Effects of thermal vacuum nitridation of Si(100) surface via NH3 exposure

•Si(100) is nitrided with NH3 at 400 °C without plasma to form SiNx.•The nitridation method decreases defect densities at HfO2/Si(100) interface.•The nitridation method decreases leakage current through HfO2/SiO2/Si. Low temperature treatments to control the Si-interface properties become more and more relevant to the broad Si-based electronics and photonics technology when the back-end-of-line processing is developed and the integration of hybrid materials on the Si platform increases. In this work we have investigated effects of NH3 nitridation of three different Si surfaces in ultrahigh-vacuum (UHV) chamber at 400 °C: (i) nitridation of well-defined Si(100) (2 × 1)+(1 × 2) cleaned by the high-temperature flash heating, (ii) nitridation of the Radio Corporation of America (RCA)-cleaned H-terminated Si(100) with the final HF dip, and (iii) nitridation of the RCA-treated (without the final HF dip) Si(100) which includes so-called wet-chemical oxide of SiO2. X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy/spectroscopy measurements show that nitrogen incorporates into subsurface layers of clean Si and into the SiO2 chemical-oxide layer, when the materials are exposed to NH3 background in UHV chamber without a plasma source at 400 °C or even at room temperature. XPS results indicate that the nitridation does not remove oxygen from the SiO2 chemical oxide. The nitridation of SiO2 is also found to increase the density of electron levels at 3 to 4 eV above the Fermi level. Electrical measurements of atomic-layer deposited HfO2/Si(100) capacitors with and without the nitridation support that the method has potential to decrease amount of interface defects and to control interface properties.