Investigation of blistering of sputtered silicon nitride anti-reflection layer
In the course of a trend to use material with low quality for silicon solar cells there is a growing demand for good bulk passivation. An important parameter for the bulk passivation of multi crystalline solar cells is the hydrogen rate of the SiN:H anti-reflection layer. The hydrogen in this layer diffuses during the SiN;H deposition as well as during the contact formation process in the bulk and passivates impurities and defects. One advantage of the sputter technology compared to other deposition systems is the possibility to vary the amount of hydrogen easily. At high hydrogen concentrations in the SiN:H anti-reflection layer blistering occurs. Researches have shown that the cell performance increases with higher hydrogen concentrations, the only limiting factor being the occurring of blistering. In this work we present results for understanding the blistering effect and techniques to shift the blister boundary.