Tunable Droplet Momentum and Cavitation Process for Damage-freeCleaning of Challenging Particles

摘要

Particle removal without damage has been demonstrated for <60nm photomask sub-resolution assist features withdroplet momentum cleaning technology that employs NanoDroplet~(TM)mixed-fluid jet nozzle. Although 99%+ particleremoval efficiency can be achieved for standard Si_3N_4particles with broad size distribution, there are some cleaningchallenges with small (<100nm) and large contact area (>500nm) particles. It was found that tunable uniform cavitationcan provide the additional physical assist force needed to improve cleaning efficiency of these challenging particleswhile meeting the damage-fee cleaning requirement. An integrated cleaning process was developed that combines bothdroplet momentum and damage-free cavitation technology. Cleaning tests were performed with different types ofchallenging particles. The results showed 5-8% particle removal efficiency improvement as compared to momentumbased only cleaning. All masks were processed using the Tetra~(TM)mask cleaning tool configured with NanoDroplet~(TM)mixed fluid jet technology and full face megasonics.