Studies of laser generated debris in crystalline silicon solar cells

Lasers are commonly used in production of solar panels for processes such as drilling through wafers and edge isolation. These laser ablation processes generate microscopic and macroscopic debris which can cause problems with the laser process itself and subsequent production processes. Therefore, it is necessary to understand the generation of debris in the laser ablation process. In this paper, laser ablation of silicon irradiated by 1064 nm pulses emitted by a Nd:YAG laser has been investigated. Here, the ablation process was carried out at various stage speeds. The process was then assisted by a combination of pressurised air and air suction to study the effect on debris formation. Analysis shows that increasing the stage speed resulted in grooves with a smaller Heat Affected Zone and less debris distribution. The effect of applying pressurised air and air suction removed the debris present at the bottom of the groove but it has no effect on the tapers present at the groove edges. These grooves were then chemically etched and it was found that etching completely removed the debris and tapers. However, the use of nitrogen extraction during ablation was found to produce good quality surface finish.