JPH08222711A - Ferroelectric capacitor and formation of ferroelectric capacitor and ferroelectric film - Google Patents

Abstract

PURPOSE: To provide a ferroelectric capacitor having an electrode structure, which is a dense structure in a film-forming method, such as a sol-gel method, and makes the formation of a ferroelectric film, such as a PZT ferroelectric film which shows good electrical characteristics, possible, and methods of forming this ferroelectric capacitor and the ferroelectric film. CONSTITUTION: A ferroelectric capacitor is formed into a structure, wherein the capacitor is provided with a Pt electrode 6 and a PZT ferroelectric film 7 formed on this electrode 6 and a TiOX layer 31, which is one of the constituent metallic element oxide layers of the ferroelectric film, is deposited on the interface between the electrode 6 and the film 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric capacitor (in particular, a capacitor for a semiconductor memory cell having a lead zirconate titanate (PZT) film), a ferroelectric capacitor and a method for forming a ferroelectric film. It is a thing.

[0002]

2. Description of the Related Art For example, an ONO film having a structure in which SiO ₂ , Si ₃ N ₄ and SiO ₂ are sequentially stacked is used as an insulating film (dielectric film) which constitutes a capacitor of a memory cell of a dynamic RAM. ing.

However, since the effective relative permittivity of this ONO film is as small as about 5, when it is applied to a large-capacity memory of 256 Mb or more, the film thickness of the capacitor dielectric film is reduced under the restriction of area. In addition, a complicated shape is required to expand the area, which causes great difficulty in the process.

On the other hand, since the perovskite crystal structure type ferroelectric material has an extremely large relative dielectric constant of several hundreds to several thousands, it is attracting attention as an insulating film material for a capacitor for future dynamic RAM. .

Of the ferroelectric materials, Pb (Zr, Ti) O
To form the PZT film indicated by ₃ , a sol-gel method, a CVD (chemical vapor deposition method), a sputtering method, or the like can be adopted as a thin film forming method, and among them, the sol-gel method is preferable. .

In the film formation by the sol-gel method, the quality of the prepared raw material solution (sol-gel solution), the film formation process and its conditions, and the choice of the substrate should determine the electrical characteristics of the finally obtained thin film. become.

FIG. 18 shows two examples (1) and (2) of the conventional lower electrode structure. That is, as the lower electrode structure of the dielectric, an electrode having a Pt / Ti / TiN structure (hereinafter, may be abbreviated as Pt / Ti / TiN) in order from the top, or
An electrode having a Pt / TiN structure (hereinafter sometimes abbreviated as Pt / TiN) is provided and joined to the poly-Si (Poly-silicon) conductive layer 30 in the contact hole 12 of the SiO ₂ underlayer 21. A PZT film 7-1 or 7 with a film thickness of 200 nm formed by the sol-gel method on the upper surface of each lower electrode.
-2 is formed. Each electrode is provided with a TiN barrier layer 20, but the former electrode has a Pt layer 6
A Ti layer 22 is further provided immediately below.

Comparing these PZT thin films, the SEM (Scanni) of these PZT thin films is shown in FIGS. 3B and 3C.
ng electron microscope) As shown in the observation photograph, Pt /
In the Ti / TiN electrode, fine particles are formed,
An extremely dense PZT thin film can be obtained, but in the Pt / TiN electrode, the particle size called rosette is 50
It can be seen that huge particles of 0 nm to 1000 nm are formed.

Then, when platinum electrodes were formed on the surfaces of these two PZT thin films and electric measurement was performed, Pt / Ti / T was obtained.
The thin film formed on iN has a leakage current value of about 6 × 10 ⁻⁷ A / cm ² when 4 V is applied, whereas Pt / TiN
The thickness of the thin film formed above is about 2 × 10 ⁻⁵ A / cm ² (see FIG. 5). This indicates that the thin film formed by depositing the Ti layer on the electrode provided between the Pt layer and the TiN layer exhibits superior IV characteristics.

The reason for this is that in the Pt / Ti / TiN electrode, the underlying Ti diffuses to the Pt surface during heat treatment,
It is considered that oxidization forms TiO _x , which becomes PZT having a dense film structure because it increases the nucleus density that promotes PZT crystallization during growth of the PZT thin film.

However, in the Pt / Ti / TiN electrode, the underlying Ti layer 22 is oxidized during the PZT sintering in the sol-gel method, so that the contact resistance between Pt and TiN increases (for example, in a normal case). 80Ω / μm ² is 30
It becomes 00 Ω / μm ² . ) And other serious problems are likely to occur.
Therefore, formation of a PZT thin film in a good crystalline state and Ti
It is difficult to simultaneously solve the problem of oxidation of the intermediate layer.

On the other hand, in order to improve the crystallinity of PZT,
A method is known in which a perovskite-based substance that easily crystallizes once is formed on a Pt electrode. For example, the film thickness on Pt
There is a method of forming a PZT thin film by a sol-gel method after forming a 50 nm PTO (lead titanate, PbTiO ₃ ) layer. For PZT by the CVD method, PLT
(Lead lanthanum titanate, (Pb, La) _x (Ti, Z
r) The _1-X O ₃ ) layer is formed on Pt and then the PZT thin film is formed.

However, in all of these methods, since a PTO layer or a PLT layer having a dielectric constant different from that of PZT exists at the interface between Pt and PZT, performance as a capacitor (for example, remanent polarization density, dielectric constant). Etc.) easily deteriorate.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to enable formation of a ferroelectric thin film such as PZT having a dense structure and good electrical characteristics in a film forming method such as a sol-gel method. An object of the present invention is to provide a capacitor having an electrode structure and a method for forming the capacitor and the ferroelectric film.

[0015]

Means for Solving the Problems The present inventor
An electrode structure that intentionally disperses and deposits lumpy titanium oxide TiO _x on the surface of t to promote the nucleation of PZT crystallization to make PZT particles finer and form a PZT thin film having a dense structure. The inventors have found a method of manufacturing a PZT capacitor using the same, clarified the behavior of Ti in a Pt electrode, established a novel electrode structure and a method of manufacturing a PZT capacitor, and arrived at the present invention.

That is, the present invention comprises an electrode and a ferroelectric film formed on the electrode, and a metal element constituting the ferroelectric film is provided at the interface between the electrode and the ferroelectric film. Of these, a ferroelectric capacitor in which an oxide of at least one element is deposited.

In the capacitor of the present invention, the electrode is made of a conductor such as Pt which is not easily oxidized at room temperature, and the oxide is a metal oxide (eg Ti) which is easily oxidized at room temperature.
It is preferable that the metal oxide is TiO _x such as O ₂ ) and the metal oxide is a deposit having a film thickness of 0.01 to 10 nm.

Further, it is preferable to provide a barrier layer such as TiN under the electrodes to prevent the diffusion of the constituent elements of the capacitor. It is preferable that the ferroelectric film is lead zirconate titanate-based, for example, PZT.

According to the present invention, for example, it is possible to form a PZT thin film having a dense structure without providing a Ti intermediate layer between Pt and TiN as in the prior art, and to form a PZT thin film like a Ti intermediate layer. The problem of increase in contact resistance due to oxidation does not occur. Therefore, it is possible to simultaneously form a ferroelectric film such as PZT in a good crystal state (reduction of leak current) and solve the problem of oxidation of the intermediate layer (reduction of contact resistance).

According to the present invention, when forming the above ferroelectric capacitor or ferroelectric film, an oxide of at least one element of the metal elements constituting the ferroelectric film is deposited on the electrode. The present invention also provides a method for forming a ferroelectric capacitor or a ferroelectric film, which comprises forming the ferroelectric film on the electrode containing the deposited metal oxide.

In this method, when forming the capacitor electrode, it is preferable to deposit the metal oxide in an island shape on the outermost surface of the electrode in contact with the ferroelectric film and then form the ferroelectric film by the sol-gel method. .

[0022]

EXAMPLES The present invention will be described below with reference to examples.

First, referring to FIG. 1, the PZT according to the present invention.
A ferroelectric capacitor CAP having a thin film and a semiconductor device incorporating the same, for example, a dynamic RAM which is a volatile memory element will be schematically described.

In this device, the silicon substrate 1
On top of it, for example, an N ⁺ type source region 3 and an N ⁺ type drain region 4
Are formed by impurity diffusion, and a word line WL is provided between these regions via a gate oxide film 5.
The bit line BL is connected to the drain region 4.

The capacitor CAP is called a stack type, and a lower electrode composed of a source region 3-polysilicon layer 30-barrier layer 20-Pt layer 6-TiO _x layer 31 is connected to the lower electrode. A PZT ferroelectric film 17 and an upper electrode 18 are sequentially laminated on the above. This structure is characterized in that a Pt electrode in which TiO _x 31 is nucleated is formed on Pt6.

Next, referring to FIG. 2, a method of forming the basic lower electrode and the ferroelectric film of the ferroelectric capacitor CAP of FIG. 1 on the SiO ₂ layer on the Si wafer as a base layer will be described. explain. First, in step 1, a SiO ₂ layer 21 was grown to a thickness of 100 nm on a thermally oxidized Si wafer 1, and a TiN thin film 20 having a thickness of 200 nm was formed on this by a reactive sputtering method.

Next, in step 2, a Pt thin film 6 having a film thickness of 200 nm was formed on the TiN thin film 20 formed in step 1 by an electron beam heating evaporation method.

Next, in step 3, TiO _x 31 having a thickness of 2 nm was deposited on the Pt thin film 6 formed in step 2 by the RF sputtering method using a TiO ₂ target. In FIG. 7, P with nucleated titanium oxide (TiO _x ).
An AFM (Atomic force microscope) image of each surface of the t / TiN electrode (A) and the untreated Pt / TiN electrode (B) is shown. It can be seen that what is observed in an island shape in FIG. 7A is titanium oxide, which is scattered on the electrode surface.

TiO produced in steps 1 to 3
It is a Pt electrode with a nucleated _X / Pt / TiN structure. The TiO _x deposited on the surface of this Pt thin film acts as the nucleus of the PZT crystal.

Next, in step 4, an amorphous PZT thin film 17 'having a film thickness of 200 nm was formed by the sol-gel method. Amorphous thin film formation temperature is 480 ℃ (10 minutes, in air)
Met. The raw material solution of this sol-gel method is Pb (CH
_{3 COO) 2 · 3H 2 O} , Ti {(CH 3) 2 CHO} 4,
Zr {CH ₃ (CH ₂ ) ₂ CH ₂ O} ₄ and NH (CH ₂ C
H ₂ OH) ₂ in CH ₃ OC ₂ H ₄ OH,
This was applied and dried.

Next, in step 5, the amorphous PZT thin film 17 'formed in step 4 was sintered in air at 600 ° C. for 10 minutes. By this sintering treatment, PZT is crystallized and becomes a ferroelectric thin film 17 having a perovskite structure. During this crystallization, TiO _X 31 at the interface between the amorphous PZT 17 ′ and Pt 6 increases the PZT nucleus density and forms a thin film 17 having a dense structure.

Next, in step 6, a Pt upper electrode 18 having a film thickness of 200 nm was formed on the PZT thin film 17 of perovskite crystal formed in step 5 by an electron beam heating evaporation method. As a result, the PZT capacitor CAP was formed. The composition of this PZT thin film is Pb: Zr:
Ti = 1.1: 0.5: 0.5 may be sufficient.

FIG. 3A is a SEM of the PZT thin film 17 formed on the above Pt / TiN electrode with TiO _x nucleated.
An observation photograph is shown. According to this, as shown in FIGS. 3B and 3C, the particle size of PZT formed on the Pt / Ti / TiN electrode or the Pt / TiN electrode is extremely large from 500 nm to 1000 nm. As shown in FIG.
PZT formed on the _X / Pt / TiN electrode has a particle size of 100 nm
It is a fine particle having the following fine particles and a dense structure (a film structure having a uniform thickness direction). That is, based on the present invention, it was confirmed that the TiO _x deposited as nuclei has the effect of making the PZT particles finer and denser.

FIG. 4 shows the surface of the PZT thin film depending on the grain size of TiO _x deposited as nuclei. According to this, although the particle size of the PZT by the particle size of the TiO _X are different, between which it is such that the relationship corresponding to the particle size of the TiO _X is not present directly. Not to mention the particle size shown in Fig. 4, the particle size of TiO _x is 0.5 to 50
In the range of 0 nm, the effect of miniaturization and densification of the PZT thin film can be obtained.

Next, as described above, the PZT thin film formed on the Pt / TiN electrode with TiO _x nucleated, and TiO 2.
PZT formed on Pt / TiN electrode that does not nucleate _X
The electrical characteristics of the thin film are compared.

First, FIG. 5 shows the IV characteristic. According to this data, the leakage current value of the PZT thin film formed on the Pt / TiN electrode shows a remarkable increase with the increase of the applied voltage, but the leakage current value of the PZT thin film formed on the TiO _x nucleated Pt / TiN electrode is increased. The leakage current value does not depend on the applied voltage and is almost constant. The leakage current value when 4 V is applied is Ti
1 × 10 ^-7 A for Pt / TiN electrode with O _x nucleation
/ cm ² but about 2 × 10 ^-5 A / cm ^{2 for} Pt / TiN electrode without nucleation (about 6 × 10 ^-7 A / cm ^{2 for} Pt / Ti / TiN electrode) . I-by nucleation
It is clear that the V characteristic has been remarkably improved.

Further, as shown in FIG.
The leakage current value is about 1 × 10 ⁻⁷ A / cm ² when using TiO _X nucleated Ir (iridium) in addition to iO _X nucleated Pt / TiN, which is equivalent to the Pt / TiN electrode. It can be seen that the excellent IV characteristics of The surface of the PZT thin film when Ir is used as the electrode is shown in FIG.
It can be seen that ZT is a fine particle having a particle size of 100 nm or less and is dense.

FIG. 6 shows the hysteresis curves of thin films formed on nucleated Pt / TiN electrodes at maximum voltages of 3V and 5V. At 3 V, the characteristics of remanent polarization density of 13.7 μC / cm ² and coercive electric field value of 53 kV / cm are obtained. At 5 V, the remanent polarization density was 18.7 μC / cm ² , and the coercive electric field value was 62 kV / cm ² . On the other hand, Pt / Ti without nucleation
In the thin film formed on the N electrode, the polarization characteristics could not be measured because the leakage current value was large.

Pt / Ti with nucleated TiO _x described above
Regarding a capacitor formed by forming a PZT thin film on N,
The IV characteristics and polarizability which are the capacitor performance are shown in FIG.
And as shown in FIG. 6, it was good. Further, the contact resistance of this capacitor was as good as 80 Ω / μm ² .

In the examples described above, PZT film formation was carried out by the sol-gel method on the Pt substrate on which TiO _x was nucleated. In this case, the particle size of TiO _x is usually 0.5 to 500n.
m is preferably 5 to 200 nm, but if the particle size of TiO _x is too small or large, the nucleating effect becomes poor. The film thickness of TiO _x is usually 0.01 to 10 nm, and
5 to 5 nm is preferable, 1.5 to 2.5 nm is even better, but if the film thickness is too thin, the nucleating effect is poor, and if it is too thick, Ti
Tend to aggregate (segregate) in the film to form a non-uniform film.

Next, a semiconductor device incorporating the capacitor according to the present embodiment, for example, a memory cell of a dynamic RAM which is a volatile memory (for example, a stack type)
Will be explained.

First, referring to FIGS. 16 and 17, an example of a memory cell of the dynamic RAM is shown.

For example, an element region partitioned by the field oxide film 2 is formed on one main surface of the P ⁻ type silicon substrate 1, and a memory cell M including a transfer gate TR composed of a MOS transistor and a capacitor CAP is formed therein.
-CEL is provided.

In the transfer gate TR, for example, an N ⁺ type source region 3 and an N ⁺ type drain region 4 are formed by impurity diffusion, and a word line WL is provided between these regions via a gate oxide film 5. The bit line BL is connected to the drain region 4 through a contact hole 11 of insulating layers 9 and 10 made of SiO ₂ or the like.

The capacitor CAP is called a stack type, and the barrier layer 20 (further, a poly-Si layer (not shown)) and the lower electrode 6 are provided in the source region 3 through the contact hole 12 of the insulating layer 10. The PZT ferroelectric film 17 and the upper electrode 18 are sequentially stacked on the lower electrode with the TiO _x nucleation layer 31 interposed therebetween.

Ferroelectric film 17 forming the capacitor CAP
Is a PZT formed by a sol-gel method using a raw material solution,
That is, it is composed of a Pb (Zr, Ti) O ₃ film. Also,
The lower electrode 6 is made of, for example, Pt or the like deposited on a TiN layer. The upper electrode 18 in contact with the ferroelectric film 17 is made of Pt, Au, aluminum or the like.

Next, a method of manufacturing this memory cell M-CEL will be described with reference to FIGS.

First, as shown in FIG. 9, a field oxide film 2 is formed on a P ⁻ type silicon substrate (wafer) 1 by a selective oxidation method.
To form the gate oxide film 5 by the thermal oxidation method and the polysilicon word line WL by the chemical vapor deposition method, respectively, and further by thermal diffusion of N type impurities such as As, the N ⁺ type source region 3 and the drain region. 4 are formed respectively.

Then, a contact hole 12 is formed on the source region 3 by photolithography with respect to the SiO ₂ insulating layer 10 deposited on the entire surface by chemical vapor deposition.

Then, as shown in FIG. 10, contact holes are formed.
On top of the TiN layer (which may be provided with a poly-Si layer) 20 to join to the source region 3 at 12, Pt.
A lower electrode having a layer 6 is formed, and a TiO _x layer 31 is further formed by sputtering. This is a TiN layer deposited on the entire surface,
It can be formed by patterning the Pt layer and the TiO _x layer by photolithography.

Then, as shown in FIG. 11, the lower electrode and the Ti
On the entire surface including the O _X layer by spin coating or dip coating, applying a sol-gel raw material solution 27 '.

Next, the wafer coated with the raw material solution 27 'is heated at a predetermined temperature (100 to 300 ° C., for example 170 ° C.) for 3 minutes to dry the coated solution, and as shown in FIG.
A dry gel film 27 is formed.

Then, the dried wafer was processed at 480 ° C. to be amorphized. Then, it is sintered (oxidized and sintered) for 10 minutes, for example, at a temperature (600 ° C. or higher, for example 600 ° C.) at which perovskite crystals are generated in the atmosphere, and the ferroelectric film 17 is formed on the entire surface as shown in FIG.

The ferroelectric film 17 has a predetermined thickness (for example,
2000 Å), the coating process of FIG. 11 and the drying process of FIG. 12 and the above-mentioned sintering process are repeated as necessary, and the dried film is laminated instead of the intended coating thickness at once. To obtain the final film thickness.

Then, as shown in FIG. 14, unnecessary portions of the ferroelectric thin film 17 formed on the entire surface are removed by a dry etching method or the like to form the PZT ferroelectric film 17 on the lower electrode 6 in a predetermined pattern. .

Next, as shown in FIG. 15, an upper electrode 18 made of platinum or the like is formed in a predetermined pattern on the junction with the ferroelectric thin film 17 by photolithography.

Further, the interlayer insulating film 9, the contact hole 11 and the bit line BL are respectively formed by a known method,
A memory cell as shown in 16 is manufactured.

In this memory cell, the ferroelectric film 17 of the capacitor CAP is Pt in which TiO _x nuclei based on the present invention are nucleated.
Since it is formed on the electrode, as described above, the film structure is dense, the particles are fine, the remanent polarization value is large, and the electrical characteristics with little leak current can be obtained.

Although the embodiments of the present invention have been described above, the above embodiments can be further modified based on the technical idea of the present invention.

For example, regarding the electrode material and the nucleating substance,
First, as an electrode material, it withstands the crystallization temperature of PZT,
In addition to Pt, Ir, Pd, P other than Pt can be used as long as it is a metal or oxide that does not easily oxidize, is a conductor at room temperature, and does not contain Ti.
t-Pd alloy, Cr, Ni, Ni-Cu alloy, Ru
It may be O ₂ , TiN, TaN, IrO ₂ or the like. And as a nucleating substance to be deposited on the surface of this electrode,
Although TiO _x such as TiO ₂ is used, if the metal is a metal that easily forms an oxide at room temperature, it includes Ti, Zr other than Ti, P
Oxides of one or more of the elements b, Sr, Ba, La, Zn, Nb, Fe can be deposited on the electrodes.

Of the above metals that can be used here, La,
Zn, Nb and Fe are elements that can be added to the ferroelectric film. Ti, Zr and Pb are the main components of PZT, and Sr
And Ba are the main components of BSTO ((Sr, Ba) TiO ₃ ).

In order to form the above-mentioned metal oxide, not only the sputtering method but also the vapor deposition method of electron beam heating in a high vacuum is used, and Ti, Zr, Pb, Sr, Ba, La and Z are formed.
After depositing n, Nb, and Fe, an oxygen-containing environment (for example,
A method of natural oxidation in the atmosphere) is also possible.

In this case, since Ti is an extremely active substance in particular, the deposit formed by the electron beam heating vapor deposition method is oxidized by the residual oxygen in the vapor deposition chamber, so that it is necessary to strongly perform the oxidation treatment. Absent. The film thickness of TiO _x is 0.01
nm to 10 nm is preferred. Examples of the oxide deposition method include a sputtering method, a CVD method, and a vapor deposition method.

Since the effect of nucleation can be expected regardless of the thickness of the electrode layer, the thickness of the electrode layer may be 0.05 nm or more.

The electrode structure is a nucleating material layer / electrode layer / barrier layer, and the barrier layer below the electrode is provided with an underlayer, for example, a SiO ₂ layer thereunder, and a contact hole provided in the SiO ₂ underlayer. A structure joined to the poly-Si conductive layer inside is conceivable. Applicable structures are eg TiO _x /
Pt / TiN / Si, but another typical structure from the combination of the above materials is TiO _x / Ir / Ti.
N / Si, TiO _x / IrO ₂ / Si, TiO _x / Pt
/ RuO ₂ / Si, TiO _x / Pt / IrO ₂ / Si,
TiO _x / RuO ₂ / Si, TiO _x / TiN / Si,
TiO _x / Ni / Ti / Si, TiO _x / ITO (Indi
um tin oxide) / Si, ZrO _x / Pt / RuO ₂ / S
i and the like.

As a method of forming a PZT thin film other than the sol-gel method, a sputtering method, a CVD method, a laser ablation method and the like can be mentioned. In the film formation by the CVD method or the sputtering method, it is possible to first deposit a substance such as TiO _x as a nucleus on a Pt substrate and then form a PZT thin film.

The material of the ferroelectric film that can be used is P
In addition to ZT, PZT added with Nb, Zr, Fe, etc., BSTO ((Sr, Ba) TiO ₃ ), PLT
It may be ((Pb, La) _x (Ti, Zr) _1-x O ₃ ).

A ferroelectric film according to the present invention is shown in FIG.
The present invention can be applied to a device having a Pt / PZT / Pt / barrier layer / poly-Si structure capacitor (stack type capacitor) shown in FIG. 1, but is not limited to this, and the above stack type capacitor is provided on the SiO ₂ film. The lower electrode of the lever capacitor may be extended and connected to the source region of the transfer gate, or may be applied to a capacitor having a structure in which a capacitor is incorporated in a so-called trench (groove) instead of the stack type. .

[0069]

The present invention, as described above, includes an electrode,
A ferroelectric film formed on the electrode, wherein an oxide of at least one element of the metal elements constituting the ferroelectric film is present at the interface between the electrode and the ferroelectric film. A capacitor having an electrode structure capable of forming a ferroelectric thin film, such as PZT, which has a dense structure in a film forming method such as a sol-gel method and which exhibits good electrical characteristics because of being deposited, and this capacitor And a method for forming a ferroelectric film can be provided.

That is, the present invention differs from the above-mentioned prior art in that PZT is formed by dispersing and depositing a substance such as titanium oxide, which can be formed relatively easily, in a lump form on the electrode surface.
Etc. to increase the nucleus density, promote crystallization thereof, miniaturize crystal grains, and enable formation of a ferroelectric thin film having a dense structure.

Therefore, according to the present invention, it is possible to provide a uniform film structure in the thickness direction of the ferroelectric film. Further, since the Ti layer is not required as the underlying layer of the lower electrode, the TiO _X layer is not formed inside the electrode even in the film formation in the oxygen-containing atmosphere, so that the problem of increasing contact resistance does not occur. The present invention solves these problems at once.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a semiconductor device incorporating a ferroelectric capacitor according to the present invention.

FIG. 2 is each schematic cross-sectional view showing the flow of manufacturing the same capacitor.

FIG. 3 is a sketch diagram showing a comparison of SEM images of PZT thin films formed on a Pt substrate.

FIG. 4 is each sketch diagram showing SEM images of PZT thin films formed on Pt substrates having various TiO _x nuclei for comparison.

FIG. 5 is an IV characteristic diagram of PZT thin films formed on various substrates.

FIG. 6 is a hysteresis curve diagram of polarization values of the PZT thin film.

FIGS. 7A and 7B are sketch diagrams showing AFM images of respective surfaces of an electrode with nucleated TiO _x and an electrode without nucleated, which are compared with each other.

FIG. 8: P formed on an Ir substrate with TiO _x nucleated
It is a sketch drawing of the SEM image of a ZT thin film.

FIG. 9 is an enlarged cross-sectional view showing one process step of a method of manufacturing a memory cell of a dynamic RAM incorporating a ferroelectric capacitor according to the present invention.

FIG. 10 is an enlarged cross-sectional view showing another process step of the method for manufacturing the memory cell.

FIG. 11 is an enlarged cross-sectional view showing another process step of the method for manufacturing the memory cell.

FIG. 12 is an enlarged cross-sectional view showing another process step of the method for manufacturing the memory cell.

FIG. 13 is an enlarged cross-sectional view showing another process step of the method for manufacturing the memory cell.

FIG. 14 is an enlarged cross-sectional view showing another process step of the method for manufacturing the memory cell.

FIG. 15 is an enlarged cross-sectional view showing still another process step of the method for manufacturing the same memory cell.

FIG. 16 is an enlarged cross-sectional view of the memory cell (XVI-XVI in FIG. 17).
It is a line sectional view).

FIG. 17 is an enlarged plan view of the memory cell.

FIG. 18 is a schematic cross-sectional view of two examples of conventional ferroelectric capacitors.

[Explanation of symbols]

1 ... Silicon substrate 3 ... N ⁺ type source region 4 ... N ⁺ type drain region 6 ... Pt electrode 7-1, 7-2, 17 ... Ferroelectric film (PZT thin film) 18 ... Upper electrode 20 ... Barrier layer 21 ... Underlayer 22 ... Ti layer 30 ... Poly Si layer 31 ... TiO _X layer CAP ... Ferroelectric capacitor TR ... Transfer gate M-CEL ... Memory cell WL ... Word line (gate electrode) BL ... Bit line

Claims (8)

[Claims] 1. An electrode and a ferroelectric film formed on the electrode, wherein at least one of constituent metal elements of the ferroelectric film is provided at an interface between the electrode and the ferroelectric film. A ferroelectric capacitor in which an oxide of one element is deposited. 2. The ferroelectric capacitor according to claim 1, wherein the electrode is made of a conductor that is not easily oxidized at room temperature, and the oxide is made of a metal oxide that is easily oxidized at room temperature. 3. The ferroelectric capacitor according to claim 1, wherein the oxide is a deposit having a film thickness of 0.01 to 10 nm. 4. The ferroelectric capacitor according to claim 1, wherein a barrier layer is provided under the electrode. 5. The ferroelectric capacitor according to claim 1, wherein the ferroelectric film is a lead zirconate titanate system. 6. When forming the ferroelectric capacitor according to claim 1, an oxide of at least one element of the metal elements constituting the ferroelectric film is formed on the electrode. And forming the ferroelectric film on the electrode containing the deposited oxide. 7. When forming the ferroelectric film according to claim 1, depositing an oxide of at least one element of the constituent metal elements of the ferroelectric film. A method of forming a ferroelectric film, comprising forming the ferroelectric film on an electrode. 8. The forming method according to claim 7, wherein the ferroelectric film is formed by a sol-gel method.