Low-temperature growth of polycrystalline Si and Ge films by redox reactions of Si2H6 and GeF4

Low-temperature growth of polycrystalline Si and Ge films has been investigated by low-pressure chemical vapor deposition (LP-CVD) featuring a redox reaction of disilane (Si2H6) and Germanium tetrafluoride (GeF4). The film growth is established in a wide range of 0.4–100 torr and in low-temperature range of 300–450°C. The Si content significantly depends on the reaction modes in which either Si2H6 or GeF4 is activated preferentially, and thus the film composition is varied from >90 atm% Si to >90 atm% Ge. It is found that the isolated nuclei are formed directly on the substrate surface and provides a good basis of high crystallinity in a thin film irrespective of the film contents. The mechanism of film growth and the origin of low-temperature crystal growth are discussed from a chemical point of view according to the experimental results.