Simple, Robust Hydrogen Passivation of Bare Silicon for Estimating Bulk Lifetime of Silicon Wafers

This paper reports on a low temperature, simple, surface passivation technique using onlychemicals commonly found in laboratories that results in a chemically safe and relatively stable surface. The technique has been applied to a bare silicon wafer, resulting in a chemical-free hydrogenterminated surface. Surface recombination velocities on 1 Ohmcm (100) oriented silicon down to 25 cm/s were achieved and remained below 50 cm/s for 30 minutes, confirming the temporal stability of the surface. This temporary surface passivation facilitates the measurement of wafer's bulk lifetime, an important parameter in photovoltaic devices. Being a low temperature process, thermal activation or deactivation of grown-in defects is avoided, increasing confidence in measured bulk lifetimes. By etching the sample in semiconductor grade chemicals commonly used for solar cell processing, the introduction of new impurities to the sample surface is also avoided. The surface is left clean and dry, making it safe and compatible with standard characterization equipment allowing for reliable in-line monitoring of lifetimes in solarcell processing flows without the need for construction of dedicated equipment for immersionmeasurements.