Semiconductor Film Stack Interface Investigation via DSIMS & TOFSIMS Depth Profiling and HAXPES : Yield Enhancement/Learning

Semiconductor interface investigation via analytical characterization represents a major focus for Failure Analysis and Process Characterization Teams. Investigation can be performed via destructive techniques through depth profiling until reaching the interface while collecting matrix and impurity distributions as a function of depth and also via nondestructive techniques which preserves information about the interface. Interface characterization involves the deployment of Failure Analysis resources, employing advance imaging and materials characterization techniques like TEM (transmission electron microscopy), SEM (Scanning Electron Microscopy), DSIMS (dynamic secondary mass spectrometry), TOFSIMS (time of flight secondary ion mass spectrometry), Auger, XRF (X-Ray Fluorescence), and XPS (X-ray Photoelectron Spectroscopy). As first exampled in the case study detailed in this paper, increased aluminum resistance was caused by oxidation of aluminum metal while in a cooling chamber prior to barrier layer deposition due to chamber lid atmospheric leaks. High resistivity interconnect issues can be related to interface quality and diminish product performance up to complete failure. Typical methods like cross section analysis via TEM and SEM did not reveal any abnormality. This prompted further investigation where innovative depth profiling methods of DSIMS / TOFSIMS to the encapsulated interface was used, highlighting the presence of oxidized aluminum metal. In another example, analysis was performed nondestructively utilizing a newly developed High Energy HAXPS mode, allowing for the successful characterization of interfaces and high electron mobility transistors where layer interaction is vital.