In semiconductor and photovoltaic industries numerous process steps deal with etching and silicon surface modification. The present study focuses on the reactivity of HF-H2O2-based mixtures toward silicon surfaces in a wide range of concentrations. The generally very moderate reactivity is investigated regarding kinetic aspects and the silicon dissolution reactions. The activation energy of silicon dissolution in HF-H2O2 mixtures is determined to be ∼50 kJ/mol, which supports a surface reaction controlled mechanism. This interpretation is checked by oxidation experiments of Si surfaces with HF-free H2O2 solutions. Resulting silicon surfaces were characterized by means of diffuse reflection Fourier transform infrared spectroscopy and photoelectron spectroscopy. Surface properties give hints for an “electrochemical” silicon oxidation. Furthermore, the oxidation behavior of different H2O2 solutions is compared to that of HNO3 solutions. All results suggest kinetically limited silicon dissolution in HF-H2O2 mixtures and hole injection into the silicon surface to be the rate-determining part of the reaction process.

The effects of phosphorous gettering and hydrogenation on the minority carrier recombination at crystal defects in directionally solidified multicrystalline silicon are described. Representative industrial wafers, both p- and n-type, and current technologies for the gettering and hydrogenation are used. The main result of this work is a strong link between activation of extended crystal defects (ECDs) by gettering and their passivation by hydrogenation. It is shown that gettering or annealing increases the recombination at active as well as inactive ECDs. Surprisingly, hydrogenation can neutralize this change in activity due to the gettering. However, it neutralizes only part, at most, of the ECD activity already present before the gettering. Therefore, under current industrial processing techniques, these two high-temperature process steps individually give large change but together much less net change of the crystal defect activity. Related phenomena are observed in wafers with strongly varying impurity concentration. Finally, there is little difference in these observations between n- and p-type wafers.

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Silicon nanoparticles have been prepared by many methods, depending on whether porous, amorphous, or crystalline silicon is required. The advantages of the novel solid–gas chemical reaction reported here are that large amounts can be produced in a convenient way, the particles have a very narrow size range, and there is enormous potential for modification of the size and surface of the particles. Details of the synthesis via reaction of lanthanum or LaCl3 with a gaseous mixture of silicon tetrachloride and hydrogen, together with the subsequent characterization of the product, are presented.

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