Recovery of atom density drift caused by change in reactor wall conditions by real-time autonomous control

In plasma etching processes, temporal changes in atom densities need to be avoided since the ratio of atom densities is known to directly determine feature profiles. For H₂ and N₂ mixture plasmas, temporal changes in H and N atom densities are affected by chamber wall conditions, particularly after air exposure. Here we demonstrate that a new feedback control system recently developed by us could autonomously recover atom densities to the intended values in real time, on the basis of vacuum ultraviolet absorption spectroscopy measurements. Real-time process control is thus crucially achieved to suppress fluctuations in feature profiles due to plasma etching. (fast track communication)