SULFURIZATION OF SIO2 SURFACE FOR POLYCRYSTALLINE SILICON GROWTH ON SIO2 SI STRUCTURE AT 250-DEGREES-C

A study of sulfurizing SiO2 surfaces for the growth of Si/SiO2/Si stru ctures was done in the present work. The silicon film was deposited at 250-degrees-C by plasma enhanced chemical vapor deposition. All of th e deposited Si films with or without sulfur treatment were of amorphou s phases with a H-2/(SiH4+H-2) flow ratio less than 92%. For those fil ms deposited at the H-2/(SiH4+H-2) flow ratio of 92%, a transition amo rphous Si layer appeared between the SiO2 and polycrystalline silicon films in those samples without sulfur treatment. No transition amorpho us Si layer was present in the sample deposited with sulfur treatment, and the largest grain size of polycrystalline silicon was estimated t o be around 500 angstrom. The polycrystalline phase was obtained in al l the silicon films deposited on SiO2/Si substrate with a H-2/(SiH4+H- 2) flow ratio larger than 92%. This technique would be applicable towa rds thin film transistor fabrication.