On the way to more sustainability: Development of five Al0.25Ga0.75N atomic layer etching modes for shorter cycle times

With a view to greater sustainability in the manufacturing process of semiconductor components, a modification of the atomic layer etching (ALE) process was successfully carried out on AlGaN material. Therefore, five different ALE modes, such as full-purge, half-purge, purge-free, continuous plasma, and bias-pulsing, were compared with each other. The focus of this work is on reducing the cycle time and, thus, the overall process time, while maintaining the quality with regard to surface morphology and contamination. First, parameter optimization in terms of ion energy, chlorine flux, modification, and removal time was carried out for the half-purge mode as the standard ALE mode. As a result, the etch per cycle (EPC) remained stable and low at (0.20 ± 0.02) nm/cycle for increasing ALE cycle numbers (25, 50, and 75), with no significant increase in surface roughness of 0.3 nm. It demonstrates the high precision and controllability of the standard recipe. The comparison of the five different ALE modes showed similar low roughness values and a consistent low EPC within the optimized process parameters for the full-purge, half-purge, purge-free, and continuous plasma modes. In contrast, the bias-pulsing mode exhibited a higher EPC of (0.33 ± 0.02) nm/cycle, along with surface chlorine contamination. Taking the process time into account, the continuous plasma mode is the best choice for reducing the processing time by up to 60%. Decreasing the processing time will also reduce gas and energy consumption, which positively affects production costs and improves sustainability.