Hydrogen Plasma Treatments of Amorphous/Crystalline Silicon Heterojunctions

AbstractHydrogen plasma post-deposition treatments of amorphous/crystalline silicon heterojunctions, which are known to enable superior passivation, are further investigated. The influence of certain plasma process parameters, including substrate temperature, gas pressure, plasma power density, excitation frequency and distance between electrode and substrate, is examined. The passivation quality after a hydrogen plasma step is depending on the density of atomic hydrogen in the plasma and on sufficient hydrogen diffusion to the interface. A variation of the electrode to substrate distance reveals that the indiffusion of hydrogen is accompanied by dry etching of the amorphous layer. To reach sound passivation quality it is necessary to introduce a certain amount of hydrogen, while at the same time limit the damage due to etching of the amorphous silicon and maintain the right amorphous silicon film thickness for solar cell application