In-situ and Non-contact Etch Depth Prediction in Plasma Etching via Machine Learning (ANN & BNN) and Digital Image Colorimetry
Journal:
arXiv
Published Date:
May 3, 2025
Abstract
Precise monitoring of etch depth and the thickness of insulating materials,
such as Silicon dioxide and silicon nitride, is critical to ensuring device
performance and yield in semiconductor manufacturing. While conventional
ex-situ analysis methods are accurate, they are constrained by time delays and
contamination risks. To address these limitations, this study proposes a
non-contact, in-situ etch depth prediction framework based on machine learning
(ML) techniques. Two scenarios are explored. In the first scenario, an
artificial neural network (ANN) is trained to predict average etch depth from
process parameters, achieving a significantly lower mean squared error (MSE)
compared to a linear baseline model. The approach is then extended to
incorporate variability from repeated measurements using a Bayesian Neural
Network (BNN) to capture both aleatoric and epistemic uncertainty. Coverage
analysis confirms the BNN's capability to provide reliable uncertainty
estimates. In the second scenario, we demonstrate the feasibility of using RGB
data from digital image colorimetry (DIC) as input for etch depth prediction,
achieving strong performance even in the absence of explicit process
parameters. These results suggest that the integration of DIC and ML offers a
viable, cost-effective alternative for real-time, in-situ, and non-invasive
monitoring in plasma etching processes, contributing to enhanced process
stability, and manufacturing efficiency.
