Lithographic tradeoffs between different assist feature OPC design strategies

In recent years many of the problems associated with the use of assist features have been partially or completely resolved. Such issues include mask manufacturing and inspection, software maturity, and the so-called forbidden pitch problem. Still, the lithographer is faced with numerous choices in developing production worthy assist feature designs. This paper will examine some of the choices, and the tradeoffs associated with each. In particular the choice between simple one-dimensional scatter bar designs and various two-dimensional designs will be explored to determine the tradeoffs. with lithographic performance. A DRC (Design Rule Check) -driven technique has been developed to highlight potential shortcomings of each individual design strategy. The lithographic impact of these shortcomings has been confirmed with on-Silicon process data.