Oxide structure-dependent interfacial layer defects of HfAlO/SiO₂/Si stack analyzed by conductance method

This work investigates the interface properties in a metal oxide semiconductor capacitor device with a 3 nm HfAlO/0.5 nm SiO₂/Si stacks prepared by various processing conditions. Different Al doping, different postannealing temperatures, and different deposition steps and stacks were considered. Equivalent oxide thickness and flat band voltage (V_FB) were obtained from capacitance-voltage measurements. After the measurement, a simple approach was used to correct the error introduced by the series resistance R_s associated with the substrate and contact while carefully monitoring the impact of the tunneling current. The interface state density (D_it) was calculated by the conductance method, and it was observed that the D_it is dependent on the structure of hafnium aluminum oxide film. The amorphous structure has the lowest D_it (2.76 × 10¹¹ eV^-1 cm^-2) whereas tetragonal HfO₂ has the highest D_it (1.27 × 10 12 eV^-1 cm^-2). The D_it values of other structures are within the range of observed highest and lowest values.