Nanoscale structures by laser direct writing in silicon

Laser-induced pyrolytic etching of silicon by chlorine has been used to process structures with nanoscale resolution. A direct write system has been designed, based on an Ar ion laser with a UV-option, on-axis optics, acousto-optic beam modulation, and high resolution translation stages for sample displacement and for focusing.

The resolution of the process is determined by the size of the melt generated by the focused laser beam. The melt size is a function of optical power, and resolutions better than the focused laser spot diameter are achieved by reducing the power onto the silicon sample. In this way we have etched trenches with a resolution better than 150 nm.

We demonstrate feature sizes of about 40 nm by closely spacing etched trenches. The minimum width of these features is determined by the etch selectivity. The feature width depends on the trench geometry, line spacing, and on scan speed, due to heat flow confinement.