The Study of Metal (Al)/ Ferroelectric (BiFeO3)/ Insulator (Y2O3)/ Silicon (p-type) MFIS Capacitors and Field Effect Transistors for Nonvolatile Memory Applications

• Main Authors: Chih-Ming Lin, 林志銘
• Other Authors: Joseph Ya-Min Lee
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/39761359415736952983

碩士 === 國立清華大學 === 電子工程研究所 === 96 === Al/ BiFeO3 (BFO)/ Y2O3/ p-Si metal ferroelectric insulator semiconductor (MFIS) capacitors and transistors were fabricated. To compare the effect of different annealing temperature, the BFO thin films were annealed at 500 ℃ and 600 ℃. The BFO films annealed at 500 ℃ show better electrical properties than those at 600 ℃. The maximum C-V memory window was 0.91 V at the annealing temperature of 500 ℃. The corresponding leakage current density was 2 x 10-7 A/cm2 at a bias voltage of 5 V. In addition, a surface treatment method was also used to passivate the Y2O3/Si interface and to reduce the leakage current. The wafers were given a H2O2 pre-treatment before Y2O3 deposition and a HCl post-treatment after deposition. The leakage current density at a bias voltage of 5 V was reduced from 2 x 10-7 A/cm2 to 4 x 10-9 A/cm2. The fabricated MFIS transistors (MFIS-FET) show good transistor characteristics. The subthreshold swing (St) was about 155 mV/dec. The IDS-VGS on-off ratio was approximately 4 orders of magnitude. The maximum electron mobility was 155 cm2/V-s. To measure the memory properties, the shift of IDS-VGS curves was observed. The maximum IDS-VGS memory window was 0.93 V. The drain current on/off ratio was more than 3 orders of magnitude after applying poling voltages of ± 7 V with duration of 10 μs. The IDS maintains an on/off ratio of more than 3 orders after an elapsed time of 104 sec. These results show that the Al/BFO/Y2O3/p-Si structure has great potential for nonvolatile memory applications.