US6198119B1
Expired / Lapsed
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Ferroelectric element and method of producing the same
Assignee: Hitachi Ltd
•
Filing: 1997-03-11
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Granted: 2001-03-06
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Expires: 2017-03-11
Abstract
Abstract A ferroelectric element is provided that can be highly densely integrated having a high Pr and a small Ec by using a ferroelectric thin film of the perovskite structure. A large distortion is imparted to the crystalline lattices of a ferroelectric thin film of the perovskite structure by using in combination elements having dissimilar ionic radii for the A-site that constitutes crystalline lattices, for the B-site and for the C-site that produces polarization, in order to obtain a ferroelectric element of a structure in which the ferroelectric thin film exhibiting a high spontaneous polarization and a small coersive electric field is sandwiched by the electrodes.
Inventors
- 👤 Toshihide Nabatame
- 👤 Takaaki Suzuki
- 👤 Tomoji Oishi
- 👤 Ken Takahashi
- 👤 Kunihiro Maeda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:14
CPC Classifications
H; H10; H10D; H10D1/00; H10D1/60; H10D1/68; H10D1/682; H10P; H10P14/00; H10P14/60; H10P14/63; H10P14/6326; H10P14/6328; H10P14/6329; H10P14/69; H10P14/692; H10P14/6938; H10P14/69398
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
73 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a crystalline structure which is comprised of a plurality of unit cells of a perovskite structure superposed one upon another in the C-axis direction, said crystalline structure comprising a blocking layer and first and second layers to cause polarization, said blocking layer being between said first and second layers to cause polarization.
Claim 2
Dependent Claim
73 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a crystalline structure which is comprised of a plurality of unit cells of a perovskite structure superposed one upon another in the C-axis direction, said crystalline structure comprising a blocking layer and first and second layers to cause polarization, said blocking layer being between said first and second layers to cause polarization.
Claim 3
Dependent Claim
96 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (AO) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 42) A=at least one of Tl, Hg, Ce, Y, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, La, and Sm B=at least one of Bi, Pb, Ca, Sr, and Ba, C=at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, and y=2, 3, 4, or 5.
Claim 4
Dependent Claim
96 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (AO) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 42) A=at least one of Tl, Hg, Ce, Y, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, La, and Sm B=at least one of Bi, Pb, Ca, Sr, and Ba, C=at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, and y=2, 3, 4, or 5.
Claim 5
Dependent Claim
71 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (PbO) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 3) B=at least one of Ca, Sr, and Ba, C=at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, and y=2, 3, 4, or 5.
Claim 6
Dependent Claim
71 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (PbO) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 3) B=at least one of Ca, Sr, and Ba, C=at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, and y=2, 3, 4, or 5.
Claim 7
Dependent Claim
28 words
A ferroelectric element according to any one of claims 1 to 3 , wherein said ferroelectric thin film is (100)-oriented or (010)-oriented with respect to the lower electrode.
Claim 8
Dependent Claim
26 words
A ferroelectric element according to any one of claims 1 to 3 , wherein said ferroelectric thin film is (110)-oriented with respect to the lower electrode.
Claim 9
Dependent Claim
26 words
A ferroelectric element according to any one of claims 1 to 3 , wherein said ferroelectric thin film is (001)-oriented with respect to the lower electrode.
Claim 10
Dependent Claim
35 words
A ferroelectric element according to any one of claims 1 to 3 , wherein said ferroelectric thin film is so oriented that the c-axis thereof is tilted at 45° with respect to the lower electrode.
Claim 11
Dependent Claim
28 words
A ferroelectric element according to claim 4 , wherein the ratio of the ferroelectric thin film (100)-oriented or (010)-oriented to the lower electrode is not smaller than 70%.
Claim 12
Dependent Claim
26 words
A ferroelectric element according to claim 5 , wherein the ratio of the ferroelectric thin film (110)-oriented to the lower electrode is not smaller than 80%.
Claim 13
Dependent Claim
26 words
A ferroelectric element according to claim 6 , wherein the ratio of the ferroelectric thin film (001)-oriented to the lower electrode is not smaller than 70%.
Claim 14
Dependent Claim
39 words
A ferroelectric element according to claim 7 , wherein the ratio of the ferroelectric thin film which is so oriented that the c-axis thereof is tilted at 45° with respect to the lower electrode is not smaller than 90%.
Claim 15
Dependent Claim
84 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a crystalline structure which is comprised of a plurality of unit cells of a perovskite structure superposed one upon another in the c-axis direction, said crystalline structure including two blocking layers and first and second layers to cause polarization, said two blocking layers being between the first and second layers to cause polarization, said two blocking layers including Bi, O and another element.
Claim 16
Dependent Claim
84 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a crystalline structure which is comprised of a plurality of unit cells of a perovskite structure superposed one upon another in the c-axis direction, said crystalline structure including two blocking layers and first and second layers to cause polarization, said two blocking layers being between the first and second layers to cause polarization, said two blocking layers including Bi, O and another element.
Claim 17
Dependent Claim
94 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (Bi 2−x A x O 2 ) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 44) A=at least one of Tl, Hg, Sb, and As, B=at least one of Bi, Pb, Ca, Sr, Ba, Y, and rare earth elements, C=at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, 0<x<2, and y=1, 2, 3, 4, or 5.
Claim 18
Dependent Claim
94 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (Bi 2−x A x O 2 ) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 44) A=at least one of Tl, Hg, Sb, and As, B=at least one of Bi, Pb, Ca, Sr, Ba, Y, and rare earth elements, C=at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, 0<x<2, and y=1, 2, 3, 4, or 5.
Claim 19
Dependent Claim
86 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (Bi 2−x Pb x O 2 ) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 45) B=at least one of Bi, Pb, Ca, Sr, Ba, Y, and rare earth elements, C at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, 0<x<2, and y=1, 2, 3, 4, or 5.
Claim 20
Dependent Claim
86 words
A ferroelectric element having an upper electrode, a ferroelectric thin film and a lower electrode, wherein said ferroelectric thin film has a perovskite structure and has a composition represented by: (Bi 2−x Pb x O 2 ) 2+ (B y−1 C y O 3y+1 ) 2− (Chemical formula 45) B=at least one of Bi, Pb, Ca, Sr, Ba, Y, and rare earth elements, C at least one of Ti, Nb, Ta, W, Mo, Fe, Co, Cr, and Zr, 0<x<2, and y=1, 2, 3, 4, or 5.
Claim 21
Dependent Claim
27 words
A ferroelectric element according to claim 12 , 13 or 14 , wherein said ferroelectric thin film is (100)-oriented or (010)-oriented with respect to the lower electrode.
Claim 22
Dependent Claim
25 words
A ferroelectric element according to claim 12 , 13 or 14 , wherein said ferroelectric thin film is (110)-oriented with respect to the lower electrode.
Claim 23
Dependent Claim
34 words
A ferroelectric element according to claim 12 , 13 or 14 , wherein said ferroelectric thin film is so oriented that the c-axis thereof is tilted at 45° with respect to the lower electrode.
Claim 24
Dependent Claim
29 words
A ferroelectric thin film according to claim 15 , wherein the ratio of the ferroelectric thin film (100)-oriented or (010)-oriented to the lower electrode is not smaller than 70%.
Claim 25
Dependent Claim
26 words
A ferroelectric element according to claim 16 , wherein the ratio of the ferroelectric thin film (110)-oriented to the lower electrode is not smaller than 80%.
Claim 26
Dependent Claim
39 words
A ferroelectric element according to claim 17 , wherein the ratio of the ferroelectric thin film which is so oriented that the c-axis thereof is tilted at 45° with respect to the lower electrode is not smaller than 90%.
Claim 27
Dependent Claim
51 words
A ferroelectric element according to any one of claims 1 to 3 , wherein the ferroelectric element has a planar structure with electrodes on both sides of the ferroelectric thin film which is of the perovskite structure, and the width of the ferroelectric thin film is not larger than 0.3 μm.
Claim 28
Dependent Claim
46 words
A ferroelectric element of a composition according to claim 12 or 13 , a planar-type structure with electrodes on both sides of the ferroelectric thin film which is of the perovskite structure, and the width of the ferroelectric thin film is not larger than 0.3 μm.
Claim 29
Dependent Claim
63 words
A lower electrode according to any one of claim 1 , 2 , 3 , 12 or 13 , wherein the ferroelectric element is constituted by a metal, an electrically conductive oxide of a single element and an electrically conductive oxide of a perovskite structure from the side of a lower substrate, and said electrically conductive oxides are oriented in a particular plane.
Claim 30
Dependent Claim
71 words
A ferroelectric element according to any one of claim 1 , 2 , 3 , 12 or 13 , wherein the upper electrode is constituted by an electrically conductive oxide of a perovskite structure, a metal or an electrically conductive oxide of the perovskite structure, an electrically conductive oxide of a single element and a metal in the order from the layer which is in contact with the ferroelectric thin film.
Claim 31
Dependent Claim
42 words
A ferroelectric element according to claim 21 , wherein a layer of an electrode in contact with the ferroelectric thin film is necessarily constituted by an electrically conductive oxide of a single element or an electrically conductive oxide of a perovskite structure.
Claim 32
Dependent Claim
27 words
A ferroelectric element according to claim 24 , wherein the metal is at least one element selected from Pt, Au, Al, Ni, Cr, Ti, Mo, and W.
Claim 33
Dependent Claim
48 words
An electrically conductive oxide according to claim 23 , wherein the electrically conductive oxide of a single element is at least one oxide of Ti, V, Eu, Cr, Mo, W, Ph, Os, Ir, Pt, Re, Ru and Sn, and has a resistivity of not larger than 1 mΩ□cm.
Claim 34
Dependent Claim
83 words
An electrically conductive oxide according to claim 23 , wherein the electrically conductive oxide of the perovskite structure is a perovskite containing at least one of ReO 3 , SrReO 3 , BaReO 3 , LaTiO 3 , SrVO 3 , CaCrO 3 , SrCrO 3 , SrFeO 3 , La 1−x Sr x CoO 3 (O<x<0.5), LaNiO 3 , CaRUO 3 , SrRuO 3 , SrTiO 3 , and BaPbO 3 , and has a resistivity of not larger than 1 mΩ□cm.
Claim 35
Dependent Claim
31 words
A ferroelectric element according to any one of claim 1 , 2 , 3 , 12 or 13 , wherein the upper electrode is constituted by a transparent electrically conductive oxide.
Claim 36
Dependent Claim
23 words
A ferroelectric element according to claim 20 , wherein at least one of the electrodes is constituted by a transparent electrically conductive oxide.
Claim 37
Dependent Claim
60 words
A ferroelectric element according to claim 30 , wherein the transparent electrically conductive oxide contains at least one of In 2 O 3 , Sn 2 , ZnO, ITO (In—Sn—O), ATO (Sb-doped Sn), FTO (F-doped Sn) CTO (Cd—Sn—O), has a resistivity of not larger than 1 m□cm, and a transmission factor in a visible region of not smaller than 80%.
Claim 38
Dependent Claim
36 words
A ferroelectric memory cell in which the ferroelectric element of any one of claim 1 , 2 , 3 , 12 , 13 or 14 is formed on the gate of a semiconductor field effect transistor.
Claim 39
Dependent Claim
35 words
A ferroelectric memory cell in which the ferroelectric element of any one of claim 1 , 2 , 3 , 12 , 13 or 14 is formed as a capacitor of a semiconductor MOS portion.
Claim 40
Dependent Claim
22 words
A ferroelectric memory cell in which the ferroelectric element of claim 20 is formed as a capacitor of a semiconductor MOS portion.
Claim 41
Dependent Claim
31 words
An infrared ray sensor, wherein the ferroelectric element according to any one of claim 1 , 2 , 3 , 12 , 13 or 14 is a pyroelectric infrared ray sensor.
Claim 42
Dependent Claim
13 words
An optical response system comprising a ferroelectric element according to claim 30 .
Claim 43
Dependent Claim
20 words
A memory including the ferroelectric memory cell according to claim 32 as a non-contact type read memory or write memory.
Claim 44
Dependent Claim
42 words
A ferroelectric element according to claim 22 , wherein a layer of an electrode in contact with the ferroelectric thin film is necessarily constituted by an electrically conductive oxide of a single element or an electrically conductive oxide of a perovskite structure.
Claim 45
Dependent Claim
27 words
A metal according to claim 23 , wherein the ferroelectric element is at least one element selected from Pt, Au, Al, Ni, Cr, Ti, Mo, and W.
Claim 46
Dependent Claim
47 words
A ferroelectric element according to claim 25 , wherein the electrically conductive oxide of a single element is at least one oxide of Ti, V, Eu, Cr, Mo, W, Ph, Os, Ir, Pt, Re, Ru and Sn, and has a resistivity of not larger than 1 mΩ□cm.
Claim 47
Dependent Claim
47 words
A ferroelectric element according to claim 24 , wherein the electrically conductive oxide of a single element is at least one oxide of Ti, V, Eu, Cr, Mo, W, Ph, Os, Ir, Pt, Re, Ru and Sn, and has a resistivity of not larger than 1 mΩ□cm.
Claim 48
Dependent Claim
80 words
A ferroelectric element according to claim 25 , wherein the electrically conductive oxide of the perovskite structure is a perovskite containing at least ReO 3 , SrReO 3 , BaReO 3 , LaTiO 3 , SrVO 3 , CaCrO 3 , SrCrO 3 , SrFeO 3 , La 1−x Sr x CoO 3 (O<x<0.5), LaNiO 3 , CaRuO 3 , SrRuO 3 , SrTiO 3 , and BaPbO 3 , and has a resistivity of not larger than 1 mΩ□cm.
Claim 49
Dependent Claim
80 words
A ferroelectric element according to claim 24 , wherein the electrically conductive oxide of the perovskite structure is a perovskite containing at least ReO 3 , SrReO 3 , BaReO 3 , LaTiO 3 , SrVO 3 , CaCrO 3 , SrCrO 3 , SrFeO 3 , La 1−x Sr x CoO 3 (O<x<0.5), LaNiO 3 , CaRuO 3 , SrRuO 3 , SrTiO 3 , and BaPbO 3 , and has a resistivity of not larger than 1 mΩ□cm.
Claim 50
Dependent Claim
23 words
A ferroelectric element according to claim 21 , wherein at least one of the electrodes is constituted by a transparent electrically conductive oxide.
Claim 51
Dependent Claim
60 words
A ferroelectric element according to claim 29 , wherein the transparent electrically conductive oxide containing at least one of In 2 O 3 , Sn 2 , ITO (In—Sn—O), ATO (Sb-doped Sn), FTO (F-doped Sn) or CTO (Cd—Sn—O), has a resistivity of not larger than 1 m□cm, and a transmission factor in a visible region of not smaller than 80%.
Claim 52
Dependent Claim
13 words
An optical response system comprising a ferroelectric element according to claim 29 .
Claim 53
Dependent Claim
20 words
A memory including the ferroelectric memory cell according to claim 33 as a non-contact type read memory or write memory.
Claim 54
Dependent Claim
31 words
A ferroelectric element according to claim 1 , wherein the crystalline structure consists of said plurality of unit cells of a perovskite structure superposed one upon another in the c-axis direction.
Claim 55
Dependent Claim
31 words
A ferroelectric element according to claim 12 , wherein the crystalline structure consists of said plurality of unit cells of a perovskite structure superposed one upon another in the c-axis direction.
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