Oxygen-mediated defect evolution and interface analysis of MoOx/n-Si devices

Abstract

The performance of MoOx based devices is highly influenced by the presence of oxygen vacancies and the trap density at the oxide-semiconductor interface. This paper presents a detailed investigation of the surface states present at the MoOx/c-Si interface through capacitance and conductance methods. Thin films of MoOx were deposited on n-Si using DC reactive sputtering of Mo under varying oxygen flow rates and studied the modulation of metal-insulator-semiconductor (MIS) device parameters using appropriate analysis methods. The capacitance-voltage (CV) analysis reveals the formation of nearly dielectric films at an intermediate oxygen flow rate of 15 sccm, exhibiting a dielectric constant of 24 and negative fixed charges of approximately 1.81x1012 cm-2. Work function evaluated from the Kelvin probe measurements was found to be maximum of 5.08 eV for the films deposited at the intermediate oxygen flow rate of 15 sccm. Furthermore, admittance analysis was performed on all the films to determine the loss mechanism in different regions, ranging from inversion to accumulation. Parallel conductance for different bias conditions was studied and observed the domination of oxide traps at the higher oxygen flow (> 20 sccm). Investigation of deep level defects were performed using the deep level transient spectroscopy (DLTS) in the temperature range of 100 K to 475 K, along with the C-V measurements. A transition in C-V behavior was observed below room temperature that shows the minority carrier response time is controlled by generation-recombination at low temperatures and by diffusion at high temperatures. The X-ray photoelectron spectroscopy (XPS) measurements showed that the films are sub-stoichiometric with the dominant oxidation state of Mo+6. The results have been discussed and presented in detail.