Real-time multivariable control of PECVD silicon nitride film properties

Abstract

This paper reports on the application of quadrupole mass spectrometry (QMS) sensing to real-time multivariable control of film properties in a plasma-enhanced CVD silicon nitride process. Process variables believed to be most important to film deposition are defined (i.e., disilane pressure, triaminosilane pressure, and dc bias voltage) and their responses to system inputs are modeled experimentally. Then, a real-time controller uses this information to manipulate the process variables and hence film performance in real time during film deposition. The relationships between gas concentrations and film performance are shown explicitly where the controller was used to drive the concentrations to constant setpoints. Also, an experiment investigating the effects of an out-of-calibration mass flow controller demonstrates the compensating ability of the real-time controller. The results indicate that in situ sensor-based control using quadrupole mass spectrometry can significantly assist in optimizing film properties, reducing drift during a run, reducing run-to-run drift, creating a better understanding of the process, and making the system tolerant to disturbances.

Monitoring and control of semiconductor manufacturing processes

“…Nevertheless, optical-based sensors (e.g., optical emission spectroscopy (OES) and laser interferometry (LIF), see [15], [26], [27] and references therein) have been invented to measure various chamber-status process variables (or in-situ variables) such as temperature and pressure. This, together with the development of appropriate models that relate in-situ variables to the process metrics, leads to the integrated RtR and real-time control strategy [6], [8], [26], which can be designed in two steps. First, the RtR control uses these models to determine in-situ process variables corresponding to the desired critical wafer parameters.…”

Real-Time Carbon Content Control for PECVD ZrO<tex>$_2$</tex>Thin-Film Growth

“…Recently, a method for real-time control of PECVD silicon nitride film properties for a relatively simple deposition chemistry was proposed in [11]; in this work, thin-film properties were indirectly controlled by regulating gas phase species compositions. At this stage, direct control of PECVD thin film properties has not been reported due to the complexity of both plasma physics and plasma chemistry and the difficulty to obtain real-time measurements of film properties.…”

Shape-based optimal estimation and design of curve evolution processes with application to plasma etching

“…Those that do consider the wafer surface typically consider only planar processes [29], [50]. Earlier work of the first author and co-workers focused on developing techniques for real-time feature-level estimation and control of plasma etching [6]- [8].…”