Intense‐pulsed plasma x‐ray sources for lithography: Mask damage effects

A characteristic of pulsed plasma sources is that each intense x‐ray pulse is of very short time duration, typically ∼1–100 ns. Thermal energy is thus deposited almost instantaneously into the x‐ray mask elements, and since the heat cannot be dissipated in such a short time, the potential exists for damaging the mask. A theoretical analysis has been carried out to examine such mask damage effects and their role in constraining key system parameters (e.g., throughput, resolution). It is shown that the timescale for interpulse cooling by heat conduction in a helium environment is adequate for source repetition rates up to a few hundred pulses per second. Thermal stress‐induced mask failure mechanisms are discussed. Finally, it is concluded that plasma x‐ray sources capable of being repetitively pulsed at rates >1 Hz appear to be promising candidates for high‐resolution, high‐throughput lithography.