Damage-free plasma etching of porous organo-silicate low-k using micro-capillary condensation above-50 °C

The micro-capillary condensation of a new high boiling point organic reagent (HBPO), is studied in a periodic mesoporous oxide (PMO) with similar to 34 % porosity and k-value similar to 2.3. At a partial pressure of 3 mT, the onset of micro-capillary condensation occurs around +20 degrees C and the low-k matrix is filled at -20 degrees C. The condensed phase shows high stability from -50 < T <= -35 degrees C, and persists in the pores when the low-k is exposed to a SF6-based plasma discharge. The etching properties of a SF6-based 150W-biased plasma discharge, using as additive this new HBPO gas, shows that negligible damage can be achieved at -50 degrees C, with acceptable etch rates. The evolution of the damage depth as a function of time was studied without bias and indicates that Si-CH3 loss occurs principally through Si-C dissociation by VUV photons.