Laser ablation of SiO₂for locally contacted Si solar cells with ultra‐short pulses

Abstract We apply ultra‐short pulse laser ablation to create local contact openings in thermally grown passivating SiO 2 layers. This technique can be used for locally contacting oxide passivated Si solar cells. We use an industrially feasible laser with a pulse duration of τ pulse ∼ 10 ps. The specific contact resistance that we reach with evaporated aluminium on a 100 Ω/sq and P‐diffused emitter is in the range of 0·3–1 mΩ cm 2 . Ultra‐short pulse laser ablation is sufficiently damage free to abandon wet chemical etching after ablation. We measure an emitter saturation current density of J 0e = (6·2 ± 1·6) × 10 −13 A/cm 2 on the laser‐treated areas after a selective emitter diffusion with R sheet ∼ 20 Ω/sq into the ablated area; a value that is as low as that of reference samples that have the SiO 2 layer removed by HF‐etching. Thus, laser ablation of dielectrics with pulse durations of about 10 ps is well suited to fabricate high‐efficiency Si solar cells. Copyright © 2007 John Wiley & Sons, Ltd.