In-line focus-dose monitoring for hyper NA imaging

The merits of hyper NA imaging using 193nm exposure wavelength with water immersion for 45nm is clear. Scanner focus and dose control is always improving to allow small DOF manufacturing in immersion lithography. However, other process parameters can affect focus and dose control and a real-time monitor capability to detect local focus and exposure conditions on production wafers is required. In this paper we evaluated a focus-exposure monitor technique based on Spectroscopic Critical Dimension (SCD) metrology following the promising results obtained by Kelvin Hung [1] et al. The key attributes of this technique are the implementation on standard production wafers, the high sensitivity to pattern profile modifications and the unique capability of spectroscopic ellipsometry to provide all the information needed to decouple the effects on pattern formation coming from process variations of Advanced Patterning Films (APF) [2], largely adopted for 65/45nm patterning, from coating and, finally, from the pure scanner imaging contributors like focus and exposure. We will present the characterization of this technique for 2 critical layers: active and contacts of a non-volatile memory device, 45nm technology.