Crystallographically aligned ferroelectric films usable in memories and method of crystallographically aligning perovskite films
US5155658A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 5, 1992 |
| Grant date | Oct 13, 1992 |
| Priority date | — |
| Expiry date | Mar 5, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D1/692
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
A ferroelectric memory and its method of making in which a highly c-axis oriented layer (56) of ferroelectric lead zirconate titanate (PZT) is epitaxially deposited at between 640.degree. and 710.degree. C. upon a crystalline film (54) of yttrium barium copper oxide (YBCO), acting both as growth template and bottom electrode. A top electrode (58) is formed over the ferroelectric layer to complete the memory element. The two electrodes are preferably composed of the same perovskite conductor of the same cyrstalline orientation, most preferably, a-axis oriented YBCO. The structure can be grown on a silicon substrate (50) with an intermediate buffer layer (52) of yttria-stabilized zirconia. The ferroelectric behavior is optimized if the structure is cooled from its growth temperature at about 20.degree. C./min. Such a-axis oriented perovskite thin films can be grown by continuously depositing the same or different perovskite material, but dividing the deposition into three temperature stages, a first at a temperature favoring a-axis oriented growth, a second gradually increasing the temperature to a temperature favoring c-axis growth, and a third at the c-axis growth temperature. None…
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