Effect of Interfacial Native Oxide in Sulphur Passivated N-Indium Phosphide MIS Capacitor with Anodic Oxide and PECVD Silicon Nitride as Gate Di-Electric

This paper deals with the studies on the surface passivation of Indium phosphide (InP) using (NH₄)₂S_x chemical treatment followed by anodic native oxidation and PECVD silicon nitride deposition. MIS capacitors fabricated on n-InP substrates are used as test vehicle for this study. Here MIS capacitors are fabricated by first treating the n-InP substrate with (NH₄)₂S_x  at 80⁰ C followed by anodisation in an aqueous solution of tartaric acid and glycol, PECVD silicon nitride deposition for gate di-electric and alumunium metal for gate metal formation. The current – voltage (I-V) and capacitance – voltage (C-V) characteristics as well as breakdown voltage of these devices are obtained after sequential post metallization annealing carried out at temperatures in the range of 200⁰ C to 450⁰ C. MIS having anodic oxide thickness in the range 0 to 10nm are fabricated to study effects of the oxide thickness on the effectiveness of surface passivation. It is shown that the devices having an oxide thickness of 2nm show reduction in the Interface State density, frequency dispersion and hysterisis on C-V compared to the devices having no oxide layer or the devices with thicker oxide range.