Measurements of the thermomechanical stress in amorphous silicon films deposited by low pressure chemical vapour deposition (LPCVD) from disilane Si2H6 are reported as a function of the deposition parameters (temperature, gas pressure and wafer spacing). Major influences of the deposition temperature and the deposition rate are put into evidence and related to the films ordering and hydrogenation. The effects of a 600 degrees C anneal are also investigated and a transition from highly compressive to highly tensile stress is characterised whatever the deposition. Such behaviour has been explained thanks to hydrogen atoms out-diffusion and crystallisation effects.