Stress modulation in silicon nitride layers grown by plasma-enhanced chemical vapor deposition

Abstract

In this work, plasma-enhanced chemical vapor deposition (PECVD) silicon nitride (SiN_x) layers deposited at up to 600 °C are investigated in terms of the influence of different deposition parameters on the mechanical stress. Elastic recoil detection analysis (ERDA) is used to determine the absolute elemental concentration distribution and Fourier-transform infrared spectroscopy (FTIR) is used to identify the bonding configuration between the different elements. The combination of ERDA and FTIR analyses provides an understanding of the nitrogen- and hydrogen-induced influence on film stress of the SiN_x layers. Increased temperature and the use of a low frequency excitation result in a higher nitrogen (N) and a lower hydrogen (H) content. This also correlates with changes in the stress of the films. Higher nitrogen and lower hydrogen values are associated with increased compressive stress. The FTIR analyses display absorption bands that indicate Si-N, Si-H and NH bonds. Although both the increase in the Si-N absorption band peak and the decrease in the Si-H peak are associated with greater compressive stress, the measurements indicate that Si-N has the largest influence on the stress. These results illustrate the role of nitrogen in modulating the stress properties of PECVD SiN_x layers providing an understanding for optimized deposition parameters to achieve desired stress characteristics.