摘要
The imaging behavior of the attenuated phase shifting mask system is studied in terms of the figure of merit of depth of focus for single layer resist, single layer resist with anti reflection coating, and multi-layer resist systems using a ±10% linewidth tolerance and the exposure-defocus window methodology. Significant imaging improvements over conventional intensity masks for contact holes and line openings are identified. A small positive mask bias pushes the improvements towards higher resolution and practical exposure dosages. The imaging performance of contact holes will be compared with that of rim phase shifting masks. The attenuated phase shifting mask produces larger depth of focus, requires lower exposure times, and takes up less mask areas. © 1992.