Si/XeF₂ etching: Temperature dependence

The temperature dependence of the Si(100)/XeF₂ etch reaction is studied quantitatively in a molecular beam setup. At a sample temperature of 150 K the reaction probability reaches unity initially, after which the XeF₂ condenses on the surface and blocks the etching process. For increasing temperatures the XeF₂ reaction probability initially decreases from 100% at 150 K down to 20% around 400 K, but for temperatures above 600 K it increases again up to 45% at 900 K. In a simple reaction scheme the high etch rate at low temperatures is explained by a XeF₂‐precursor, with an activation energy for desorption of 32±4 meV. Furthermore the increased etch rate at high temperatures is explained by the desorption of SiF₂ with an activation energy of 260±30 meV. The steady‐state fluorine content of the SiF_x reaction layer, measured using thermal desorption spectroscopy, reaches a maximum of 5.5 monolayers at 300 K. For increasing temperatures it decreases to a submonolayer coverage above 700 K. The temperature dependence of the formation of the reaction layer is described well by including the XeF₂‐precursor in a previously developed adsorption model.