Selective Dry Etching of p-Type Si Films for Photolithography Processing of Interdigitated Back Contact Silicon Heterojunction Solar Cells

• Published in: IEEE journal of photovoltaics 2017-09, Vol.7 (5), p.1292-1297
• Main Authors: Do Yun Kim, Lentz, Florian, Yong Liu, Singh, Aryak, Richter, Alexei, Pomaska, Manuel, Lambertz, Andreas, Kaining Ding
• Format: Article
• Language: English
• Subjects: Dry etching; Hafnium; Inductively coupled plasma chemical vapor deposition (ICP-CVD); interdigitated back contact (IBC); Lithography; Passivation; photolithography; Photovoltaic cells; reactive ion etch; Silicon; silicon heterojunction (SHJ)
• ISSN: 2156-3381; 2156-3403
• DOI: 10.1109/JPHOTOV.2017.2719866

Highly doped p-type Si thin films are hardly etched by alkaline etchants unlike i- and n-type Si films. In addition, the use of a HNO 3 /HF/H 2 O mixture to etch p-type Si films can lead to inhomogeneous etching of p-type Si films and consequently result in excessive surface roughness and inferior surface passivation. For these reasons, we have implemented a dry etching method to selectively pattern p-type Si films for interdigitated back contact (IBC) silicon heterojunction (SHJ) solar cells using a SiO x masking layer. In this way, the underlying passivation layer and the Si surfaces can be undamaged. In this study, the etch rates of all Si films that make up IBC-SHJ solar cells have been investigated in order to obtain high etch selectivity and establish proper patterning steps. Furthermore, we have fabricated IBC-SHJ solar cells on planar wafers by using dry and wet patterning methods developed in this study. As a result, a conversion efficiency of 15.7% is obtained with Voc of 682 mV, J sc of 33.8 mA/cm 2 , and FF of 0.68.