PATTERNING OF A TI PT/AU METALLIZATION FOR SUBMICRON BIPOLAR-TRANSISTORS MADE BY DIRECT WRITE E-BEAM LITHOGRAPHY/

To fabricate interdigitated bipolar transistors with lateral dimension s well below 1 mum, electron beam lithography and dry etching have bee n implemented in an on optical lithography based production process. T he most demanding step is the patterning of the Ti/Pt/Au metallization layer traditionally used in these devices. Pattern definition by elec tron beam lithography is severely hampered by the proximity effect. Th is problem has been studied in detail and local exposure dose correcti ons are applied to realize well defined resist patterns. The resist pa ttern is transferred to the Au/Pt layers by argon sputter etching. In this work with lateral dimensions smaller than the thickness of the me tal layers the quality of the etch profiles is seriously degraded by r edeposition phenomena. However with a Ti layer patterned by lift-off a s etch mask, gaps with a defined width as small as 0.6 mum have been o pened.