Study of Mask Proximity Impact on Mask Mean-to-Target Specification

概要

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An analytic relationship of the mask mean-to-target (MTT) and the mask uniformity specifications affected by the mask proximity effect (MPE) is suggested. MPE mainly caused by e-beam proximity and the etch loading effect makes different MTTs for patterns with different pitch sizes. $\Gamma$ is the parameter introduced to represent MTT differences induced by MPE. The mask MTT and uniformity ($M$–$U$) curves which define the boundary of the specification region shift along the mask MTT axis according to the sign of $\Gamma$. The mask $M$–$U$ curves translate upward for a positive $\Gamma$ and downward for a negative $\Gamma$. $M$–$U$ specifications are calculated for 45 and 51 nm half-pitch sizes. $\Gamma$’s are obtained from the experimental proximity curve and they are $-0.5$ and $-0.8$ nm for the 45 and 51 nm nodes, respectively. For the 45 nm node, the lower and upper mask MTT specifications are $-5.35$ and 3.91 nm, respectively. For the 51 nm node, the lower and upper MTT specifications are $-9.00$ and 3.90 nm, respectively. $M$–$U$ curves are shown to be translated downward for negative $\Gamma$’s and their amounts are $-2.55$ and $-0.72$ nm for the 45 and 51 nm nodes, respectively.
2007-12-15