US5116643A
Expired / Lapsed
US
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Method for preparing PLZT, PZT and PLT sol-gels and fabricating ferroelectric thin films
Assignee: National Semiconductor Corp
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Filing: 1990-12-19
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Granted: 1992-05-26
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Expires: 2010-12-19
Abstract
Abstract A method to produce thin films suitable for fabricating ferroelectric thin films. The method provides for selection of the predetermined amounts of lead, lanthanum, zirconium, and titanium precursors which are soluble in different solvents. Dissolving predetermined amounts of the precursors in their respective solvents in proportions such that hydrolyze reaction rate for each metal precursor will be approximately equal. Preferably, the reaction is performed under an inert atmosphere at from about 350 mmHg to 650 mmHg pressure. The precursors and solvents are mixed, and water is added to begin a hydrolysis reaction. After the hydrolysis the solution is heated to drive off the excess water and solvent to promote the formation of a sol-gel. The sol-gel is then applied to a thin substrate and sintered to produce the ferroelectric film.
Inventors
- 👤 William D. Miller
- 👤 Leo N. Chapin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 01:23
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/60; H10P14/69; H10P14/692; H10P14/6938; H10P14/69398; C; C04; C04B; C04B35/00; C04B35/01; C04B35/48; C04B35/49; C04B35/491; C23; C23C; C23C18/00; C23C18/02; C23C18/12; C23C18/1204; C23C18/1208; C23C18/1216; C23C18/1229; C23C18/1245; C23C18/125; C23C18/1254; H10P14/65; H10P14/6516; H10P14/6529; H10P14/66; H10P14/668; H10P14/63; H10P14/6326; H10P14/6342
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
150 words
A method of preparing a mixture suitable for spin deposition on substrates, comprising: (a) solubilizing amounts of two or more precursors of lead, titanium, zirconium and lanthanum in predetermined solvents, said solvents being different for each precursor at proportions such that upon hydrolysis the metal precursors will exhibit approximately equal reaction rates; (b) mixing under an inert atmosphere at a pressure from about 350 mmHg to about 650 mmHg the metal precursors and solvents at a temperature sufficient to maintain the metal precursors in solution and for a period of time sufficient to produce a homogeneous mixture; (c) adding a predetermined amount of water to resulting solution sufficient to begin a hydrolysis reaction without causing precipitation of solids while maintaining the mixture under an insert atmosphere; and (d) boiling the mixture at a temperature sufficient to vaporize said solvents and azeotrope water to increase a viscosity suitable for spin coating.
Claim 2
Independent Claim
150 words
A method of preparing a mixture suitable for spin deposition on substrates, comprising: (a) solubilizing amounts of two or more precursors of lead, titanium, zirconium and lanthanum in predetermined solvents, said solvents being different for each precursor at proportions such that upon hydrolysis the metal precursors will exhibit approximately equal reaction rates; (b) mixing under an inert atmosphere at a pressure from about 350 mmHg to about 650 mmHg the metal precursors and solvents at a temperature sufficient to maintain the metal precursors in solution and for a period of time sufficient to produce a homogeneous mixture; (c) adding a predetermined amount of water to resulting solution sufficient to begin a hydrolysis reaction without causing precipitation of solids while maintaining the mixture under an insert atmosphere; and (d) boiling the mixture at a temperature sufficient to vaporize said solvents and azeotrope water to increase a viscosity suitable for spin coating.
Claim 3
Dependent Claim
33 words
The method of claim 1 comprising the additional step of diluting the mixture resulting from step (c) with additional amounts of solvents in order to quench the hydrolysis reaction followed by step (d).
Claim 4
Dependent Claim
36 words
The method of claim 1 wherein said precursors are selected from the group comprising alkoxides of lanthanum, alkioxides of lead, alkoxides of titanium, alkoxides of zirconium, esters of lead, esters of titanium, and esters of zirconium.
Claim 5
Dependent Claim
37 words
The method of claim 2 wherein said metal precursors are selected from the group comprising alkoxides of lanthanum, alkoxides of lead, alkoxides of titanium, alkoxides of zirconium, esters of lead, esters of titanium, and esters of zirconium.
Claim 6
Dependent Claim
24 words
The method of claim 1 wherein said precursors are selected from the group comprising lanthanum 2,4-pentanedionate, zirconium n-butoxide, titanium (IV) isopropoxide, and lead tetraacetate.
Claim 7
Dependent Claim
24 words
The method of claim 2 wherein said precursors are selected from the group comprising lanthanum 2,4-pentanedionate, zirconium n-butoxide, titanium (IV) isopropoxide, and lead tetraacetate.
Claim 8
Dependent Claim
53 words
The method of claim 1 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the applied thin film.
Claim 9
Dependent Claim
53 words
The method of claim 2 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the applied thin film.
Claim 10
Dependent Claim
53 words
The method of claim 3 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 500° C. to about 650° C. for a period sufficient to sinter the applied thin film.
Claim 11
Dependent Claim
53 words
The method of claim 4 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 500° C. to about 650° C. for a period sufficient to sinter the applied thin film.
Claim 12
Dependent Claim
54 words
The method of claim 5 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 500° C. to about 650° C. for a period of sufficient to sinter the applied thin film.
Claim 13
Independent Claim
201 words
A method of preparing a PLZT mixture suitable for spin deposition on substrates, comprising: (a) solubilizing a lead precursor in a first solvent; (b) solubilizing a titanium precursor in a second solvent; (c) solubilizing a zirconium precursor in a third solvent; (d) mixing under an inert atmosphere at a pressure of from about 350 mmHg to about 650 mmHg the dissolved lead, titanium and zirconium precursor in the first, second and third solvents together at a temperature sufficient to maintain the metals in solution and for a period of time sufficient to produce a homogeneous mixture; (e) adjusting the proportions of said first, second, and third solvents such that the reaction rates of the zirconium, titanium and lead upon hydrolysis of the resulting mixture will be approximately equal while maintaining the mixture under an inert atmosphere; (f) adding a lanthanum precursor to the mixture; (g) adding a predetermined amount of water to the resulting solution sufficient to begin a hydrolysis reaction without causing precipitation of solids while maintaining the mixture under an insert atmosphere; and (h) boiling the mixture at a temperature sufficient to vaporize the said azeotrope water and solvents until the mixture reaches a viscosity suitable for spin coating.
Claim 14
Independent Claim
201 words
A method of preparing a PLZT mixture suitable for spin deposition on substrates, comprising: (a) solubilizing a lead precursor in a first solvent; (b) solubilizing a titanium precursor in a second solvent; (c) solubilizing a zirconium precursor in a third solvent; (d) mixing under an inert atmosphere at a pressure of from about 350 mmHg to about 650 mmHg the dissolved lead, titanium and zirconium precursor in the first, second and third solvents together at a temperature sufficient to maintain the metals in solution and for a period of time sufficient to produce a homogeneous mixture; (e) adjusting the proportions of said first, second, and third solvents such that the reaction rates of the zirconium, titanium and lead upon hydrolysis of the resulting mixture will be approximately equal while maintaining the mixture under an inert atmosphere; (f) adding a lanthanum precursor to the mixture; (g) adding a predetermined amount of water to the resulting solution sufficient to begin a hydrolysis reaction without causing precipitation of solids while maintaining the mixture under an insert atmosphere; and (h) boiling the mixture at a temperature sufficient to vaporize the said azeotrope water and solvents until the mixture reaches a viscosity suitable for spin coating.
Claim 15
Dependent Claim
38 words
The method of claim 12 comprising the addition of diluting the mixture from step (g) with additional amounts of one or more of said solvents in an amount sufficient to quench the hydrolysis reaction followed by step (h).
Claim 16
Dependent Claim
44 words
The method of claim 12 wherein said precursors of said lead, titanium and zirconium are selected from the group comprising alkoxides, and esters of said lead, titanium and zirconium, and said lanthanum precursor is selected from the group comprising alkoxides, and esters of lanthanum.
Claim 17
Dependent Claim
44 words
The method of claim 13 wherein said precursors of said lead, titanium and zirconium are selected from the group comprising alkoxides, and esters of said lead, titanium and zirconium, and said lanthanum precursor is selected from the group comprising alkoxides, and esters of lanthanum.
Claim 18
Dependent Claim
53 words
The method of claim 12 further comprising the steps of spinning the resulting PLZT solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the PLZT film.
Claim 19
Dependent Claim
53 words
The method of claim 13 further comprising the steps of spinning the resulting PLZT solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the PLZT film.
Claim 20
Independent Claim
216 words
A method for preparing a PLZT mixture suitable for spin deposition on substrates, comprising: (a) solubilizing a lead precursor in a first solvent; (b) solubilizing a titanium precursor in a second solvent compatible with said first solvent; (c) solubilizing a zirconium precursor in a third solvent compatible with said first and second solvents; (d) mixing under an inert atmosphere at a pressure of from about 350 mmHg to about 650 mmHg the dissolved lead, titanium and zirconium precursor in the first, second and third solvents together at a temperature sufficient to maintain the metals in solution and for a period of time sufficient to produce a homogeneous mixture; (e) adjusting the proportions of said first, second, and third solvents such that the reaction rates of the zirconium, titanium and lead upon hydrolysis of the resulting mixture will be approximately equal while maintaining the mixture under an inert atmosphere; (f) adding lanthanum to the mixture; (g) adding water to the resulting solution sufficient to begin a hydrolysis reaction of the precursors without causing precipitation of solids while maintaining the mixture under an insert atmosphere; and (h) boiling the mixture at a temperature sufficient to vaporize the water and said solvents, reducing the solvent and water content of the mixture to increase the viscosity suitable for spin coating.
Claim 21
Independent Claim
216 words
A method for preparing a PLZT mixture suitable for spin deposition on substrates, comprising: (a) solubilizing a lead precursor in a first solvent; (b) solubilizing a titanium precursor in a second solvent compatible with said first solvent; (c) solubilizing a zirconium precursor in a third solvent compatible with said first and second solvents; (d) mixing under an inert atmosphere at a pressure of from about 350 mmHg to about 650 mmHg the dissolved lead, titanium and zirconium precursor in the first, second and third solvents together at a temperature sufficient to maintain the metals in solution and for a period of time sufficient to produce a homogeneous mixture; (e) adjusting the proportions of said first, second, and third solvents such that the reaction rates of the zirconium, titanium and lead upon hydrolysis of the resulting mixture will be approximately equal while maintaining the mixture under an inert atmosphere; (f) adding lanthanum to the mixture; (g) adding water to the resulting solution sufficient to begin a hydrolysis reaction of the precursors without causing precipitation of solids while maintaining the mixture under an insert atmosphere; and (h) boiling the mixture at a temperature sufficient to vaporize the water and said solvents, reducing the solvent and water content of the mixture to increase the viscosity suitable for spin coating.
Claim 22
Dependent Claim
41 words
The method of claim 18 comprising the additional step of diluting the mixture resulting from step (g) with additional amounts of one or more of said solvents in an amount sufficient to quench the hydrolysis reaction thereafter followed by step (h).
Claim 23
Dependent Claim
30 words
The method of claim 18 wherein the precursors of said lead, titanium and zirconium are selected from the group comprising oxides, acetates and esters of said lead, titanium and zirconium.
Claim 24
Dependent Claim
30 words
The method of claim 19 wherein the precursors of said lead, titanium and zirconium are selected from the group comprising oxides, acetates and esters of said lead, titanium and zirconium.
Claim 25
Dependent Claim
53 words
The method of claim 18 further comprising the steps of spinning the resulting PLZT solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the PLZT film.
Claim 26
Dependent Claim
53 words
The method of claim 19 further comprising the steps of spinning the resulting PLZT solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the PLZT film.
Claim 27
Dependent Claim
25 words
The method of claim 18 wherein said lead precursor is lead tetraacetate, said zirconium precursor is zirconium n-butoxide, and said titanium precursor is titanium isopropoxide.
Claim 28
Dependent Claim
25 words
The method of claim 19 wherein said lead precursor is lead tetraacetate, said zirconium precursor is zirconium n-butoxide, and said titanium precursor is titanium isopropoxide.
Claim 29
Independent Claim
158 words
A method of preparing a mixture suitable for spin deposition on substrates, comprising: (a) solubilizing amounts of one or more precursors of lead, titanium, and zirconium in predetermined solvents, said solvents being different for each precursor, at proportions such that upon hydrolysis the metal precursors will exhibit approximately equal reaction rates; (b) mixing the metal precursors and solvents together with lanthanum; (c) maintaining the mixture under an inert atmosphere at a pressure of from about 350 mmHg to 650 mmHg, at a temperature sufficient to maintain the metal precursors and lanthanum in solution, and for a period of time sufficient to produce a homogeneous mixture; (d) adding a predetermined amount of water to the resulting solution sufficient to begin a hydrolysis reaction without causing precipitation of solids while maintaining the mixture under an inert atmosphere; and (e) boiling the mixture at a temperature sufficient to vaporize said solvents and water to increase the viscosity suitable for spin coating.
Claim 30
Independent Claim
158 words
A method of preparing a mixture suitable for spin deposition on substrates, comprising: (a) solubilizing amounts of one or more precursors of lead, titanium, and zirconium in predetermined solvents, said solvents being different for each precursor, at proportions such that upon hydrolysis the metal precursors will exhibit approximately equal reaction rates; (b) mixing the metal precursors and solvents together with lanthanum; (c) maintaining the mixture under an inert atmosphere at a pressure of from about 350 mmHg to 650 mmHg, at a temperature sufficient to maintain the metal precursors and lanthanum in solution, and for a period of time sufficient to produce a homogeneous mixture; (d) adding a predetermined amount of water to the resulting solution sufficient to begin a hydrolysis reaction without causing precipitation of solids while maintaining the mixture under an inert atmosphere; and (e) boiling the mixture at a temperature sufficient to vaporize said solvents and water to increase the viscosity suitable for spin coating.
Claim 31
Dependent Claim
33 words
The method of claim 26 comprising the additional step of diluting the mixture resulting from step (d) with additional amounts of solvents in order to quench the hydrolysis reaction followed by step (c).
Claim 32
Dependent Claim
33 words
The method of claim 26 wherein said precursors are selected from the group comprising alkoxides of lead, alkoxides of titanium, alkoxides of zirconium, esters of lead, esters of titanium, and esters of zirconium.
Claim 33
Dependent Claim
34 words
The method of claim 27 wherein said metal precursors are selected from the group comprising alkoxides of lead, alkoxides of titanium, alkoxides of zirconium, esters of lead, esters of titanium, and esters of zirconium.
Claim 34
Dependent Claim
22 words
The method of claim 26 wherein said precursors are selected from the group comprising zirconium n-butoxide, titanium (IV) isopropoxide, and lead tetraacetate.
Claim 35
Dependent Claim
22 words
The method of claim 27 wherein said precursors are selected from the group comprising zirconium n-butoxide, titanium (IV) isopropoxide, and lead tetraacetate.
Claim 36
Dependent Claim
53 words
The method of claim 26 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the applied thin film.
Claim 37
Dependent Claim
52 words
The method of claim 27 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 475° C. to about 700° C. for a period sufficient to sinter the applied thin
Claim 38
Dependent Claim
53 words
The method of claim 28 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 500° C. to about 650° C. for a period sufficient to sinter the applied thin film.
Claim 39
Dependent Claim
53 words
The method of claim 29 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 500° C. to about 650° C. for a period sufficient to sinter the applied thin film.
Claim 40
Dependent Claim
53 words
The method of claim 30 further comprising the steps of spinning the resulting solution onto a substrate to form a thin film, and then heating the coated substrate at a temperature in the range of from about 500° C. to about 650° C. for a period sufficient to sinter the applied thin film.
Claim 41
Dependent Claim
70 words
The method of claim 1 further comprising the steps of spinning the resulting solution onto a substrate and then heating the coated substrate at a ramp rate of 100° C. per second to a temperature in the range of 725°-775° C., maintaining the temperature in the range of 725°-775° C. for at least about 60 seconds, followed by a ramp down to less than 300° C. in about 90-120 seconds.
Claim 42
Dependent Claim
14 words
The method of claim 37 wherein the heating is performed under an oxygen atmosphere.
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