JP5360799B2 - Method for producing zinc oxide thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cleaning an oxide substrate by removing both organic substances and metal impurities on its surface, and to provide a method of forming an oxide thin film on the cleaned oxide substrate. <P>SOLUTION: The method of cleaning an oxide substrate includes: a first cleaning step wherein at least either atomic hydrogen or atomic heavy hydrogen is brought into contact with the surface of an oxide substrate 5 without heating the oxide substrate 5 placed in a vacuum atmosphere, so as to remove metal impurities from the surface of the oxide substrate 5; and a second cleaning step wherein oxygen plasma is brought into contact with the surface of the oxide substrate 5 so as to remove organic impurities from the surface thereof. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for cleaning the surface of an oxide substrate and a method for manufacturing an oxide thin film, and particularly to a technique suitable for cleaning the surface of a single crystal zinc oxide substrate.

An Al ₂ O ₃ (sapphire) substrate has been used for crystal growth of a zinc oxide based semiconductor crystal, but since the lattice constant of a sapphire substrate is significantly different from that of a zinc oxide based semiconductor, a zinc oxide based semiconductor is formed on the sapphire substrate. When a crystal is grown, a large number of crystal defects are generated due to the difference in the lattice constant, which makes it difficult to apply to a device.
In recent years, single crystal zinc oxide substrates have been realized, and application to crystal growth of zinc oxide based semiconductors has begun to be expected. Crystal growth of a zinc oxide-based semiconductor using a single crystal zinc oxide substrate can reduce crystal defects caused by a difference in lattice constant as in the case of using a sapphire substrate. However, current single crystal zinc oxide substrates have problems with surface cleanliness and flatness, and are difficult to apply to semiconductor crystal growth.

  Usually, the substrate surface used for semiconductor crystal growth is cleaned using various methods to remove contamination existing on the surface. If the substrate surface is contaminated, the semiconductor crystal grown on the substrate will generate crystal defects due to the contamination. Further, the contamination of the substrate surface has a problem that it is taken into the crystal and becomes an impurity. Such crystal defects and impurities inside the semiconductor crystal deteriorate the crystallinity and electrical characteristics of the semiconductor crystal.

  The flatness of the semiconductor crystal is also important. A light emitting diode (LED) or a laser diode (LD) has a laminated structure sandwiching a very thin thin film on the order of several atomic layers called a quantum well structure. For this reason, the thin film to be applied needs to obtain flatness in the atomic layer order. If the substrate surface has a rough shape, the semiconductor crystal grown on the substrate takes over the surface shape of the substrate and becomes a rough surface.

For the above reasons, in order to realize a semiconductor element using a single crystal oxide substrate such as single crystal zinc oxide, it is necessary to suppress crystal defects and impurities as much as possible. That is, it can be recognized that the cleanliness and flatness of the substrate surface used for semiconductor crystal growth are extremely important features.
As an approach regarding these, as disclosed in Non-Patent Document 1 below, the surface of the single crystal zinc oxide substrate is planarized by a method of heat-treating the single crystal zinc oxide substrate in a ceramic zinc oxide box. .
In the technique disclosed in Non-Patent Document 2, the single crystal zinc oxide substrate is cleaned using hydrogen plasma. At present, gallium arsenide (GaAs) substrates used as light-emitting elements and electronic devices have been subjected to atomic hydrogen irradiation treatment as a cleaning method. Patent Documents 1 and 2 disclose a method of removing surface oxides and carbides by performing atomic hydrogen treatment.
The cleaning method disclosed in Patent Document 1 includes a radical processing step and a cleaning processing step as the cleaning processing step. After the substrate is introduced into the vacuum chamber, heating is performed to obtain a predetermined temperature (200 ° C. ), A radical treatment is performed, and then the temperature is raised to a high temperature (400 ° C.) and heat treatment is performed. However, Patent Document 1 does not describe substrate processing before introduction of the vacuum chamber and crystal growth after cleaning.
Although not described in Non-Patent Document 2, it is considered that hydrogen plasma treatment aims at the effects as described in Patent Documents 1 and 2.
Japanese Journal of Applied Physics, Vol. 45, No. 7, 2006, pp. 5724-5727 APPLIED PHYSICS LETTERS, Vol. 86, 091901 (2005) JP-A-6-97139 JP-A-10-79364

Conventionally, a substrate for semiconductor crystal growth has been degreased and cleaned before the crystal growth to remove organic substances adhering to the surface. When crystal growth is performed in a state where organic substances remain on the substrate, defects are generated in the semiconductor crystal using the impurities as nuclei, and the quality of the semiconductor crystal is degraded.
Usually, degreasing cleaning removes organic substances on the surface of the substrate with a solvent such as acetone or methanol. However, if the cleaning process or drying process is insufficient, the organic substances remain and the substrate for crystal growth is removed. There is a risk of contamination.
Ashing with oxygen plasma is considered to be effective for removing organic substances. However, since metal impurities other than organic substances are usually present on the surface of the semiconductor crystal growth substrate, organic substances are removed with oxygen plasma. As a result, oxides of remaining metal impurities are formed. Since this metal oxide is very stable both chemically and physically, there is a problem that it is extremely difficult to remove it once it is formed on the substrate surface.

In order to solve the above problems, an object of the present invention is to provide a method for cleaning an oxide substrate that can suppress the incorporation of impurities and the deterioration of surface flatness.
It is another object of the present invention to provide a method for forming an oxide thin film on an oxide substrate that has been cleaned by removing both organic substances and metal impurities on the surface.

In the method for producing a zinc oxide thin film of the present invention, at least one of atomic hydrogen and atomic deuterium is brought into contact with the surface of the zinc oxide substrate placed in a true vacuum atmosphere without heating. A first cleaning step for removing metal impurities from the surface of the substrate; and a second cleaning step for removing organic impurities from the surface of the zinc oxide substrate by bringing oxygen plasma into contact with the surface of the zinc oxide substrate. A step of cleaning the surface of the zinc oxide substrate by a cleaning method of the zinc oxide substrate provided; and a step of growing a crystal of zinc oxide on the surface of the cleaned zinc oxide substrate to obtain a single crystal zinc oxide thin film. It is characterized by that.
In the manufacturing method, the cleaning treatment is preferably performed in a high vacuum of 1.0 × 10 ⁻⁵ Torr or less.
In the manufacturing method, it is preferable that the substrate temperature during the first cleaning process is 100 ° C. or less.

According to the oxide substrate cleaning method of the present invention, a clean and highly flat oxide substrate surface can be obtained.
In addition, the manufacturing process can be simplified because the substrate does not require high-temperature treatment after heating or cleaning.
The present invention is particularly suitable for surface cleaning of a single crystal zinc oxide substrate, and by growing a thin film such as a zinc oxide based semiconductor crystal on the cleaned surface obtained by the present invention, the surface flatness of the monoatomic layer order is obtained. It is possible to obtain a semiconductor crystal thin film with good properties.

In addition, by crystal growth using a single crystal zinc oxide substrate cleaned according to the present invention, a zinc oxide thin film having extremely high surface flatness necessary for a quantum well structure, for example, a zinc oxide semiconductor thin film is obtained. It becomes possible to provide.
The present invention removes metal impurities on the surface of the oxide substrate by performing atomic hydrogen treatment at a low temperature without heating, and then forms an oxide plasma by performing oxygen plasma irradiation, Removal of organic impurities can be realized, the surface of the oxide substrate can be cleaned, and an oxide substrate having a flat and clean surface state can be obtained.
According to the present invention, there is no need for heating at the time of cleaning inside the vacuum chamber, and there is no need for a cleaning process at a high temperature as shown in Patent Document 1 described above. In addition, it is possible to remove residual organic impurities that have not been removed by degreasing and to contaminate the substrate having a clean surface obtained in the present invention as much as possible due to the cleaning process in ultra-high vacuum. It is possible to shift to the crystal growth process without any problem.
In addition, by growing crystals using a single crystal zinc oxide substrate cleaned according to the present invention, a zinc oxide system having extremely high surface flatness required for quantum well structures provided in light emitting diodes, laser diodes, etc. A semiconductor thin film can be provided.

  The present invention relates to crystal growth of a semiconductor crystal using an oxide substrate in a semiconductor manufacturing process represented by a molecular beam epitaxy (MBE) method, and relates to atomic hydrogen irradiation without heating the oxide substrate before growth. Provided is a cleaning method comprising a first cleaning process for removing metal impurities and a second cleaning process for removing organic substances by an oxygen plasma irradiation process, and a flat and clean oxide substrate surface is provided. It is characterized by obtaining.

  The present invention includes a step of degreasing an oxide substrate before crystal growth, a step of introducing the oxide substrate into a vacuum chamber and performing a cleaning process in a vacuum, and a step of performing crystal growth thereafter. TECHNICAL FIELD The present invention relates to an oxide thin film forming technique, and in a cleaning process after introducing an oxide substrate into a vacuum chamber, metal impurities on the surface of the oxide substrate are obtained by performing atomic hydrogen treatment at a low temperature. After that, it is possible to realize removal of organic impurities without forming metal oxide by performing oxygen plasma irradiation, thereby realizing surface cleaning of the oxide substrate, flat and clean It is possible to obtain an oxide substrate having a surface.

Hereinafter, an example of a method for cleaning an oxide substrate according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described below.
FIG. 1 is a block diagram showing an example of a processing apparatus suitable for carrying out the oxide substrate cleaning method of the present invention. In the processing apparatus of this example, the oxide substrate 5 to be cleaned is disposed at a predetermined position, and the inside is connected to a vacuum chamber 4 that can be evacuated to an ultra-high vacuum atmosphere, and an internal space of the vacuum chamber 4. A hydrogen supply cell 6 for supplying atomic hydrogen or atomic deuterium attached to the outer wall, a hydrogen source 3 and a filament heating power source 7 connected to the outside of the hydrogen supply cell 6, and the vacuum An oxygen plasma supply cell 11 connected to the inner space of the chamber 4 and attached to the outer wall thereof, and an oxygen source 8 and an RF power source 10 connected to the outside of the oxygen plasma supply cell 11 are configured. ing.

In the atomic hydrogen supply cell 6, a filament 1 for generating atomic hydrogen or atomic deuterium electrically connected to a filament heating power source 7 is provided. The hydrogen source 3 and the hydrogen supply cell 6 are connected by a hydrogen supply pipe 3a, and a valve 2 for adjusting the amount of hydrogen supplied to the atomic hydrogen supply cell 6 is provided in the middle of the hydrogen supply pipe 3a. ing. Further, the oxygen source 8 and the oxygen plasma supply cell 11 are connected by an oxygen supply pipe 8a, and a valve 9 for adjusting the oxygen supply amount to the oxygen plasma supply cell 11 is provided in the middle of the oxygen supply pipe 8a. Is provided.
The oxide substrate 5 is attached to the base 4A inside the vacuum chamber 4, and the hydrogen supply cell 6 and oxygen are disposed on the outer wall of the vacuum chamber 4 so as to face the surface of the oxide substrate 5 from an oblique direction. A plasma supply cell 11 is attached.

Next, a method for cleaning the oxide substrate 5 using the apparatus shown in FIG. 1 will be described.
Before the oxide substrate 5 is cleaned using the apparatus shown in FIG. 1, the oxide substrate 5 is degreased and preliminarily cleaned. The degreasing treatment performed here may be a degreasing treatment that is generally performed when cleaning the substrate, and an organic substance that is assumed to be attached to the surface of the oxide substrate 5 using a solvent such as acetone or methanol. Wash. When these solvents are used, various commonly used methods such as an immersion method, a spray method, a wiping method, and a steam method can be appropriately selected and used. After cleaning the outer surface of the oxide substrate 5 with these solvents, it is preferable to completely remove the solvent by a cleaning process and a drying process.

The oxide substrate 5 that has been degreased is introduced into the vacuum chamber 4 and set on the base 4A, and the inside of the chamber 4 is brought into a vacuum state of 1 × 10 ⁻⁵ Torr or less.
Thereafter, hydrogen gas is introduced from the hydrogen source 3 into the vacuum chamber 4, and the valve 2 is adjusted to set the hydrogen gas partial pressure to 1.0 × 10 ⁻⁵ Torr to 1.0 × 10 ⁻⁷ Torr. After the gas pressure is stabilized, the filament heating power source 7 is adjusted to energize the filament 1 and the filament temperature is heated to about 1900 to 2200 ° C. Since the hydrogen molecules touching the high temperature filament 1 are dissociated into hydrogen atoms and irradiated from the hydrogen supply cell 6 for supplying atomic hydrogen to the surface of the oxide substrate 5, the first cleaning process is performed.
In the first cleaning step, the oxide substrate 5 to be cleaned is not heated. Here, by not heating the substrate, it is possible to prevent diffusion of impurities into the inside and reduction of the substrate surface.
Not heating the substrate means that the substrate is not actively heated by a heating device or the like. However, the concept that the oxide substrate 5 naturally reaches a temperature of about 100 ° C. or lower according to the processing of the film is not heated.
Further, since the above-described atomic hydrogen irradiation treatment is performed in a high vacuum of 1.0 × 10 ⁻⁵ Torr or less, adhesion of impurities to the oxide substrate 5 can be minimized, The metal impurities on the surface of the oxide substrate 5 can be removed while preventing the diffusion of impurities into the interior and preventing the reduction of the substrate surface while maintaining a clean state.

After the first cleaning step with atomic hydrogen, the hydrogen gas remaining in the vacuum chamber 4 is exhausted, and the inside is depressurized to about 1.0 × 10 ⁻¹⁰ Torr. Thereafter, oxygen gas supplied from the oxygen source 8 is introduced into the vacuum chamber 4 by operating the valve 9. The oxygen partial pressure in the vacuum chamber 4 is set to 3.0 × 10 ^{−5 to} 1.0 × 10 ⁻⁷ Torr, and oxygen radicals are generated by RF plasma excited by a high frequency of 13.56 MHz generated by the RF power source 10. Is generated. By irradiating the oxide substrate 5 with the oxygen radicals from the oxygen plasma supply source 11, a second cleaning process for removing organic substances on the surface of the oxide substrate 5 is performed.
Since metal impurities are sufficiently removed from the surface of the oxide substrate 5 by the first cleaning step using atomic hydrogen, oxygen is not added to the surface of the oxide substrate 5 in the second cleaning step. Even if it irradiates with a radical, the organic substance on the surface of the oxide substrate 5 can be removed without causing generation of a metal oxide.
The method of the present invention for performing the first cleaning step and the second cleaning step described above is particularly suitable for the single crystal zinc oxide substrate 5, and the single crystal subjected to atomic hydrogen treatment and oxygen radical irradiation is used. By growing a zinc oxide based semiconductor crystal on the surface of the zinc oxide substrate 5, it becomes possible to obtain a zinc oxide based semiconductor crystal having a zinc oxide thin film having flatness in the atomic layer order on the surface.

The zinc oxide thin film can be grown by MBE (molecular beam epitaxy) on the zinc oxide semiconductor crystal having the surface-cleaned zinc oxide thin film described above.
Crystal growth of the zinc oxide thin film can be performed using, for example, metallic zinc and RF-excited oxygen plasma. The growth temperature of the zinc oxide semiconductor crystal at this time can be in the range of 400 to 1000 ° C.
On the surface of this zinc oxide thin film, both metal impurities and organic impurities can be removed at a high level, and the crystal growth of the zinc oxide thin film is facilitated, resulting in no crystal defects. A zinc oxide thin film having good smoothness and flatness in the atomic layer order can be obtained.

"Growth of zinc oxide thin film using single crystal zinc oxide substrate"
Next, the single crystal zinc oxide substrate is cleaned by the method of the present invention, and the crystal of the zinc oxide thin film on the single crystal zinc oxide substrate is obtained by the MBE method using the cleaned single crystal zinc oxide substrate. The growth will be explained specifically.
The single crystal zinc oxide substrate is degreased with a solvent and introduced into an ultrahigh vacuum chamber having a structure shown in FIG. 1 that can be evacuated to about 1.0 × 10 ⁻¹⁰ Torr or less.
After the single crystal zinc oxide substrate is put into the vacuum chamber, the hydrogen partial pressure is set to 5.0 × 10 ⁻⁶ Torr, the filament is energized to heat the filament to 2100 ° C., and atoms to the single crystal zinc oxide substrate Irradiation with gaseous hydrogen was performed for 30 minutes, and the first cleaning step was performed. At this time, by irradiating the substrate surface with atomic hydrogen without heating the substrate, reduction of the substrate surface can be selectively suppressed, and metal impurities on the substrate surface can be removed while suppressing internal diffusion of impurities such as hydrogen. it can.

After the first cleaning step with atomic hydrogen, the remaining hydrogen gas is exhausted, and the interior of the chamber is exhausted to 1.0 × 10 ⁻¹⁰ Torr. Thereafter, the oxygen partial pressure in the chamber is set to 1.0 × 10 ⁻⁵ Torr, and oxygen radicals are generated by RF plasma excited by a high frequency of 13.56 MHz and 200 W. This oxygen radical was irradiated from the oxygen plasma supply cell toward the single crystal zinc oxide substrate for 10 minutes, and a second cleaning process for cleaning the substrate surface was performed to remove organic substances. Since the metal impurities are sufficiently removed from the surface of the single crystal zinc oxide substrate by the first cleaning step using atomic hydrogen, unnecessary metal oxides are generated in the second cleaning step. The organic substance on the surface of the oxide substrate can be removed without causing it.

Next, a zinc oxide semiconductor crystal is grown on the single crystal zinc oxide substrate cleaned by the first cleaning step by the atomic hydrogen treatment and the second cleaning step by oxygen plasma.
The growth of the zinc oxide semiconductor crystal is performed using metallic zinc and RF-excited oxygen plasma. The growth temperature of the zinc oxide semiconductor crystal at this time can be 400 to 1000 ° C., but here it was 650 ° C.
An observation result (AFM image) by an atomic force microscope (AFM) of the zinc oxide semiconductor crystal grown on the single crystal zinc oxide substrate cleaned as described above according to the method of the present invention is shown in FIG. FIG. 3 shows an AFM image of a zinc oxide semiconductor crystal grown without performing the cleaning step according to the inventive method. 2 and 3 are both μm, the mean square roughness of the sample shown in FIG. 2 is 1.506 nm, and the mean square roughness of the sample shown in FIG. It was 057 nm.
From the comparison of the AFM images of FIG. 2 and FIG. 3, the surface flatness of the zinc oxide semiconductor crystal obtained by carrying out the method of the present invention is clearly improved, and the surface pores generated by the remaining impurities as nuclei are observed. It turns out that it is decreasing.

FIG. 4 shows an X of a zinc oxide semiconductor crystal grown on a single crystal zinc oxide substrate subjected to the cleaning process of the present invention and a zinc oxide semiconductor crystal grown without performing the cleaning process of the present invention. The result of a line diffraction and 2 (theta) -omega measurement is shown. The vertical axis in FIG. 4 indicates the diffraction intensity (arbitrary unit), the horizontal axis indicates 2θ (°), the solid line in FIG. 4 indicates the embodiment of the present invention, and the chain line in FIG. 4 indicates the sample without cleaning treatment. .
In a zinc oxide semiconductor crystal grown on a single crystal zinc oxide substrate not subjected to the treatment of the present invention, an asymmetric diffraction peak is observed on the low angle side of the peak of the zinc oxide semiconductor crystal. This peak is considered to be caused by impurities remaining on the substrate. The asymmetry of the peak is that the impurity forms an impurity layer with metal oxide or organic matter in the zinc oxide semiconductor crystal, which distorts the zinc oxide semiconductor crystal and affects the lattice constant of the zinc oxide semiconductor crystal. It is thought to be due to
On the other hand, the zinc oxide semiconductor crystal grown on the single crystal zinc oxide substrate subjected to the cleaning treatment of the method of the present invention does not show the asymmetric peak as shown by the solid line in FIG. It was a crystal. This indicates that impurities on the single crystal zinc oxide substrate can be removed by both atomic hydrogen treatment and plasma treatment, and that a high-quality zinc oxide semiconductor crystal can be realized.

  From the above, the method of the present invention can provide a clean substrate surface without reducing the surface of the oxide substrate. Further, a zinc oxide semiconductor crystal grown on a single crystal zinc oxide substrate obtained by applying the method of the present invention is obtained as an extremely flat thin film having a level difference corresponding to one atomic layer of the zinc oxide semiconductor single crystal. Is possible.

“Comparative Example 1”: “Atomic hydrogen treatment after oxygen plasma treatment”
In order to prove the effectiveness of the method of the present invention, the crystal growth of a zinc oxide thin film on a single crystal zinc oxide substrate to which the cleaning method of the comparative example is applied will be described.
The single crystal zinc oxide substrate is degreased and introduced into an ultrahigh vacuum chamber of 1.0 × 10 ⁻¹⁰ Torr or less. After introducing the single crystal zinc oxide substrate after degreasing treatment into the vacuum chamber, the brew partial pressure in the chamber is set to 1.0 × 10 ⁻⁵ Torr, and RF plasma excited by a high frequency of 13.56 Maz and 200 W is used. , Generate oxygen radicals. This oxygen radical was irradiated to the single crystal zinc oxide substrate for 10 minutes to remove organic substances on the surface.
After the first cleaning step using oxygen plasma, the remaining oxygen gas is exhausted to 1.0 × 10 ⁻¹⁰ Torr. Thereafter, the hydrogen partial pressure is set to 5.0 × 10 ⁻⁶ Torr, the filament is heated to 2100 ° C., and atomic hydrogen irradiation to the single crystal zinc oxide substrate is performed for 30 minutes. By performing these cleaning processes without heating the substrate, reduction of the substrate surface and internal diffusion of remaining impurities can be suppressed.

A zinc oxide semiconductor crystal was grown on the single crystal zinc oxide substrate treated by the method described above. Crystal growth was performed using metallic zinc and RF-excited oxygen plasma. The growth temperature of the zinc oxide semiconductor crystal at this time can be 400 to 1000 ° C., but here it was 650 ° C.
An atomic force microscope (AFM) observation result of the crystal-grown zinc oxide semiconductor crystal is shown in FIG.
As a result shown in FIG. 5, a zinc oxide semiconductor crystal having a very rough surface was obtained. The root mean square roughness of this sample is 4.692 nm.
2, 3, and 5, the shading display bar expressed as nm on the lower side of the horizontal axis shows a measure of roughness according to the shading of the display color of the AFM image shown in each figure. 2 shows a maximum of 11.95 nm, FIG. 3 shows a maximum of 8.09, and FIG. 5 shows a maximum of 47.99. From comparison of these indices, it can be seen that the surface roughness of the sample showing the AFM image shown in FIG. 5 is much larger than the surface roughness of the sample shown in FIGS.
This is because, in Comparative Example 1, since the oxygen plasma treatment was first performed, the metal impurities present on the substrate surface formed oxides and could not be cleaned even by the subsequent atomic hydrogen treatment, which is a cleaning process. It is believed that there is. In addition, it is thought that the metal oxide can be reduced and removed by changing the conditions of the atomic hydrogen treatment, but in that case, the surface of the base zinc oxide substrate itself is also reduced, which may impair the surface flatness. There is.

  FIG. 6 shows the results of X-ray diffraction 2θ-ω measurement of a zinc oxide semiconductor crystal grown on a single crystal zinc oxide substrate cleaned by the processing method described in Comparative Example 1, and the single crystal oxidation according to the previous example. The result of the X-ray diffraction 2 (theta) -omega measurement of the zinc oxide semiconductor crystal grown on the zinc substrate is compared and shown. In the zinc oxide semiconductor crystal (chain line) grown on the single crystal zinc oxide substrate cleaned by the treatment method of Comparative Example 1, the peak of the zinc oxide semiconductor crystal is broadened as compared with the example (solid line) of the present invention. It can be seen. This is because the organic substance can be removed by the oxygen plasma irradiation in the treatment method described in Comparative Example 1, but the remaining metal impurities form a metal oxide, which distorts the zinc oxide semiconductor crystal. This is thought to be due to the influence on the lattice constant.

  From the above comparison, the surface of the oxide thin film becomes rough even when the oxide substrate is cleaned by performing atomic hydrogen irradiation after the treatment with oxygen plasma and the oxide thin film is grown thereon. On the other hand, it can be seen that the order of removing organic impurities by contacting atomic plasma after removing metal impurities by performing atomic hydrogen irradiation is important.

FIG. 1 is a block diagram showing an example of an apparatus used for carrying out the cleaning method according to the present invention. FIG. 2 is a view showing an example of an AFM image of the surface of the zinc oxide substrate obtained by the method according to the present invention. FIG. 3 is a view showing an example of an AFM image of the surface of the zinc oxide substrate obtained without performing the method according to the present invention. FIG. 4 is a diagram comparing the results of X-ray diffraction 2θ-ω measurement of a sample subjected to the method according to the present invention and the results of X-ray diffraction 2θ-ω measurement of a sample not performed. FIG. 5 is a diagram showing an example of an AFM image of the sample of Comparative Example 1 obtained without performing the method according to the present invention. FIG. 6 is a diagram comparing the result of X-ray diffraction 2θ-ω measurement of a sample subjected to the method according to the present invention and the result of X-ray diffraction 2θ-ω measurement of a sample of Comparative Example 1 that is not performed.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Filament, 2 ... Valve, 3 ... Hydrogen source, 4 ... Vacuum chamber, 5 ... Oxide substrate, 6 ... Hydrogen supply cell, 7 ... Filament heating power source, 8 ... Oxygen source, 9 ... Valve, 10 ... RF power source 11 ... oxygen plasma supply cell.

Claims (3)

The first step of removing metal impurities from the surface of the zinc oxide substrate by bringing at least one of atomic hydrogen and atomic deuterium into contact with the surface without heating the zinc oxide substrate placed in a vacuum atmosphere. Zinc oxide by a method of cleaning a zinc oxide substrate comprising a cleaning step and a second cleaning step of removing organic impurities from the surface of the zinc oxide substrate by bringing oxygen plasma into contact with the surface of the zinc oxide substrate A step of cleaning the surface of the substrate;
Method for producing a zinc oxide thin film characterized by having a step of growing a crystal of zinc oxide to clean the zinc oxide surface of the substrate to obtain a single-crystal zinc oxide thin film. 1.0 × 10 ^-5 The method for producing a zinc oxide thin film according to claim 1, wherein the cleaning treatment is performed in a high vacuum of Torr or less. The method for producing a zinc oxide thin film according to claim 1 or 2, wherein the substrate temperature during the first cleaning treatment is 100 ° C or lower.

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