US6236076B1
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Ferroelectric field effect transistors for nonvolatile memory applications having functional gradient material
Assignee: Panasonic Holdings Corp
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Filing: 1999-04-29
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Granted: 2001-05-22
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Expires: 2019-04-29
Abstract
Abstract A nonvolatile nondestructible read-out ferroelectric FET memory comprising a semiconductor substrate, a ferroelectric functional gradient material ("FGM") thin film, and a gate electrode. In one basic embodiment, the ferroelectric FGM thin film contains a ferroelectric compound and a dielectric compound. The dielectric compound has a lower dielectric constant than the ferroelectric compound. There is a concentration gradient of the ferroelectric compound in the thin film. In a second basic embodiment, the FGM thin film is a functional gradient ferroelectric ("FGF"), in which compositional gradients of ferroelectric compounds result in unconventional hysteresis behavior. The unconventional hysteresis behavior of FGF thin films is elated to an enlarged memory window in ferroelectric FET memories. FGM thin films are preferably formed using a liquid source MOD methods, preferably a multisource CVD method.
Inventors
- 👤 Koji Arita
- 👤 Carlos A. Paz de Araujo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 02:57
CPC Classifications
H; H10; H10D; H10D84/00; H10D84/80; H10D64/00; H10D64/60; H10D64/66; H10D64/68; H10D64/689; H10D30/00; H10D30/60; H10D30/701; H10D64/01; H10D64/031; H10D64/033; H10D1/00; H10D1/60; H10D1/68; H10D1/682; H10D1/684; H10D30/68
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
35 words
A ferroelectric memory including a ferroelectric FET comprising: a semiconductor substrate; a ferroelectric functionally graded material (FGM) thin film less than a micron in thickness and comprising a layered superlattice material; and a gate electrode.
Claim 2
Dependent Claim
35 words
A ferroelectric memory including a ferroelectric FET comprising: a semiconductor substrate; a ferroelectric functionally graded material (FGM) thin film less than a micron in thickness and comprising a layered superlattice material; and a gate electrode.
Claim 3
Dependent Claim
36 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , wherein said ferroelectric FGM thin film is located above said semiconductor substrate, and said gate electrode is located above said ferroelectric FGM thin film.
Claim 4
Dependent Claim
24 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , wherein said gate electrode is located on said ferroelectric FGM thin film.
Claim 5
Dependent Claim
24 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , wherein said ferroelectric FGM thin film is located on said semiconductor substrate.
Claim 6
Dependent Claim
23 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , further comprising a gate oxide layer located on said semiconductor substrate.
Claim 7
Dependent Claim
25 words
A ferroelectric memory including a ferroelectric FET as in claim 5 , wherein said ferroelectric FGM thin film is located on said gate oxide layer.
Claim 8
Dependent Claim
24 words
A ferroelectric memory including a ferroelectric FET as in claim 5 , further comprising an interface insulator layer located on said gate oxide layer.
Claim 9
Dependent Claim
29 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , further comprising an interface insulator layer located between said ferroelectric FGM thin film and said semiconductor substrate.
Claim 10
Dependent Claim
23 words
A ferroelectric memory including a ferroelectric FET as in claim 8 , wherein said interface insulator layer is located on said semiconductor substrate.
Claim 11
Dependent Claim
25 words
A ferroelectric memory including a ferroelectric FET as in claim 9 , wherein said ferroelectric FGM thin film is located on said interface insulator layer.
Claim 12
Dependent Claim
28 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , further comprising a floating electrode located between said semiconductor substrate and said ferroelectric FGM thin film.
Claim 13
Dependent Claim
26 words
A ferroelectric memory including a ferroelectric FET as in claim 11 , further comprising an adhesion layer located between said floating electrode and said semiconductor substrate.
Claim 14
Dependent Claim
34 words
A ferroelectric memory including a ferroelectric FET as in claim 12 , wherein said floating electrode is located on said adhesion layer, and said ferroelectric FGM thin film is located on said floating electrode.
Claim 15
Dependent Claim
91 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , wherein said ferroelectric FGM thin film contains moieties of first metal atoms in relative molar proportions corresponding to a stoichiometric formula of said layered superlattice material and moieties of second metal atoms in relative molar proportions corresponding to a stoichiometric formula of a dielectric compound, said dielectric compound having a dielectric constant less than said layered superlattice material, and said ferroelectric FGM thin film having a functional gradient of said moieties of first metal atoms and second metal atoms.
Claim 16
Dependent Claim
45 words
A ferroelectric memory including a ferroelectric FET as in claim 14 , wherein said dielectric compound comprises an oxide selected from the group consisting of ZrO 2 , CeO 2 , Y 2 O 3 and Ce 1−x Zr x O 2 , where 0≦x≦1.
Claim 17
Dependent Claim
50 words
A ferroelectric memory including a ferroelectric FET as in claim 14 , wherein said ferroelectric FGM thin film comprises at least two metals selected from the group consisting of strontium, calcium, barium, cadmium, lead, tantalum, hafnium, tungsten, niobium, zirconium, bismuth, scandium, yttrium, lanthanum, antimony, chromium, molybdenum, vanadium, ruthenium and thallium.
Claim 18
Dependent Claim
25 words
A ferroelectric memory including a ferroelectric FET as in claim 16 , wherein said first metal atoms include the metals strontium, bismuth, tantalum, and niobium.
Claim 19
Dependent Claim
48 words
A ferroelectric memory including a ferroelectric FET as in claim 17 , wherein said first metal atoms include the metals strontium, bismuth and tantalum in relative molar proportions corresponding to a stoichiometric formula SrBi 2+y (Ta 1−x Nb x ) 2 O 9 , wherein 0≦x≦1 and 0≦y≦0.20.
Claim 20
Dependent Claim
72 words
A ferroelectric memory including a ferroelectric FET as in claim 1 , wherein said ferroelectric FGM thin film is a functionally graded ferroelectric (FGF) thin film, said FGF thin film containing moieties of a plurality of types of metal atoms in relative molar proportions corresponding to stoichiometric formulas of said layered superlattice material and a second ferroelectric compound, said FGM thin film having a functional gradient of said moieties of metal atoms.
Claim 21
Dependent Claim
22 words
A ferroelectric memory including a ferroelectric FET as in claim 19 , wherein said second ferroelectric compound is a ferroelectric metal oxide.
Claim 22
Dependent Claim
23 words
A ferroelectric memory including a ferroelectric FET as in claim 20 , wherein said ferroelectric metal oxide is an ABO 3 -type perovskite.
Claim 23
Dependent Claim
54 words
A ferroelectric memory including a ferroelectric FET as in claim 21 , wherein said types of metal atoms include lead, zirconium and tantalum, and said stoichiometric formulas include a formula represented by a generalized stoichiometric formula Pb(Zr 1−x Ti x )O 3 , wherein x varies in correspondence with said functional gradient and 0≦x≦1.
Claim 24
Dependent Claim
14 words
A ferroelectric memory including a ferroelectric FET as in claim 22 , wherein 0.25≦x≦0.45.
Claim 25
Dependent Claim
22 words
A ferroelectric memory including a ferroelectric FET as in claim 20 , wherein said second ferroelectric compound is a layered superlattice material.
Claim 26
Dependent Claim
49 words
A ferroelectric memory including a ferroelectric FET as in claim 24 , wherein said FGF thin film comprises at least two metals selected from the group consisting of strontium, calcium, barium, cadmium, lead, tantalum, hafnium, tungsten, niobium, zirconium, bismuth, scandium, yttrium, lanthanum, antimony, chromium, molybdenum, vanadium, ruthenium and thallium.
Claim 27
Dependent Claim
24 words
A ferroelectric memory including a ferroelectric FET as in claim 25 , wherein said types of metal atoms include strontium, bismuth, tantalum and niobium.
Claim 28
Dependent Claim
45 words
A ferroelectric memory including a ferroelectric FET as in claim 26 , wherein said stoichiometric formulas are represented by a generalized stoichiometric formula SrBi 2 (Ta 1−x Nb x ) 2 O 9 , wherein x varies in correspondence with said functional gradient and 0≦x≦1.
Claim 29
Dependent Claim
33 words
A ferroelectric memory including a ferroelectric FET comprising: a semiconductor substrate; a ferroelectric thin film; and a gate electrode; wherein said ferroelectric thin film comprises ferroelectric layered superlattice material having unconventional hysteresis behavior.
Claim 30
Dependent Claim
33 words
A ferroelectric memory including a ferroelectric FET comprising: a semiconductor substrate; a ferroelectric thin film; and a gate electrode; wherein said ferroelectric thin film comprises ferroelectric layered superlattice material having unconventional hysteresis behavior.
Claim 31
Dependent Claim
49 words
A ferroelectric memory including a ferroelectric FET as in claim 28 , wherein said layered superlattice material comprises the metals strontium, bismuth, tantalum and niobium in relative molar proportions corresponding to a stoichiometric formula SrBi 2+y (Ta 1−x Nb x ) 2 O 9 , wherein 0≦x≦1 and 0≦y≦0.20.
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