Annealing properties of open volumes in strained SiN films studied by monoenergetic positron beams

The effect of annealing on open volumes in strained SiN films deposited on Si by plasma enhanced chemical vapor deposition was studied using monoenergetic positron beams. For compressive SiN, the stress was reduced by postdeposition annealing; this effect was attributed to the relaxation of matrix structures accompanied by an expansion of small open spaces intrinsically existing in the matrix and the introduction of large open volumes. For tensile SiN, although annealing tends to decrease the concentration of large open volumes, the size of the small open spaces and the film stress were almost constant up to 1000°C annealing. This was attributed to the network structure related to the open spaces remaining stable even at 1000°C annealing, and this mainly determines the stress in the tensile film.