The Fabrication and Characterization of Metal (Al)/ La2O3/p-Si Capacitors And Field-effect Transistors

• Main Authors: Hong-Wen Chou, 周鴻文
• Other Authors: Ya-Min Lee
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/40956665428475841788

碩士 === 國立清華大學 === 電子工程研究所 === 92 === Metal-oxide-semiconductor (MOS) capacitors that incorporate La2O3 dielectrics were fabricated by RF magnetron sputtering. In this work, the essential structures and electrical properties of La2O3 thin film were investigated. C-V, X-ray energy dispersive spectrometer (EDS) and TEM analyses reveal that an interfacial layer was formed, reducing the κ-value of the annealed La2O3 thin films. The conduction mechanisms of the Al/La2O3 (24 nm)/p-Si metal-lanthanide oxide-semiconductor structure were also studied. The J-V characteristics of the MOS capacitors in accumulation showed the behavior of space charge limited conduction with traps. Three different regions, namely Ohm’s law, trap filled limited and Child’s law were explicitly observed in J-E characteristics at room temperature. The activation energy in the trap filled limited region calculated from the Arrhenius plots was about 0.21±0.01 eV. This energy was attributed to the shallow traps, distributed near the conduction band edge in the forbidden gap of La2O3. The electronic mobility, trap density, dielectric relaxation time and density of states in conduction band were determined from the space charge limited currents at room temperature. The dielectric constant measured from a separate metal- La2O3-silicon capacitors is 16. At high temperature (470 K) and low field (≦2.25 MV/cm), the conduction mechanisms of the Al/La2O3 (18 nm)/p-Si metal-lanthanide oxide-semiconductor structure was studied to be Schottky emission. And barrier height of Al/La2O3 of 0.95 eV is deduced. The band diagram of the Al/La2O3 /p-Si metal-lanthanide oxide-semiconductor structure was also constructed. N-channel metal-oxide-semiconductor field effect transistors (MOSFETs) using La2O3 gate oxide were fabricated successfully. The La2O3 films were deposited by RF magnetron sputtering. The C-V, ID-VD and ID–VG characteristics are measured. The threshold voltage was -1.0 V. The subthreshold swing was 167 mV/dec. The ION/IOFF ratio is about 105 at VD=0.1 V. Since St=2.3(kT/q)[1+(CD+Cit)/Cox], the interface trapped charge density Dit is extracted to be about 5.42x1012 cm-2-eV-1.