JP4968654B2 - Oxide material, ferroelectric material, and electronic device using the same - Google Patents

Description

  The present invention relates to an oxide material and a ferroelectric material used for an electronic device, and a method for manufacturing the electronic device. More specifically, the present invention can be suitably used for a ferroelectric memory that is a nonvolatile memory. The present invention relates to an oxide material and a ferroelectric material, and an electronic device using such a material.

  In recent years, mobile terminals represented by mobile phones, notebook computers, personal digital assistants (PDAs) and the like have been widely used. Since these portable terminals are generally used by battery drive, various ideas have been made to reduce power consumption and extend the usable time.

  As a means for reducing the power consumption of the portable terminal, it is conceivable to use a memory that does not consume power to hold data in place of a conventional DRAM or SRAM. Specifically, the use of a ferroelectric nonvolatile memory that does not require power for data retention and can be mounted on a small portable terminal has been studied. A ferroelectric nonvolatile memory is a memory that can hold data without consuming electric power by utilizing polarization characteristics of a ferroelectric material.

This ferroelectric nonvolatile memory
・ Lead zirconate titanate (PZT; PbZr _X Ti _1-X O ₃ ) perovskite ferroelectric material (ABO ₃ )
-Bismuth, such as strontium bismastantalate (SBT; SrBi ₂ Ta ₂ O ₉ ), bismaster titanate (BIT; Bi ₄ Ti ₃ O ₁₂ ), bismuth lanthanum titanate (BLT; Bi _4-X La _X Ti ₃ O ₁₂ ) (Bi) Layered perovskite ferroelectric material (BiA _m-1 B _m O _{3m + 3} )
A material having a structure in which a ferroelectric material such as the above is sandwiched between an upper electrode (metal) / ferroelectric thin film / lower electrode (metal) is representative. The structure described above is called an MFM (Metal / Ferroelectric / Semiconductor) structure.

In addition, there is a ferroelectric nonvolatile memory having the following structure using the above-described ferroelectric material.
MFMIS (metal / ferroelectric / metal / insulating layer / silicon, so-called capacitor) structure MFIS (metal / ferroelectric / insulating layer / silicon, so-called transistor) structure

As a conventional ferroelectric nonvolatile memory, Patent Document 1 discloses a ferroelectric device, Patent Document 2 discloses a ferroelectric material and a memory using the same, and Patent Document 3 discloses a ferroelectric device. A semiconductor memory device is disclosed. Patent Document 4 discloses a method for manufacturing a ferroelectric thin film used in a conventional electronic device such as a ferroelectric memory or a ferroelectric capacitor.
JP-A-8-249876 Japanese Patent Laid-Open No. 10-22465 JP-A-11-274429 JP-A-8-264526

However, the above-described conventional ferroelectric materials include
- a bismuth (Bi) layered perovskite ferroelectric material SBT is, BIT and BLT residual polarization (Pr) is 10 [mu] C / cm ² or less and the small-bismuth (Bi) layered perovskite ferroelectric materials coercive field (Ec) 100kV / cm or more is large ・ Imprint characteristic deterioration (Hysteresis curve shift occurs)
For this reason, it has been difficult to achieve high integration, low voltage drive, and high reliability of ferroelectric memory devices using this.

  The present invention has been made in view of such problems, and provides an oxide material capable of producing a ferroelectric material having a large remanent polarization (Pr) and a small coercive electric field (Ec). An object of the present invention is to provide an electronic device using such a ferroelectric material, which is highly reliable, can be highly integrated, and can be driven at a low voltage.

  As a result of diligent research in view of the above problems, the present inventor has found that a ferroelectric metal ion and a group IV element are added at a predetermined concentration to an oxide material having a perovskite structure used for a ferroelectric thin film. To experimentally confirm that the electrical properties (ferroelectric properties) of the thin body film are improved, and to invent the oxide material, ferroelectric material and electronic device using the same according to the present invention described below. Arrived.

The present invention includes a first electrode layer, possess a second electrode layer, a structure consisting of a ferroelectric thin film which is disposed between the first and second electrode layers, wherein the ferroelectric thin film Is an oxide material having a perovskite structure, in which an element constituting the perovskite structure is partially substituted with a polyvalent metal ion, and includes an oxide material to which a group IV element is added An electronic device , wherein the oxide material includes both the polyvalent metal ion concentration and the group IV element in a concentration range of 0.05 atomic% to 0.25 atomic%. Is.

The present invention also includes a first electrode layer, an insulating layer, have a deployed strength consisting of a dielectric thin film structure between the first electrode layer and the insulating layer, the ferroelectric thin film , An oxide material having a perovskite structure, in which an element comprising the perovskite structure is partially substituted by a polyvalent metal ion, and an oxide material containing a group IV element is added The device provides an electronic device characterized in that the oxide material contains both the polyvalent metal ion concentration and the group IV element in a concentration range of 0.05 atomic% to 0.25 atomic%. It is.

In the electronic device of the present invention, the oxide material having a perovskite structure is an oxide material having a bismuth layered perovskite structure of (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1} ) ^2−. It is characterized by being.

Wherein A represents a monovalent, divalent or trivalent ion, B represents a tetravalent, pentavalent or hexavalent ion, and m represents the number of BO ₆ octahedrons in the perovskite layer. Or the electronic device of 2.

  In the electronic device of the present invention, the oxide material is such that the polyvalent metal ion and the group IV element are added in an atomic ratio of 5: 1 to 1: 2, preferably about 1: 1. Characterize.

  In the electronic device of the present invention, the oxide material is characterized in that the Group IV element is added in an amount of 0.1 to 1.0 atomic%.

In the electronic device of the present invention, the oxide material having the perovskite structure includes bismuth lanthanum titanate (BLT; Bi _4-X La _X Ti ₃ O ₁₂ ), bismaster titanate (BIT; Bi ₄ Ti ₃ O ₁₂ ), and It is selected from the group consisting of strontium bismastantalate (SBT; SrBi ₂ Ta ₂ O ₉ ).

  In the electronic device of the present invention, the polyvalent metal ion is composed of Mo, W, T, Nb, Sb, Ta, Si, S, Ti, Ge, Se, Zr, Sn, Te, Ce, and Hf ions. It is selected from the group.

  In the electronic device of the present invention, the polyvalent metal ion is a six-coordinate Mo or W ion.

  In the electronic device of the present invention, the Group IV element is selected from the group consisting of Si, Ge, and Sn.

  In the electronic device of the present invention, the ferroelectric thin film contains the polyvalent metal ion at a concentration of 0.05 to 0.25 atomic%.

  The present invention is also an oxide material constituting a ferroelectric material, having a perovskite structure, wherein the elements constituting the perovskite structure are partially substituted with polyvalent metal ions, An oxide material to which an element is added is provided.

Oxide material of the present invention is characterized by having ^{_{(Bi 2 O 2) 2+ (}} A m-1 B m O 3m + 1) 2- bismuth layered perovskite structure.

In the above composition formula, A represents a monovalent, divalent or trivalent ion, B represents a tetravalent, pentavalent or hexavalent ion, and m represents the number of BO ₆ octahedrons in the perovskite layer.

  The oxide material of the present invention is characterized in that the polyvalent metal ion and the group IV element are added in an atomic ratio of 5: 1 to 1: 2, preferably about 1: 1.

  The oxide material having a perovskite structure of the present invention is an oxide selected from the group consisting of bismuth lanthanum titanate (BLT; Bi4-XLaXTi3O12), bismaster titanate (BIT; Bi4Ti3O12), and strontium bismastantalate (SBT; SrBi2Ta2O9). It is a material.

  In the oxide material of the present invention, the polyvalent metal ions are from Mo, W, T, Nb, Sb, Ta, Si, S, Ti, Ge, Se, Zr, Sn, Te, Ce, and Hf ions. It is selected from the group consisting of:

  In the oxide material of the present invention, the polyvalent metal ion is a hexacoordinate Mo or W ion.

  In the oxide material of the present invention, the Group IV element is selected from the group consisting of Si, Ge, and Sn.

  The present invention is also a ferroelectric material made from the oxide material described above, containing the polyvalent metal ion at a concentration of 0.05 to 0.25 atomic% and the group IV element at a concentration of 0.1 to 1.0 atomic%. The present invention provides a ferroelectric material characterized by

  As described above, according to the present invention, an oxide material capable of producing a ferroelectric material having a large remanent polarization (Pr) and a small coercive electric field (Ec) is provided. In particular, a suitable oxide material is provided by including BLT, which is a bismuth (Bi) layered perovskite ferroelectric material, with a hexavalent metal ion and Si.

  In addition, by using such an oxide material as a ferroelectric material, an electronic device with high reliability, high integration, and low voltage driving can be manufactured.

  The best mode for carrying out an oxide material, a ferroelectric material, and an electronic device using the same according to the present invention will be described below in detail with reference to the accompanying drawings. FIGS. 1-7 is a figure which illustrates embodiment of this invention, In these figures, the part which attached | subjected the same code | symbol represents the same thing, and the fundamental structure shall be the same.

First Embodiment In this embodiment, a ferroelectric material having a Bi layered perovskite structure is used, and the structure is generally (Bi ₂ O ₂ ) ²⁺ (A _m-1 B _m O _{3m + 1).} ) It shall be indicated by ^2- . (Bi ₂ O ₂ ) ²⁺ constitutes a Bi layered part, (A _m-1 B _m O _{3m + 1} ) ^2- constitutes a perovskite layer part, A is a monovalent, divalent, trivalent ion, B Represents tetravalent, pentavalent and hexavalent ions, and m represents the number of octahedrons of BO _{6 in} the perovskite layer. Here, in particular, a ferroelectric material having a composition of Bi _4-X La _X Ti ₃ O ₁₂ with m = 3 is used.

In the present embodiment, a polyvalent metal ion element that partially substitutes titanium (Ti) forming a B site with respect to a ferroelectric material made of BLT (Bi _{4 -X} La _X Ti ₃ O ₁₂ ). Molybdenum (Mo) is used as an additive, and Group IV element silicon (Si) is used as an additive to be contained in BLT. Mo is a hexavalent ion.

  BLT, which is a ferroelectric material, can be thinned by a sol-gel method. Specifically, a sol-gel solution A containing a ferroelectric material and a sol-gel solution B containing an organometallic compound in which a polyvalent metal ion element and a group IV element are dispersed in an organic solvent have a desired concentration and mixing. The mixed sol-gel solution C adjusted by the ratio is thinned. At this time, independent control of the polyvalent metal ion element and the group IV element is difficult, and the composition ratio of the polyvalent metal ion element and the group IV element depends on the composition of the sol-gel solution B.

  Hereinafter, a manufacturing process of an electronic device using a ferroelectric material made of BLT will be described with reference to FIGS. The electronic device of this embodiment has a typical MFM capacitor structure including a platinum (Pt) upper electrode, a BLT thin film containing Mo and Si, and a platinum (Pt) lower electrode.

  FIG. 1A is a process cross-sectional view after the insulating layer 2 is formed on the support substrate 1 and the lower electrode layer 3 is further formed on the insulating layer 2. The support substrate 1 is most typically made from a silicon wafer. If a silicon wafer is used for the support substrate 1, the insulating layer 2 can be easily formed by forming a thermal oxide film of silicon on the surface. This silicon thermal oxide film forming step is advantageous in that it can be performed using a conventional silicon semiconductor production line. The lower electrode layer 3 is formed by sputtering using Pt.

  FIG. 1B is a process cross-sectional view after the oxide material thin film layer 4 and the upper electrode layer 5 are sequentially deposited on the lower electrode layer 3. The oxide material thin film layer 4 is a MoSi-BLT thin film formed by adding the multivalent metal ion element Mo and the group IV element Si to the BLT described above and thinning the film by a sol-gel method. The upper electrode layer 5 is formed by sputtering using Pt.

  A specific method for producing a MoSi-BLT thin film by the sol-gel method is as follows. A sol-gel solution A containing BLT (atomic ratio Bi: La: Ti = 3.35: 0.75: 3) and a sol-gel solution B containing Mo and Si (atomic ratio 1: 1) have a substitution amount of Mo of 0.1 to 0.1 with respect to Ti. The mixed sol-gel solution C is obtained by mixing so as to be about 2% (atomic ratio). The mixed sol-gel solution C is spin-coated (2500 rpm, 20 seconds), dried (240 ° C., 10 minutes, in air), calcined (400 ° C., 10 minutes, in an oxygen atmosphere), and fired (700 ° C. For 30 minutes in an oxygen atmosphere), a MoSi-BLT thin film is formed.

  In FIG. 2A, following the step shown in FIG. 1B, the upper electrode layer 5 is patterned to form the upper electrode 7, and the oxide material thin film layer 4 is further patterned to form the oxide material thin film 6. It is process sectional drawing after forming. In the present embodiment, the lower electrode layer 3 may be further patterned. Patterning of the upper electrode layer 5 and the oxide material thin film layer 4 can be performed using conventional photolithography and dry etching, or wet etching. These microfabrication techniques may be selected according to design rules designed by those skilled in the art.

  FIG. 2B shows an interlayer insulating layer 8 formed on the MFM (in this embodiment, Pt / MoSi-BLT / Pt capacitor) structure formed as described above, and a desired electrode (in this embodiment). These are process sectional drawing after forming the contact hole 9 in the upper electrode 7 and the lower electrode layer 3). The interlayer insulating layer 8 is preferably formed using silicon oxide by spin coating, CVD vapor deposition, sputtering, or the like. In the present embodiment, SOG (Spin On Glass) is used in consideration of device damage. Following the formation of the interlayer insulating layer 8, contact holes 9 are formed in the upper electrode 7 and the lower electrode layer 3, respectively, by photolithography and etching.

  FIG. 2C is a process cross-sectional view after the wiring 10 is provided in the contact hole 9 formed as described above. The wiring 10 is formed by depositing aluminum (Al), which is a wiring material, on the two contact holes 9 and the surrounding interlayer insulating layer 8 and patterning the aluminum into a desired shape. At this time, in order to prevent mutual diffusion, it is preferable to provide titanium nitride (TiN) in the lower layer of Al.

  Through the above steps, the structure of the electronic device using the BLT thin film containing Mo and Si is completed. Next, the evaluation results of the electrical characteristics (ferroelectric characteristics) of the electronic device having the MFM structure of the present embodiment formed as described above will be shown.

  FIG. 3 shows the electronic device of the present embodiment fabricated as described above, with the Mo concentration in the MoSi-BLT thin film as the horizontal axis and the remanent polarization (Pr) and coercive electric field (Ec) as the vertical axis. It is the graph which showed these correlations. According to this graph, the remanent polarization (Pr) increases with increasing Mo concentration on the low Mo concentration side, and takes a local maximum when the Mo concentration reaches 0.05 atomic% to 0.25 atomic%. It decreases monotonously with increasing Mo concentration. On the other hand, the coercive electric field (Ec) increases with increasing Mo concentration on the low Mo concentration side, takes a maximum value near 0.05 atomic percent of Mo concentration, and then decreases monotonously with increasing Mo concentration. ing. As described above, the Si concentration (atomic%) in the MoSi-BLT thin film is equal to the Mo concentration, but the correlation between the Si concentration, remanent polarization (Pr), and coercive electric field (Ec) is also shown in FIG. Results similar to those shown in (1) were obtained (not shown).

  Therefore, when the Mo concentration (or Si concentration) of the MoSi-BLT thin film is in the range of 0.05 atomic% to 0.25 atomic%, the remanent polarization (Pr) is almost maximum and the coercive electric field (Ec) is reduced. Therefore, the addition effect of Mo and Si is preferable in these ranges. The most preferable Mo concentration (or Si concentration) was 0.1 atomic%.

  Here, the remanent polarization (Pr) and coercive electric field (Ec) in the preferable Mo concentration (or Si concentration) range, and the remanent polarization (Pr) and coercive electric field (Ec) when the Mo concentration (or Si concentration) is 0. ), The electronic device according to the present embodiment containing Mo, which is a polyvalent metal ion element, and Si, which is a group IV element, in BLT, which is an oxide material, is an electronic device made of BLT that does not contain these. It was experimentally clarified that the electrical characteristics were remarkably improved compared to. By using an oxide material that increases the remanent polarization (Pr) and decreases the coercive electric field (Ec), the electronic device can be highly integrated and driven at a low voltage.

  FIG. 4 is a diagram showing the ferroelectric characteristics of a MoSi-BLT thin film containing 0.1 atomic% of Mo and Si and a BLT thin film containing no Mo and Si by hysteresis curves. According to this figure, the hysteresis curve of the MoSi-BLT thin film shows a marked improvement in the shape of the hysteresis curve (an increase in remanent polarization and a decrease in coercive field) compared to the normal BLT thin film. It can be confirmed that the ferroelectric characteristics are greatly improved.

  From the above, the BLT thin film contains high-concentration (increase in remanent polarization) and low-voltage drive (resistance of coercive electric field) by containing Mo, which is a polyvalent metal ion element, and Si, which is a Group IV element, at a constant concentration. (Decrease) is possible.

  Next, after leaving the MoSi-BLT thin film (containing Mo and Si 0.1 atomic%) used in the electronic device of this embodiment and the BLT thin film containing no Mo and Si at 115 ° C. for 1 day, The result of evaluating each electrical characteristic (ferroelectric characteristic) is shown.

  FIG. 5 is a diagram showing the ferroelectric characteristics before and after heating of the MoSi-BLT thin film containing 0.1 atomic% of Mo and Si described above by hysteresis curves. FIG. 6 is a diagram showing the ferroelectric characteristics before and after heating of the above-described BLT thin film containing no Mo and Si by hysteresis curves.

  As is clear from FIG. 5 and FIG. 6, for the BLT thin film containing no Mo and Si, imprints (shifts in the hysteresis curve) are observed in the hysteresis curve before and after heating. For the MoSi-BLT thin film containing 0.1 atomic% of Mo and Si, imprint is hardly generated in the hysteresis curve before and after heating.

  By the way, an experimental result is known in recent years that even if a BLT thin film containing no Mo and Si is produced at a crystallization temperature of about 750 ° C., imprinting of a hysteresis curve does not occur. Further, the crystallization temperature of the MoSi-BLT thin film according to the present embodiment and the BLT thin film containing no Mo and Si are 700 ° C. Then, in order to suppress the imprint of the hysteresis curve in the conventional BLT thin film, it was necessary to prepare a crystallization temperature of about 750 ° C. According to this embodiment, Mo and Si are added to the BLT thin film. Thus, it becomes possible to prepare at a crystallization temperature of 700 ° C. In other words, the temperature in the manufacturing process of the BLT thin film was reduced by 50 ° C. Also in this respect, it can be seen that the MoSi-BLT thin film of this embodiment is an excellent ferroelectric material.

  From the above, the BLT thin film contains high-concentration (increase in remanent polarization) and low-voltage drive (resistance of coercive electric field) by containing Mo, which is a polyvalent metal ion element, and Si, which is a Group IV element, at a constant concentration. (Decrease) is possible.

In the present embodiment, an electronic device having an MFM structure using a Pt / MoSi-BLT / Pt capacitor has been described as an example. However, an electronic device having an MFIS structure can be formed in the same manner. In this case, for example, La-Al ₂ O ₃ which is alumina (Al ₂ O ₃ ) doped with lanthanum (La) may be used as an insulator having an MFIS structure. This electronic device manufacturing method is based on the same manufacturing process as in this embodiment except that the insulating layer 2 in the electronic device of this embodiment is omitted and the lower electrode layer 3 is formed of La—Al ₂ O ₃ . Similarly, an electronic device having an MFMIS structure can be formed. In this case, it can be formed by providing, for example, Pt / MoSi-BLT / Pt (MFM structure) used in this embodiment on the insulator. Also in the electronic device having these MFIS structure or MFMIS structure, excellent electrical characteristics (ferroelectric characteristics) are provided as in the present embodiment.

In the present embodiment, the MoSi-BLT ferroelectric material has been described as an example. Similarly, other ferroelectric materials having a Bi layered perovskite structure such as SBT (SrBi ₂ Ta ₂ O ₉ ) and BIT (Bi ₄ Ti ₃ O ₁₂ ) or PZT (PbZr _X Ti _1-X O ₃ ) having a perovskite structure can also be used.

  Further, as described in the present embodiment, platinum (Pt) is typically used for the lower electrode layer 3 and the upper electrode layer 5, but the present invention is not limited to this, and iridium (Ir), The electrode layer may be formed using ruthenium (Ru) or the like.

  Furthermore, as the polyvalent metal ions, hexavalent ions such as Mo, tungsten (W), tellurium (Te) are suitable, but pentavalent ions (Nb, Sb, Ta) or tetravalent ions (Si, S, Ti, Ge, Se, Zr, Sn, Te, Ce, Hf) may be used. As the group IV element, silicon (Si) is preferable, but germanium (Ge), tin (Sn), or the like may be used. An embodiment in which W is used for the polyvalent metal ion is shown below.

Second Embodiment In this embodiment, as in the first embodiment, BLT (atomic ratio Bi: La: Ti = 3.35: 0.75: 3) having a Bi layered perovskite structure is used as a ferroelectric material. An electronic device using a WSi-BLT thin film containing a polyvalent metal ion element W and a group IV element Si as an oxide material thin film layer will be described.

  The manufacturing method of the electronic device of this embodiment is substantially the same as the manufacturing method of the electronic device of the first embodiment shown in FIGS. The WSi-BLT thin film is prepared by the same sol-gel method as described above. That is, BLT (atomic ratio Bi: La: Ti = 3.35: 0.75: 3) sol-gel solution A which is a source of oxide material and WSi (atomic ratio 1: 1) sol-gel solution B which is a source of W and Si Are mixed so that the substitution amount of W with respect to Ti is about 0.1 to 2 atomic% to obtain a mixed sol-gel solution C. The mixed sol-gel solution C is spin-coated (2500 rpm, 20 seconds), dried (240 ° C., 10 minutes, in air), calcined (400 ° C., 10 minutes, in an oxygen atmosphere), and fired (700 ° C. For 30 minutes in an oxygen atmosphere), a WSi-BLT thin film is formed.

  FIG. 7 is a graph showing the correlation between the W concentration in the WSi-BLT thin film and the residual polarization (Pr) and coercive electric field (Ec) on the vertical axis. It is the graph which showed the relationship. According to this graph, the remanent polarization (Pr) increases as the W concentration increases on the low W concentration side, takes a local maximum when the W concentration becomes 0.05 atomic% to 0.25 atomic%, and thereafter, It decreases monotonically with increasing W concentration. On the other hand, the coercive electric field (Ec) increases with increasing W concentration on the low W concentration side, takes a maximum value around 0.05 atomic% W concentration, and then decreases monotonically with increasing W concentration. ing. As described above, the Si concentration (atomic%) in the WSi-BLT thin film is equal to the W concentration, but the correlation between the Si concentration, remanent polarization (Pr), and coercive electric field (Ec) is also shown in FIG. Results similar to those shown in (1) were obtained (not shown).

  Therefore, when the W concentration (or Si concentration) of the WSi-BLT thin film is in the range of 0.05 atomic% to 0.25 atomic%, the remanent polarization (Pr) has almost the maximum value and the coercive electric field (Ec) decreases. Therefore, the addition effect of W and Si is preferable in these ranges. The most preferable W concentration (or Si concentration) was 0.05 atomic%.

  Here, the remanent polarization (Pr) and coercive electric field (Ec) in the preferable W concentration (or Si concentration) range, and the remanent polarization (Pr) and coercive electric field (Ec) when the W concentration (or Si concentration) is 0. ), The electronic device of the present embodiment in which W, which is a polyvalent metal ion element, and Si, which is a group IV element, is contained in BLT, which is an oxide material, is an electronic device made of BLT that does not contain these. It was experimentally clarified that the electrical characteristics were remarkably improved compared to. By using an oxide material that increases the remanent polarization (Pr) and decreases the coercive electric field (Ec), the electronic device can be highly integrated and driven at a low voltage.

In this embodiment, the electronic device having the MFM structure using the Pt / WSi-BLT / Pt capacitor has been described as an example. However, an electronic device having the MFIS structure can be formed in the same manner. In this case, for example, La-Al ₂ O ₃ which is alumina (Al ₂ O ₃ ) doped with lanthanum (La) may be used as an insulator having an MFIS structure. This electronic device manufacturing method is based on the same manufacturing process as in this embodiment except that the insulating layer in the electronic device of this embodiment is omitted and the lower electrode layer is formed of La—Al ₂ O ₃ . Similarly, an electronic device having an MFMIS structure can be formed. In this case, it can be formed by providing, for example, Pt / WSi-BLT / Pt (MFM structure) used in this embodiment on the insulator. Also in the electronic device having these MFIS structure or MFMIS structure, excellent electrical characteristics (ferroelectric characteristics) are provided as in the present embodiment.

In the present embodiment, the WSi-BLT ferroelectric material has been described as an example. Similarly, other ferroelectric materials having a Bi layered perovskite structure, such as SBT (SrBi ₂ Ta ₂ O ₉ ) and BIT, have been described. (Bi ₄ Ti ₃ O ₁₂ ) or PZT (PbZr _X Ti _1-X O ₃ ) having a perovskite structure can also be used.

  In addition, platinum (Pt) is typically used for the lower electrode layer and the upper electrode layer. However, the present invention is not limited to this, and the electrode layer is formed using iridium (Ir), ruthenium (Ru), or the like. It may be formed.

Third Embodiment In this embodiment, as in the first and second embodiments, BLT (atomic ratio Bi: La: Ti = 3.35: 0.75: 3) having a Bi layered perovskite structure as a ferroelectric material is used. An electronic device using a ferroelectric thin film containing a polyvalent metal ion Mo and a group IV element Si as an oxide thin film layer will be described. The difference between the first and second embodiments is that, instead of using a sol-gel solution containing both a polyvalent metal ion such as MoSi or WSi and a group IV element, a polyvalent metal ion, The purpose is to use two types of sol-gel solutions each containing a Group IV element individually.

  The manufacturing method of the electronic device of this embodiment is the same as the manufacturing method described in the first and second embodiments. However, the preparation of the mixed sol-gel solution is different. That is, BLT (atomic ratio Bi: La: Ti = 3.35: 0.75: 3) sol-gel solution A which is a source of oxide material and BiMo (atomic ratio Bi: Mo = 2.2: 1.0) sol-gel which is a source of Mo Solution B and Si alkoxide sol-gel solution C, which is a Si supply source, are such that the amount of substitution of Mo with respect to Ti is about 0.1 to 2 atomic% and the amount of addition of Si with respect to BLT is about 0.1 to 1.0 atomic%. To obtain a mixed sol-gel solution D, which is spin-coated, dried, calcined, and baked (according to the description of the first and second embodiments) to form a Mo-Si-BLT thin film. Is done.

  FIG. 8 shows the correlation between the Si device in the Mo-Si-BLT thin film and the remanent polarization (2Pr) on the vertical axis for the electronic device of this embodiment manufactured as described above. It is a graph. According to this graph, it is understood that the remanent polarization value (2Pr) increases when the Si concentration is 0.1 to 1.0 atomic%, and in particular, takes a maximum value when the Si concentration is around 0.25 atomic%. However, such a tendency is prominent in the ferroelectric thin film (Mo plot is constant at 0.5 atomic%) substituted with Mo (a circle in the figure), and the ferroelectric thin film without Mo substituted (The plot of Δ in the figure) was less effective. Accordingly, it has been found that the addition of a group IV element in the presence of a polyvalent metal ion is effective for obtaining a suitable electronic device and oxide material.

  As the ferroelectric material having such excellent characteristics, a sol-gel solution of BiW (atomic ratio Bi: W = 2.2: 1.0) which is a supply source of polyvalent metal ions W can also be used.

  As mentioned above, although the oxide material of this invention, the ferroelectric material, and the electronic device using the same were shown and demonstrated concrete embodiment, this invention is not limited to these. A person skilled in the art can make various changes and improvements to the configurations and functions of the invention according to the above-described embodiments or other embodiments without departing from the gist of the present invention.

  The oxide material and ferroelectric material of the present invention can be used as a material for the electronic device exemplified in each of the above embodiments, as well as a ferroelectric nonvolatile memory and a ferroelectric capacitor using the polarizability thereof, It can also be used for piezoelectric filters and ultrasonic transducers using piezoelectricity, infrared sensors using pyroelectricity, light modulation elements and optical shutters using the electro-optic effect, and the like.

It is a figure which shows the manufacturing process of the MFM type electronic device concerning 1st Embodiment of this invention. (A) is process sectional drawing after forming an insulating layer on a support substrate, and also forming a lower electrode layer on an insulating layer, (b) is an oxide material thin film layer on a lower electrode layer. FIG. 6 is a process cross-sectional view after sequentially depositing upper electrode layers. It is a figure which shows the manufacturing process of the MFM type electronic device concerning 1st Embodiment of this invention. (A) is a process after patterning the upper electrode layer to form the upper electrode, and further patterning the oxide material thin film layer to form the oxide material thin film, following the process shown in FIG. It is sectional drawing, (b) is process sectional drawing after forming an interlayer insulation layer on the MFM structure of (a), and forming a contact hole in an upper electrode and a lower electrode, (c) It is process sectional drawing after providing wiring in a contact hole. It is a graph which shows the relationship between Mo density | concentration in a MoSi-BLT thin film, a residual polarization (Pr), and a coercive electric field (Ec) about the electronic device of 1st Embodiment of this invention. It is a figure which shows the ferroelectric characteristic of the MoSi-BLT thin film containing Mo and Si 0.1 atomic%, and the BLT thin film which does not contain Mo and Si at all by a hysteresis curve, respectively. It is the figure which showed the ferroelectric characteristic before the heating of the MoSi-BLT thin film containing Mo and Si 0.1 atomic% before and after a heating, respectively. It is the figure which showed the ferroelectric characteristic before the heating of the BLT thin film which does not contain Mo and Si at all, and after the heating with the hysteresis curve, respectively. It is a graph which shows the relationship between Mo density | concentration in a WSi-BLT thin film, a residual polarization (Pr), and a coercive electric field (Ec) about the electronic device of 2nd Embodiment of this invention. It is a graph which shows the relationship between the residual polarization | polarization value and the Si density | concentration in the Mo-Si-BLT thin film (Mo = 0.5 atomic%) and Si-BLT about the electronic device of 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support substrate 2 Insulating layer 3 Lower electrode layer 4 Oxide material thin film layer 5 Upper electrode layer 6 Oxide material thin film 7 Upper electrode 8 Interlayer insulating layer 9 Contact hole 10 Wiring

Claims (5)

The ferroelectric thin film has a structure comprising a first electrode layer, a second electrode layer, and a ferroelectric thin film disposed between the first and second electrode layers, and the ferroelectric thin film has a perovskite structure. An electronic device comprising an oxide material having a group IV element added, wherein an element constituting the perovskite structure is partially substituted by a polyvalent metal ion. And
The oxide material is bismuth lanthanum titanate (BLT; Bi _4-X La _X Ti ₃ O ₁₂ ) ”
And the polyvalent metal ion is each ion of Mo or W, and the group IV element is Si,
The electronic device, wherein the oxide material contains both the polyvalent metal ion concentration and the Group IV element in a concentration range of 0.05 atomic% to 0.25 atomic% . The ferroelectric thin film has a structure comprising a first electrode layer, an insulating layer, and a ferroelectric thin film disposed between the first electrode layer and the insulating layer, and the ferroelectric thin film has an oxide having a perovskite structure. An electronic device comprising an oxide material to which a group IV element is added, wherein the element constituting the perovskite structure is partially substituted with a polyvalent metal ion,
The oxide material is bismuth lanthanum titanate (BLT; Bi _4-X La _X Ti ₃ O ₁₂ ) ”
And the polyvalent metal ion is each ion of Mo or W, and the group IV element is Si,
The electronic device, wherein the oxide material contains both the polyvalent metal ion concentration and the Group IV element in a concentration range of 0.05 atomic% to 0.25 atomic% . The electronic device according to claim 1, wherein the polyvalent metal ion is a hexacoordinate Mo or W ion. An oxide material comprising a ferroelectric material, having a perovskite structure, wherein the elements constituting the perovskite structure are partially substituted with polyvalent metal ions, and a group IV element is added. ,
The oxide material is bismuth lanthanum titanate (BLT; Bi _4-X La _X Ti ₃ O ₁₂ ) ”
And the polyvalent metal ion is each ion of Mo or W, and the group IV element is Si,
The oxide material is characterized in that the polyvalent metal ion concentration and the group IV element are both contained in a concentration range of 0.05 atomic% to 0.25 atomic% . The oxide material according to claim 4,
The oxide material, wherein the polyvalent metal ions are hexacoordinate Mo or W ions.

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