The effects of 7.2 eV vacuum ultraviolet (VUV) and 4.9 eV ultraviolet (UV) irradiation on a 20 nm HfO2 layer atomic layer deposited (ALD) on (100) Si substrate are explored with electron-spin resonance (ESR). Silicon dangling-bond defect concentrations (Pb centers) and positively charged oxygen vacancies (E’ centers) were measured with g-factor fitting. The concentrations of the defect states are presented. VUV irradiation increases the level of Pb0 and Pb1 states, while UV decreases the level of Pb0 and Pb1 states, but increases the level of E’ states significantly. [i] [#_edn1] In addition, rapid thermal annealing (RTA) mitigates the effects of both VUV and UV irradiation. Surface-potential measurements with a Kelvin probe show that electron photoemission process dominate VUV irradiation. On the other hand, electrons are transferred from E’ states to the silicon substrate during UV irradiation. At the same time, electrons are photo-injected into the dielectric layer from the substrate. Furthermore, VUV spectroscopy measurements show that the Fermi level for E’ defect states is around 4.7 eV, which is within the bandgap of the dielectric layer. Also, previous work [ii] [#_edn2] shows that the E’ states, as oxygen-interstitial defects (OID), are located within the HfO2 layer. We conclude that VUV irradiation modifies the concentrations of the silicon dangling-bond defect states and UV irradiation can be a potential source for positively charge oxygen vacancies during the processing.

 Work Supported by the Semiconductor Research Corporation under contract 2008-KJ-1781

[i] [#_ednref] H. Ren, S.L. Cheng, Y. Nishi and J.L. Shohet, Applied Physics Letters (to be published)

[ii] [#_ednref][ii] J.L. Lauer, J.L. Shohet and Y.Nishi, Applied Physics Letters 94, 162907 (2009)