Growth and Characterization of Silicon Dioxide Thin Films Developed by Anodic Oxidation

Silicon dioxide (SiO2) is also known as silica, it is a chemical compound that is an oxide of silicon. Thin films of silicon dioxide are most widely used in the fabrication of silicon based integrated/discrete devices (e.g. diode, transistors, etc.), integrated circuits (ICs) and microelectromechanical systems (MEMS) fabrication for various purposes. The SiO2 layer has been used as surface passivation to protect semiconductor devices from contamination, gate dielectric in metal oxide semiconductors (MOS), mask against diffusion and implantation of dopants into silicon, dielectric in the storage capacitors of DRAM memories, isolating the devices from one another on the same chip, as sacrificial and etch mask layer in MEMS fabrication. Several techniques has been well established to prepare the silicon dioxide films in different processing environments, however Thermal oxidation, Sputtering, Chemical Vapor Deposition are most commonly used. Among the various existing techniques of silicon dioxide synthesis Anodic oxidation of silicon is one of the technique which can be operated even below room temperature. The Anodic oxidation process offers several advantages over other techniques such as low cost of process, simple experiment set up, does not involve any toxic and expensive gases, etc. The present work is aimed to investigate the effect of various parameters such as current density, final voltage, and composition of the electrolyte on different characteristics of the as-grown oxide films. Uniform and non-porous silicon dioxide thin films are obtained at small water content added into the electrolyte. The thickness of the oxide increases as the water content in the electrolyte increased. Various characterization tools such as Ellipsometry, SEM and FTIR are employed to characterize the thickness, refractive index, surface morphology and chemical composition of the as-grown oxide thin films