JP2009071144A - Method of manufacturing ferroelectric memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a ferroelectric film with superior characteristics. <P>SOLUTION: The method of manufacturing the ferroelectric memory having a ferroelectric film sandwiched between a first electrode and a second electrode; includes the steps of: forming an iridium film 51a over a substrate; forming a first platinum film 531a on the iridium film 51a; forming the first electrode 5a having the first platinum film 531a and the iridium film 51a including an iridium oxide film 52a by heat-treating the substrate where the first platinum film 531a is formed in an oxygen atmosphere and then thermally diffusing oxygen in the surface layer of the iridium film 51a through the first platinum film 531a to make the surface layer into the iridium oxide layer 52a; forming a ferroelectric film 6a on the first electrode 5a; and forming the second electrode 7a on the ferroelectric film 6a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a ferroelectric memory.

A ferroelectric memory (FeRAM) is a non-volatile memory capable of low voltage and high speed operation utilizing spontaneous polarization of a ferroelectric material, and a memory cell can be composed of one transistor / 1 capacitor (1T / 1C). Therefore, since it can be integrated in the same manner as a DRAM, it is expected as a large-capacity nonvolatile memory. Here, as the ferroelectric material, a perovskite type oxide such as lead zirconate titanate (Pb (Zr, Ti) O ₃ : PZT) or a bismuth layer like bismuth strontium tantalate (SrBi ₂ TaO ₉ : SBT) is used. Compounds and the like.

  By the way, the crystal orientation is extremely important in order to maximize the ferroelectric properties of the ferroelectric material. For example, since PZT acquires a larger amount of spontaneous polarization, a composition containing more Ti (titanium) than Zr (zirconium) is usually adopted. In this composition range, PZT belongs to a tetragonal crystal, and the maximum amount of polarization can be obtained by orienting the cZ axis which is the spontaneous polarization axis. However, it is very difficult to actually perform c-axis orientation, and an a-axis orientation component perpendicular to the c-axis is generated, and this a-axis orientation component does not contribute to polarization inversion, so that the ferroelectric characteristics are degraded.

  Therefore, a method is considered in which the crystal orientation of the PZT is changed to the (111) orientation so that all crystal components contribute to the polarization inversion, and the charge extraction efficiency is improved as compared with the case of the c-axis orientation. In order to align the crystal orientation of PZT to (111), the crystal orientation of the lower electrode serving as the base is important. However, the material of the lower electrode is a precious metal such as iridium or platinum because of its thermal and chemical stability. It is limited to.

  Among precious metals, platinum is regarded as the most promising material for the lower electrode because it has a lattice constant close to that of a PZT-based ferroelectric material and provides good interface matching. However, it is difficult to directly connect platinum to a conductive portion such as a wiring using platinum as a lower electrode. That is, since the ferroelectric material is an oxide as described above, it deteriorates when it is reduced. On the other hand, when the wiring and the conductive part are generally oxidized, the resistance increases. However, since platinum easily permeates oxygen, oxygen contained in PZT permeates the lower electrode and oxidizes the conductive part, which increases resistance, and PZT is deoxygenated and PZT is reduced at that time. Inconvenience such as deterioration occurs.

  In order to avoid such an inconvenience, it is conceivable to provide an oxygen-barrier barrier metal that does not transmit oxygen on the base of the lower electrode (platinum). Such barrier metal uses TiN or TiAlN (titanium aluminum nitride) containing Ti which has strong self-orientation in addition to the barrier property, so that the crystal orientation of the lower electrode and the ferroelectric film can be changed. It is also expected to improve. However, although materials such as TiN and TiAlN are difficult to permeate oxygen, if heat treatment is performed in an oxygen atmosphere in the process of forming a ferroelectric film, oxygen diffusion occurs between the lower electrode and the barrier metal. The metal is oxidized and becomes high resistance.

Therefore, a method has been considered in which an iridium film is further provided on the barrier metal, and a lower electrode made of an iridium film and a platinum film is provided. Iridium functions well as a barrier film between the ferroelectric film and the conductive portion because iridium oxide, which is an oxide thereof, has oxygen barrier properties and conductivity. However, since the iridium film has poor adhesion with the platinum film, when a ferroelectric film, an upper electrode, or the like is formed on the platinum film, stress due to a difference in lattice constant or the like accumulates in the surface direction of the film, May cause delamination. Therefore, Patent Document 1 discloses a method in which a lower electrode having a three-layer structure having an iridium oxide film between an iridium film and a platinum film is used to increase the adhesion between the iridium film and the platinum film by the iridium oxide film.
JP 2003-282831 A

  However, in the method of Patent Document 1, it is difficult to control the crystal orientation of Pt. That is, even if a barrier metal made of, for example, TiN or TiAlN is formed in a good (111) orientation and an iridium film is formed in a (111) orientation by matching the crystal structure thereon, iridium oxide is different from iridium. Since it has a rutile type crystal structure, it essentially does not lattice match with the iridium (111) plane. As a result, the orientation of iridium oxide becomes random. Therefore, the platinum film formed on the iridium oxide film cannot reflect the (111) orientation of the barrier metal. Since the crystal orientation of the platinum film is determined only by the self-orientation of platinum, it is difficult to highly orient the (111) orientation, and the ferroelectric film thereon can be sufficiently (111) oriented. could not.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a good ferroelectric memory having a good ferroelectric film.

  A method for manufacturing a ferroelectric memory according to the present invention is a method for manufacturing a ferroelectric memory having a ferroelectric film sandwiched between a first electrode and a second electrode, wherein an iridium film is formed above the substrate. Forming the first platinum film on the iridium film, heat-treating the substrate on which the first platinum film is formed in an oxygen atmosphere, and passing through the first platinum film to form the iridium film. Forming a first electrode including the first platinum film and the iridium film including the iridium oxide layer by thermally diffusing oxygen in the surface layer, and forming the first electrode on the first electrode. Forming a ferroelectric film and forming a second electrode on the ferroelectric film.

  In this way, since the first platinum film is formed on the iridium film, the crystal orientation of the iridium film can be reflected in the crystal orientation of the first platinum film. Therefore, the crystal orientation of the first platinum film can be controlled by controlling the crystal orientation of the iridium film. Therefore, a first platinum film having a desired crystal orientation can be formed, and a ferroelectric film having a desired crystal orientation can be formed on the first platinum film by reflecting the crystal orientation. In this manner, a ferroelectric film having excellent ferroelectric characteristics can be formed, and a ferroelectric memory having excellent characteristics can be manufactured.

  In addition, since the iridium oxide layer is formed between the iridium film and the first platinum film after the first platinum film is formed, the first platinum film can be formed in a desired crystal orientation and is oxidized. The iridium layer can increase the adhesion between the iridium film and the first platinum film. Therefore, it is possible to prevent the first platinum film and the iridium film from being peeled off during the process after forming the iridium oxide layer or during use of the manufactured ferroelectric capacitor.

If a ferroelectric film made of Pb (Zr, Ti) O ₃ (lead zirconate titanate, PZT) is formed, PZT is well known as a ferroelectric material. A dielectric film can be formed. Moreover, since PZT has a lattice constant close to that of platinum, good interface matching can be obtained between the ferroelectric film and the lower electrode.

In the step of forming the first electrode, after forming the iridium oxide layer, a second platinum film is formed on the first platinum film to form a first electrode having the second platinum film. It is preferable to do.
In this way, the second platinum film can be formed in a desired crystal orientation using the first platinum film as a seed. Therefore, the first platinum film only needs to have a minimum thickness that can control the crystal orientation of the second platinum film, and can be made thinner than the case where the second platinum film is not formed. Therefore, by forming the first platinum film thinly, oxygen can permeate the first platinum film satisfactorily, and oxygen can be diffused favorably in the surface layer of the iridium film. In this way, a good iridium oxide layer can be formed.

In the step of forming the first electrode, the first platinum film is preferably formed to a thickness of 5 nm to 50 nm.
The first platinum film shrinks when the iridium oxide layer is formed or when a thermal process in a later process causes the atoms to thermally vibrate so that the crystal structure becomes dense. By setting the thickness of the first platinum film to 5 nm or more, it is possible to prevent the first platinum film from being broken due to shrinkage. In addition, when the thickness of the first platinum film is 50 nm or less, the amount of oxygen that permeates the first platinum film when forming the iridium oxide layer can be made sufficient.

In the step of forming the first electrode, the second platinum film is preferably formed by a sputtering method.
According to the sputtering method, it is possible to form the second platinum film having a dense crystal structure as compared with the vapor deposition method or the like, and it is possible to form the second platinum film having a favorable crystal orientation.

In the step of forming the first electrode, it is preferable to heat-treat the substrate on which the first platinum film is formed at a temperature of 550 ° C. or higher.
If the substrate is heated to a temperature of 550 ° C. or higher, the first platinum film has a dense crystal structure due to thermal vibration of its atoms and a good crystal orientation.

In the step of forming the iridium film, it is preferable to form a (111) -oriented base conductive film with a self-orienting metal material above the substrate and to form the iridium film on the base conductive film. .
In this way, the iridium film can be formed in a (111) orientation reflecting the crystal orientation of the underlying conductive film, and the first platinum film can be reflected by reflecting the crystal orientation of the iridium film ( 111) orientation. Further, the ferroelectric film can be formed in the (111) orientation reflecting the crystal orientation of the first platinum film. Since the ferroelectric film with the (111) orientation has a good charge extraction rate, it has excellent ferroelectric characteristics.

Hereinafter, although one embodiment of the present invention is described, the technical scope of the present invention is not limited to the following embodiment. In the description, various structures are illustrated using drawings, but in order to show the characteristic parts of the structures in an easy-to-understand manner, the structures in the drawings may be shown with different dimensions and scales from the actual structures. is there.
[Ferroelectric memory]

  First, the configuration of an example of a ferroelectric memory manufactured by the manufacturing method of the present invention will be described.

  FIG. 1 is a cross-sectional configuration diagram showing the main part of a ferroelectric memory 1 of this example. As shown in FIG. 1, the ferroelectric memory 1 has a stack type structure, and includes a base 2 having a transistor 22, a base conductive film 3 provided on the base 2, and a base conductive film 3. The ferroelectric capacitor 4 is provided.

The base 2 includes a transistor 22 provided on a silicon substrate (substrate) 21 made of, for example, single crystal silicon, and a base insulating film 23 made of SiO ₂ provided so as to cover the transistor 22. . An element isolation region 24 is provided on the surface layer of the silicon substrate 21, and the space between the element isolation regions 24 corresponds to one memory cell.

  The transistor 22 includes a gate insulating film 221 provided on the silicon substrate 21, a gate electrode 222 provided on the gate insulating film 221, source regions 223 provided on both sides of the gate electrode 222 on the surface of the silicon substrate 21, and The drain region 224 and sidewalls 225 provided on the side surfaces of the gate electrode 222 are configured. In this example, a first plug 25 that is electrically connected to the source region 223 is provided, and a second plug 26 that is electrically connected to the source region 223 is provided to the drain region 224.

  The first plug 25 and the second plug 26 are made of a conductive material such as W (tungsten), Mo (molybdenum), Ta (tantalum), Ti, or Ni (nickel). In this example, the first plug 25 is electrically connected to a bit line (not shown), and the source region 223 is electrically connected to the bit line through the first plug 25.

  The base conductive film 3 includes a conductive film 31 and an oxygen barrier film 32 that are sequentially formed on the base insulating film 23 and the second plug 26. The conductive film 31 is made of a conductive material such as TiN, for example, and its crystal orientation is (111) orientation. The oxygen barrier film 32 is made of a conductive material having an oxygen barrier property such as TiAlN, TiAl, TiSiN, TiN, TaN, TaSiN, and has a crystal orientation of (111). Ti is a metal particularly excellent in self-orientation, and the conductive film 31 and the oxygen barrier film 32 are preferably made of the above-described conductive material containing Ti.

  The ferroelectric capacitor 4 is formed on the underlying conductive film 3, and a lower electrode (first electrode) 5, a ferroelectric film 6 and an upper electrode (second electrode) 7 are laminated in order from the lower layer. It has become. The lower electrode 5 is electrically connected to the second plug 26 through the oxygen barrier film 32 and the conductive film 31. That is, the lower electrode 5 and the drain region 224 are electrically connected.

  The lower electrode 5 has a configuration in which an iridium film 51, an iridium oxide layer 52, and a platinum film 53 are laminated in order from the lower layer. In this example, the crystal orientation of the iridium film 51 and the platinum film 53 is the (111) orientation. It is known that the adhesion between the iridium film and the platinum film is poor, but the iridium oxide layer 52 functions as an adhesion layer by interposing the iridium oxide layer 52 between the iridium film 51 and the platinum film 53. Thus, no separation occurs between the iridium film 51 and the iridium oxide layer 52 or between the iridium oxide layer 52 and the platinum film 53.

The ferroelectric film 6 is made of a ferroelectric material having a perovskite crystal structure represented by the general formula of ABO ₃ . In the above general formula, A is composed of Pb or a part of Pb substituted with La, and B is composed of Zr or Ti. Also, one or more of V (vanadium), Nb (niobium), Ta, Cr (chromium), Mo (molybdenum), W (tungsten), Ca (calcium), Sr (strontium) and Mg (magnesium) It may be added. As the ferroelectric material constituting the ferroelectric film 6, a known material such as PZT, SBT, (Bi, La) ₄ Ti ₃ O ₁₂ (bismuth lanthanum titanate: BLT) can be used. PZT is preferably used.

  Further, when PZT is used as the ferroelectric material, in order to obtain a larger spontaneous polarization amount, it is preferable to make the Ti content in the PZT larger than the Zr content. Furthermore, when the Ti content in PZT is greater than the Zr content, the crystal orientation of PZT is preferably the (111) orientation in terms of good hysteresis characteristics. In this example, the ferroelectric film 6 made of PZT is adopted, and the crystal orientation of the ferroelectric film 6 is made by setting the crystal orientation of the base conductive film 3, the iridium film 51, and the platinum film 53 to the (111) orientation. The orientation is (111) orientation.

  In this example, the upper electrode 7 is electrically connected to a ground line (not shown), and is composed of a single layer film or a multilayer film in which a plurality of layers are laminated. As the material, Al (aluminum), Ag (silver), Ni (nickel), or the like can be used in addition to the same material as the lower electrode 5 described above. In this example, a multilayer film in which a platinum film, an iridium oxide film, and an iridium film (not shown) are laminated from the lower layer is employed.

  With the above structure, when a voltage is applied to the gate electrode 222 of the transistor 22, an electric field is applied between the source region 223 and the drain region 224 to turn on the channel, and a current flows therethrough. It becomes possible. When the channel is turned on, an electric signal from the bit line electrically connected to the source region 223 is transmitted to the drain region 224 and further to the ferroelectric capacitor 4 electrically connected to the drain electrode 224. Is transmitted to the lower electrode 5. A voltage can be applied between the upper electrode 7 and the lower electrode 5 of the ferroelectric capacitor 4, and charges (data) can be accumulated in the ferroelectric film 6. As described above, the ferroelectric memory 1 can read or write data (charge) by switching the electric signal to the ferroelectric capacitor 4 by the transistor 22.

[Manufacturing Method of Ferroelectric Memory]
Next, an embodiment of a method for manufacturing a ferroelectric memory according to the present invention will be described. In the present embodiment, a method for manufacturing the ferroelectric memory 1 will be described as an example.

  2A to 2E and 3A to 3D are cross-sectional process diagrams illustrating a method for manufacturing the ferroelectric memory 1 according to the present embodiment. In addition, in the figure used for the following description, the principal part is expanded and shown typically.

  First, as shown in FIG. 2A, the base 2 is formed using a known method or the like. Specifically, for example, an element isolation region 24 is formed on a silicon substrate (substrate) 21 by a LOCOS method, an STI method, or the like, and a gate insulating film 221 is formed on the silicon substrate 21 between the element isolation regions 24 by a thermal oxidation method or the like. Form. Then, a gate electrode 222 made of polycrystalline silicon or the like is formed on the gate electrode 222. Then, impurities are implanted into the surface layer of the silicon substrate 21 between the element isolation region 24 and the gate electrode 222 to form doped regions 223 and 224. Then, a sidewall 225 is formed using an etch back method or the like. In this embodiment, the doped region 223 functions as a source region, and the doped region 224 functions as a drain region.

Then, a base insulating film 23 is formed on the silicon substrate 21 on which the transistor 22 is formed by depositing SiO ₂ by, for example, a CVD method. Then, the base insulating film 23 on the source region 223 and the drain region 224 is etched to form a through hole that exposes the source region 223 and a through hole that exposes the drain region 224. Then, in each of these through holes, for example, Ti and TiN are sequentially formed by sputtering to form an adhesion layer (not shown).

  Then, tungsten is formed on the entire surface of the base insulating film 23 including the inside of the through hole by, for example, a CVD method, tungsten is embedded in the through hole, and the upper surface of the base insulating film 23 is polished by a CMP method or the like. Then, tungsten on the base insulating film 23 is removed. In this way, the first plug 25 is embedded in the through hole on the source region 223, and the second plug 26 is embedded in the through hole on the drain region 224. The substrate 2 can be formed as described above.

Next, as shown in FIG. 2B, a conductive film 31 a is formed on the base insulating film 23. Specifically, surface treatment is first performed by exposing the upper surface of the base insulating film 23 to NH ₃ plasma. Thereby, the self-orientation of Ti can be enhanced. Then, Ti is deposited on the base insulating film 23 by using, for example, a CVD method or a sputtering method. Since Ti has a high self-orientation property, a hexagonal close-packed film having a (001) orientation is formed.

  Then, a conductive film 31a made of TiN is formed by nitridation treatment in which this film is subjected to heat treatment (for example, 500 ° C. or more and 650 ° C. or less) in a nitrogen atmosphere. By setting the temperature of the heat treatment to less than 650 ° C., the influence on the characteristics of the transistor 22 is suppressed, and by setting the temperature to 500 ° C. or more, the nitriding treatment can be shortened. Note that the formed conductive film 31a has a (111) orientation reflecting the orientation of Ti in the original metal state.

  Next, as shown in FIG. 2C, a TiAlN film is formed on the conductive film 31a by using, for example, a sputtering method or a CVD method to form an oxygen barrier film 32a. The oxygen barrier film 32a can be formed epitaxially by matching the crystal orientation with the conductive film 31a serving as the base. In other words, the (111) -oriented oxygen barrier film 32a reflecting the crystal orientation of the conductive film 31a can be formed. In this way, the underlying conductive film 3a having the (111) orientation composed of the conductive film 31a and the oxygen barrier film 32a is formed.

  Next, as shown in FIG. 2D, iridium is deposited on the oxygen barrier film 32a by a sputtering method to form an iridium film 51a. The iridium film 51a can be formed by reflecting the underlying crystal orientation, and since the underlying oxygen barrier film 32a has the (111) orientation, it can be formed in the (111) orientation.

  Next, as shown in FIG. 2E, a seed film (first platinum film) 531a made of platinum is formed on the iridium film 51a. As a formation method, a sputtering method, an evaporation method, or the like can be used. According to the sputtering method, a film having a crystal structure denser than that of the vapor deposition method can be formed, so that a film having a favorable crystal orientation can be formed. Further, according to the vapor deposition method, a film having a sparse crystal structure can be formed, so that a film that easily transmits oxygen can be formed. Note that even when formed by a vapor deposition method, the crystal structure can be made dense by thermally oscillating the atoms later by heat treatment, and a favorable crystal orientation can be obtained.

  The thickness of the seed film 531a is preferably 5 nm or more and 50 nm or less. In this embodiment, the seed film 531a is formed to a thickness of 5 nm by sputtering. The seed film 531a can be formed by reflecting the underlying crystal orientation, and since the underlying iridium film 51a has the (111) orientation, it can be formed in the (111) orientation.

  Next, as shown in FIG. 3A, the base 2 (see FIG. 1) on which the seed film 531a is formed is heat-treated in an oxygen atmosphere, and oxygen is thermally diffused through the seed film 531a to the surface layer of the iridium film 51a. Thus, the surface layer is an iridium oxide layer 52a. For the heat treatment, furnace annealing using a resistance heating type electric furnace or the like, infrared heating type lamp annealing, or the like can be used.

  In this embodiment, the substrate 2 is heated to a temperature of about 600 ° C. using furnace annealing to perform heat treatment. Since the thickness of the seed film 531a is 50 nm or less, a sufficient amount of oxygen can be diffused to the iridium film 51a side through the seed film 531a. In addition, since the heat treatment for a sufficient time can be performed by furnace annealing with little restriction on the heating time, the surface layer of the iridium film 51a can be uniformly thermally oxidized, and the iridium oxide layer 52a can be formed satisfactorily. . Since iridium oxide has an oxygen barrier property, when the iridium oxide layer is formed to a thickness corresponding to the oxygen atmosphere, oxygen does not diffuse further to the iridium film side. Therefore, the thickness of the iridium oxide layer can be controlled by the oxygen concentration in the oxygen atmosphere, the heating temperature, and the heating time. In this way, for example, an iridium oxide layer 52a having a thickness of about 5 nm is formed.

  In addition, since the substrate 2 is heated to 550 ° C. or higher, the atoms of the seed film 531a are thermally vibrated to repair the crystal defects and form a dense crystal structure, and the crystal orientation of the seed film 531a is improved. Here, since the thickness of the seed film 531a is set to 5 nm or more, the seed film 531a is prevented from being broken by contraction when a dense crystal structure is formed.

In general, iridium oxide has a rutile type crystal structure or an amorphous crystal structure, unlike iridium and platinum. For this reason, the surface structure of the (111) orientation of the lower layer film is blocked by the iridium oxide layer.
However, in the method of the present invention, before the iridium oxide layer 52a is formed, the seed film 531a is formed in a (111) orientation above the portion where the iridium oxide layer 52a is formed. The crystal orientation of the lower layer (iridium film 51a) side can be transmitted to the upper layer (seed film 531a) side of 52a.

  Next, as shown in FIG. 3B, in this embodiment, a core film (second platinum film) 532a made of platinum is formed to a thickness of 95 nm on the seed film 531a by sputtering. The core film 532a can be formed by reflecting the underlying crystal orientation, and since the underlying seed film 531a has the (111) orientation, it can be formed in the (111) orientation. In this manner, a platinum film 53a composed of the seed film 531a and the core film 532a is formed, and a lower electrode 5a composed of the iridium film 51a, the iridium oxide layer 52a, and the platinum film 53a is formed.

  Next, as shown in FIG. 3C, a ferroelectric film 6a is formed on the lower electrode 5a by depositing a ferroelectric material by a sputtering method or a sol-gel method. In this embodiment, PZT is used as the ferroelectric material, and this is formed by a sol-gel method. The ferroelectric film 6a can be formed by reflecting the underlying crystal orientation. Since the underlying core film 532a has the (111) orientation, the ferroelectric film 6a can be formed in the (111) orientation. In addition, since PZT has a lattice constant close to that of platinum, good interface matching with the platinum film 53a of the lower electrode 5a can be obtained.

Next, as shown in FIG. 3D, the upper electrode 7a is formed on the ferroelectric film 6a by sequentially depositing platinum, iridium oxide, and iridium by using, for example, sputtering or CVD. .
Next, the conductive film 31a, the oxygen barrier film 32a, the lower electrode 5a, the ferroelectric film 6a, and the upper electrode 7a are patterned by using a known resist technique and photolithography technique to form the ferroelectric capacitor 4. (Manufacturing) In this way, the ferroelectric memory 1 shown in FIG. 1 is manufactured.

  According to the manufacturing method of the present invention as described above, since the seed film (first platinum film) 531a is formed on the upper layer side of the iridium oxide layer 52a before the iridium oxide layer 52a, the lower layer of the iridium oxide layer 52a. The crystal orientation on the (iridium film 51a) side can be transmitted to the upper layer (seed film 531a) side. Therefore, by controlling the crystal orientation of the iridium film 51a, the crystal orientation of the platinum film 53a and the ferroelectric film 6a can be controlled. Therefore, the crystal orientation of the ferroelectric film 6a can be improved, and the ferroelectric film 6a having excellent ferroelectric characteristics can be formed. In this manner, the ferroelectric capacitor 3 having excellent hysteresis characteristics can be manufactured, and the highly reliable ferroelectric memory 1 having the same can be manufactured.

  In addition, at least one of iridium, platinum, Ru (ruthenium), Rh (rhodium), Pd (palladium), Os (osmium) or an alloy thereof, or these between the lower electrode 5 and the base conductive film 3 A configuration in which a film made of an oxide is provided is also possible.

  In this embodiment, the platinum film 53a composed of the seed film 531a and the core film 532a is formed. However, the platinum film 53a may be formed only by the seed film 531a. In this case, the seed film is formed thicker, for example, about 50 nm. It is preferable to do.

FIG. 3 is a side sectional view showing a ferroelectric memory according to the manufacturing method of the present invention. It is sectional process drawing which shows the manufacturing method of this invention. It is sectional process drawing which shows the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ferroelectric memory, 2 ... Base | substrate, 21 ... Silicon substrate (substrate), 22 ... Transistor, 3 ... Base conductive film, 4 ... Ferroelectric capacitor, 5, 5a ... lower electrode (first electrode), 51, 51a ... iridium film, 52, 52a ... iridium oxide layer, 53, 53a ... platinum film, 531a ... seed film (first film) (Platinum film), 532a ... core film (second platinum film), 6, 6a ... ferroelectric film, 7, 7a ... upper electrode (second electrode)

Claims (6)

A method of manufacturing a ferroelectric memory having a ferroelectric film sandwiched between a first electrode and a second electrode,
Forming an iridium film above the substrate;
Forming a first platinum film on the iridium film;
The substrate on which the first platinum film is formed is heat-treated in an oxygen atmosphere, and oxygen is thermally diffused to the surface layer of the iridium film through the first platinum film, thereby forming the iridium oxide layer as the surface layer. Forming a first electrode having a platinum film and the iridium film including the iridium oxide layer;
Forming a ferroelectric film on the first electrode;
Forming a second electrode on the ferroelectric film, and manufacturing the ferroelectric memory.   In the step of forming the first electrode, after the iridium oxide layer is formed, a second platinum film is formed on the first platinum film to form a first electrode having the second platinum film. The method of manufacturing a ferroelectric memory according to claim 1.   3. The method of manufacturing a ferroelectric memory according to claim 1, wherein, in the step of forming the first electrode, the first platinum film is formed to a thickness of 5 nm to 50 nm.   4. The method of manufacturing a ferroelectric memory according to claim 2, wherein in the step of forming the first electrode, the second platinum film is formed by a sputtering method.   5. The process according to claim 1, wherein, in the step of forming the first electrode, the substrate on which the first platinum film is formed is heated to a temperature of 550 ° C. or higher. Manufacturing method for ferroelectric memory.   The step of forming the iridium film comprises forming a (111) -oriented base conductive film with a self-orienting metal material above the substrate, and forming the iridium film on the base conductive film. Item 6. The method for manufacturing a ferroelectric memory according to any one of Items 1 to 5.

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