Etchant/dopant material offers non-contact inkjet selective emitter solution for solar front contacts
Additional benefits include the material being a non-contact, single-step, and cost-effective solution. Ink jet doping and etching with VersaEtch is a hybrid tool that can be used together with either screen printing or electroplating of metallized contacts.
“We developed the VersaEtch Etchant/n-Dopant in response to market feedback from leading solar cell producers about the most efficient way to integrate the benefits of inkjet technology into solar cell production,” explained Steve Liker, Director of Sales and Marketing at Trident Solar. “The manufacturers wanted a single-step, non-contact process that would enable more efficient front contacts by etching through the SiNx ARC layer then diffusion doping the silicon emitter. This selective emitter approach can decouple the metallization process from the etching / doping process maximizing the results of both areas.”
Combining the etching and doping processes also eliminates the need for precise alignment of etchant and dopant in two separate processes.
As a non-contact process, use of the VersaEtch Etchant/n-Dopant can result in up to a 10x reduction in costly wafer scrap compared to the use of contact selective emitter processes such as screen etching or laser etching. Scrap rates currently range from 0.5 -1.0% and can be reduced to as low as 0.1%.
The VersaEtch Etchant/n-Dopant was developed and is manufactured by Alpha PV Technologies (patent pending) for Trident Solar as the result of a collaborative effort of both companies.
The material can be jetted from the Trident 256Jet-S printhead and etch through the SiNx ARC layer when heated to 350°C. When heated to 800°C the n-dopant diffuses into the silicon active emitter. All that is needed to complete the process is a post water rinse.
The Trident 256Jet-S industrial printhead was specifically designed for solar applications. The printhead features stainless steel construction for chemical inertness and a unique repairable design – that allows the nozzle plate to be disassembled, ultrasonically cleaned and reassembled. These features set the 256Jet-S printhead apart from disposable inkjet technologies and graphic printheads that were adapted to solar applications but not specifically designed to deliver consistent performance in the deposition of aggressive solar process fluids such as acidic dopants and alkaline etchants. These features allow the 256Jet-S printhead to last up to 5 times longer than alternative inkjet printheads .
While the use of the Trident 256Jet-S printhead to deposit the VersaEtch Etchant/n-Dopant has been demonstrated, additional applications are also in development in order to maximize the use of ink jet investment . These include crystalline silicon applications such as jetting palladium as a seed layer and thin film applications like the jetting of alkaline etch. Trident is also developing an application for inkjet deposition of a diffusion barrier for either crystalline silicon or thin film applications.
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