CHARACTERISTICS OF METAL-FERROELECTRIC-INSULATOR-SILICON DEVICES USING HFSION BUFFER LAYERS

ABSTRACT

In this work, metal-ferroelectric-insulator-silicon (MFIS) devices were fabricated using HfSiON as buffer layers and their electrical properties were studied. Ultra-thin HfSiON films were fabricated by electron-beam evaporation at room temperature and post-annealed using different parameters such as temperature, time in O₂. By annealing a 2 nm-thick HfSiON film at 800°C for 60s in O₂, a negligible hysteresis loop and small equivalent oxide thickness of 2.3 nm were obtained with a corresponding leakage current density of 6.8 × 10^{− 5} A/cm² at a voltage shifted from the flat band voltage by 1 V. In the fabrication of MFIS diodes, Sr_0.8Bi_2.2Ta₂O₉ (SBT) films with 400 nm thickness were formed by chemical solution deposition. For Pt/SBT (400 nm)/HfSiON(2 nm)/Si diodes, a memory window of 0.8 V in width was observed during double capacitance-voltage sweep between +5 and –5 V. At the same time, excellent data retention properties were observed. The high and low capacitances in the hysteresis loop were well distinguishable even after 24 h had elapsed.

Keywords:

• MFIS devices
• buffer layer
• HfSiON
• retention property
• Sr_0.8Bi_2.2Ta₂O₉

ACKNOWLEDGMENT

This work was performed under the auspices of the Special Coordination Funds for Promotion Science and Technology supported by the Ministry of Education, Culture, Sports, Science and Technology. One of the Authors (X. B. Lu) wishes to acknowledge the Japan Society for Promotion of Science (JSPS) for the award of a JSPS fellowship.