Interaction of low-energy electrons with nitrogen-bearing species on silicon(100).

As feature size in microelectronic devices decreases, silicon nitride and oxynitride are considered to replace the gate oxide of choice of the last several decades---silicon dioxide. Electron beam assisted nitridation and oxynitridation were investigated in this project, using ammonia and nitric oxide as precursors. The nitridation and oxynitridation of Si(100) were studied with XPS, AES, ESD, TPD and HREELS. The low thermal budget approach used may be attractive for potential development as a practical technique for the semiconductor industry. Electron beam enhanced nitridation from ammonia was unambiguously demonstrated using multiple surface analytical techniques. The electron beam was shown to effectively remove hydrogen from NHx (a) (x = 3,2) and from the silicon surface. Electron stimulated desorption of adsorbed hydrogen and dissociation of adsorbed NHx are believed to be responsible for the enhanced nitridation. Nitride can also form on the surface by irradiating the surface in an ammonia environment at 110 K. A nitride growth rate of 1A/min was obtained from the bulk Si LVV AES signal intensity attenuation. Nitric oxide both molecularly and dissociatively adsorbs on Si(100) at 110 K. The electron beam irradiation of the molecularly adsorbed NO was found to enhance oxynitride formation while the thermal process simply removes NO(a). The oxynitride overlayer was observed to form on Si(100) by irradiating the sample in a NO environment. The overlayer thickness exhibited a linear dependence on the electron irradiation/NO exposure time. An oxynitride growth rate of 0.2 A/min was obtained. A N 1s shake-up satellite peak around 410 eV was observed from N(a) species. The behavior of the 410 peak upon annealing may indicate the presence of the dative pi-bonding involved in the planar Si3N species. This work suggests that XPS could be used to show structural differences of the silicon nitride and its precursors, indicating XPS can be used for quality control in the nitridation process