JP2001222913A - Dielectric thin film, its manufacturing method, and its electronic product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an effective use of grating distortion due to misfit grating and reduce leak current, and improve fatigue characteristics. SOLUTION: Substantially one layer of X3}O corresponding to one atom layer of X3}O is inserted into a substrate 10 similar to a thin film in crystalline construction at an appropriate interval while perovskite oxide X1} X2}O3 layer 12 is caused to grow epitaxially. X1} and X3} are Ca or the like, X2}, Ti or the like, and 'O', oxygen. An X3}O layer 14 introduced so that the perovskite structure of the X1} X2}O3 layer 12 is divided, but in a state of extremely high structural fitness with the perovskite structure to form a laminar perovskite structure. The X3}O layer 14 acts as a blocking layer against misfit (grating misfit) dislocation introduction, thus resulting in ferroelectric thin film holding a high grating distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dielectric thin film having a perovskite structure, a method of manufacturing the same, and an electronic component thereof.

[0002]

BACKGROUND ART An oxide thin film material having a perovskite structure has a very wide variety of functions such as ferroelectricity, high dielectric constant, electro-optic effect, piezoelectric effect, pyroelectric effect, and superconductivity. It has been applied to a wide range of electronic devices such as ferroelectric memory devices and optical sensors. For example, DRAM (Dynamic Random Access Memory)
ry), MMIC (Microwave Monolithic Integrated Ci)
rcuit) and a capacitor of an MCM (Multi Chip Module) are one of suitable applications.

[0003] In recent years, in particular, the development of a memory element focusing on the high dielectric constant and ferroelectric characteristics of a perovskite oxide thin film has been spotlighted, and as a DRAM capacitor aimed at high integration by reducing the capacitor area. Applications or high-speed non-volatile ferroelectric memories utilizing hysteresis characteristics by ferroelectricity are being studied.

However, this oxide thin film material having a perovskite structure is a crystalline material, unlike conventional amorphous materials such as SiO ₂ and Si ₃ N ₄ . For this reason, advanced thin-film crystal growth technology and defect control technology are required to express desired characteristics. For example, Pb (Zr _m
Ti _1-m ) O ₃ material has a large spontaneous polarization value,
Because of its relatively high Curie temperature of 300 ° C. or higher, it is used as a nonvolatile ferroelectric memory material.

However, due to the formation of cation vacancies due to the volatility of Pb, the generation of oxygen defects near the interface of the Pt electrode, the introduction of defects due to semiconductor processes such as the formation of a passivation film, etc., the characteristics may be significantly deteriorated. Are known. In particular, the deterioration of spontaneous polarization due to the polarization inversion cycle, so-called fatigue characteristics, is deeply caused by the above-mentioned defects, and is a serious problem in practical use. Further, in a Pb-based perovskite, a heterophase having a pyrochlore structure that greatly reduces ferroelectricity is easily formed in a thin film low-temperature process, and this point is also a major problem in practical use.

On the other hand, BaTiO ₃ is well known as a ferroelectric perovskite structure oxide having no Pb, and its structure is extremely stable as compared with a Pb-based perovskite. However, this BaTiO ₃ -based material has a small spontaneous polarization and a Curie point of 120 ° C., which is close to room temperature.
For this reason, the temperature dependence of the polarization amount is extremely large, and as a result, it is unsuitable as a nonvolatile capacitor for a ferroelectric memory element.

[0007]

SUMMARY OF THE INVENTION The present invention focuses on the above points, and is thermodynamically stable, can effectively utilize lattice distortion caused by lattice mismatch, and further has a leak current. To provide a dielectric thin film, a method of manufacturing the same, and an electronic component capable of reducing the fatigue and improving the fatigue characteristics.
That is the purpose.

[0008]

In order to achieve the above object, the present invention provides {X1} having an oxygen 12 coordination structure and {X1}
And {X3} having a different coordination structure from Ca, Mg, Sr,
When {X2} composed of at least one element selected from Ba and Pb and having a six-coordinate oxygen structure is composed of at least one element selected from Ti and Zr, and “O” is oxygen Formed on substrates with similar crystal structures
In the perovskite layer having a composition of {X1} {X2} O ₃ , {X1
3} O is inserted to form a lattice distortion due to lattice mismatch with the substrate.

Another invention relates to {X having an oxygen 12 coordination structure.
1} and {X3} having a different coordination structure from {X1} are represented by Ca, M
{X2} composed of at least one element selected from g, Sr, Ba, and Pb and having an oxygen six-coordinate structure is composed of at least one element selected from Ti and Zr, and {X}
Is the sum of the constituent elements of {X1} and {X3}, and when “O” is oxygen, a dielectric thin film having a composition of {X} _m {X2} O _{2 + m} (where m> 1), A perovskite layer having a composition of {X1} {X2} O ₃ formed on a substrate having a similar crystal structure, and {X3} inserted into the perovskite layer
O and has lattice distortion due to lattice mismatch with the substrate.

[0010] Still another invention has an oxygen 12 coordination structure.
{X1} and {X3} having a different coordination structure from {X1} are represented by C
at least one selected from a, Mg, Sr, Ba, Pb
{X2} composed of various kinds of elements and having an oxygen 6 coordination structure is represented by T
When at least one element selected from i and Zr is used and “O” is oxygen, a perovskite layer having a composition of {X1} {X2} O ₃ is added two-dimensionally or three-dimensionally to {X3 } O is inserted.

The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment First, a first embodiment of the present invention will be described in detail. As shown in FIG. 1A, SrRuO ₃ having a similar crystal structure to a thin film to be formed, or SrTiO doped (added) with Nb.
₃ (hereinafter referred to as “Nb—SrTiO ₃ ”) or other single crystal substrate (lower electrode) 10 is prepared. Then, on this single crystal substrate 10, perovskite oxide {X1}
{X2} while the O ₃ layer 12 is epitaxially grown, {X3} of substantially one atomic layer to substantially one molecule layer at appropriate intervals O1
Insert 4. Therefore, {X3} O is not always in a state that can be called a layer, but is referred to as a “layer” in the following description for convenience.

Here, {X1} is at least one element selected from the group consisting of Ca, Mg, Sr, Ba and Pb, having an oxygen 12 coordination structure. {X2} is at least one element selected from the group consisting of Ti and Zr having a six-coordinate oxygen structure. {X3} has a coordination structure different from that of {X1} and is at least one element selected from the group consisting of Ca, Mg, Sr, Ba, and Pb. “O” is oxygen.

As shown in FIG. 1 (B) or (C),
The {X3} O layer 14 is introduced in the form of dividing the perovskite structure of {X1} {X2} O ₃ layer 12. In the figure, an octahedron 12A represents a perovskite structure of {X2} O ₆ octahedra, a black circle 12B represents an element {X1}, and a white circle 12B.
C represents the element {X3}. However, the element {X3} 12C easily replaces the position of the adjacent element {X1} 12B. That is, {X3} O is randomly inserted into the perovskite layer 12.

In the example shown in FIG. 1B, the {X3} O layer 14 has a rock salt type structure having a very high structural consistency with the perovskite structure, and has a layered perovskite structure similar to the so-called K ₂ NiF ₄ structure. This is an example in which is formed. On the other hand, a structure which is not necessarily a rock salt type structure as shown in FIG. In any case, the {X3} O layer 14 having a rock salt type structure acts as a blocking layer against the introduction of misfit (lattice mismatch) dislocations.
As a result, a ferroelectric thin film having high lattice strain can be obtained.

The {X3} O layer 14 having a rock salt type structure
Divides a three-dimensional network of Ti—O bonds, which is also a main factor in the development of ferroelectricity and also serves as an electron conduction path. Therefore, the introduction of the {X3} O layer 14 is effective in reducing the leak current and improving the fatigue characteristics. Note that {X1} {X
When the 2} existence ratio of {X3} O layer 14 to the O ₃ layer 12 is too high, cooperative action between units having the perovskite structure is lowered, so that the phenomenon occurs that ferroelectricity is remarkably lowered.

The {X3} O layer 14 may be introduced irregularly so as not to form a superlattice structure, or may have a superlattice structure. For example, if the {X3} O layer 14 is introduced irregularly so as not to form a superlattice structure, the translational symmetry is not given in the film thickness direction (vertical direction indicated by arrow F1 in FIG. 1A). Thus, the effective critical film thickness can be increased, and the introduction of misfit dislocations can be effectively suppressed. Conversely, when the {X3} O layer 14 is introduced so as to have a superlattice structure, as described later, good insulating properties can be obtained.

When the dielectric thin film 16 having the above-described laminated structure is epitaxially grown on the substrate 10 having a similar crystal structure to the dielectric thin film, the dielectric thin film is formed in a state where the lattice is distorted. The lattice strain formed by this causes a new dielectric characteristic. In addition, in the present embodiment, the strain due to the {X3} O layer 14 is also introduced as described above. Therefore, these two types of strains contribute to the dielectric characteristics of the dielectric element according to the present embodiment. As shown in FIG. 1B, the {X1} {X2} O ₃ layer 12 and the {X3} O layer 14
Can be introduced into the dielectric film by the number of insertions of the {X3} O layer 14, which is a rock salt structure layer,
This also contributes to the dielectric properties.

{X4} having an oxygen 12-coordination structure is represented by C
at least one selected from a, Mg, Sr, Ba, Pb
When {X5} is composed of a cation different from {X4}, {X1} is represented by {X4} _1−m {X5} _m (where m> 0) It may be configured. In this case, {X5} acts as an impurity, causing distortion in the perovskite layer. The perovskite structure is generally more stable when the amount of impurities {X5} is small, that is, when m <0.5.

Next, the manufacturing process will be described in more detail. First, the substrate 10 acting as a lower electrode is made of conductive SrTiO ₃ doped with Nb or La.
Perovskite oxide substrates. Second, Mg
Ca {X91} which is a conductive oxide is placed on an insulating perovskite single crystal substrate such as O, SrTiO ₃ , LaAlO ₃ or the like.
O ₃ (where {X91} = V, Cr, Fe, or Ru), S
r {X92} O ₃ (where {X92} = V, Cr, Fe, or R
u), La {X93} O ₃ (where {X93} = Ti, Co, N
i, or _{Cu), La 1-m Sr} m {X94} O 3 ( provided that
{X94} = V, Mn, or Co, m> 0.23), Ba
PbO ₃ , SrRuO ₃ , SrlrO ₃ , Sr ₂ RuO
_{4, Sr} 2 IrO _4, or _{(La 1-m Sr m)} 2
One obtained by epitaxial growth of any one of CuO ₄ (where m <0.3) can be used.

Third, a barrier layer on a semiconductor Si substrate, MgAl ₂ O ₄ , MgO, CeO ₂ , α-Al ₂ O
₃ , a conductive oxide, Ca, on an epitaxial oxide such as YSZ (yttrium-stabilized zirconium).
{X95} O ₃ (where {X95} = V, Cr, Fe, or R
u), Sr {X96} O ₃ (where {X96} = V, Cr, F
e, or Ru), La {X97} O ₃ (where {X97} = T
i, Co, Ni, or _{Cu), La 1-m Sr} m {X98}
O ₃ (where {X98} = V, Mn, or Co and m> 0.
23), BaPbO ₃ , SrRuO ₃ , SrIrO ₃ ,
Sr ₂ RuO ₄ , Sr ₂ IrO ₄ , or (La
_{1-m Sr m) 2 CuO} 4 ( proviso that m any of <0.3) is epitaxially grown and the like.

On such a substrate 10, for example, a laser ablation method, an MBE (Molecular Beam Epitaxy) method,
The dielectric thin film 16 is formed by a thin film manufacturing technique such as a sputtering method. That is, {X1} {X2} O ₃ layer 12
A laminated thin film of the {X3} O layer 14 is formed. {X3} O layer 14
Is formed using known atomic layer control. For example, in the case of the laser ablation method, the laser output and the number of pulses are adjusted to form substantially one atomic layer. Similarly, in the case of sputtering, the output of the plasma and the sputtering time are adjusted, and in the case of CVD, the gas amount is adjusted to substantially form about one atomic layer. In this case, it is technically difficult to control the film formation of the {X3} O layer 14, but a slight difference in the supply amount of the {X3} O is caused by the formation of the {X3} O layer 14 in the film thickness direction. Has been confirmed to be acceptable. As described later, the composition of {X1} {X2} O ₃ layer 12 at the time of film formation
By growing {X1} O excess, it grew three-dimensionally
The {X3} O layer (see FIG. 2) can be easily formed.

FIG. 3 shows an example of an apparatus for producing a dielectric thin film according to the present embodiment. In this apparatus, a perovskite compound is deposited on a substrate for film formation by a laser ablation method to produce a dielectric thin film having a layered perovskite structure. In FIG. 1, a target 102 is placed in a vacuum chamber 100, and a deposition substrate 10 is placed at a predetermined distance from the target 102. Oxygen gas or ozone may be introduced into the vacuum chamber 100 as needed. As the laser light source 104, for example, A having a wavelength λ = 193 nm
An rF excimer laser is used. A laser beam 106 emitted from a laser light source 104 is configured to irradiate the target 102 via an optical system 108 such as a mirror or a lens.

The vacuum chamber 100 is evacuated by an exhaust device 110 such as a TMP (turbo molecular pump).
12 are provided. A film thickness monitor 114 is provided near the surface of the film formation substrate 10. Further, RHEED (reflection high-energy electron diffraction) gun 120, RHEED screen 122, high-sensitivity camera 1
The RHEED gun 120 is evacuated by the exhaust device 126.

As the target 102, for example, a ceramic sintered body or a powder pressed body manufactured by a usual powder metallurgy technique is used. The sintered body is obtained by mixing raw material powders to have a desired composition, and then performing preliminary firing, molding, and firing. The pressed powder body is formed by pressing without sintering.

When the target 102 is irradiated with the laser beam 106, the target 1
From 02, the vapor is scattered into the oxygen atmosphere, and a thin film having substantially the same composition as the target 102 is formed on the opposing film forming substrate 10.

As the target 102, for example, a sintered body of a perovskite oxide SrTiO _{3 and} a sintered body of SrO (or a pressed powder body) are prepared, and these are alternately used to form a laminated film on the substrate 10. By doing, S
A layered perovskite oxide thin film containing the rO layer two-dimensionally is obtained. A specific example will be described later as an embodiment.

<Second Embodiment> Next, a second embodiment of the present invention will be described. In this embodiment, in the above-mentioned layered perovskite oxide, the {X3} O layer 1
{X1} {X2} O ₃ layer 12
{X1} 'element having an ionic radius different from that of the {X1} ion. Here, {X1} ′ is Ca, Mg, S
At least one element selected from the group consisting of r, Ba, and Pb. By doing so, lattice distortion other than that caused by lattice mismatch between the substrate 10 and the thin film 16, that is, distortion due to the difference in ionic radius is effectively introduced.

The ionic radius of the {X1} ′ ion may be larger or smaller than the ionic radius of {X1} in the {X1} {X2} O ₃ layer 12 which is the parent phase. However, by selecting an ion having a smaller ion radius than the {X1} ion of the {X1} {X2} O ₃ layer 12, which is the parent phase, the crystal structure can be stabilized.

In general, from a simple geometric point of view,
The structural stability of the ionic crystal is inferred from the ionic radius of each constituent element. The larger the ionic radius, the higher the coordination number, and the more stable the structure. On the other hand, in the dielectric thin film of the above-mentioned structure, the coordination number of the {X3} ions insert {X3} O layer 14 is a perovskite structure {X1} {X2} O ₃ layer 1
2 is smaller than the coordination number of the {X1} ion. For this reason, the {X1} ′ element having a smaller ionic radius is more likely to be {X3}
By preferentially occupying the cation sites of the O layer 14, the crystal structure is stabilized. By utilizing this phenomenon, the layered perovskite oxide of this embodiment can be more stably generated. Also, by changing the ion radius ratio between the {X1} ion and the {X1} ′ ion within a range where the structural stability can be maintained, the lattice strain can be effectively controlled.

Further, in order to effectively introduce lattice distortion,
Part of the {X1} ion element in the {X1} {X2} O ₃ layer 12 may be replaced with “R” ions having different ionic radii. As the “R” ion, rare earth elements such as La,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, and Ho
At least one element selected from the group consisting of is preferred. In the dielectric thin film having such a configuration, the {X3} O layer 1
The larger lattice strain is induced by the synergistic effect of the lattice distortion caused by partial introduction of "R" ion having a different ion radius from that of the {X1} ion, and excellent characteristics such as high spontaneous polarization are obtained. . Further, by partially introducing “R” ions having different valences, it is possible to suppress generation of carriers due to oxygen vacancy or the like.

In addition, when the element having a small ionic radius enters preferentially and contains a large amount, the crystal structure becomes more stable. For example, when the perovskite layer is BaTiO ₃ , CaO is introduced.

Third Embodiment Next, a third embodiment of the present invention will be described. In the above embodiment, the {X3} O layer 1
4 is introduced two-dimensionally into the {X1} {X2} O ₃ layer 12, but the composition of the thin film represented by {X} {X2} O ₃ which is simply formed is {X}
By making O excessive, a crystalline thin film containing the {X3} O layer can be obtained. In this case, however, as shown in FIG. 2, the {X3} O layer 14 is introduced into the {X1} {X2} O ₃ layer 12 which is the parent phase of the perovskite structure in a three-dimensional disorder. Become. Also in the present embodiment, the {X3} O layer 1
The fact that No. 4 acts as a blocking layer for introducing misfit dislocations is the same as in the above embodiment. In this three-dimensional structure, the composition of the entire thin film is excessive in {X3} sites.

In this embodiment, when the {X1} ion is composed of a combination of two or more elements having different ionic radii, ie, ({X1} ′ _n {X
1} ” _mn ) {X2} O _{2 + m} , the {X1} ′ element having a small ionic radius is selectively selected from the {X3} O layer
3} The crystal structure can be stabilized by precipitation at the cation position. Where {X1} ′ and {X1} ″ are Ca, M
At least one element selected from the group consisting of g, Sr, Ba, and Pb, where m> 1, n> 0. Note that the ionic radius of the {X1} ′ element is smaller than the ionic radius of {X1} ″.

Also in this embodiment, the crystal structure becomes more stable when the element having a small ionic radius preferentially enters the {X3} O layer and contains a large amount. For example, a perovskite layer _{(Sr m1 Ca s1) TiO 3} ( provided that m1
+ S1 = 1), the {X3} O layers _{(Sr m2 Ca} s2) O
(Where m2 <s2).

<Example> An example of the present invention will be described below. (1) First Embodiment In this first embodiment, an ArF excimer laser having a wavelength of 193 nm is used as the laser light source 104 shown in FIG. The atmosphere oxygen pressure when forming the thin film was 1.3 Pa, and the temperature of the substrate 10 was 600 ° C.
As the substrate 10, an Nb—SrTiO ₃ single crystal substrate having a (100) plane as a surface (film formation surface) is used, and as a target 102, a sintered body of a perovskite oxide SrTiO ₃ and a pressed SrO powder body Two were prepared. Laser ablation was performed by using these alternately, and a layered perovskite dielectric thin film having a superlattice structure in which a SrO layer was included two-dimensionally was formed on the substrate 10.

Specifically, five layers of SrTiO ₃ are formed,
A dielectric thin film is formed by forming substantially one SrO layer. FIG. 4A shows RHEE during film formation.
This shows how the D intensity changes with time. From the intensity change pattern, substantially one layer of SrO is formed, and SrO is formed thereon.
It can be seen that substantially five layers of TiO ₃ are formed.

Further, when a high-resolution transmission electron microscope (TEM) image of a cross section of the obtained dielectric thin film was examined, it was found that a SrO 3 insertion layer having a rock salt type structure in a SrTiO ₃ crystal having a perovskite structure had a two-dimensional structure. At the atomic layer level. In this dielectric thin film, not only a structure in which SrO layers and SrTiO ₃ layers are alternately and simply laminated in one direction, but also a thermally induced SrO layer having a three-dimensionally perpendicular relationship is formed. Was also seen.

On the other hand, Sr ₆ T
with i 5 _O 16 _{+ m,} thereby forming a dielectric thin film of the comparative example under the same conditions. In this way, a SrO-excess three-dimensional perovskite film is obtained.

Next, the superlattice perovskite film of SrTiO ₃ / SrO described above and a perovskite film in excess of SrO will be compared. FIG. 4 shows the results of X-ray diffraction.
(B) was obtained. In the figure, the graph GA shows the diffraction result of the superlattice perovskite film, and the graph GB shows the S
It is a diffraction result of a rO excess perovskite film. As is apparent from comparison between the two, a peak indicated by an arrow F4 exists in the superlattice perovskite film, and a period of the superlattice exists.

Next, FIG. 5 shows an example of a comparison between the two electrical characteristics. The electric characteristics shown in the figure were measured by forming an electrode of platinum on each of the perovskite films. In the figure, the solid line graph GA
Is the characteristic of the superlattice perovskite film (relative permittivity εr
= 244), the dotted line graph GB is the characteristic of the SrO-rich perovskite film (relative permittivity εr = 302), and the dashed line graph GC is the characteristic of the stoichiometric SrTiO ₃ perovskite single crystal (relative dielectric constant εr). = 298).

First, referring to FIG. 5, when examining the amount of leakage current when a voltage is applied, the superlattice perovskite film has the lowest leakage current. On the other hand, the SrO-excess perovskite film has the highest capacitance, followed by the superlattice perovskite film. As described above, by adopting the super lattice structure, although the capacitance is slightly reduced, the withstand voltage can be significantly improved.

[0043] (2) In Example 2 ...... present embodiment, the perovskite layer is _{({Ba 0.8 Ca 0 .2}} 0.98 {La}
_0.02 ) TiO ₃ , which contains S
rO is introduced. Specifically, as a target,
_{({Ba 0.8 Ca 0.2} 0} .98 {La} 0.02) T
A sintered body of iO _{3 and} a sintered body of SrO were prepared, and laser ablation was performed by using them alternately in the same manner as in the above-described embodiment to obtain a layered perovskite dielectric material including a SrO rock salt type structure layer two-dimensionally. A body thin film was formed on the substrate. According to this, {La} _0.02 acts as an impurity, causing distortion in the perovskite layer.

(3) Embodiment 3 In this embodiment, the target 102 is made of Sr having an {X1} ion excess composition.
_A dielectric thin film was prepared using a _1.5 TiO _3.5 sintered body. In this embodiment, the substrate 10 is also an Nb-SrTiO ₃ single crystal substrate as in the above embodiment, and the substrate temperature is 600 ° C.

When a transmission electron microscope image of a cross section of the obtained dielectric thin film was examined, it was confirmed that a three-dimensional and extremely structurally conformable SrO layer was formed in the perovskite structure at an atomic layer level. We were able to. Examination of the selected area electron beam diffraction image confirmed the presence of a cross streak spot suggesting the formation of a layered perovskite structure.

The dielectric constant of the dielectric thin film of this embodiment increases three-dimensionally and isotropically by introducing the SrO layer.
Misfit dislocations are not introduced due to the blocking effect of the layer. Further, the thin film lattice is completely two-dimensionally restricted by the lattice of the substrate 10, and an in-plane compressive stress of about 1 GPa is generated in the thin film.

(4) Fourth Embodiment In this embodiment, two BaTiO ₃ sintered bodies and two SrO sintered bodies were used as the targets 102, and the SrO layer was irregularly introduced into the BaTiO ₃ layer. A dielectric thin film was prepared. As a base of the substrate 10, a SrTiO ₃ single crystal substrate functioning as a lower electrode was used. The conductive perovskite SrR
A substrate obtained by epitaxially growing uO ₃ was used as the substrate 10, and the substrate temperature was set at 600 ° C.

The dielectric thin film obtained as described above is made of Sr
With the introduction of the O layer, no misfit dislocations are introduced and the thin film lattice is completely constrained two-dimensionally to the lattice of the substrate 10,
It showed high ferroelectricity.

(5) Embodiment 5 In this embodiment, {Sr _0.8 Ca _0.2 } _1.1 Ti is used as the target 102.
O _3.1 was used. By doing so, {Sr
A three-dimensional perovskite film with an excess of _0.8 Ca _0.2 } is formed.

(6) Embodiment 6 Next, the dielectric of the present invention
Example of using thin film for ferroelectric nonvolatile memory
explain. As shown in FIG.
MgAl oxide on the i-substrate 50₂O₄Membrane 52, conductive
SrRuO which is an electrically conductive oxide ₃Membrane 54, layer according to the invention
Perovskite film 56 and conductive oxide Sr
RuO₃It has a structure in which films 58 are stacked. here
And two SrRuO₃The thin films 54 and 58 are respectively
Function as the upper and lower electrodes,₂O₄Membrane 52
Is used as a buffer layer for forming a film on the Si substrate 50.
Function.

In the dielectric memory device having such a configuration, the MgAl ₂ O ₄ film 52 is epitaxially grown on the Si substrate 50 with a perfect plane orientation, and the SrRuO ₃ film 54 is further grown thereon. I have. This SrRuO
_{The three} film 54 functions as a conductive oxide electrode having a perovskite structure. Since {Ba _0.3 Sr _0.7 } TiO ₃ and SrO, which are ferroelectric oxide layers, are formed on this electrode in a layered manner, the perovskite film 56 is easily epitaxially grown.

Therefore, in the ferroelectric memory device of the present embodiment, not only the excellent leak characteristics and the strain-induced ferroelectric characteristics having the layered perovskite structure according to the present invention, but also the ferroelectric thin film perfectly lattice-matched By realizing the oxide electrode interface, it is possible to avoid the problem of adhesion between the ferroelectric thin film and the electrode and the diffusion of constituent elements that cause deterioration of fatigue characteristics, particularly, diffusion of oxygen, which are observed when a Pt electrode is used.

<Other Embodiments> The present invention has many embodiments, and various modifications can be made based on the above disclosure. For example, the following is also included. (1) Although the laser ablation method has been mainly described in the above embodiment, the same layered structure can be obtained by applying the technique of the artificial superlattice for forming a two-dimensional periodic structure having a desired composition in the order of an atomic layer and a molecular layer. A perovskite structure is feasible. In this case, an SrTiO ₃ thin film having a perovskite structure is formed by alternately laminating the SrO molecular layers and the TiO ₂ molecular layers. Can be obtained.

(2) In Example 4, the MgAl ₂ O ₄ film 52 was used as a buffer layer on which a conductive oxide having a perovskite structure was epitaxially grown on the Si substrate 50 and epitaxially grown. However, the buffer layer is not limited to this.
Various oxides epitaxially grown on the Si substrate can be used depending on the lattice matching of the conductive substrate to be used. For example, MgO, CeO ₂ , α-Al ₂ O ₃ , YS
Z (yttrium stabilized zirconium) can be used.

An epitaxial type is formed on the buffer layer 52.
Regarding the conductive oxide 54 to be formed, the upper layered
Lattice matching with buskite film 56 and lower buffer layer 52
Various oxides with perovskite structure in consideration of performance
May be used. For example, Ca {X81} O₃(However, {X81}
= V, Cr, Fe, Ru), Sr {X82} O₃(However,
{X82} = V, Cr, Fe, Ru), La {X83} O₃(T
Dashi {X83} = Ti, Co, Ni, Cu), La_1-mS
r_m{X84} O₃(However, {X84} = V, Mn, Co, m>
0.23), BaPbO₃, SrRuO₃, SrIrO
₃, Sr₂RuO ₄, Sr₂IrO₄, (La_1-mS
r_m)₂CuO₄(Where m <0.3)
A lobskite oxide is applicable.

(3) In the fourth embodiment, the application example of the dielectric memory element has been described. However, the present invention is not limited to this, and can be applied to dielectric films of various electronic components. For example, by applying the present invention as a DRAM capacitor or an MCM decoupling capacitor, the functions of these components can be enhanced.

[0057]

As described above, according to the present invention,
The following effects can be obtained. (1) Since {X3} O is inserted and formed in the perovskite layer having the composition of {X1} {X2} O ₃ , the lattice strain caused by the lattice mismatch between the substrate and the perovskite layer is effectively used. In addition, the leakage current can be reduced and the fatigue characteristics can be improved. (2) By performing ionic substitution in consideration of the ionic radius, lattice distortion can be effectively introduced and spontaneous polarization can be improved. (3) Since the {X3} O and the perovskite layer have a superlattice structure, the withstand voltage can be improved.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a two-dimensional layered perovskite structure of the present invention.

FIG. 2 is a diagram schematically showing a three-dimensional layered perovskite structure.

FIG. 3 is a block diagram showing an example of an apparatus for manufacturing a dielectric thin film having a perovskite structure.

FIG. 4 is a graph showing a measurement example of RHEED intensity and X-ray diffraction intensity in an example having a superlattice structure.

FIG. 5 is a graph showing a comparison between electrical characteristics of a superlattice perovskite film and a SrO-excess perovskite film.

FIG. 6 is a diagram showing a main configuration of a dielectric memory element to which the present invention is applied.

[Explanation of symbols]

 10, 50: substrate 12: perovskite layer 14: {X3} O layer 16: dielectric thin film 52: oxide (buffer layer) 54: conductive oxide (lower electrode) 56: perovskite film 58: conductive oxide ( Upper electrode) 100 vacuum chamber 102 target 104 laser light source 106 laser beam 108 optical system 110 exhaust device 112 infrared heater 114 film thickness monitor 116 plume 120 gun 122 screen 124 high-sensitivity camera 126 … Exhaust device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 21/203 H01L 21/203 Z S 21/316 Y 21/316 X H01G 4/06 102 27/04 H01L 27/04 C 21/822 27/10 444C 27/105 651 27/108 41/18 101B 21/8242 41/22 A 41/187 41/24 (72) Inventor Kentaro Morito 6-16 Ueno, Taito-ku, Tokyo No. 20 Taiyo Denki Co., Ltd. (72) Inventor Shoichi Sekiguchi 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd. (72) Inventor Masayuki Fujimoto 6-16 Ueno, Taito-ku, Tokyo No. 20 Taiyo Denki Co., Ltd.

Claims (17)

[Claims] 1. A method according to claim 1, wherein {X1} has an oxygen 12 coordination structure and {X1}.
And {X3} having a different coordination structure from Ca, Mg, Sr,
When {X2} composed of at least one element selected from Ba and Pb and having a six-coordinate oxygen structure is composed of at least one element selected from Ti and Zr, and “O” is oxygen {X1} {X2} O ₃ formed on a substrate having a similar crystal structure
(X3) O is inserted into a perovskite layer having the following composition to form a lattice strain due to lattice mismatch with the substrate. 2. The dielectric thin film according to claim 1, wherein the perovskite layer is divided into a plurality of layers by inserting the {X3} O. 3. The dielectric thin film according to claim 1, wherein substantially one layer of said {X3} O is inserted. 4. The dielectric thin film according to claim 1, wherein a rock salt structure layer is formed by inserting the {X3} O. 5. The dielectric thin film according to claim 1, wherein said perovskite layer and said {X3} O are alternately laminated to form a superlattice structure. 6. The method according to claim 6, wherein {X4} having an oxygen 12 coordination structure is Ca,
When {X5} is composed of at least one element selected from Mg, Sr, Ba and Pb, and {X5} is composed of an element different from {X4}, {X1} is represented by {X4} _1-m {X5} _m (however, m>
The dielectric thin film according to claim 1, wherein the dielectric thin film is represented by the following formula: 7. The dielectric thin film according to claim 6, wherein m is smaller than 0.5. 8. The dielectric thin film according to claim 1, wherein said {X3} has a composition containing more elements having a smaller ionic radius than said {X1}. 9. The method according to claim 1, wherein the perovskite layer and the {X3} O
9. The method of manufacturing a dielectric thin film according to claim 1, wherein the first and second targets are alternately grown on substrates having similar crystal structures. 10. {X1} having an oxygen 12 coordination structure, and {X1
{X3} having a different coordination structure from Ca, Mg, S
{X2} composed of at least one element selected from r, Ba and Pb and having an oxygen six-coordinate structure is composed of at least one element selected from Ti and Zr, and {X} is represented by {X
A dielectric thin film having a composition of {X} _m {X2} O _{2 + m} (where m> 1), where “O” is oxygen, as the sum of the constituent elements of {1} and {X3}, {X1} {X2} O ₃ formed on a substrate similar to
A dielectric thin film comprising: a perovskite layer having the following composition; and {X3} O inserted into the perovskite layer, and having a lattice distortion due to lattice mismatch with the substrate. 11. The dielectric thin film according to claim 10, wherein a rock salt structure layer is formed by inserting the {X3} O. 12. XC having an oxygen 12 coordination structure is represented by C
at least one selected from a, Mg, Sr, Ba, Pb
When {X5} is composed of an element different from {X4}, {X1} is represented by {X4} _1−m {X5} _m (where m> 0) 10. The method according to claim 10, wherein
2. The dielectric thin film according to 1. 13. The dielectric thin film according to claim 12, wherein m is less than 0.5. 14. The dielectric thin film according to claim 10, wherein the {X3} has a composition containing a larger number of elements having a smaller ionic radius than the {X1}. 15. The perovskite layer and {X3} O
Is formed on a substrate having a similar crystal structure by using a target having a composition of {X} _m {X2} O _{2+ m} (where m> 1). The method for producing a dielectric thin film according to any one of the above. 16. {X1} having an oxygen 12 coordination structure, {X1
{X3} having a different coordination structure from Ca, Mg, S
{X2} composed of at least one element selected from r, Ba, and Pb and having a six-coordinate oxygen structure is composed of at least one element selected from Ti and Zr, and “O” is replaced with oxygen. A dielectric thin film characterized in that {X3} O is inserted two-dimensionally or three-dimensionally into a perovskite layer having a composition of {X1} {X2} O ₃ . 17. An electronic component using the dielectric thin film according to any one of claims 1 to 8, 10 to 14, and 16.