Secondary Ion Mass Spectrometry Study of Hydrogenated Amorphous Silicon Layer Disintegration upon Rapid (Laser) Annealing

Double layers of deuterated and hydrogenated amorphous silicon (a-Si:H) on glass are heated in ambient by scanning with a green (532 nm) continuous wave laser. The hydrogen diffusion length in the laser spot is obtained from the deuterium (D) -hydrogen (H) interdiffusion measured by secondary ion mass spectrometry (SIMS), the temperature in the laser spot is obtained by calculation. Under certain conditions, detachment of the deuterated layer from the hydrogenated layer is observed in the SIMS depth profiles, visible by rising oxygen and carbon signals at the D/H interface attributed to in-diffusion of atmospheric gas species like water vapor, oxygen and carbon oxide. Stacks involving both undoped and boron-doped a-Si:H films show disintegration. The results suggest that the parameters leading to the disintegration effects are the presence of a plane of reduced material cohesion at the D/H interface, a sizeable H diffusion length and a rather high heating rate. We consider it likely that the observed layer disintegration process is involved in the peeling of a-Si:H films upon fast heating. Furthermore, the results show that rapid laser heating can be used to detect planes of reduced material cohesion which may compromise the electronic properties of a-Si:H based stacks.