Effect of halogen on the structure of tow temperature polycrystalline silicon thin films fabricated on glass substrates

Polycrystalline silicon thin films were fabricated by VHF (100-144 MHz) pla sma enhanced chemical vapor deposition, Three different source materials we re used to grow the films on glass substrates: (1) SiH2Cl2/H-2, (2) SiF4/H- 2 and (3) SiH4/H-2 mixing gases. It was found that the gas mixing ratio whe re crystal silicon grows strongly depends on the selection of source gas: i .e,, crystal growth occurred at mixing ratios (SiF4/H-2) smaller than 30/10 seem while the crystal growth in SiH4/H-2 system required much smaller mix ing ratios, such as less than or equal to 1/50 seem, Microstructures of the films were also strongly influenced by the source material, (220) orientat ion structures were easily obtained when SiF4, SiH2Cl2 or B2H6 were used, c ompared to SiH4. In addition, (400) preferentially oriented film grew on gl ass when the film was grown at a gas mixing ratio of SiF4/H-2 = 30/10 seem and a substrate temperature of 200 degrees C, Chlorinated source gases incl uding SiHnClm (n+m=4) are also expected to produce (400) oriented growth.