Improvement of capacitance-voltage (C-V) characteristics of YSZ/Si(001) and ZrO 2 /Si thin film by Nb-doping
- PDF / 1,968,365 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 17 Downloads / 195 Views
T7.1.1/N9.1.1
Improvement of capacitance-voltage (C-V) characteristics of YSZ/Si(001) and ZrO2/Si thin film by Nb-doping Naoki Wakiya, Tomohiko Moriya, Kazuo Shinozaki and Nobuyasu Mizutani Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan ABSTRACT Yttria stabilized zirconia (YSZ) and zirconia (ZrO2) thin films without and with Nb-doping were prepared on Si substrate by rf-magnetron sputtering. Undoped YSZ and ZrO2 thin films had (001) orientation, and the orientation was unchanged by the Nb-doping. For both undoped YSZ and ZrO2 thin films, around 2.0 V ion-drift type hysteresis was clearly observed in capacitance-voltage (C-V) characteristics. Nb-doping into YSZ brought about the increase of lattice parameter up to 20 mol% of Nb, which suggests that Nb was incorporated into YSZ lattice up to 20 mol%. By the Nb-doping, the hysteresis in C-V characteristics for YSZ thin film was considerable decreased to around 0.1 V. Drastic suppression of the hysteresis in C-V characteristics was observed for Nb-doped ZrO2 thin film. In this case, the hysteresis was completely disappeared. These facts suggest that oxygen vacancies in YSZ and ZrO2 thin films would be suppressed or disappeared by Nb-doping. This means that Nb is a excellent dopant for both YSZ and ZrO2 to suppress the ion-drift type hysteresis. INTRODUCTION Yttria stabilized zirconia (YSZ) and undoped zirconia (ZrO2) thin films on Si substrate are attractive buffer layer materials for ferroelectric random access memory (FeRAM) and high-k applications due to their high dielectric constants and diffusion barrier characteristics. Therefore, YSZ and ZrO2 thin films on Si substrate have been prepared by several method such as pulsed laser deposition (PLD) [1-3], vacuum evaporation [4], e-beam evaporation [5-8], ion-beam evaporation [9,10] and direct current (DC) sputtering [11-15]. However, both YSZ/Si and ZrO2/Si thin films show ion-drift type hysteresis in capacitance-voltage (C-V) characteristics, which is deleterious for above applications [16]. So far, the reason for the ion-drift type hysteresis was ascribed to the oxygen vacancies [16]. Therefore, it is expected that the hysteresis can be suppressed if the vacancies are disappeared. To suppress the hysteresis, we have reported that decrease of the thickness of YSZ and preparation of CeO2/YSZ double layer structure is effective [17]. However by using this method, it is difficult to suppress the hysteresis completely because, oxygen vacancies still remains. It is expected that doping with high-valence cations such as Nb5+ and Ta5+ is effective to suppress the hysteresis because they would compensate the
T7.1.2/N9.1.2
oxygen vacancies. The purpose of this work is to propose new method to suppress the hysteresis in C-V characteristics by Nb-doping. EXPERIMENTAL All films were deposited by rf-magnetron sputtering. ZrO2 thin films were prepared using metal Zr target (54 mm in diameter). YSZ thin
Data Loading...
