JP2000091533A - Ferroelectric thin-film element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a highly oriented perovskite oxide ferroelectric thin film with as feel multiple structure of layers as possible on an Si substrate. SOLUTION: This ferroelectric thin-film element is provided with a Si substrate, a TiN film formed on the Si substrate by being epitaxially grown for which a part of Ti is replaced with Al, an oxide conductive thin film formed on the TiN thin film by being grown epitaxially and an oxide ferroelectric thin film formed on the oxide conductive thin film by being oriented and grown and provided with a perovskite structure. In this case, the Al replacement amount of Ti site in the TiN thin film when converted is 1-30%, by being converted into Al atoms and an oxygen content in the TiN thin film if made equal to or less than 5% by being 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 device and a method of manufacturing the same, and more particularly, for example, to a DRAM.
The present invention relates to a ferroelectric thin film element which can be applied to capacitors for ferroelectric RAM (FeRAM), pyroelectric elements and microactuators, thin film capacitors and small piezoelectric elements, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, BaTiO3 has been deposited on a Si substrate._Three(After
Below, abbreviated as BTO), SrTiO _Three(Hereafter, STO
), (Ba, Sr) TiO_Three(Hereinafter BST
O), PbTiO_Three, (Pb, La) TiO
_Three(Hereinafter abbreviated as PLT), PZT, PLZT, P
b (Mg, Nb) O_Three(Hereinafter abbreviated as PMN)
Lead-free and lead-free perovskite compound thin film formation is flourishing
It is being studied. In particular, PZ with large remanent polarization
Epitaxy of Pb-based perovskite compounds such as T and PLZT
Spontaneous polarization in one direction
Higher polarization value and switching
Characteristics can be obtained.
The development of such technologies will be dramatically expanded in applications.
Is eagerly awaited.

[0003]

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.
A so-called metal-ferroelectric-metal (MFM) structure is required, and it is difficult to obtain a triaxially oriented ferroelectric oxide thin film having good crystallinity for the following reasons. In other words, when a metal film such as Ag or Au is used as a conductor on a Si substrate, the interface between the ferroelectric and the metal is oxidized during the growth of the ferroelectric oxide thin film, or the interface between the ferroelectric metal and the underlying Si is increased. Causes interdiffusion. Although a method using Pt as the metal film is conceivable, Pt epitaxially grows on an oxide single crystal substrate such as MgO or SrTiO _3, but direct epitaxial growth on a Si substrate has not been realized. (La, Sr) CoO ₃ [LSC
O] may be used, but in this case, for example, PLZT / LSCO / BiTO / YSZ / Si
Thus, it is necessary to insert two or more different layers between the Si substrate and the LSCO layer, and it has been difficult to enhance the epitaxial property of the uppermost ferroelectric layer. [Here, BiTO is an abbreviation for Bi ₄ Ti ₃ O ₁₂ and YSZ
Is an abbreviation for ZrO ₂ to which Y (yttrium) is added. ]

On the other hand, TiN is formed by an ion beam film forming method, a Pt thin film is formed thereon, and SrRuO ₃ (hereinafter abbreviated as SRO) is formed thereon as a buffer layer. Furthermore, (Ba, Sr) T
There is a method of epitaxially growing an iO ₃ [BSTO] thin film. However, in this method, BSTO / SRO
Because of the multi-layer structure of / Pt / TiN / Si, not only does the cost significantly increase, but also the crystallinity deteriorates as each thin film is stacked on the Si substrate. Further, SRO is considered to impart ferroelectricity to BSTO by applying strain to the BSTO layer by stress. However, there is no example in which a Pb-based perovskite compound has been successfully grown on SRO. is there.

[0005] Therefore, the main object of the present invention is S
An object of the present invention is to provide a ferroelectric thin film element in which a highly oriented perovskite oxide ferroelectric thin film is formed with a multilayer structure as small as possible on an i-substrate and a method for manufacturing the same.

[0006]

A ferroelectric thin film element according to the present invention comprises a Si substrate, a TiN thin film formed by epitaxial growth on a Si substrate, and a part of Ti is replaced by Al, and a thin film on the TiN thin film. An oxide conductive thin film formed by epitaxial growth on a ferroelectric thin film element including an oxide ferroelectric thin film having a perovskite structure formed by orientationally growing on the oxide conductive thin film, The Al substitution amount of the Ti site in the TiN thin film is 1 to 30% in terms of Al atoms,
And the oxygen content in the TiN thin film is 5 in terms of oxygen atoms.
% Or less, which is a ferroelectric thin film element. In the ferroelectric thin film element according to the present invention, the oxide conductive thin film is made of ABO ₃ (A is La, Sr, B
at least one selected from a, B is Ru, Co
At least one selected from the group consisting of), preferably a perovskite structure represented by
SrRuO ₃ , BaRuO ₃ , (Ba, Sr) RuO ₃
Alternatively, (La, Sr) CoO ₃ is desirable.
Further, in the ferroelectric thin film element according to the present invention, the oxide ferroelectric is preferably a Pb-based perovskite compound, particularly, for example, ABO ₃ (containing at least Pb or Pb and La as constituent elements of A site). , B, Ti, Zr, Mg, Nb
Perovskite-type oxide represented by the formula (1). Further, in the ferroelectric thin film element according to the present invention, it is preferable that the ferroelectric thin film is epitaxially grown.

The method of manufacturing a ferroelectric thin film element according to the present invention is directed to a method of manufacturing a semiconductor device in which Ti is obtained by partially replacing Ti with Al on a Si substrate.
A step of epitaxially growing an N thin film, a step of epitaxially growing an oxide conductive thin film having a perovskite structure on a TiN thin film, and a step of aligning and growing a ferroelectric thin film element having a perovskite structure on an oxide conductive thin film And a method of manufacturing a ferroelectric thin film element comprising:
A method for manufacturing a ferroelectric thin film element, wherein the content is 1 to 30% in terms of 1 atom and the oxygen content in the TiN thin film is 5% or less in terms of oxygen atoms. In the method for manufacturing a ferroelectric thin film element according to the present invention, the oxide conductive thin film is made of ABO ₃ (A is La, Sr,
At least one selected from Ba, B is Ru, C
It is preferable to adopt a perovskite structure represented by at least one selected from the group consisting of SrRuO ₃ , BaRuO ₃ ,
(Ba, Sr) RuO ₃ or (La, Sr) CoO ₃
It is desirable that Further, in the method for producing an oxide ferroelectric according to the present invention, the oxide ferroelectric is preferably a Pb-based perovskite compound, particularly, for example, ABO ₃ (at least Pb or Pb and La as constituent elements of the A site). And at least one selected from Ti, Zr, Mg, and Nb as a constituent element of the B site). Furthermore, in the method of manufacturing an oxide ferroelectric according to the present invention, the ferroelectric thin film is preferably grown epitaxially.

In the ferroelectric thin film element according to the present invention,
Two layers of TiN thin film and oxide conductive thin film (both conductive)
With only this, it is possible to form a ferroelectric thin film made of an oxide having a perovskite structure grown on a Si substrate. Therefore, there is no need to sandwich an unnecessary dielectric (insulator) layer between the lower electrode layer and the ferroelectric layer, and the number of stacked layers can be kept to a minimum. Further, in the ferroelectric thin film element according to the present invention, a part of Ti
Since the TiN thin film and the conductive oxide thin film substituted by 1 are epitaxially grown and the ferroelectric thin film is oriented and grown, it is possible to obtain good electric characteristics. In the present invention, the reason why the Al substitution amount of the Ti site in the TiN thin film is in the range of 1 to 30% in terms of Al atoms is that sufficient oxidation resistance is obtained when the Al substitution amount is less than 1%. This cannot be obtained, and when the amount of Al substitution exceeds 30%, the conductivity of TiN is significantly reduced.
Further, if the oxygen content in the TiN thin film exceeds 5%, the oxidation resistance is lowered and favorable epitaxial growth is hindered. Therefore, it is desirable that the oxygen content in the TiN thin film be 5% or less. In addition, it is necessary to use a very advanced process control technique to directly epitaxially grow a Pb-based perovskite oxide such as PZT on a TiN thin film. This is because a Pb-based perovskite-type ferroelectric oxide typified by PZT needs to be grown under a high oxygen partial pressure while satisfying the contradictory condition that oxidation of TiN must be suppressed. Because it does not become. However, a perovskite-type conductive oxide such as SRO easily has a perovskite structure even under a low oxygen partial pressure at which TiN is hardly oxidized, and has the same crystal structure as a base buffer layer of PZT, and has a similar lattice constant. Therefore, it is convenient to epitaxially grow a perovskite ferroelectric such as PZT. That is,
By epitaxially growing a perovskite-type conductive oxide such as SRO on TiN, it becomes relatively easy to achieve highly oriented growth of a Pb-based perovskite oxide ferroelectric represented by PZT. . Thus, in the present invention, a perovskite-type oxide conductive thin film such as SRO is epitaxially grown on TiN, and a Pb-based perovskite oxide ferroelectric represented by PZT is highly oriented and grown thereon.
Further, according to the present invention, a Pb-based perovskite-type oxide thin film having excellent characteristics as a ferroelectric thin film can be grown at a high degree of orientation (uniaxial orientation or more). Can be obtained. Also,
In the ferroelectric thin film element of the present invention, a Pb-based perovskite oxide as a ferroelectric thin film is represented by ABO _3.
Pb or Pb as a site constituent element and at least L
a, and as a constituent element of the B site, Ti,
It is desirable to include at least one selected from Zr, Mg, and Nb. This is due to the fact that a material configuration having a characteristic that the remanent polarization value, which is one index of ferroelectricity, is large and the electric field (coercive electric field) required for reversing the polarization is small is obtained.

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

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

EXAMPLE On a Si single crystal substrate from which a natural oxide film was removed,
In accordance with each of the examples and comparative examples described in detail below, a TiN thin film in which part of Ti was replaced with Al (hereinafter abbreviated as a TAN thin film), an SRO thin film, and a Pb-based perovskite ferroelectric thin film were formed in this order. Then, a ferroelectric thin-film device provided with an oriented ferroelectric oxide thin film was manufactured. Thereafter, an Au upper electrode having a diameter of 0.5 mm was formed on the Pb-based perovskite-type ferroelectric oxide thin film by a vacuum deposition method using a mask, and the electrical characteristics of the ferroelectric thin film element were evaluated.

FIG. 1 shows a conventional PLD used for forming a TAN thin film and the like in the following Examples and Comparative Examples.
FIG. 2 is an illustrative view showing one example of a (Pulsed Laser Deposition) apparatus. 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 TAN thin film or the like is formed on the substrate S.

FIG. 2 is a view showing a conventional known MZ used for forming a PZT thin film in the following Examples and Comparative Examples.
FIG. 2 is an illustrative view showing one example of an OCVD apparatus; This MOCV
The D device 30 includes a vacuum container 32. The substrate S is placed on the substrate heater 34 in the vacuum vessel 32. A vacuum pump (mechanical booster pump) 36 is connected to the vacuum container 32 via a variable valve. Further, a raw material gas is introduced into the vacuum vessel 32 from a gas blowing nozzle 38. A gas mixer 40 is connected to the gas blowing nozzle 38. 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, the solid vaporizer 50
Pb vaporized in the above is introduced by the Ar gas as a carrier gas sent through the MFC 44. Third
From the path, the Zr vaporized by the liquid vaporizer 52 becomes M
Ar as carrier gas sent via FC46
Introduced by gas. 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.

(Example 1) 2 inches (50.8 mm) of Si (100) was used as a silicon substrate. This S
The i (100) substrate is ultrasonically cleaned in an organic solvent such as acetone or ethanol, immersed in a 10% HF solution,
The oxide film on the i-substrate surface was removed. Thereafter, the PLD method (also known as Pulsed Laser Ablation: P
LA) method, in vacuum (about 10 ^-5 Torr), substrate temperature: 550 to 650 ° C., laser repetition frequency: 5 to 5
10 Hz, laser energy density: 4.5 J / cm ²
Under the condition of (KrF), a part of the Ti site is
Approximately 100 to 500 nm with 10% substitution in terms of atoms
The TiN thin film (Ti _0.9 Al _0.1 N: TAN) was epitaxially grown. The target used to obtain this TAN thin film was a part of Ti
% Substituted TiN (Ti _0.9 Al _0.1 N: TAN) sintered body was used. The relative density of this sintered body is 90% or more, and preferably a dense one of 95% or more is good.
Next, on this TAN (Ti _0.9 Al _0.1 N) thin film, by the same PLD method, 10 ⁻⁴ Torr, substrate temperature: 550
C, laser repetition frequency: 5-10 Hz, laser energy density: 5.0 J / cm ² (KrF), ultra-thin SRO (SrRuO ₃ ) of about 50-100 nm.
A thin film was grown. For this SRO thin film, a ceramic sintered body target having the same composition was used. Furthermore, this S
The total pressure: 10 Torr (oxygen partial pressure: 5 Torr) and the substrate temperature: 60 on the RO thin film by an MOCVD apparatus as shown in FIG.
At 0 ° C., Pb (Zr _0.52 T
i _0.48 ) O ₃ [PZT] thin film was epitaxially grown. Pb (DPM) ₃ , Zr (Ot-C ₄ H ₉ ) ₄ , T
Using _{i (O-i- C 3 H} 7) 4. Table 1 shows detailed production conditions of the PZT thin film.

[0014]

[Table 1]

In the present invention, the Si substrate is made of Si
It is not limited to (100), but Si (111) or Si (110) can be used. In addition, these Si substrates have a miscut angle of 5 °.
The following can be used: Further, the TAN thin film can be manufactured not only by the PLD method but also by a method such as an electron beam evaporation method, a sputtering method, and an MBE method. Further, the SRO thin film can be manufactured not only by the PLD method but also by a method such as a sputtering method, an MBE method, or a CVD method. In this embodiment, the MOCVD method was used for the production of the epitaxial PZT thin film. However, the present invention is not limited to the MOCVD method.
A method such as the BE method can be applied.

Comparative Example 1 As in Example 1, Si (1
00) In vacuum (about 10) ^-Five Tor
r), substrate temperature: 550-650 ° C, laser repetition
Frequency: 5Hz, laser energy density: 4.5J /
cm^Two(KrF) T of about 100 to 500 nm
AN thin film (Ti_0.9Al_0.1N: TAN) epitaxy
Grew up. Then, on this TAN thin film,
The total pressure: 10 Torr (acid
(Elemental partial pressure 5 Torr), substrate temperature: 600 ° C, 300 ~ 6
00 nm thick Pb (Zr_0.52Ti_0.48) O_Three[PZ
T] A thin film was epitaxially grown.

FIG. 3 shows an XRD pattern of the PZT / SRO / TAN thin film formed on Si in the first embodiment. FIG. 4 shows the result of performing a pole figure analysis to see the orientation of the same sample in the film plane. FIG. 4 shows that a four-fold symmetrical peak was obtained at 90 ° intervals for the thin film formed above TAN.
It can be confirmed that epitaxial growth has occurred on the top. On the other hand, FIG. 5 shows an XRD pattern of the PZT thin film obtained in the comparative example. As a result, although the PZT thin film becomes a perovskite phase, it does not show a tendency to be oriented in a specific axis, indicating that it cannot be epitaxially grown. Table 2 shows the results of evaluating the electrical characteristics of the obtained PZT thin film element. FIG. 6 shows a PE hysteresis loop drawn using the epitaxial PZT thin film according to the first embodiment.

[0018]

[Table 2] ^* 1) tanδ and εr are measured values at 1kHz, 0.1V

(Embodiment 2) As in Embodiment 1, a Si substrate
A TAN thin film (Ti_0.7Al_{0. Three}N)
Was epitaxially grown. On this TAN thin film,
As in the first embodiment, an extremely thin SRO (Sr
RuO_Three) After forming the layer, 5 Torr by PLD method.
(O_TwoAtmosphere), substrate temperature: 500 ° C, laser repetition
Frequency: 5Hz, laser energy density: 4.5J
/ Cm^Two(KrF) of about 500-800 nm
PLT thin film (Pb_0.9La_0.1TiO_ThreeEpitaxy)
Grew up. For manufacturing on this PLT thin film
The target was Pb_0.9La_0.1TiO_ThreeComposition
A Lamix sintered body target was used. FIG. 7 is obtained
3 shows an XRD pattern of a grown epitaxial PLT thin film.
From this, the method of manufacturing a ferroelectric thin film according to the present invention is used.
With this, the PLT thin film is also etched on the Si substrate.
It can be seen that epitaxial growth is possible. In addition, above
In this embodiment, the oxide conductive thin film is made of SRO (SrRuO
_Three), The present invention is not limited to this.
Not something. ABO as an oxide conductive thin film_Three
(A is at least selected from La, Sr, and Ba
B is at least one selected from Ru and Co
Suitable for conducting thin films with perovskite structure
It can be used as appropriate. And specifically, SrRuO
_ThreeOther than BaRuO_Three, (Ba, Sr) RuO_Three,
(La, Sr) CoO_ThreeIs preferred.

[0020]

By using the method for producing a ferroelectric thin film of the present invention, a Pb-based perovskite oxide such as PZT can be formed on TiN without using advanced process control technology. (Uniaxial orientation or more) can be grown. Therefore, a Pb-based perovskite-type ferroelectric oxide thin film typified by PZT, which has been extremely difficult to date, can be relatively easily and highly oriented grown on single-crystal Si. The ferroelectric thin-film element obtained by the present invention can be used for DRAM, FeR
It is expected to be applied not only to AM and the like but also to other pyroelectric elements, microactuators, thin film capacitors, and small piezoelectric elements.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows TAN, SRO and PL in the present invention.
FIG. 2 is an illustrative view of a PLD device used for producing a T thin film.

FIG. 2 is an illustrative view of an MOCVD apparatus used for producing a PZT thin film in Example 1 and Comparative Example 1 of the present invention.

FIG. 3 shows the X of the PZT thin film prepared in Example 1 of the present invention.
It is an RD pattern figure.

FIG. 4 is a pole figure of the PZT thin film shown in FIG.

FIG. 5 is an XRD pattern diagram of the PZT thin film manufactured in Comparative Example 1.

FIG. 6 is a graph showing the DE of the epitaxial PZT thin film of Example 1.
Shows hysteresis characteristics.

FIG. 7 shows the XR of the PLT thin film produced in Example 2.
It is a D pattern figure.

[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 Drive manipulator 24 Laser focusing lens 26 Synthetic quartz window 28 Plume 30 MOCVD apparatus 32 Vacuum container 34 Substrate heater 36 Vacuum pump (Mechanical booster pump) 38 Gas blowing nozzle 40 Gas mixer 42,44,46,48 Mass flow controller 50 Solid vaporizer 52,54 Liquid vaporizer S Substrate T Target L Excimer laser beam (beam line)

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 41/09 (72) Inventor Lee Jin Min 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (Reference) 5F038 AC15 AC18 DF05 EZ14 5F083 FR01 JA13 JA15 JA40 JA42 JA45 PR21 PR22 PR25

Claims (12)

[Claims] A SiN substrate, a TiN thin film formed by epitaxial growth on the Si substrate and a part of Ti replaced by Al, an oxide conductive thin film formed by epitaxial growth on the TiN thin film, and A ferroelectric thin film element including an oxide ferroelectric thin film having a perovskite structure formed by orienting growth on the oxide conductive thin film, wherein the Ti site in the TiN thin film has an Al substitution amount of Al atom. Wherein the oxygen content in the TiN thin film is 5% or less in terms of oxygen atoms. 2. The oxide conductive thin film is made of ABO ₃ (A is at least one selected from La, Sr, and Ba;
2. The ferroelectric thin film element according to claim 1, wherein the ferroelectric thin film element has a perovskite structure represented by (B is at least one selected from Ru and Co). 3. The oxide conductive thin film is made of SrRuO ₃ ,
BaRuO ₃ , (Ba, Sr) RuO ₃ or (La,
_3. The ferroelectric thin film element according to claim 2, wherein the ferroelectric thin film element is one of Sr) CoO ₃ . 4. The ferroelectric thin film device according to claim 1, wherein the oxide ferroelectric is a Pb-based perovskite compound. 5. The method according to claim 1, wherein the Pb-based perovskite compound is A
BO ₃ (containing at least Pb or Pb and La as a constituent element of the A site, and containing Tb as a constituent element of the B site
5. The ferroelectric thin film element according to claim 4, wherein the ferroelectric thin film element is a perovskite oxide represented by (i.e., at least one selected from i, Zr, Mg, and Nb). 6. The ferroelectric thin film element according to claim 1, wherein said ferroelectric thin film is grown epitaxially. 7. A step of epitaxially growing a TiN thin film in which part of Ti is replaced with Al on a Si substrate; a step of epitaxially growing an oxide conductive thin film having a perovskite structure on the TiN thin film; A method for producing a ferroelectric thin-film element comprising a step of orientingly growing a ferroelectric thin-film element having a perovskite structure on a conductive thin film, wherein the Al substitution amount of Ti sites in the TiN thin film is converted into Al atoms. Wherein the oxygen content of the TiN thin film is 5% or less in terms of oxygen atoms. 8. The oxide conductive thin film is made of ABO ₃ (A is at least one selected from La, Sr, and Ba;
8. The method according to claim 7, wherein the ferroelectric thin film element has a perovskite structure represented by (B is at least one selected from Ru and Co). 9. The oxide conductive thin film is made of SrRuO ₃ ,
BaRuO ₃ , (Ba, Sr) RuO ₃ or (La,
9. The method for producing a ferroelectric thin film element according to claim 8, wherein the ferroelectric thin film element is one of Sr) CoO ₃ . 10. The method for manufacturing a ferroelectric thin film device according to claim 7, wherein the oxide ferroelectric is a Pb-based perovskite compound. 11. The Pb-based perovskite compound,
Perovskite oxide containing at least Pb or Pb and La as a constituent element of A site represented by ABO ₃ and at least one selected from Ti, Zr, Mg and Nb as constituent elements of B site The method for manufacturing a ferroelectric thin-film element according to claim 10, wherein: 12. The method according to claim 7, wherein said ferroelectric thin film is grown epitaxially.
2. The method for manufacturing a ferroelectric thin film element according to any one of 1.