Physico-chemical characterization of polyimide passivation layers for high power electronics applications.

[Display omitted] • ToF-SIMS surface analysis of polyimide layers only revealed surface contamination. • A depth profiling approach allowed to obtain chemical information on the layers. • The use of a large cluster ion source enabled preservation of molecular information. • Multivariate analysis pointed out the characteristic mass peaks for each layer. • This approach allowed to discriminate polyimide layers with very similar structures. Silicon carbide (SiC) is a wide bandgap semiconductor suitable for high-voltage, high-power and high-temperature applications. However, the production of advanced SiC power devices still remains limited due to some shortcomings of the dielectric properties of the passivation layer. Thanks to their high operating temperature and dielectric strength, spin coated polyimide (PI) layers are considered ideal candidates for SiC devices passivation and insulation. In this view, a robust methodology for the physico-chemical characterization of such PI layers is required. Thanks to the use of time of flight-secondary ion mass spectrometry (ToF-SIMS), a SIMS-based surface-sensitive technique that provides specific identification of molecules, it was possible to distinguish different types of PIs employed in commercial SiC devices and postulate their molecular structure. This was obtained after careful selection of the analytical conditions used for the characterization of the specimens. The results attained in this study open the way for further improvements in one of the most key issues in the development of higher SiC power devices. [ABSTRACT FROM AUTHOR]