate 52 and other related parts are supported on the rotary table 40. By adjusting the angle of laser light 32 with respect to the target 42, the target 42 toward the substrate can be spatially selected.

In this apparatus, the CW laser 30 such as large-output CO₂ laser is focused and irradiated to the target 42. Like the first embodiment, the material is emitted from the target 42, and laser in­duced plasma is generated there. Of the emitted material, that flew toward the substrate 52 passes a predetermined opening 62 of the shielding plate. The velocity filter 80 composed of a plurality of rotary disks is located behind the shielding plate 60.

By selecting, for example, the width (angle of opening Θ) of the opening 86 of the first rotary disk 84 of the velocity filter 80, the number of rotations of the first rotary disk 84, the disk diameter, the distance between the target 42 and the velocity filter 80, the bundle (or pack) of particles 100 is formed by the choppering the continuous emission, which contains various velocity components, from the target 42 using the first rotary disk 84. In the bundle of particles 100 there are the materials having various kinds of velocitys. The material flew at a higher velocity reaches the second rotary disk 106 earlier, while that flew at a lower velocity reaches the second rotary disk 106 afterwardly. As a result, the bundle of par­ticles 102 extends spatially and has a particle dis­tribution spatially corresponding to the velocity com­ponent. By selecting, for example, the width (angle of opening Θ′) of the opening 108 of the second rotary disk 106, the number of rotations of the rotary disk 106, its delay time, the disk diameter, the distance between the first rotary disk 84 and the second rotary disk 106, it is possible to obtain a bundle of parti­cles of which component is selected, like the bundle of particles 104. For efficiency, the number of rota­tions of the second rotary disk is the same as that of the first rotary disk or a multiple thereof.

By using a plurality of rotary disks, even in the case of continuous laser light, it is possible to select a particular velocity component of the emitting material like pulse-like generation.

As described above, the laser light of this em­ bodiment may be either pulse or continuous. For the feature of this embodiment, laser light is focused and irradiated to the target, and the traveling path of the emitted material is restricted spatially and timewise, and the material emitted in a predetermined direction in a predetermined period of time is selected.

Experiment

The experiment was conducted by using the appa­ratus of the second embodiment. The results of this experiment are as follows.

In this experiment, the target 42 was molybdenum (Mo); the substrate 52, glass; the laser 30, KrF ex­cimer laser (wavelength of 249 nm, pulse width of 16 nsec, pulse energy of 250 mJ); the internal pressure of the airtight chamber 10, less than 1x10⁻⁵Torr; the repeating period of laser pulse, 20 pulses/sec; the applying angle of laser light 32 with respect to the target 52, 45°; the total pulse number, 30,000; the area over which the laser light 32 is irradiated the target 42, 6x10⁻³cm², the rotational velocity of the target 42, 20 rpm; and the temperature of the target 42, room temperature.

Under the above condition, vacuum deposition took place. The velocity distribution of the parti­cles constituting the emitted material is shown in FIG. 7. By allowing the emitted material to pass the velocity filter 80 only after the lapse of a predetermined time from irradiation of laser pulses to the target, it is possible to select the emitted material which is to pass the velocity filter 80. In other words, if the velocity filter 80 is set to a very short time from irradiation of laser light 32 over the target 42, it is possible to select only mul­tiply charged ions. If the velocity filter 80 is set to open only a predetermined time thereafter, it is possible to select only singly charged ions.

Now, the experiment was conducted under the fol­lowing conditions: the diameter of the opening 62 of the shielding plate 60 was 20 mm; the diameter of the rotary disk 84 of the velocity filter 80, 30 mm; the angle Θ of the opening 86 of the rotary disk, 5°; the number of rotations, 1,200 rmp; the distance d between the target 42 and the velocity filter 80, 34.7 mm; the distance between the target 42 and the substrate 52, 40 mm; and the shielding plate 60 is disposed 2 mm ahead of the velocity filter.

By synchronizing the pulsed laser light 32 with rotation of the velocity filter 80, the emitted material is allowed to pass the velocity filter 80 only in a predetermined period of time (0.7 msec) from the start of irradiation of the laser light to the target 42. Thus, the velocity filter 80 allows only the material having a velocity of more than 5x10³ cm/sec, to pass in accordance with the time to pass.

As is apparent from FIG. 7, since fine grains are small in velocity, it is presumed that the fine grains in the deposited film can be reduced in number by the velocity filter 80. To this end, deposition tests were conducted in the absence of and in the presence of the velocity filter 80, and the density of fine grains was measured.

The density of fine grains in the presence of the velocity filter 80 was 65/mm², while the density of fine grains in the absence of the velocity filter 80 was 2.4x10³/mm².

From the results of this experiment, it is un­derstood that the velocity filter 80 can eliminate the fine grains efficiently. This number of fine grains was measured by using SEM (Scanning Electron Micro­scope) photographs taken in the experiment.

Third Embodiment

FIGS. 9 and 10 show a third embodiment. Like reference numerals designate similar parts throughout the first, second and third embodiments.

For the features of the third embodiment, the apparatus is provided with an irradiated-voltage con­trol means for controlling the velocity, kind and quantity of the emitting material according to its chemical state to keep the voltage irradiated between the target 42 and the substrate 52 at a predetermined level. The irradiated-voltage control means is com­posed of a switch 90, a positive variable voltage source 92 or a negative variable voltage source 94. With this irradiated-voltage control means, a voltage is irradiated to the target 42, and the substrate 52 is connected to the ground. Therefore, it is possible to give a predetermined positive or negative potential between the target 42 and the substrate 52. Further, since the output voltage value of each of the positive and negative voltage sources 92, 94 is variable, the target 42 can be set to a desired potential.

By giving a predetermined potential to the target 42 by the voltage sources 92, 94, it is pos­sible to control, of laser induced plasma generated by laser light 32, only the charged particles of the material emitted in a predetermined direction selected by the opening 62 of the shielding plate 60. Specifi­cally, if the potential of the target 42 is positive, ions emitted from the target 42 and passed through the shielding plate 60 are accelerated by the electromag­netic field created between the target 42 and the sub­strate 52. Reversely, if the potential of the target 42 is negative, the ions passed through the shielding plate 60 are decelerated. Further, creating such field varies the acceleration depending on the number of charge and mass of ions to vary the spatial and timewise distribution of charged particles in the emitted material. The velocity, order and quantity of ions when reaching the substrate 52 vary depending on whether or not they are ions and on the number of charge and mass of ions. By varying the potential of the target 42, it is possible to control the property, e.g. crystallinity, of the film deposited on the sub­strate 52.

At that time, the potential of the shielding plate 60 is optional, and the function of the elec­tromagnetic field lens as well as the selective trans­mission means may be added. Further, the number of openings or cylindrical tubes constituting the shield­ing plate 60 are not limited to the illustrated exam­ples and may be settable according to the situation. Also the shape of the opening should by no means be limited to a circle as illustrated. Thus, this third embodiment features that a predetermined voltage is irradiated between the target and the substrate and that the velocity, kind and quantity of the material are selected according to the chemical state of the material that is emitted in a predetermined direction.

Experiment

The experiment was conducted under the following conditions, using the apparatus of the third embodi­ment. In this experiment, the target 42 was tungsten (W); the substrate 52, glass; the laser 30, KrF ex­cimer laser (wavelength of 249 nm, pulse width of 16 nsec, pulse energy of 250 mJ); the degree of vacuum inside the airtight chamber 10, less than 1x10⁻⁵Torr; the repeating period of pulse laser, 25 pulses/sec; the angle of irradiation of the laser light over the target 42, 45°; the total pulse number, 30,000; the area over which laser light is irradiated to the target 42, 6x10⁻³cm²; the rotational velocity of the target 42, 20 rpm; the temperature of the target 42, room temperature; the temperature of the substrate 52, room temperature; and the distance between the target 42 and the substrate 52, 30 mm. Further, the opening 62 of the shielding plate 60 was ø5 mm; the distance between the substrate 52 and the shielding plate 60, 1 mm; and the potential of the shielding plate 60, the ground.

Under the above condition, by giving the poten­tial of -1 kV to 1 kV to the target 42, the velocity and quantity of the charged particles in the selected and transmitted material were controlled.

The results of X-ray diffraction of the tungsten deposited film obtained by this experiment are shown in FIG. 10. If no voltage is irradiated to the target 42, the tungsten film is high in crystallinity. But, when the potential of the target 42 was negative and its voltage was gradually increased, the crystallinity of the tungsten deposited film was gradually lowered. When the potential was -1 kV, it was non-crystalline. Reversely, when the potential of the target 42 was positive and was gradually increased, the crystal­linity came improving up to about 300 V. Beyond 300 V, the grain size of the crystal was reduced.

In this experiment, the temperature of the sub­strate 52 was room temperature. If the temperature of the substrate 52 was kept at 500°C, the film deposited on the substrate 52 became crystalline as the poten­tial of the target 42 was in the range of -3 kV to 3 kV.

As described above, by applying a voltage be­tween the target 42 and the substrate 52 and controll­ing laser induced plasma, it is possible to control the crystal structure of the deposited film formed on the substrate 52. Further, since the property of a tungsten film is very dependent on its crystal struc­ture, it is possible to obtain different kinds of films having various properties. For example, by reducing the crystal grains in size, it is possible to increase the degree of hardness of a film so that a film suited for abrasion-resistant and heat-resistant coating. In addition, improving the cystallinity means realizing a characteristic more suited for wiring materials.

Fourth Embodiment

FIG. 11 shows a fourth embodiment in which the velocity filter of the second embodiment and the irradiated-voltage control means of the third embodi­ment are used.

According to the fourth embodiment, it is pos­sible to select only the material which is emitted in a predetermined direction and at a predetermined velocity, and to control the velocity, order and quantity of the charged particles which reach the sub­strate. Therefore, the conditions for forming the film by deposition can be set in detail, and the con­struction of the film can be widely controlled.

Fifth Embodiment

FIGS. 12 and 13 show an amorphous metal film producing apparatus.

As shown in FIGS. 12 and 13, a vacuum chamber 110 is vacuumed at its interior by a non-illustrated pump. Inside the vacuum chamber 110, a target 112 for material of an amorphous film is mounted on a target holder 14, and laser light 16 from a non-illustrated laser light generator means is irradiated to the target 112 via a condenser lens 118 and a transmitting window 120. The target 112 is rotated at a constant speed by a d.c. motor 122 so that the target 112 is prevented from being damaged due to heat of the laser light 116.

A substrate holder 124 is disposed in confront­ing relation to the target 112 with a predetermined distance therebetween. A substrate 126, on which par­ticles evaporated from the target 112 are deposited to form a film 126a as described below, is mounted on the substrate holder 24. In the illustrated embodiment, glass is used for the substrate 126.

The substrate holder 124 is connected to the ground and the target holder 114 is connected to a d.c. power source 128, giving a desired potential dif­ference between the target 112 and the substrate 126. The d.c. power source 128 is composed of a switch 128a, a positive variable power source 128b and a neg­ative variable power source 28c, keeping the target 112 at a desired potential.

This application of potential is performed on a single metal or alloy, such as of Fe or Ni, which re­quires a high cooling speed. The application of potential can increase the energy of the charged com­ponent in the evaporation material to increase the cooling speed of the evaporation material, can break the chemical bond in the deposited film 126a, can put the high-energy evaporation material into the film to agitate the atom arrangement of the film 126a, thus making the film structure amorphous. At that time, if a positive potential is applied, the negatively charged particles in the emitted material will be repelled, and the negatively charged particles will be accelerated. Reversely, if a negative potential is applied, the negatively charged particles of the emitted material will be accelerated, and the posi­tively charged particles will be repelled.

Therefore, by applying the positive or negative potential, it is possible to increase the energy of the evaporated material, increase the cooling speed, breaking the chemical bond in the deposited film 126a and put the high-energy evaporation material into the film 126a, thus making the film structure amorphous.

The substrate holder 124 and the target holder 114 are supported on a positioning rotary stage 130 via an insulator 132.

Experiment 1

To form an amorphous pure iron film, pure iron was mounted on the target holder 114, and then the in­terior of the vacuum chamber 110 was vacuumed at lower than 1x10⁻⁵Torr.

Then, using KrF excimer laser, which can produce a high output (wavelength of 249 nm, pulse width of 16 nsec, pulse frequency of 25 pulses/sec and pulse ener­gy of 250 mJ), laser light 116 was irradiated to the target 112 of pure iron (99.999% purity) for 20 minutes while the target 112 was rotating at 20 rpm. The angle of irradiation of laser light with respect to the normal of the surface of the target holder 114 was about 45°, and the diameter of the spot of the laser light 116 irradiated on the pure-iron target 112 was about 6x10⁻³cm².

Subsequently, a predetermined potential is ap­plied to the target holder 114 by the d.c. power source 128. As a result, an amorphous pure-iron film 126a was formed on the glass substrate 126.

FIG. 14, (A), (B) and (C), shows the results of X-ray diffraction of the amorphous pure-iron film 126a when the applied voltage was 1 kV, 0 kV and -1 kV.

In FIG. 14, the horizontal coordinate represents the angle of incidence, and the vertical coordinate represents the intensity of X-ray. The X-ray diffrac­tion pattern of the applied voltage 0 kV shows a crys­tal structure having a peak 34 on the (110) plane. However, with the films 126a when the applied voltage was 1 kV and -1 kV, their X-ray diffraction patterns were broad patterns each not having remarkable peaks, showing a noncrystalline structure.

Thus, because the high-energy evaporation material is forced into the film by application of electric field, it is possible to form an amorphous pure-iron film.

FIG. 15 shows the change of magnetic flux densities when other metal elements were individually added to pure iron. According to the amorphous pure-­iron film of this example, the saturated magnetic flux density was 24 kG, which was relatively large, com­pared to that with the case where another element such as Ni, Si, Cr or Mo was added to pure iron.

Accordingly, with the amorphous pure-iron film of this embodiment, it is possible to realize a high magnetic flux density, compared to the conventional alloy film. This amorphous pure-iron film is particu­larly suitable for various kinds of parts or devices such as transformers and magnetic heads.

Experiment 2

To form an amorphous tungsten (hereinafter called "W" film, pure W was mounted on the target holder 114, and then the interior of the vacuum cham­ber 110 was vacuumed at lower than 1x10⁻⁵Torr.

Then, using KrF excimer laser, which can produce a high output (wavelength of 249 nm, pulse width of 16 nsec, pulse frequency of 25 pulses/sec and pulse ener­gy of 250 mJ), laser light 116 was irradiated to the target 112 of pure iron (99.999% purity) for 20 minutes while the target 112 was rotating at 20 rpm. The angle of irradiation of laser light with respect to the normal of the surface of the target holder 114 was about 45°, and the diameter of the spot of the laser light 116 irradiated on the pure-W target 112 was about 6x10⁻³cm².

Subsequently, a predetermined potential is ap­plied to the target holder 114 by the d.c. power source 128. As a result, an amorphous pure-W film 126a was formed on the glass substrate 126.

FIG. 16, (A), (B) and (C), shows the results of X-ray diffraction of the amorphous pure-W film 126a when the applied voltage as 1 kV, 0 kV and -1 kV.

In FIG. 16, the horizontal coordinate represents the angle of incidence, and the vertical coordinate represents the intensity of X-ray. The X-ray diffrac­tion pattern of the applied voltage 0 kV shows a crys­tal structure having a peak 34 on the (110) plane. However, with the films 126a when the applied voltage was 1 kV and -1 kV, their X-ray diffraction patterns were broad patterns each not having remarkable peaks, showing a noncrystalline structure.

Thus, because the high-energy evaporation material is forced into the film by application of electric field, it is possible to form an amorphous pure-iron film.

According to this invention, it is possible to form an amorphous film of pure iron and pure W as well as another metal or alloy having a critical cooling speed lower than that of pure iron.

A metal target and a substrate are placed, in confronting relation, in a vacuum chamber whose inte­rior is kept in a high vacuum state, and laser light is irradiated to the surface of the target to emit a high-speed evaporation material from the target. The emitted material is then deposited on the substrate. The composition of this deposited film on the sub­strate is controlled by providing a direction selec­ting means and a speed selection means between the target and the substrate, or by applying a predetermined high voltage between the target and the substrate. Particularly, the application of the high voltage increases the cooling speed and impact energy of the evaporated material on the substrate to form an amorphous metal film.