Effect of ammonium halide salts on wet chemical nanoscale etching and polishing of InGaAs surfaces for advanced CMOS devices

Abstract

Wet surface treatment of InGaAs is crucial for high-performance complementary metal-oxide semiconductor (CMOS) devices as it reduces material loss and oxide formation in the InGaAs layer. In this present study, the surface chemistries of In0.53Ga0.47As during wet chemical etching and the chemical-mechanical planarization (CMP) process in acidic (HCl/H2O2/H2O mixture) and alkaline (NH4OH/H2O2/H2O mixture) solutions were investigated. Elemental oxide formation, surface termination, and stoichiometry after the chemical etching/CMP process were investigated through X-ray photoelectron spectroscopy and atomic force microscopy. In wet chemical etching, the dissolution of the InGaAs elemental oxide was more prominent in acidic HCl mixture solutions compared to alkaline NH4OH mixture solutions. It was observed that the overall surface etching was more aggressive in acidic solution, whereas the alkaline solution provided higher surface roughness (R-a, similar to 7.19 nm, scanning area of 5 mu m x 5 mu m) due to the lower dissolution capacity of indium oxide. The effects of the oxidizer and the slurry pH on the removal rate, Ra, and surface contamination were evaluated after the InGaAs CMP process. A high removal rate (similar to 110 nm/min) and considerably lower surface contamination were obtained using an alkaline slurry (pH 10). A novel InGaAs CMP slurry is developed by adding different ammonium halide salts to the alkaline slurry for improving surface roughness and removal rate. The addition of ammonium halide salts to an alkaline slurry was very effective in achieving a higher removal rate (similar to 175 nm/min) and smoother surface (R-a ˂ 0.6 nm) with lower contamination during the InGaAs CMP process.