Demand for mask process correction (MPC) is growing for leading-edge process nodes. MPC was originally intended to
correct CD linearity for narrow assist features difficult to resolve on a photomask without any correction, but it has been
extended to main features as process nodes have been shrinking.
As past papers have observed, MPC shows improvements in photomask fidelity. Using advanced shape and dose
corrections could give more improvements, especially at line-ends and corners. However, there is a dilemma on using
such advanced corrections on full mask level because it increases data volume and run time. In addition, write time on
variable shaped beam (VSB) writers also increases as the number of shots increases.
Optical proximity correction (OPC) care-area defines circuit design locations that require high mask fidelity under mask
writing process variations such as energy fluctuation. It is useful for MPC to switch its correction strategy and permit the
use of advanced mask correction techniques in those local care-areas where they provide maximum wafer benefits. The
use of mask correction techniques tailored to localized post-OPC design can result in similar desired level of data
volume, run time, and write time. ASML Brion and NCS have jointly developed a method to feedforward the care-area
information from Tachyon LMC to NDE-MPC to provide real benefit for improving both mask writing and wafer
This paper explains the detail of OPC care-area feedforwarding to MPC between ASML Brion and NCS, and shows the
results. In addition, improvements on mask and wafer simulations are also shown. The results indicate that the worst
process variation (PV) bands are reduced up to 37% for a 10nm tech node metal case.