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In the ITRS roadmap [1] increasingly long mask write and cycle time is explicitly addressed as a difficult challenge in
mask fabrication for the 16nm technology node and beyond. Write time reduction demands have to be seen in relation to
corresponding performance parameters like Line Width Roughness (LWR), resolution, placement as well as CD
Uniformity. The previously presented Multi Shaped Beam (MSB) approach [2, 3] is considered a potential solution for high
throughput mask write application. In order to fully adapt the MSB concept to future industry's requirements specific
optimizations are planned.
The key element for achieving write time reduction is a higher probe current at the target, which can be obtained by
increasing the number of beamlets as well as applying a higher current density. In the present paper the approach of a
256 beamlet MSB design will be discussed. For a given image field size along with a beamlet number increase both
beamlet pitch and size have to be optimized.
Out of previous investigations, one finding was that by changing the demagnification after the beam forming section of
the MSB column the overall performance can be optimized. Based on first electron-optical simulations for a new final
lens a larger demagnification turned out to be advantageous.
Stochastic beam blur simulation results for the MSB reduction optics will be presented. During the exposure of a pattern
layout the number of used beams, their shape and their distribution within the image field varies, which can lead to space
charge distortion effects. In regard to this MSB simulation results obtained for an image field of approximately
10x10ìm² will be presented.
For the 256 beamlet MSB design and resist sensitivities of 20μC/cm2, 40μC/cm2 and 100μC/cm2 write time and LWR simulations have been performed. For MSB pattern data fracturing an optimized algorithm has been used, which
increased the beamlet utilization factor (indicates the mean number of beamlets which are used per multi-shot). Finally
an update with regard to the required changes of the data path architecture for the 256 beamlet MSB approach will be
given. Data integrity as an important aspect of the production worthiness of such a systems will be discussed specifically.
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