FERROELECTRIC C-AXIS ORIENTED Pb_5Ge_3O_(11) THIN FILMS FOR ONE TRANSISTOR MEMORY APPLICATION

摘要

One transistor memory devices have been proposed recently. To meet the needs of one transistor memory applications, C-axts oriented Pb_5Ge_3O_(11) (PGO) thin films were prepared using metalorganic chemical vapor deposition (MOCVD) and rapid thermal processing (RTP). It was found that the nucleation of C-axis Pb_5Ge_3O_(11) phase started at a deposition temperature below 400°C and grain growth dominated at 500°C or above. With increasing annealing temperature, the remanent polarization (Pr) and coercive field (Ec) values increased, and the hysteresis loops of the Pb_5Ge_3O_(11) films were well saturated and symmetrical after the post-annealing. The C-axis PGO thin film showed good ferroelectric properties at 5V: 2Pr and 2Ec values were 2.0 - 4.0 μC/cm~2 and 90 - 110 kV/cm, respectively. The films also showed excellent fatigue characteristics: no fatigue was observed up to 1 × 10~9 switching cycles. The retention and imprint properties have also been studied. The leakage currents of the PGO films were 2-5×10~(-7) A/cm~2 at 100 kV/cm and dielectric constants were 40 - 70. The high quality MOCVD Pb_5Ge_3O_(11) films can be used for single transistor ferroelectric memory devices.