Theoretical and Experimental Research on Step Coverage Optimization for Integrated Microstructures of Thin Films

A reliable deposition process of thin films must guarantee their material homogeneity and properties. In this context, the metallization of integrated microstructures needs to be performed specific requirements, among which those related to the conformity, respectively to the way in which layers uniformly cover the existing unevenness/steps on the surface of the substrate. This paper deals with studying and experimentation of conformity of metal films on steps, being demonstrated that the geometry of placement of silicon wafers in the evaporation system and the step profile influence the cracks developing. A mathematical model of vacuum evaporation process, validated through numerical simulation and experiment is given. The experiments have consisted of some planarization films (thermal grown SiO2 and deposited, undoped and phosphorous doped, SiO2 using APCVD - a process of Atmospheric Pressure Chemical Vapor Deposition) and Al metallization. Results of slope and roughness measurements, and SEM investigations are presented. Based on them, interesting conclusions are inferred regarding the optimization of working parameters for a uniform covering of the substrates with irregularities.