JP4399059B2 - Thin film structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin film structure formed on the surface of a single crystal substrate and a method for manufacturing the same. The present invention relates to a thin film structure that can be used as a conductive substrate for providing an epitaxial thin film such as a conductive memory and FET, and a method for manufacturing the same.
[0002]
[Prior art]
Pb _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three The (PLZT) -based material has an extremely large electro-optic coefficient among oxide ferroelectric materials having a good electro-optic effect, and LiNbO has a composition exhibiting a primary electro-optic coefficient. _Three GH Haertling and CE Land, J. Amer. Ceram. Soc.Vol. Is a composition that exhibits a second order electro-optic coefficient and has the highest level among ferroelectric materials. 54. p.1 (1971), etc., and its application to optical devices is expected.
[0003]
The inventors have made SrTiO doped with impurities. _Three A PLZT thin film having a uniform perovskite phase can be epitaxially grown on the substrate, and the PLZT thin film formed on this substrate has been found to exhibit excellent characteristics and has already been filed (Japanese Patent Application No. 10- 157609).
[0004]
However, SrTiO doped with impurities _Three However, only a substrate having a size of about 1 inch can be manufactured, and the application range is limited because the substrate size is limited. Also, SrTiO doped with impurities _Three Since there is no cleavage, even if a PLZT thin film is provided, the end face must be mechanically polished in order to use it as an optical waveguide device, and the process is complicated and requires a lot of production time. .
[0005]
[Problems to be solved by the invention]
In order to broaden the application range of the PLZT material and to manufacture an optical waveguide device using the PLZT material by a simpler method, the present inventors _Three We are investigating the formation of a conductive thin film having a perovskite phase structure and capable of epitaxially growing a PLZT thin film on a general-purpose substrate such as a sapphire substrate or an MgO substrate.
[0006]
If a conductive thin film having a uniform perovskite phase can be epitaxially grown on a substrate such as sapphire on which a substrate having a size of several inches can be grown, a wide range of applications can be opened. Further, if a PLZT thin film can be epitaxially grown through a conductive thin film on a sapphire substrate, an MgO substrate, or a GaAs substrate or Si substrate using MgO as a buffer layer through a conductive thin film, the end face is easily formed by cleavage. It is possible to achieve a significant cost reduction. If a PLZT thin film can be epitaxially grown via a conductive thin film on a sapphire substrate, MgO substrate, or a GaAs substrate or Si substrate using MgO as a buffer layer, monolithic integration with a semiconductor device is possible.
[0007]
However, sapphire and MgO substrates are ABO _Three It was very difficult to epitaxially grow a conductive thin film having a uniform perovskite phase structure on these single crystal substrates without having a perovskite phase structure of the type. .
[0008]
Accordingly, an object of the present invention is a thin film structure formed on the surface of a single crystal substrate, which is single crystal or epitaxial and has an ABO _Three A thin film structure having a conductive or semiconductive thin film having a perovskite phase structure on its surface and a method for manufacturing the same.
[0009]
[Means for Solving the Problems]
To achieve the above objective, According to reference examples The thin film structure is a thin film structure formed on the surface of a single crystal substrate, and is a single crystal or epitaxial Pb provided on the surface of the single crystal substrate. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three And a single crystal or epitaxial layer provided on the surface of the buffer layer. _Three And a conductive or semiconductive thin film having a perovskite phase structure.
[0010]
Also, According to reference examples The method of manufacturing a thin film structure is a method of manufacturing a thin film structure formed on the surface of a single crystal substrate, and a single crystal or epitaxial Pb is formed on the surface of the single crystal substrate. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three After the buffer layer is formed, the surface of the buffer layer is monocrystalline or epitaxial and is ABO. _Three A conductive or semiconductive thin film having a perovskite phase structure is formed.
[0011]
Nb-doped SrTiO _Three La-doped SrTiO _Three , BaPbO _Three , SrRuO _Three , YBa ₂ Cu _Three O _7-x , SrVO _Three LaNiO _Three , La _0.5 Sr _0.5 CoO _Three Conductive or semiconductive materials such as non-perovskite surfaces have ABO _Three An epitaxial thin film having a type perovskite phase structure is difficult to grow, and the thin film after growth has poor crystallinity, and a non-perovskite phase is likely to be mixed therein.
[0012]
Invention according to reference example Then, single crystalline or epitaxial Pb _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three The buffer layer is made of a perovskite phase structure, and a conductive or semiconductive epitaxial thin film is formed through this buffer layer, so that ABO is formed on the single crystal substrate. _Three A conductive or semiconductive epitaxial thin film having a perovskite phase structure can be provided.
[0013]
Single crystal or epitaxial and ABO _Three As a conductive or semiconductive thin film having a perovskite phase structure, SrRuO _Three A thin film made of is particularly preferred.
[0014]
For the formation of the buffer layer, solid phase epitaxial growth using application of a metal organic compound solution is the most desirable growth method because of good flattening characteristics.
[0015]
And The thin film structure according to claim 1, Invention according to reference example In the above, the buffer layer is made of single crystal or epitaxial Pb in the range of 0 <x <0.30 and 0 <y <0.20. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three And a single crystal or epitaxial Pb in the range of 0 <x <0.20 and 0.20 <y <1.0 provided on the surface of the first buffer layer. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three And a second buffer layer.
[0016]
Claims 7 Is a method for manufacturing a thin film structure formed on the surface of a single crystal substrate, and 0 <x <0.30, 0 <y <on the surface of the single crystal substrate. Single crystal or epitaxial Pb in the range of 0.20 _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three A first buffer layer is formed, and a single crystal or epitaxial Pb in the range of 0 <x <0.20 and 0.20 <y <1.0 is formed on the surface of the first buffer layer. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three A second buffer layer is formed, and the surface of the second buffer layer is monocrystalline or epitaxial and is ABO. _Three A conductive or semiconductive thin film having a perovskite phase structure is formed.
[0017]
PLZT having a composition in the range of 0 <x <0.30 and 0 <y <0.20 constituting the first buffer layer is difficult to form a pyrochlore layer and can easily perform epitaxial growth of a perovskite single phase. Next, when a second buffer layer made of PLZT having a composition in the range of 0 <x <0.20 and 0.20 <y <1.0 is epitaxially grown on the surface of the first buffer layer, the second buffer layer Since it grows on the surface of the first buffer layer having the same crystal structure and composition, it is usually difficult to grow a perovskite single phase. However, as a perovskite single phase without the formation of a pyrochlore layer, Can be epitaxially grown. Since the obtained second buffer layer has a perovskite phase structure, ABO is passed through this second buffer layer. _Three A conductive or semiconductive epitaxial thin film having a perovskite phase structure can be provided.
[0018]
In addition, PLZT having a composition in the range of 0 <x <0.30 and 0 <y <0.20 constituting the first buffer layer can easily form deep grooves in the crystal grain boundaries as shown in FIG. The thickness of the first buffer layer is preferably in the range of 1 to 40 nm, and the crystal grains are preferably separated into islands as shown in FIG.
[0019]
Since the crystal grains of the first buffer layer are in the form of islands, when the second buffer layer is epitaxially grown on the surface of the first buffer layer, it becomes possible to fill the gap without creating a gap between the islands. The surface of the second buffer layer becomes smooth. Further, since the obtained second buffer layer has a perovskite phase structure and good crystallinity and smoothness, a conductive or semiconductive epitaxial thin film is formed through this second buffer layer. And better quality ABO _Three A conductive or semiconductive epitaxial thin film having a perovskite phase structure can be formed.
[0020]
In the present invention, the term “single crystal” is generally called “epitaxial”, from a defect-free one obtained by thinning a single crystal as it is to one containing crystal defects such as twins. , But the crystal orientation is unidirectionally oriented in one direction at least by the θ-2θ X-ray diffraction pattern, that is, the random orientation plane is identified as 1% or less of the diffraction intensity of the single orientation plane .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Reference example As shown in FIG. 1, the thin film structure is formed of single crystal or epitaxial Pb provided on the surface of the single crystal substrate 10. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three A buffer layer 12 comprising a single crystal or an epitaxial layer provided on the surface of the buffer layer 12 and ABO. _Three And a conductive or semiconductive thin film 14 having a type perovskite phase structure. Hereinafter, according to the manufacturing process, Along with reference examples, the present invention The thin film structure will be described in detail.
[0022]
As a material of the single crystal substrate 10, ZrO ₂ , Y ₂ O _Three 8% -ZrO ₂ , MgO, MgAl ₂ O _Four , Al ₂ O _Three , ZnO, ZnGa ₂ O _Four , CdGa ₂ O _Four , CdGa ₂ O _Four , Mg ₂ TiO _Four MgTi ₂ O _Four , SrTiO _Three , BaTiO _Three , BaZrO _Three LaAlO _Three , LiNbO _Three LiTaO _Three And oxides such as Si, Ge, diamond and the like, AlAs, AlSb, AlP, GaAs, GaSb, InP, InAs, InSb, AlGaP, AlLnP, AlGaAs, AlInAs, AlAsSb II-VI compound semiconductors such as ZnS, ZnSe, ZnTe, CaSe, CdTe, HgSe, HgTe, CdS, and the like. Among these, Al is available for large substrates ₂ O _Three Si, MgO, MgO provided on the surface, and GaAs provided MgO on the surface are more preferable.
[0023]
First, the buffer layer 12 is provided on the surface of the single crystal substrate 10.
[0024]
The buffer layer 12 is made of single crystal or epitaxial Pb. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three It is. When the buffer layer has a single layer structure, an epitaxial Pb in the range of 0 <x <0.3 and 0.1 <y <0.6 can be formed because a highly smooth surface can be formed. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three It is preferable to use (PLZT).
[0025]
And the thin film structure of the present invention, As shown in FIG. 2, the buffer layer has a two-layer configuration of a first buffer layer 12A and a second buffer layer 12B. Is .
[0026]
When the buffer layer has a two-layer structure, the first buffer layer 12A includes an epitaxial Pb in the range of 0 <x <0.30 and 0 <y <0.20 indicated by the region A in FIG. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three (PLZT) is used, and the second buffer layer 12B has an epitaxial Pb in the range of 0 <x <0.20 and 0.20 <y <1.0 shown by the region B in FIG. _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three (PLZT) is used. In addition, from the viewpoint of surface smoothing, the thickness of the first buffer layer 12A is preferably in the range of 1 to 40 nm.
[0027]
The buffer layer 12 is formed by vapor phase epitaxial growth methods such as electron beam evaporation, flash evaporation, ion plating, Rf-magnetron sputtering, ion beam sputtering, laser ablation, MBE, CVD, plasma CVD, MOCVD, and sol-gel. It can be formed on the single crystal substrate 10 by an epitaxial growth method selected from a solid phase epitaxial growth method using a wet process such as a MOD method or a MOD method. A coating process in which the obtained ferroelectric precursor solution is applied to form a thin film, a thermal decomposition process in which the thin film is pyrolyzed, and a crystal in which the pyrolyzed thin film is heated to a crystal growth temperature and solid phase epitaxially grown. A solid phase process in which the growth process is performed one or more times. Takisharu growth method is particularly preferred. A buffer layer having a flat surface can be formed by solid phase epitaxial growth using a metal organic compound solution.
[0028]
As the metal organic compound, metal alkoxides and metal salts which are reaction products of Pb, La, Zr and Ti metals and organic compounds, preferably organic compounds having a boiling point of 80 ° C. or higher at normal pressure are used. It is done.
[0029]
As an organic ligand of a metal alkoxide compound, R ¹ O- or R ² OR ^Three O- (wherein R ¹ And R ² Represents an aliphatic hydrocarbon group, R ^Three Represents a divalent aliphatic hydrocarbon group which may have an ether bond). These metal alkoxide compounds are R ¹ OH or R ² OR ^Three It can be synthesized by distillation or reflux in an organic solvent represented by OH, and R ¹ And R ² As the aliphatic hydrocarbon group, an alkyl group having 1 to 4 carbon atoms is preferable, and R ^Three Are preferably an alkylene group having 2 to 4 carbon atoms and a divalent group having 4 to 8 carbon atoms in which an alkylene group having 2 to 4 carbon atoms is bonded by an ether bond.
[0030]
Specifically, as the solvent having a boiling point of 80 ° C. or more, for example, (CH _Three ) ₂ CHOH (boiling point 82.3 ° C.), CH _Three (C ₂ H _Five ) CHOH (boiling point 99.5 ° C.), (CH _Three ) ₂ CHCH ₂ OH (boiling point 108 ° C.), C _Four H ₉ OH (boiling point 117.7 ° C.), (CH _Three ) ₂ CHC ₂ H _Four OH (boiling point 130.5 ° C.), CH _Three OCH ₂ CH ₂ OH (boiling point 124.5 ° C.), C ₂ H _Five OCH ₂ CH ₂ OH (boiling point 135 ° C.), C _Four H ₉ OCH ₂ CH ₂ Alcohols such as OH (boiling point 171 ° C.) are most desirable, but are not limited to these. ₂ H _Five OH (boiling point: 78.3 ° C.) can also be used.
[0031]
The ferroelectric precursor solution comprises a plurality of metal organic compounds selected from metal alkoxides and metal salts, alcohols, diketones having a predetermined composition, preferably a boiling point of 80 ° C. or higher at normal pressure, It can be obtained by mixing in a solvent selected from ketone acids, alkyl esters, oxyacids, oxyketones, and acetic acid, or by reacting with these solvents.
[0032]
The composition of the metal organic compound is Pb _1-x La _x (Zr _y Ti _1-y ) _{1-x / 4} O _Three It is preferable that Pb is contained in excess of the ratio of Pb, La, Zr, Ti corresponding to the stoichiometric composition of Pb, and it is preferable to make Pb 5 at% (5 mol%) or more. It is also effective to add a small amount of various metal organic compounds containing metal elements other than Pb, La, Zr, and Ti as necessary.
[0033]
The ferroelectric precursor solution can be applied to the surface of a single crystal substrate after hydrolysis of the added metal organic compound, but in order to obtain a high-quality epitaxial ferroelectric thin film, the ferroelectric precursor solution can be applied. It is preferable not to decompose. From the viewpoint of the quality of the thin film obtained, the ferroelectric precursor solution is preferably adjusted in a dry nitrogen or argon atmosphere.
[0034]
The ferroelectric precursor solution is applied by a method selected from a spin coating method, a dipping method, a spray method, a screen printing method, and an ink jet method. These coating steps are preferably performed in a dry nitrogen or argon atmosphere from the viewpoint of the quality of the thin film obtained.
[0035]
An amorphous thin film is formed by thermally decomposing a thin film obtained by applying the ferroelectric precursor solution at a temperature at which crystallization does not occur. The temperature range of thermal decomposition is preferably 100 to 500 ° C, more preferably 200 to 400 ° C. Moreover, it is preferable to heat up to the thermal decomposition temperature at a temperature increase rate of 0.1 to 1000 ° C./second, preferably at a temperature increase rate of 1 to 100 ° C./second. The thermal decomposition and the temperature increase are preferably performed in an oxygen-containing atmosphere, preferably in oxygen.
[0036]
The pyrolyzed thin film is heated at the crystal growth temperature for 1 second to 24 hours, preferably 10 seconds to 12 hours, and the ferroelectric thin film is grown on the substrate surface by solid phase epitaxial growth. The temperature range for crystal growth is preferably 600 ° C. or more, more preferably 600 to 1200 ° C., and particularly preferably 600 to 800 ° C. Moreover, it is preferable to raise the temperature rapidly at a temperature rising rate of 10 to 500 ° C./second, preferably a temperature rising rate of 20 to 100 ° C./second until the crystal growth temperature. The crystal growth and the temperature increase are preferably performed in an oxygen-containing atmosphere, preferably in oxygen.
[0037]
In the crystal growth step, when the temperature is raised to the crystal growth temperature, the temperature range in which nuclei of the pyrochlore phase are generated, specifically, the temperature range of 350 to 450 ° C. is set to a temperature increase rate of 10 to 500 ° C./second, More preferably, it is preferable to increase the temperature at a high rate of 20 to 100 ° C./second. Thus, the nucleation of a pyrochlore phase is suppressed by heating up at high speed. From the viewpoint of productivity, it is preferable to apply the temperature increase rate not only in the nucleation temperature range of the pyrochlore phase but also throughout the temperature increase process.
[0038]
The excess amount of Pb and the heating rate affect the crystal structure. In order to suppress nucleation of the pyrochlore phase, it is effective to set the Pb amount to be greater than 0% or a temperature increase rate of 10 ° C./second or more as described above, and desirably the Pb amount is greater than 0% and It is effective that the temperature rising rate is 10 ° C./second or more, and more desirably, the Pb content is 5% or more and the temperature rising rate is 20 ° C./second or more as shown in the range A of FIG.
[0039]
As the oxygen atmosphere, it is desirable from the viewpoint of the quality of the thin film obtained to use an oxygen atmosphere that has been dried for at least a certain period of time, but it may be humidified as necessary.
[0040]
The buffer layer 12 is formed by performing the above-mentioned solid phase epitaxial growth one or more times, but the film thickness of the PLZT thin film formed by one solid phase epitaxial growth is preferably 10 to 1000 nm. More preferably, it is set to ˜200 nm.
[0041]
In addition, after solid phase epitaxial growth, it is desirable to hold at a temperature lower than the crystal growth temperature, desirably 100 to 600 ° C., and then cool. Cooling is preferably performed at a cooling rate of 0.01 to 100 ° C./second.
[0042]
By the above method, on the single crystal substrate 10 of different materials, the density and refractive index are the same as those of the single crystal, and the surface is optically smooth. For example, Pb (Zr _1-x Ti _x ) O _Three (PZT), Pb _1-x La _x (Zr _1-y Ti _y ) _{1-x / 4} O _Three A monocrystalline PLZT buffer layer 12 such as (PLZT) can be formed.
[0043]
Next, on the buffer layer 12, it is single crystal or epitaxial and is ABO. _Three A conductive or semiconductive thin film 14 having a type perovskite phase structure (hereinafter referred to as “conductive or semiconductive thin film 14”) is formed.
[0044]
Examples of the material of the conductive or semiconductive thin film 14 include SrRuO. _Three Nb-doped SrTiO _Three La-doped SrTiO _Three , BaPbO _Three , YBa ₂ Cu _Three O _7-x , SrVO _Three LaNiO _Three , La _0.5 Sr _0.5 CoO _Three It is possible to use SrRuO _Three However, the present invention is not limited to these, and can be selected from materials having similar crystal symmetry and lattice constant to the PLZT buffer layer.
[0045]
The conductive or semiconductive thin film 14 is formed by vapor phase epitaxial growth methods such as electron beam evaporation, flash evaporation, ion plating, Rf-magnetron sputtering, ion beam sputtering, laser ablation, MBE, CVD, plasma CVD, MOCVD, and the like. It can be formed on the buffer layer by an epitaxial growth method selected from a solid phase epitaxial growth method using a wet process such as a sol-gel method or a MOD method.
[0046]
By the above method, the single crystal substrate 10 made of different materials has the same crystallinity as the single crystal and the surface is optically smooth. For example, SrRuO _Three A single crystal conductive or semiconductive thin film 14 such as can be formed.
[0047]
【Example】
Example 1
Sapphire Al ₂ O _Three (1102) A 10 nm-thick epitaxial PLZT (28/0/100) buffer layer is grown on a single crystal substrate by solid phase epitaxy, and a 90-nm thick epitaxial PLZT (9/65/35) buffer layer is further grown. Further, epitaxial SrRuO with a film thickness of 100 nm _Three As a result, the thin film structure having the structure shown in FIG. 2 was formed on the single crystal substrate.
[0048]
First, anhydrous lead acetate (Pb (CH _Three COO) ₂ ), Lanthanum isopropoxide (La (O-i-C _Three H ₇ ) _Three ), And titanium isopropoxide (Ti (O-i-C _Three H7) _Four ) As a starting material and dissolved in 2-methoxyethanol at a ratio of Pb: La: Ti = 72: 28: 100 so that Pb has a stoichiometric composition with respect to other elements, and distilled for 6 hours. Then, reflux was performed for 18 hours to finally obtain a precursor solution for PLZT (28/0/100) having a Ti concentration of 0.6M.
[0049]
This precursor solution was passed through a 0.2 μm filter and passed through Al. ₂ O _Three The substrate was spin coated. All the above operations are N ₂ I went in the atmosphere. Prior to spin coating, the substrate is solvent cleaned, etched with HCl, rinsed with deionized water, and finally N ₂ Dry in by spin coating with ethanol.
[0050]
Next, humidification O ₂ The temperature was raised to 300 ° C. at 10 ° C./sec in the atmosphere, held at 300 ° C. for 2 minutes, then heated to 650 ° C. at 10 ° C./sec and held at 650 ° C. for 30 minutes, Finally, the electric furnace was turned off and cooled. As a result, a PLZT (28/0/100) buffer layer having a thickness of 10 nm was grown by solid phase epitaxial growth. When the surface of the PLZT (28/0/100) buffer layer was observed with an atomic force microscope (AFM), it was in the form of an island structure as shown in FIG.
[0051]
Next, similarly, anhydrous lead acetate, lanthanum isopropoxide, zirconium isopropoxide (Zr (Oi-C _Three H ₇ ) _Four ), And titanium isopropoxide as a starting material, Pb: La: Zr: Ti = 91: 9: 65: 35 at a ratio of Pb: La: Zr: Ti = 91: 9: 65: 35 It was dissolved in ethanol, distilled for 6 hours, and then refluxed for 18 hours. Finally, a precursor solution for PLZT (9/65/35) having a Zr + Ti concentration of 0.6 M was obtained. This precursor solution was passed through a 0.2 μm filter, and an Al provided with a PLZT (28/0/100) buffer layer. ₂ O _Three The substrate was spin coated. All the above operations are N ₂ I went in the atmosphere.
[0052]
Next, humidification O ₂ The temperature was raised to 300 ° C. at 10 ° C./sec in the atmosphere, held at 300 ° C. for 2 minutes, then heated to 650 ° C. at 10 ° C./sec and held at 650 ° C. for 30 minutes, Finally, the electric furnace was turned off and cooled. Thereby, a 90 nm thick PLZT (9/65/35) thin film was grown by solid phase epitaxial growth.
[0053]
Thereafter, the substrate temperature is 600 ° C., the substrate / target distance is 50 mm, the Rf power is 50 W, Ar / O by Rf magnetron sputtering. ₂ SrRuO with a film thickness of 100 nm in atmosphere and pressure of 1 Pa _Three The conductive thin film was epitaxially grown.
[0054]
As shown in FIG. 6, according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The diffraction intensity of (110) is strong and SrRuO. _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three (110) // PLZT (110) // PLZT (110) // Al ₂ O _Three The structure of (1102) was obtained. SrRuO _Three The rocking curve half width by the (110) plane was as good as 2.0 °.
[0055]
SrRuO _Three Although the surface of the conductive thin film was observed with an optical microscope, nothing was seen because the surface was uniform, and the result of observation with AFM was that the surface was extremely uniform and smooth, as shown in FIG. In addition, the surface was so specular that no contrast was obtained, and the roughness was only 1.3 nm in terms of Ra. Further, the resistivity was as good as about 0.2 mΩ · cm.
(Comparative Example 1)
Sapphire Al ₂ O _Three (1102) SrRuO on a single crystal substrate by Rf magnetron sputtering _Three A conductive thin film was directly grown. Growth conditions are: substrate temperature 600 ° C., substrate / target distance 50 mm, Rf power 50 W, Ar / O ₂ The atmosphere and pressure were 1 Pa. As shown in FIG. 8, according to the X-ray diffraction θ-2θ pattern, only a few unidentifiable weak peaks were observed, and the epitaxial SrRuO _Three A thin film could not be obtained.
( Reference example 2)
Almost the same as in Example 1, sapphire Al ₂ O _Three (1102) An epitaxial PZT (30/70) buffer layer having a thickness of 100 nm is grown on a single crystal substrate by solid phase epitaxy, and further SrRuO. _Three A thin film structure having the structure shown in FIG. 1 was formed on a single crystal substrate by growing a conductive thin film.
[0056]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three (110) // PZT (110) // Al ₂ O _Three The structure of (1102) was obtained.
(Example 3)
Almost the same as in Example 1, sapphire Al ₂ O _Three (1102) An epitaxial PLZT (20/0/100) buffer layer having a thickness of 10 nm is grown on a single crystal substrate by solid phase epitaxy, an epitaxial PZT (52/48) buffer layer is grown, and SrRuO is further grown. _Three By growing the conductive thin film, a thin film structure having the structure shown in FIG. 2 was formed on the single crystal substrate.
[0057]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three (110) // PZT (110) // PLZT (110) // Al ₂ O _Three The structure of (1102) was obtained.
Example 4
Almost the same as in Example 1, sapphire Al ₂ O _Three (1102) An epitaxial PZT (20/80) buffer layer having a thickness of 10 nm was grown on a single crystal substrate by solid phase epitaxy, and an epitaxial PZT (25/75) buffer layer was grown. Furthermore, SrRuO _Three Conductive thin film metal organic compound precursor precursor solution is provided with Al with PLZT (25/75) buffer layer ₂ O _Three Perform spin coating on the substrate, O ₂ The temperature was raised to 300 ° C. at 10 ° C./sec in the atmosphere, held at 300 ° C. for 2 minutes, then heated to 650 ° C. at 10 ° C./sec and held at 650 ° C. for 30 minutes, Finally, the electric furnace was turned off and cooled. As a result, SrRuO having a film thickness of 100 nm _Three Conductive thin films were grown by solid phase epitaxial growth.
[0058]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three (110) // PZT (110) // PZT (110) // Al ₂ O _Three The structure of (1102) was obtained.
(Example 5)
Almost the same as in Example 1, sapphire Al ₂ O _Three An epitaxial PLZT (28/0/100) buffer layer having a thickness of 5 nm is grown on a (0001) single crystal substrate by solid phase epitaxy, an epitaxial PLZT (8/65/35) buffer layer is grown, and SrRuO is further grown. _Three By growing the conductive thin film, a thin film structure having the structure shown in FIG. 2 was formed on the single crystal substrate.
[0059]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three (111) // PLZT (111) // PLZT (111) // Al ₂ O _Three A structure of (0001) was obtained.
(Example 6)
Sapphire Al ₂ O _Three An epitaxial PLZT (28/0/100) buffer layer having a thickness of 10 nm is grown on a (0001) single crystal substrate by Rf magnetron sputtering at a substrate temperature of 650 ° C., and epitaxially grown at a substrate temperature of 650 ° C. by Rf magnetron sputtering. A PLZT (8/65/35) buffer layer is grown, and SrRuO is further grown at a substrate temperature of 600 ° C. by Rf magnetron sputtering. _Three By growing the conductive thin film, a thin film structure having the structure shown in FIG. 2 was formed on the single crystal substrate.
[0060]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three (111) // PLZT (111) // PLZT (111) // Al ₂ O _Three A structure of (0001) was obtained.
(Example 7)
An epitaxial PLZT (28/0/100) buffer layer having a film thickness of 10 nm is grown on the MgO (100) single crystal substrate by solid phase epitaxial growth in the same manner as in Example 1, and the epitaxial PLZT (8/65/35) buffer layer is grown. And grow SrRuO _Three By growing the conductive thin film, a thin film structure having the structure shown in FIG. 2 was formed on the single crystal substrate.
[0061]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three A structure of (100) // PLZT (001) // PLZT (001) // MgO (100) was obtained.
(Example 8)
An epitaxial PLZT (28/0/100) buffer layer and an epitaxial PLZT (8/65/35) buffer layer having a thickness of 10 nm are grown on a GaAs (100) single crystal substrate on which an MgO buffer layer has been epitaxially grown, and further SrRuO. _Three By growing the conductive thin film, a thin film structure having the structure shown in FIG. 2 was formed on the single crystal substrate.
[0062]
An epitaxial MgO buffer layer on a GaAs (100) substrate is formed by using an excimer laser deposition method in which a metal Mg target surface is instantaneously heated by a UV laser pulse to perform deposition. ₂ The substrate was grown at a substrate temperature of 350 ° C. by reactive film formation in an atmosphere. Furthermore, after epitaxially growing a PLZT buffer layer on the MgO buffer layer by a laser deposition method, an epitaxial PLZT (8/65/35) buffer layer is grown, and SrRuO is further grown. _Three A conductive thin film was grown.
[0063]
SrRuO _Three The surface of the conductive thin film is extremely uniform and smooth, and according to the X-ray diffraction θ-2θ pattern, SrRuO _Three The conductive thin film is a perovskite single phase, and the crystallographic relationship of each layer is a single orientation SrRuO. _Three A structure of (10) // PLZT (001) // PLZT (001) // MgO (100) // GaAs (100) was obtained.
[0064]
【The invention's effect】
According to the present invention, it is single crystalline or epitaxial and is ABO. _Three A thin film structure having a conductive or semiconductive thin film having a perovskite phase structure on the surface can be easily formed on the surface of the single crystal substrate.
[0065]
The surface of the thin film structure is smooth and has a single crystal or epitaxial shape with high crystallinity and is ABO. _Three It consists of a conductive or semiconductive thin film having a perovskite phase structure, so that it can be used for epitaxial thin film optical waveguides such as optical switches, light modulation elements, light deflection elements, second harmonic elements, and non-volatile memories, FETs, etc. It can be used as a conductive substrate provided with a thin film.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing an example of the structure of a thin film structure of the present invention.
FIG. 2 is a cross-sectional view schematically showing another example of the structure of the thin film structure of the present invention.
FIG. 3 Pb _1-x La _x (Zr _1-y Ti _y ) _{1-x / 4} O _Three It is a phase diagram of (PLZT).
FIG. 4 is a graph showing a preferred range of excess Pb amount and temperature increase rate.
5 is an atomic force microscope (AFM) photograph of the buffer layer surface of Example 1. FIG.
FIG. 6 shows SrRuO of Example 1. _Three It is an X-ray diffraction pattern of a conductive thin film.
7 is an atomic force microscope (AFM) photograph of the buffer layer surface of Example 1. FIG.
FIG. 8 shows SrRuO of Comparative Example 1 _Three It is an X-ray diffraction pattern of a conductive thin film.
FIG. 9 is a schematic cross-sectional view of a PLZT thin film in a range of 0 <x <0.30 and 0 <y <0.20 provided on a single crystal substrate.
FIG. 10 is a schematic cross-sectional view of a PLZT buffer layer in a range of 0 <x <0.30 and 0 <y <0.20 provided on a single crystal substrate with a thickness of 1 to 40 nm.
[Explanation of symbols]
10 Single crystal substrate
12 Buffer layer
12A First buffer layer
12B Second buffer layer
14 Conductive or semiconductive thin film

Claims (13)

A thin film structure formed on the surface of the single crystal substrate, provided on the surface of the single crystal substrate a single crystal form or epitaxial-like _{Pb 1-x La x (Zr} y Ti 1-y) 1-x _A buffer layer made of _{/ 4} O ₃ , and a conductive or semi-conductive thin film having a single crystal or epitaxial ABO ₃ type perovskite phase structure provided on the surface of the buffer layer ,
The buffer layer is, 0 <x <0.30,0 <y < ranging 0.20 single crystalline or epitaxial-like _{Pb 1-x La x (Zr} y Ti 1-y) 1-x / 4 O _A first buffer layer made of ₃ and a single crystal or epitaxial Pb _{1− in} the range of 0 <x <0.20 and 0.20 <y <1.0 provided on the surface of the first buffer layer. _{x La x (Zr y Ti 1} -y) 1-x / 4 O 3 and a second buffer layer composed of a thin film structure constructed by.   The thin film structure according to claim 2, wherein the first buffer layer has a thickness of 1 nm to 40 nm. The thin film structure according to claim 1 or 2 , wherein the conductive or semiconductive thin film having an ABO ₃ type perovskite phase structure is a thin film made of SrRuO ₃ . The single crystal substrate, sapphire (Al ₂ O ₃₎ thin film structure according to any one of claims 1 to 3. The thin film structure according to any one of claims 1 to 3 , wherein the single crystal substrate is magnesium oxide (MgO). The thin film structure according to any one of claims 1 to 3 , wherein the single crystal substrate is a semiconductor having magnesium oxide (MgO) on a surface thereof. A method of manufacturing a thin film structure formed on the surface of a single crystal substrate, wherein the single crystal substrate has a single crystal or epitaxial structure in the range of 0 <x <0.30 and 0 <y <0.20. Jo of _{Pb 1-x La x (Zr} y Ti 1-y) forming a first buffer layer made of _{1-x /} 4 O _3, on the surface of the first buffer layer, 0 <x <0.20, 0.20 <y <1.0 in the range of single-crystalline or epitaxial-like _{Pb 1-x La x (Zr} y Ti 1-y) forming a second buffer layer composed of _{1-x /} 4 O _3, on the surface of the second buffer layer, forming a conductive or semi-conductive thin film having a single crystal form or a epitaxial like ABO ₃ type perovskite phase structure, the manufacturing method of the thin film structure. The buffer layer is a coating process in which a ferroelectric precursor solution obtained from a metal organic compound is applied to form a thin film, a thermal decomposition process in which the thin film is thermally decomposed, and the thermally decomposed thin film is brought to a crystal growth temperature. The method for producing a thin film structure according to claim 7 , wherein the thin film structure is formed by performing a crystal growth step of raising the temperature and performing solid phase epitaxial growth one or more times. The metal organic compound, method for producing a _{Pb 1-x La x (Zr} y Ti 1-y) 1-x / 4 O 3 stoichiometry thin film structure according to claim 8 containing excess Pb than the composition . 10. The method for manufacturing a thin film structure according to claim 8, wherein the ferroelectric precursor is a mixture or a reaction product of a plurality of metal organic compounds selected from metal alkoxides and metal salts. In the crystal growth process, when raising the temperature to the crystal growth temperature, in any one of claims 8 to 10, raising the temperature at a heating rate of 350 to 450 10 to 500 ° C. / sec the temperature range of ° C. The manufacturing method of the thin film structure of description. The method for manufacturing a thin film structure according to any one of claims 8 to 11 , wherein the crystal growth temperature is 600 to 800 ° C. The method for manufacturing a thin film structure according to any one of claims 8 to 13 , wherein the thermal decomposition step and / or the crystal growth step are performed in an atmosphere containing oxygen.

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