A low-temperature preparation of ferroelectric Sr_xBi_(2+y)Ta_2O_9 thin film and its application to metal-ferroelectric-insulator-semiconductor structure

摘要

Preferentially (105)-oriented Sr_(0.7)B_(2.8)Ta_2O_9 (SBTO) thin films on SiO_2-Hi (100) have been prepared by pulsed laser deposition at temperatures as low as 350 beg C, which is the lowest process temperature for growing SBTO ferroelectric thin films. Dielectric properties of the SBTO films have been improved by increasing the Sr/B atomic ratio from 0.7/2.8 to 0.7/2.0. Memory windows of as large as 3.6 and 4.3 V in the MFIS capacitor have been obtained at Sr/B ratios of 0.7-2.0 and 1.0/2.0 respectively and are the largest values reported in the MF(I)S diode structures. Little C-V degradation is observed up to with the 10~(10) cycles for the process temperature of 400 deg C, especially for Sr/B of 0.7/2.0, with the memory window remaining at more than 3.2 V. Memory retention time was about 3 X 10~3 s at which the difference in capacitance between 'ON' and 'OFF' states reduces to half of its initial value. Optimum hold bias voltage exists in the retention test. Improvement in memory characteristics is strongly related to the insulating properties of the ferroelectric and dielectric thin films rather than the value of dielectric constant.