30 December 1999 Transmission and phase balancing of alternating phase-shifting masks (5x): theoretical and experimental results
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Dual trench alternating phase shifting masks with an optimized value of the so-called shallow trench depth represents an interesting approach to overcome aerial image imbalances. In order to get a better understanding of the possibilities and limits of this approach, especially for 5X reduction, theoretical and experimental investigations were accomplished. In this paper experimental data obtained from 5X dual trench type alternating PSMs, using DUV-lithography are introduced and compared with 3D-mask simulations. The masks were fabricated with different etch depths and contain parts of typical DRAM patterns. Besides the transmission balancing also the phase balancing has an important influence on the effective process window of an alternating PSM. The effective phase error can be measured with an AIMS-system (MSM100). The comparison with simulated data allows the determination of the phase error. In a second step the influence of different balancing methods on phase and transmission were investigated with the TEMPEST mask simulator for unpolarized light. The optimization of the balancing with respect to the CD-bias, undercut and etch depth will be shown and a first approach of a sensitivity analysis will be presented.
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Uwe A. Griesinger, Uwe A. Griesinger, Rainer Pforr, Rainer Pforr, Juergen Knobloch, Juergen Knobloch, Christoph M. Friedrich, Christoph M. Friedrich, } "Transmission and phase balancing of alternating phase-shifting masks (5x): theoretical and experimental results", Proc. SPIE 3873, 19th Annual Symposium on Photomask Technology, (30 December 1999); doi: 10.1117/12.373332; https://doi.org/10.1117/12.373332

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