WO2008082046A1 - Ferroelectric memory device, fet, and methods of manufacturing the same - Google Patents

Ferroelectric memory device, fet, and methods of manufacturing the same Download PDF

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Publication number
WO2008082046A1
WO2008082046A1 PCT/KR2007/002884 KR2007002884W WO2008082046A1 WO 2008082046 A1 WO2008082046 A1 WO 2008082046A1 KR 2007002884 W KR2007002884 W KR 2007002884W WO 2008082046 A1 WO2008082046 A1 WO 2008082046A1
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Prior art keywords
ferroelectric
layer
memory device
gate electrode
channel forming
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PCT/KR2007/002884
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French (fr)
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Byung-Eun Park
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University Of Seoul Foundation Of Industry-Academic Cooperation
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Priority claimed from KR1020070058170A external-priority patent/KR100877429B1/en
Publication of WO2008082046A1 publication Critical patent/WO2008082046A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/22—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using ferroelectric elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/401—Multistep manufacturing processes
    • H01L29/4011—Multistep manufacturing processes for data storage electrodes
    • H01L29/40111—Multistep manufacturing processes for data storage electrodes the electrodes comprising a layer which is used for its ferroelectric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
    • H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/49—Metal-insulator-semiconductor electrodes, e.g. gates of MOSFET
    • H01L29/51—Insulating materials associated therewith
    • H01L29/516—Insulating materials associated therewith with at least one ferroelectric layer
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B51/00—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory transistors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B51/00—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory transistors
    • H10B51/30—Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory transistors characterised by the memory core region
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/22—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using ferroelectric elements
    • G11C11/223—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using ferroelectric elements using MOS with ferroelectric gate insulating film

Definitions

  • the present invention relates to a ferroelectric memory device, a field-effect transistor (FET) , and methods of manufacturing the same.
  • ROMs read only memories
  • EPROM electrically erasable PROM
  • EEPROM electrically erasable PROM
  • flash ROM random access memories
  • RAMs random access memories
  • the memory devices are composed of a capacitor and a transistor formed on a semiconductor wafer such as a silicon wafer.
  • the conventional memory devices have been studied to increase the density of memory cells.
  • a nonvolatile memory device capable of maintaining stored data even if a power supply is cut off has attracted much attention, extensive research aimed at using a ferroelectric material as a material for a memory device has continued to progress .
  • inorganic materials such as lead zirconate titanate (PZT), Strontium bismuth tantalate (SBT), lanthanum-substituted bismuth titanate (BLT) , and the like are mainly used.
  • PZT lead zirconate titanate
  • SBT Strontium bismuth tantalate
  • BLT lanthanum-substituted bismuth titanate
  • the inorganic ferroelectric materials have some drawbacks in that they are expensive, polariby characteristics are degraded with the passage of time, bhey require a high temperature treatment during the thin film formation, and they require expensive equipment.
  • the memory devices using the organic materials have drawbacks in that it is difficult to achieve a high density in the same memory structure compared with the conventional memory devices using inorganic materials.
  • the present invention has been made in an effort to solve the above-described problems.
  • the present invention provides a ferroelectric memory device capable of being easily manufactured at low cost, having excellent polarization characteristics, and providing a greater number of memory cells in the same area, a field-effect transistor (FET), and methods of manufacturing the same.
  • FET field-effect transistor
  • a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
  • a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
  • the channel forming layer may be an organic or inorganic semiconductor layer.
  • the channel forming layer may be an insulating layer.
  • the substrate may be formed of at least one selected from the group consisting of polyimide (PI), polycarbonate (PC) , polyethersulfone (PES) , polyetheretherketone (PEEK) , polybutyleneterephthalate (PBT) , polyethyleneterephthalate (PET) , polyvinylchloride (PVC) , poLyethylene (PE) , ethylene copolymer, polypropylene (PP), propylene copolymer, poly (4- methyl-1-pentene) (TPX) , polyarylate (PAR), polyacetal (POM), polyphenyleneoxide (PPO) , polysulfone (PSF) , polyphenylenesulfide (PPS) , polyvinylidenechloride (PVDC) , polyvinylacetate (PVAC), polyvinylalcohol (PVA), polyvinylacetal (PVAL), polys
  • the substrate may be formed of a material including paper.
  • the inorganic ferroelectric material may comprise at least one selected from the group consisting of a ferroelectric oxide, a ferroelectric fluoride, a ferroelectric semiconductor, and a mixture thereof.
  • the mixture may further comprise a suicide, a silicate or any other metal.
  • the organic material may be a polymer ferroelectric material.
  • the polymer ferroelectric material may comprise at least one selected from the group consisting of polyvinylidene fluoride (PVDF), PVDF polymer, PVDF copolymer, PVDF terpolymer and, further, odd-numbered nylon, cyano- polymer, and polymer or copolymer thereof.
  • PVDF polyvinylidene fluoride
  • the polymer ferroelectric material may be PVDF-TrFE.
  • the ferroelectric layer may be formed by heating and baking a mixed solution of an inorganic ferroelectric solution and an organic solution.
  • a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
  • a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer .
  • An insulating layer may be formed between the memory cells, the insulating layer being formed of an organic material .
  • the ferroelectric layers of the stacked memory cells may be arranged adjacent to each other.
  • the gate electrodes of the stacked memory cells may be arranged adjacent to each other.
  • a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
  • a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
  • a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a method of manufacturing a ferroelectric memory device including a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, the method comprising: forming the gate electrode; forming the channel forming layer; forming the ferroelectric layer using a mixture of an inorganic ferroelectric material and an organic material; and forming the drain and source electrodes .
  • a method of manufacturing a ferroelectric memory device including a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, the method comprising: forming the gate electrode; forming the channel forming layer; forming the ferroelectric layer using a mixture of a solid solution of an inorganic ferroelectric material and an organic material; and forming the drain and source electrodes .
  • a method of manufacturing a ferroelectric memory device comprising: forming a first memory cell on a substrate; forming an insulating layer on the first memory cell; and forming a second memory cell on the insulating layer, wherein forming the first and second memory cells comprise forming a gate electrode, forming a channel forming layer, forming a ferroelectric layer using a mixture of an inorganic ferroelectric material and an organic material, and forming drain and source electrodes, respectively.
  • a method of manufacturing a ferroelectric memory device comprising: forming a first memory cell on a substrate; forming an insulating layer on the first memory cell; and forming a second memory cell on the insulating layer, wherein forming the first and second memory cells comprise forming a gate electrode, forming a channel forming layer, forming a ferroelectric layer using a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and forming drain and source electrodes, respectively.
  • a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein each of the ferroelectric layers of the stacked memory cells is formed of a mixture of an inorganic ferroelectric material and an organic material, the mixtures being different from each other, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
  • a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein each of the ferroelectric layers of the stacked memory cells is formed of a mixture of an inorganic ferroelectric material and an organic material, the mixtures being different from each other, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
  • the channel forming layer may be formed between the gate electrode and the ferroelectric layer.
  • the ferroelectric layer may be formed between the gate electrode and the channel forming layer.
  • the organic material may have ferroelectric characteristics .
  • a mixed solution of an inorganic ferroelectric solution and an organic solution may be coated on the substrate to form a ferroelectric film, and the ferroelectric film may be heated, baked and etched to form the ferroelectric layer.
  • the mixed solution may comprise a PZT solution and a PVDF-TrFE solution.
  • the PZT solution may be prepared by mixing a PZO solution and a PTO solution.
  • the PVDF-TrFE solution may be prepared by dissolving PVDF-TrFE powder in at least one solvent selected from the group consisting of C 4 H 5 O (THF), C 4 H 8 O (MEK), C 3 H 6 O (acetone), C 3 H 7 NO (DMF), and C 2 H 6 OS (DMSO).
  • solvent selected from the group consisting of C 4 H 5 O (THF), C 4 H 8 O (MEK), C 3 H 6 O (acetone), C 3 H 7 NO (DMF), and C 2 H 6 OS (DMSO).
  • the ferroelectric layer may be formed by a spin coating, ink-jet printing, or screen printing method.
  • the process of etching the ferroelectric layer may be performed by a buffered oxide etching (BOE) method.
  • BOE buffered oxide etching
  • the process of etching the ferroelectric layer may be performed by a two-step etching method using BOE and gold etchant .
  • the process of etching the ferroelectric layer may be performed by a reactive ion etching (RIE) method.
  • RIE reactive ion etching
  • the baking temperature may be below 200 ° C.
  • FIGS. 1 to 5 are graphs showing capacitance-voltage characteristics of ferroelectric materials applied to the present invention.
  • FIG. 6 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a first embodiment of the present invention
  • FIG. 7 is an equivalent circuit diagram of the memory device shown in FIG. 6;
  • FIG. 8 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a second embodiment of the present invention
  • FIGS. 9A to 9P are cross-sectional views showing manufacturing processes of the ferroelectric memory device shown in FIG. 8;
  • FIG. 10 is a cross-sectional view showing a modified structure of the ferroelectric memory device shown in FIG. 8 ;
  • FIGS. HA to HD are cross-sectional views showing other examples of the ferroelectric memory device in accordance with the present invention.
  • the inorganic ferroelectric materials include ferroelectric oxides, ferroelectric fluorides such as BaMgF 4 (BMF) , and ferroelectric semiconductors.
  • the organic ferroelectric materials include polymer ferroelectric materials and the like.
  • the ferroelectric oxides include perovskite ferroelectric materials such as PbZr x Tii_ x O 3 (PZT) , BaTiO 3 and PBTiO 3 , pseudo-ilmenite ferroelectric materials such as LiNbO 3 and LiTaO 3 , tungsten-bronze (TB) ferroelectric materials such as PbNb 3 O 6 and Ba 2 NaNb 5 Oi 5 , ferroelectric materials having a bismuth layer structure such as SrBi 2 Ta 2 O 9 (SBT), (Bi, La) 4 Ti 3 Oi 2 (BLT) and Bi 4 Ti 3 Oi 2 , pyrochlore ferroelectric materials such as La 2 Ti 2 O 7 , and ferroelectric materials such as RMnO 3 , Pb 5 Ge 3 On (PGO) and BiFeO 3 (BFO) including a rare earth element (R) such as Y, Er, Ho, Tm, Yb and Lu .
  • R rare earth element
  • ferroelectric semiconductors include 2-6 compounds such as CdZnTe, CdZnS, CdZnSe, CdMnS, CdFeS, CdMnSe and CdFeSe.
  • polymer ferroelectric materials include polyvinylidene fluoride (PVDF), PVDF polymer, PVDF copolymer, PVDF terpolymer and, further, odd-numbered nylon, cyano-polymer, and polymer or copolymer thereof.
  • PVDF polyvinylidene fluoride
  • the inorganic ferroelectric materials including the ferroelectric oxides, the ferroelectric fluorides and the ferroelectric semiconductors have dielectric constants greater than those of the organic ferroelectric materials. Accordingly, the generally proposed ferroelectric field-effect transistor (FET) or ferroelectric memory device employs the inorganic ferroelectric materials for forming the ferroelectric layer.
  • FET ferroelectric field-effect transistor
  • the above-described inorganic ferroelectric materials require a high temperature treatment above 500 ° C, for example, to be formed on a substrate.
  • a transition layer of low quality is formed on the boundary between the ferroelectric layer and a silicon substrate due to the high temperature, and chemical elements such as Pb and Bi in the ferroelectric material are diffused into the silicon substrate, thus shortening the data retention time of the ferroelectric memory.
  • a mixture of an inorganic ferroelectric material and an organic material or an organic ferroelectric material is used as the ferroelectric material,
  • the inorganic ferroelectric materials are formed at higher temperatures, while their dielectric constants are high.
  • the organic materials including the organic ferroelectric materials are formed at lower temperatures, while their dielectric constants are relatively low. Accordingly, when mixing the inorganic ferroelectric material with the organic material or the organic ferroelectric material, it is possible to obtain a ferroelectric material having a dielectric constant above a predetermined value and formed at a much lower temperature.
  • the inorganic ferroelectric material and the organic material may be mixed with each other as follows:
  • the organic materials mixed with the inorganic ferroelectric material include, a monomer, an oligomer, a polymer, and a copolymer.
  • an organic material having a high dielectric constant may be used.
  • the organic materials having a high dielectric constant include polyvinylpyrrolidone (PVP) , polycarbonate (PC) , polyvinyl chloride (PVC) , polystyrene (PS) , epoxy, polymethylmethacrylate (PMMA), polyimide (PI), polyethylene (PE) , polyvinyl alcohol (PVA) , polyhexamethylene adipamide (nylon 66), polyetherketoneketone (PEKK), and the like.
  • PVP polyvinylpyrrolidone
  • PC polycarbonate
  • PVC polyvinyl chloride
  • PS polystyrene
  • epoxy epoxy
  • PMMA polymethylmethacrylate
  • PI polyimide
  • PE polyethylene
  • PVA polyvinyl alcohol
  • Nylon 66 polyhexamethylene adipamide
  • PEKK polyetherketoneketone
  • the organic materials include a nonpolar organic material, such as fluorinated para-xylene, fluoropolyarylether, fluorinated polyimide, polystyrene, poly ( ⁇ -methyl styrene) , poly ( ⁇ -vinylnaphthalene) , poly (vinyltoluene) , polyethylene, cis-polybutadiene, polypropylene, polyisoprene, poly (4-methyl-l-pentene) , poly (tetrafluoroethylene) , poly (chlorotrifluoroethylene) , poly (2-methyl-1, 3-butadiene) , poly (p-xylylene) , poly( ⁇ - ⁇ - ⁇ '- ⁇ '-tetrafluoro-p-xylylene) , poly [1, 1- (2-methyl propane) bis (4-phenyl) carbonate] , poly (cyclohexyl methacrylate) , poly (chlorostyrene)
  • organic semi-conducting materials that can be used in this invention include soluble compounds and soluble derivatives of compounds of the following list: conjugated hydrocarbon polymers such as polyacene, polyphenylene, poly (phenylene vinylene) , polyfluorene including oligomers of those conjugated hydrocarbon polymers; condensed aromatic hydrocarbons such as anthracene, tetracene, chrysene, pentacene, pyrene, perylene, coronene; oligomeric para substituted phenylenes such as p-quaterphenyl (p-4P) , p- quinquephenyl (p—5P) , p-sexiphenyl (p—6P) ; conjugated heterocyclic polymers such as poly (3-substituted thiophene) , poly (3, 4-bisubstituted thiophene) , polybenzothiophene, polyisothianapthene, poly (N
  • the ferroelectric materials employed in the present invention have the following characteristics:
  • the ferroelectric layer is formed using a mixed solution of an inorganic material and an organic material, it is possible to easily form the ferroelectric layer by an ink-jet printing, spin coating or screen printing method;
  • FIGS. 1 to 5 are graphs showing polarization characteristics of ferroelectric layers formed of an inorganic ferroelectric material and an organic ferroelectric material such as PbZr x Tii- x O 3 (PZT) and PVDF- TrFE mixed in predetermined ratios .
  • the ferroelectric layer was formed in such a manner that a PZT solution and a PVDF-TrFE solution were mixed in a predetermined ratio to form a mixed solution, the mixed solution was coated on a silicon wafer by a spin coating method, and the resulting silicon wafer was heated in the temperature range of 150 to 200 ° C on a hot plate for a predetermined period of time.
  • the PZT solution was prepared by mixing a PZO solution and a PTO solution, in which the PZO solution was formed by mixing a zirconium propoxide solution with a mixed solution of a 2-methoxyethanol solution and a lead acetate trihydrate solution and the PTO solution was formed by mixing a titanium isopropoxide solution with the mixed solution of the 2-methoxyethanol solution and the lead acetate trihydrate solution.
  • the PVDF-TrFE solution was prepared by dissolving PVDF-TrFE powder in a solvent such as C 4 H 5 O (THF) , C 4 H 8 O (MEK), C 3 H 6 O (acetone), C 3 H 7 NO (DMF), and C 2 H 6 OS (DMSO).
  • FIG. 1 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 1:1
  • FIG. 2 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 2:1
  • FIG. 3 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 3:1
  • FIGS. IA, 2A and 3A the thickness of the ferroelectric layer was 50 nm; in FIGS. IB, 2B, 3B, 4 and 5, the thickness of the ferroelectric layer was 75 nm; and in FIG. 1C, the thickness of the ferroelectric layer was 100 nm.
  • the characteristic curves represented as A show the polarization characteristics in which the formation temperature of the ferroelectric layer was 190 ° C
  • the characteristic curves represented as B show the polarization characteristics in which the formation temperature of the ferroelectric layer was 170 ° C
  • the characteristic curves represented as C show the polarization characteristics in which the formation temperature of the ferroelectric layer was 150 ° C.
  • the ferroelectric material in accordance with the present invention can be effective used as the material of the ferroelectric field-effect transistor or ferroelectric memory.
  • FIG. 6 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a first embodiment of the present invention.
  • a transistor or a memory cell 20 is formed on a substrate 10.
  • the substrate 10 may comprise a semiconductor substrate such as a silicon substrate.
  • the substrate 10 may be formed of paper, paper coated with parylene, or an organic material such as flexible plastic.
  • the available organic materials may include polyimide (PI), polycarbonate (PC), polyethersulfone (PES), polyetheretherketone (PEEK), polybutyleneterephthalate (PBT), polyethyleneterephthalate (PET), polyvinylchloride (PVC), polyethylene (PE), ethylene copolymer, polypropylene (PP), propylene copolymer, poly (4- methyl-1-pentene) (TPX) , polyarylate (PAR), polyacetal (POM), polyphenyleneoxide (PPO) , polysulfone (PSF) , polyphenylenesulfide (PPS), polyvinylidenechloride (PVDC), polyvinylacetate (PVAC) , polyvinylalcohol (PVA) , polyvinylacetal (PVAL), polystyrene (PS), AS resin, ABS resin, polymethylmethacrylate (PMMA) , fluorocarbon resin, phenol-formaldehyde (
  • a gate electrode 21 is formed on the substrate 10 as a lower electrode in a well known method.
  • the gate electrode 21 may be formed of at least one selected from the group consisting of conductive metals including gold (Au) , silver (Ag), aluminum (Al), platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiO 3 ), conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3,4- ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
  • conductive metals including gold (Au) , silver (Ag), aluminum (Al), platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiO 3
  • an organic semiconductor layer as a channel forming layer 22 is formed to coat the overall surface of the gate electrode 21 and the substrate 10.
  • the organic semiconductor layer may be formed of at least one selected from the group consisting of Cu-phthalocyanine, polyacetylene, merocyanine, polythiophene, phthalocyanine, poly (3-hexylthiophene) , poly (3-alkylthiophene) , ⁇ - sexithiophene, pentacene, ⁇ - ⁇ -dihexyl-sexithiophene, polythienylenevinylene, bis (dithienothiophene) , ⁇ - ⁇ - dihexyl-quaterthiophene, dihexyl-anthradithiophene, ⁇ - ⁇ - dihexyl-quinquethiophene, F8T2, Pc 2 Lu, Pc 2 Tm, C 6 o/C 7 o, TCNQ, C 60 ,
  • the channel forming layer 22 may be formed of an inorganic semiconductor layer such as silicon besides the organic materials.
  • an insulating layer may be used as the channel forming layer 22.
  • the insulating layer may be formed of an inorganic material such as ZrC> 2 , SiC> 4 , Y 2 ⁇ 3 , and CeO 2 , or an organic material such as BCB, polyimide, acryl, parylene C, PMMA, and CYPE.
  • the channel forming layer 22 is to form a channel of the ferroelectric memory device.
  • a ferroelectric layer 23 is formed in a region corresponding to the gate electrode 21 on the channel forming layer 22.
  • the ferroelectric layer 23 may be formed of a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material as describe above.
  • a drain electrode 24 and a source electrode 25 are formed on both lateral sides of the ferroelectric layer 23 as upper electrodes .
  • the drain electrode 24 and the source electrode 25 may be formed of at least one selected from the group consisting of conductive metals including gold (Au) , silver (Ag) , aluminum (Al), platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiO 3 ) , conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3, 4- ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
  • conductive metals including gold (Au) , silver (Ag) , aluminum (Al), platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiO 3 )
  • conductive metal oxides conductive metal alloys
  • the ferroelectric layer 23 since the ferroelectric layer 23 has polarization characteristics according to a voltage applied to the gate electrode 21, a predetermined channel is formed in the channel forming layer 22 by the polarization characteristics of the ferroelectric layer 23, and thus the drain electrode 24 and the source electrode 25 are in either a conductive or non-conductive state through the channel region.
  • all of the commercialized memory devices have a 1T-1C (one transistor-one capacitor structure) structure. These memory devices write and read data to and from the capacitor by charging or discharging a predetermined voltage in the capacitor through on/off operation of the transistor.
  • 1T-1C one transistor-one capacitor structure
  • the ferroelectric layer 23 has polarization characteristics according to a voltage applied to the gate electrode 21 and such polarization characteristics are maintained constant even in the case where the voltage is cut off. Accordingly, in case of the memory device having the above structure, it is possible to configure a non-volatile memory device with a simple IT structure, in which a source electrode of a ferroelectric memory device 40 is ground and data is read through a drain electrode, as shown in FIG. 7.
  • FIG. 8 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a second embodiment of the present invention.
  • a first memory cell 80 is formed on a substrate 70, and an insulating layer 90 is formed of polyimide (PI), for example, on the first memory cell 80.
  • PI polyimide
  • the substrate 70 may be formed of a semiconductor substrate such as a silicon substrate.
  • the substrate 10 may be formed of paper, paper coated with parylene, or an organic material such as flexible plastic.
  • the available organic materials may include polyimide (PI), polycarbonate (PC), polyethersulfone (PES), polyetheretherketone (PEEK), polybutyleneterephthalate (PBT), polyethyleneterephthalate (PET) , polyvinylchloride (PVC) , polyethylene (PE) , ethylene copolymer, polypropylene (PP) , propylene copolymer, poly (4-methyl-l-pentene) (TPX), polyarylate (PAR) , polyacetal (POM) , polyphenyleneoxide (PPO), polysulfone (PSF), polyphenylenesulfide (PPS), polyvinylidenechloride (PVDC) , polyvinylacetate (PVAC) , polyvinylalcohol (PVA
  • the memory cells 80 and 100 are sequentially stacked on the substrate 70.
  • a gate electrode 81 is formed as a lower electrode and a channel forming layer 82 is formed on the gate electrode 81.
  • a ferroelectric layer 83 is formed on a region corresponding to the gate electrode 81 on the channel forming layer 82.
  • the ferroelectric layer 83 is formed of a ferroelectric material in accordance with the present invention, i.e., a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material.
  • a drain electrode 84 and a source electrode 85 are formed on both lateral sides of the ferroelectric layer 83 as upper electrodes .
  • the second memory cell 100 has substantially the same structure as the first memory cell 80, in which a gate electrode 101, a channel forming layer 102 and a ferroelectric layer 103 are sequentially stacked.
  • the ferroelectric layer 103 of the second memory cell 100 may be formed of a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material, like the first memory cell 80.
  • the ferroelectric layer 83 and the ferroelectric layer 103 may not be formed of the same material, but may be formed of different materials, if necessary.
  • the ferroelectric material 83 may be formed of a mixture of an inorganic ferroelectric material and an organic material
  • the ferroelectric layer 103 may be formed of a mixture of an inorganic ferroelectric material and an organic ferroelectric material
  • the ferroelectric layers 83 and 103 may be formed of any kind of ferroelectric mixture provided by the present invention.
  • the gate electrodes 81 and 101 may be formed of at least one selected from the group consisting of conductive metals including gold (Au) , silver (Ag) , aluminum (Al) , platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiOa) , conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3,4- ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
  • conductive metals including gold (Au) , silver (Ag) , aluminum (Al) , platinum (Pt), indium tin oxide (ITO), and
  • the channel forming layer may be formed of at least one selected from the group consisting of Cu-phthalocyanine, polyacetylene, merocyanine, polythiophene, phthalocyanine, poly (3-hexylthiophene) , poly (3-alkylthiophene) , ⁇ - sexithiophene, pentacene, ⁇ - ⁇ -dihexyl-sexithiophene, polythienylenevinylene, bis (dithienothiophene) , ⁇ - ⁇ - dihexyl-quaterthiophene, dihexyl-anthradithiophene, ⁇ - ⁇ - dihexyl-quinquethiophene, F8T2, Pc 2 Lu, Pc 2 Tm, C 60 ZC 70 , TCNQ, C 60 , PTCDI-Ph, TCNNQ, NTCDI, NTCDA, PTCDA, Fl ⁇ CuP
  • the insulating layers may be formed of an inorganic material such as ZrO 2 , SiO 4 , Y 2 O 3 , and CeO 2 , or an organic material such as BCB, polyimide, acryl, parylene C, PMMA, and CYPE.
  • the channel forming layers 82 and 102 are to form channels of the ferroelectric memory device.
  • the drain electrodes 84 and 104 and the source electrodes 85 and 105 may be formed of at least one selected from the group consisting of conductive metals including gold (Au), silver (Ag), aluminum (Al), platinum (Pt), indium tin oxide (ITO) , and strontiumtitanate (SrTiOa) , conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3, 4-ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
  • conductive metals including gold (Au), silver (Ag), aluminum (Al), platinum (Pt), indium tin oxide (ITO) , and strontiumtitanate (SrTiOa)
  • conductive metal oxides conductive metal alloys
  • the ferroelectric layers 83 and 103 have polarization characteristics according to voltages applied to the gate electrodes 81 and 101, channels are formed in the channel forming layers 82 and 102 by the polarization characteristics of the ferroelectric layers 83 and 103, and thus the drain electrodes 84 and 104 and the source electrode 85 and 105 are in either a conductive or non-conductive state through the channel regions.
  • a conductive layer 51 such as gold (Au) is deposited on a substrate such as a semiconductor wafer, paper, paper coated with parylene, or plastic (FIGS. 9A and 9B), and a photoresist 52 is applied thereto by a spin coating method (FIG. 9C) .
  • the photoresist 52 is removed except for the area for forming a gate electrode, using a remover such as acetone (FIG. 9D) , and the conductive layer 51 is etched using the remaining photoresist 52 as a mask to form a gate electrode 81 (FIG. 9E) .
  • a channel forming layer 82 is formed on the overall surface of the structure by a spin coating method (FIG. 9F) .
  • a ferroelectric solution in accordance with the present invention is coated on the channel forming layer 82 by a spin coating, ink-jet printing, or screen printing method, and the resulting layer is baked at a low temperature below 200 ° C , for example, thus forming a ferroelectric layer 83 (FIG. 9G) .
  • the ferroelectric layer 83 except for the area corresponding to the gate electrode 81 is removed using a photoresist 53 by a buffered oxide etching (BOE) , two-step etching using BOE and gold etchant, or reactive ion etching (RIE) method (FIGS. 9H to 9J), and the photoresist 53 formed on the ferroelectric layer 83 is removed (FIG. 9K) .
  • BOE buffered oxide etching
  • RIE reactive ion etching
  • a photoresist 54 is applied to the ferroelectric layer 83, a conductive layer 55 such as gold (Au) , for example, is deposited on the overall surface of the resulting structure to form a drain electrode 84 and a source electrode 85, and then the photoresist 54 and the conductive layer 55 on the ferroeLectric layer 83 are removed by a lift-off method, thus forming a first memory cell 80 (FIGS. 9L to 90) .
  • a conductive layer 55 such as gold (Au)
  • an insulating layer 90 is formed of polyimide (PI) , for example, on the overall surface of the first memory cell 80, and the insulating layer is planarized (FIG. 9P) .
  • PI polyimide
  • a second memory cell 100 is formed on the top of the planarized insulating layer 90 by repeatedly carrying out the processes of FIGS. 9A to 90.
  • a gate electrode 101 of the second memory cell 100 is formed through the insulating layer 90 on the ferroelectric layer 83 of the first memory cell 80. Accordingly, in this case, the ferroelectric layer 83 provided in the first memory cell 80 may be affected by the voltage applied to the gate electrode 101, thus degrading the data retention characteristics of the first memory cell 80.
  • FIG. 10 shows a ferroelectric memory device in accordance with another embodiment of the present invention, in which substantially the same elements as those of FIG. 8 have the same reference numerals and their detailed description will be omitted.
  • a ferroelectric layer 103 of a second memory cell 100 is formed on the top of the insulating layer 90.
  • a channel forming layer 102 is formed to coat the overall surface of the ferroelectric layer 103, and a gate electrode 101 is formed in a region corresponding to the ferroelectric layer 103 on the channel forming layer 102. Since the ferroelectric layer 103 of the second memory cell 100 also has polarization characteristics according to a voltage applied to the gate electrode 101, a channel is formed in the channel forming layer 102 by the polarization characteristics of the ferroelectric layer 103, and thus the drain electrode 104 and the source electrode 105 are in either a conductive or non-conductive state through the channel region.
  • the ferroelectric layers 83 and 103 of the first and second memory cells 80 and 100 are arranged adjacent to each other through the insulating layer 90, and the respective gate electrodes 81 and 101 are arranged at positions that are the most distant from the other memory cells. Accordingly, the ferroelectric layer 83 of the first memory cell 80 may not be affected by the gate voltage of the second memory cell 100, differently from the above embodiment .
  • a gate electrode is disposed at the bottom thereof, the same as the gate electrode 81 of the first memory cell 80, so that the gate electrode may be arranged adjacent to the gate electrode of the second memory cell 100.
  • FIGS. 11A to HD are cross-sectional views showing various examples of the ferroelectric memory device in accordance with the present invention, in which a gate electrode 21 and a ferroelectric layer 23 are directly connected to each other, and a channel forming layer 22 is formed on the side of the ferroelectric layer 23 opposite to the gate electrode 21.
  • FIG. HA shows a staggered structure
  • FIG. ILB shows an inverted staggered structure
  • FIG. HC shows a coplanar structure
  • FIG. HD shows an inverted coplanar structure.
  • FIGS. HA to HD the same elements as those of FIG. ⁇ have the same reference numerals.
  • FIGS. HA to HD the same elements as those of FIG. ⁇ have the same reference numerals. In the structure of FIGS.
  • the channel forming layer 22 it is possible to use an insulating layer instead of the channel forming layer 22. That is, as the channel forming layer 22, any type capable of forming a channel according to an applied voltage is available.
  • a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material is used as the ferroelectric material, and the memory devices having a IT structure using the ferroelectric material are sequentially stacked to form a plurality of memory cells. Accordingly, it is possible to configure the ferroelectric memory cell through a relatively low temperature process and form the plurality of memory cells in the same area.

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Abstract

Disclosed herein are a ferroelectric memory device and a field-effect transistor (FET), in which hysteresis and remanent polarization characteristics of a ferroelectric material used are significantly improved to ensure a stable memory operation, and methods of manufacturing the same. The ferroelectric memory device and the FET in accordance with the present invention include: a substrate 10; a gate electrode 21 formed on the substrate 10; a channel forming layer 22 formed on the gate electrode 21; and a ferroelectric layer 23 formed on the channel forming layer 22, the ferroelectric layer 23 being composed of a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material.

Description

[DESCRIPTION]
[invention Title]
FERROELECTRIC MEMORY DEVICE, FET, AND METHODS OF MANUFACTURING THE SAME
[Technical Field]
The present invention relates to a ferroelectric memory device, a field-effect transistor (FET) , and methods of manufacturing the same.
[Background Art]
At present, most electronic devices including personal computers necessarily adopt various kinds of memory devices . Such memory devices are broadly classified into read only memories (ROMs) such as an electrically programmable ROM
(EPROM) , an electrically erasable PROM (EEPROM) and a flash ROM, and random access memories (RAMs) such as a static RAM (SRAM), a dynamic RAM and a ferroelectric RAM. In general, the memory devices are composed of a capacitor and a transistor formed on a semiconductor wafer such as a silicon wafer.
The conventional memory devices have been studied to increase the density of memory cells. However, since a nonvolatile memory device capable of maintaining stored data even if a power supply is cut off has attracted much attention, extensive research aimed at using a ferroelectric material as a material for a memory device has continued to progress .
At present, as the ferroelectric materials used in the memory devices, inorganic materials such as lead zirconate titanate (PZT), Strontium bismuth tantalate (SBT), lanthanum-substituted bismuth titanate (BLT) , and the like are mainly used. However, the inorganic ferroelectric materials have some drawbacks in that they are expensive, polariby characteristics are degraded with the passage of time, bhey require a high temperature treatment during the thin film formation, and they require expensive equipment.
In view of the above circumstances, the applicant and the inventor have disclosed ferroelectric memory devices using organic materials in Korean Patent Application Nos . 2005-0036167, 2006-0003399 and 2006-0041814.
However, the memory devices using the organic materials have drawbacks in that it is difficult to achieve a high density in the same memory structure compared with the conventional memory devices using inorganic materials.
[Disclosure] [Technical Problem]
Accordingly, the present invention has been made in an effort to solve the above-described problems. The present invention provides a ferroelectric memory device capable of being easily manufactured at low cost, having excellent polarization characteristics, and providing a greater number of memory cells in the same area, a field-effect transistor (FET), and methods of manufacturing the same.
[Technical Solution]
In accordance with a first aspect of the present invention, there is provided a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
In accordance with a second aspect of the present invention, there is provided a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer. In accordance with a third aspect of the present invention, there is provided a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer. In accordance with a fourth aspect of the present invention, there is provided a ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
The channel forming layer may be an organic or inorganic semiconductor layer.
The channel forming layer may be an insulating layer. The substrate may be formed of at least one selected from the group consisting of polyimide (PI), polycarbonate (PC) , polyethersulfone (PES) , polyetheretherketone (PEEK) , polybutyleneterephthalate (PBT) , polyethyleneterephthalate (PET) , polyvinylchloride (PVC) , poLyethylene (PE) , ethylene copolymer, polypropylene (PP), propylene copolymer, poly (4- methyl-1-pentene) (TPX) , polyarylate (PAR), polyacetal (POM), polyphenyleneoxide (PPO) , polysulfone (PSF) , polyphenylenesulfide (PPS) , polyvinylidenechloride (PVDC) , polyvinylacetate (PVAC), polyvinylalcohol (PVA), polyvinylacetal (PVAL), polystyrene (PS), AS resin, ABS resin, polymethylmethacrylate (PMMA) , fluorocarbon resin, phenol-formaldehyde (PF) resin, melamine-formaldehyde (MF) resin, urea-formaldehyde (UF) resin, unsaturated polyester (UP) resin, epoxy (EP) resin, diallylphthalate (DAP) resin, polyurethane (PUR) , polyamide (PA) , silicon (SI) resin or their mixtures and compounds.
The substrate may be formed of a material including paper.
The inorganic ferroelectric material may comprise at least one selected from the group consisting of a ferroelectric oxide, a ferroelectric fluoride, a ferroelectric semiconductor, and a mixture thereof. The mixture may further comprise a suicide, a silicate or any other metal.
The organic material may be a polymer ferroelectric material.
The polymer ferroelectric material may comprise at least one selected from the group consisting of polyvinylidene fluoride (PVDF), PVDF polymer, PVDF copolymer, PVDF terpolymer and, further, odd-numbered nylon, cyano- polymer, and polymer or copolymer thereof.
The polymer ferroelectric material may be PVDF-TrFE. The ferroelectric layer may be formed by heating and baking a mixed solution of an inorganic ferroelectric solution and an organic solution.
In accordance with a fifth aspect of the present invention, there is provided a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
In accordance with a sixth aspect of the present invention, there is provided a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
In accordance with a seventh aspect of the present invention, there is provided a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
In accordance with an eighth aspect of the present invention, there is provided a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer . An insulating layer may be formed between the memory cells, the insulating layer being formed of an organic material .
The ferroelectric layers of the stacked memory cells may be arranged adjacent to each other. The gate electrodes of the stacked memory cells may be arranged adjacent to each other.
In accordance with a ninth aspect of the present invention, there is provided a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
In accordance with a tenth aspect of the present invention, there is provided a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer. In accordance with an eleventh aspect of the present invention, there is provided a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
In accordance with a twelfth aspect of the present invention, there is provided a field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
In accordance with a thirteenth aspect of the present invention, there is provided a method of manufacturing a ferroelectric memory device including a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, the method comprising: forming the gate electrode; forming the channel forming layer; forming the ferroelectric layer using a mixture of an inorganic ferroelectric material and an organic material; and forming the drain and source electrodes .
In accordance with a fourteenth aspect of the present invention, there is provided a method of manufacturing a ferroelectric memory device including a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, the method comprising: forming the gate electrode; forming the channel forming layer; forming the ferroelectric layer using a mixture of a solid solution of an inorganic ferroelectric material and an organic material; and forming the drain and source electrodes .
In accordance with a fifteenth aspect of the present invention, there is provided a method of manufacturing a ferroelectric memory device, the method comprising: forming a first memory cell on a substrate; forming an insulating layer on the first memory cell; and forming a second memory cell on the insulating layer, wherein forming the first and second memory cells comprise forming a gate electrode, forming a channel forming layer, forming a ferroelectric layer using a mixture of an inorganic ferroelectric material and an organic material, and forming drain and source electrodes, respectively.
In accordance with a sixteenth aspect of the present invention, there is provided a method of manufacturing a ferroelectric memory device, the method comprising: forming a first memory cell on a substrate; forming an insulating layer on the first memory cell; and forming a second memory cell on the insulating layer, wherein forming the first and second memory cells comprise forming a gate electrode, forming a channel forming layer, forming a ferroelectric layer using a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and forming drain and source electrodes, respectively.
In accordance with a seventeenth aspect of the present invention, there is provided a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein each of the ferroelectric layers of the stacked memory cells is formed of a mixture of an inorganic ferroelectric material and an organic material, the mixtures being different from each other, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
In accordance with an eighteenth aspect of the present invention, there is provided a ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein each of the ferroelectric layers of the stacked memory cells is formed of a mixture of an inorganic ferroelectric material and an organic material, the mixtures being different from each other, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
The channel forming layer may be formed between the gate electrode and the ferroelectric layer. The ferroelectric layer may be formed between the gate electrode and the channel forming layer.
The organic material may have ferroelectric characteristics .
In the process of forming the ferroelectric layer, a mixed solution of an inorganic ferroelectric solution and an organic solution may be coated on the substrate to form a ferroelectric film, and the ferroelectric film may be heated, baked and etched to form the ferroelectric layer.
The mixed solution may comprise a PZT solution and a PVDF-TrFE solution.
The PZT solution may be prepared by mixing a PZO solution and a PTO solution.
The PVDF-TrFE solution may be prepared by dissolving PVDF-TrFE powder in at least one solvent selected from the group consisting of C4H5O (THF), C4H8O (MEK), C3H6O (acetone), C3H7NO (DMF), and C2H6OS (DMSO).
The ferroelectric layer may be formed by a spin coating, ink-jet printing, or screen printing method.
The process of etching the ferroelectric layer may be performed by a buffered oxide etching (BOE) method.
The process of etching the ferroelectric layer may be performed by a two-step etching method using BOE and gold etchant .
The process of etching the ferroelectric layer may be performed by a reactive ion etching (RIE) method.
The baking temperature may be below 200°C.
[Description of Drawings]
FIGS. 1 to 5 are graphs showing capacitance-voltage characteristics of ferroelectric materials applied to the present invention;
FIG. 6 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a first embodiment of the present invention; FIG. 7 is an equivalent circuit diagram of the memory device shown in FIG. 6;
FIG. 8 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a second embodiment of the present invention; FIGS. 9A to 9P are cross-sectional views showing manufacturing processes of the ferroelectric memory device shown in FIG. 8;
FIG. 10 is a cross-sectional view showing a modified structure of the ferroelectric memory device shown in FIG. 8 ; and
FIGS. HA to HD are cross-sectional views showing other examples of the ferroelectric memory device in accordance with the present invention.
[Mode for Invention]
Hereinafter, preferred embodiments in accordance with the present invention will be described with reference to the accompanying drawings. The preferred embodiments are provided so that those skilled in the art can sufficiently understand the present invention, but can be modified in various forms and the scope of the present invention is not limited to the preferred embodiments.
First, the basic concept of the present invention will be described below. At present, there are known various materials showing ferroelectric characteristics. Such materials are broadly classified into inorganic materials and organic materials. The inorganic ferroelectric materials include ferroelectric oxides, ferroelectric fluorides such as BaMgF4 (BMF) , and ferroelectric semiconductors. The organic ferroelectric materials include polymer ferroelectric materials and the like.
The ferroelectric oxides include perovskite ferroelectric materials such as PbZrxTii_xO3 (PZT) , BaTiO3 and PBTiO3, pseudo-ilmenite ferroelectric materials such as LiNbO3 and LiTaO3, tungsten-bronze (TB) ferroelectric materials such as PbNb3O6 and Ba2NaNb5Oi5, ferroelectric materials having a bismuth layer structure such as SrBi2Ta2O9 (SBT), (Bi, La)4Ti3Oi2 (BLT) and Bi4Ti3Oi2, pyrochlore ferroelectric materials such as La2Ti2O7, and ferroelectric materials such as RMnO3, Pb5Ge3On (PGO) and BiFeO3 (BFO) including a rare earth element (R) such as Y, Er, Ho, Tm, Yb and Lu .
Moreover, the ferroelectric semiconductors include 2-6 compounds such as CdZnTe, CdZnS, CdZnSe, CdMnS, CdFeS, CdMnSe and CdFeSe.
Furthermore, the polymer ferroelectric materials include polyvinylidene fluoride (PVDF), PVDF polymer, PVDF copolymer, PVDF terpolymer and, further, odd-numbered nylon, cyano-polymer, and polymer or copolymer thereof.
In general, the inorganic ferroelectric materials including the ferroelectric oxides, the ferroelectric fluorides and the ferroelectric semiconductors have dielectric constants greater than those of the organic ferroelectric materials. Accordingly, the generally proposed ferroelectric field-effect transistor (FET) or ferroelectric memory device employs the inorganic ferroelectric materials for forming the ferroelectric layer.
However, the above-described inorganic ferroelectric materials require a high temperature treatment above 500 °C, for example, to be formed on a substrate. In the case where an inorganic ferroelectric layer is formed through the high temperature treatment on the substrate, a transition layer of low quality is formed on the boundary between the ferroelectric layer and a silicon substrate due to the high temperature, and chemical elements such as Pb and Bi in the ferroelectric material are diffused into the silicon substrate, thus shortening the data retention time of the ferroelectric memory. In the present invention, a mixture of an inorganic ferroelectric material and an organic material or an organic ferroelectric material is used as the ferroelectric material,
According to the study by the present inventor, the inorganic ferroelectric materials are formed at higher temperatures, while their dielectric constants are high. However, the organic materials including the organic ferroelectric materials are formed at lower temperatures, while their dielectric constants are relatively low. Accordingly, when mixing the inorganic ferroelectric material with the organic material or the organic ferroelectric material, it is possible to obtain a ferroelectric material having a dielectric constant above a predetermined value and formed at a much lower temperature.
In this case, methods of forming mixed solutions of the inorganic ferroelectric material and the organic material or the organic ferroelectric material are as follows :
1. Mixing an inorganic powder with an organic powder and dissolving the mixed powders in a solvent to form a mixed solution;
2. Dissolving an organic powder in an inorganic solution to form a mixed solution;
3. Dissolving an inorganic powder in an organic solution to form a mixed solution; and 4. Mixing an organic solution with an inorganic solution to form a mixed solution.
Moreover, the inorganic ferroelectric material and the organic material may be mixed with each other as follows:
1. Mixing an inorganic ferroelectric material with an organic material;
2. Mixing an inorganic ferroelectric material with an organic ferroelectric material;
3. Mixing a solid solution of an inorganic ferroelectric material with an organic material; 4. Mixing a solid solution of an inorganic ferroelectric material with an organic ferroelectric material; and
5. Mixing the aforementioned mixture with a suicide, a silicate or another metal. Of course, the above mixing methods are not limited to specific methods and any method that can appropriately mix the inorganic material with the organic material may be employed.
The organic materials mixed with the inorganic ferroelectric material include, a monomer, an oligomer, a polymer, and a copolymer. Preferably, an organic material having a high dielectric constant may be used.
The organic materials having a high dielectric constant include polyvinylpyrrolidone (PVP) , polycarbonate (PC) , polyvinyl chloride (PVC) , polystyrene (PS) , epoxy, polymethylmethacrylate (PMMA), polyimide (PI), polyethylene (PE) , polyvinyl alcohol (PVA) , polyhexamethylene adipamide (nylon 66), polyetherketoneketone (PEKK), and the like. Moreover, the organic materials include a nonpolar organic material, such as fluorinated para-xylene, fluoropolyarylether, fluorinated polyimide, polystyrene, poly (α-methyl styrene) , poly (α-vinylnaphthalene) , poly (vinyltoluene) , polyethylene, cis-polybutadiene, polypropylene, polyisoprene, poly (4-methyl-l-pentene) , poly (tetrafluoroethylene) , poly (chlorotrifluoroethylene) , poly (2-methyl-1, 3-butadiene) , poly (p-xylylene) , poly(α-α-α'- α'-tetrafluoro-p-xylylene) , poly [1, 1- (2-methyl propane) bis (4-phenyl) carbonate] , poly (cyclohexyl methacrylate) , poly (chlorostyrene) , poly (2, β-dimethyl-1, 4- phenylene ether), polyisobutylene, poly (vinyl cyclohexane) , poly(arylene ether), and polyphenylene, or copolymers having a low dielectric constant, such as poly (ethylene/tetrafluoroethylene) , poly (ethylene/chlorotrifluoroethylene) , fluorinated ethylene/propylene copolymer, polystyrene-co-α-methyl styrene, ethylene/ethyl acrylate copolymer, poly (styrene/10%butadiene) , poly (styrene/15%butadiene) , poly (styrene/2, 4-dimethylstyrene) , Cytop, Teflon AF, and polypropylene-co-1-butene . Other organic semi-conducting materials that can be used in this invention include soluble compounds and soluble derivatives of compounds of the following list: conjugated hydrocarbon polymers such as polyacene, polyphenylene, poly (phenylene vinylene) , polyfluorene including oligomers of those conjugated hydrocarbon polymers; condensed aromatic hydrocarbons such as anthracene, tetracene, chrysene, pentacene, pyrene, perylene, coronene; oligomeric para substituted phenylenes such as p-quaterphenyl (p-4P) , p- quinquephenyl (p—5P) , p-sexiphenyl (p—6P) ; conjugated heterocyclic polymers such as poly (3-substituted thiophene) , poly (3, 4-bisubstituted thiophene) , polybenzothiophene, polyisothianapthene, poly (N-substituted pyrrole), poly (3- substituted pyrrole), poly (3, 4-bisubstituted pyrrole), polyfuran, polypyridine, poly-1, 3, 4-oxadiazoles, polyisothianaphthene, poly (N-substituted aniline), poly (2- substituted aniline), poly (3-substituted aniline), poly (2,3- bisubstituted aniline) , polyazulene, polypyrene; pyrazoline compounds; polyselenophene; polybenzofuran; polyindole; polypyridazine; benzidine compounds; stilbene compounds; triazines; substituted metallo- or metal-free porphines, phthalocyanines, fluorophthalocyanines, naphthalocyanines, or fluoronaphthalocyanines; Cεo and C7o fullerenes; N,N'- dialkyl, substituted dialkyl, diaryl or substituted diaryl- 1, 4 , 5, 8-naphthalenetetracarboxylic diimide; N, N' -dialkyl, substituted dialkyl, diaryl or substituted diaryl 3,4,9,10- perylenetetracarboxylicdiimide; bathophenanthroline; diphenoquinones; 1, 3, 4-oxadiazoles; 11,11,12,12- tetracyanonaptho-2, β-quinodimethane; α,α' -bis (dithieno [3,2- b2 ', 3 '-d] thiophene) ; 2,8-dialkyl, substituted dialkyl, diaryl or substituted diaryl anthradithiophene; and 2,2'- bibenzo[l, 2-b: 4, 5-b' ] dithiophene.
It is possible to appropriately set the mixture ratio of the inorganic material and the organic material. If the mixture ratio of the inorganic ferroelectric material is increased, the formation temperature is increased while the dielectric constant of the mixture is increased, whereas if the mixture ratio of the inorganic ferroelectric material is decreased, the formation temperature is lowered while the dielectric constant of the mixture is reduced. The ferroelectric materials employed in the present invention have the following characteristics:
1. Since the ferroelectric layer is formed using a mixed solution of an inorganic material and an organic material, it is possible to easily form the ferroelectric layer by an ink-jet printing, spin coating or screen printing method; and
2. Since the formation temperature of the ferroelectric layer is lowered, it is possible to form the field-effect transistor or ferroelectric memory device on various kinds of substrates such as an organic material or paper instead of the existing silicon substrate. Meanwhile, FIGS. 1 to 5 are graphs showing polarization characteristics of ferroelectric layers formed of an inorganic ferroelectric material and an organic ferroelectric material such as PbZrxTii-xO3 (PZT) and PVDF- TrFE mixed in predetermined ratios .
Here, the ferroelectric layer was formed in such a manner that a PZT solution and a PVDF-TrFE solution were mixed in a predetermined ratio to form a mixed solution, the mixed solution was coated on a silicon wafer by a spin coating method, and the resulting silicon wafer was heated in the temperature range of 150 to 200°C on a hot plate for a predetermined period of time.
Moreover, the PZT solution was prepared by mixing a PZO solution and a PTO solution, in which the PZO solution was formed by mixing a zirconium propoxide solution with a mixed solution of a 2-methoxyethanol solution and a lead acetate trihydrate solution and the PTO solution was formed by mixing a titanium isopropoxide solution with the mixed solution of the 2-methoxyethanol solution and the lead acetate trihydrate solution.
The PVDF-TrFE solution was prepared by dissolving PVDF-TrFE powder in a solvent such as C4H5O (THF) , C4H8O (MEK), C3H6O (acetone), C3H7NO (DMF), and C2H6OS (DMSO). FIG. 1 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 1:1, FIG. 2 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 2:1, FIG. 3 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 3:1, FIG. 4 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 1:2, and FIG. 5 shows the polarization characteristics in which the mixed ratio of the PZT and PVDF-TrFE was 1:3. In FIGS. IA, 2A and 3A, the thickness of the ferroelectric layer was 50 nm; in FIGS. IB, 2B, 3B, 4 and 5, the thickness of the ferroelectric layer was 75 nm; and in FIG. 1C, the thickness of the ferroelectric layer was 100 nm.
Moreover, in FIGS. 1 to 5, the characteristic curves represented as A show the polarization characteristics in which the formation temperature of the ferroelectric layer was 190°C, the characteristic curves represented as B show the polarization characteristics in which the formation temperature of the ferroelectric layer was 170°C, and the characteristic curves represented as C show the polarization characteristics in which the formation temperature of the ferroelectric layer was 150 °C.
Referring to FIGS. 1 to 5, in the case where the mixed ratio of the PZT and PVDF-TrFE was 1:1 or in the case where the mixed ratio of the PVDF-TrFE was greater than that of the PZT, generally good polarization characteristics were shown in the temperature range of 150 to 190°C, and the higher the mixed ratio of the PZT was, the better the polarization characteristics were shown at higher temperatures .
Moreover, the higher the thickness of the ferroelectric layer, the lower the polarization value, i.e., the capacitance value, whereas the greater the size of the memory window. Especially, it was remarkable that, even in the case where the mixed ratio of the PZT and PVDF-TrFE was changed or in the case where the formation temperature was set to a temperature below about 200 °C, excellent hysteresis characteristics were shown. As described above, since the formation temperature of the ferroelectric layer formed of the conventional inorganic ferroelectric material is higher than that of the ferroelectric layer formed in accordance with the present invention, various problems occur when forming the ferroelectric layer on the silicon substrate. Contrarily, when the mixture of the inorganic ferroelectric material and the organic material is used, it is possible to form the ferroelectric layer at a low temperature of below 200°C and excellent hysteresis characteristics are shown in a voltage range of -5 to 5 V. Accordingly, the ferroelectric material in accordance with the present invention can be effective used as the material of the ferroelectric field-effect transistor or ferroelectric memory.
FIG. 6 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a first embodiment of the present invention.
In FIG. 6, a transistor or a memory cell 20 is formed on a substrate 10. Here, the substrate 10 may comprise a semiconductor substrate such as a silicon substrate. Moreover, the substrate 10 may be formed of paper, paper coated with parylene, or an organic material such as flexible plastic. The available organic materials may include polyimide (PI), polycarbonate (PC), polyethersulfone (PES), polyetheretherketone (PEEK), polybutyleneterephthalate (PBT), polyethyleneterephthalate (PET), polyvinylchloride (PVC), polyethylene (PE), ethylene copolymer, polypropylene (PP), propylene copolymer, poly (4- methyl-1-pentene) (TPX) , polyarylate (PAR), polyacetal (POM), polyphenyleneoxide (PPO) , polysulfone (PSF) , polyphenylenesulfide (PPS), polyvinylidenechloride (PVDC), polyvinylacetate (PVAC) , polyvinylalcohol (PVA) , polyvinylacetal (PVAL), polystyrene (PS), AS resin, ABS resin, polymethylmethacrylate (PMMA) , fluorocarbon resin, phenol-formaldehyde (PF) resin, melamine-formaldehyde (MF) resin, urea-formaldehyde (UF) resin, unsaturated polyester (UP) resin, epoxy (EP) resin, diallylphthalate (DAP) resin, polyurethane (PUR), polyamide (PA), silicon (SI) resin or their mixtures and compounds.
A gate electrode 21 is formed on the substrate 10 as a lower electrode in a well known method. The gate electrode 21 may be formed of at least one selected from the group consisting of conductive metals including gold (Au) , silver (Ag), aluminum (Al), platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiO3), conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3,4- ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
Next, an organic semiconductor layer as a channel forming layer 22 is formed to coat the overall surface of the gate electrode 21 and the substrate 10. The organic semiconductor layer may be formed of at least one selected from the group consisting of Cu-phthalocyanine, polyacetylene, merocyanine, polythiophene, phthalocyanine, poly (3-hexylthiophene) , poly (3-alkylthiophene) , α - sexithiophene, pentacene, α- ω-dihexyl-sexithiophene, polythienylenevinylene, bis (dithienothiophene) , α-ω- dihexyl-quaterthiophene, dihexyl-anthradithiophene, α-ω- dihexyl-quinquethiophene, F8T2, Pc2Lu, Pc2Tm, C6o/C7o, TCNQ, C60, PTCDI-Ph, TCNNQ, NTCDI, NTCDA, PTCDA, FlβCuPc, NTCDI- C8F, DHF-βT, and PTCDI-C8.
Moreover, the channel forming layer 22 may be formed of an inorganic semiconductor layer such as silicon besides the organic materials.
Furthermore, an insulating layer may be used as the channel forming layer 22. In this case, the insulating layer may be formed of an inorganic material such as ZrC>2, SiC>4, Y2θ3, and CeO2, or an organic material such as BCB, polyimide, acryl, parylene C, PMMA, and CYPE.
The channel forming layer 22 is to form a channel of the ferroelectric memory device.
A ferroelectric layer 23 is formed in a region corresponding to the gate electrode 21 on the channel forming layer 22. Here, the ferroelectric layer 23 may be formed of a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material as describe above. A drain electrode 24 and a source electrode 25 are formed on both lateral sides of the ferroelectric layer 23 as upper electrodes .
The drain electrode 24 and the source electrode 25 may be formed of at least one selected from the group consisting of conductive metals including gold (Au) , silver (Ag) , aluminum (Al), platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiO3) , conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3, 4- ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
In the above structure, since the ferroelectric layer 23 has polarization characteristics according to a voltage applied to the gate electrode 21, a predetermined channel is formed in the channel forming layer 22 by the polarization characteristics of the ferroelectric layer 23, and thus the drain electrode 24 and the source electrode 25 are in either a conductive or non-conductive state through the channel region.
In general, all of the commercialized memory devices have a 1T-1C (one transistor-one capacitor structure) structure. These memory devices write and read data to and from the capacitor by charging or discharging a predetermined voltage in the capacitor through on/off operation of the transistor.
In the above structure, the ferroelectric layer 23 has polarization characteristics according to a voltage applied to the gate electrode 21 and such polarization characteristics are maintained constant even in the case where the voltage is cut off. Accordingly, in case of the memory device having the above structure, it is possible to configure a non-volatile memory device with a simple IT structure, in which a source electrode of a ferroelectric memory device 40 is ground and data is read through a drain electrode, as shown in FIG. 7.
FIG. 8 is a cross-sectional view showing a structure of a ferroelectric memory device in accordance with a second embodiment of the present invention. In FIG. 8, a first memory cell 80 is formed on a substrate 70, and an insulating layer 90 is formed of polyimide (PI), for example, on the first memory cell 80. Then, a second memory cell 100 is formed on the insulating layer 90.
The substrate 70 may be formed of a semiconductor substrate such as a silicon substrate. Moreover, the substrate 10 may be formed of paper, paper coated with parylene, or an organic material such as flexible plastic. The available organic materials may include polyimide (PI), polycarbonate (PC), polyethersulfone (PES), polyetheretherketone (PEEK), polybutyleneterephthalate (PBT), polyethyleneterephthalate (PET) , polyvinylchloride (PVC) , polyethylene (PE) , ethylene copolymer, polypropylene (PP) , propylene copolymer, poly (4-methyl-l-pentene) (TPX), polyarylate (PAR) , polyacetal (POM) , polyphenyleneoxide (PPO), polysulfone (PSF), polyphenylenesulfide (PPS), polyvinylidenechloride (PVDC) , polyvinylacetate (PVAC) , polyvinylalcohol (PVA) , polyvinylacetal (PVAL) , polystyrene (PS), AS resin, ABS resin, polymethylmethacrylate (PMMA), fluorocarbon resin, phenol-formaldehyde (PF) resin, melamine-formaldehyde (MF) resin, urea-formaldehyde (UF) resin, unsaturated polyester (UP) resin, epoxy (EP) resin, diallylphthalate (DAP) resin, polyurethane (PUR) , polyamide (PA), silicon (SI) resin or their mixtures and compounds. The memory cells 80 and 100 are sequentially stacked on the substrate 70. In this embodiment, although the description has been given to the case where the memory cells are formed on the substrate Ln a double layer, it is possible to form the memory cells Ln a multiple layer, if necessary.
In the first memory cell 80, a gate electrode 81 is formed as a lower electrode and a channel forming layer 82 is formed on the gate electrode 81. Subsequently, a ferroelectric layer 83 is formed on a region corresponding to the gate electrode 81 on the channel forming layer 82. Here, the ferroelectric layer 83 is formed of a ferroelectric material in accordance with the present invention, i.e., a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material. Then, a drain electrode 84 and a source electrode 85 are formed on both lateral sides of the ferroelectric layer 83 as upper electrodes . The second memory cell 100 has substantially the same structure as the first memory cell 80, in which a gate electrode 101, a channel forming layer 102 and a ferroelectric layer 103 are sequentially stacked.
The ferroelectric layer 103 of the second memory cell 100 may be formed of a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material, like the first memory cell 80.
Especially, the ferroelectric layer 83 and the ferroelectric layer 103 may not be formed of the same material, but may be formed of different materials, if necessary. For example, the ferroelectric material 83 may be formed of a mixture of an inorganic ferroelectric material and an organic material, and the ferroelectric layer 103 may be formed of a mixture of an inorganic ferroelectric material and an organic ferroelectric material
That is, the ferroelectric layers 83 and 103 may be formed of any kind of ferroelectric mixture provided by the present invention. The gate electrodes 81 and 101 may be formed of at least one selected from the group consisting of conductive metals including gold (Au) , silver (Ag) , aluminum (Al) , platinum (Pt), indium tin oxide (ITO), and strontiumtitanate (SrTiOa) , conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3,4- ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials. The channel forming layer may be formed of at least one selected from the group consisting of Cu-phthalocyanine, polyacetylene, merocyanine, polythiophene, phthalocyanine, poly (3-hexylthiophene) , poly (3-alkylthiophene) , α- sexithiophene, pentacene, α - ω-dihexyl-sexithiophene, polythienylenevinylene, bis (dithienothiophene) , α-ω- dihexyl-quaterthiophene, dihexyl-anthradithiophene, α - ω - dihexyl-quinquethiophene, F8T2, Pc2Lu, Pc2Tm, C60ZC70, TCNQ, C60, PTCDI-Ph, TCNNQ, NTCDI, NTCDA, PTCDA, FlβCuPc, NTCDI- C8F, DHF-6T, and PTCDI-C8.
Moreover, it is possible to use insulating layers as the channel forming layers 82 and L02. In this case, the insulating layers may be formed of an inorganic material such as ZrO2, SiO4, Y2O3, and CeO2, or an organic material such as BCB, polyimide, acryl, parylene C, PMMA, and CYPE.
The channel forming layers 82 and 102 are to form channels of the ferroelectric memory device.
The drain electrodes 84 and 104 and the source electrodes 85 and 105 may be formed of at least one selected from the group consisting of conductive metals including gold (Au), silver (Ag), aluminum (Al), platinum (Pt), indium tin oxide (ITO) , and strontiumtitanate (SrTiOa) , conductive metal oxides, conductive metal alloys, and conductive metal compounds and, further, conductive organics with a conductive polymer as a substrate such as polyaniline and poly (3, 4-ethylenedioxythiophene) /poly (styrenesulfonate) (PEDOT/PSS) , conductive organic mixtures, conductive organic compounds, and conductive organic multilayer materials.
In the above structure, since the ferroelectric layers 83 and 103 have polarization characteristics according to voltages applied to the gate electrodes 81 and 101, channels are formed in the channel forming layers 82 and 102 by the polarization characteristics of the ferroelectric layers 83 and 103, and thus the drain electrodes 84 and 104 and the source electrode 85 and 105 are in either a conductive or non-conductive state through the channel regions.
Next, the manufacturing processes of the ferroelectric memory device in accordance with the present invention will be described with reference to FIGS. 9A to 9P. A conductive layer 51 such as gold (Au) is deposited on a substrate such as a semiconductor wafer, paper, paper coated with parylene, or plastic (FIGS. 9A and 9B), and a photoresist 52 is applied thereto by a spin coating method (FIG. 9C) . Subsequently, the photoresist 52 is removed except for the area for forming a gate electrode, using a remover such as acetone (FIG. 9D) , and the conductive layer 51 is etched using the remaining photoresist 52 as a mask to form a gate electrode 81 (FIG. 9E) . Then, the photoresist 52 on the gate electrode 81 is removed, and a channel forming layer 82 is formed on the overall surface of the structure by a spin coating method (FIG. 9F) . Next, a ferroelectric solution in accordance with the present invention is coated on the channel forming layer 82 by a spin coating, ink-jet printing, or screen printing method, and the resulting layer is baked at a low temperature below 200 °C , for example, thus forming a ferroelectric layer 83 (FIG. 9G) .
Next, the ferroelectric layer 83 except for the area corresponding to the gate electrode 81 is removed using a photoresist 53 by a buffered oxide etching (BOE) , two-step etching using BOE and gold etchant, or reactive ion etching (RIE) method (FIGS. 9H to 9J), and the photoresist 53 formed on the ferroelectric layer 83 is removed (FIG. 9K) . Subsequently, in the same method as described above, a photoresist 54 is applied to the ferroelectric layer 83, a conductive layer 55 such as gold (Au) , for example, is deposited on the overall surface of the resulting structure to form a drain electrode 84 and a source electrode 85, and then the photoresist 54 and the conductive layer 55 on the ferroeLectric layer 83 are removed by a lift-off method, thus forming a first memory cell 80 (FIGS. 9L to 90) .
After the formation of the first memory cell 80 as described above, an insulating layer 90 is formed of polyimide (PI) , for example, on the overall surface of the first memory cell 80, and the insulating layer is planarized (FIG. 9P) .
Next, a second memory cell 100 is formed on the top of the planarized insulating layer 90 by repeatedly carrying out the processes of FIGS. 9A to 90.
Meanwhile, in the above structure, a gate electrode 101 of the second memory cell 100 is formed through the insulating layer 90 on the ferroelectric layer 83 of the first memory cell 80. Accordingly, in this case, the ferroelectric layer 83 provided in the first memory cell 80 may be affected by the voltage applied to the gate electrode 101, thus degrading the data retention characteristics of the first memory cell 80.
In view of the above circumstances, FIG. 10 shows a ferroelectric memory device in accordance with another embodiment of the present invention, in which substantially the same elements as those of FIG. 8 have the same reference numerals and their detailed description will be omitted.
In the structure of FIG. 10, a ferroelectric layer 103 of a second memory cell 100 is formed on the top of the insulating layer 90. A channel forming layer 102 is formed to coat the overall surface of the ferroelectric layer 103, and a gate electrode 101 is formed in a region corresponding to the ferroelectric layer 103 on the channel forming layer 102. Since the ferroelectric layer 103 of the second memory cell 100 also has polarization characteristics according to a voltage applied to the gate electrode 101, a channel is formed in the channel forming layer 102 by the polarization characteristics of the ferroelectric layer 103, and thus the drain electrode 104 and the source electrode 105 are in either a conductive or non-conductive state through the channel region.
In this embodiment, the ferroelectric layers 83 and 103 of the first and second memory cells 80 and 100 are arranged adjacent to each other through the insulating layer 90, and the respective gate electrodes 81 and 101 are arranged at positions that are the most distant from the other memory cells. Accordingly, the ferroelectric layer 83 of the first memory cell 80 may not be affected by the gate voltage of the second memory cell 100, differently from the above embodiment .
Moreover, in the case where another memory cell is stacked on the second memory cell 100 in this embodiment, a gate electrode is disposed at the bottom thereof, the same as the gate electrode 81 of the first memory cell 80, so that the gate electrode may be arranged adjacent to the gate electrode of the second memory cell 100.
The invention has been described in detail with reference to preferred embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. For example, although the description has been given with respect to the case where the respective memory cells 80 and 100 are configured in such a manner that the ferroelectric layers 83 and 103 are provided on the gate electrodes 81 and 101 through the channel forming layers 82 and 102, the ferroelectric memory device in accordance with the present invention may be configured with various structures besides the above-described memory cell structure.
That is, FIGS. 11A to HD are cross-sectional views showing various examples of the ferroelectric memory device in accordance with the present invention, in which a gate electrode 21 and a ferroelectric layer 23 are directly connected to each other, and a channel forming layer 22 is formed on the side of the ferroelectric layer 23 opposite to the gate electrode 21. FIG. HA shows a staggered structure, FIG. ILB shows an inverted staggered structure, FIG. HC shows a coplanar structure, and FIG. HD shows an inverted coplanar structure. In FIGS. HA to HD, the same elements as those of FIG. β have the same reference numerals. In the structure of FIGS. HA to HD, since the polarization is generated in the ferroelectric layer 23 when a specific voltage is applied to the gate electrode 21, a channel is formed in the channel forming layer 22 by the polarization of the ferroelectric layer 23, and thus the drain electrode 24 and the source electrode 25 are in either a conductive or non-conductive state through the channel region.
Moreover, in the structures of FIGS. HA to HD, it is possible to use an insulating layer instead of the channel forming layer 22. That is, as the channel forming layer 22, any type capable of forming a channel according to an applied voltage is available.
[industrial Applicability]
As described above, according to the present invention, a mixture of an inorganic ferroelectric material or a solid solution thereof and an organic material or an organic ferroelectric material is used as the ferroelectric material, and the memory devices having a IT structure using the ferroelectric material are sequentially stacked to form a plurality of memory cells. Accordingly, it is possible to configure the ferroelectric memory cell through a relatively low temperature process and form the plurality of memory cells in the same area.

Claims

[CLAIMS]
[Claim l]
A ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
[Claim 2]
The ferroelectric memory device of claim 1, wherein the channel forming layer is an organic or inorganic semiconductor layer.
[Claim 3]
The ferroelectric memory device of claim 1, wherein the channel forming layer is an insulating layer.
[Claim 4]
The ferroelectric memory device of claim 1, wherein the substrate is formed of a material selected from the group consisting of polyimide (PI), polycarbonate (PC), polyethersulfone (PES), polyetheretherketone (PEEK), polybutyleneterephthalate (PBT) , polyethyleneterephthalate (PET), polyvinylchloride (PVC), polyethylene (PE), ethylene copolymer, polypropylene (PP), propylene copolymer, poly (4- methyl-1-pentene) (TPX) , polyarylate (PAR), polyacetal (POM), polyphenyleneoxide (PPO) , polysulfone (PSF) , polyphenylenesulfide (PPS) , polyvinylidenechloride (PVDC) , polyvinylacetate (PVAC) , polyvinylalcohol (PVA) , polyvinylacetal (PVAL) , polystyrene (PS) , AS resin, ABS resin, polymethylmethacrylate (PMMA) , fluorocarbon resin, phenol-formaldehyde (PF) resin, melamine-formaldehyde (MF) resin, urea-formaldehyde (UF) resin, unsaturated polyester (UP) resin, epoxy (EP) resin, diallylphthalate (DAP) resin, polyurethane (PUR), polyamide (PA), silicon (SI) resin or their mixtures and compounds.
[Claim 5]
The ferroelectric memory device of claim 1, wherein the substrate is formed of a material including paper.
[Claim 6]
The ferroelectric memory device of claim 1, wherein the inorganic ferroelectric material comprises at least one selected from the group consisting of a ferroelectric oxide, a ferroelectric fluoride, a ferroe Lectric semiconductor, and a mixture thereof. [Claim 7]
The ferroelectric memory device of claim 1, wherein the mixture further comprises a siLicide, a silicate or any other metal .
[Claim 8]
The ferroelectric memory device of claim 1, wherein the organic material is a polymer ferroelectric material.
[Claim 9]
The ferroelectric memory device of claim 8, wherein the poLymer ferroelectric material comprises at least one selected from the group consisting of polyvinylidene fluoride (PVDF), PVDF polymer, PVDF copolymer, PVDF terpolymer and, further, odd-numbered nylon, cyano-polymer, and polymer or copolymer thereof.
[Claim 10] The ferroelectric memory device of claim 8, wherein the polymer ferroelectric material is PVDF-TrFE.
[Claim 11]
The ferroelectric memory device of claim 1, wherein the ferroelectric layer is formed by heating and baking a mixed solution of an inorganic ferroelectric solution and an organic solution.
[Claim 12] A ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
[Claim 13] The ferroelectric memory device of claim 12, wherein the mixture further comprises a suicide, a silicate or any other metal.
[Claim 14] A ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 15] The ferroelectric memory device of claim 14, wherein the channel forming layer is an organic or inorganic semiconductor layer.
[Claim 16] The ferroelectric memory device of claim 15, wherein the channel forming layer is an insulating layer.
[Claim 17]
The ferroelectric memory device of claim 14, wherein the substrate is formed of a material selected from the group consisting of polyimide (PI), polycarbonate (PC), polyethersulfone (PES) , polyetheretherketone (PEEK) , polybutyleneterephthalate (PBT), polyethyleneterephthalate (PET), polyvinylchloride (PVC), polyethylene (PE), ethylene copolymer, polypropylene (PP), propylene copolymer, poly (4- methyl-1-pentene) (TPX) , polyarylate (PAR), polyacetal (POM), polyphenyleneoxide (PPO) , polysulfone (PSF) , polyphenylenesulfide (PPS) , polyvinylidenechloride (PVDC) , polyvinylacetate (PVAC) , polyvinylalcohol (PVA) , polyvinylacetal (PVAL) , polystyrene (PS) , AS resin, ABS resin, polymethylmethacrylate (PMMA) , fluorocarbon resin, phenol-formaldehyde (PF) resin, melamine-formaldehyde (MF) resin, urea-formaldehyde (UF) resin, unsaturated polyester (UP) resin, epoxy (EP) resin, diallylphthalate (DAP) resin, polyurethane (PUR) , polyamide (PA) , silicon (SI) resin or their mixtures and compounds .
[Claim 18]
The ferroelectric memory device of claim 14, wherein the substrate is formed of a material including paper.
[Claim 19]
The ferroelectric memory device of claim 14, wherein the inorganic ferroelectric material comprises at least one selected from the group consisting of a ferroelectric oxide, a ferroelectric fluoride, a ferroelectric semiconductor, and a mixture thereof.
[Claim 20] The ferroelectric memory device of claim 14, wherein the mixture further comprises a suicide, a silicate or any other metal .
[Claim 2l] The ferroelectric memory device of claim 14, wherein the organic material is a polymer ferroelectric material.
[Claim 22]
The ferroelectric memory device of claim 21, wherein the polymer ferroelectric material comprises at least one selected from the group consisting of polyvinylidene fluoride (PVDF), PVDF polymer, PVDF copolymer, PVDF terpolymer and, further, odd-numbered nylon, cyano-polymer, and polymer or copolymer thereof.
[Claim 23]
The ferroelectric memory device of claim 21, wherein the polymer ferroelectric material is PVDF-TrFE.
[Claim 24]
The ferroelectric memory device of claim 14, wherein the ferroelectric layer is formed by heating and baking a mixed solution of an inorganic ferroelectric solution and an organic solution.
[Claim 25]
A ferroelectric memory device comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 26]
The ferroelectric memory device of claim 25, wherein the mixture further comprises a suicide, a silicate or any other metal.
[Claim 27]
A field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
[Claim 28]
A field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 29]
A field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 30]
A field-effect transistor comprising a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer. [Claim 31]
A method of manufacturing a ferroelectric memory device including a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, the method comprising: forming the gate electrode; forming the channel forming layer; forming the ferroelectric layer using a mixture of an inorganic ferroelectric material and an organic material; and forming the drain and source electrodes.
[Claim 32]
The method of claim 31, wherein the channel forming layer is formed between the gate eLectrode and the ferroelectric layer.
[Claim 33]
The method of claim 31, wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 34]
The method of claim 31, wherein the organic material has ferroelectric characteristics. [Claim 35]
The method of claim 31, wherein, in forming the ferroelectric layer, a mixed solution of an inorganic ferroelectric solution and an organic solution is coated on the substrate to form a ferroelectric film, and the ferroelectric film is heated, baked and etched to form the ferroelectric layer.
[Claim 36]
The method of claim 35, wherein the mixed solution comprises a PZT solution and a PVDF-TrFE solution.
[Claim 37] The method of claim 36, wherein the PZT solution is prepared by mixing a PZO solution and a PTO solution.
[Claim 38]
The method of claim 36 , wherein the PVDF-TrFE solution is prepared by dissolving PVDF-TrFE powder in at least one solvent selected from the group consisting of C4H5O ( THF) , C4H8O (MEK) , C3H6O ( acetone ) , C3H7NO ( DMF) , and C2H6OS ( DMSO ) .
[Claim 39] The method of claim 35 , wherei n the ferroelectric layer is formed by a spin coating, ink-jet printing, or screen printing method.
[Claim 40] The method of claim 35, wherein etching the ferroelectric layer is performed by a buffered oxide etching (BOE) method.
[Claim 41] The method of claim 35, wherein etching the ferroelectric layer is performed by a two-step etching method using BOE and gold etchant.
[Claim 42] The method of claim 35, wherein etching the ferroelectric layer is performed by a reactive ion etching (RIE) method.
[Claim 43] The method of claim 35, wherein the baking temperature is below 200°C.
[Claim 44]
A method of manufacturing a ferroelectric memory device including a substrate, a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, the method comprising: forming the gate electrode; forming the channel forming layer; forming the ferroelectric layer using a mixture of a solid solution of an inorganic ferroelectric material and an organic material; and forming the drain and source electrodes .
[Claim 45]
A ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gabe electrode and the ferroelectric layer.
[Claim 46]
The ferroelectric memory device of claim 45, wherein an insulating layer is formed between the memory cells, the insulating layer being formed of an organic material. [Claim 47]
The ferroelectric memory device of claim 45, wherein the ferroelectric layers of the stacked memory cells are arranged adjacent to each other.
[Claim 48]
The ferroelectric memory device of claim 45, wherein the gate electrodes of the stacked memory cells are arranged adjacent to each other.
[Claim 49]
A ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
[Claim 50] The ferroelectric memory device of claim 49, wherein an insulating layer is formed between the memory cells, the insulating layer being formed of an organic material.
[Claim 51] The ferroelectric memory device of claim 49, wherein the ferroelectric layers of the stacked memory cells are arranged adjacent to each other.
[Claim 52] The ferroelectric memory device of claim 49, wherein the gate electrodes of the stacked memory cells are arranged adjacent to each other.
[Claim 53] A ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer. [Claim 54]
The ferroelectric memory device of claim 53, wherein the ferroelectric layers of the stacked memory cells are arranged adjacent to each other.
[Claim 55]
The ferroelectric memory device of claim 53, wherein the gate electrodes of the stacked memory cells are arranged adjacent to each other.
[Claim 56]
A ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein the ferroelectric layer is formed of a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 57]
The ferroelectric memory device of claim 56, wherein an insulating layer is formed between the memory cells, the insulating layer being formed of an organic material.
[Claim 58]
The ferroelectric memory device of claim 56, wherein the ferroelectric layers of the stacked memory cells are arranged adjacent to each other.
[Claim 59]
The ferroelectric memory device of claim 56, wherein the gate electrodes of the stacked memory cells are arranged adjacent to each other.
[Claim 60]
A method of manufacturing a ferroelectric memory device, the method comprising: forming a first memory cell on a substrate; forming an insulating layer on the first memory cell; and forming a second memory cell on the insulating layer, wherein forming the first and second memory cells comprise forming a gate electrode, forming a channel forming layer, forming a ferroelectric layer using a mixture of an inorganic ferroelectric material and an organic material, and forming drain and source electrodes, respectively. [Claim βl]
The method of claim 60, wherein the ferroelectric layers of the first and second memory cells are arranged adjacent to each other.
[Claim 62]
The method of claim 60, wherein the gate layers of the first and second memory cells are arranged adjacent to each other.
[Claim 63]
The method of claim 60, wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
[Claim 64]
The method of claim 60, wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 65]
The method of claim 60, wherein, in forming the ferroelectric layer, a mixed solution of an inorganic ferroelectric solution and an organic solution is coated on the substrate to form a ferroelectric film, and the ferroelectric film is heated, baked and etched to form the ferroelectric layer.
[Claim 66] A method of manufacturing a ferroelectric memory- device, the method comprising: forming a first memory cell on a substrate; forming an insulating layer on the first memory cell; and forming a second memory cell on the insulating layer, wherein forming the first and second memory cells comprise forming a gate electrode, forming a channel forming layer, forming a ferroelectric layer using a mixture of a solid solution of an inorganic ferroelectric material and an organic material, and forming drain and source electrodes, respectively .
[Claim 67]
The method of claim 66, wherein the ferroelectric layers of the first and second memory cells are arranged adjacent to each other.
[Claim 68]
The method of claim 66, wherein the gate layers of the first and second memory cells are arranged adjacent to each other.
[Claim 69]
The method of claim 66, wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer.
[Claim 70]
The method of claim 66, wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
[Claim 71]
A ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein each of the ferroelectric layers of the stacked memory cells is formed of a mixture of an inorganic ferroelectric material and an organic material, the mixtures being different from each other, and wherein the channel forming layer is formed between the gate electrode and the ferroelectric layer. [Claim 72]
A ferroelectric memory device comprising a plurality of memory cells stacked on a substrate, wherein each of the plurality of memory cells comprises a gate electrode, drain and source electrodes, a channel forming layer, and a ferroelectric layer, wherein each of the ferroelectric layers of the stacked memory cells is formed of a mixture of an inorganic ferroelectric material and an organic material, the mixtures being different from each other, and wherein the ferroelectric layer is formed between the gate electrode and the channel forming layer.
PCT/KR2007/002884 2006-12-29 2007-06-14 Ferroelectric memory device, fet, and methods of manufacturing the same WO2008082046A1 (en)

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