Properties of low-temperature (80-300° C) pyrolytic SiO₂ on Si and InP

Abstract

We report on a new low-temperature pyrolytic deposition technology for silicon dioxide. We present data characterizing the electrical and optical properties of this dielectric deposited on Si and InP substrates. The effects of thermal processing are also reported. Deposition of high-quality SiO₂ is achieved by reacting SiH₄ and O₂ at pressures of 2–12 Torr. Reactions occur by pyrolysis only, promoting stoichiometric SiO₂ deposition and good interfacial properties. No plasma- or photo-enhancement is required. Deposition is achieved at temperatures as low as 80° C, the lowest temperature ever reported for pyrolytic SiO₂ deposition. Rates as high as 65 Å/min at 100° C and 100-150 Å/min at 150-300° C are attained. The leakage current densities measured for both Si and InP MIS capacitors (e.g. 10^-9 Å/cm² for 150° C SiO₂) are two to six orders of magnitude lower than values reported for plasma- and photo-enhanced SiO₂ deposited at equivalent temperatures. The high-temperature integrity of this dielectric also makes it a promising annealing cap for group III-V compound semiconductors. Our annealing studies show that SiO₂-capped indium phosphide surfaces remain specular up to 850° C.