Toward Through-Process Layout Quality Metrics

Quality of a layout has the most direct impact in the manufacturability of a design. Traditionally, layout quality is ensured in the first order by design rules, i.e. if a layout is free of design rules violation, it is a good layout. It is assumed such a layout will be fabricated to specification. Moreover, a design rule clean layout also ensures the electrical performance of the circuit it represents. There are other layout quality measures, e.g. random defects yield of a layout is modeled by critical area, systematic defects yield is sometime measured by a weighted score of recommended design rules. All the traditional layout quality measures are computed with drawn layout shapes. In the advent of low K1 lithography and the increasing variability of process technologies beyond 90nm, nominal layout quality measures need to be revisited. Traditionally, nominal electrical properties such as L-eff and W-eff are extracted from drawn layout, and the corner cases are estimated with worst case process conditions. Most of these parameters are layout pattern dependent. As a matter of fact, they can be systematic through process and can have large impact in the modeling of circuit parameters [1]. In this paper, we investigate a through process layout quality measure, in which we extract through process electrical parameters from simulated through process resist contours. We showed a mechanism to compute a statistical model that predicts through process electrical parameters from the process parameter variation. We demonstrated that such computation is practical. 1