Atomic force microscope based patterning of carbonaceous masks for selective area growth on semiconductor surfaces

Carbonaceous masks for selective growth on GaAs substrates were fabricated with high resolution by anodization with an atomic force microscope (AFM). Mask deposition is made by a 15-kV accelerated electron-beam irradiation in a scanning electron microscope. The local anodization of the carbonaceous film under intense electric field is investigated and the main factors for improving resolution and reproducibility are discussed. The "edge effect" o f the anodized region, revealed in the electric-field distribution at the t ip-water-film interfaces is identified as the main factor responsible for t he resolution degradation during patterning. Short forward bias pulse for a nodizing the carbonaceous film and the subsequent reverse bias pulse for ne utralizing the space charge, locally accumulated during the forward bias, a re shown to be effective for the higher pattern resolution and also for dee pening the patterning depth. Based on the analysis, a modulated-amplitude p ulsed bias mode is proposed and is demonstrated to bring a significant impr ovement in the resolution and the aspect ratio of patterns made by the anod ization. Carbonaceous masks ready for selective area growth of semiconducto rs alloys were fabricated with the pattern resolution of similar to 26 nm, limited by the curvature of AFM cantilever tips. (C) 2000 American Institut e of Physics. [S0021-8979(00)10917-X].