Effect of hydrogen on the low-temperature growth of polycrystalline silicon film deposited by SiCl4/H2

We employed plasma enhanced chemical vapor deposition technique to fabricate poly-Si films grown at a low temperature of 250 °C by using SiCl4 with various H2 dilutions as source gases. It is found that a high deposition rate over 0.25 nm/s can be achieved by using SiCl4 with low hydrogen dilutions. The Raman spectra measurements and scanning electronic microscopy observations reveal that the crystalline fraction as well as the grain size increases with decreasing the hydrogen dilution ratio. However, they start to decrease rapidly when the hydrogen dilution ratio becomes lower than a certain level. The hydrogen dilution ratio for achieving the best crystallinity is found to decrease with increasing the RF power. These behaviors are completely different from those observed in the SiH4/H2 system. It is suggested that hydrogen plays an important role in the low-temperature growth of poly-Si films. The growth mechanism is discussed in terms of surface reactions and is compared with that in the SiH4/H2 system.