Interface modification of ultrathin SiO2/Si(0 0 1) by nitric oxide treatments: a comparative electron paramagnetic resonance and nuclear reaction analysis study

In this work, we investigate by nuclear reaction analysis (NRA), electron paramagnetic resonance (EPR) spectroscopy and atomic force microscopy (AFM) the NO-induced modifications of the physical properties of oxide layers of thickness <3 nm, obtained by rapid thermal oxidation (RTO) of Si in O2 or O2/O3 mixture. We show that for both types of oxides, the N incorporation kinetics are faster than in the case of thick oxides (>20 nm), and typical concentration of 2×1015 cm−2 can be achieved. The N profiles varies with oxide type. In both cases, the interface defect concentration is reduced after furnace NO treatments by up to a factor of six. Our study reveals that this reduction is not only the consequence of the N incorporation but that the thermal relaxation of the nitrided layer also plays a major role. To investigate this effect, we performed He annealings which change the thermal budget of the dielectric layer. We show that the He annealings of the NO treated layers delays the re-oxidation process further and changes the chemical composition of the nitrided oxide layer. By AFM, we show that the NO treatment does not form a continuous nitrided layer but forms islands at the interface.