DUV LITHOGRAPHY FOR 0.35-MU-M CMOS PROCESSING

The performance of positive and negative tone resists on the critical levels of a 0.35 mum CMOS process has been evaluated. The use of a dar kfield reticle suppresses reflections in lens and resist. Therefore re flection problems are reduced for poly gate patterning with a negative tone resist. If a positive resist is used it should be combined with a bottom ARC. For the contact hole level a positive tone resist is req uired. Good performance, including batch uniformity is obtained for 0. 5 mum holes. For 0.4 mum contact holes, latitudes needed to be improve d and this has been realised by either the combination of mask biasing and focus drilling or the use of an attenuated phase shifting reticle . For metal patterning, again positive and negative resists have been studied. An important issue here is the interaction between the acid f ormed upon exposure and the underlying TiN layer.