Cathodoluminescence spectroscopy of nitrided SiO2-Si interfaces

We use cathodoluminescence spectroscopy (CLS) to investigate the electronic states of ultrathin gate dielectrics with nitrided SiO2-Si interfaces, kno wn to improve reliability in advanced complementary metal-oxide-semiconduct or devices. The 5 nm,thick films investigated were: (i) as-deposited (at 30 0 degrees C) structures, (ii) 400 degrees C hydrogen anneal, (iii) 900 degr ees C rapid thermal anneal (RTA), and (iv) a combination of both anneals. C LS emission energies and intensities versus excitation energy were essentia lly unchanged for the as-deposited interface compared to non-nitrided plasm a-processed interfaces. In the near-infrared, features appear at 0.8 and 1. 0 eV, with the 1.0 eV peak Si substrate intensity increasing with increasin g depth. From depth variation measurements at higher photon energy, a 3.4 e V peak is also shown to arise from the Si substrate, and a 2.7 eV feature i s shown to come from the interface region. After hydrogenation, the CLS is essentially the same as for non-nitrided interfaces, except for an increase in the relative intensity of a broad background luminescence ranging from 1.5 to 2.5 eV. However, the RTA and the combination of the RTA and hydrogen ation do not completely suppress emission near 2.0 eV feature as for non-ni trided interfaces. From the behavior of the CLS features, we are able to cl early distinguish between interfacial defects and substrate features, which are significantly reduced by the combined RTA/hydrogen anneal, and feature s that are not reduced by the annealing procedures. (C) 1999 American Vacuu m Society. [S0734-2101(99)22804-7].