A time-multiplexed, anisotropic, inductively coupled plasma Si deep reactive ion etch process is characterized in terms of the Si macroload, cross-wafer spatial variation, local pattern density, and feature size. The process regime is established as neutral flux limited, in which material transport occurs in the molecular flow to transition flow regimes. For this process regime, a semiempirical, unified analytic model and a numeric model are developed using the Dushman and Clausing vacuum conductance correction factors, respectively, in the Coburn and Winters model of aspect ratio dependent etching. The experimental reaction probability for etching of Si by F was found to be 0.24 for Dushman's factor and 0.22 for Clausing's factor. Each model is validated to +/- 10% against experimental depth data for microdonut and trench test structures and match each other to within 10% for depths of up to 160 mu m. The observed depth range is 64 mu m at a depth of 160 mu m. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3305716]