A negative capacitance field effect transistor with a modified gate stack and drain-side cavity for label-free biosensing

Abstract

Dielectrically modulated (DM) Negative Capacitance Field Effect Transistor (NCFET) based label-free Biosensors have emerged as promising devices for accurate detection of various biomolecules, where the sensitivity of DM architectures strongly depends on the sensing mechanism as well as on the size of the nano-cavity. Therefore, to achieve higher sensitivity along with reduced fabrication complexity, we propose to utilize a pre-existing drain-sided spacer region as a nano-cavity, in a Fully Depleted Silicon-on-insulator (FDSOI) based NCFET architecture. The Ferroelectric (FE) layer in the Metal-Ferroelectric-Insulator-Semiconductor (MFIS) configuration meaningfully alters the impact of drain's electric field on the source-sided electrostatics, which results in higher sensitivity. Having quantified the sensitivity for an FE-DE gate stack based NCFET Biosensor, we now propose to include a Paraelectric (PE) layer between Ferroelectric (FE) and Dielectric (DE) materials, thus modifying the gate stack from FE-DE to FE-PE-DE with an equivalent negative capacitance seen from both the stacks, where a remarkable improvement is seen in the FE-PE-DE gate stack based NCFET with nearly identical linearity performance as seen from the high value of Pearson's coefficient (r2 ≥ 0.9). Therefore, in order to illustrate the efficacy of the proposed sensing mechanism and the modified gate stack (FE-PE-DE), dielectric constant (kBio) values in the range of kBio = 4.5 to kBio = 75.99 are considered. Finally, the effect of scaling the channel length (Lg) on the sensitivity of the FE-PE-DE NCFET device is shown and a high value, particularly at lower permittivity, demonstrates the versatility and wide applicability of the proposed NCFET Biosensor.