Use of calcium and strontium dopants to improve retention performance in a PZT ferroelectric film
US5800683A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 22, 1997 |
| Grant date | Sep 1, 1998 |
| Priority date | — |
| Expiry date | May 22, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L21/02266
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
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…
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