Fabrication of open stencil masks with asymmetric void ratio for the ion projection lithography space charge experiment

For the ion projection lithography space charge experiment [P.W.H. de Jager et al., J. Vac. Sci. Technol. B 17, 3098 (1999)] a suitable stencil test m ask has been realized and used. This article addresses the stress engineeri ng and fabrication process of this specific lest mask with openings in the range of some few 100 nm up to some 100 mum. This large difference in stenc il pattern dimensions causes reactive ion etching (RIE) lag (dependence of the etch rate on feature size and pattern density) during the fabrication p rocess and considerable stress variations across the membrane field. The so lution to these problems was by (i) implementing novel doping technologies to create variable thickness areas on the membrane serving as reinforcement and stress relief Structures, and (ii) adjusting the design to feature siz es and pattern densities to the same order of magnitude for the e-beam lith ography and RIE processing steps. The etching of the openings through the 3 mum thick Si membrane was done by inductively coupled plasma etching with gas chopping techniques. These methods as developed for this specific test mask can be used to improve the stencil mask technology in general. (C) 200 0 American Vacuum Society. [S0734-211X(00)06706-8].