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

Abstract

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.

Rapid, noncontact, sensitive, and semiquantitative characterization of buffered hydrogen-fluoride-treated silicon wafer surfaces by terahertz emission spectroscopy

“…Because of the complicated situations at the Si surface, such as the native oxide layer, dangling bonds, or the presence of other absorbed particles, the properties of the Si surface, including the surface potential and surface electric field, vary widely but are essential to Si-based devices fabrication 2 , 3 . In the modern semiconductor industry, hydrogen fluoride (HF) and its buffered (BHF) solutions are frequently used to treat the surface and remove the native oxide layer 4 – 6 . After BHF etching, a hydrogen(H)-terminated surface forms, and the surface properties change significantly owing to the variation in the surface states and the generation of surface dipoles 7 , 8 .…”