JPH06279180A - Production of crystal thin film - Google Patents

Abstract

PURPOSE:To form a good-quality thin film by forming the thin film in such a manner that the average molar number of the atoms or molecules deposited by evaporation and stuck onto a substrate during one supply period attains the value below the molar number for one layer of the unit lattice of the desired compd. crystal thin film. CONSTITUTION:UV light from an excimer laser device 1 is passed through an optical box 2 subjected to gaseous N2 purging and a window 5 and is made incident on a vacuum chamber 3 in which the pressure of an atmosphere gas such as O2 is maintained under 0.01 to 1000mTorr. This UV light is condensed by a condenser lens 4 and a target 6 formed by combining plural materials, such as YCu and BaCu alloy, is successively irradiated with this condensed light in a specified period. The surface of the target 6 is locally heated for a short period of time by the irradiation with the UV rays, by which the target materials are evaporated and the atoms or molecules are deposited by evaporation on the substrate 8 of MgO single crystal, etc., arranged to face the target in such a manner that the average molar number of the atoms or molecules deposited by evaporation and stuck onto the substrate during one supply period attains the value below the molar number for one layer of the unit lattice of the desired compd. crystal thin film. The crystal thin film of the same compsn. as the compsn. of the desired compd. such as YBa2Cu3O7 is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a crystal thin film. More specifically, it relates to a method of producing a compound crystal thin film on a predetermined substrate by irradiating a target with an electromagnetic wave beam to evaporate the target, and is useful for producing a thin film for an electronic device using a ceramic crystal thin film containing a metal component and oxygen. Regarding the method.

[0002]

2. Description of the Related Art In recent years, the development of various lasers and their applications have been remarkable, and the application of high-power lasers to thin film fabrication has been rapidly developing as an important application field. As a method for producing such a thin film, a method generally known as laser ablation (for example, Japanese Patent Laid-Open No. 2-1768).
No. 5, Applied Physics Lett
ers, vol. 54, no. 11 pp. 861-863,
Reference), and preparation of an oxide superconducting thin film without post heat treatment has been reported.

In this laser ablation method, the target material is evaporated by irradiating the target with a laser pulse having a large energy density, and a thin film having a composition close to the target composition can be formed on the substrate. Further, in recent years, a vapor deposition method incorporating a method of slowly forming one atomic layer at a time in a relatively high vacuum for about 100 seconds or more while observing RHEED vibration has been studied. This evaporation method is
er by Layer is also referred to as laser vapor deposition. For example, laser vapor deposition of Layer by Layer for each atomic layer is described in Jpn. J. Appl. Ph
ys. , 31 (1992) L217-220. This method provides significantly lower electrical properties than bulk materials of the same composition. This is because it takes a long time to reach the composition of the target thin film, and the thin film is formed in a state in which it deviates from the target composition despite the formation of a sufficiently thick atomic layer on the substrate. It is thought that this is because there are many other phases and defects. In addition, as an example of performing the post-heat treatment, as laser vapor deposition of Layer by Layer for each block layer, Jpn. J. Appl. Phys. , 28 (1989) L823-826.

Here, the laser ablation method will be described while explaining the laser vapor deposition apparatus with reference to FIG. FIG. 1 is a schematic diagram showing an example of a laser vapor deposition apparatus. The ultraviolet light from the excimer laser generator 1 is
The light enters the vacuum chamber 3 through the nitrogen-purged optical box 2 and the window 5 of the vacuum chamber. This ultraviolet light is condensed in front of the target by the condenser lens 4 arranged in the optical box and is applied to the target 6. The light applied to the target locally heats the target surface for a short time. For example, the excimer laser has a pulse width of 10 to 30.
A short time of nsec is common. Upon receiving this heating, evaporation starts from the target surface, and the target material is discharged toward the substrate 8 arranged facing the target and deposited on the substrate. The target holder 7 of the laser deposition apparatus is preferably rotatable, and in some cases, a plurality of targets are arranged in the target holder so that each target can be rotated and the positions of different targets can be exchanged. May have. The substrate holder 9 is normally rotatable,
Has a heating function. When actually manufacturing an oxide superconducting thin film, an oxidizing gas such as oxygen is supplied to the vacuum chamber through a gas inlet. A shutter 10 is usually provided between the target and the substrate holder.

[0005]

In the conventional laser ablation method, it is a great advantage that the metal composition of the thin film to be produced has the same composition or almost the same composition as the composition of the target. ² J / cm ² per pulse using a target close to ceramic thin film composition
Vapor deposition is performed by irradiating the laser with the above large energy density. However, when vapor deposition is performed under these conditions, the composition of the target surface changes as laser irradiation is repeated, the surface shape of the target changes and the deposition rate decreases significantly, and particles are generated on the thin film surface. was there. On the other hand, when irradiating a target close to the target ceramic thin film composition with a laser having an extremely low energy density per pulse for vapor deposition, the metal composition of the thin film to be produced may deviate greatly from the composition of the target, or the impurity phase It was considered to be unfavorable because it would be formed.

In laser vapor deposition using a target close to the target ceramic thin film composition, the thin film composition is determined by the distance between the substrate and the target, atmospheric gas pressure, laser energy density, etc., but the preferred range is narrow, for example, between the substrate and the target. The distance is often limited to 10 cm or less. This is because the vaporized atoms or molecules for vapor deposition are significantly scattered by the atmospheric gas, and the influence of the scattering varies depending on the atomic species and molecular species, so the composition of the deposited thin film changes, and the effect is that the substrate distance is long. This is because it becomes larger. In order to remove this limitation, when a target having a composition different from the target thin film composition is vapor-deposited and an attempt is made to control the composition of the vapor-deposited thin film, such a target has grains and impurity phases having a target compound composition. It becomes a mixture with the deposited one, and the target surface composition fluctuates more than a normal target, and grains are easily formed on the vapor-deposited thin film.

As described above, when a thin film made of a multi-component element is produced from a target containing the same number of multi-component elements or a target made of the same number of metal elements,
There are many restrictions, and in particular, the target material cannot be freely selected. In particular, when there is no alloy compound corresponding to the compound to be thinned, a metal target can be obtained only by a method such as powder metallurgy. For example, YBa ₂ Cu ₃ O ₇ exists as a compound but decomposes without melting itself, and a compound having a YBa ₂ Cu ₃ composition cannot be obtained.

In order to essentially solve such a problem,
We examined laser deposition by sequentially irradiating multiple targets with different composition from the target metal composition of the thin film, and made it possible to select the target material from a wide range of materials. We tried to apply it to the vapor deposition method. In addition, we tried to make it possible to select a target material whose composition does not fluctuate easily and a target material that makes it easy to manufacture a dense target, and to control the composition of the vapor-deposited thin film in a wide range of parameters and to suppress grain generation.

[0009]

The inventors of the present invention have surprisingly been able to unexpectedly irradiate a target having a metal element composition different from that of a target thin film with an electromagnetic wave beam at high speed.
Atmospheric pressure, substrate temperature of 100 mtorr, and 650 ° C. under the same conditions as in the conventional laser deposition method, the composition of atoms and molecules to be deposited on a very slow time scale compared to the time scale of a chemical reaction of several hundred milliseconds. The inventors have found that a thin film with high characteristics can be obtained without forming precipitates and the like, and that the target is less deteriorated on the surface despite the fact that the above conditions are met, and have reached the present invention.

That is, the gist of the present invention is to prepare a crystal thin film of a compound containing two or more kinds of metal elements on a substrate,
A plurality of targets containing at least one type of metal element constituting the compound and having different compositions from each other are sequentially irradiated with an electromagnetic wave beam at a constant period, and atoms or atoms such that they have substantially the same metal composition as the compound on the substrate. When supplying molecules, the average number of moles of vapor-deposited atoms or molecules attached to the substrate during one supply cycle is set to be less than the number of moles of one unit lattice of the compound crystal thin film. And a method for producing a crystal thin film. The present invention is particularly useful when a crystalline thin film is produced by reactively vapor-depositing a ceramic thin film made of metal and gas in an atmosphere gas containing the gas element.

In the following description, atoms supplied from the target, reaching the substrate, adhering, and being incorporated into the crystal structure,
The number of molecules or the number of moles of each element is converted into the number of atoms or molecules to be vapor-deposited. this is,
It corresponds to the number obtained by subtracting the reduced number of atoms scattered from the substrate due to re-evaporation or re-sputtering from the reduced number of atoms flying to the substrate. In the present invention, by independently controlling the evaporation rates of the constituent elements, a desired composition can be obtained over a wide range of the distance between the substrate and the target, the atmospheric gas pressure, and the laser energy density. A target material is selected, and deterioration of the target surface can be suppressed.

When the target compound is composed of a plurality of metal elements and a gas element, a metal element atom capable of forming a thin film with a sufficient thickness of only one kind of metal element constituting the compound by the metal element and the gas component. Alternatively, when molecules are supplied onto the substrate, the crystal phase of the metal element and the gas component is stabilized, and the target compound crystal cannot be formed even if the other remaining constituent metal elements are supplied later. In order to avoid this, atoms or molecules that are not incorporated in the compound thin film crystal and can move sufficiently and have a compound composition close to the target compound composition are present on the substrate or already formed thin film layer, and If it exists at a short migration distance below the lattice, a compound crystal structure having a desired composition can be obtained.
Therefore, in the present invention, when supplying atoms or molecules having a metal composition almost the same as that of the target compound, 1
The vapor deposition is performed so that the average number of moles of atoms or molecules vapor-deposited during the supply cycle and attached on the substrate is less than the number of moles of one unit lattice of the target compound crystal thin film.

The moving distance of the unit lattice is defined as the unit lattice length of the epitaxially grown target compound in the direction of the orientation axis, and is the distance over which atomic molecules must move even in ordinary laser deposition. Further, the number of moles of one unit cell layer means the number of moles of each element when the target compound crystal has the desired orientation on the surface of the substrate and exactly one layer uniformly covers the entire surface of the substrate. Is a number, which defines the patent. Specifically, AxByCz with G as a gas component
When a compound represented by Gw is oriented in the a-axis direction of this compound to form a crystal thin film, the number of moles of one unit lattice is the a-axis length and the area of the substrate (more strictly, the thin film formation region). The volume obtained by multiplying by is divided by the unit cell volume of the target compound, and the number of moles of A is multiplied by x, the number of moles of B is multiplied by y, and the number of moles of C is obtained by multiplying by z. To be

Practically, it is simpler to calculate the number of unit lattices in the thin film prepared by vapor deposition film thickness measurement or to analyze the deposited element amount, and convert it to the film thickness to express the deposited amount. Is. In particular, a value obtained by dividing the film thickness obtained from the analysis of the amount of attached elements by the number of supply cycles of vapor-deposited atoms or molecules is shorter than the a-axis length, which is another expression of the above requirement. More stringent conditions include conditions where this value is shorter than the shortest axis of the unit cell. In addition, it is preferable that the vapor deposition be started after the vapor deposition rate is fairly stable.

For example, when a YBa ₂ Cu ₃ O ₇ thin film is sequentially formed, the substrate temperature is about 550 to 650 ° C. and the oxygen gas pressure is 1
At 0 to 100 mtorr, many precipitates are generated when the cycle of supplying atoms and molecules for several minutes or more so that the composition ratio of Y: Ba: Cu on the substrate becomes 1: 2: 3. In general, a supply cycle that gives a composition that is almost the same as the desired thin film composition is 1 second or less, preferably 0.3 second or less, and the problem of deposit formation is greatly improved. Therefore, when a plurality of targets having different compositions containing at least one or more metal elements are sequentially vaporized to supply atoms or molecules onto the substrate, the composition of the supplied atoms or molecules is the target compound. It is preferable that the period of the cycle that is almost the same as the metal composition is within 1 second. For this reason, atoms or molecules having the same metal composition as that of the compound are supplied onto the substrate, and the average number of moles of the atoms or molecules to be vapor-deposited on the substrate during one supply cycle is the unit cell 1 of the compound crystal thin film. It is necessary to make it less than the number of moles of the layers.

In the vapor deposition method of the present invention, in order to make it easy to avoid compositional changes and surface shape deterioration due to heating of the target surface, it is preferable to use a target containing only one kind of metal element as the metal forming the target ceramic thin film. Prepare only the types of elements and apply sequential vapor deposition. Alternatively, it is preferable to use a target of a composition that is as stable and dense as possible, or a composition that easily obtains an alloy. Furthermore, it is preferable that the difference between the boiling points of any two kinds of the metal elements is not extremely different, and it is preferable to avoid the combination in which the ratio of the melting points is different by about twice or more. Examples of the target to be used include a metal target, an alloy target, and a target of a ceramic compound such as an oxide or a nitride thereof, and a target that can be formed by melting is particularly preferable.
Generally, pure metals, alloys and refractory oxides are the preferred target materials and are composed of fewer elements, eg 2 elements or less, with pure metals or alloys being particularly preferred.

Further, in the periodic table, Zr and Hf, which are all solid-solved in the same group, and Fe and Co, which have similar physical properties and melting points close to each other, are regarded as substantially one element. It is also possible. Further, for example, when forming an oxide thin film, using a pure metal or alloy as a target,
Since these melting points are usually lower than those of the respective oxides, the particles are easily melted even when they come to the substrate, which is effective in improving the generation of particles. Even when the target is used for a long period of time and a fine structure is formed and the surface shape is deteriorated, it can be easily repaired by heating below the melting point, and there is an advantage that heating can be performed in the vapor deposition apparatus.

As a technique similar to the method of the present invention, there is a laser deposition method using the above-mentioned Layer by Layer. This method is essentially different from the present invention in that each atomic layer of the unit cell is laminated one by one. In the laser deposition method using Layer by Layer, the cycle time for supplying the deposition material that achieves the target thin film composition to the substrate is on the order of 100 seconds, but in the present invention, the difference is of the order of 100 milliseconds. Achieved in the meantime. Due to this difference in time scale, in the method of the present invention, the component gas is sufficiently incorporated into the crystal thin film at a low vacuum atmosphere gas pressure of about 100 mtorr without selecting an appropriate substrate temperature and activating the atmosphere gas. A thin film can be formed without forming an impurity phase, and a high-performance thin film can be easily obtained.

The same effect as that of the present invention can be obtained by simultaneously irradiating a plurality of targets with an electromagnetic wave beam. A plurality of electromagnetic wave generators are used, or laser light from one electromagnetic wave generator is split by a beam splitter. Realized by However, it is preferable that the positions of the vapor deposition sources be as close as possible.

When performing sequential vapor deposition, it is more convenient to use a pulsed electromagnetic wave beam for controlling the irradiation time of the electromagnetic wave beam for different targets and for changing the target to be changed one after another. Since heating is little, evaporation efficiency is good and impurities are unlikely to be generated. When a continuous wave electromagnetic wave beam is used, FIG.
It is possible to control the composition by rotating and using a target having a structure as shown in FIG. That is, FIG.
FIG. 4 is a diagram showing an example of a target for producing a thin film containing metal A: metal B: metal C at an atomic ratio of x: y: z by using a continuous wave electromagnetic wave beam, and a constant amount of each metal. When the evaporation rates with respect to power are a, b, and c, the area ratio of each metal in the target is x / a: y / b: z / c.

In the apparatus used in the vapor deposition method of the present invention, when the pulsed electromagnetic wave beam is used for successive vapor deposition, the electromagnetic wave beam is applied to a specific target at a specific cycle so that the rotation of the target and the oscillation of the electromagnetic wave are synchronized. To be irradiated. In this case, if a deposit other than the target composition is heated and present on the substrate for a long period of time, an impurity phase is generated.Therefore, in order to obtain the target composition in a short time, it is possible to sequentially apply electromagnetic waves to different targets at high speed. Irradiation with a beam is preferable.

In the vapor deposition method of the present invention, even if only the effect of irradiating an electromagnetic wave beam having an extremely low energy density and heating the target surface is used, it is sufficient to increase the repetition frequency and the beam shape of the electromagnetic wave beam. It is also possible to obtain the vapor deposition rate. Moreover, the composition can be controlled by changing the energy input to each target, the energy density of the electromagnetic wave beam, and the number of irradiation pulses. An example of an electromagnetic wave beam irradiation cycle in the sequential vapor deposition method of the present invention, and a case of producing a thin film containing metal A, metal B and metal C are shown in FIGS. 3 and 4. In FIGS. 3 and 4, the horizontal axis represents time, the position of the bar represents laser irradiation time, and one cycle shown in the drawings corresponds to almost one rotation of the target holder. 3 and 4, the length of the rod corresponds to the laser energy density, and the longer the rod, the larger the energy density. FIG. 3 shows the case where the target A is irradiated with laser three times, the target B is irradiated twice, and the target C is irradiated four times in one cycle with a constant energy density. FIG. 4 shows laser irradiation of each target once by changing the laser energy density. The case of irradiation is shown.

For example, YBa₂Cu₃O₇C-axis alignment film
When manufacturing, all BaO or Ba target, CuO
Or Cu target and Y₂O₃Or use Y target
I mean. YBa₂Cu₃O₇Number of metal elements per unit cell of
Since there are six, the number of moles covered by one atomic layer on the substrate is 6
If a certain number of moles less than or equal to 1 is written as z, it is in an oxidizing atmosphere.
Then, BaO or a Ba target is vapor-deposited with z mole number of BaO.
The CuO or
With the number of pulses of CuO vapor deposition on the Cu target
Irradiate an electromagnetic wave beam, and further BaO or Ba target
Electromagnetic wave with a pulse number that vaporizes BaO in z mole number
After irradiating the beam, CuO or Cu target Cu
O is irradiated with a pulse number electromagnetic wave beam for vapor deposition of z mole number,
Then Y ₂O₃Alternatively, the Y-O layer is almost z mole on the Y target.
After irradiating an electromagnetic wave beam with a number of pulses for vapor deposition, Cu
CuO is vapor-deposited on the O or Cu target in a z-mol number.
Repeatedly irradiating the electromagnetic beam with the number of pulses
You

It is preferable to perform these operations at a somewhat high speed by synchronizing the target selection with the electromagnetic wave beam oscillation by a computer or an electric circuit. Further, when the vapor deposition rate is significantly different depending on the target, it is preferable to lower the irradiation electromagnetic wave beam energy density of the target having a high vapor deposition rate for vapor deposition. For this purpose, it is preferable to change the position and type of the condenser to change the degree of focusing of the electromagnetic wave beam or to insert an attenuator of the electromagnetic wave beam in synchronization with the selection of the target.

As the component gas, for example, O ₂ , O ₃ , O, NO ₂ , N ₂ O or the like is used when forming an oxide, and S, S _2n (n = 1 to
4), SF ₆ or the like is used, and if it is a nitride, N ₂ , N
H ₃ and N can be used. When a gas is activated and used, a high frequency electric field (RF), a DC electric field to form an activated gas (radicals, monatoms such as oxygen atoms, active molecules such as ozone), and ozone to form ultraviolet rays and the like. Etc., and the preferable atmospheric gas pressure is 0.01
~ 1000 mtorr, more preferably 0.1
~ 1000 mtorr.

It is preferable that the electromagnetic wave beam has a wavelength that has a low reflectance and a high absorption coefficient with respect to the target material and a high light energy absorption efficiency. Generally 190 nm
To 350 nm ultraviolet light is easily absorbed by many substances,
Also, it is easy to obtain a laser with a large output per pulse. As a generation source of such a laser, an excimer laser, a YAG laser combined with a non-linear optical element to shorten the wavelength, an Ar ion laser, a carbon dioxide laser, or the like is used. Particularly, a pulse laser in which a nonlinear optical element is combined with an excimer laser or a YAG laser is preferable.

The output of the pulse laser is 1 per pulse
About 0 to 1000 mJ is preferable. The energy density is 0.001 to 10 J / cm ² , preferably 0.1.
About 1 to 1 J / cm ² is used. The pulse width is usually about 10 to 100 nsec. As the output of a semiconductor laser increases, a target that easily absorbs light and evaporates even if the wavelength is shortened by directly or in combination with a non-linear optical element, for example, Japanese Patent Application No. 4-227274 by the present inventor.
It is considered possible to use the metal halide compounds described in JP-A No. 1994-101, etc. to perform vapor deposition with a semiconductor laser having an energy per pulse of about 1 mJ.

The vapor deposition method of the present invention is applied to the production of ceramic crystal thin films composed of a plurality of metal elements, when the compound to be thinned is composed of metal elements having greatly different melting points, or when decomposition or phase separation easily occurs at high temperature. Especially useful. As the target, it is more preferable to use a target containing only two or less main component elements as described above, and vapor deposition is performed in an atmosphere containing a gas element in the ceramic crystal thin film. For example, among oxides composed of rare earth elements, one kind of alkaline earth metal, and transition metal elements, YBa ₂ Cu ₃
It is called a compound having a crystal structure called an O ₇ type 123 structure or a (Ln, M) ₂ CuO ₄ (Ln is a rare earth element and M is an alkaline earth metal) type 214 structure. It is effective for forming a thin film of a compound having a crystal structure.

These substances include rare earth elements and copper, and other elements.
, The electrical characteristics may change, but
It is known that sex hardly changes. For example Y
Ba ₂Cu₃O₇Type oxides are rare earth elements and other sources of copper
There is a difference of several tens of degrees in the proper substrate temperature when replaced with a raw material
The vapor deposition conditions of are almost the same. Therefore, the steam of the present invention
The deposition method is also sufficient for laser deposition of these various substances.
It is valid. Also, for example, Bi₂Sr₂Ca_(n-1)Cu_nO
_{(2n + 4 + d)}(N is 1, 2 or 3 and d is 0 <d <1
is there. ) Bi-based copper oxide superconductor, rare earth gar
Net oxides such as rare earth garnet oxides, orthofe
Lights, dielectrics such as BaTiO₃ , SrTiO₃ , P
Also useful for preparing LZT ((Pb, La) (Ti, Zr) O)
Is. Furthermore, the vapor deposition method of the present invention can be applied to many other ceramics.
Mick (metal element and N, P, O, S, Se, Te, F,
Preparation of thin films of compounds with low boiling elements such as Cl, Br, I
It seems that there is sufficient effect.

As the substrate, glass, plastic, Si, Ge, GaA is used in the case of producing an amorphous vapor-deposited thin film.
It may be a compound semiconductor such as s or a metal, but when the substrate is heated from room temperature in order to produce a polycrystalline vapor-deposited thin film, it is important that it does not react with the vapor-deposited thin film at the substrate temperature used. A stable and inexpensive substrate such as yttrium-doped zirconia oxide) is used even at high temperatures. In addition, MgO, SrTiO ₃
You may use what formed the intermediate | middle layers, such as. In order to produce a single crystal thin film, the lattice matching with the vapor-deposited thin film is further important. For example, in a copper oxide superconductor, MgO, SrT
iO ₃ , LaAlO ₃ , NdGaO ₃ or the like is used.

[0031]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. Example 1 Preparation of YBa ₂ Cu ₃ O ₇ thin film Cu particles having a purity of 99.99% and Y particles having a purity of 99.9% were mixed at a molar ratio of 1: 1 and melted in an argon gas by an arc melting method. A YCu alloy was obtained. Also, the purity is 99.99%
Cu particles and Ba particles having a purity of 99.9% were mixed at a molar ratio of 1: 1 and melted in an argon gas by an arc melting method to form Ba particles.
A Cu alloy was formed. A target obtained by repeating this target 5 times in the same vapor deposition experiment as in this example was used in this experiment.

A MgO single crystal having a (100) plane as a substrate plane is sequentially trichlene, acetone, methyl alcohol, and IP.
A substrate was prepared by cleaning with A and exposing to UV light and ozone for 10 minutes in an ozone generator using UV light in air to further degrease the surface. As an electromagnetic wave beam generator, 19
Using an ArF excimer laser generator that generates a laser beam of 3 nm, in order to adjust the beam shape, locate the laser emission port with an optical path length of about 150 cm from the target holder, and focus it 2 cm before the lens target with a focal length of 350 cm. did. In addition, about 0.
An electric beam scanner (Galvano scanner manufactured by General Scanning Co.) having a deflection angle of 5 degrees is arranged, and the laser beam is swung laterally.

A target holder capable of fixing a plurality of targets was attached to the tip of a magnetic coupling type rotation introducing terminal, and this rotation introducing terminal could be driven from the outside of the vacuum device by a servomotor with an encoder. This servomotor is controlled by a pulse generator. The encoder output from the motor and the origin detection output are sent to an electronic circuit, and when each pulse is totaled and a specific number of pulses is reached, a laser drive pulse is sent to the laser to cause the laser to oscillate within a few microseconds. By this method, laser irradiation is performed on a specific position of a specific target with a precision of 0.36 degrees in a specific cycle for each individual target. still,
A computer programs the laser oscillation operation circuit in advance before vapor deposition.

The above YCu, BaCu, and YCu alloy targets were mounted in this order at intervals of about 52 degrees in the direction of rotation of the target holder, and the MgO single crystal substrate was placed 7 cm from the target.
The substrate was separated and opposed to the target, fixed on the substrate heater with silver paste, and the vacuum chamber was evacuated. The substrate was heated to about 750 ° C. and kept at 3 × 10 ⁻⁶ torr or less in a vacuum chamber with a mass flow meter (flowmeter) at a flow rate of 70 sccm.
0 mtorr was filled with pure oxygen gas and left for 20 minutes.
In this state, the substrate temperature was lowered to about 650 ° C., the orifice was changed, and 100 mtorr was filled with pure oxygen gas at a flow rate of 90 sccm. Energy per pulse of laser is 150mJ, energy density on the target is 1J
/ Cm ² slightly lower and target holder 210 rp
Rotate at m, irradiate the first YCu target and BaCu target once per revolution, irradiate the second YCu target twice per revolution, and irradiate the target at different angles for each revolution. It was set to shift the position. At this time, the vapor-deposited atomic molecules of Y: Ba: Cu = 1: 2: 3 are supplied in about 100 milliseconds.

After the shutter is closed for 1 minute to pre-sputter the target surface, this vapor deposition is started and continued for 90 minutes. Then, the vacuum chamber is filled with pure oxygen at 1 torr or more, and the substrate heating is immediately stopped, and the heating is continued for about 30 minutes. It was cooled below to ° C. The obtained thin film was quantitatively analyzed for the elements by a fluorescent X-ray apparatus which had been calibrated by ICP analysis method (inductively coupled plasma emission analysis method) in advance. As a result, the composition ratio of Y: Ba: Cu was 1:
At 1.8: 3.2, a thin film having an estimated film thickness of about 400Å was obtained. At this time, the converted average film thickness of atoms and molecules during the period in which Y: Ba: Cu = 1: 2: 3 is supplied is 0.01Å, and the minimum lattice spacing of the unit cell is about 3. It is sufficiently smaller than 8Å, which corresponds to about 40 times the number of moles when one unit cell covers the substrate. Also, the superconducting transition temperature of the thin film was 87 K, and only the diffraction peak of YBa ₂ Cu ₃ O ₇ was observed in X-ray diffraction, and a c-axis oriented thin film in which a-axis orientation was partially mixed was obtained by indexing. I found out that

In the SEM photograph, a precipitate of about 0.2 μm was seen, but a particle of about 0.5 μm was 1 per 100 μm square.
About 0 particles were observed, but almost no particles having a size of 1 μm or more were observed over the entire area. The surface of the YCu target remained extremely smooth, and the surface of the BaCu target was also smooth. In addition, when the vapor deposition rate and composition of each target were measured using this target, the vapor deposition rate and composition of the second and subsequent times coincided with the experimental error range for each vapor deposition.

Comparative Example 1 99.9% YBa ₂ Cu ₃ O ₇ powder was added at room temperature to 200 kg /
Press at a pressure of cm ² and press in air at 950 ° C for 10
After sintering for a time to produce a sintered body target, vapor deposition was performed 5 times in accordance with Example 1, and then used in the experiment of this comparative example.
In this comparative example, unlike the sequential vapor deposition of Example 1, YBa ₂ Cu ₃
The deposition time was set to 30 minutes using only one target having an O ₇ composition, and other conditions were the same as in Example 1. At this time, the thin film composition was Y: Ba: Cu = 1: 1.3: 2.6, which was a significant decrease in Ba. Therefore, the same experiment was repeated with the average energy density per pulse of the energy beam irradiation portion on the target changed to about 1 J / cm ² .
In this case, although the vapor deposition rate was high at first and the composition was close to the desired composition, the grains on the thin film became more prominent and increased, and in the sixth batch, the vapor deposition rate was remarkably decreased and the thin film composition was Y: Ba :. The superconducting transition temperature was 81K, which was deviated from the target composition of Cu = 1: 1.5: 2.4. The generation of grains on the thin film became more prominent. In addition, several 100 μm-square coarse particles having a size of 1 μm or more were also mixed. Further, the surface of the target was remarkably rough, and irregularities were observed even with a 50 × optical microscope.

COMPARATIVE EXAMPLE 2 The same experiment as in Example 1 was manually stopped by rotating the target, and the YCu and BaCu targets were subjected to 10H at predetermined positions.
With z, laser irradiation for 7.5 minutes and 2.5 minutes respectively,
Other conditions were the same, and the vapor-deposited thin film was produced. At this time, when the obtained film was subjected to elemental analysis by a fluorescent X-ray apparatus, it was found that Y: Ba: Cu
A composition ratio of 1: 1.7: 3.0 provided a thin film with an estimated film thickness of about 500Å. At this time, Y: Ba: Cu = 1: 2: 3
The vapor-deposited atomic molecules have a converted average film thickness of 50Å during the cycle, and the maximum lattice spacing of the unit cell is about 1
Large enough compared to 1.7Å. This also corresponds to about 4 times the number of moles when one unit cell covers the substrate. The achieved cycle of the target composition is approximately 9 minutes. This thin film had almost the same thin film composition as that of the example, but did not show zero resistance, and was a thin film mainly composed of an impurity phase such as BaCuO _{2 in} X-ray diffraction.

Example 2 Preparation of YBa ₂ Cu ₃ O ₇ Thin Film The same experimental apparatus as in Example 1 was changed with the following points. 1) Use a lens with a focal length of 400 cm as the target 1
It was focused in front of cm. 2) Attach a light intensity attenuator (using a plate with a 1 mm diameter hole uniformly opened) on the servo motor that makes a hole on the aluminum plate so that light passes through only a part of the laser beam, and rotates the target holder. The light attenuator is rotated in synchronization with the laser irradiation energy so that the laser irradiation energy is Y only on the Ba target.
It was 1 of 5 minutes on the Cu ₃ target. 3) A stop equal to the size of the uniform area of the laser beam was placed in front of and behind the light attenuator.

Cu particles having a purity of 99.99% and a purity of 99.9
% Y particles were mixed at a molar ratio of 1: 3 and melted by an arc melting method in an argon gas to form a YCu ₃ alloy, which was used as a target with Ba. The above YCu ₃ , Ba, and YCu ₃ alloy targets were attached in this order every 103 degrees in the direction of rotation of the target holder, and the SrTiO ₃ single crystal substrate was placed 7.5 cm away from the target to face the target.
The substrate was fixed on the heater with silver paste and the vacuum chamber was evacuated. The substrate was heated to about 650 ° C., and the temperature was set to 3 × 10 ⁻⁶ torr or less. A mass flow meter (flowmeter) was used to fill the substrate with pure oxygen gas at 95 mtorr at a flow rate of 80 sccm. It was left for 20 minutes while being irradiated with. After turning off the ultraviolet light and closing the shutter for 1 minute to pre-sputter the target surface, vapor deposition was started.

The energy per pulse of the laser is 1
80 mJ, and constantly controlled to about 0.3 J / cm ² the average energy density on 1.5J / cm ^2, Ba target energy density on YCu ₃ target. Rotate the target holder at 300 rpm, YCu per rotation
₃ Target 1 per pulse, combining all YCu ₃ target when 2 pulses, Ba target cells per pulse laser irradiation was operated for 50 minutes. It was set so that the irradiation position of the target was shifted and scanned at a different angle for each target every 10 rotation cycles. At this time, the vapor-deposited atomic molecules of Y: Ba: Cu = 1: 2: 3 are supplied in about 200 milliseconds. After continuing for 50 minutes, the vacuum chamber was filled with pure oxygen at 1 torr or more and the substrate heating was immediately stopped, and the temperature was lowered to 200 ° C. or less in about 30 minutes.

The obtained thin film was quantitatively analyzed for the elements by a fluorescent X-ray apparatus which had been corrected by ICP analysis method (inductively coupled plasma emission analysis method) in advance, and the composition ratio of Y: Ba: Cu was 1: 2.2. At 3.3, a thin film with an estimated film thickness of about 500Å was obtained. At this time, the converted average film thickness of the atomic molecules during the period in which the vapor-deposited atomic molecules of Y: Ba: Cu = 1: 2: 3 is 0.03Å, and the minimum lattice spacing of the unit cell is about 3.8Å.
Which is sufficiently smaller than that of the unit cell, which corresponds to about 1/100 of the number of moles when one unit cell covers the substrate. Almost no grains could be seen under an optical microscope, and although SEM had precipitates scattered on the surface, grains having a size of 1 μm or more, which are characteristic of laser vapor deposition, were not seen. In X-ray analysis, YB
It was confirmed to be a C 2 -axis oriented film of a ₂ Cu ₃ O ₇ , and the superconducting transition temperature was 80K.

[0043]

[Effects of the Invention] The characteristics of the laser vapor deposition method, that is, the atmospheric gas species and its pressure can be freely selected, and activated atomic molecules can be supplied onto the substrate, remain free from the target thin film composition. Without selecting a target material from a wide range of materials, it is easy to select a target material whose target composition does not fluctuate or a target with which a dense target is easily manufactured, and composition control in a wide parameter range and suppression of grain generation are possible. To do. In particular, a good quality thin film can be formed without post heat treatment.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a laser vapor deposition apparatus.

FIG. 2 is a schematic view showing an example of a target used when a continuous wave electromagnetic wave beam is used in the vapor deposition method of the present invention.

FIG. 3 is a diagram showing an example of an electromagnetic wave beam irradiation method in the case of controlling the composition of a thin film to be formed by the number of irradiation pulse times of the electromagnetic wave beam in the sequential vapor deposition method of the present invention.

FIG. 4 is a diagram showing an example of an electromagnetic wave beam irradiation method in the case of controlling the composition of a thin film formed by the irradiation pulse energy density of the electromagnetic wave beam in the sequential vapor deposition method of the present invention.

[Explanation of symbols]

 1 Excimer laser generator 2 Optical box 3 Vacuum chamber 4 Condenser lens 5 Ultraviolet light transmitting window 6 Target 7 Target holder 8 Substrate 9 Substrate holder 10 Shutter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // H01B 12/06 ZAA 7244-5G

Claims (3)

[Claims] 1. A method for producing a crystal thin film of a compound containing two or more kinds of metal elements on a substrate, which comprises a plurality of compounds containing at least one kind of metal element constituting the compound and having different compositions from each other. When the target is sequentially irradiated with an electromagnetic wave beam at a constant cycle and atoms or molecules are supplied onto the substrate so that the metal composition is almost the same as the compound, a thin film is deposited during one supply cycle. A method for producing a crystal thin film, characterized in that the average number of moles of atoms or molecules attached to a substrate is less than the number of moles of one unit lattice of the compound crystal thin film. 2. The method for producing a crystalline thin film according to claim 1, wherein vapor deposition is performed in an active atmosphere gas containing a gas component in the ceramic thin film. 3. The atmospheric gas pressure is 0.1 to 1000 mto.
The method for producing a crystalline thin film according to claim 2, wherein the crystalline thin film is rr.