ADVANCED I-LINE LITHOGRAPHY - PROCESSES FOR POSITIVE AND NEGATIVE PATTERNING USING THE SAME ACID HARDENING RESIST

In this paper, we propose two sub 0.5 mum i-line processes (0.40 NA st epper), for negative and positive patterning, using the same acid hard ening resist: the negative patterning is achieved via wet development and the positive patterning via silylation and dry development. We fir st considere the wet development negative process. Such a negative pro cess is strategic for many lithographic levels, and we here demonstrat e its application for sub 0.5 mum gates fabrication [the level of IC f abrication requiring the highest resolution]. The lithographic results obtained over flat and topographic polysilicon wafers are presented a nd discussed in terms of exposure dose and focus latitudes. The plasma etching behavior of the resist is then studied and discussed as a fun ction of the gas chemistry: the best conditions are finally used for t ransfering the patterns into a 0.38 mum thick polysilicon layer. In th e second part of this paper, we demonstrate a positive dry development process using vapor silylation; different silylation conditions and d evelopment modes are evaluated. Such a process could be used where reg ular wet development processes reach their limits, or where a positive process is better adapted to the geometry of the level in fabrication ; only one resist would then be necessary for both polarities.