| Popis: |
As the dimensions of devices shrink and the processing of new devices gets more complex, the requirements for overlay are becoming tighter. Many process elements and previously unmodeled components now dominate the total overlay budget; such as reticle error, alignment-mark quality and design, tool control, alignment system setup and alignment sampling layout, etc. Unmodeled errors (RMSE) consume a larger percentage of the total overlay as the tolerances become tighter. The strategy pursued was to reduce the contribution of each of these elements to as small as possible. In this paper, an improved sampling method is introduced to optimize the sampling layouts in order to minimize RMSE in alignment modeling solutions. The applications of these optimized sampling layouts in both production and system maintenance are also introduced. |
