Precursors and processes for making metal oxides

• US 5,654,456 A
• Filed: 06/07/1995
• Issued: 08/05/1997
• 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:
  US08/482,766
• Time in Patent Office: 790 Days
• Field of Search: 556/1, 556/28, 556/54, 556/55, 501/138
• 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: 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 21/314 : 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 first metal, an alcohol, and a carboxylic acid are reacted to form a metal alkoxycarboxylate which is then reacted with an alkoxide and/or a carboxylate of a second metal to form a precursor. Alternatively, a metal carboxylate and a metal alkoxide are combined and heated to form a precursor. In either alternative, the precursor includes all or most of the metal-oxygen-metal bonds of a desired metal oxide and a carboxylate ligand. The precursor is applied to a substrate, dried and annealed to form the metal oxide, such as BST. The metal-oxygen-metal bonds in the precursor permit the desired metal oxide to be formed from the precursor in one step, providing excellent thin films suitable for integrated circuits. The carboxylate ligand provides stability to the precursor allowing it to be stored for periods common in large scale manufacturing.

Claims

1. A method of making a barium strontium titanate precursor comprising:

providing a barium alkoxycarboxylate initial precursor; and

adding strontium and titanium to said barium alkoxycarboxylate to form a final precursor.

2. A method as in claim 1 wherein said step of adding titanium comprises:

reacting strontium with said initial precursor to form a barium/strontium precursor solution; and

combining titanium isopropoxide with barium/strontium precursor solution; and

heating said combined solution.

3. A method of making a barium strontium titanate precursor comprising:

providing a titanium isopropoxide initial precursor; and

adding said titanium isopropoxide to another initial precursor containing carboxylates to form a final precursor.

4. A method as in claim 3 wherein said step of adding comprises combining said titanium isopropoxide with a barium/strontium alkoxycarboxylate solution and heating the combined solutions.