Surface photovoltage spectroscopy for the evaluation of oxidation processes in the microelectronic industry

Inhalt:
We analyze various oxidation processes performed in horizontal and vertical furnaces, and in atomic layer deposition (ALD) system by using surface photovoltage measurements. We demonstrate that the minority carrier diffusion length (MCDL), which is an indicator of the purity of silicon wafers depends significantly on the design of furnaces used for thermal oxidation, loading (unloading) temperature, gases and their flow ratios used during the oxidation. In many cases, MCDL is also sensitive to the type of wafers used for the oxidation and their growth methods. We interpret these results with an emphasis on the formation of electrically active O-related defects in oxidized wafers. At last, we show that MCDL in Si wafers after the deposition of alumina layers by using the atomic layer deposition technique is significantly larger in comparison to those obtained after thermal oxidation. Possible reasons of this phenomenon are also discussed.