Design space for low sensitivity to size variations in [110] PMOS nanowire devices: The implications of anisotropy in the quantization mass

TL;DR

This study investigates how size variations affect the ON-current in [110] PMOS nanowire devices, revealing anisotropic behaviors and design strategies to minimize sensitivity, with implications for device manufacturing and strain engineering.

Contribution

It introduces a detailed atomistic and semi-classical modeling approach to analyze size sensitivity in nanowires, highlighting anisotropic effects and design regions for stable ON-current performance.

Findings

Width variations have minor impact on ON-current in certain design regions.

Height variations significantly affect ON-current, especially near volume-to-surface inversion transition.

Strain engineering can mitigate size sensitivity effects.

Abstract

A 20-band sp3d5s* spin-orbit-coupled, semi-empirical, atomistic tight-binding model is used with a semi-classical, ballistic, field-effect-transistor (FET) model, to examine the ON-current variations to size variations of [110] oriented PMOS nanowire devices. Infinitely long, uniform, rectangular nanowires of side dimensions from 3nm to 12nm are examined and significantly different behavior in width vs. height variations are identified and explained. Design regions are identified, which show minor ON-current variations to significant width variations that might occur due to lack of line width control. Regions which show large ON-current variations to small height variations are also identified. The considerations of the full band model here show that ON-current doubling can be observed in the ON-state at the onset of volume inversion to surface inversion transport caused by structural side size variations. Strain engineering can smooth out or tune such sensitivities to size variations. The cause of variations described is the structural quantization behavior of the nanowires, which provide an additional variation mechanism to any other ON-current variations such as surface roughness, phonon scattering etc.