The Role of Quantization Effects on the Operation of 50 nm MOSFETs, 250 nm FIBMOS Devices and Narrow-Width SOI Device Structures

We investigate the role of the quantum-mechanical space-quantization effects on the operation of a 50 nm MOSFET device, an asymmetric 250 nm FIBMOS device and a narrow-width SOI device structure. We find that space-quantization effects give rise to larger average displacement of the carriers from the interface proper and lower sheet electron density in both the regular and the asymmetric MOSFET device structures. The effect is even more pronounced in the narrow-width SOI device due to the presence of a two-dimensional confinement (both vertical and along the width direction). The reduction in the sheet electron density, in turn, gives rise to shift in the devices threshold voltage, on the order of 100–200 mV, depending upon the device structure being investigated. This leads to 20–40% decrease of the device on-state current which depends upon the gate bias. Hence, to properly describe the operation of future ultra-small devices it is mandatory to incorporate quantummechanical space quantization effects into existing classical device simulators (drift-diffusion, hydrodynamics or Monte Carlo particle-based simulators) since first-principle quantum-mechanical calculations (direct solution of the many-body Schrödinger equation, Green’s functions method, etc.) are still limited to one-dimensional structures and rely on a number of approximations.