The utilization of EUV pellicles as protective layers for EUV masks requires the use of refractory materials that can tolerate large temperature excursions due to the non-negligible absorption of EUV radiation during exposure. Additionally, the mechanical stress induced on the EUV pellicle by the thermal load is dependent on the thermal expansion of the material which can be responsible for transient wrinkling. In this study, an ultrathin (20 nm), free-standing membrane based on silicon nitride is utilized as a learning vehicle to understand the material requirements of EUV pellicles under dynamic exposure conditions that are typical of commercial EUV scanners. First, the nanoscale radiative properties (emissivity) and thermo-mechanical failure temperature of the dielectric film under vacuum conditions are experimentally investigated utilizing a pulsed ArF (193 nm) probing laser. The silicon nitride membrane is found to be marginally compatible with an equivalent 80W EUV source power under steady state illumination conditions. Next, the thermal behavior of the EUV pellicle under dynamic exposure conditions is simulated using a finite element solver. The transient temperature profile and stress distribution across the membrane under stationary state conditions are extracted for an equivalent 60W EUV power source and the pellicle wrinkling due to heating and consequent impact on CD uniformity is estimated. The present work provides a generalized methodology to anticipate the thermal response of a EUV pellicle under realistic exposure conditions.
We have created a finite-element based, multiple-material,
levelset-based code to implicitly represent and track evolving
islands and grains. With this method, the code can track island
growth in three dimensions through nucleation to coalescence into a
grain structure. We discuss the numerical methods, capabilities,
and limitations of the code, and then examine the microstructures
that result from different models of growth based on starting
structures derived from atomistic Monte Carlo simulations. We show
simulation results from a kinetically limited process (electroless
deposition), a transport-limited process (physical vapor
deposition), and a process neither transport nor kinetically
limited (physical vapor deposition with orientation
dependent sticking factors).