Direct Etching - Targeting Commercial Photovoltaic Applications

A method for spatially-selective etching of dielectric layers without the use of a mask has been developed at the University of New South Wales (UNSW). This 'direct etching' method, which was first implemented using inkjet printing, is now being further developed using Optomec's Aerosol Jet Printer (AJP), in order to achieve the patterning resolution and processing throughput required for commercial photovoltaic applications. Results presented in this paper show that the use of the AJP enables etched grooves as narrow as 15-20 mu m. Grooves can be etched in similar to 75 nm layers of SiO2, SiNx, SiONx and PECVD Al2O3 dielectric layers. Furthermore, the etching process can be tailored to different applications by varying processing parameters, such as the gas flow rates, platen movement speed and number of printing passes. Finally, the accurate alignment enabled by the AJP allows etched patterns to be formed in pre-patterned surfaces, a property that may find application in a number of selective-emitter solar cell designs which use aligned screen printing for metallization.