US5626728A
Expired / Lapsed
US
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Piezoelectric lead zirconium titanate device and method for forming same
Assignee: Apple Inc
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Filing: 1994-05-27
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Granted: 1997-05-06
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Expires: 2014-05-27
Abstract
Abstract A piezoelectric device, such as a surface acoustic wave filter, comprises a piezoelectric film composed of a lead zirconium titanate compound applied to a substrate formed of silicon or gallium arsenide. The device includes an intermediate film between the piezoelectric film and the substrate and composed of a lead-free zirconium titanate compound to prevent interaction between lead oxide in the piezoelectric material and the material of the substrate that would otherwise cause spilling or adversely effect the electrical properties of the substrate. The piezoelectric device is made by first applying the film of the lead-free zirconium titanate compound and thereafter applying the film of the lead zirconium titanate compound. Preferably, the lead-free zirconium titanate film is applied by sputtering and annealed to densify the material and increase the dielectric constant prior to depositing the piezoelectric material.
Inventors
- 👤 Ed S. Ramakrishnan
- 👤 Wei-Yean Howng
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 11:04
CPC Classifications
H; H10; H10N; H10N30/00; H10N30/01; H10N30/07; H10N30/074; H10N30/079; H10N30/076; H10N30/80; H10N30/85; H10N30/853; H10N30/8548; H10N30/8554
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
173 words
A method for coating a piezoelectric film onto a substrate selected from the group consisting of silicon and gallium arsenide, said method comprising depositing a first film onto the substrate, said first film being composed of a lead-free zirconium titanate compound having the formula Zr.sub.y Ti.sub.1-y O.sub.4 where y is between about 0.3 to 0.65, annealing the first film by heating at a temperature and for a time effective to densify the lead-free zirconium titanate compound to form an annealed first film having a dielectric constant between about 25 and 60, depositing a second film onto the annealed first layer, said second film being composed of a lead zirconate titanate compound characterized by the formula Pb.sub.a M.sub.1-a (Zr.sub.b Ti.sub.1-b)O.sub.3 where M is a metal selected from the group consisting of lanthanum, niobium, antimony, tungsten, tantalum, barium, strontium, neodymium, and tin and a is between about 0.9 and 1.0 and b is between about 0.5 and 0.7, and heating the second film to a temperature and for a time effective to produce piezoelectric properties.
Claim 2
Independent Claim
173 words
A method for coating a piezoelectric film onto a substrate selected from the group consisting of silicon and gallium arsenide, said method comprising depositing a first film onto the substrate, said first film being composed of a lead-free zirconium titanate compound having the formula Zr.sub.y Ti.sub.1-y O.sub.4 where y is between about 0.3 to 0.65, annealing the first film by heating at a temperature and for a time effective to densify the lead-free zirconium titanate compound to form an annealed first film having a dielectric constant between about 25 and 60, depositing a second film onto the annealed first layer, said second film being composed of a lead zirconate titanate compound characterized by the formula Pb.sub.a M.sub.1-a (Zr.sub.b Ti.sub.1-b)O.sub.3 where M is a metal selected from the group consisting of lanthanum, niobium, antimony, tungsten, tantalum, barium, strontium, neodymium, and tin and a is between about 0.9 and 1.0 and b is between about 0.5 and 0.7, and heating the second film to a temperature and for a time effective to produce piezoelectric properties.
Claim 3
Dependent Claim
14 words
A method in accordance with claim 1 wherein y is between 0.4 and 0.6.
Claim 4
Dependent Claim
11 words
A method in accordance with claim 1 wherein M is lanthanum.
Claim 5
Dependent Claim
40 words
A method in accordance with claim 1 wherein the step of depositing the second film comprises sputtering the lead zirconium titanate compound onto the first film to form the second film having a thickness between about 2 and 10 microns.
Claim 6
Dependent Claim
39 words
A method in accordance with claim 1 wherein the step of depositing the first film comprises sputtering the lead-free zirconium titanate compound onto the substrate to form the first film having a thickness between about 750 and 2500 Angstroms.
Claim 7
Independent Claim
162 words
A method for coating a piezoelectric film onto a silicon substrate, said method comprising sputtering a lead-free zirconium titanate compound onto the substrate to form a first film having a thickness between about 750 and 2500 Angstroms, said lead-free zirconium titanate compound having the formula Zr.sub.y Ti.sub.1-y O.sub.4 where y is between about 0.3 to 0.65, annealing the first film by heating at a temperature effective to densify the lead-free zirconium titanate compound, sputtering a lead zirconium titanate compound onto the annealed first film to form a second film having a thickness between about 2 and 10 microns, said lead zirconate titanate compound having the formula Pb.sub.a M.sub.1-a (Zr.sub.b Ti.sub.1-b)O.sub.3 where M is a metal selected from the group consisting of lanthanum, niobium, antimony, tungsten, tantalum, barium, strontium, neodymium, and tin and a is between about 0.9 and 1.0 and b is between about 0.5 and 0.7, and annealing the second film by heating at a temperature effective to produce piezoelectric properties.
Claim 8
Independent Claim
162 words
A method for coating a piezoelectric film onto a silicon substrate, said method comprising sputtering a lead-free zirconium titanate compound onto the substrate to form a first film having a thickness between about 750 and 2500 Angstroms, said lead-free zirconium titanate compound having the formula Zr.sub.y Ti.sub.1-y O.sub.4 where y is between about 0.3 to 0.65, annealing the first film by heating at a temperature effective to densify the lead-free zirconium titanate compound, sputtering a lead zirconium titanate compound onto the annealed first film to form a second film having a thickness between about 2 and 10 microns, said lead zirconate titanate compound having the formula Pb.sub.a M.sub.1-a (Zr.sub.b Ti.sub.1-b)O.sub.3 where M is a metal selected from the group consisting of lanthanum, niobium, antimony, tungsten, tantalum, barium, strontium, neodymium, and tin and a is between about 0.9 and 1.0 and b is between about 0.5 and 0.7, and annealing the second film by heating at a temperature effective to produce piezoelectric properties.
Claim 9
Dependent Claim
32 words
A method in accordance with claim 6 wherein the step of annealing the first film comprises heating the first film in air at a temperature between about 700° C. and 875° C.
Claim 10
Dependent Claim
32 words
A method in accordance with claim 6 wherein the step of annealing the first film comprises heating the first film in air at a temperature between about 750° C. and 825° C.
Claim 11
Dependent Claim
34 words
A method in accordance with claim 6 wherein the step of annealing the first film comprises heating the first film in a non-oxidizing atmosphere at a temperature between about 850° C. and 1050° C.
Claim 12
Dependent Claim
34 words
A method in accordance with claim 6 wherein the step of annealing the first film comprises heating the first film in a non-oxidizing atmosphere at a temperature between about 925° C. and 1025° C.
Claim 13
Dependent Claim
32 words
A method in accordance with claim 6 wherein the step of annealing the second film comprises heating the second film in air at a temperature between about 700° C. and 800° C.
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