(Invited) Second Harmonic Generation: A Powerful Non-Destructive Characterization Technique for Dielectric-on-Semiconductor Interfaces

摘要

The quality of interfaces between dielectrics and semiconductors has a tremendous impact on the performances of semiconductor devices. High-k dielectrics are omnipresent in the gate stack of advanced MOSFETs. They are also used as passivation layers for silicon in fields such as solar cells or image sensors. When referring to passivation, two mechanisms can be identified: chemical passivation (quantified by the interface state density, D_(jt)) and electric-field passivation (quantified by fixed oxide charge density, Q_(ox)). An ideal characterization method for passivated silicon should give access to both chemical and field-effect relevant quantities (ideally being able to distinguish them) in a non-destructive way. Among the commonly used techniques, we can cite electrical methods based on current or capacitance monitoring of simple test devices, Corona characterization of semiconductors, carrier lifetime extraction conducted through photoconductance or photoluminescence decay measurements, etc. The choice among these several options is based on criteria such as sensitivity, non-destructiveness, possibility of direct on-wafer probing without any additional device fabrication steps, ability to discriminate D_(jt) and Q_(ox), capability to provide a high spatial resolution. A recent technique which could meet all these criteria is the second harmonic generation (SHG), provided that an appropriate calibration method is developed for D_(it) and Q_(ox) extraction.