Post-CMP dry etching for the removal of the nanoscale subsurface damage layer from a single crystal La3Ga5SiO14 for a high quality wide band SAW filter device

摘要

The nanoscale subsurface damage layer induced on a single crystal La3Ga5SiO14 during the Chemical Mechanical Polishing(CMP)process for surface finishing is removed by a post-CMP dry etching in Cl/Ar inductively coupled plasmas.The electrical conductivity is recovered to the initial value(~1X10~(-4)OMEGA~(-1)·cm~(-1)measured before being CMP-processed with a colloidal silica slurry at etch depths of 43-68 nm,while maintaining a smooth surface morphology.The depth of the subsurface damage layer formed in a langasite single crystal initially increases as a downward force applied to a single crystal La3Ga5SiO14 during the CMP process increases,and then saturates at depths ~68 nm,indicating that the subsurface damage layer induced by the mechanical stress does not form to a depth beyond a critical level.