Direct observation of x-ray radiation-induced damage to SiO2/Si interface using multiwavelength room temperature photoluminescence

Higher failure rates have been observed for devices at or adjacent to areas that have been measured or inspected by in-line x-ray during front end of line process steps. The failures are thought to be related to SiO2/Si interface damage caused by x-ray radiation during routine in-line element, material, and process monitoring. This issue has been noted for highly advanced integrated semiconductor devices following device failure mode analysis of Si wafers, with and without x-ray in-line inspection. A multiwavelength room-temperature photoluminescence (RTPL) study was performed to identify the presence of such damage in x-ray irradiated wafers from various types of x-ray inspection steps during device fabrication processes. It was found that x-ray radiation as low as 16 keV induced damage at the SiO2/Si interface. The damage to the SiO2/Si interface was successfully observed by using multiwavelength RTPL wafer mapping.