Surface modification and etch process optimization of fused silica during reaction CHF3–Ar plasma etching

Abstract

The ability to predict and control the influence of reaction ion etching process parameters on laser damage resistance of fused silica optical components is vital for their development in specialized applications such as inertial confinement fusion. In this study, a set of experiments was designed and performed to determine an optimized process condition by characterizing the evolution of the surface roughness and absorption of the fused silica samples treated at various gas flow rates. The macroscopic morphology, carbon concentration and laser damage resistance of the etched surface was measured. The optimized surface was obtained when the gas flow rate R (CHF3/(CHF3+Ar)) decreased down to 38.4%. With the optimized etch process, the presence of subsurface defects known to lead to laser damage initiation was removed and prevented. The C atomic concentration of the sample surface etched was decreased by 64.7%. The laser damage resistance increased dramatically; the average threshold fluence for damage initiation increased from 6.79J/cm2 to 8.99J/cm2.