Alumina layers deposited with different precursors for different microelectronic applications

Alumina thin films are widely used as barriers in HF etch processes in modern microelectronics. In various microelectronic applications, films deposited on driving electrodes of MEMS devices, such as those made of alumina, might be responsible for various charging effects leading to the degradation of actuator performances. This necessitates high-quality alumina layers with a low density of defects and interface states. In the present study, we compare the electrical properties of alumina layers deposited with different oxidants (ozone and water) using the atomic layer deposition technique. Capacitance-voltage measurements reveal that all as-deposited alumina layers contain negatively charged defects, but their concentration is significantly higher in layers prepared with ozone. The origin of these defects will be discussed. Furthermore, we demonstrate that the density of interface states in layers prepared with ozone is also significantly higher compared to those prepared with water. However, this can be optimized by varying the deposition temperature or the flow of O₃. Such defects also influence current-voltage characteristics, which are also analysed in this study.