Presented at SPIE Advanced Lithography 2009

As immersion lithography extends into the 32nm node through the use of double patterning techniques, the requirements for overlay, CDU and focus also become tighter. In the 2006 SPIE conference Rudolph Technologies (August Technology) presented a poster which proved that backside particles < 5μm did not cause enough wafer deflection to create focus problems during exposure for the 65nm node. During that same time period, there were other studies that looked at the cause and effect of backside particles on wafer deflection.