NF3 and fluorocarbon downstream plasmas were investigated to study downstream chamber cleaning system. As the flow rate of NF3 increases, the etching rate of TEOS increases; however, the etching rate saturated at a given sample temperature. Flamm (1979) showed the etch rate of fluorine is a linear function of the density of F atoms, but did not observe the saturation regime. Under chamber cleaning conditions, the etching rate can be saturated, particularly on the walls where the temperature is lower than in the electrode region. Therefore an understanding of this phenomenon is critical to understanding the rate limiting processes for chamber cleaning. The etching rate was modeled using a physisorbed precursor state in which atomic F is weakly bound to the surface. The physisorbed F reacted with the fluorinated surface in a sequential reaction with a particular reaction step being rate limiting. The reaction model gives the expected first order response with atomic F concentration that was observed by Flamm at low atomic fluorine concentrations in which the etching rate is limited by the combination of adsorption equilibrium and reaction rate. At sufficiently atomic F concentrations, the surface becomes saturated and the etching rate is limited by the surface reaction rate alone. Using these surface kinetics, a well mixed reactor model was used to compute the cleaning of chambers in which surface areas of differing temperatures are exposed to the same atomic F concentration. The results for this model will be discussed for both NF3 and fluorocarbon cleaning of PECVD reactors.