JPH0753634B2 - Oxide thin film manufacturing equipment - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an apparatus for producing an oxide thin film, and more specifically, an apparatus for producing various oxide thin films used for optical elements, piezoelectric elements, surface acoustic wave elements and the like. It is about.

[Technical background of the invention]

Conventionally, the best method for producing an oxide thin film is a sputtering method. As shown in FIG. 1, the sputtering apparatus generates a plasma by discharge between the electrode plates 1 and 2 facing each other, and causes ions to collide with the target 1 placed on one electrode plate 2, while the target 1 This is an apparatus for producing a thin film by depositing more sputtered atoms or molecules on a substrate 3 on an electrode plate 2 placed opposite to a target 1. At this time, a sputtering gas such as Ar is made to flow from the gas inlet 4 to the outlet 5.

Generally, a desired oxide is used as a target material, and an oxide thin film is formed by mixing O ₂ gas into Ar as a sputtering gas.

However, in the above-mentioned sputtering method, the control of the oxygen amount depends on the oxygen partial pressure, so that it is not possible to control the atomic level, and the reproducibility is not sufficient due to changes in the target composition ratio over time. There was a drawback. In fact, X
Even in oxide films that are recognized as single crystals by line diffraction and high-energy electron diffraction, experimental results have been reported that oxygen defects in the film have a large effect on the electrical properties of the film (Suzuki, Murakami, Soli.
d State Comun. 53, 1985, see P691).

In addition, such crystal defects including oxygen defects reduce the density of the film and cause deterioration of film characteristics such as a decrease in electric breakdown voltage.

In addition to the sputtering method, a device for obtaining an oxide film by incorporating an ion source 6 such as a Cowman type shown in FIG. 2 into a vapor deposition device and performing oxygen ion irradiation simultaneously with vapor deposition has been disclosed (for example, PJMartin. , J. Material Scienc
See e21 volume 1986). In this apparatus, an evaporation source 7 is provided in the lower part of the apparatus, and the evaporation source 7 is provided on a substrate 3 installed on an electrode plate 2.
In this case, oxygen ions are irradiated from the ion source 6 to produce an oxide film having no oxygen defects. In FIG. 2, 4 is a gas inlet, and 5 is an outlet.

In such an apparatus, since the operating gas pressure of the ion source 6 is 1 × 10 ⁻⁴ Torr or more, it is impossible to perform vapor deposition in a high vacuum of 1 × 10 ⁻⁵ Torr or less. Therefore, the vapor deposition molecules reach the substrate 3 while colliding with the residual gas many times, and the adsorption of the residual gas also occurs on the surface of the substrate 3, so that it is difficult to sufficiently control the composition of the vapor deposition film. Further, generally, ions such as O ⁺ , O ₂ ⁺ , and O ²⁺ and neutral radicals are randomly mixed in the irradiated oxygen ions, so that an accurate oxygen amount cannot be monitored. Therefore, the semiconductor Si
In principle, it has been impossible in the past to achieve composition control and impurity level control for oxide thin films, as has been achieved for GaAs and GaAs thin films.

[Outline of Invention]

It is an object of the present invention to provide an apparatus for producing an oxide thin film having good characteristics, that is, having no crystal defects and having a density close to a bulk value.

Another object of the present invention is to provide an apparatus for producing an oxide thin film having no composition deviation in the oxide thin film.

A further object of the present invention is to provide an oxide thin film device capable of excellent impurity level control.

Another object of the present invention is to provide an apparatus capable of producing a multi-layered oxide thin film which does not cause diffusion between the multi-layered oxide thin films when producing a multi-layered oxide thin film.

In order to achieve the above object, an oxide thin film manufacturing apparatus according to the present invention comprises a substrate holder for heating a substrate provided in a film forming chamber, and a molecular beam for evaporating a substance to be deposited on the substrate by a molecular beam. In a device for producing an oxide thin film having a vapor deposition source, an ion chamber for generating plasma and extracting oxygen ions with energy of 10 to 50 KeV from the plasma, and O ⁺ or O ₂ ⁺ from oxygen ions from this ion chamber. A mass separator for separating only ions, and a deceleration electrode for decelerating the oxygen ions to 10 to 200 eV,
The thin film deposited on the substrate under high vacuum can be irradiated with the decelerated oxygen ions simultaneously with vapor deposition.

According to the apparatus for producing an oxide thin film of the present invention, a thin film is deposited on a substrate by molecular beam vapor deposition having good composition controllability, and O ⁺ or O ₂ ⁺ is decelerated to 10 to 200 eV to form a deposited film on the substrate. Therefore, an oxide thin film without crystal defects can be produced in a high vacuum. Therefore, there is an advantage that the composition controllability is good and an oxide thin film having no crystal defects can be obtained. Further, since the oxide thin film is manufactured in a high vacuum, crystallization is started even when the substrate temperature is lowered, and when the oxide thin films are laminated in multiple layers, diffusion may occur between the oxide thin films. There is also the advantage of not having it.

[Specific Description of the Invention]

FIG. 3 is a schematic view of a specific example of the apparatus for producing an oxide thin film according to the present invention. As is clear from this figure, according to the apparatus for producing an oxide thin film according to the present invention, a raw material for an oxide thin film is obtained. A film forming chamber 11 equipped with K-cells 8 and 8'which are molecular beam sources for charging a thin film raw material to be vaporized by a molecular beam and an electron beam evaporation source 9 for vaporizing other thin film raw materials.
Is equipped with. And the ionization chamber 10 for extracting oxygen ions from the plasma source with energy of 10 to 50 KeV is
O ⁺ or O ₂ from oxygen ions generated in the ionization chamber 10
Mass separator 13 for separating ⁺ and this O ⁺ or O ₂ ⁺
Via the decelerating electrode 12 for decelerating the 200eV are connected to the film forming chamber 11, the substrate 3 on the substrate holder 2 O ⁺
Or it is designed so that oxygen ions of O ₂ ⁺ can be implanted.

A quartz oscillator or an ion gauge 14 and a mass spectrometer 15 for monitoring the intensity of the molecular beam are provided in the film forming chamber 11, and a Faraday cup 16 for monitoring the ions is provided. There is.

An electron emission source 17 such as a thermionic filament is provided between the deceleration electrode 12 and the substrate 3, and when an insulating film is formed on the substrate 3, ions or electrons are radiated onto the substrate 3 to be deposited. The film can be prevented from being charged.

The ionization chamber 10 is connected to the mass separator 13 via a gate valve 20. Note that reference numeral 19 is a sample introduction chamber.

The apparatus for manufacturing an oxide thin film according to the present invention operates as follows.

First, the film forming chamber 11 is set to a high vacuum (high vacuum of 10 ⁻⁵ Torr or more) by a cryopump or the like.

In the molecular beam vapor deposition for vapor-depositing elements other than oxygen, vapor deposition is performed on the substrate 3 from the K-cell vapor deposition sources 8 and 8'or the electron beam vapor deposition source 9 in the above-mentioned ultra-high vacuum (for example, 10 ^-9 Torr). I do. At this time, the intensity of the molecular beam source is monitored by the crystal oscillator or the ion gauge 14 and the mass spectrometer 15, and by feeding back this, the input power to each vapor deposition source can be controlled.

Oxygen ions generated in the ionization chamber 10 with energy of 10 to 50 KeV enter the mass separator 13 through the gate valve 20 and are separated into O ⁺ or O ₂ ⁺ . This O ⁺ or O ₂ ⁺ oxygen ion beam is decelerated by the deceleration electrode 12 to have an energy of 10 to 200 eV and is applied to the substrate 3. At this time, the oxygen ion beam is monitored by the Faraday cup 16 and fed back to control the energy. The irradiated oxygen ion beam has a high density of 10 to 100 μA / cm ² .

In oxygen ion irradiation, setting of oxygen ion energy is important. That is, when the ion energy is 10 KeV or more, crystal defects remain in the obtained thin film, the film thickness is significantly reduced by the sputtering effect in the range of more than 200 eV to 10 KeV, and the energy is too low at less than 10 eV,
It is necessary to raise the substrate temperature as in the ordinary vacuum deposition. Therefore, the oxygen ion energy is set to 10 to 200 eV.

Since the ionization chamber 10 has a low vacuum (10 ^-4 Torr), the differential pressure exhaust is performed by separating (for example, 1 m or more) the ion chamber 10 and the molecular beam deposition chamber (film forming chamber) 11 (10 ^-9 Torr). Has been done. At this time, the ions are inevitably long distance (1m or more)
The low-energy (10 to 200 eV) ions cause the beam diameter to spread due to the space charge effect. Therefore, high energy (10 to 50 Ke
V), and the low energy (1
The structure has a deceleration electrode 12 that decelerates to 0 to 200 eV). Therefore, high-density (10 to 100 μA / cm ² ) ion irradiation can be obtained.

Further, a mass separator 13 is provided between the ion extracting electrode 21 and the deceleration electrode 12 in order to obtain pure O ⁺ or O ₂ ⁺ ions.

As described above, the ultrahigh vacuum for forming the oxide thin film on the substrate 3 is preferably a high vacuum of 10 ⁻⁵ Torr or higher. 10 ^-5 To
When the vacuum is lower than rr, the crystal growth temperature rises,
This is because the substrate temperature must be kept high.

With such a configuration, compared to the conventional sputtering device and vapor deposition device in which an ion source is applied, it is possible to form a film in a high vacuum, and the epitaxial temperature of the single crystal film is lowered (600 ° C or less). In addition, there is an advantage that the composition of each element including oxygen can be controlled independently and accurately.

The present invention will be described below based on examples.

Example 1 [Manufacture of ZnO film] By using a microwave excitation type ion source as the ionization chamber 10 in FIG. 3, even if a highly reactive oxygen gas is used, the ion source can be continuously stored for 10 hours or more without any maintenance. It was possible to form a film. The vacuum degree of the ionization chamber 10 during operation is 5 × 10 ⁻⁴ Torr, and the film formation chamber 11 is evacuated between the ion source 10 and the mass separator 13 by a cryopump (displacement of 700 / sec). Was maintained at 5 × 10 ⁻⁹ Torr.

Here, the ions are extracted from the plasma chamber 10 at an extraction voltage of 20 KV, converted into O ⁺ through the mass spectrometer 13, and then the energy is reduced to 10 to 200 eV by the deceleration electrode 12. At this time, the value of the oxygen ion current density with respect to the energy after deceleration is shown in FIG. From Fig. 4, for example, a maximum of 50 μA / at an energy of 50 eV
An ion current density of cm ² is obtained.

Here, the Zn metal particles filled in the K-cell 8 in advance are evaporated, and the deposition rate on the substrate 3 is 0.73Å / sec.
By controlling the K-cell temperature so that the oxygen ion beam is irradiated onto the glass substrate under the conditions of 5 eV and 50 μA / cm ² at the same time, Zn and O that are incident per unit time per unit area are added. The stoichiometric ratio Zn: O
A ZnO polycrystalline film of = 1: 1 was obtained. In particular, use sapphire R or C surface as the substrate, and keep the substrate temperature from room temperature to 600
By maintaining a constant temperature between ℃, smooth surface
A ZnO single crystal film was obtained. The degree of vacuum in the film forming chamber 11 at the time of Zn evaporation was 5 × 10 ⁻⁸ Torr. At this time, the ZnO (1120) surface is on the sapphire R surface and the ZnO (00
01) surface has grown epitaxially. In both cases, the half-value widths of the (1120) and (0001) peaks were both smaller than 0.3 ° by X-ray diffraction measurement of the obtained ZnO film, and the ZnO lattice constant converted from the peak position was almost equal to the bulk value ( The difference is 0.1% or less), which indicates good crystallinity. Usually, in the sputtering method, the same degree of crystallinity cannot be obtained unless the substrate temperature is 600 ° C. or higher. Therefore, according to the oxide thin film manufacturing apparatus of the present invention, a single crystal film having good crystallinity at a low substrate temperature can be obtained. It was proved that it could be obtained.

Example 2 [Production of LiNbO ₃ film] In the same manner as in Example 1, after obtaining an O ⁺ ion beam under the conditions of 50 eV and 50 μA / cm ² , the thermionic emission filament 17 (neutralizing filament) is energized. A neutral oxygen beam was obtained by heating and applying a thermionic shower to the O ⁺ ion beam. Also, Li from the K-cell 8 and electron beam evaporation source 9
By evaporating Nb, sapphire C at the same time as the oxygen beam
By irradiating the surface substrate, a LiNbO ₃ single crystal film was obtained. Also oxygen ion beam in LiNbO ₃ film of insulator by neutralization, the refractive index n ₀ (normal light) having a wavelength of 633nm to light 2.32, ne (extraordinary light) is LiNbO ₃ film density close to the bulk at 2.18 Is obtained.

Example 3 [BaPbO ₃ -BaBiO ₃ multilayer film] Figure 3 of the K- cell 8 three prepared, Ba, respectively, Pb,
Bi metal particles were added, vapor deposition was performed, and oxygen ion irradiation was performed in the same manner as in Example 1 to form a multilayer film on the SrTiO ₃ (110) plane substrate 3. First, the shutter is used to prevent vapor deposition of only Bi, and a BaBiO ₃ film is formed to a thickness of 50Å,
A separate shutter prevents only Pb from being vapor-deposited.
An O ₃ film is formed with a thickness of 50Å. This process was repeated 50 times to form a BaPbO ₃ —BaBiO ₃ multilayer film having a thickness of 5000Å. At this time, even if the substrate temperature is as low as 300 ° C, a single crystal film is formed, and at that time, there is no mutual diffusion of each layer of BaPbO ₃ and BaBiO ₃ and the superlattice film structure that is steep on the atomic order is adopted. It was confirmed by microscopic observation.

〔The invention's effect〕

As described above, according to the oxide thin film manufacturing apparatus of the present invention, an oxide single crystal thin film having a density close to the bulk value has sufficient composition control and a low substrate temperature (from room temperature to 60 ° C.).
Can be formed at 0 ° C. Therefore, there is an advantage that the multi-layered structure of oxides can be formed as designed without mutual diffusion, and a thin film which could not be produced by conventional mutual diffusion can be formed.

[Brief description of drawings]

FIG. 1 is a block diagram of a sputtering apparatus, FIG. 2 is a block diagram of a vapor deposition apparatus incorporating an ion source such as a Cowman type, and FIG. 3 is a block diagram of one embodiment of an oxide thin film manufacturing apparatus according to the present invention.
FIG. 4 is a diagram showing the maximum oxygen ion current density characteristics with respect to oxygen ion energy in the apparatus of the above-mentioned embodiment. 1 ... Target, 2 ... Substrate holder, 3 ... Substrate, 4
…… Gas inlet, 5 …… Gas outlet, 6 …… Ion source,
7 ... Evaporation source, 8, 8 '... Knud cell (K-cell), 9 ... Electron beam evaporation source, 10 ... Ionization chamber, 11
…… Deposition chamber, 12 …… Deceleration electrode, 13 …… Mass separator, 14 ・ ・ ・
… Thickness gauge or ion gauge, 15 …… Mass spectrometer, 16…
Faraday cup, 17 Neutralizing filament, 18 ...
... Heater for heating substrate, 19 ... Sample introduction chamber, 20 ... Gate valve,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C30B 29/22 Z 8216-4G 29/30 A 8216-4G

Claims (5)

[Claims] 1. An apparatus for producing an oxide thin film, comprising: a substrate holder for heating a substrate provided in a film forming chamber; and a molecular beam evaporation source for evaporating a substance to be deposited on the substrate by a molecular beam. O ⁺ from the ionization chamber to generate and extract oxygen ions from the plasma with energy of 10 to 50 KeV and from the oxygen ions from this ionization chamber
Or a mass separator for separating only O ₂ ⁺ ions,
With a deceleration electrode for decelerating the oxygen ions to 10 to 200 eV, the thin film deposited on the substrate under high vacuum can be irradiated with the decelerated oxygen ions simultaneously with vapor deposition. Oxide thin film manufacturing apparatus. 2. The oxidation according to claim 1, wherein the number of the molecular beam vapor deposition sources is one or more, and the vapor deposition sources can perform vapor deposition independently of each other. Thin film manufacturing equipment. 3. A Faraday cup, a crystal oscillator, or an ion gauge is provided in the film forming chamber, and the oxygen ion irradiation amount and the molecular beam irradiation amount can be monitored and feedback-controlled, respectively. An apparatus for producing an oxide thin film according to claim 1 or 2. 4. The film forming chamber is provided with an electron irradiation mechanism between the ionization chamber and the substrate so that the oxygen ion beam or the substrate can be irradiated with electrons. 4. An apparatus for producing an oxide thin film according to any one of items 3 to 3. 5. The film forming chamber is formed by irradiation with a neutral oxygen beam.
The apparatus for manufacturing an oxide thin film according to claim 4, further comprising a mechanism for measuring the amount of secondary electron emission.