DIRECT WRITE PATTERN PLACEMENT ACCURACY FOR E-BEAM NANOLITHOGRAPHY

The pattern placement accuracy (PPA) is an important parameter in e-beam ''direct write'' for nanoelectronic applications. With a LEICA EBPG 4 HR, the influence of different mark/substrate combinations and of several writing parameters on the TPA was investigated. The obtainable ''direct write'' overlay accuracy was 45 nm (I mean I + 3 sigma) for gold marks on a silicon wafer. Taking into account VLSI design rules, this value does not allow to scoop the EBPG 4 HR's resolution of 30 nm. However, splitting up the total ''direct write'' overlay error in single contributions, e.g. reproducibility of mark detection, electron beam drift, alignment errors and temperature stability, there is only a small margin for improvements. New methods in chip design, pattern alignment and chip processing seem to be necessary to manufacture electronic devices on the nanometer scale.