Plasma sheath modelling to predict etch-induced overlay

Abstract

In this work a two-dimensional, axisymmetric plasma sheath model is presented that is used to predict ion trajectory deviations in the plasma-wafer interface for a given set of physical etch conditions and chamber geometries. The model successfully predicts the plasma sheath deformation and the associated ion tilt in the vicinity of the wafer edge due to electrical discontinuities. We couple the predictive power of the plasma sheath model with a feature-scale kinetic Monte Carlo etch model to determine the asymmetries in post-etched structures and hence on-product overlay. The feature-scale model serves as a tool to translate the ion tilt within plasma sheath to the sidewall angle asymmetries in the etched trenches and the resulting overlay errors in two adjacent layers of a semiconductor device that could ultimately affect the device yield.

Role of gas composition in weakened nonlinear standing wave excitation and improved plasma radial uniformity in very-high-frequency asymmetric capacitive Ar/CF4 discharges

“…Since the computational domain of the sheath model is much larger than s, the boundary conditions at the other side are set as follows: n sh,+i equals to n +i in the bulk plasma, u sh,+i is set to the ion mean thermal velocity u +i,th , and ϕ sh is set to zero. In this work, the plasma-sheath boundary is determined as the location where the electron density starts deviating from the ion density, as described in [48,49].…”

Science-based, data-driven developments in plasma processing for material synthesis and device-integration technologies

“…[133][134][135] The 2D axisymmetric plasma sheath model predicted ion trajectory deviations at the plasma-wafer interface for actual chamber geometries and etch conditions. 136) The plasma sheath was deformed, and the ion trajectories tilted from the normal to the surface in the vicinity of the wafer edge. The feature-scale kinetic MC etch model determines the asymmetries in the postetched feature profiles.…”

Assessing neutral transport mechanisms in aspect ratio dependent etching by means of experiments and multiscale plasma modeling

“…It is an important metric in semiconductor fabrication, as a poor overlay could result in open contacts or unintended shorts between adjacent layers, thereby severely affecting the device yield [1,2]. The contribution of ions to etch-induced asymmetries was investigated in one of our earlier publications [3]. The present work will focus on the contribution of neutrals, with special attention to microloading and aspect ratio dependent etching (ARDE).…”