Electrochemical and analytical study of the Si etching mechanism in HF

In this work a methodology and metrology for the substrate and dopant loss during cleaning and etching of Si semiconductor substrates has been developed. Using this methodology, the substrate loss in different HF based cleaning solutions can be investigated. The etching mechanism in different HF mixtures is studied, where the effect of dissolved O2, illumination, HF-concentration and additives can be explored. This knowledge must allow controlling the etching and surface terminations during HF-based cleaning for different critical process steps. Electrochemical measurements are done in a electrochemical cell, as described elsewhere (1). This setup allows in-situ measurements at the surface during the actual cleaning or etching process. At the Open Circuit Potential (OCP) the corrosion current icorr is measured and a typical voltammogram of p-type Si in HF is shown in Figure 1. By these measurements it’s possible to determine a polarization resistance Rp which can be linked to the etch rate dN/dt and the number of electrons exchanged (n) (2,3), according t