Selective Etching of Silicon Native Oxide with Remote-Plasma-Excited Anhydrous Hydrogen Fluoride

We demonstrate to the acceleration of the moistureless etching reaction between the silicon native oxide and the anhydrous hydrogen fluoride (AHF) gas, using remote-plasma-excited Ar gas at room temperature. The etching reaction is significantly enhanced by the remote-plasma-excitation for both the chemically grown native oxide films and the dehydrated oxide films. Then, we attempt to improve the selectivity of the oxide etching with respect to silicon by introducing hydrogen into this system, and to realize the highly selective etching of native oxide with respect to silicon. With the increase of the hydrogen partial pressure, the etch rate of silicon rapidly decreases due to the suppression of the density of fluorine radicals in the gas phase. We have confirmed the value of the etch rate selectivity to be at least 4.