Optimized marker definition for high overlay accuracy e-beam lithography

The accurate alignment of different structures on a wafer is of crucial importance for industrial high performance devices as well as for devices probing new physical effects. High level overlay accuracy for e-beam defined patterns in such nanoscaled devices requires sets of markers accurately positioned. In this work the influence of the positioning algorithm for e-beam defined markers on the overlay accuracy is investigated. As markers simple square holes in silicon substrates are used, which are processed with standard reactive ion etching. While in former work the overlay displacement was (18 ± 8) nm, in this work it is shown, that with an optimized marker positioning algorithm overlay displacement of (1.6 ± 2.1) nm can be achieved.

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► Overlay accuracy of a Vistec EBPG5000+ was analyzed.
► Marker definition algorithm was optimized.
► Marker definition with perpendicular incident beam facilitates best overlay.
► Radial displacement of R = (1.6 ± 2.1) nm could be realized.