Electrical characteristics of ZrO2/GaAs MOS capacitor fabricated by atomic layer deposition

Abstract

GaAs based metal oxide semiconductor capacitors were fabricated with zirconium oxide (ZrO2) using atomic layer deposition. The effect of growth temperature of ZrO2 dielectric films on GaAs was studied. The ZrO2 layers were deposited using tetrakis dimethyl amido zirconium and water in the temperature region of 200–275 °C. The as deposited samples have a significant amount of fixed charge in the bulk of the gate dielectric and at dielectric/semiconductor (ZrO2/GaAs) interface, which causes the flat band shift and frequency dispersion. The postannealing in nitrogen (N2) reduces the flat band shift, frequency dispersion, and capacitance–voltage (C-V) stretch out. In addition, the inversion characteristics of as fabricated capacitor were also improved with respect to the growth temperature and annealing. The gate dielectric stack is qualitatively illustrated through improved C-V characteristics and quantitatively verified by the reduced interface trap density (Dit). The effect of N2 annealing is investigated in detail through electrical characterization and Dit measurements. The authors find that there exists a tradeoff where annealing improves C-V characteristics and reduces the Dit, however, at the cost of higher leakage current.