JPH10173140A - Manufacture of ferroelectric capacitor and manufacture of ferroelectric memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high-quality ferroelectric thin film by forming excellent crystal nuclei by depositing a metallic or metal oxide thin film, a metal oxide material, and a ferroelectric material by sputtering, etc. SOLUTION: After an Ir thin film 6 is formed on a silicon oxide film 10 formed on an Si substrate 1, a Ti film 31 is deposited on the Ir thin film 6 at a room temperature. Then a PbTiO3 film 33 is formed as crystal nuclei by depositing PbO 32 on the Ti film 31 by sputtering using a PbO ceramic target at a temperature higher than the crystallization temperature of PbTiO3 and a Pb(Ti, Zr)O3 thin film 17 is deposited on the film 33 by sputtering Pb(Ti, Zr)O3 34. Since the formed PbTiO3 film 33 becomes perovskite crystal nuclei, the particles 17A of the deposited Pb(Ti, Zr)O3 thin film 17 grow in columnar shapes and excellently deposit due to the crystal nuclei of the base film 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a ferroelectric capacitor (particularly, a capacitor of a semiconductor memory cell having a lead zirconate titanate (PZT) film) and a method of manufacturing a ferroelectric memory device. is there.

[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 laminated is used as an insulating film (dielectric film) constituting a capacitor of a memory cell of a dynamic RAM. Have been done.

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

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

[0005] Among ferroelectric materials, Pb (Zr, Ti) O
_{In order} to form the PZT film shown in ₃ above, 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. This method is most suitable for a mass production process as a method for uniformly forming a thin film on a flat portion having a large area without being affected by the size.

However, in the formation of a PZT thin film by a sputtering method, a favorable density is formed because the formation density of PZT crystallization nuclei on a substrate is low and PbO is evaporated during film formation due to its low crystallinity. PZ showing electrical characteristics
The manufacture of T-capacitors is relatively difficult.

[0007] Platinum (Pt) is generally used as an electrode material of a PZT capacitor. However, since Pt has no reducing ability to the silicon oxide film, it cannot be directly adhered. Therefore, after forming a Ti adhesive layer of about 50 nm on a silicon oxide film, Pt is deposited by a sputtering method or an evaporation method using an electron beam heating method.

In the case of forming a PZT thin film on such Pt, in the film formation by the sol-gel method, Ti diffuses at the Pt grain boundary during heat treatment, and TiO is formed on the Pt-PZT interface.
₂ is formed, which acts as a crystal nucleus during PZT film formation.
However, in the sputtering method, the evaporation of PbO is intense, and it is more difficult to form a PZT thin film of higher quality than in the sol-gel method.

On the other hand, it is known to use an electrode made of an oxidizing metal such as iridium (Ir) or a conductive oxide such as iridium oxide (IrO ₂ ) to improve the polarization fatigue characteristics of the PZT capacitor. . However, when these substances are used as a substrate, even if a Ti layer is formed as an adhesive layer, a nucleation effect due to the diffusion of Ti cannot be obtained.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide Pt
It is an object of the present invention to provide a method capable of forming a high-quality ferroelectric thin film by good nucleation when manufacturing a ferroelectric capacitor such as a PZT capacitor using an electrode material such as Ir as an electrode other than Ir.

[0011]

That is, the present invention provides a first electrode made of iridium or the like, a ferroelectric film made of lead zirconate titanate or the like on the first electrode, When manufacturing a ferroelectric capacitor composed of a second electrode made of iridium or the like on a film, at least one metal element or an oxide thereof (for example, titanium) of a metal element constituting the ferroelectric film is converted into the ferroelectric capacitor. Metal or metal oxide thin film (eg, titanium thin film) deposited on the first electrode
Forming an oxide of a metal element (for example, lead oxide: PbO) which is at least one kind of metal element constituting the ferroelectric film and which is different from the metal or metal oxide thin film. A step of depositing on the metal or metal oxide thin film, and an oxide film (eg, titanium) of the deposited metal oxide (eg, lead oxide) and a metal element (eg, titanium) of the metal or metal oxide thin film Lead titanate: Pb
Forming TiO ₃ ) on the first electrode, and forming the ferroelectric film as a constituent material (for example, lead zirconate titanate: Manufacturing a ferroelectric capacitor, comprising: depositing Pb (Ti, Zr) O ₃ ) to form the ferroelectric film; and forming the second electrode on the ferroelectric film. The present invention also relates to a method of manufacturing a ferroelectric memory device, including a step of manufacturing a ferroelectric capacitor in a memory cell by this manufacturing method.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method for manufacturing a ferroelectric capacitor and a method for manufacturing a ferroelectric memory device according to the present invention,
The metal or metal oxide thin film (or, for example, the titanium thin film), the metal oxide (or, for example, the lead oxide), and the constituent material of the ferroelectric (or, for example, the lead zirconate titanate) are each subjected to a sputtering method. It is desirable to deposit by a chemical vapor deposition method or a vacuum evaporation method.

In particular, after depositing the metal or metal oxide (eg, the titanium thin film), the metal oxide is deposited at a substrate temperature equal to or higher than the crystallization temperature of the constituent material of the ferroelectric film (eg, lead titanate). (For example, the lead oxide) is deposited by a sputtering method, and further, a constituent material (for example, the lead zirconate titanate) of the ferroelectric film is deposited by a sputtering method at a substrate temperature equal to or higher than the substrate temperature. It is desirable to heat treat the film.

In the method of manufacturing a ferroelectric capacitor and the method of manufacturing a ferroelectric memory device according to the present invention, the first electrode (and further the second electrode) is hardly oxidized at room temperature, and the polarization fatigue characteristic of the capacitor is reduced. A metal or metal oxide formed of a conductor such as Ir to be improved and deposited on the first electrode by a sputtering method or a vacuum evaporation method has a film thickness of 0.5 or more.
A thin film of titanium or the like as thin as 5.0 to 5.0 nm, and a metal oxide such as PbO is deposited on the thin film at a substrate temperature of 400 ° C. or more, particularly to a thickness of 0.5 to 5.0 nm by a sputtering method or the like. And an oxide film (for example, P
(bTiO ₃ film) is preferably formed. Further, lead zirconate titanate, which is a constituent material of the ferroelectric film, is preferably deposited on the oxide film by a sputtering method or the like at a substrate temperature of 600 to 700 ° C. Note that a barrier layer such as TiN is preferably provided below the first electrode to prevent diffusion of the constituent elements of the capacitor.

[0015]

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

First, referring to FIG. 3, a ferroelectric capacitor CAP having a PZT thin film 17 formed by a method according to the present invention, and a semiconductor device incorporating the same, for example, a memory cell M of a dynamic RAM as a volatile storage element. -The configuration of the CEL will be schematically described. However, in FIG. 3, the insulating film made of SiO ₂ or the like is not shown.

In this device, for example, an N ⁺ -type source region 3 and an N ⁺ -type drain region 4 are formed on a P ⁻ -type silicon substrate 1 by impurity diffusion, and a gate oxide film 5 is interposed between these two regions. To provide a transfer gate TR. The bit line BL is connected to the drain region 4.

The capacitor CAP is of a so-called stack type, and has a polysilicon layer 30-T buried in a contact hole formed in a source region 3 and an insulating film.
Barrier layer 20-Ir made of iN, TaN, RuO ₂ or the like
The lower electrode 6 composed of a PZT ferroelectric film 17 and the upper electrode 18 composed of an Ir layer are connected on the lower electrode 6.
Are sequentially laminated. In such a structure, Ir
PbTiO ₃ as a crystal nucleus on the lower electrode 6 composed of a layer
Is characterized in that the PZT film 17 is crystallized in a perovskite structure by sputtering PZT thereon.

Next, a method of manufacturing the ferroelectric capacitor CAP of FIG. 3 will be described with reference to FIGS. In this manufacturing method, basically, Ti having a reduced film thickness of about 2 nm is deposited on a substrate provided with a lower electrode such as Ir by a sputtering method or a vapor deposition method, and only PbO is deposited at an initial stage of sputtering to form PbTiO _3. Is formed on the substrate surface as an initial nucleus, and then a step of depositing crystalline PZT is performed.

First, in step 1, a 200 nm-thick silicon oxide film 10 is formed on a Si substrate 1 by thermal oxidation. This silicon oxide film 10 forms an interlayer insulating film. Note that other elements constituting the memory cell such as the transfer gate TR and the poly-Si layer 30 shown in FIG. 3 are omitted in the drawing, and only the process of forming the capacitor CAP is shown.

Next, in step 2, an Ir thin film 6 having a thickness of 100 nm is formed on the silicon oxide film 10 formed in step 1 by an electron beam heating evaporation method or a sputtering method. In this case, a barrier layer 20 made of TiN, TaN, RuO ₂ or the like may be formed on the poly-Si layer 30 as shown in FIG. 3 as a base layer in advance.

Next, in step 3, a 2 nm-thick Ti31 film is deposited on the Ir thin film 6 formed in step 2 at room temperature by an electron beam heating evaporation method in a vacuum.

The Ti / Ir / SiO ₂ / Si structure formed in these steps 1 to 3 is used as a substrate.

Next, in step 4, PbO 32 is deposited to a thickness of 2 nm on the Ti thin film 31 by a sputtering method using a PbO ceramic target or a reactive sputtering method using a Pb target. This deposition temperature is equal to or higher than the crystallization temperature of PbTiO _3.
Increase to 0 ° C or higher. As shown in FIG. 4, the formation temperature of the crystallization nucleus composed of PbTiO ₃ is determined by observation using an X-ray diffraction spectrum (XRD).
At 0 ° C. or more, particularly at 500 ° C. or more, the formation of PbTiO ₃ is remarkably observed (however, FIG.
Was used, but the same applies to Ir). Thus, as in step 5, the PbTiO ₃ film 33 as a crystal nucleus is formed on the Ir thin film 6.
To form

Next, the PbTiO ₃ 33 formed in step 5
Above, in step 6, Pb (T, Zr) O ₃ target is formed by reactive sputtering using Pb (T, Zr) O ₃ target.
(i, Zr) O ₃ 34 is sputtered, and Pb (Ti, Zr)
An O ₃ thin film 17 is deposited. The actual temperature of the substrate is 600
C. to 700.degree. In this step, since the PbTiO ₃ 33 formed in Steps 4 and 5 becomes a perovskite crystal nucleus, the deposited particles 17A of the Pb (Ti, Zr) O ₃ thin film 17 grow in a columnar shape. In this case, even if the sputtering method is used, PbO does not evaporate from Pb (Ti, Zr) O ₃ and is well deposited by the underlying crystal nuclei.

In step 6, Pb (Ti, Zr) O ₃
With the growth of the thin film 17, PbTiO ₃ 33 becomes Pb (T
It disappears by reacting with i, Zr) O ₃ 34, and the Pb (Ti, Zr) O ₃ thin film 17 is formed as a single layer as in Step 7.

Next, in step 8, Pb (Ti, Z
r) The O ₃ thin film 17 is subjected to a heat treatment in oxygen at 650 ° C. × 1 hour. This process compensates for oxygen defects during sputtering.

Next, in step 9, for example, Ir is deposited by sputtering or electron beam heating in vacuum.
An upper electrode 18 is formed.

Next, in step 10, the capacitor constituting layer is patterned by dry etching.

Then, a heat treatment in oxygen at 500 ° C. is performed to recover the sputtering damage of the side wall 17 B of the Pb (Ti, Zr) O ₃ layer 17.

As described above, according to the present embodiment, when manufacturing a PZT ferroelectric capacitor CAP, in order to form a PZT thin film having good crystallinity by sputtering, Ti deposition on an electrode is performed. PbO deposition-
After specifying the process flow of Pb (Ti, Zr) O ₃ deposition and its conditions, depositing extremely thin Ti33 on the surface of the electrode 6, PbO32 is deposited thereon at a substrate temperature higher than the crystallization temperature of PbTiO _3. Let there be PbTiO ₃
33, and subsequently formed Pb (Ti, Z
r) It is characteristically used as a crystal nucleus of the perovskite phase of O ₃ 17.

Therefore, when forming the PZT thin film 17 by sputtering, the PbTiO ₃ by PbO sputtering on the Ti film 31 is used.
Since 33 is formed in advance as a crystal nucleus and PZT can be deposited and grown on the perovskite crystal having a columnar structure on this PbTiO ₃ , even if the electrode 6 is formed of a substance other than Pt, the target is formed thereon. PZT thin film 17 with crystal structure
Can be reliably formed, and a sputtering method can be applied. Therefore, a uniform thin film can be obtained without being affected by the surface of the base, and mass productivity can be improved.
When Ir is used for the lower electrode, polarization fatigue becomes difficult, and the fatigue characteristics are improved.

Next, as described above, the PbTiO ₃ film 33
The electrical characteristics of the PZT thin film formed on the Ir electrode 6 with nuclei and the PZT thin film formed on the Ir electrode without nuclei are compared.

First, FIG. 5 shows IV characteristics. According to this data, the leakage current value of the PZT thin film formed on the Ir electrode increases as the applied voltage increases.
The leakage current value of the PZT thin film formed on the Ir electrode with the O ₃ nucleus does not depend on the applied voltage and is almost constant. The leakage current value when 4 V is applied is about 3 × 10 ⁻⁸ A / cm ² for the Ir electrode with PbTiO ₃ nucleation, but about 1 × 10 ⁻⁴ A / cm ² for the Ir electrode without nucleation.
cm ² or more. It is clear that the nucleation significantly improved the IV characteristics. When a Pt electrode is used, the leakage current value is about 1 × 10 when 4 V is applied.
^-5 A / cm ² , indicating that a large leakage current exists.

FIG. 6 shows a hysteresis curve measured at a maximum voltage of 5 V for a PZT thin film formed on a nucleated Ir electrode. As is clear from this data, a remanent polarization density of 200 fC / μm ² or more was obtained on average. On the other hand, PZT formed on Ir electrode without nucleation
In the case of a thin film, the polarization characteristics deteriorated due to the leakage current, and sometimes the measurement was impossible.

A capacitor C for forming a PZT thin film 17 on the Ir electrode 6 on which the PbTiO ₃ film 33 is nucleated.
It is desirable to manufacture the AP under the following conditions.

The process flow conditions (1) deposited and vacuum deposition of Ti31 onto the substrate, or Ar by sputtering-ring method, Ti thickness: 0.5～5.0Nm (more favorable Mashiku 1.5 If it is too thin, nucleation becomes difficult, and if it is too thick, aggregation (segregation) of Ti tends to occur. · Deposition temperature: 200 ° C. or less (2) PbO32 deposition-(Ar + O ₂₎ by reactive sputtering-ring method Substrate temperature: 400 ° C. or higher (the crystallization temperature or more PbTiO ₃₎ (preferably four hundred to five 00 ° C.) -PbO thickness: 0.5 to 5.0 nm (more preferably 1.5 to 2.5 nm). If it is too thin, nucleation becomes difficult, and if it is too thick, aggregation (segregation) tends to occur. (3) Pb (Ti, Zr) O ₃ · (Ar + O ₂ ) deposition of reactive sputtering 17 ・ Substrate temperature: 600 to 700 ° C. (perovskite crystal growth temperature) ・ Target: Pb (Ti, Zr) O ₃ or Pb (Ti, Zr) O ₃ containing additives such as La, Nb, Fe, Er, etc. * The above “temperature” is the temperature of the substrate.

FIG. 7 shows that Ir / PZT / PbO / Ti /
7 shows a comparison of polarization fatigue characteristics of each of the PZT capacitors having Ir, Ir / PZT / Ir, and Pt / PZT / Pt structures.

FIG. 7 shows that in a capacitor having a Pt / PZT / Pt structure using Pt for the lower and upper electrodes, 2
A sharp decrease in polarization characteristics is observed in the inversion of × 10 ⁵ times or more. Further, even when Ir is used for the lower and upper electrodes, the present invention is not applied, and in the case of a capacitor having an Ir / PZT / Ir structure in which PZT is formed on the Ir electrode by a sputtering method, similarly. A sharp decrease in polarization characteristics is observed at 2 × 10 ⁵ or more inversions. However, Ir
In the capacitor of the present embodiment having the / PZT / PbO / Ti / Ir structure, no decrease in polarization characteristics is observed up to 2 × 10 ⁹ times.

As described above, it is apparent that the capacitor of this embodiment using the nucleated Ir electrode has a stable remanent polarization density (Pr) at the time of polarization reversal and is very superior to other capacitors. It is. This is considered to be attributed to the oxidation resistance of Ir metal and the like.

Next, a method of manufacturing a semiconductor device incorporating the capacitor obtained by this embodiment, for example, a memory cell M-CEL (for example, a stack type) of a dynamic RAM which is a volatile memory will be described.

First, as shown in FIG. 8, a field oxide film 2 is formed on a P ^- type silicon substrate (wafer) 1 by selective oxidation.
To form a gate oxide film 5 by a thermal oxidation method and a polysilicon word line WL by a chemical vapor deposition method, respectively, and further, an N ⁺ -type source region 3 and a drain region by thermal diffusion of an N-type impurity such as As. 4 are formed.

Then, a contact hole 12 is formed on the source region 3 by photolithography with respect to the SiO ₂ insulating layer 40 deposited on the entire surface by the chemical vapor deposition method.

Next, as shown in FIG. 9, a barrier layer 20 made of a TiN thin film is formed so as to be joined to the source region 3 in the contact hole 12. In addition, the barrier layer 2
Poly Si may be buried in the contact hole below 0.

Next, as shown in FIG. 10, a lower electrode having the Ir layer 6 is formed to a thickness of 100 nm on the barrier layer 20 by sputtering or vacuum evaporation.

Next, as shown in FIG.
An i-layer 31 is deposited to a thickness of 2 nm.

Next, as shown in FIG. 12, PbO 32 was deposited on the Ti layer 31 at 460 ° C. by reactive sputtering.
The PbTi is deposited at the above deposition temperature, and as shown in FIG.
A crystal nucleus composed of the O ₃ layer 33 is formed.

Next, as shown in FIG. 14, PbTiO ₃ 3
On the 3, Pb (Ti, Zr) O ₃ Pb by a reactive sputtering method using a target (Ti, Zr) O ₃
34, and a Pb (Ti, Zr) O ₃ thin film 17 is deposited. The actual temperature of the substrate is between 600C and 700C. The particles 17A of the deposited Pb (Ti, Zr) O ₃ thin film 17 grow in a columnar shape.

In this case, the Pb (Ti, Zr) O ₃ thin film 1
With the growth of 7, PbTiO ₃ becomes Pb (Ti, Zr)
It disappears by reacting with O ₃ 34, and as shown in FIG.
The i, Zr) O ₃ thin film 17 is formed as a single layer.

The Pb (Ti, Zr) O ₃ thin film 17
650 ° C. × 1 hour heat treatment in oxygen.
This process compensates for oxygen defects during sputtering.

Next, as shown in FIG. 16, for example, I sputtering is performed by a vapor deposition method using an electron beam heating method in a vacuum.
An upper electrode 18 is formed.

Next, as shown in FIG. 17, the capacitor constituting layers 18, 17 and 6 are patterned by dry etching.

Then, a heat treatment in oxygen at 500 ° C. is performed to recover the sputtering damage of the side wall 17 B of the Pb (Ti, Zr) O ₃ layer 17.

Although the embodiment of the present invention has been described above, the above-described embodiment 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,
Pt, Pd, Pd, as well as Ir, as long as they are hardly oxidized, are conductors at room temperature, and do not contain Ti.
t-Pd alloy, Cr, Ni, Ni-Cu alloy, Ru, R
It may be uO ₂ , TiN, TaN, IrO ₂ , SrRuO ₃ or the like.

Although Ti was used as a nucleating substance deposited on the surface of this electrode, Zr, Pb, Sr, B
one or one of the elements a, La, Zn, Nb and Fe
One or more species or oxides thereof can be deposited on the electrode. For example, TiO _X other than metal Ti, the use of metal Pb or PbO, on this, with respect to Ti is PbO
It is possible to deposit TiO _x on Pb and PbO.

In the above-described embodiment, the formation of a thin film by a sputtering method has been described as an example. However, a film can be similarly formed by a CVD method or a combination of a sputtering method and a CVD method.

Among the usable metals, La, Zn,
Nb and Fe are elements that can be added to the ferroelectric film. T
i, Zr and Pb are the main components of PZT, and Sr and B
a is the main component of BSTO ((Ba, Sr) TiO ₃ ).

In order to deposit the metal or its oxide, Ti, Zr, Pb, Sb may be deposited not only by the sputtering method but also by an electron beam heating type deposition method in a high vacuum.
depositing r, Ba, La, Zn, Nb or Fe;
Alternatively, a method of naturally oxidizing in an oxygen-containing environment (for example, in the air) after the deposition is also possible.

In this case, among them, Ti is an extremely active substance, and the deposit formed by the evaporation method of the electron beam heating method is oxidized by the residual oxygen in the evaporation chamber. Absent.

Since the effect of the nucleation described above can be expected regardless of the thickness of the electrode layer, the thickness of the electrode layer is 5 nm.
It is good as above.

The electrode structure is a nucleation material layer / electrode layer / barrier layer, and the barrier layer below the electrode is a poly-Si conductive layer in a contact hole provided in an insulating layer made of, for example, an SiO ₂ layer thereunder. A structure to be joined to the layers is conceivable. The electrode structure of the nucleating substance layer / electrode layer / barrier layer that can be applied is, for example, TiO _x / Ir / TiN.
i or TiO _x / Ir / TiN, Ti or TiO _x / P
t / RuO ₂ , Ti or TiO _x / Pt / IrO ₂ , T
i or TiO _x / Ni / TiN, Zr or ZrO _x / P
t / RuO _{2 and the} like. Further, it is not always necessary to provide a barrier layer separately from the electrode, in which case, Ti or TiO _x / IrO ₂ , Ti or TiO _x / RuO ₂ , T
i or TiO _x / TiN, Ti or TiO _x / ITO
(Indium tin oxide).

The material of the ferroelectric film that can be used is P
In addition to ZT, PZT, BSTO ((Ba, Sr) TiO ₃ ), which is obtained by adding Nb, Zr, Fe, etc. to PZT, PLT
((Pb, La) _x (Ti, Zr) _1-x O ₃ ) or the like.

The ferroelectric film according to the present invention is, for example, shown in FIG.
Can be applied to the device having the Ir / PZT / Ir / barrier layer / poly-Si structure capacitor (stacked capacitor), but is not limited thereto, and the above-mentioned stacked capacitor is provided on the SiO ₂ film. A structure in which the lower electrode of the lever is extended to connect to the source region of the transfer gate may be used, or the present invention is applicable to a capacitor having a structure in which a capacitor is incorporated in a so-called trench instead of a stack type. .

[0065]

According to the present invention, as described above, at least one kind of metal element constituting the ferroelectric film or its oxide (for example, titanium) is deposited on the first electrode.
Forming a metal or metal oxide thin film (for example, a titanium thin film); and oxidizing at least one metal element constituting the ferroelectric film, the metal element being different from the metal or metal oxide thin film. (Eg, lead oxide: Pb
Depositing O) on the metal or metal oxide thin film, and the deposited metal oxide (eg, lead oxide) and a metal element (eg, titanium) of the metal or metal oxide thin film.
(For example, lead titanate: PbTi)
Generating O ₃ ) on the first electrode, and forming the ferroelectric film (eg, lead zirconate titanate) on the oxide film using the generated oxide film as a crystal nucleus. : Depositing Pb (Ti, Zr) O ₃ ) to form the ferroelectric film, and forming the second electrode on the ferroelectric film. At the time of forming a ferroelectric film by sputtering or the like, a ferroelectric crystal can be deposited and grown in a desired structure on the crystal nucleus, regardless of the material of the first electrode. Can reliably form a ferroelectric film having a crystalline structure,
In addition, since the sputtering method can be applied, a uniform thin film can be obtained without being affected by the surface of the base, and the mass productivity is improved. When Ir is used for the first and second electrodes, polarization fatigue is less likely to occur, and fatigue characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a flow of manufacturing a ferroelectric capacitor according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a manufacturing flow of the capacitor following FIG. 1;

FIG. 3 is a schematic sectional view of a semiconductor device incorporating the capacitor.

FIG. 4 is an X-ray diffraction spectrum diagram of a film according to a substrate temperature when a PZT thin film of the capacitor is formed.

FIG. 5 is an IV characteristic diagram of a PZT thin film formed on each electrode.

FIG. 6 is a hysteresis curve diagram of a polarization value of a PZT thin film of a ferroelectric capacitor according to the present invention.

FIG. 7 is a graph showing the relationship between the remanent polarization density and the number of times of polarization reversal of a PZT capacitor using various electrode materials.

FIG. 8 is an enlarged sectional view showing one process step of a method for manufacturing a memory cell of a dynamic RAM incorporating a ferroelectric capacitor according to the present invention.

FIG. 9 is an enlarged cross-sectional view showing another process step of the memory cell manufacturing method.

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

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

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

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

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

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

FIG. 16 is an enlarged cross-sectional view showing another process step of the manufacturing method of the memory cell.

FIG. 17 is an enlarged cross-sectional view showing yet another process step of the memory cell manufacturing method.

[Explanation of symbols]

1 ... silicon substrate 3 ... N ⁺ -type source region 4 ... N ⁺ -type drain region 6, 18 ... Ir electrodes 10 ... SiO ₂ film 17 ... ferroelectric film (PZT thin film ) 17A ... particles (columnar structure) 20 ... barrier layer 30 ... poly-Si layer 31 ... Ti layer _{32 ··· PbO 33 ··· PbTiO 3 34} ··· Pb (Ti, Zr) O ₃ CAP: Ferroelectric capacitor TR: Transfer gate M-CEL: Memory cell WL: Word line (gate electrode) BL: Bit line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/8247 29/788 29/792 (72) Inventor Yukio Fukuda 2355 Kihara, Miura-mura, Inashiki-gun, Ibaraki Japan Shares of Texas Instruments Japan Limited In-house (72) Inventor Numata Inui 2355 Kihara, Miura-mura, Inashiki-gun, Ibaraki Prefecture Within Texas Instruments Instruments Co., Ltd.

Claims (5)

[Claims] When manufacturing a ferroelectric capacitor including a first electrode, a ferroelectric film on the first electrode, and a second electrode on the ferroelectric film, Depositing at least one kind of metal element of the constituent metal element of the ferroelectric film or an oxide thereof on the first electrode;
Forming a metal or metal oxide thin film; and forming an oxide of a metal element that is at least one metal element of the metal elements constituting the ferroelectric film and is different from the metal or metal oxide thin film. Depositing the deposited metal oxide and a metal element of the metal or the metal oxide thin film on the first electrode; and forming the oxide film on the first electrode. A step of depositing a constituent material of the ferroelectric film on the oxide film thus formed to form the ferroelectric film; and a step of forming the second electrode on the ferroelectric film. A method for manufacturing a ferroelectric capacitor. 2. The first electrode made of iridium,
In manufacturing the ferroelectric capacitor constituted by the ferroelectric film made of lead zirconate titanate on the first electrode and the second electrode made of iridium on the ferroelectric film, The titanium, which is a metal element constituting the ferroelectric film, is used as the first metal.
Forming a titanium thin film by depositing on the electrode of the above, a step of depositing an oxide of lead, which is a metal element constituting the ferroelectric film, on the titanium thin film, Forming a lead titanate film comprising titanium of the titanium thin film on the first electrode; and using the generated lead titanate film as a crystal nucleus, lead zirconate titanate on the lead titanate film. 2. The method according to claim 1, further comprising: depositing the ferroelectric film to form the ferroelectric film; and forming the second electrode on the ferroelectric film. 3. 3. The sputtering method, wherein the metal or the metal oxide thin film or the titanium thin film, the metal oxide or the lead oxide, the constituent material of the ferroelectric film, or the lead zirconate titanate are respectively used. The manufacturing method according to claim 1, wherein the deposition is performed by a vapor deposition method or a vacuum evaporation method. 4. The oxide film or the oxide film obtained by depositing the metal or metal oxide thin film or the titanium thin film and then obtaining an oxide of a metal element different from the metal or metal oxide thin film or the titanium thin film. The substrate is deposited by a sputtering method at a substrate temperature equal to or higher than the crystallization temperature of the lead titanate film, and further, the constituent material of the ferroelectric film or the lead zirconate titanate is deposited by a sputtering method at a substrate temperature equal to or higher than the substrate temperature. 4. The method according to claim 3, wherein said deposited film is heat-treated. 5. A method for manufacturing a ferroelectric memory device, comprising a step of manufacturing the ferroelectric capacitor in a memory cell by the manufacturing method according to claim 1.