Abstract
Miniaturizing Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) to the nanoscale results in specific structure and performance effects known as Short Channel Effects (SCEs). Performance degradation due to SCEs occurs due to increased leakage currents (IOFF), decreased threshold voltage (VTH) stability and breakdown voltage. Various solutions for these problems have been developed through the application of structural and material engineering techniques. One particular engineering technique that shows promise as a potential solution is to incorporate a Selective Buried Oxide Layer (SELBOX). In this article, we investigate how the introduction of a SELBOX impacts the electrical characteristics of nano-scale n-MOSFETs through device simulation (TCAD). For the purposes of this study, we developed a 20 nm n-MOSFET with a high-k HfO₂ gate dielectric using the TCAD Silvaco ATLAS software package. Three different types of SiO₂, Al₂O₃, and HfO₂ dielectric materials were used in conjunction with the SELBOX layer which is located at a depth of 30 nm from the drain. In addition, the location of the SELBOX as related to the drain was also varied from its original position to the direct vicinity of the channel to assess the overall effect of the SELBOX position. Finally, we compare the characteristics of a conventional-type MOSFET (no SELBOX) to those of devices modified by inclusion of the SELBOX at varying positions/depths from the drain. The findings indicate that the dielectric constant and band gap of the implanted material, as well as its closeness to the drain and channel region, substantially influence device performance. In the instance of SiO₂ as SELBOX material, the IOFF decreased by 33%, and the breakdown voltage significantly increased from 85.09 V to 491.4 V. The utilization of Al₂O₃ resulted in a 27% reduction in IOFF and an increase in breakdown voltage from 85.09 V to 275.7 V. Notably, the application of HfO₂ as SELBOX material resulted in a divergent effect: IOFF rose by 21%, but the breakdown voltage increased to 172.3 V.
Keywords
Al2O3; HfO2; n-MOSFET; SELBOX; Silvaco ATLAS; Breakdown Voltage.