Investigation of laser recrystallization of thin Si-films using numeric simulation
Laser recrystallization of polycrystalline silicon films which are encapsulated in silica layers and may be seeded via seeding holes to bulk materials is widely investigated for the goal to obtain base materials for Silicon-on-Insulator (SOI) or 3-Dimensional (3D) devices. While doing experimental investigations in laser physics and material science, many approaches of numeric simulations are made. Our cystal growth modeling shows that the temperature distribution controls the facets formation during recrystallization which in turn determines the average distance between neighboring grain boundaries which are one of the most significant defects in the laser recrystallized films. One successful way to reduce crystal defects is to enlarge and localize the facets of crystal growth using the concept of spatially modulating the temperature profile by optical aobsorber strips on the Wafer. On the other hand, because the formation of grain boundaries may originate from stress in the new recry stallized film due to the different densities of liquid and silicon and the geometrical nonuniformity of faceted films, to reduce the size of facets and thus the stress may be another possibility. Based on this idea we introduced a new concept called micro absorber to modulate the temperature profile so that the size of facets were kept under several microns. Using this technique areas free of grain boundaries of up to 100 mym x 50 mym have been obtained.