Wafer-to-wafer process reproducibility is one of the major concerns in plasma etching of thin films with high density inductively coupled reactors, which are widely used for integrated circuit manufacturing. These reactors are typically operated at low pressures, where the mean free path of species in the plasma is on the order of the reactor dimensions, and reactive radicals collide as often with the chamber walls as they do with each other in the gas phase. Thus, the plasma chamber walls play a crucial role in determining the discharge properties such as ion density, electron temperature, and species concentration. Often, a stack of thin films of different materials is etched sequentially using multiple gases in the same chamber. Chemicals used and/or produced during the etching of one film may adsorb or deposit on the walls of the reactor and alter the chemical reactivity of the walls. The changing wall conditions cause variations in the discharge properties directly affecting etching reproducibility. This problem of process sensitivity to the wall conditions has been known for a long time but its management has remained an art. This talk will review the advances made towards improving the understanding of plasma-wall interactions using various plasma diagnostic techniques as applied to specific chemistries used for plasma etching proceses used in integrated circuit manufacturing.