Active control of surface integrity in thin film scratching and finishing

Thin films are widely adopted to improve resistance to chemicals, high temperature, etc. However, their hard and brittle nature imposes great challenges to achieve satisfactory surface integrity control in finishing process. To address this, an active bending methodology via piezoelectric actuator is proposed to investigate the thin film response on and beneath the surface, under different stress states. An analytical model is established and verified by experiments, which demonstrate distinct nano scratching regimes on a Si3N4 film. Based on this active stress control approach, macroscale bonnet polishing was conducted and showed great improvement in surface roughness and material removal.