The mechanism of secondary grain growth in polysilicon films

Secondary grain growth in 0.5 mu m thick undoped and phosphorus-doped polysilicon films, produced by low-pressure chemical vapour deposition, is investigated by transmission electron microscopy. Analysis shows that the driving force for secondary grain growth in phosphorus-doped polysilicon films is the difference in dislocation density in the normal and secondary grains for the early stages of secondary grain growth; the driving force is due to surface energy anisotropy for the subsequent growth stages. The mast probably secondary grain formation mechanism is grain coalescence assisted by dislocation climb.