H2O2 DECOMPOSITION AND ITS IMPACT ON SILICON SURFACE ROUGHENING AND GATE OXIDE INTEGRITY

In this study the impact of temperature and metal contamination on the stability of hydrogen peroxide in the two most common wet chemical cl eaning mixtures for wafer process operations has been investigated. Th e stability of the caustic mixture (NH4OH/H2O2/H2O) was found to be ve ry sensitive to certain metallic contaminations in the sub-ppb range, while the stability of the acid mixture (HCl/H2O2/H2O) is mainly influ enced by non metallic, anionic components of the solution itself. We o bserved also a strong oscillating behaviour of the rate of the oxygen gas evolution caused by the decomposition of H2O2. Furthermore it was found, that the oxygen gas bubbles, formed by the decomposition of hyd rogen peroxide cause a certain kind of micro-roughness on the silicon surface through a micro masking mechanism. In a series of experiments we could prove that this kind of surface roughness has a significant i mpact on the integrity of thin gate oxides.