Pattern Collapse and Particle Removal Forces of Interest to Semiconductor Fabrication Process

The removal of particles from silicon wafers without pattern damage during fabrication process is extremely important for increasing the yield. Various physically assisted cleaning techniques such as megasonic cleaning, jet spray cleaning, and laser shock wave cleaning (LSC) have been introduced. However, most of tools show pattern damage [1]. One of the main challenges in next generation cleaning process is the particle removal without the pattern damage. As the feature size continues to decrease, the patterns are so fragile that it is hard to remove particles less than 50 nm without pattern damages. To accomplish the effective cleaning performance without the damage, the collapse force of pattern and removal force of particle should be known quantitatively. In this paper, pattern collapse forces were measured for different gate stack patterns by lateral force microscope (LFM) [2]. The particle removal mechanism of LSC was studied to find the relationship between measured collapse forces and particle removal force by LSC which has a known applied force. Finally, particle contaminated pattern wafers were cleaned by LSC with optimized process parameters to verify the relationship and to achieve the best particle removal performance without the pattern damage.