Si surface preparation and passivation by vapor phase of heavy water

In our previously published paper [1, 2] we demonstrated that deuterium adsorbs on Si surface at room temperature much stronger than hydrogen [3, 4]. Moreover, in case of deuterium passivated wafers the vacuum storage can be omitted without risking the non-controlled native oxidation of silicon for up to 5 hours or more. It could be a suitable and more robust surface cleaning and passivation process for the industry, but heavy water is expensive. As a cheaper procedure, we present in this paper the results of our studies in which the Si surface is treated in vapor phase of heavy-water (D2O) + 50% HF (e.g. 20:1) mixture at 25, 40, 50 and 65 °C, for 1, 10 and 60 minutes. The surface evolution of the D-passivated surface was followed by contact angle measurements, by spectroscopic ellipsometry (SE), by atomic force microscopy (AFM), by X-ray photoelectron spectroscopy (XPS), by transmission electron microscopy (TEM) and by infrared absorption spectroscopy (IR) qualification and the results were compared to the H-passivated Si surface. It turned out that 1 min vapor phase treatment at 65 °C was enough to remove the native oxide and to passivate the Si surface without any degradation of the atomic surface flatness. Combination of D (or H) passivation with rapid thermal process (RTP) based on the thermal desorption kinetics of the adsorbed D and/or H layers on Si is a promising method for improved interface engineering and for better initial reactions in case of ultra thin dielectric layer formations.