UV scanning enabling advanced SOI defectivity monitoring

SOI material is now established as the substrate of choice for advanced microprocessors applications, pushing SOI technology to ultrathin layers and high volume production. When reviewing ITRS roadmap targets (1), several challenging items appear, such as required threshold for defectivity monitoring. Using UV wavelength, light transmitted in SOI layer is absorbed in the first A and no more reflectivity issue is impacting defectivity measurement. Then, bare silicon inspection strategy can be applied on SOI without anymore need for dedicated calibration curves. Defectivity benchmark between bare silicon and SOI substrates using same recipe is enabled and is showing similar defect levels. Then, equivalent yield reported on bulk and SOI can be more easily understood.