Low-voltage electron-beam lithography with scanning tunneling microscopy in air: A new method for producing structures with high aspect ratios

A new lithography method for patterning an electron-beam resist employed in microelectronic technology with low energetic electrons from a scanning tunneling microscopy tip is presented. The method utilizes a thin electron-sensitive, chemically amplified top resist (positive mode) and amorphous diamondlike carbon as conductive bottom resist which allows one (in contrast to other scanning probe microscopy techniques) to achieve aspect ratios larger than five. The exposure response curve of the employed top resist is presented and compared with high-energy e-beam results. It is shown that the exposure with low-energy electrons leads to a direct cleavage of the functional group of the resist polymer responsible for development. Furthermore, the achievable writing speed for scanning tunneling microscopy exposure is estimated. The successful application of the scanning-tunneling-microscopy-based lithography is demonstrated especially with respect to the high aspect ratio on various substrates (Al, Si, SiO2, and poly Si). (C) 1996 American Vacuum Society.