Sensitivity of Lightly and Heavily Dopped Cylindrical Surrounding Double-Gate (CSDG) MOSFET to Process Variation

Abstract

This research work analyzes the sensitivity of Cylindrical Surrounding Double-Gate (CSDG) MOSFET to process variation using the Poisson equation’s analytical solution. This work has been verified with the numerical simulation. Also, the results obtained have been compared with a multi-gate device known as Cylindrical Surrounding Gate (CSG) MOSFETs. The lightly and heavily doped CSDG MOSFETs have been realized. Their immunity to parameter variation (channel length, Silicon thickness, and Random Dopant Fluctuations (RDFs)) has been compared to CSG MOSFET. This research work indicates that lightly doped CSDG MOSFET exhibits the slightest threshold variations than CSG MOSFETs. It confirms that the lightly doped CSDG MOSFET has better immunity to channel variation than CSG MOSFETs. This is due to its structure and inherent internal and external gate geometry, which offers greater control over the channel. However, RDFs become a dominating factor for heavily doped CSG and CSDG MOSFETs, leading to more dispersion in the threshold variations. Therefore, the CSDG MOSFET’s immunity to channel variation becomes deteriorated due to the larger surface-to-volume ratio. At this point, the CSG MOSFET tends to offer better immunity to process variation. Hence, the sensitivity of threshold voltage to parameter variations depends entirely on the RDFs, as the heavily doped devices are aggressively scaled to the nanometer regime.

Keywords

• Channel length
• cylindrical surrounding double-gate (CSDG) MOSFET
• nanotechnology
• natural length
• scaling pattern
• semiconductors