Reliability and electric properties for PECVD a-SiNx:H films with an optical band-gap ranging from 2.5 to 5.38 eV

The reliability and electrical properties for PECVD a-SiN_x:H films with an optical band-gap ranging from 2.5 to 5.38 eV have been investigated. The observed changes in the electrical characteristics are reviewed in terms of changes in the chemical and physical behaviour of the metastable Si dangling bonds. We found evidence that the degradation mechanism for our films is similar to that of a-SiN_x:H with a band-gap < 2.4 eV. In addition, we propose that, on prolonged stress, the bonds needed in the process of metastability can become exhausted for Si-rich and N-rich materials. For intermediate materials (x∼1.2), exhaustion is also expected but not observed within the time scale of our experiments. Finally, it has been shown that TDDB can be used to describe the reliability for PECVD a-SiN_x:H films whereas QBD fails to do so. The a-SiN_x:H films with x > 1.2 were all shown to fulfil both the lifetime and leakage current requirements for application in passive RF networks.