Mechanistic understanding of the stress-induced failure of Si_3N_4 Metal-Insulator-Metal Capacitors

摘要

The failure of Si_3N_4 metal-insulator-metal (MIM) capacitors fabricated by plasma enhanced chemical vapor deposition (PECVD) was investigated using cross-sectional transmission electron microscopy (XTEM) and residual stress analysis. As a result we noted that the failure of the Si_3N_4 MIM capacitors originated from the microvoids formed over the Si_3N_4 dielectric and the TiN interlayer. The microvoid of the MIM capacitor, particularly in case of having a very thin Si_3N_4 of less than 50 nm-thick, caused it to leak out much of the current to the extent of a few microamperes even at bias of 3 volts. The formation of microvoids was explained by the residual stress of the constituent layers at a mechanistic point of view. The stress analysis showed that the absolute stress normalized by the thickness of the Si_3N_4 layer should be less than 31 MPam to avoid microvoiding. In this research it was noted in conclusion that the stress state of not only the dielectric but also the interlayer should be taken into account for the successful design of high capacitive Si_3N_4 MIM capacitors.