Application of radio frequency capacitively coupled Ar+H2 plasma on rapid annealing of Cu-based photovoltaic grid line

Abstract

With the continuous thinning of photovoltaic silicon wafers for cost reduction, copper based photovoltaic grid lines (Cu-PGL) require annealing and softening treatment. However, for the commonly used short circuit annealing method in industry, some issues exist such as air surface oxidation and environmental pollution, which need to be addressed for large-scale development of high-performance Cu-PGL. In this study, we propose a medium-pressure capacitively coupled plasma driven by radio frequency (RF) for plasma rapid annealing of Cu-PGL to meet solar cell performance requirements. The experimental results show that the yield strength of Cu-PGL decreases from 336.5 MPa to 59 MPa after plasma rapid annealing while electrical conductivity increases from 87 %IACS (International Annealed Copper Standard) to 116 %IACS at the optimal condition of discharge pressure of 1.0 kPa, and input power of 150 W with wire speed of 50 m/min. The plasma annealing mechanism of Cu wire was disclosed by combining spectral diagnosis of the plasma and Cu wire performance characterization.