On the road to insertion of extreme ultraviolet (EUV) lithography into production at the 16 nm technology node and below, we are testing its integration into standard semiconductor process flows for 22 nm node devices.In this paper, we describe the patterning of two levels of a 22 nm node test chip using single-exposure EUV lithography; the other layers of the test chip were patterned using 193 nm immersion lithography. We designed a full-field EUV mask for contact and first interconnect levels using rule-based corrections to compensate for the EUV specific effects of mask shadowing and imaging system flare. The resulting mask and the 0.25-NA EUV scanner utilized for the EUV lithography steps were found to provide more than adequate patterning performance for the 22 nm node devices. The CD uniformity across the exposure field and through a lot of wafers was approximately 6.1% (3σ) and the measured overlay on a representative test chip wafer was 13.0 nm (x) and 12.2 nm (y). A trilayer resist process that provided ample process latitude and sufficient etch selectivity for pattern transfer was utilized to pattern the contact and first interconnect levels. The etch recipes provided good CD control, profiles and end-point discrimination.The patterned integration wafers have been processed through metal deposition and polish at the contact level and are now being patterned at the first interconnect level.

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Various issues related to non-telecentric mask effects for EUV lithography will be discussed in this paper. First, a raytracing approach will provide a conceptual description as to the nature of non-telecentric thick mask effects, highlighting the behavior of various edge types and corners. Rigorous modeling of these effects are discussed along with a few consequences of improper modeling. A series of simulation and experimental studies are presented to probe both the one-and two-dimensional impact of thick mask effects. It will be shown that a simple constant edge bias appears sufficient for 1D features, but begins to break down when space-widths are less than about 45 nm. Investigation into the impact of corners and small 2D features indicates that a simple edge-based bias also breaks down for edge lengths less than about 60nm. A sample set of rules-based post-OPC HV corrections for 22nm node dimensions are proposed, although based on experimental results, it is concluded that more accurate resist modeling and scanner stability are required before being able to precisely predict and control HV effects. Finally, with some simplifying assumptions, simulation is used to predict the extent of potential HV effects of future EUV imaging systems.

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