Wafer-Scale Nanoimprint Lithography Process Towards Complementary Silicon Nanowire Field-Effect Transistors for Biosensor Applications

The authors present a combined, p- and n-type fabrication process for silicon nanowire field-effect transistor (SiNW FET) biosensors on a 4” wafer format with nanowire widths down to 100 nm and a height of only 42 nm. The full wafer design includes various SiNW FET combinations with metal or electrolyte gate contacts. A top-down fabrication protocol on high-quality silicon-on-insulator wafers is developed. Down-thinning of Si is done by a modified CMOS cleaning solution, which gives the possibility to control the resulting thickness with sub-nm precision. The structuring of SiNW FETs is realized by nanoimprint lithography (NIL) applying a special temperature/pressure profile. The authors fabricate nano-scale sensor structures and micro-scale contact lines in the same NIL step. Precise control of the imprinting procedure is important for complete filling of the structures. In this project, the authors aim towards complementary device combinations and therefore they characterize the threshold voltage dependency on the device structures. Back-gate contacts at the front-side of the chips enable a control of surface potential shifts. The new SiNW FET sensors can be utilized for biomedical applications, where they are operated in a liquid environment under double-gate configuration using parallel front gating and back gating.