Authors: I. Kim, J.W. Lee
Affilation: POSTECH, Korea
Pages: 382 - 385
Keywords: CO2, supersonic nozzle, nano-bullet, cleaning efficiency
The removal of contaminant particles(CPs) as small as 10nm from wafer surface is essential in successful fabrication of nano-scale devices. The supersonic particle beam technique using nano-sized volatile bullet particles(BPs) was extremely effective in removing CPs in the 10nm size range, but was not very effective for CPs as big as 50-100 nm. In this study, an improved nano particle beam technique was developed, where a mixture of bullet particles of different sizes were used instead of mono-disperse bullet particles. Nano-sized CPs were selectively removed by using bullet particles of two different sizes. Nanometer-sized BPs were generated by gas-phase nucleation and growth in a supersonic nozzle, and different BP sizes were obtained by adjusting the stagnation pressure and nozzle geometric. CO2/He mixture gas was used to generate BPs travelling at supersonic velocities. Cleaning performance was sensitive to the BP size and velocity. Small BPs removed the 10~30nm CPs selectively, and big BPs worked on the CPs 30nm or larger. When two different BPs were used sequentially, we obtained cleaning efficiency about 99% for 10~100nm Al2O3 CPs. This is the first ever report of a successful removal of CPs in the 10nm range with a wide size distribution.