Multilayer reticle heating impact on product overlay

With the continuous resolution shrinking in cutting edge semiconductor industry such as memory device, on product overlay (OPO) control has become more and more challenging. Reticle heating is a critical impact to OPO when DUV light exposes to the reticle, as the thermal expansion of the reticle induces nanos of overlay error on wafer level which directly impacts device function. Reticle heating control functions has been developed to compensate overlay error in current advanced scanners for normal full reticle, of which one layer mask occupies one reticle. However, the heating effect of Multilayer Reticle (MLR), wherein one reticle consists of multiple mask layers, is less discussed. In this paper, we investigated the reticle heating effect to OPO on MLR, and the methods for MLR heating control is proposed.