Analysis of imperfect chromium source in 1D atom lithography for nanometrology

Periodic nanostructures spaced by half of the wavelength applied for nanometrology can be obtained by laser-focused atomic deposition. Experimental result with standing wave light mask is presented, showing a periodicity of 213 ± 0.1nm, a height of 4nm and a feature width of 64 ± 6nm. To further minimize the feature width and enhance the peak-to-valley contrast of the deposited lines, the effects of imperfect chromium source are numerically simulated with Optimized Particle Optics model, where the initial condition of each trajectory is stochastically selected. Simulation results show that the isotope contributes to the accumulation of background and further broadens the feature width. The predicted line width is sensitive with the oven temperature in thin lens regime. The feature widths obtained are 29nm, 46nm and 75nm respectively when the FWHMs of the transverse angular spread are 0.16mrad, 0.3mrad and 0.5mrad. The transverse angular spread plays a central role in broadening the feature width, even when the longitudinal velocity spread is thermal.