Seltenerd-basierte ternäre Oxide als alternative Gatedielektrika

For the further scaling of silicon-based field effect transistors the use of alternative gate dielectrics with k > 20 - so called high-k dielectrics - is crucial. Only with these materials the leakage currents in the devices can be kept below a critical limit compared to the so far used silicon dioxide. And, the ongoing reduction of feature size of integrated circuits ist the basis for the success of microelectronics industry during the last four decades. Thermodynamic calculations predict that some rare earth based ternary oxides (e.g. REScO3 or REREO3 with RE = Y, La or an element from the lanthanide group) are stable in contact with silicon and therefore being considered for the use as alternative gate dielectrics. In this work, GdScO3 and LaLuO3 thin films deposited with different techniques (pulsed laser deposition, atomic layer deposition and electron beam evaporation) were morphologically and electrically characterized. The produced films are stoichiometric, homogeneous and smooth. They reveal dielectric constants as high as 23 for GdScO3 and even up to 32 for LaLuO3, undisturbed C-V curves and low leakage current densities. Furthermore, a process for the integration of GdScO3 as gate dielectric into silicon-based field effect transistors was developed. The prepared devices show normal transfer and output characteristics. Carrier mobilities of about 120 cm2/Vs for bulk silicon and 155 cm2/Vs for silicon on insulator substrates were determined. The use of strained silicon yields an improvement of 140% for the carrier mobility and about 30% for the maximum drain current and a doubling of the maximum transconductance. The integration of GdScO3 as gate dielectric into AlGaN/GaN-MISHFETs resulted in a reduction of the gate leakage current by four orders of magnitude, a doubling of the output power, and a significant improvement of the power added efficiency. In summary, the results of this work confirm the suitability of the rare earth based ternary oxides GdScO3 and LaLuO3 for the use as alternative gate dielectrics in microelectronics