In‐situestimation of MOCVD growth rate via a modified Kalman filter

Abstract

In‐situ laser reflectance monitoring of metal‐organic chemical vapor deposition (MOCVD) is an effective way to monitor growth rate and expitaxial layer thickness of a variety of III–V and II–VI semiconductors. Materials with low optical extinction coefficients, such as ZnTe/GaAs and AlAs/GaAs for a 6328 Å HeNe laser, are ideal for such an application. An Extended Kalman filter modified to include a variable forgetting factor was applied to the MOCVD systems. The filter was able to accurately estimate thickness and growth rate while filtering out process noise and cope with sudden changes in growth rate, reflectance drift, and bias. Due to the forgetting factor, the Kalman filter was successful, even when based on very simple process models.

Moving horizon estimation for in situ monitoring of chemical vapor deposition process

“…To robustly extract maximum information from the in situ reflectometer data, a statistical analysis would be advantageous. To address these problems some researchers used the extended Kalman filter to interpret the measurements [7], [8], [9]. A Kalman filter is an optimal state estimator applied to a linear dynamic system.…”

An extended Kalman filter for in situ sensing of yttria-stabilized zirconia in chemical vapor deposition

“…An early application of Kalman filtering to in-situ monitoring of a deposition process appeared in 1984 [33]. Later Woo and his coworkers applied a modified Kalman filter to estimate film thickness and growth rate from a laser reflectance measurement [34]. EKF was also used to estimate etch rate and end-point in a plasma etch system by Vincent and Khargonekar [12], [35].…”