NUCLEATION AND GROWTH OF SILICON ON SIO2 DURING SIH4 LOW-PRESSURE CHEMICAL VAPOR-DEPOSITION AS STUDIED BY HYDROGEN DESORPTION TITRATION

We have developed a new approach to characterize the initial stages of nucleation and early growth of Si on SiO2 from SiH4 at low pressures. In a rapid thermal chemical vapor deposition reactor a sequence of alternating growth and hydrogen thermal desorption cycles using an in situ mass spectrometer is carried out. Desorption of hydrogen (a reaction product) is used to titrate the area of exposed Si surface on the SiO2 surface after each growth step. A sensitivity of better than 10(-3) monolayers (ML) is demonstrated. Nucleation and growth of Si islands is seen upon SiH4 exposure under chemical vapor deposition conditions (500-700-degrees-C). Once nucleated, the islands grow in size at rates consistent with those of Si epitaxial growth until they merge to form a polycrystalline film.