Removal of Nano-sized Particles Using Carbon Dioxide (CO2) Gas Cluster Cleaning without Pattern Damage

Abstract

As pattern size of semiconductor device becomes less than 20nm, the removal of particles smaller than 10nm without pattern damages requires new physical dry cleaning technology. CO2 gas cluster cleaning is an alternative dry cleaning process to meet these cleaning requirements. To demonstrate gas cluster cleaning performance, particle removal efficiency (PRE) and gate structure pattern damages were evaluated. When pressurized and low temperature CO2 gas was passed through a convergence-divergence (C-D) nozzle, high energy CO2 gas clusters were generated at high speed in a vacuum atmosphere. The cleaning force of the CO2 gas cluster is related to the flow rate of the CO2 gas. The optimum CO2 gas flow rate for the particle removal without pattern damage was found to be 6L/min (LPM). Removal efficiency for 50nm silica particles was greater than 90%, and no pattern damage was observed on 60nm poly-Si and a-Si gate line patterns. It was confirmed that the CO2 gas cluster cleaning force could be controlled by the CO2 gas flow rate supplied to nozzle.