Sub-1/4-µm Periodic Patterns with Nd:YAG Laser and Image Transfer to Silicon Surface by Reactive Ion Etching

Abstract
Quarter-micron linear and dot patterns were made on polyimide surface spin-coated onto silicon substrates with the Q-switched 4th-harmonic UV-pulses of Nd:YAG laser at 266 nm. Shallow polymer images were then transferred to silicon substrates by successive reactive ion etchings of SF6, O2 and SF6–C2ClF5 after filling in valleys of ripples with poly(dimethylsiloxane). We were successful in fabricating ≈ 100 nm silicon structures with vertical wall profiles. Because this process does not use any masks or scanning beam system, nanostructures can be formed on wide surface areas of polymers, silicon, GaAs, and other surfaces. The dimensions can be varied by varying the laser wavelength and geometrical arrangement.