New alternating phase-shifting mask conversion methodology using phase conflict resolution

A new methodology for completely phase-shifting a layout without creating local phase conflicts is proposed for lithographic techniques combining one phase-shifting mask and one binary mask exposure. Critical and non-critical areas of the layout are identified and phase conflicts are avoided by splitting the shifter regions from non-critical areas to non-critical areas without crossing critical areas. The out-of-phase splits of the shifter regions are removed using the binary exposure. Simulation results and experimental data collected for 90nm technology node show no sign of process latitude loss around the areas where the shifters are split. The overlay latitude is commensurate with 90nm technology scanner requirements (tool to itself). This approach can also be utilized at the cell library level by creating two copies of each cell with forced phase-shifting boundary conditions. The top and bottom of all the cells have the same phase while the left and right side of each cell have opposite phases, in degrees either 0-0 and 180-180 or 0-180 and 180-0. This implementation guarantees conflict-free cell creation and placement.

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