Comparison of the vacuum-ultraviolet radiation response of HfO2/SiO2/Si dielectric stacks with SiO2/Si

Vacuum ultraviolet (vuv) emitted during plasma processing degrades dielectrics by generating electron-hole pairs. VUV-induced charging of SiO2/p-Si and HfO2/SiO2/p-Si dielectric stacks are compared. For SiO2/p-Si, charging is observed for photon energies > 15 eV by ionization of dielectric atoms from photoinjected electrons. In HfO2/SiO2/p-Si, charging is observed for photon > 10 eV and is due to ionization by photoinjected electrons and by H+ trapping in the HfO2/SiO2 bulk. Hydrogen appears during annealing at the Si-SiO2 interface forming Si-H, which, during irradiation, is depassivated by photoinjected electrons. The authors conclude that dielectric charging in thin oxides (< 10 nm) occurs more easily in HfO2/SiO2 than in SiO2. (c) 2007 American Institute of Physics.