The single sided nature and high selectivity of the ADE process is particularly well suited to the removal of the poly-silicon from the front side of a wafer, during the manufacturing of a TOPCON solar cell. The a-Si can be etched either before of after annealing. The a-Si is removed from the top surface but critically, also from the wafer 's edges during the ADE process. The BSG under-layer is not etched, due to the high selectivity of the process, providing adequate protection to the cell's emitter, and more flexibility for the associated diffusion process. > Patterning of poly-layers
ADE selectivity can be leveraged to pattern poly-silicon surfaces. In this example, a glass mask was use to pattern the rear of an IBC cell.
>> Presented during the 2024 BC Workshop: LINK
> Laser damage etch
Laser contact opening through SiNx can lead to damage than needs to be etched. The ADE 's etch selectivity allows for direct etching, without interfering with the nitride/oxide layers, nor the back side of the wafer due to the single-side nature of the process.
> Optimized Adhesion of Plated Silicon Solar Cell Contacts
ADE is introduced as plating pre‐treatment to generate a beneficial nano‐roughness on the silicon substrate. The method is shown to improve the adhesion of solar cell contacts that are structured by local ablation of the passivation layer using ns‐pulsed lasers. Due to the high etch selectivity of the ADE process between silicon and silicon nitride, no additional etch mask is required to protect the passivation layer. In peel force tests on busbars, the average peel‐force raised from 0.3 to 2 N mm−1. In sheer‐test on finger contacts an increase of maximum sheer force and a decreasing length of the finger displacement are observed.
>> Check the full paper: LINK
> Single side Emitter etch back/removal - edge isolation
The single-side and finely controllable ADE process is well suited for emitter etch back. Both front side and edges are targeted by the process. Complete removal and edge isolation is also possible.
> FLUORINATION
Gas phase Fluorination of layers is also possible with the ADE platform. Its compatibility with roll to roll configuration makes it suitable for the continuous processing and dynamic fluorination of films. The typical reaction when applied to an organic compound is the substitution of hydrogen atoms by fluorine; direct fluorination involves a reaction of the C-H bond with the elemental fluorine. This is the most common method used for the fluorination of polymers.
