Trade-Off Relationship between Si Recess and Defect Density Formed by Plasma-Induced Damage in Planar Metal–Oxide–Semiconductor Field-Effect Transistors and the Optimization Methodology

Abstract

Physical damage induced by high-energy ion bombardment during plasma processing is characterized from the viewpoint of the relationship between surface-damaged layer (silicon loss) and defect site underneath the surface. Parameters for plasma-induced damage (PID), Si recess depth (dR) and residual (areal) defect density after wet-etch treatment (Ndam), are calculated on the basis of a modified range theory, and the trade-off relationship between dR and Ndam is presented. We also model their effects on device parameters such as off-state leakage (Ioff) and drain saturation current (Ion) of n-channel metal–oxide–semiconductor field effect transistors (MOSFETs). Based on the models, we clarify the relationship among plasma process parameters (ion energy and ion flux), dR, Ndam, Ioff, and Ion. Then we propose a methodology optimizing ion energy and ion flux under the constraints defined by device specifications Ioff and Ion, via dR and Ndam. This procedure is regarded as so-called optimization problems. The proposed methodology is applicable to optimizing plasma parameters that minimize degradation of MOSFET performance by PID.