JPH03274257A - Method and apparatus for producing thin oxide film - Google Patents

Abstract

PURPOSE:To form a multiple oxide of single crystal minimal in defects at low temp. by using plural simple oxides as targets, alternately or simultaneously sputtering these targets by means of ion beam, and supplying active carbon, if necessary. CONSTITUTION:Plural simple oxide targets 1 are held by a target holder 2 having a conical curved surface. Sputtering is carried out by changing the direction of ion beam into an arbitrary direction by means of an impressed voltage on a deflecting device 7 and switching the targets 1. Further, ion beam irradiation is carried out by switching the targets 1 by means of control electric power source 8. Moreover, irradiation time is selected. Simultaneously, active carbon is supplied from an active carbon source 10 onto a substrate 3, if necessary. By this method, the thin single-crystal film having a composition corresponding to stoichiometric ratio and also having superior quality can be produced. The necessity of particularly high degree, of vacuum, complicated evaporation mechanism for multicomponent, and high-degree control can be obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus and method for manufacturing composite oxide thin films used in dielectric optical elements, piezoelectric elements, surface acoustic wave elements, superconducting elements, etc.

[Conventional technology] MA has a chemical composition consisting of multiple metal elements MA, Ml.
nAMana...0. A sputtering method is often used to form a composite oxide expressed as a thin film crystal on a substrate. In this method, a composite oxide thin film is formed by targeting an oxide sintered body with a desired composition and sputtering it onto a substrate using plasma or an ion beam, but the composition of the thin film deposited on the substrate is There was a problem that the composition did not match the target composition.

In order to solve this problem, in recent years, multidimensional vacuum evaporation methods have been used to form fffi-type oxide superconductors and magnetic materials with high critical temperatures. For example, JP-A-1-21
Publication No. 9162, Japan Society of Applied Physics Lecture Proceedings No. 2a-
E-7, JP-A-59-184799, etc.

As shown in FIGS. 4 and 5, this method involves depositing a single metal, which is a refined element, on a substrate by evaporating it in a vacuum using heater heating or electron beam heating.
Oxygen is supplied to form a composite oxide. These methods have the following problems.

[Problem B to be Solved by the Invention] Firstly, the apparatus used to form a film of a multi-component substance has become complicated and requires complicated control. That is,
The amount of molecular beam flux must be measured for each component element, and the amount of heat input to the evaporation source must be controlled.Also, the evaporation chamber must be kept at a high vacuum, while the area around the substrate must be maintained at a sufficient oxygen pressure to promote oxidation. , a device for supplying active enzyme is required.

Second, many useful oxide crystals contain metals that are easily oxidized at the evaporation temperature or metals that are rare as a single substance.For example, the former include alkali metals such as Li and carbon. , alkaline earth metals such as Ca, and the latter include rare earth metals such as Nd, Ho, and Er.

Evaporating such metals under conditions of controlling oxygen partial pressure or supplying active oxygen generally requires advanced technology.

There is also the problem of increased costs due to low yield.

Thirdly, it may be difficult to form an oxide containing elements having significantly different melting points as component elements. The kinetic energy of the evaporated particles depends on the temperature of the evaporation source, e.g. L + Ta
In O3, when the melting points of Li and Ta are significantly different, 180° C. and 2988° C., respectively, the energies of the evaporated particles are 0.04 eV and 0.28 eV. It is difficult to form a thin film with a good compositional structure of both components by depositing particles with different energies as described above, simply by controlling the amount of evaporated molecules.

Fourth, in order to use oxide crystals as optical waveguide devices, semiconductor devices, light emitting devices, and superconducting devices, trace amounts of active metal elements are often doped into the host crystal with precision. In multi-component deposition methods such as
Doping with quantitative elements is extremely difficult.

Therefore, the present invention does not use metals that have a strong tendency to oxidize at the evaporation temperature, or metals that are rare or expensive in terms of resources, as an evaporation source, and also provides an apparatus that includes an evaporator, oxygen supply mechanism, or complex control thereof. An object of the present invention is to provide an apparatus and a method for forming a single-crystal composite oxide with few defects at as low a temperature as possible while controlling the stoichiometric ratio and weight-adding elements without using.

[Means for Solving the Problems] That is, the present invention provides an ion beam sputtering thin film forming apparatus for forming an oxide thin film containing a plurality of metal elements as components, comprising: (a) rotation for rotating a substrate; (b) A substrate holding mechanism comprising a heating chamber and a heater for maintaining the temperature at a predetermined temperature. (b) A substrate holding mechanism that holds a simple oxide target of each component element of the composite oxide thin film and that is capable of holding simple oxide targets for each of the component elements of the composite oxide thin film and for releasing the target from the target by sputtering. (e) a variable energy ion source for sputtering, and a sputtering ion beam emitted from the ion source; (d) Beam deflection device for switching the incident angle to multiple targets at an incident angle that maximizes the rate of incidence; The present invention relates to an oxide thin film production apparatus characterized by comprising: active oxygen sources disposed opposite to each other; and (e) a computer for automatically switching and controlling a beam deflection device according to a predetermined program.

Furthermore, the present invention provides a method for manufacturing an oxide thin film using the above-mentioned apparatus, in which individual targets of simple oxides of constituent elements of a desired composite oxide N film are sputtered onto a substrate according to a predetermined program. The present invention relates to a method for producing an oxide thin film, characterized in that a surface reaction is promoted by simultaneously supplying active oxygen around the substrate.

[Function] The device according to the present invention has the following essential mechanisms: ■ Stable simple oxides of constituent metal elements MA, AOo, M
A device 111 (target holder) that targets a plate-shaped sample of S ++ @ OY I... and holds the target so that the particles emitted by sputtering can efficiently irradiate the substrate; ■ Energy for sputtering An ion source that supplies a variable ion beam, a deflection device (steerer) that switches and irradiates the ion beam to multiple targets, and there is at least one set of this ion source and deflector system, and there may be multiple sets: ■ A substrate holding device that supports and rotates the substrate; and a heating device that maintains the substrate at a predetermined temperature; (2) A source of active oxygen to promote the reaction of simple oxide molecular beams and reduce oxygen vacancies.

In the present invention, a plurality of simple oxides are targeted by measuring the sputtering yield and the rate at which the emitted molecular beams are deposited on the substrate in a vacuum of 10-') or less, and these are then exposed to the ion beam. This method is characterized by forming a crystalline thin film at a lower temperature than conventional methods by sputtering alternately or simultaneously in a time-sharing manner and supplying active oxygen if necessary.

[Example of implementation] The present invention will be further explained below with reference to Examples.

Example 1 The basic configuration of the apparatus of the present invention will be explained below with reference to FIG. 1 showing one embodiment of the present invention.

(1), (1'>-= ・ is M A M A O, A,
Simple oxide targets such as MaxaOya. These are target holders (
2) is fixed on the inner surface.

(3) is a substrate on which a thin film of composite oxide is formed, the center of which is located in the direction of the normal to the center of the target surface so that the amount of molecular beams emitted from each target is maximized.

(4) is a substrate holding device, which is rotated by a motor (5>). <4') is an electric heater for adjusting the temperature of the substrate.

(6) is a small diameter ion source for sputtering,
Its accelerating voltage can be varied from 1 to 20 KV.

(7) is a deflection device, and the direction of the ion beam can be changed to any direction by applying a voltage to the deflection device (7).
Sputtering can be performed by switching to other methods.

The apex angle θ of the target holder (2) and the deflection device are adjusted so that the incident angle of the ion beam that is normal to the target laser I is close to 60", which maximizes the sputtering yield. The distance between (7) and the target (2) is determined.

The target is switched and irradiated with the ion beam by a controll power source (8) of the deflection device. The stoichiometric ratio of the component elements MA, M, ... of the target composite oxide thin film is set to nA, na ... target (1), (1
')...'s sputtering yield as SA, S,...
・Then, the time to irradiate each target with the ion beam 6, t, ... ratio is t^:tB...=SAn
The irradiation time is selected so that A:S, 118..., and is automatically switched by the computer (9>).

(10) is an active oxygen source for irradiating the substrate, which is placed in the normal direction to the center of the substrate, that is, facing the substrate. The vacuum chamber (13) is connected to an exhaust system to maintain the pressure at 101 Torr or less prior to the film forming operation and at 10-' Torr or less during the film forming operation.

Irradiation time tA to the substrate using the apparatus shown in Figure 1
, tl..., it is possible to efficiently produce a thin film crystal of a composite oxide having a stoichiometric ratio and few defects with good reproducibility.

In addition, in Example 2 below, a preferable example of the device of the present invention will be described.
An oxide thin film manufacturing apparatus shown in FIG. 2 showing an embodiment was used.

Next, the apparatus shown in FIG. 2 will be explained.

The device shown in FIG. 2 is the main part of the device of the present invention shown in FIG. 1 with various additional functions added.

A vacuum Wi (143) equipped with a target (1) which is a thin film material, a substrate (3) on which a composite oxide thin film is to be formed, etc. is connected to a cryopump (26) via a gate valve (25), and is connected to a cryopump (26) for film formation. The structure is such that the inside of the system can be maintained at a predetermined degree of vacuum during operation.

An ion source that generates an ion beam for sputtering (
6) is a conventional ion source consisting of an ion source power supply (4) and an Ar cylinder (23). The ion beam for sputtering is an Einzel lens (15).

The target is irradiated via (15') and deflectors (7) and (7'). The Einzel lens is an n-electron Q lens that acts to adjust the cross-sectional distribution of the ion beam. In addition, the deflection device is equipped with a cleaning device power source (8) and a computer (9), and if the irradiation time of the ion beam for sputtering to each target is programmed into the computer, the ion beam will be applied to each target for the programmed set time. It has a configuration that allows ion beam irradiation.In other words, the computer (9) calculates the stoichiometric ratio of the component elements MA, M, ... of the target N film of the composite oxide by nA, nl・', and the target. (1), (1
If the sputtering yield of ') is SA, S,..., then the time tA- for irradiating each target with the ion beam is
The ratio of tl・” is tA: ti・HH=SAnA:San
, . . . The irradiation time is selected and automatically switched as follows.

A filament (24) and a Faraday cup (19) are disposed between the deflection devices (7), (7') and the target (1).
is provided. A filament (24) is provided to supply hot electrons to neutralize the charge of the ions. The Faraday cup (19) serves for ion beam current measurement.

In addition, the active oxygen source is equipped with an ECR ion source (17), an ECR ion source power source (18), and an oxygen cylinder (11), and is also structured to be able to apply microwaves. It acts to efficiently generate ions.

Note that the target holder (2), substrate support mechanism (4), etc. of the apparatus shown in FIG. 2 have substantially the same configuration as those of the apparatus shown in FIG.

In the apparatus shown in Fig. 2, a reflective high-energy electron beam diffraction device consisting of an electron gun (20), a fluorescent screen (21), and a camera <22> is installed, and the structure of the thin film obtained after film formation is can be measured.

Further, in Examples 2 and 3 below, an oxide thin film production apparatus shown in FIG. 2 was used as a preferred embodiment of the apparatus of the present invention.

Example 2 When manufacturing a composite oxide thin film having the above-mentioned structure, the thin film thickness of 1% of this example was used. performed the operation.

Using powders of Li2O, Nb, and O9 as raw materials, this was flit hydraulically formed at a pressure of 5000 kg/cl.
Flat plates sintered at temperatures of 1000°C and 1500°C, respectively, were used as targets (1) and (1').

Further, Y-cut LiNb◯ single crystal was used for the substrate (3).

Appetizers @ Directly & Akira Flftm\r, x-mu, and M
d4KtUE IA5r”KV was used. Also, a tungsden filament (24) was used for ionic charge neutralization.
is provided.

As the active oxygen source, an ECR ion source (17) with an effective diameter of 20 mm was used, with an extraction voltage of 300 V and a current density of 0.
Oxygen ions of 5 mA/am'' were irradiated.

Also, as a microwave, 2.45GH2, input 10
A 0W one was used. At a substrate temperature of 450"C and a rotation speed of 50 rpm, Li 20 and Nb2O9 targets were irradiated with an ion beam for 1ffl+ for 3 and 4 seconds.
By sputtering for 2 hours alternately at intervals of 4
'fiIIIi of μm was obtained on the substrate.

When the structure of the thin film obtained after film formation was examined using a reflective layer high-energy electron beam diffraction apparatus installed in the apparatus shown in FIG. 2, it was confirmed that the obtained thin film was a single crystal.

Moreover, according to chemical analysis by ICP method, Li/Nb=
It was found to be 1.00.

Next, in addition to the above LLO and Nb2O5, a T i O2 target is added as a target, and when I? ff11
? LiNbO3 doped with about 0.8% titanium by sputtering at 50 microsecond intervals
A dedicated optical path and wave path was created.

Example 3 Nd-doped Y) A 1 s O+ for solid-state laser
2 (Y A G ) single crystal is L i N bo
Similar to 3, crystals produced by the Czochralski method are commercially available. YAG has problems such as a high melting point of 1970° C., a very slow crystal growth rate of 0.1 grains/hour, and a low yield of laser rods due to core defects.

By the method of the present invention (111 planes), a YAG optical waveguide was formed on a single YAG single root substrate. Al as a raw material
! 5 using powders of 202, Y 203 and Nd2O5.
Flat plates that were hydrostatically formed at a pressure of 000 kg/c+e' and sintered at 1400°C, 1600°C, and 1600°C, respectively, were used as targets. The conditions for the sputtering ion beam and the substrate irradiation active oxygen are the same as in Example 2.

Ion beam irradiation time for sputtering is A 1203
A single crystal thin film with a thickness of about 2 μm was obtained by continuously forming the bottom film for 2 hours under conditions of 3 seconds, Y, 0.5 seconds, and N d20 s 80 microseconds. Nd doping amount is 0.9 at% by EPMA
Met.

Comparative Example Conventionally, single crystals of 1Nbo3 used in electronic devices such as surface wave devices and optoelectronic devices such as optical modulators have often been produced by a rotational pulling method from a melt using the Czochralski method.

That is, raw material powder of LiNb○ is melted by high-frequency heating using a platinum crucible, and while keeping the temperature at 1270°C, it is heated using seed crystals at a rotation speed of 20 rpm and a speed of 3 var.
Pull up at the speed of @/hour. In this method, as shown in the phase diagram in Figure 3, the crystal crystallized from the liquid phase of the stoichiometric set rL (Li/Nb=1) separates into two phases, so the single crystal is
It is grown from a liquid phase with a harmonic melt composition of i/Nb=0.98. Therefore, only crystals containing many defects at the Nb and 0 positions can be obtained. There is Fl'if1, which can be used for electronic devices, but its quality is not sufficient for optoelectronic devices, and problems such as damage by laser light have been pointed out.

In addition, as a thin film forming method, LiNb0. We also conducted research on surface devices by sputtering using a sintered body of , but as mentioned above, it was difficult to control the stoichiometric composition.

[Effects of the Invention] According to the apparatus and method of the present invention, a high-quality single crystal thin film whose composition matches the stoichiometric ratio can be produced without using unstable or rare metals as evaporation sources.

The equipment for this purpose does not require a particularly high degree of vacuum, a complicated evaporation machine for multiple elements, or sophisticated control.

Furthermore, by changing the time settings for alternate sputtering of multi-element targets, it is possible to simultaneously dope a trace amount of active elements into the four-body crystal.

Further, it is also possible to form a multilayer film in which oxides having different constituent elements are laminated at regular intervals of the WA thickness, or a gradient mechanism film in which the composition changes continuously.

The apparatus and method of the present invention are effective for forming thin films of composite oxides containing metal elements with greatly different melting points, or composite oxides whose composition deviates from the stoichiometric ratio when grown from a melt.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the basic configuration of the device of the present invention, FIG. 2 is a diagram showing a preferred embodiment of the device of the present invention used in Examples, and FIG. 3 is a diagram illustrating the basic configuration of the device of the present invention.
This is an equilibrium state diagram of the C03 system, and FIGS. 4 and 5 are diagrams showing an apparatus used for forming a conventional multi-oxide-containing thin film by a reactive multi-component vapor deposition method. In the figure, 1.1'...Target, 2...Target holder, 3...Substrate, 4...Substrate support mechanism, 4'...
・Heater, 5...Motor, 6...Ion source, 7.7
'... Deflection device, 8... Deflection device power supply, 9... Computer, 10... Active oxygen source, 11... Oxygen cylinder, 12... Exhaust port, 13... Vacuum chamber, 14...
・Ion source power supply, 15.15'...Einzel lens, 16...Lens power supply, 17...ECR ion source, 18...ECR ion source power source 9...Faraday cup, 20. ...Electron gun, 21...Fluorescent screen, 22...Camera, 23...Ar cylinder, 24.
...Filament, 25...Gate valve, 26...
・Cryopump. Figure 3 Figure 4 Procedural amendment written on November 8, 2016

Claims (2)

[Claims] 1. An ion beam sputtering thin film forming apparatus for forming an oxide thin film containing a plurality of metal elements as components, the apparatus comprising: (a) a heater having a rotation mechanism for rotating the substrate and maintaining it at a predetermined temperature; (b) Holds the simple oxide target of each component element of the composite oxide thin film, and holds the target so that the molecular beam emitted from the target by sputtering most efficiently enters the substrate. a target holder having a conically curved surface for holding; (c) a variable energy ion source for sputtering;
a beam deflection device for switching the ion beam emitted from the ion source to a plurality of targets at an incident angle that maximizes the sputtering rate; (d) promoting surface reactions on the substrate and reducing oxygen defects; and (e) a computer for automatically switching and controlling the beam deflection device according to a predetermined program. Equipment for manufacturing oxide thin films. 2. 2. A method for producing an oxide thin film using the apparatus according to claim 1, in which individual targets of simple oxides of constituent elements of a desired composite oxide thin film are sputtered onto a substrate according to a predetermined program, and if necessary, sputtering is performed simultaneously. A method for producing an oxide thin film, characterized in that surface reactions are promoted by supplying active oxygen around a substrate.