Paper PS2-FrM2
Silicon Etching using CW, Synchronized Pulsed and Bias Pulsed Cl₂ Plasma

Friday, November 14, 2014, 8:40 am, Room 308

The semiconductor industry is more and more challenged by the miniaturization of integrated circuits and the introduction of new devices architectures. Typical high density plasma show limitations in terms of anisotropy, selectivity and ion induced damages to etch stacks of ultrathin layers. New plasma technologies that provide an atomic level control of etching processes are now required and pulsed plasmas are promising candidates. In this work, we compare the performances of typical CW ICP plasma with synchronous pulsed plasma (ICP and bias power pulsed in phase) and bias pulsed plasma (ICP is CW and bias pulsed). In each case we use Cl₂ plasma to etch silicon and several parameters are monitored including etch rate, surface roughness, thickness of SiCl_x reactive layer, ions flux and ions energy. We also investigate the importance of the surface preparation. Using atomic force microscopy, we show that (by contrast with CW plasmas) the surface roughness increases as a function of etching time in pulsed plasmas and that this worsens at small duty cycle. Preliminary results of molecular dynamic simulations suggest that this could be attributed to the modulation of the ion energy in pulsed plasma: in the OFF period radicals can attack the surface defect created by individual ions impacts during the previous ON period.