Computer and analytical modeling of phenomena in silicon films under excimer laser irradiation

Structuring of silicon surfaces with excimer laser and in particular the formation of sharp conical tips after a single pulse of KrF excimer laser might have a variety of applications. Sharp cones of this kind can be used as field emitters in vacuum microelectronic devices such as field emission displays (FEDs), vacuum micro diodes and triodes and other field-emission-based (cold cathode) systems. Tall Si cones can also be fabricated for atomic force and scanning tunneling microscopy applications. At the same time, this technology can be used for the fabrication of anti-reflection infrared stealth surfaces and in outer space Si solar cells application.Modeling and computer simulation of processes that occur under laser irradiation is a very affordable way to study the complicated heat and mass transfer phenomena. Not only helps it improve understanding of phenomena but could lead to producing sharper and smaller structures. A quasi-static phenomenological model for cones formation on thin silicon films was developed. The model accounts for difference in solid and liquid silicon densities. The model is also based on condition of lateral heat transfer that exists in thin Si film on SiO 2. It shows that mass transfer from the periphery toward the center of laser spot occurs during the melt solidification. Computer simulations for different film thicknesses confirmed that re-solidification occurs predominately laterally with a phase border moving toward the center of laser spot. Computer simulations for single-pulse irradiation of bulk silicon revealed conditions under which formation of cones could occur. Recommendations for further experimental work were made based on result of computer simulations.