Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Patent
1997-05-22
1998-09-01
Beck, Shrive
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
20419215, 20419218, 2041922, 20419222, 20429813, C23C 1440
Patent
active
058006834
ABSTRACT:
A lead zirconate titanate ferroelectric film used as the dielectric layer in a ferroelectric capacitor is doped with calcium and/or strontium, and the lead composition selected to improve data retention performance. The chemical formula for the ferroelectric film is: (Pb.sub.v Ca.sub.w Sr.sub.x La.sub.y)(Zr.sub.z Ti.sub.(1-z))O.sub.3 ; wherein v is ideally between 0.9 and 1.3; w is ideally between 0 and 0.1; x is ideally between 0 and 0.1; y is ideally between 0 and 0.1, and z is ideally between 0 and 0.9. In addition, the chemical composition of the ferroelectric film is further specified in that the measured opposite state charge at a specific time and temperature of the ferroelectric capacitor is greater than eight micro-Coulombs per square centimeter, and the rate of imprint degradation is less than fifteen percent per decade. The method for making the ferroelectric film as the dielectric layer in a ferroelectric capacitor includes sputtering onto a bottom electrode from a target comprising lead zirconate titanate doped with the combination of or subcombinations of calcium, strontium, and lanthanum to a film thickness between 750 Angstroms and 5000 Angstroms. A top electrode is subsequently formed, wherein the top and bottom electrodes are typically noble metals such as platinum. The resultant ferroelectric capacitor is coupled to an integrated MOS transistor to form a ferroelectric memory cell with improved retention performance.
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Davenport Tom
Hadnagy Domokos
Kammerdiner Lee
Beck Shrive
Meeks Timothy
Meza, Esq. Peter J.
Ramtron International Corporation
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