Plasma single-sided etching for rear emitter etch-back and flattening of industrial crystalline silicon solar cells

In this paper, we present investigations on single-sided plasma etching for silicon wafers with work aimed for the development, characterization and application of single-sided plasma etching processes for industrial silicon solar cells. Tests were conducted using a popular industrial inline plasma system from Roth&Rau (modified SiNA). For high-efficiency cell structures with passivated and locally contacted rear side; it is beneficial to prepare a polished/flat rear surface to achieve a very good quality of passivation. During this work different dry etching approaches (using SF6- and O2-based plasma chemistry) for the solar cells rear, have been investigated in terms of resulting surface topography and optical performance. Solar cells processed with the developed plasma etching steps (for front and rear surface) exceeding 17% efficiency are reported in this study. The investigated process can be adapted to fit in the workflow for PERC-type (passivated emitter and rear cell) high-efficiency solar cell structures.