JPH01179474A - Film formation by use of laser light or intense light - Google Patents

Abstract

PURPOSE:To form a film small in residual stress on a film forming face making use of active particles which fly from a target by a method wherein intense light lays such as laser lights or the like are irradiated onto a target, where the laser lights are irradiated onto a reflecting mirror and the reflected laser lights are irradiated onto the target. CONSTITUTION:A thin film forming base material 10 is placed on a base material holder 10', and a target 17 is provided to a target holder 18 facing the base material 10 apart from each other at a certain distance 31. A reflecting mirror 15 is provided between the base material 10 and the target 17, a laser light emitted from a light source 11 travel as laser rays 12 and 12' and a reflected laser light 16, which is concentrated and irradiated onto the target 17. Then, as the energy of the intense irradiating light is sufficiently larger than the coupling energy of the components of the target, a part of the components or the component elements are vaporized and grows to be fine particles, a cluster, or in an atomic state 23 as they are kept active, which fly and are evaporated on a film forming face as a film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to a physical vapor phase method using light.
apor deposition (PVD method)
Regarding.

The present invention relates to a film forming method in such a photo PVD method, in which laser light or strong light is reflected by a mirror and irradiated onto a target in order to uniformly irradiate a large area of the target. The present invention facilitates the manufacture of devices using crystal anisotropy of materials such as oxide superconducting materials, and also aims to obtain a large critical current density in the formed thin film when forming superconducting thin films. It is something.

"Prior Art" In recent years, polycrystalline or single crystal materials of oxides have attracted attention. In particular, ceramic-based superconducting materials are attracting attention.

This material was first developed by IBM's Zurich laboratory in Ba-
It has been reported as a La-Cu-0 (baraquo) based oxide high temperature superconductor, and also YBCO (YBazCu06-8)
system has become known. However, these methods only involve mixing the respective oxide powders and baking them into tablets.
Even if a Tc onset of 90K was obtained, it was not possible to form a sufficiently thin film. For this reason, the development of thin film technology is being pursued. One of them is sputtering method, CVD method (
chemical vapor deposition method) and electron beam evaporation method.

``Conventional Problems'' The potential for superconductivity of these oxide polycrystalline structures is that their critical current density is small. For this purpose, the a-b plane (also known as the 0-plane C)
All crystals must be oriented in the plane perpendicular to the axis. Furthermore, when the sputtering method is used, the composition ratio of the target and the composition ratio when the thin film is formed vary.

This has the disadvantage that many types of targets must be made. In the gas phase method, since the starting material is a gas, mixing is easy, but gaseous materials are inherently extremely expensive and harmful, so it is difficult to use in practice.

Further, the electron beam evaporation method is not suitable for forming a film over a large area, and it is difficult to say that any of the film forming methods to date are optimal.

For this reason, ■ The raw material is an oxide or a mixture thereof, so it can be supplied at low cost; ■ There is no deviation in the stoichiometric ratio depending on the film forming conditions; ■ Thin film formation is easy and mass production is possible. There was a need for a means that satisfies the following: (1) that orientation during film formation can be expected;

Because the present invention satisfies all of these objectives,
This was done in order to propose the VD method, mass-produce it, and enable film formation over a large area. This film formation method is particularly applied to the formation of thin films of oxide superconducting materials.

"Means to Solve the Problem" In the present invention, when a solid target is irradiated with intense light such as a laser beam, the laser beam is irradiated onto a reflecting mirror, and the target is irradiated with the reflected light. As a result, the active particles, active clusters, or active atoms of the composition flying from the target can be formed on the surface with less residual stress to form a film.

Furthermore, in the method of the present invention, as seen in the so-called sputtering method, a substrate on which flying particles have already been formed can be sputtered (
Theoretically, there is no need to physically strike the target, and the principle is that the active fine particles, active clusters, or active atoms are vaporized and sent flying by cutting with light energy that exceeds the bond energy between the atoms that make up the target using strong light. ing. Therefore, there is little mechanical strain remaining in the formed film. In addition, since it is pulsed light (pulse width is 100 ns or less, YAG laser has an extremely short pulse width of 40 to 800 seconds, and excimer laser has a pulse width of 5 to 30 ns), all areas irradiated with laser light can be treated with the same stoichiometric amount. It can be flown while maintaining the logical ratio and created on the surface to be formed.

In the present invention, the laser beam is not directly irradiated from a laser light source onto a target held under reduced pressure, but is irradiated onto a reflecting mirror (mirror) disposed in front of the target, that is, between the target and the surface to be formed. The reflected light is irradiated onto the target, and the irradiation is particularly focused on the target surface.

In the so-called photo PVD method, the distance between the facing substrate forming surface and the target is extremely small, 2 to 5 cm.

Therefore, even if this target is not directly irradiated with laser light, a large area of the target cannot be uniformly irradiated. However, by using the method of the present invention, even if this distance is narrow, by moving this mirror or variably controlling its angle, it is possible to uniformly scan and irradiate a large area target with an intense laser beam.

Also, if the target is 30cm to 1m wide (for example, 60cm wide)
Even if the target has a large area (cm (width) x 40 cm (length) x 5 mm (thickness)), a linear laser beam is irradiated onto the target using a mirror, and this mirror is irradiated with the laser parallel to the target surface. By moving the target while moving it, the laser beam can be irradiated over the entire large area with the same width as the target. Furthermore, it is possible to uniformly form a thin film over a large area on the corresponding surface to be formed. (As shown in Figure 1 and Example 1) Furthermore, by continuously moving this surface to be formed from one direction to the other, the width can be approximately the same and the length can be increased infinitely, making it possible to produce large areas or mass production. can do. (An example is shown in Figure 2 and Example 2)
If the thin film to be formed on this surface is made of an oxide superconducting material, the surface to be formed is heated to a lower temperature, preferably 200 to 500°C, and reactive atoms or reactive fine particles are made to react with each other in active oxygen. At the same time, the oxide superconducting material as a reaction product is arranged on the surface to be formed to form a film. This is possible because the pho+-pvo method has less residual mechanical strain during film formation. By doing this, for example, the critical current density in the 0 plane (plane parallel to the ab axis) is
'A/cm' or more (in this case, ab
The aim is to improve this to the point where it is possible to improve

Typical superconducting materials used in the present invention are oxides using elements of groups Ma and Ila of the periodic table of elements and copper.

The superconducting material of the present invention is (AI-X Bx)ycuzO
w x =0.1-1. y = 2.0-4.0 preferably 2.5-3.5. z=1.0-4.0 preferably 1.5-3.5. W = 4.0 to 10.0, preferably 6 to 8, which can generally be expressed.

A uses one or more of elements selected from the yttrium group and elements selected from other lanthanoids. The Yztrium family is defined in the Physical and Chemistry Dictionary (
According to Iwanami Yotsuten (published on April 1, 1963), Y (yttrium) and Gd (gadolium).

Yb (ytterbium), Eu (europium), Tb
(terbium), Dy (dysprosium), l1o (holmium).

Er (erbium), Tm (thulium), Lu (lutetium).

Sc (scandium) and other lanthanides are used.

Moreover, B is Ba (barium) and Sr (strontium).

One or more types of elements selected from Ca (calcium) are used.

In the present invention, an oxide superconducting material obtained by pre-sintering an oxide material using such an element is used as a target. This is a thin film forming method in which an oxide superconducting material is formed into a film under atmospheric pressure or reduced pressure that partially contains oxygen.

"Function" In the present invention, a method of irradiating the laser light parallel or perpendicular to the target surface in the photoPVD method was adopted. For this reason, particles flying from the target may adhere to the mirror, but it is possible to produce a large quantity of the film, and by controlling the temperature on the surface on which the film is formed, a film of good quality can be obtained. Furthermore, by applying a magnetic field at the same time, orientation became extremely easy. Also, the magnetic field is stronger <0.
Since it requires 1 T or more, preferably 1 to 5 T, it has the disadvantage that the device tends to be larger. However, since the formed film has almost no sputtering effect, it has the advantage that the critical current can be increased. Further, when an electric field is used in combination during film formation, although it has the advantage that plasma can be applied to a large area and the apparatus itself is inexpensive, it has the disadvantage that the sputtering effect cannot essentially be completely eliminated.

Examples will be shown below to further explain the present invention.

"Example 1" FIG. 1 shows the PVD apparatus used in the present invention.

In the same figure, this device includes a space (11) that can be maintained at atmospheric pressure or a reduced pressure state, and an electromagnet (20) that generates a magnetic field.
-1), (20-2) and its power supply (not shown)
, a turbo molecular pump (26), a rotary pump (28), a pressure adjustment valve (25), which constitutes the exhaust system,
Substrate holder (substrate holding means) (10'), film forming substrate (10), gas system (24), target (17),
Target holder (18), water cooling system (28), (
28”), laser light source (11), mirror (13)
, window (14), movable reflector (15), heating means (
33).

First, the thin film forming substrate (10) is placed on the substrate holder (10'), and the target (17) is placed on the target holder (10').
8), facing the base and at a certain distance (31)
placed apart from each other. A reflecting mirror (15) is provided between the base and the target, and the laser beam is emitted from the light source (11) (
12), (12”) and reflected light (16),
The target (17) is focused and irradiated. Then, because the irradiated intense light is sufficiently larger than the binding energy of the target constituent, the constituent or a part of its constituent elements vaporizes and becomes a fine particle, cluster, or atomic state while maintaining an active state (23). It flies and is deposited as a film on the surface to be formed. In order to maintain the active state necessary for film formation on this surface, the distance (31) is 1 to 10 cm.
For example, it will be necessary to make it extremely narrow, 3 cm. Then, this atmosphere (11) is set to 10-6 to 10-”torr.
It is not impossible to set the distance (31) to about 10 cm if the film is maintained at a constant temperature, but at 1 to 10 torr (the rest being oxygen), it is recommended to set it to 1 to 4 cm to ensure stable coating. This is extremely important. Therefore, if the target is to be directly irradiated with laser light, the laser beam must be irradiated at a small angle (32) of 5 to 20 degrees, which is close to parallel to the target, making it impossible to uniformly irradiate a large area of the target. However, in the present invention, as shown in FIG.
15) and 45 to 1 to the target surface.
It can be incident at an angle of 35° (32). Therefore, the location of the target to be irradiated can be focused strongly enough.

In this example, the substrate having the surface to be formed was an Mgo+ 5rTi03 or YSZ substrate having a (100) or (110) plane, or a silicon wafer with an insulating film formed on a portion of the upper surface for use in IC. This board holder (
10") was made of stainless steel to avoid disturbing the electromagnetic field as much as possible.

As part of the fabrication process, the entire structure was first assembled using a turbo molecular pump (
26), 1× by rotary pump (28)
Evacuate to below 10-'torr. Next, a non-product gas (a gas that does not constitute a post-decomposition reaction body) such as oxygen (6
) is introduced into the plasma generation region (1) through the 2SCCM gas system (7), and this pressure is applied to I
Let it be rr.

A YAG laser or an excimer laser (using KrF or KrC1) was used as a strong laser light source. The excimer laser beam was linearly incident (perpendicular to the drawing in FIG. 2), and the mirror (15) was formed into a lens shape so that the linear beam was focused on the target. And this mirror (1
5) was repeatedly moved vertically at a speed of 10 to 30 mm/min (30-2) to form a film.

When a YAG laser is used as the laser light source, since the depth of focus is large, the mirror (15) may be scanned in the horizontal or vertical direction, or the beam may be rotated on the target.

In addition, when using an excimer laser as a laser light source, since the depth of focus is shallow, a linear beam is created in advance using an optical system (not shown) and then passed through a window (14) and a mirror (15). 17) Irradiate on top. And mirror (15
) to the linear beam in the vertical direction (vertical direction in Figure 2) (
30-2) and irradiate pulsed light at 1 to 100 pulses/second, uniform irradiation over a large area becomes possible.

The target surface instantly becomes 2000 to 8
Since the temperature reaches 000°C, the target material in this irradiated area instantly vaporizes. This temperature is 1150°
C (the melting temperature of oxide superconducting materials), active particles, clusters, or atoms excited by such high energy are generated on the surface to be formed in the original crystal configuration, and the temperature is 150 to 500°. By depositing a thin film of this oxide superconducting material on the substrate (10) on the substrate holder (10') heated by the heater (33) at C,
An oxide superconducting thin film having an orthorhombic modified vervskite structure with a thickness of 1 μm = 1 mm could be formed.

Further, the critical current density was obtained by measuring 3 x 10'A/cm2 in a direction parallel to the substrate surface.

In other words, the X-ray diffraction results revealed that the crystal structure shown in Figure 1 was sufficiently formed during film formation and subsequent thermal annealing, and that the C-axis direction was also perpendicular to the surface on which the film was formed. Ta.

“Example 2” The component after film formation was YBazCuzOh~8
It was used so that That is, the base body (10) and holder (10'') in the apparatus shown in FIG. It was moved at a speed of 10 cmZ.Thus, countless substrates (10-1)
, (10-2), and (10-3) were able to form oxide superconducting thin films on the formation surfaces. Portions not shown are the same as in FIG. As a result, for a superconducting material thin film formed on a substrate such as glass, alumina, ZrO2, etc., the critical current density is 3.4 X 10'A/c.
I got mz. A Tco of 93K was obtained.

In the present invention, the direction of gravity may be set downward in the drawing or in a direction perpendicular to the drawing, depending on the design purpose.

"Example 3" In Example 1, the main part was made as shown in FIG. That is, a donut-shaped target (17), a donut-shaped substrate holder (10'), and a substrate (10) having a plurality of formation surfaces thereon were arranged.

Laser light (12') is irradiated from the center of the substrate holder,
The light (16) reflected by the reflector (15) is directed towards the target (
17) Irradiate on top. Then, the target composition was made to fly (23). The rest is the same as in Example 1.

The substrate is MgO (100) or 5rTiOz (100)
, the substrate temperature was 450°C. As a result, a thin film of 1 cm 2 or more could be obtained on this substrate even if the thickness was 1.5 μm.

In this embodiment, a method may be adopted in which a laser beam is irradiated from the target side and the laser beam is reflected onto the target by a mirror.

"Example 4" In Example 1, the main part is shown in FIG.

In this drawing, the laser beam (12) moves its position to (12'-
1).

(12'-2) and variable (30-4). Then, a laser beam was irradiated onto a reflecting mirror (15) having a triangular pyramid shape having a curved surface and rotating about the shaft (32). Then, since this reflecting mirror has a curved surface, at a certain position (16-1
) can be irradiated with laser light, and (16-2) can be irradiated with laser light at other positions. In this way, all positions of the target (17) can be irradiated with laser light. However, in this case, it is difficult to focus on the target, so it is better to use a laser with a large depth of focus, such as a YAG laser. The rest is the same as in Example 1.

In Example 1, the substrate was made of MgO(110), 5r
TiO+ (110) was applied. Then, a magnetic field was applied to the surface to be formed at 0.2 T and the substrate temperature was set to 450°C. Then, a single crystal thin film close to 5 mm2 was deposited on this substrate at 3 μm.
It was possible to obtain a film with a thickness of m.

"Example 5" In this example, the oxide superconducting material made in Example 1 was formed into a film using the apparatus shown in Fig. 1 so that the magnetic field was directed in the C-axis direction in accordance with the pre-made crystal plane. did. the result,
A critical current density of 4.5 Xl05A/cm2 was also obtained.

In the present invention, the molded product is in the form of a thin film. However, this shape can be modified to a membrane structure, a layer structure, or a line structure with a thickness of 3 to 30 μm according to the needs of the market.

"Effects" The present invention has made it possible to create a thin film of an oxide superconducting material that operates at temperatures above liquid nitrogen temperature, which was previously considered impossible, by aligning its crystal axes.

Furthermore, in order to make it easier to match the layer structure between the polycrystalline structures in the compound of this target material, a plurality of elements Ila and I[Ia in the periodic table of elements may be mixed. As shown in the present invention, by applying a magnetic field during heating to further unify the molecular arrangement, the presence of voids and lowering of the barrier height of grain boundaries can be further eliminated in the final completed compound. Therefore, Tc onset, Tco
It is estimated that the temperature can be increased even further.

In the present invention, the film formed is mainly made of oxide superconducting material. However, the method of the present invention is effective for forming thin films of all kinds of materials such as metal materials, semiconductor materials, magnetic materials, and transparent conductive film materials. However, the method of the present invention
It is extremely effective for film formation using a compound containing multiple elements as a starting material, and is particularly effective because the stoichiometric ratio of the compound is almost the same as that of the target after film formation. To this end, it was extremely effective to avoid repeatedly applying pulsed light to the same location and to scan the light beam while cooling the target with water so that the target itself would not generate heat, causing the particles, clusters, and atoms to fly.

In the present invention, with respect to the name photo PVD method, the terms evaporation method using a laser beam, laser beam, and sputtering method may also be used. However, since laser beams use the concept of sputtering (collision), photoP
It seems that the term "VD method" is more appropriate. The vapor deposition method uses the principle that atoms are evaporated by heating the evaporation source so that the thermal energy is greater than the binding energy. However, since laser light is optical energy and the flight of fine particles and clusters is large, the photo PVD method seems to be a more appropriate term.

[Brief explanation of the drawing]

FIG. 1 shows an outline of a photophysical vapor deposition apparatus used in the present invention. FIGS. 2, 3, and 4 show important parts of the photophysical vapor deposition apparatus used in the present invention.

Claims (1)

[Claims] 1. When irradiating a solid target with a laser beam or strong light to cause active particles, active clusters, or active atoms of the solid target to fly, the laser beam or strong light is applied to the solid target. Irradiates the mirror surface in front,
A film forming method using laser light or strong light, characterized in that the solid target is irradiated with light reflected from the mirror surface. 2. In claim 1, the laser beam or intense light is characterized in that the laser beam or intense light is irradiated onto a solid target by rotating the mirror surface, rotating the angle of the mirror surface, or moving the mirror surface. A film formation method using 3. In claim 2, the film to be formed is (A_1_-_xB_x)_yCu_zO_wx=0
．． 1-1, y=2.0-4.0, z=1.0-4.0,
w=4.0 to 10.0, A is Y (yttrium),
Gd (gadolinium), Yb (ytterbium), Eu (
europium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium),
Consisting of one or more elements selected from Tm (thulium), Lu (lutetium), Sc (scandium), and other lanthanoids, B is Ba (barium), S
A film forming method using laser light or strong light, characterized in that the film is made of an oxide superconducting material containing one or more elements selected from r (strontium) and Ca (calcium).