Correlation of Stress in Silicon Nitride Layers with their Complete Removal by Laser Ablation

In recent years laser ablation of dielectric layers for local structuring of solar cell passivation layers has become more and more common. Apart from adjusting laser parameters for a damage-free removal of dielectric layers, it is necessary to prepare the surface in a way suitable for the respective contact methods (screen printing, nickel plating, etc.). In this study, we demonstrate for silicon nitride layers how the deposition parameters and deposition method correlate to the characteristics of the ablated area. Furthermore a simple method to predict these characteristics is introduced based on the determination of the intrinsic stress in the dielectric layer. A correlation between compressively stressed or stress-free silicon nitride layers and a complete ablation was found.