Enhancement of deposition rate at cryogenic temperature in synchrotron radiation excited deposition of silicon film

The authors have investigated the synchrotron radiation excited deposition of silicon films on the SiO2 substrate by using SiH4/He mixture gas at BL-12C at Photon Factory. They used VUV light from the multilayer mirror with the center photon energy from 97 to 123eV, which effectively excites L-core electrons of silicon. Substrate temperature was widely varied from -178 degree C to 500 degree C. At -178 degree C, the deposition rate was as high as 400nm/200mAHr (normalized at the storage ring current at 200mA). As increasing the substrate temperature, the deposition rate was drastically decreased. The number of deposited silicon atoms is estimated to be 4 to 50% of incident photons, while the number of photo generated species in the gas phase within the mean free path from the surface is calculated as few as about 10-3 of incident photons. These experimental results show that the deposition reaction is governed by the dissociation of surface adsorbates by the synchrotron radiation