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

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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 ($d_{\text{R}}$) and residual (areal) defect density after wet-etch treatment ($N_{\text{dam}}$), are calculated on the basis of a modified range theory, and the trade-off relationship between $d_{\text{R}}$ and $N_{\text{dam}}$ is presented. We also model their effects on device parameters such as off-state leakage ($I_{\text{off}}$) and drain saturation current ($I_{\text{on}}$) 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), $d_{\text{R}}$, $N_{\text{dam}}$, $I_{\text{off}}$, and $I_{\text{on}}$. Then we propose a methodology optimizing ion energy and ion flux under the constraints defined by device specifications $I_{\text{off}}$ and $I_{\text{on}}$, via $d_{\text{R}}$ and $N_{\text{dam}}$. 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.
2011-08-25