Correlation between silicon‐nitride film stress and composition: XPS and SIMS analyses

Abstract

AbstractThe characteristics of silicon‐nitride films deposited with plasma‐enhanced chemical vapour deposition (PECVD) can vary not only in composition, but also in terms of physical properties. An important parameter in the fabrication of micro‐electro‐mechanical systems (MEMS) devices is the control and tailoring of the film stress. In fact, silicon‐nitride film stress can vary from tensile (up to 800 MPa) to compressive (−500 MPa), depending on the PECVD deposition conditions (e.g. plasma pressure, plasma frequency and power).In this work, we have investigated the role of frequency mixing on the resulting film structure and stress. The layers were prepared with a commercial PECVD deposition chamber, keeping all deposition parameters constant except the ratio between low (380 kHz) and high (13.56 MHz) frequency. Film stress values were compared with compositional and chemical data from X‐ray photoemission spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) measurements. These two techniques are complementary.The comparison between quantified SIMS depth profiles and the XPS HF etch‐back method shows a good agreement in nitrogen profile behaviour. In addition, XPS analyses have provided a suitable chemical characterisation of the different growth processes.We demonstrate that this analytical approach is really effective for the physico‐chemical characterisation of PECVD grown silicon nitride. Copyright © 2006 John Wiley & Sons, Ltd.