Atomic layer etching of sputter-deposited AlN in Cl2-Ar plasmas

Aluminum nitride (AlN) is a widely used material in micro- and nanoelectronics. However, one of the challenges in the fabrication of AlN-based devices is achieving precise nanoscale etching while maintaining smooth surface and well-defined etch profile. Atomic Layer Etching (ALE) is a promising approach to address these challenges.



This study investigates the ALE of AlN thin films deposited via sputter deposition. The experiments were performed in an Applied Materials™ Centura™ DTM Chamber using Cl₂ and Ar gases for the modification (Cl step) and ion bombardment (Ar step) steps, respectively.



The feasibility of ALE for sputter-deposited AlN thin films was successfully demonstrated. The etch per cycle (EPC) was found to be approximately a single monolayer of the wurtzite AlN crystal structure. The ALE energy window was determined by analyzing the IEDFs in the Ar step, revealing the energy range of around 75 eV, which is consistent with the previously reported data in the literature [1]. Moreover, it was determined that the process is linear, e.g. the EPC is constant against the number of cycles. The AlN RMS roughness after processing within the ALE energy window is around 570 pm, which is lower than the as-grown material roughness of 3 nm.



[1] T. Faraz, Y. G. P. Verstappen, M. A. Verheijen, N. J. Chittock, J. E. Lopez, E. Heijdra, W. J. H. Van Gennip, W. M. M. Kessels, and A. J. M. Mackus, Precise ion energy control with tailored waveform biasing for atomic scale processing, Journal of Applied Physics 128, 213301 (2020).