Etching behavior of Y2O3 coatings in a capacitively coupled NF3/Ar/O2 plasma: Effects of bias power and pressure

Yttrium oxide (Y2O3) has been widely used as a protective coating for the inner surfaces of semiconductor process chambers. In NF3-containing plasmas, corrosion may cause coating thinning and surface morphology reconstruction, thereby affecting in-service reliability. To elucidate the etching mechanism of Y2O3 coatings in NF3/Ar/O2 plasmas, the effects of the RF bias power and the pressure on the etching behavior are investigated in a dual-frequency (60 MHz + 400 kHz) capacitively coupled plasma. The results show that, with increasing bias power, the samples gain weight at a low bias power, while they start to lose weight at a higher bias power, and the weight loss rate increases with further increase in bias power. The surface morphology evolves from “cracks” to a “honeycomblike” structure and then tends to flatten. When the bias power is fixed at 500 W, the weight loss rate is maximized at 30 mTorr within the pressures investigated here. Shallow craterlike features are observed on the surfaces etched at 10 and 30 mTorr, accompanied by a tendency for the crack regions to become flattened. In contrast, at 50 mTorr, the surface crack morphology is similar to the original sample. These results indicate that the bias power and the pressure affect the weight loss behavior and morphology evolution of Y2O3 coatings by altering the F-radical concentration as well as the ion energy and flux onto the substrate. These findings provide an experimental reference for selecting the process parameters of Y2O3 protective coatings in NF3 plasmas for semiconductor etching.