Benjamin Joseph Fletcher

Optimization of pH sensing using silicon nanowire field effect transistors with HfO2 as the sensing surface

Silicon nanowire field effect transistor sensors with SiO(2)/HfO(2) as the gate dielectric sensing surface are fabricated using a top down approach. These sensors are optimized for pH sensing with two key characteristics. First, the pH sensitivity is shown to be independent of buffer concentration. Second, the observed pH sensitivity is enhanced and is equal to the Nernst maximum sensitivity limit of 59 mV/pH with a corresponding subthreshold drain current change of ∼ 650%/pH. These two enhanced pH sensing characteristics are attributed to the use of HfO(2) as the sensing surface and an optimized fabrication process compatible with silicon processing technology.

Subtractive W contact and local interconnect co-integration (CLIC)

The resistivity of W interconnects deposited by physical vapor deposition (PVD) and chemical vapor deposition (CVD) is studied. The impacts of the deposition process and liner film stacks are explored. The results show acceptable resistivity for local interconnect (LI) applications with a linewidth down to 20nm and a wiring pitch down to 60nm. An integration scheme for combining a CVD W contact and local interconnect is explored as a means of providing a compact wiring solution with minimal impact on process complexity. The wiring concept is validated by integrating the local interconnects with trigate transistors.