Crossbar Production

Abstract

Preparing externally accessible arrangements of structures not producible by lithography, because of either technical reasons (below the lithographic limit) or economic reasons (excessive cost of advanced lithography). As already discussed, the dramatic explosion of the cost required to sustain the reduction of the feature size (Fig. 2.6) has given rise to doubts on the possibility of continuing the current increase of density [by a factor of 2 each 18 months (24 months) for memories (microprocessors)] beyond the next decade. Hence the interest in the development of alternative lithographic methods or of nonlithographic patterning technologies for the definition of geometries on the nanometer length scale. The crossbar structure has the potential to overcome the limits of conventional DUV, EUV, and EB lithographies because of the following reasons. The fabrication of crosspoints does not require any alignment,¹ being the selfaligned result of two subsequent definitions. The geometries of interest (usually parallel lines; see however Sect. 6.2) may be produced without any advanced lithography.