JP2005239480A - Substrate having single-crystal thin-film layer, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method, wherein a zinc oxide single-crystal thin-film layer having a smooth-surface is manufactured on a mica substrate with good reproducibility by promoting two-dimensional growth of zinc oxide precursors based on monomolecular adsorption by the use of a specific mica substrate and by reacting the zinc oxide precursor layer with water vapor. <P>SOLUTION: The manufacturing method for a substrate having a zinc oxide single-crystal thin-film layer comprises the following steps: a step for forming a zinc oxide precursor thin-film layer on a mica substrate; a step for reacting the precursor thin-film layer with water vapor; and a step for depositing a zinc oxide thin-film on a single-layer zinc oxide thin-film at a high temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a substrate having a single crystal thin film layer in which a zinc oxide precursor compound is deposited on a specific mica substrate, and a zinc oxide single layer thin film is deposited by steam treatment, and zinc oxide is deposited thereon. Relates to a method of manufacturing

  Zinc oxide (ZnO) is a direct transition type semiconductor having a forbidden band width of 3.4 eV, and is expected to be applied to short wavelength light emitting devices such as ultraviolet light emitting diodes (ultraviolet LEDs). Furthermore, recently, it has been studied to use a zinc oxide thin film as a UV light source to excite a phosphor, so that it can be used as a white LED in a general fluorescent lamp, and a new application field using a zinc oxide thin film is expected. Yes.

  Conventionally, a zinc oxide thin film has been formed on a single crystal substrate such as sapphire. Sapphire is non-toxic, chemically stable, and its crystal structure is excellent as a substrate for growing hexagonal wurtzite crystals, so it is also suitable as a substrate for forming GaN thin films, etc. It was used for. As a method for forming a thin film, various methods such as a sputtering method, a molecular beam epitaxy method (MBE), a chemical vapor phase method, and a metal organic chemical vapor phase method have been adopted. However, even if the various methods described above are employed, it has not been possible to form a single crystal zinc oxide thin film having a smooth surface and no grain boundary over a wide range on a sapphire substrate.

  The cause is considered to be due to mismatch of lattice constants of sapphire and zinc oxide, and a device was devised to eliminate the negative effects of mismatch of lattice constants. For example, in Patent Document 1, a corundum-type structure oxide having a lattice constant intermediate between the lattice constants of a thin film to be formed with a substrate is formed on a substrate such as a sapphire single crystal or a silicon single crystal. It is disclosed to form a zinc oxide thin film laminated crystal. In this method, the oxide layer provided on the substrate can alleviate the mismatch of the lattice constant between the zinc oxide and the substrate, thereby improving the orientation and crystallinity of the zinc oxide thin film. However, it is necessary to treat the substrate before forming the zinc oxide thin film, which is not industrially preferable. Further, although this method improves the crystallinity, a single crystal zinc oxide thin film cannot be formed. Furthermore, Ota et al. Reported that a smooth zinc oxide single crystal thin film can be formed by heat-treating zinc oxide deposited on an yttrium-stabilized zirconia single crystal substrate at about 1200 ° C., and the lattice parameter mismatch is too large. It was reported that there was no obstacle (see Non-Patent Document 1). Although this method cannot be applied industrially at all because the heat treatment temperature is too high, it is suggested that there are factors other than the mismatch of lattice constants that hinder a smooth zinc oxide single crystal thin film.

  Also disclosed is a method of converting oxygen atoms on the sapphire substrate surface into nitrogen atoms and depositing zinc oxide thereon (see Non-Patent Document 2). Oxygen atoms on the sapphire substrate are weakly covalent, so when zinc, zinc oxide, or a zinc oxide precursor is deposited, the zinc oxide is deposited more than two-dimensionally over the entire surface of the sapphire substrate. It is considered that a smooth surface cannot be obtained because it is more energetically stable to combine and to grow three-dimensional particles. On the other hand, in the above method, since the oxygen atom having a low covalent bond existing on the surface of the sapphire substrate is replaced with a nitrogen atom having a high covalent bond, zinc, zinc oxide or a zinc oxide precursor is bonded. And a flat zinc oxide single crystal thin film is obtained. However, although this method can improve the adsorption force of the substrate surface, the bonding property is not sufficient, and if the substrate is excessively nitrided, a part of the substrate is etched, and the surface of the substrate There was a problem that the roughness increased. Moreover, since it is necessary to process a board | substrate before forming a zinc oxide thin film, it is industrially unpreferable.

  In addition, the use of a substrate having a highly covalent Si atom or GaAs on the surface of the substrate has been studied. However, when a thin film is deposited in an oxygen atmosphere, the surface is oxidized, which is not preferable.

  In the present invention, as a result of various studies on the type of substrate, the treatment method of the zinc oxide precursor, etc., using a specific mica substrate, two-dimensional growth by monomolecular adsorption of the zinc oxide precursor is performed, A smooth zinc oxide monolayer film is produced by reacting the zinc oxide precursor layer with water vapor. The inventors have found a method capable of producing a zinc oxide single crystal thin film layer on this single layer thin film with good reproducibility, and completed the present invention.

JP-A-5-254991 Heteroepitaxial growth of zinc oxide single crystal thin films on (111) plane YSZ by pulsed laser deposition. Ohta, Hiromichi; Tanji, Hiroaki; Orita, Masahiro; Hosono, Hideo; Kawazoe, Hiroshi, Materials Research Society Symposium Proceedings (1999), 570 (Epitaxial Growth-Principles and Applications), 309-313. Molecular beam epitaxy growth of single-domain and high-quality ZnO layers on nitrided (0001) sapphire surface, Xinqiang Wang, Hiroyuki Iwaki, Masashi Murakami, Xiaolong Du, Yoshihiro Ishitani, Japanese Journal of Applied Physics, Vol.42, (2003) .pp.L99-L101

  The present invention uses a specific mica substrate to cause two-dimensional growth by monomolecular adsorption of a zinc oxide precursor, and reacts the zinc oxide precursor layer with water vapor to deposit a smooth zinc oxide single layer thin film. Provided is a production method capable of producing a zinc oxide single crystal thin film on this single layer thin film with good reproducibility.

  That is, the present invention includes a step of forming a zinc oxide precursor thin film layer on a mica substrate, a step of reacting the precursor thin film layer with water vapor, and a step of depositing a zinc oxide thin film on a single-layer zinc oxide thin film. The present invention relates to a method for manufacturing a substrate having a zinc oxide single crystal thin film layer.

The mica substrate is preferably a mica substrate made of F ₂ KMg ₃ (AlSi ₃ O ₁₀ ).

The precursor thin film layer of zinc oxide, produced by thermal decomposition of zinc acetate mu ₄ - Okisohekisa -μ- acetato four zinc _{[Zn 4 (μ 4 -O)} (μ-CH 3 COO) 6] thin film composed of It is preferable that

  Moreover, this invention relates to the board | substrate which has a zinc oxide single crystal thin film layer obtained from the said manufacturing method.

  In the present invention, a zinc oxide precursor thin film layer (monomolecular film layer) can be firmly formed on a substrate with a high adsorption force. As a result, a zinc oxide single crystal thin film layer (single layer) having a flat surface can be obtained. ZnO) can be easily formed on the substrate, and a substrate having a high-performance zinc oxide single crystal thin film layer can be manufactured industrially.

The present invention
First step: forming a zinc oxide precursor thin film layer on a mica substrate;
A second step: a step of reacting the precursor thin film layer with water vapor; and a third step: a zinc oxide single crystal thin film layer comprising a step of depositing a zinc oxide thin film on the single layer thin film generated by the water vapor treatment. The present invention relates to a method for manufacturing a substrate having the same.

  In the first step, a precursor of zinc oxide is sublimated and deposited on a mica substrate kept at room temperature to form a precursor thin film layer.

Examples of the zinc oxide precursor to be deposited on mica include zinc acetate, diethyl zinc, and acetylacetonato zinc. Among them, it is decomposed mu ₄ - because it can generate Okisohekisa -μ- acetato four zinc _{[Zn 4 (μ 4 -O)} (μ-CH 3 COO) 6], zinc acetate is preferred. Μ ₄ -Oxohexa-μ-acetatotetrazinc produced by decomposition of zinc acetate has (1) a Zn—O bond in the molecule, and (2) a crystal structure in which the aggregation of the molecules is the same as that of zinc oxide. (3) Since it has a quaternary structure in which zinc exists outside the molecule and is distorted, it is preferable in that a strong bond can be formed with oxygen atoms on the substrate surface.

  Examples of the method for depositing the zinc oxide precursor include metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and laser ablation. Among these, MOCVD is preferable in that it can be deposited over a large area, the deposition rate is high, and the mass productivity is high.

  The sublimation conditions depend on the type of zinc oxide precursor to be deposited, and are not particularly limited as long as the deposited zinc oxide precursor sublimates and deposits on the substrate.

  Since the mica substrate used in the present invention has a covalent Si—O bond on the substrate surface, it can be easily bonded to zinc, zinc oxide, or a zinc oxide precursor. The Si-O bond on the surface of the mica substrate is combined with zinc, zinc oxide or a zinc oxide precursor, and zinc, zinc oxide or a zinc oxide precursor grows two-dimensionally, and a zinc oxide precursor thin film layer (monomolecular layer) ) Can be firmly formed on the substrate with a high adsorption force. As a result, a flat surface zinc oxide single crystal thin film layer can be easily formed on the substrate, and a substrate having a high performance zinc oxide single crystal thin film layer can be manufactured.

  Furthermore, the mica substrate has an advantage that it can be easily cleaved and a clean surface can be provided if necessary, eliminating the costly polishing operation.

  As the mica substrate, either a natural mica substrate or a synthetic mica substrate can be used.

As natural mica, muscovite: (OH) ₂ KAl ₂ (AlSi ₃ O ₁₀ ), soda mica (Paragonite): (OH) ₂ NaAl ₂ (AlSi ₃ O ₁₀ ), phlogopite: ( OH) ₂ KMg ₃ (AlSi ₃ O ₁₀ ) and the like. As for these, the rough stone of the magnitude | size of about 20 cm x 20 cm x 1 cm can be obtained. When high transparency is required, muscovite is preferable. These natural mica substrates can be used up to a temperature of about 600 ° C.

Examples of the synthetic mica include fluorine phlogopite: F ₂ KMg ₃ (AlSi ₃ O ₁₀ ). Fluorophlogopite can (1) increase the transparency because it can reduce the impurities of iron, (2) can be used at a high temperature of about 1000 ℃, (3) mass production greatly cost It is preferable because it can be lowered.

  Either a natural mica substrate or a synthetic mica substrate can be suitably used up to a substrate temperature of about 600 ° C. However, when the substrate temperature exceeds 600 ° C., particularly when the substrate temperature is 700 ° C. or higher, it is preferable to use synthetic mica.

  In the second step, the precursor thin film layer is reacted with water vapor to change the zinc oxide precursor of the precursor thin film layer to zinc oxide.

  The substrate temperature of the substrate having the precursor thin film layer obtained in the first step is raised to 100 to 170 ° C., held for 5 to 60 minutes, and reacted with water vapor. At this time, the vapor pressure of water in the apparatus is preferably 2 to 10 Pa or more. The reaction time depends on the pressure of the water vapor. When the water vapor pressure is low, the reaction time becomes long. Conversely, when the water vapor pressure is high, the reaction is completed in a short time. If the reaction is insufficient, the zinc oxide precursor on the substrate will not be completely zinc oxide.

  In the third step, the zinc oxide thin film is deposited on the single-layer zinc oxide thin film obtained in the second step by various methods. Examples of the deposition method include metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), laser ablation, and sputtering. MOCVD is preferable in that it can be deposited over a large area, the deposition rate is high, and the mass productivity is high.

  According to the manufacturing method of the present invention, the annealing process is unnecessary, and since the zinc oxide single crystal thin film layer can be formed at a low temperature of about 500 ° C., the substrate can be easily produced industrially. Become.

  The thickness of the zinc oxide single crystal thin film layer obtained by this method is not particularly limited, and may be adjusted appropriately to a desired thickness.

  By the production method of the present invention, a smooth zinc oxide single crystal thin film layer can be produced on a mica substrate with good reproducibility.

  Next, although the manufacturing method of this invention is demonstrated using an Example, this invention is not limited to an Example.

(substrate)
The substrate used in the examples is
This is a synthetic mica substrate (made by Ito Kiko Co., Ltd.) made of F ₂ KMg ₃ (AlSi ₃ O ₁₀ ) synthesized by the crucible descent method.

Example 1
Using a metal organic chemical vapor deposition apparatus (MOCVD apparatus), zinc acetate was sublimated at 220 ° C. for 2 minutes, and [Zn ₄ (μ ₄ −O) (μ− CH ₃ COO) ₆ ] was deposited. Thereafter, it was stored for 30 minutes in an atmosphere of a total pressure of 33 Pa and a water vapor pressure of 2 Pa, and reacted with water to obtain a zinc oxide thin film adsorbed monomolecularly. Single-layer thin film formation was confirmed by observation with an atomic force microscope. Further, it cannot be confirmed from the X-ray diffraction (XRD) measurement of the single layer film that the single layer material is zinc oxide, but μ ₄ -oxohexa-μ-acetatotetrazinc [OZn ₄ ( From the XRD of the film obtained by steaming a thick film in which CH ₃ COO) ₆ ] was volumed for a long time under the steam pressure condition, it was confirmed that the film was a film made of zinc oxide. The layer film is considered to be zinc oxide.

  This single layer thin film was heated to various temperatures, and the surface morphology was observed with an atomic force microscope. The result is shown in FIG. In the monolayer film sufficiently reacted with water vapor, no change in shape was observed up to 300 ° C. (FIG. 1A), and the surface roughness increased slightly at the deposition temperature of 570 ° C. (FIG. 1 ( b)). From this result, it can be seen that even when the single layer thin film is heated to about 570 ° C., particle growth hardly occurs and the surface morphology preferable for two-dimensional growth is maintained.

  A zinc oxide thin film was deposited on the single layer thin film by MOCVD. Detailed deposition conditions are a substrate temperature of 570 ° C., a total pressure of 100 Pa, a water vapor pressure of 6 Pa, and oxygen of 12 Pa. The deposition time is 1 hour. The surface morphology of the obtained thin film is shown in FIG. 2 (magnification is (a) 1 μm × 1 μm, (b) 5 μm × 5 μm). Grain growth was not observed, and a good zinc oxide thin film with a surface roughness of about several nm was obtained. This thin film had a c-axis oriented perpendicular to the substrate, and X-ray pole figure measurement revealed that the in-plane crystal orientation was perfectly aligned. From this result, this thin film was confirmed to be a single crystal zinc oxide having a smooth surface.

Comparative Example 1
Zinc oxide was deposited directly without producing a single layer zinc oxide thin film. The substrate is the same synthetic mica as in Example 1, the substrate temperature is 570 ° C., the total pressure is 100 Pa, the water vapor pressure is 6 Pa, and the oxygen is 12 Pa. The surface morphology of the obtained zinc oxide thin film was observed with an atomic force microscope. The results are shown in FIG. 3 (magnification is (a) 1 μm × 1 μm, (b) 5 μm × 5 μm). As is clear from the figure, there were a large number of particles, and the surface roughness was very poor at 20 nm.

The AFM surface image after heat processing of a single layer ZnO film | membrane is shown. The heat treatment temperatures are (a) 300 ° C and (b) 570 ° C. 2 shows an AFM surface image of a ZnO thin film deposited at 570 ° C. on a single layer ZnO film. The magnification is (a) 1 μm × 1 μm and (b) 5 μm × 5 μm. The AFM surface image at the time of depositing a ZnO thin film directly at 570 degreeC, without forming single layer ZnO is shown. The magnification is (a) 1 μm × 1 μm and (b) 5 μm × 5 μm.

Claims (4)

Zinc oxide comprising a step of forming a zinc oxide precursor thin film layer on a mica substrate, a step of reacting the precursor thin film layer with water vapor, and a step of depositing a zinc oxide thin film at a high temperature on a single layer zinc oxide thin film A method for manufacturing a substrate having a single crystal thin film layer. The manufacturing method according to claim 1, wherein the mica substrate is a mica substrate made of F ₂ KMg ₃ (AlSi ₃ O ₁₀ ). The precursor thin film layer of zinc oxide, produced by thermal decomposition of zinc acetate mu ₄ - Okisohekisa -μ- acetato four zinc _{[Zn 4 (μ 4 -O)} (μ-CH 3 COO) 6] thin film composed of The manufacturing method according to claim 1 or 2. The board | substrate which has a zinc oxide single crystal thin film layer obtained by the manufacturing method of Claim 1, 2 or 3.