Etching of III-V Materials Determined by ICP-MS with Sub-Nanometer Precision

The use of inductively coupled plasma mass spectrometry (ICP-MS) is proposed in order to study the etching of III-V substrates at the sub nanometer level in diluted chemistries containing hydrochloric (HCl) or sulfuric acid (H2SO4). Based on the stability and the matrix effects of the sample, an optimal concentration of 100 mM HCl or H2SO4 was suggested for the insertion into the ICP-MS. The interferences originating from the acid matrices were effectively attenuated by the octopole reaction system (ORS) when operated in He mode, allowing for the In, Ga and As analytes to be quantified at a single ppb level with an accuracy of ±5% and a precision better than 5%. The presented detection limit, background equivalent concentration (BEC), spike recovery and stability data demonstrated that the ICP-MS technique could be used for determining the dissolved In, Ga and As analytes in a concentration range corresponding to the amount present in a sub nanometer layer.