The ASE HRM is an evolution of the previous generations of ICP design, now incorporating a decoupled plasma source (patent pending). This decoupled source generates very high density plasma which is allowed to diffuse into a separate process chamber. Through careful chamber design, the excess ions that are detrimental to process control are reduced, leaving a uniform distribution of fluorine free-radicals at a higher density than that available from the conventional ICP sources. The higher fluorine free-radical density facilitates increased etch rates, typically over three times the etch rates achieved with the original Bosch process. Also, as a result of the reduction in the effect of localised depletion of these species, improved uniformity for many applications can be achieved.〔Hopkins et al. 2004 Developments in Si and SiO₂ Etching for MEMS-based Optical Applications (2004)〕