Laser-induced convection nanostructures on SiON/Si interface

The homogenized beam of an excimer KrF laser has been used to form rectangular millimeter-scale holes of vertical walls in the ∼1 μm thick silicon-oxynitride (SiON) thin film deposited on Si <111> wafer. The regular rectangular craters in SiON layer have the flat bottom surface reaching the SiON/Si interface. At the same time horizontal thermal gradient causes the formation of the nanoscale Marangoni convection structures at the SiON/Si interface. The inhomogeneous pattern of the roll structures can be divided into domains of regular, irregular, and chaotic organizations. The roll diameter is about 200 nm while their average wavelength, Λ, is, ∼2 μm, i.e., about ten times larger than the laser wavelength, and decreases with increasing number of pulses. Numerical simulation of the Marangoni domain roll structures based on the simple Swift-Hohenberg equation has reproduced all observed types of the roll organization, including those that show the evolution of dislocations from the Eckhause instability