Optical lithography is still the preferred technology for semiconductor volume production. The wavelength reduction cannot keep up with the pace of decreasing feature sizes. As a result, printing occurs closer and closer to the resolution limit of the projection tools, inducing severe proximity effects. In this paper, an overview of three automated optical proximity correction packages is given. Correction accuracy as well as mask making feasibility are touched upon. An attempt is made to predict the need for OPC in the optical lithography roadmap. It is expected that OPC will be needed to push the 248 nm lithography down to 0.18 micrometer, while it can then further be used to push 193 nm lithography down to 0.13 micrometer.
In this paper, the results of an NA-sigma optimization study are reported, carried out experimentally for an advanced ASML PAS5500/300 deep-UV stepper. The work has been primarily focused on a 0.25 and sub-0.25 micrometers gate layer in a logic CMOS process. A positive and negative tone resist process have been compared in terms of CD control and line- end shortening. Dry etch effects and across-field behavior has been taken into account. Furthermore the contact level of the 0.25 micrometers process have been optimized. Effects of layer dependent NA-sigma settings on overlay have been studied.