Numerical and Experimental Investigation of Sustainable Rinsing Processes for Silicon Solar Cell Manufacturing

In this work, potential improvements for the rinsing process of Si wafers are identified. A numerical model was developed which describes the concentration distribution near the wafer surface of potassium hydroxide (KOH) as a function of time, temperature, volume flow, wafer size and gap distance between the wafers. The simulation results showed that a temperature increase from 25°C to 45°C reduces the KOH concentration at the wafer surface by 35%. An increase of wafer size from M2 to M12 led to an increase in rinsing time and water consumption of 10%. In contrast to constant low-flow rinsing, the combination of a phase without flow and subsequent high flow saved 35 s of process time. The simulation results were transferred to experimental rinse recipes. With regards to the flow conditions two different inlet pipes, an industrial standard and an optimized pipe are compared using three different recipes. In the experimental comparison of the rinsing scenarios, the final conductance was reduced by half for a recipe of two minutes without flow and three minutes high flow using the optimized inflow pipe, compared to the five-minute low flow recipe using the standard inflow pipe.