UV ANNEALING OF LOW-TEMPERATURE PHOTODEPOSITED SIO2-FILMS WITH A NEW POWERFUL LAMP SOURCE

A decrease of processing temperature is essential for III-V semiconductors and in general for technology of opto-electronic devices. In this work, silicon dioxide films were deposited on Si and InP substrates using an UV-induced CVD process. SiO2 was prepared using a SiH4/O2 mixture diluted in N2, and deposition rates as high as 60 angstrom/min at a substrate temperature of 100-degrees-C have been obtained. The light source consists of a new xenon UV-VIS-IR lamp with wavelength ranging from 170 nm to 3-mu-m. This lamp offers a high luminance continuous spectrum in the UV frequency range of interest (170-250 nm). With this powerful lamp coupled to a flowing all-optical reactor, the deposition temperature could be reduced to 100-degrees-C. Such a high photon fluence has also allowed for the first time to observe an effect we call "UV annealing". In fact, direct absorption of energetic UV photons by several localized chemical structures (Si-H, OH, absorbed water) removes the photochemical by-products of the previous reaction, and finally leads to the production of Si-O-Si bonds. The evolution of the solid-state reactions was studied in situ, using a surface-sensitive multiple internal reflection technique coupled with infrared spectroscopy (FTIR). Subsequent improvement by UV annealing of dielectric layers deposited on InP substrate was demonstrated from C(V) measurement of MIS capacitors, fabricated of these structures.