Atomic layer etching of silicon in Br2-containing plasmas

This paper reports an experimental investigation of Br2 for inductively coupled plasma (ICP) atomic layer etching of silicon. Pulses of Br2 were periodically injected into a constant flow of Ar carrier gas to brominate the Si (100) surface. Two modes of bromination were investigated: plasma gas dosing, in which the ICP was powered during Br2 injection, and gas dosing, where the ICP power was off during this step. Dosing was followed by a purge step, and then ICP plus substrate bias power, leading to etching of the brominated Si surface layer by Ar+. The etching rate exhibited saturation behavior as a function of dose, with rates of 0.80 and 1.3 nm per cycle for gas dosing and plasma gas dosing, respectively. Optical emission from SiBr was used to follow relative etching yields during the Ar+ bombardment step and provide insights into the etching mechanism.