JP2000188377A - Ferroelectric thin-film element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric thin-film element, having an oxide ferroelectric thin film which is constituted of a simple thin film stack as much as possible and which is highly aligned, especially the oxide ferroelectric thin film of a Pb system perovskite on a Si single-crystal substrate and to provide the manufacture method. SOLUTION: A ferroelectric thin-film element contains a Si substrate 66, a TiN thin film 64, which is formed on the Si substrate and in which a part of Ti is substituted for Al, and the ferroelectric thin film 62 of an oxide, which is formed on the TiN thin film and has perovskite structure. The Al substitution quantity of a Ti site in the TiN thin film is 1%-30%, when it is converted into Al atoms and oxygen content in the TiN thin film is not more than 5%, when it is converted into oxygen atoms.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric thin film element and a method of manufacturing the same, and more particularly, for example, to a DRAM or a Ferroelectric RAM (hereinafter referred to as FeRAM).
The present invention relates to a ferroelectric thin film element applicable to a capacitor, a pyroelectric element, a microactuator, a thin film capacitor, a small piezoelectric element, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, BaTiO ₃ , S
rTiO ₃ , (Ba, Sr) TiO ₃ , PbTiO ₃ ,
(Pb, La) TiO ₃ , PZT, PLZT, and P
The formation of thin films of lead-based and lead-free perovskite compounds such as b (Mg, Nb) O ₃ has been actively studied. In particular, if a Pb-based perovskite compound such as PZT or PLZT having a large remanent polarization can be epitaxially grown, spontaneous polarization can be aligned in one direction, and a larger polarization value and switching characteristics can be obtained. Since the application as a medium is dramatically expanding, the development of such a technology is eagerly desired.

However, in applications where the spontaneous polarization is aligned in one direction in the film thickness direction as described above, a ferroelectric thin film is sandwiched between conductive layers (electrode layers) on a Si substrate, that is, a so-called metal-ferroelectric-metal ( MFM) structure is required. However, conventionally, it has been difficult to obtain a triaxially oriented ferroelectric oxide thin film having good crystallinity for the following reasons.

[0004] First, as a conductor, Ag,
When a metal film such as Au is used, the interface between the ferroelectric and the metal film is oxidized during the growth of the ferroelectric oxide thin film, or interdiffusion occurs with the underlying Si.

Secondly, a method using Pt as a metal film can be considered. Pt is epitaxially grown on an oxide single crystal substrate such as MgO or SrTiO _3.
Direct epitaxial growth on the substrate has not been realized.

Third, (La, Sr) as a conductive thin film
There is also a method using an oxide such as CoO ₃ (hereinafter abbreviated as LSCO). In this case, for example, PLZT / LS
It was necessary to insert another layer between the Si substrate and the LSCO layer, such as CO / BiTO / YSZ / Si, and it was difficult to enhance the epitaxial property of the uppermost ferroelectric layer. [Here, BiTO is Bi ₄ Ti ₃ O ₁₂
YSZ is Zr with Y (yttrium) added.
O is a _two abbreviations. ]

Fourth, Koinuma et al. Have only succeeded in epitaxially growing a PZT thin film which is a Pb-based perovskite oxide ferroelectric on Si [Jpn.
J. Appl. Phys. Vol 35 (1996), L
574]. Koinuma et al. Use laser deposition [Pulsed L
[Assembly Deposition (hereinafter abbreviated to PLD)]] method on a Si substrate at a low pressure (10 ⁻⁷ Torr).
In the following), TiN is epitaxially grown, and S
rTiO ₃ (hereinafter abbreviated as STO) is formed as a buffer layer, and a PZT thin film is epitaxially grown thereon. At this time, the STO layer on the TiN film is
^-5 Torr (at 550 ° C.) in a vacuum, and 0.1 Torr / O ₂ which is a PZT layer production atmosphere
It is produced at a pressure extremely different from that during the flow (at 450 ° C.). This is based on the fact that the STO generates a perovskite phase even under a low oxygen partial pressure as described above,
This is to prevent oxidation of the TiN layer. However, in this technique, a pressure (high vacuum) of 10 ⁻⁷ Torr or less is required for epitaxially growing a TiN thin film on a Si substrate, and the cost of a vacuum system such as a film forming chamber becomes extremely high. If STO, which is a paraelectric substance at normal temperature, is not inserted as a buffer layer between TiN and PZT, P
There is a problem that ZT cannot be highly oriented.

[0008]

As described above, an electrode layer serving as a base is epitaxially grown on a Si single crystal substrate, and a ferroelectric thin film of an oxide having a perovskite structure, especially a Pb-based perovskite oxide, is formed immediately above the electrode layer. Forming a ferroelectric in a highly oriented (one or more axis) state could not be easily realized by conventional techniques.

[0009] Therefore, an object of the present invention is to provide a highly oriented oxide ferroelectric thin film, particularly a Pb-based perovskite oxide ferroelectric thin film, with the simplest possible thin film lamination structure on a Si single crystal substrate. It is an object of the present invention to provide a ferroelectric thin film element having the same and a method for manufacturing the same.

In order to achieve the above object, to form a Pb-based perovskite compound having good crystallinity,
It is important that oxygen deficiency is not caused by producing under high oxygen partial pressure conditions. However, under a high oxygen partial pressure, TiN in which 1 to 3% of Ti is replaced by Al (hereinafter abbreviated as TAN) has insufficient oxidation resistance.
Oxidation of the N surface occurs. In this case, the function as a buffer layer for epitaxial growth is lost, and P
The b-type perovskite compound cannot be epitaxially grown. Furthermore, TiO formed by oxidizing TiN
_{Since the two} layers have a lower dielectric constant than PZT, there is a problem that no voltage is applied to the PZT layer when an element is formed.

[0011] Therefore, another object of the present invention is to provide a ferroelectric element having a base electrode layer capable of forming a highly oriented Pb-based perovskite oxide ferroelectric thin film on a single crystal substrate by a simple thin film structure and a manufacturing process. An object of the present invention is to provide a dielectric thin film element.

[0012]

According to the present invention, there is provided a ferroelectric thin film element formed on a Si substrate, a TiN thin film formed on the Si substrate and partially replacing Ti with Al, and a TiN thin film. A ferroelectric thin film element including a ferroelectric thin film of an oxide having a perovskite structure, wherein an Al substitution amount of Ti sites in the TiN thin film is 1% or more and 30% or less in terms of Al atoms, and The oxygen content in the TiN thin film is not more than 5% in terms of oxygen atoms,
This is a ferroelectric thin film element. In the ferroelectric thin film element according to the present invention, the TiN thin film in which a part of Ti is replaced by Al is epitaxially grown, and the ferroelectric thin film is oriented and grown. Further, in the ferroelectric thin film element according to the present invention, the ferroelectric thin film is preferably a thin film of a Pb-based perovskite compound, for example, a general formula ABO ₃ (where A is a constituent element other than Pb or Pb other than Pb or Pb) Containing at least La and containing B, Ti, Z
It is preferably a thin film of a Pb-based perovskite compound represented by at least one of r, Mg, and Nb). In the ferroelectric thin film element according to the present invention, the ferroelectric thin film is preferably oriented and grown by epitaxial growth. Further, a Pb-based perovskite compound thin film as a ferroelectric thin film is formed on a Si substrate. It is desirable that the epitaxial growth is performed with the c-axis oriented vertically in order to utilize the characteristics in the thickness direction of the thin film as device characteristics. Further, in the ferroelectric thin-film element according to the present invention, T
The iN thin film can be formed by a sputtering method, a reactive evaporation method, or the like, but is preferably formed by a laser evaporation method because the degree of vacuum can be independently controlled. Further, the ferroelectric thin film is preferably formed by a chemical vapor deposition method (CVD method).

Further, the method of manufacturing a ferroelectric thin film element according to the present invention includes the steps of epitaxially growing a TiN thin film in which a part of Ti is replaced by Al on a Si substrate;
Orientating and growing a ferroelectric thin film of an oxide having a perovskite structure on a TiN thin film, wherein the Al substitution amount of Ti sites in the TiN thin film is changed to Al atoms. Converted from 1% to 30%
Or less, and wherein the oxygen content in the TiN thin film is 5% or less in terms of oxygen atoms. Further, in the method for manufacturing a ferroelectric thin film element according to the present invention, the ferroelectric thin film is preferably a thin film of a Pb-based perovskite compound, for example, a general formula ABO ₃ (where Pb or Ab is a constituent element of A). At least La is contained in addition to Pb, and Ti,
It is preferably a thin film of a Pb-based perovskite compound represented by at least one of Zr, Mg, and Nb). Further, in the method for manufacturing a ferroelectric thin film element according to the present invention, it is preferable that the ferroelectric thin film is highly oriented by epitaxial growth. Further, it is desirable that the Pb-based perovskite compound thin film as the ferroelectric thin film is epitaxially grown with the c-axis oriented perpendicular to the Si substrate in order to utilize the characteristics in the thickness direction of the thin film as device characteristics. . In the method for manufacturing a ferroelectric thin film element according to the present invention, the TiN thin film in which part of Ti is replaced by Al is formed by a laser deposition method using a target material in which part of Ti is replaced by Al. It is preferably formed at a pressure of 10 ⁻⁶ Torr or less. Further, as for the target, it is also possible to perform laser deposition while switching between TiN and AlN at a predetermined ratio by using different targets. Also,
In the method of manufacturing a ferroelectric thin film element according to the present invention,
The ferroelectric thin film is preferably formed by a chemical vapor deposition method. In particular, in order to facilitate the growth of a ferroelectric thin film having a Pb-based perovskite structure with good crystallinity, M
It is desirable to form by OCVD. Further, in the method of manufacturing a ferroelectric thin film element according to the present invention, the method of manufacturing
After the thin film is formed on the Si substrate, until the ferroelectric thin film is formed thereon, the Ti
When the N thin film is heated to a temperature of 300 ° C. or higher, the partial pressure of oxygen in the vacuum chamber at least in the vicinity of the TiN thin film is 1 × 10 ⁻⁵ Torr or less, and the partial pressure of water is 5 × 10 ⁵ Torr. ^Under the condition of a pressure of ^-5 Torr or less, the Ti
It is preferable to leave the N thin film. This means that the oxygen partial pressure is greater than 1 × 10 ⁻⁵ Torr and the water partial pressure is 5 × 1 Torr.
This is because, under conditions greater than 0 ^-5 Torr, there is a disadvantage that the oxidation reaction of TAN proceeds rapidly. Further, in the method for manufacturing a ferroelectric thin film element according to the present invention, the oxygen partial pressure excluding an amount necessary for forming a thin film of a Pb-based perovskite compound without causing oxygen deficiency is:
1 × at least in the vicinity of the TiN thin film in a vacuum chamber.
Pressure of 10 ⁻⁵ Torr or less and partial pressure of water of 5 × 10
^Under a condition of a pressure of ^-5 Torr or less, a first Pb-based perovskite compound thin film is formed on the TiN thin film by a chemical vapor deposition method, and a Pb-based perovskite compound thin film is formed thereon so as not to cause oxygen deficiency. The second Pb-based perovskite compound thin film is chemically treated under the condition that the oxygen partial pressure excluding the amount necessary for forming the thin film is at least 1 × 10 ⁻¹ Torr near the TiN thin film in the vacuum chamber. It is preferably formed by a vapor deposition method. This is because oxygen deficiency hardly occurs at a pressure of 1 × 10 ⁻¹ Torr or more. Further, in the method for manufacturing a ferroelectric thin film element according to the present invention, it is preferable that the first Pb-based perovskite compound thin film is formed in a thickness of 5 nm to 50 nm. This is because if it is smaller than 5 nm, the TAN is oxidized and the Pb-based perovskite compound does not grow epitaxially, and if it is larger than 50 nm, oxygen deficiency of the Pb-based perovskite compound tends to occur.

The present inventors have developed a part of TiN site of TiN.
Is replaced by Al, an absolute pressure of 10^-7Torr
TAN on Si substrate even under low pressure (high vacuum)
It has been found that the epitaxial growth is good. Tisa
The substitution amount for replacing part of the site with Al
If it is less than 1%, the effect of improving oxidation resistance is poor.
If it exceeds 30%, the conductivity of TAN is significantly reduced.
Therefore, a substitution range of 1% or more and 30% or less is appropriate.
However, when the oxygen content in the TAN thin film exceeds 5%,
Even if part of the Ti site of TiN is replaced by Al
Oxidation resistance and good epitaxy as expected on Si substrates
Char growth is not obtained. Therefore, the acid in the TAN thin film
The oxygen content can be reduced to 5% or less by substituting oxygen atoms.
Preferably, more preferably less than 1%
No. To keep the oxygen content in the TAN film below 5%
, At the time of TAN production ^-6Low pressure below Torr
(Degree of vacuum) is required, but this is part of the Ti site
In the case of TiN in which is not replaced by Al^-7To
One order of magnitude higher pressure than required pressure below rr
Power. That is, according to the present invention, the pressure
Power as a barrier metal layer on the Si single crystal substrate.
Extreme layer (TAN) can be epitaxially grown
You. The thickness of the TAN film is not particularly limited
It is not, but the specific resistance is about 1 or 2 digits
Since it is large, the thickness is in the range of about 100 nm to 10 μm.
Is desirable. Then, the TAN is used as an electrode layer
Easily used just above the TAN
It is possible to make the body thin film highly oriented (more than one axis orientation)
Become. Therefore, according to the present invention, on a Si single crystal substrate
Highly oriented oxides with relatively simple thin film lamination structure
Ferroelectric thin film, especially Pb-based perovskite oxide ferroelectric
A ferroelectric thin-film element having a body thin film can be obtained.

The objects, other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the drawings.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

EXAMPLE On a Si single crystal substrate from which a natural oxide film was removed,
According to each Example and Comparative Example shown in detail below, TAN
A thin film and an oxide ferroelectric thin film were formed in this order to produce an oriented ferroelectric thin film element. Thereafter, a 0.5 μm Au layer was formed on the oxide ferroelectric thin film by a vacuum evaporation method using a mask.
An upper electrode was formed, and electrical characteristics as a ferroelectric thin film element were evaluated.

FIG. 1 is an illustrative view showing one example of a PLD device used for forming a TAN thin film, a PLT thin film, or a BSTO thin film in the following Examples and Comparative Examples.
Here, this conventionally known PLD (Pulsed Laser)
An outline of the (r Deposition) apparatus 10 will be described. This PLD device 10 includes a vacuum container 12.
Gas is introduced into the vacuum vessel 12 from a gas introduction pipe 14, and unnecessary gas is exhausted from an exhaust pipe 16. In the vacuum vessel 12, a Si single crystal substrate (hereinafter, simply referred to as a substrate) S is placed on a substrate heater 18. The target T is held by the target holder 20 obliquely above the substrate S. The target holder 20 includes a driving manipulator 22 for adjusting the position of the target T.
It is supported by. Excimer laser beam L is applied to vacuum vessel 1
After being condensed from outside by a laser condensing lens 24, the light passes through a synthetic quartz window 26 and irradiates the target T. Then, a TiN thin film is formed on the substrate S.

FIG. 2 is an illustrative view showing one example of an MOCVD apparatus used for forming a PZT thin film in the following Examples and Comparative Examples. Here, the conventionally known M
The outline of the OCVD apparatus 30 will be described. This MOC
The VD device 30 includes a vacuum container 32. The substrate S is placed on the substrate heater 34 in the vacuum vessel 32.
A turbo molecular pump 364 is connected to the vacuum vessel 32 via a valve 311.
Is connected to a rotary pump 363. Further, a mechanical booster pump 362 is connected to the vacuum vessel 32 via a variable valve 312, and the mechanical booster pump 362 is connected to a rotary pump 361. Further, a raw material gas is introduced into the vacuum vessel 32 from a gas blowing nozzle 38. Gas blowing nozzle 3
A gas mixer 40 is connected to 8. When forming a PZT thin film, four paths are connected to the gas mixer 40 via variable valves, respectively. O ₂ gas is introduced from the first path via a mass flow controller (hereinafter abbreviated as MFC) 42. From the second path, Pb vaporized in the solid vaporizer 50 is introduced by Ar gas as a carrier gas sent through the MFC 44. From the third path, Zr vaporized by the liquid vaporizer 52 is introduced by Ar gas as a carrier gas sent through the MFC 46. From the fourth path, Ti vaporized by the liquid vaporizer 54 is introduced by Ar gas as a carrier gas sent through the MFC 48. The gases introduced from these four paths are mixed by the gas mixer 40, and cause a thermal decomposition and a combustion reaction on the substrate S to grow a PZT thin film.

(Embodiment 1) 2 inches of S as a Si substrate
i (100) was used. This Si (100) substrate was subjected to ultrasonic cleaning in an organic solvent such as acetone and ethanol, and then immersed in a 10% HF solution to remove an oxide film on the surface of the Si substrate, and then subjected to an experiment. Thereafter, the PL shown in FIG.
In a vacuum (about 10 ⁻⁶ Torr), substrate temperature: 550 ° C. to 650 ° C., laser repetition frequency:
5 to 10 Hz, laser energy density: 4.5 J / cm ²
Under the condition of (KrF), a TAN thin film (Ti _0.9 Al _0.1 N) in which a part of a Ti site of about 500 nm is substituted with Al by 10% in terms of Al atoms is epitaxially grown on a Si single crystal substrate by a laser vapor deposition method. I let it. The target used to obtain the TAN thin film was (Ti _0.9 Al
_0.1 ) A TAN sintered body represented by a composition formula of N was used. The relative density of the sintered body is at least 90%, and preferably at least 95%. The oxygen content in the obtained TAN thin film was measured by Auger electron spectroscopy (Auger elect).
RON spectroscopy (AES) was 1% or less in terms of oxygen atoms. Further, the MOCVD apparatus 30 shown in FIG.
At a total pressure of 10 Torr and a substrate temperature of 700 ° C.
Pb (Zr _0.52 Ti _0.48 ) O with a thickness of 00 to 600 nm
₃ [PZT] thin films were grown epitaxially by chemical vapor deposition. The precursors of Pb, Zr and Ti are Pb (DPM) ₂ , Zr (O-t-C ₄
H _{9) 4,} was used _{Ti (O-i- C 3 H} 7) 4. PZT
Table 1 shows detailed conditions for forming the thin film.

[0020]

[Table 1]

FIG. 3 shows "apparent oxygen partial pressure" in the PZT film forming process. In the film formation process by MOCVD, a precursor that contributes to film formation is completely oxidized,
In addition, a large amount of oxygen is consumed to form PZT without causing oxygen defects. FIG. 4 shows changes in the partial pressure of oxygen excluding the consumed oxygen (hereinafter, referred to as “partial pressure of excess oxygen”) and the partial pressure of water. In the temperature raising step, the vacuum vessel is evacuated by the turbo molecular pump 364, the oxygen partial pressure is 2 × 10 ⁻⁷ Torr, and the water partial pressure is 1 × 10 ⁻⁶ Torr.
It is kept in. In the heating step, the precursor and oxygen are not supplied to the vacuum vessel. After the substrate temperature reaches 700 ° C., the supply of the precursor is started by opening the variable valves of the respective supply paths, and at the same time, the exhaust is switched to the exhaust by the booster pump 362. Then, the PZT film is formed for one minute while the oxygen flow rate is controlled and supplied by the mass flow controller 42 so that the “partial pressure of excess oxygen” in the vacuum vessel becomes 5 × 10 ⁻⁶ Torr. The thickness of the first PZT thin film grown during this time is about 40 nm. After one minute, the mass flow controller 42 adjusts the oxygen flow rate such that the “partial pressure of excess oxygen” becomes 1 Torr. At this time, the pressure in the vacuum vessel 32 is
12 adjusts to 10 Torr.

FIG. 5 shows a cross-sectional structure of the ferroelectric thin film element manufactured in the first embodiment. In this ferroelectric thin film element, a TAN film 64 is formed on a Si substrate 66, a first PZT thin film 62 is formed thereon, and a second PZT thin film 60 is further formed thereon. The first PZT thin film 62 is a PZT thin film formed at a low oxygen partial pressure,
The second PZT thin film 60 is made of a P film formed at a high oxygen partial pressure.
It is a ZT thin film. FIG. 6 is an XRD pattern of the PZT thin film. In the figures, a. u. Indicates an arbitrary unit. FIG. 6 shows that the perovskite PZT is c-axis oriented. FIG. 7 is a pole figure of the PZT thin film. As shown in FIG. 7, it is understood that the PZT thin film is epitaxially grown and highly oriented because of the four-fold symmetry. FIG. 8 shows the PE hysteresis characteristics of the PZT thin film. Furthermore, as shown in Table 2, the evaluation results of the electrical characteristics of the PZT thin film show that the PZT thin film of Example 1 has excellent electrical characteristics.

[0023]

[Table 2] In Table 2, Tan δ and ε _r are 1 kHz, 0.
It is a measured value at 1V.

Note that Si (100) is used as the substrate.
Without limitation, Si (111), Si (110), etc.
May be used. Also, the miscut angle of the single crystal substrate
Can be used if it is 5% or less. Furthermore, MgO,
SrTiO_Three, MgAl_TwoO _ThreeSingle crystal such as
May be used. The TAN thin film is made of KrF by PLD method.
ArF excimer is manufactured using excimer laser.
It is also possible with a laser, other electron beam evaporation methods,
rf sputtering method, DC sputtering method, ion
Beam sputtering, ECR sputtering, etc.
It is also possible to produce with ion beam, laser
-Crystallinity by assisting with the beam
Can also be improved. Furthermore, PZT film formation
The method is not limited to the thermal MOCVD, and the plasma CV
D, laser CVD, laser abrasion method, spa
A sputtering method, a vapor deposition method, an MBE method, or the like may be used.

Comparative Example 1 As in Example 1, Si (1
00) A TAN thin film was epitaxially grown on the substrate by the PLD device 10. And MOC on TAN thin film
By the VD method, the substrate temperature is 700 ° C., 400 to 600 nm
A PZT thin film having a thickness of 1 was epitaxially grown. PZ
FIG. 9 shows changes in the apparent partial pressure of oxygen and the partial pressure of water in the T thin film production process. FIG. 10 shows changes in the partial pressure of excess oxygen and the partial pressure of water. In the temperature raising step and the film forming step, the vacuum vessel 32 is evacuated by the booster pump 362. "Partial pressure of excess oxygen" in the heating process
Is 1 × 10 ⁻³ Torr. After the substrate temperature reaches 700 ° C., supply of oxygen and a precursor is started. The oxygen supply amount is controlled by the mass flow controller 42 so that the “partial pressure of excess oxygen” becomes 5 × 10 ⁻⁶ Torr.

Comparative Example 2 As in Comparative Example 1, Si (1
00) A TAN thin film was epitaxially grown on the substrate by the PLD device 10. And MOC on TAN thin film
By the VD method, the substrate temperature is 700 ° C., 400 to 600 nm
A PZT thin film having a thickness of 1 was epitaxially grown. PZ
FIG. 11 shows changes in the apparent partial pressure of oxygen and the partial pressure of water in the T thin film production process. FIG. 12 shows changes in the partial pressure of excess oxygen and the partial pressure of water. In the temperature raising step, the vacuum vessel 32 is evacuated by the turbo molecular pump 364,
The “partial pressure of excess oxygen” is 2 × 10 ⁻⁷ Torr, and the partial pressure of water is 1 × 10 ⁻⁶ Torr. In the film forming process, the vacuum chamber 32 is evacuated by the booster pump 362, and the oxygen supply amount is controlled by the mass flow controller 42 so that the "partial pressure of excess oxygen" becomes 6 Torr.

FIG. 13 is an illustrative view showing a cross-sectional structure of a ferroelectric thin film element manufactured according to Comparative Examples 1 and 2. The TAN film 64 on the Si substrate 66 and the P
An oxidized TAN film 68 is formed at the interface with the ZT thin film 60. FIG. 14 is an XRD pattern of the PZT thin film manufactured in Comparative Example 1. As can be seen from FIG.
Although the PZT thin film grows in an oriented manner, the diffraction intensity is very weak. Similarly, FIG. 15 shows the PZT prepared in Comparative Example 2.
It is an XRD pattern of a thin film. As can be seen from FIG. 15, this PZT thin film has a perovskite structure, but has not been oriented and grown. FIG. 16 shows the P produced by Comparative Example 1.
It is a PE hysteresis characteristic of a ZT thin film. Since the crystallinity is poor, the remanent polarization Pr is small, and the coercive voltage is large due to the presence of an oxide layer of TAN. Table 2 also shows the results of evaluating the electrical characteristics of the PZT thin film element obtained in Comparative Example 1. As shown in Table 2, Comparative Example 1 is inferior in electrical characteristics to Example 1.

(Example 2) In the same manner as in Example 1, a TAN thin film (Ti _0.7 Al
_0.3N ) was epitaxially grown. On this TAN thin film, 5 Torr (O ₂ atmosphere), substrate temperature: 500 ° C., laser repetition frequency: 5 Hz, by PLD method
Laser energy density: PLT thin film (Pb _0.9 L) of about 500 to 800 nm under the condition of 4.5 J / cm ² (KrF)
a _0.1 TiO ₃ ) was epitaxially grown. PLT
The target used to obtain the thin film was Pb _0.9 La
A ceramic sintered body target having a composition of _0.1 TiO ₃ was used. FIG. 17 is a diagram showing an XRD pattern of the obtained epitaxial PLT thin film. From these results, by using the method of manufacturing a ferroelectric thin film according to the present invention,
It can be seen that the PLT thin film can also be oriented and grown on a Si substrate by epitaxial growth.

(Embodiment 3) As in Embodiment 1, a Si substrate
Part of Ti site is Al atom by PLD method.
TAN thin film (Ti_0.99Al_0.01
N) was epitaxially grown. On this TAN thin film
And 10% by the PLD method.^-FourTorr, substrate temperature: 60
0 ° C, laser repetition frequency: 5Hz, laser energy
Lugi density: 4.5 J / cm^Two (KrF) about 50
BSTO thin film of 0 to 800 nm (Ba _0.7 Sr_0.3 Ti
O_Three ) Was epitaxially grown. Obtain BSTO thin film
The target used for this was Ba_0.7 Sr_0.3 TiO
_Three A ceramic sintered body target of the composition was used. Figure
18 is the XRD of the obtained epitaxial BSTO thin film.
It is a figure showing a pattern. From this result, according to the present invention
By using the method of manufacturing a ferroelectric thin film, BSTO
Epitaxial growth on Si substrate for thin films
It can be seen that oriented growth is possible.

Comparative Example 3 In the same manner as in Example 1, Si (1
00) On the substrate by PLD method, about 10 ⁻⁵ Torr at a higher pressure than in Example 1, substrate temperature: 550 to 65
0 ° C., laser repetition frequency: 5 Hz, laser energy density: about 10 J / cm ² (KrF)
A TAN thin film (Ti _0.9 Al _0.1 N) of 0 to 500 nm was epitaxially grown. TAN obtained by this
When the oxygen content in the thin film was measured by AES, it was about 10% in terms of oxygen atoms. On this TAN thin film,
By MOCVD, under the same conditions as those shown in Table 1, total pressure: 10 Torr, substrate temperature: 600 ° C., 30
Pb (Zr _0.52 Ti _0.48 ) O ₃ having a thickness of 0 to 600 nm
[PZT] A thin film was grown.

FIG. 19 shows an XRD pattern of the PZT thin film obtained in Comparative Example 3. From FIG. 19, it can be seen that although the PZT thin film becomes a perovskite phase, it does not tend to be oriented in a specific axis, and is not epitaxially grown. Table 2 also shows the results of evaluating the electrical characteristics of the PZT thin film element obtained in Comparative Example 3. As shown in Table 2, Comparative Example 3 is inferior in electrical characteristics to Example 1.

[0032]

According to the present invention, TiN (TA) as a barrier metal layer is formed on single-crystal Si at a higher pressure than in the prior art.
N) The thin film can be epitaxially grown, and the epitaxial growth of the perovskite oxide ferroelectric on single crystal Si, which has been extremely difficult until now, can be relatively easily performed. Therefore, Ti on single crystal Si
A perovskite oxide ferroelectric thin film directly above the N thin film,
In particular, it is possible to obtain a ferroelectric thin film element in which a ferroelectric thin film of a Pb-based perovskite oxide is grown while being highly oriented. Further, according to the present invention, the conventional apparatus can be used as it is without changing the thin film structure such as multi-layering and simply changing the process. Can be obtained. Therefore, it is extremely useful industrially. Further, such a high-quality epitaxial ferroelectric thin film has very few crystal defects, and can exhibit the original characteristics of the material itself. The ferroelectric thin film device obtained by the present invention is expected to be applied not only to DRAMs and FeRAMs, but also to other pyroelectric devices, microactuators, thin film capacitors, and small piezoelectric devices.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one example of a PLD device used for forming a TAN thin film in Examples and Comparative Examples of the present invention.

FIG. 2 is an illustrative view showing one example of an MOCVD apparatus used for producing a PZT thin film in Examples and Comparative Examples of the present invention.

FIG. 3 is a diagram illustrating an apparent partial pressure of oxygen and a partial pressure of water during a PZT film forming process in Example 1.

FIG. 4 is a diagram showing a partial pressure of excess oxygen and a partial pressure of water during a PZT film forming process in Example 1.

FIG. 5 is an illustrative view showing a cross-sectional structure of a ferroelectric thin-film element manufactured in Example 1;

FIG. 6 is an XRD pattern diagram of a PZT thin film of the ferroelectric thin film element manufactured in Example 1.

FIG. 7 is a pole figure of a PZT thin film of the ferroelectric thin film element manufactured in Example 1.

FIG. 8 is a PE hysteresis loop diagram of a PZT thin film of the ferroelectric thin film element manufactured in Example 1.

FIG. 9 is a diagram showing an apparent partial pressure of oxygen and a partial pressure of water during a PZT film forming process in Comparative Example 1.

FIG. 10 is a diagram showing a partial pressure of excess oxygen and a partial pressure of water during a PZT film forming process in Comparative Example 1.

11 is a diagram showing an apparent partial pressure of oxygen and a partial pressure of water during a PZT film forming process in Comparative Example 2. FIG.

FIG. 12 is a diagram showing a partial pressure of excess oxygen and a partial pressure of water during a PZT film forming process in Comparative Example 2.

FIG. 13 is an illustrative view of a cross-sectional structure of a ferroelectric thin-film element manufactured in Comparative Examples 1 and 2.

FIG. 14 is an XRD pattern diagram of a PZT thin film of the ferroelectric thin film element manufactured in Comparative Example 1.

FIG. 15 is an XRD pattern diagram of a PZT thin film of a ferroelectric thin film element manufactured in Comparative Example 2.

FIG. 16 is a PE hysteresis loop diagram of a PZT thin film of a ferroelectric thin film element manufactured in Comparative Example 1.

FIG. 17 is an XRD pattern diagram of a PLT thin film of the ferroelectric thin film element manufactured in Example 2.

FIG. 18 is an XRD pattern diagram of the BSTO thin film of the ferroelectric thin film element manufactured in Example 3.

FIG. 19 is an XRD pattern diagram of a PZT thin film of the ferroelectric thin film element manufactured in Comparative Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 PLD apparatus 12 Vacuum container 14 Gas introduction pipe 16 Exhaust port 18 Substrate heater 20 Target holder 22 Driving manipulator 24 Laser focusing lens 26 Synthetic quartz window 28 Plume 30 MOCVD apparatus 311 Valve 312 Variable valve 32 Vacuum container 34 Substrate Heater 361, 363 Vacuum pump (rotary pump) 362 Vacuum pump (mechanical booster pump) 364 Vacuum pump (turbo molecular pump) 38 Gas blowing nozzle 40 Gas mixer 42, 44, 46, 48 Mass flow controller 50 Solid vaporization 52,54 Liquid vaporizer S Substrate T Target L Excimer laser beam (beam line)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 27/10 451 H01L 37/02 21/8247 29/78 371 29/29/788 41/08 L 29/792 41 / 22 Z 37/02 41/09 41/22

Claims (16)

[Claims] 1. A ferroelectric material comprising: a Si substrate; a TiN thin film formed on the Si substrate in which a part of Ti is replaced with Al; and a ferroelectric thin film of an oxide having a perovskite structure formed on the TiN thin film. A dielectric thin film element, wherein an Al substitution amount of a Ti site in the TiN thin film is 1% or more and 30% or less in terms of Al atoms, and the TiN
A ferroelectric thin film element, characterized in that the oxygen content in the thin film is 5% or less in terms of oxygen atoms. 2. TiN in which part of the Ti is replaced by Al
2. The ferroelectric thin film element according to claim 1, wherein the thin film is grown epitaxially, and the ferroelectric thin film is grown by orientation. 3. The ferroelectric thin film element according to claim 1, wherein the ferroelectric thin film is a thin film of a Pb-based perovskite compound. 4. The ferroelectric thin film has a general formula of ABO ₃
(However, A contains at least La in addition to Pb or Pb as a constituent element of A, and Ti, Zr, M as a constituent element of B.
g and Nb).
3. The ferroelectric thin film element according to claim 1, wherein the ferroelectric thin film element is a thin film of a perovskite compound. 5. The ferroelectric thin film device according to claim 1, wherein said ferroelectric thin film is grown epitaxially. 6. TiN in which part of the Ti is replaced by Al
The ferroelectric thin film element according to claim 1, wherein the thin film is formed by a laser deposition method. 7. The ferroelectric thin film element according to claim 1, wherein said ferroelectric thin film is formed by a chemical vapor deposition method. 8. A step of epitaxially growing a TiN thin film in which a part of Ti is replaced by Al on a Si substrate, and a step of aligning and growing a ferroelectric thin film of an oxide having a perovskite structure on the TiN thin film. A method for manufacturing a ferroelectric thin film element, wherein an Al substitution amount of a Ti site in the TiN thin film is 1% or more and 30% or less in terms of Al atoms, and the TiN
A method for manufacturing a ferroelectric thin film element, wherein the oxygen content in the thin film is 5% or less in terms of oxygen atoms. 9. The method according to claim 8, wherein the ferroelectric thin film is a Pb-based perovskite compound thin film. 10. The ferroelectric thin film has a general formula of ABO ₃
(However, A contains at least La in addition to Pb or Pb as a constituent element of A, and Ti, Zr, M as a constituent element of B.
g and Nb).
The method for producing a ferroelectric thin film element according to claim 8, wherein the ferroelectric thin film element is a thin film of a perovskite compound. 11. The method for manufacturing a ferroelectric thin film device according to claim 8, wherein said ferroelectric thin film is epitaxially grown. 12. Ti obtained by substituting a part of the Ti with Al.
The N thin film according to claim 8, wherein the N thin film is formed at a pressure of 10 ⁻⁶ Torr or less by a laser deposition method using a target material in which a part of Ti is replaced by Al. A method for manufacturing a dielectric thin film element. 13. The method according to claim 8, wherein the ferroelectric thin film is formed by a chemical vapor deposition method. 14. The TiN thin film is formed on the Si substrate.
After the formation, the ferroelectric thin film is formed thereon.
The TiN thin film has a temperature of 300 ° C. or more during
When heated to at least the above T
Oxygen partial pressure in the vicinity of the iN thin film is 1 × 10^-FiveTorr or less
At a lower pressure and a partial pressure of water of 5 × 10 ^-FiveTorr or less
9. The TiN thin film is left under a condition of pressure.
14. The ferroelectric thin-film element according to claim 13
Manufacturing method. 15. A Pb-based perov without causing oxygen deficiency.
Excluding the amount required to form a thin film of the skyte compound
Oxygen partial pressure at least near the TiN thin film in the vacuum chamber
At 1 × 10^-FiveAt a pressure of less than Torr and water
Pressure is 5 × 10 ^-FiveUnder the condition of a pressure of Torr or less,
First Pb-based perovskite compound thin film on TiN thin film
A film is formed by chemical vapor deposition, and a Pb-based perovskite is formed on it so as not to cause oxygen deficiency.
Oxygen partial pressure excluding the amount required to form the compound thin film
At least in the vicinity of the TiN thin film in a vacuum chamber.
1 × 10^-1Under the condition that the pressure is equal to or higher than Torr, the second P
b-type perovskite compound thin film formed by chemical vapor deposition
15. The method according to claim 9, wherein:
A method for manufacturing a ferroelectric thin-film element according to any of the preceding claims. 16. The method according to claim 15, wherein the first Pb-based perovskite compound thin film is formed in a thickness range of 5 nm to 50 nm.