Radical Etching

The mechanism for radical etching can be gleaned from the Lennard-Jones diagram for thermal etching. For radical etching, the incoming species are radicals unlike molecules in thermal etching. The benefit of radical etching is a larger process window with respect to surface temperature compared to thermal etching. Like thermal etching, radical etching also uses only neutral species. The elementary process steps of radical etching are the radical transport to the surface, adsorption, surface reaction, and desorption. Etching rate nonuniformity is primarily driven by the flux uniformity to the wafer. The selectivity of radical etching can be boosted using passivating gases. Radical etching is an isotropic etching technology like thermal etching and thermal isotropic atomic layer etching. The root cause for aspect ratio dependent etching in radical etching is the transport of radicals to the etching front. The most widely used radical etching process is the removal or stripping of photoresist or carbon hardmasks.