Precursors and processes for making metal oxides

• US 5,559,260 A
• Filed: 06/07/1995
• Issued: 09/24/1996
• Est. Priority Date: 12/13/1991
• Status: Expired due to Term

• Current Assignee: Symetrix Corporation
• Original Assignee: Symetrix Corporation
• Inventors: Paz de Araujo, Carlos A., Scott, Michael C., McMillan, Larry D.
• Primary Examiner(s): NAZARIO GONZALEZ, PORFIRIO
• Application Number:
  US08/477,068
• Time in Patent Office: 475 Days
• Field of Search: 556/28, 556/31, 556/1, 534/16
• US Class Current: 556/28
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3243 Chromates or chromites, e.g. aluminum chromate, lanthanum strontium chromite
• CPC Class Codes: C04B 2235/3268 Manganates, manganites, rhenates or rhenites, e.g. lithium manganite, barium manganate, rhenium oxide
• CPC Class Codes: C04B 2235/441 Alkoxides, e.g. methoxide, tert-butoxide
• CPC Class Codes: C04B 2235/449 Organic acids, e.g. EDTA, citrate, acetate, oxalate
• CPC Class Codes: C04B 2235/72 Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
• CPC Class Codes: C04B 35/4682 based on BaTiO3 perovskite phase
• CPC Class Codes: C04B 35/6264 Mixing media, e.g. organic solvents
• CPC Class Codes: C07F 3/003 without C-Metal linkages
• CPC Class Codes: C07F 7/28 Titanium compounds
• CPC Class Codes: C23C 16/4412 Details relating to the exhausts, e.g. pumps, filters, scrubbers, particle traps
• CPC Class Codes: C23C 16/448 characterised by the method used for generating reactive gas streams, e.g. by evaporation or sublimation of precursor materials
• CPC Class Codes: C23C 16/4486 by producing an aerosol and subsequent evaporation of the droplets or particles
• CPC Class Codes: C23C 16/45561 Gas plumbing upstream of the reaction chamber
• CPC Class Codes: C23C 16/4558 Perforated rings
• CPC Class Codes: C23C 16/46 characterised by the method used for heating the substrate C23C16/48, C23C16/50 take precedence
• CPC Class Codes: C23C 16/482 using incoherent light, UV to IR, e.g. lamps
• CPC Class Codes: C23C 16/52 : Controlling or regulating the coating process C23C16/45557, C23C16/279 take precedence
• CPC Class Codes: C23C 18/1216 : Metal oxides C23C18/1212 takes precedence
• CPC Class Codes: C23C 18/1275 : performed under inert atmosphere
• CPC Class Codes: C30B 29/68 : Crystals with laminate structure, e.g. "superlattices"
• CPC Class Codes: C30B 7/00 : Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions from molten solvents C30B9/00; by normal or gradient freezing C30B11/00; under a protective fluid C30B27/00
• CPC Class Codes: H01C 7/1013 : Thin film varistors
• CPC Class Codes: H01L 21/02197 : the material having a perovskite structure, e.g. BaTiO3
• CPC Class Codes: H01L 21/02205 : the layer being characterised by the precursor material for deposition
• CPC Class Codes: H01L 21/02282 : liquid deposition, e.g. spin-coating, sol-gel techniques, spray coating
• CPC Class Codes: H01L 21/02337 : treatment by exposure to a gas or vapour
• CPC Class Codes: H01L 21/314 : Inorganic layers H01L21/3105, H01L21/32 take precedence
• CPC Class Codes: H01L 21/31691 : with perovskite structure
• CPC Class Codes: H01L 28/55 : with a dielectric comprising a perovskite structure material
• CPC Class Codes: H01L 28/56 : the dielectric comprising two or more layers, e.g. comprising buffer layers, seed layers, gradient layers
• CPC Class Codes: H01L 28/60 : Electrodes
• CPC Class Codes: H10B 12/30 : DRAM devices comprising one-transistor - one-capacitor [1T-1C] memory cells
• CPC Class Codes: H10B 53/00 : Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory capacitors

Abstract

A precursor is made by mixing a metal alkoxycarboxylate-containing liquid with a 2-ethylhexanoic acid in an effective amount for shelf-stabilizing said liquid by substituting 2-ethylhexanoate ligands for alkoxide ligands, thereby forming a mixture, and heating said mixture to substitute said carboxylate ligands for said alkoxide ligands. Specficially, a barium strontium titanate precursor and a strontium bismuth tantalate precursor are made by combining polyoxyalkylated metal moieties to form a liquid solution in which the metal atoms bond with an oxygen atom in a ligand selected from a ligand group consisting of alkoxides and carboxylates, then then heating the liquid solution.

Claims

1. A method of making a precursor for fabricating a metal oxide, said method comprising the steps of:

mixing a metal alkoxycarboxylate-containing liquid with a 2-ethylhexanoic acid in an effective amount for shelf-stabilizing said liquid by substituting 2-ethylhexanoate ligands for alkoxide ligands, thereby forming a mixture; and

heating said mixture to so substitute said carboxylate ligands for said alkoxide ligands.

2. The method as set forth in claim 1, further including a step of providing said metal alkoxycarboxylate to at least two metals selected from a metal group consisting of barium, strontium, tantalum, calcium, bismuth, lead, yttrium, scandium, lanthanum, antimony, chromium, thallium, titanium, hafnium, tungsten, niobium, zirconlure, manganese, iron, cobalt, nickel, magnesium, zinc, and mixtures thereof.

3. The method as set forth in claim 2, said metals being provided in effective amounts for forming strontium bismuth tantalate upon drying and calcining of said precursor.

4. The method as set forth in claim 2, said metals being provided in effective amounts for forming strontium bismuth niobate upon drying and calcining of said precursor.

5. The method as set forth in claim 2, said metals being provided in effective amounts for forming strontium bismuth tantalum niobate upon drying and calcining of said precursor.

6. The method as set forth in claim 2, said metals being provided in effective amounts for forming barium bismuth tantalate upon drying and calcining of said precursor.

7. The method as set forth in claim 2, said metals being provided in effective amounts for forming lead bismuth tantalate upon drying and calcining of said precursor.

8. The method as set forth in claim 2, said metals being provided in effective amounts for forming barium bismuth niobate upon drying and calcining of said precursor.

9. A precursor produced according to the method of claim 1, said precursor having a shelf life exceeding at least two months.

10. A method of making a barium strontium titanate precursor, said method comprising the steps of:

combining a polyoxyalkylated barium moiety, a polyoxyalkylate strontium moiety, and a polyoxyalkylated titanium moiety to form a liquid solution,

each of said respective moieties having a formula in which corresponding barium, strontium, and titanium atoms bond with an oxygen atom in a ligand selected from a ligand group consisting of alkoxides and carboxylates; and

heating said liquid solution.

11. The method as set forth in claim 10, wherein said formula defines a member selected from a moiety group consisting of barium carboxylates, barium alkoxides, barium alkoxycarboxylates, strontium carboxylates, strontium alkoxides, strontium alkoxycarboxylates, titanium carboxylates, titanium alkoxides, and titanium alkoxycarboxylates.

12. The method as set forth in claim 11, wherein said heating step includes reacting two members of said moiety group to form a reaction product having a molecular formula including a central oxygen atom connecting two metal atoms, said two members including a single-metal alkoxycarboxylate and a metal alkoxide.

13. The method as set forth in claim 12, said two members including said barium alkoxycarboxylate and said titanium alkoxide.

14. The method as set forth in claim 13, said titanium alkoxide being titanium isopropoxide.

15. A method of making a strontium bismuth tantalate precursor, said method comprising the steps of:

combining a polyoxyalkylated strontium moiety, a polyoxyalkylated bismuth moiety, and a polyoxyalkylated tantalum moiety to form a liquid solution;

each of said respective moieties having a formula in which corresponding strontium, bismuth, and tantalum atoms bond with an oxygen atom in a ligand selected from a ligand group consisting of alkoxides and carboxylates; and

heating said liquid solution.

16. The method as set forth in claim 15, wherein said formula defines a member selected from a moiety group consisting of bismuth carboxylates, bismuth alkoxides, bismuth alkoxycarboxylates, strontium carboxylates, strontium alkoxides, strontium alkoxycarboxylates, tantalum carboxylates, tantalum alkoxides, and tantalum alkoxycarboxylates.

17. The method as set forth in claim 16, wherein said heating step includes reacting two members of said moiety group to form a reaction product having a molecular formula including a central oxygen atom connecting two metal atoms, said two members including a single-metal alkoxycarboxylate and a metal alkoxide.