Aluminum Oxide (Al2O3) is a high k dielectric material with promising biosensor applications. The key feature of the Al2O3 device that allows its stable operation in high salt buffers is the impermeability of the device to mobile buffer ions. Permeation of such mobile buffer ions into traditional silicon-based device results in electrical instability of the device of magnitudes sufficient to interfere with analyte sensing.
This thesis focuses on Al2O3 high k dielectric devices which could work in the physiologic buffer solution (PBS). A low cost Al2O3 MOS capacitor was first fabricated and tested as a tractable model for metal-oxide-semiconductor field effect transistor (MOSFET). The MOS capacitors were dipped in sterile PBS solution for increasing intervals of time starting from 30 mins upto 24 hours. Triangular voltage sweep (TVS) method was used to characterize the Na+ ion penetration. No sodium ion (Na+) penetration was observed for the Al2O3 capacitors. By contrast, the dose of Na+ ion penetration into silicon-dioxide MOS capacitor increased with increasing soak time in the PBS solution. Further, no Na+ ion response was observed for varying Al2O3 thickness of 10nm, 25nm, 50nm, 100nm.
A low cost Si based bioFET with 20nm high-k Al2O3 dielectric deposited by ALD was fabricated and tested in the PBS solution later. After fully functionalizing the surface with aminopropyldimethylethoxysilane (APDMES), the Al2O3 gate dielectric bioFET is capable to work under PBS solution. The drain to source current decreased after detecting the streptavidin. This could be the mobile charge in the channel decreased after binding of the protein. However, the decreased changes are very small and cannot be used as an effective biosensor. To some extent, these changes could be noise because the common source I-V measurements were done in solution which increases lots of unstable factors.