Study Of Laser Induced Plasma Shockwave To Clean Nanoparticles On Surface Of Silicon Wafer

Nanoparticles pollution on silicon surface could easily lead to generation of defects. The traditional chemical cleaning method is noneffective due to the secondary pollution on the silicon surface. Laser induced plasma shock wave cleaning technology is a new method which can effectively remove these particles adhering on the surface. This technology has been widely used in various fields due to its accurate cleaning positioning, avoiding secondary pollution and broad range of application etc. This technology provides a new way for cleaning nanoparticles on silicon substrate in the semiconductor industry.In this paper, we demonstrate the experimental study concerning on the removal polystyrene latex(PSL) particles in diameter of 500 nm from silicon surface by nanosecond laser induced plasma shockwave in the air. We study the effect on removal efficiency by different parameters including gap distance, laser energy and pulse number. The results show that with the decrease of gap distance and/or increase laser energy, the removal efficiency increases rapidly. With the accumulation of pulse number, the image of cleaning area changes from annular to circular. We utilize rolling model to numerically simulate the influence of gap distance and laser energy on the result of cleaning. The simulation results agree well with the experimental results. Via the analysis on numerical simulation of cleaning effect on shock wave propagation distance and experiment result with different pulse number(cleaning pattern changed from annular to circular), we identify that laser plasma shock wave clean process could be completed with the combination of rolling mechanisms and bouncing mechanisms. We also find that the cleaning efficiency can be enhanced close to 100% and silicon substrate damage can be avoided by the aberration of focal lens.