Surface oxide content examination of capping boron layers in UV photodetectors

The capability of Si-based PureB photodetectors to withstand UV radiation is an unconditional requirement for a variety of industrial applications. A good example can be found in the next-generation 13.5-nm lithography systems [1]: UV detectors used to optimize the imaging performance will be exposed to EUV radiation levels as high as a few mJ/cm² [2]. It has been demonstrated in [3] that only 2-nm thick pure boron layer can be resistant to detrimental environments. Such boron layer can be added to fully processed BSI/FSI CMOS imagers as end-of-line capping layer, to passivate their surface, as well as to increase the spectral range of their sensitivity from IR down to soft x-ray. In both applications negligible degradation of the electrical and optical behavior of the photodiodes/devices is highly demanded.