(Invited) Development of New High-Dielectric Constant Thin Films By Combinatorial Synthesis

Abstract

The development of high-dielectric constant film materials is essential for future active and passive nanoelectronics devices. By using combinatorial synthesis, high throwput material development, we developed high-dielectric constant film materials for film capacitor and gate dielectrics.In the case of the passive devices, we focused on the power device application. Power devices such as SiC require high-temperature operational passive devices, which are capable of operating over 250°C. For module and system level advancement, the high-temperature operational passive should be developed urgently. By employing combinatorial method and the thermal diffusion theory, we found some candedates based on ferroelectric materials. For the relaxor feroelectric, the permitivity of 400 and the stability <8% from room temperature to 400°C has been obtained, which are promising as a high-temperature dielectric medium. In the presentation, we also introduce the development of new high-k gate materials for GaN and Ge channels. For a Ge channel, which has been attracting a lot of attention as a replacement for the Si channel used in current Si-based metal-oxide-semiconductor (CMOS) devices. This is because the Ge channel has high electron and hole mobility, which lead to a higher drive current, and Ge has a narrower band gap than Si thus allowing supply voltage scaling. However, Ge has the same issue as Si, namely an unintentionally oxidized layer with a low dielectric constant (~5.6) can form at an oxide/Ge interface. Furthermore, in contrast with SiO2, which is a good insulating layer for MOS devices, GeOx is thermodynamically unstable and water soluble. These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage characteristic. To overcome these issues, we have proposed the direct growth of (110) rutile TiO2 or non-oxide materials on (100) Ge substrates.