High Efficiency Wafer Backside Cleaning with Full Coverage Megasonics Spin Process

As the technology node scales down to 45nm and beyond, removal of particles and metal contamination from wafer backsides have become critical for advanced lithography with smaller depth of focus, as well as to enable efficient metrology tool sharing between various applications. Smaller particles are usually held by van der Waals’ force, and removal of these particles usually requires mechanical force, such as acoustic energy which creates cavitation. Just as the wafer frontside, backside cleaning requires full liquid coverage for high efficiency cleaning. Backside clean with full coverage backside megasonics can achieve higher particle removal efficiency (PRE), especially for smaller particles. In this paper, we report a novel full coverage backside megasonic spin process that demonstrates high PRE and metal contamination removal and achieve high PRE for advanced lithography and wafer metrology.