Beam shaping - the key to high throughput selective emitter laser processing with a single laser system

Abstract

The fabrication of selective emitters by laser processing has attracted the interest of researchers in recent years. However, narrow foci of Gaussian laser beams limit the throughput and feature an inhomogeneous intensity distribution on the wafer. The use of beam shaping can eliminate this setback. A single laser system delivering <;70 Watt to the wafer is already sufficient to achieve short processing times per wafer. The feasibility of a laser system for a selective laser doping process from PSG is investigated and the potential of eligible beam shaping is assessed. Adequate sheet resistances with a good homogeneity and process stability can be achieved, with minor impact to random pyramid surfaces and no measureable degradation of the material. A diffractive optical element splitting one laser into 10 spots of equal intensity is evaluated and fast processing times are achieved

Large area co‐plated bifacial n‐PERT cells with polysilicon passivating contacts on both sides

“…Lasers with beam shaping (e.g., an elongated top-hat profile instead of circular Gaussian) would be far more suitable for this process. 30 For the inkjet-patterned samples, the polysilicon layers were found to be uniform (Figure 6C, as expected. So, it was suspected that the reason for the high contact resistivity for inkjet-patterned samples 3.…”

“…It is noted that due to the narrow beamwidth (<20 μm), multiple laser passes are made adjacent to each other to create the laser oxidized regions. Lasers with beam shaping (e.g., an elongated top‐hat profile instead of circular Gaussian) would be far more suitable for this process 30 …”

Laser processing of materials for renewable energy applications

“…In modern PV factories, it is desirable for a specifi c manufacturing tool or system to be able to process silicon solar cells at a rate of about 1 wafer/s. Laser systems under development should be able to process wafers at these speeds for the formation of localized contacts since scientists at Fraunhofer ISE 97 have estimated that laser doping of selective emitters could be performed in ~ 1 s per wafer by using a diffractive optic element to split a laser beam into 70 parallel beams.…”

The Influence of Thermal Effects and Dielectric Films on the Electronic Quality of p +-Doped Silicon Processed by Nanosecond Laser

“…Although advanced characterization methods for laser doping have been developed [2]- [8], the dependence of this degradation on the combination of laser parameters, dopant precursors, and dielectric films is complex and has not been fully elucidated. Literature reports suggest the ability of laser doping to achieve successful dopant incorporation with low-material-quality damage, as demonstrated either through measurements of the carrier lifetime and saturation current densities [9], [10] or through demonstration of good cell performance [11]. However, in these publications, the lifetime and recombination parameters were characterized using large contiguous doped areas that were produced with dopant precursors and overlapping laser pulses.…”