Various effects taking place in plasma etch systems exert essential influence upon process characteristics and control. In this study pressure control valve (PCV) operation during dielectric etch processes in MERIE (magnetically enhanced reactive ion etching) reactor was investigated. Growth of polymers on grating type baffle separating plasma and exhaust zones of the reactor is causing the exhaust conductance and in this connection chamber pressure to change dynamically. During running of an evaluated process based on increased gas flow of high-molecular fluorocarbon and argon mixture fast changes in PCV behavior were observed. Intensive polymerization was suspected to be a main reason for these changes. Detailed monitoring of chamber manometer and PCV readings let to evaluate polymers rates of growth and shrinkage and dynamics of some other processes affecting the valve movement, and also define the limitations for pressure control. The polymers formed on anodized aluminum chamber parts were found to be thick, very dense and hard. Detailed examinations of the polymeric stratums showed that they consisted of many thin layers. The thickness of one layer was just about a hundred nanometers. Thus we could suppose that every single layer of formed polymer refers to individual wafer. Chemical analysis of the polymers showed that they consist mostly of fluorine and carbon. Ratio of fluorine to carbon contents was about 2 to 1. The investigation results show that polymers formed during plasma etching may significantly decrease pumping and pressure control systems capability depending on temperature, structure, density and volume of the polymers. Process pressure, mass flow of gas mixture components and correlation between RF power on and RF power off time intervals were found to be the main factors responsible for polymers formation and behavior.