Nanoimprint lithography enables memristor crossbars and hybrid circuits

Memristive devices are promising building blocks for enhanced CMOS hardware in data storage and computing. Nanoimprint lithography (NIL) has been an enabling technology in the past decade for exploring novel devices and circuits. In this paper, the authors review the progress and technical aspects of the fabrication and integration of memristor crossbar arrays using NIL. Since the key component of successful fabrication is the imprint mold, the material selection, master mold fabrication, anti-sticking treatment and cleaning are first discussed. The requirements and composition of imprint resists, in particular low-viscosity liquid resists that cross-link upon ultraviolet light radiation, are investigated next. After the description of imprint systems and alignment mechanisms, a disruptive self-alignment fabrication scheme for crossbar arrays is presented. Finally, the first implementation of a memristor/CMOS hybrid circuit using NIL on foundry-made CMOS substrates, together with more recent developments, is recounted. The challenges and possible solutions for NIL as a primary tool for crossbar fabrication are also proposed and discussed.