Effects of Dipping in an Aqueous Hydrofluoric Acid Solution before Oxidation on Minority Carrier Lifetimes in p-Type Silicon Wafers

概要

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A scanning photon microscope is successfully applied to measure ac surface photovoltages which correspond to apparent minority carrier lifetimes ($\tau_{\text{PCD}}$) measured by the microwave-detected photoconductive decay ($\mu$-PCD) method, using oxidized p-type silicon wafers pre-treated with or without dipping in an aqueous hydrofluoric acid (HF) solution. The dipping in HF solution causes a larger fixed oxide charge, resulting in a strongly inverted layer beneath the oxide. This situation gives longer $\tau_{\text{PCD}}$ than the bulk lifetime ($\tau_{\text{PV}}$) by an ac photovoltaic method, while if the fixed oxide charge is small, $\tau_{\text{PCD}}$ gives an apparently smaller lifetime than $\tau_{\text{PV}}$, implying that $\tau_{\text{PCD}}$ is influenced by the surface charge state or the surface potential. Hence, the process diagnosis by lifetime requires the measurements by both surface photovoltages and the $\mu$-PCD method.
INSTITUTE OF PURE AND APPLIED PHYSICSの論文
1989-05-20