Hard Mask Strategies in Nanoscale Patterning of Mg-Based Oxide Semiconductors: Implications for Advanced Device Architectures

Achieving high-fidelity feature transfer of compositionally complex Mg-based oxide semiconductors like magnesium zinc oxide (MgZnO) requires not only precise control of MgZnO etching but also optimized hard mask (HM) engineering. The integrity of the HM is highly dependent on both the material of the HM selected and the etching mode employed for patterning MgZnO. In this study, first, we compared the performance of silicon oxide/titanium nitride (SiO 2 /TiN) and silicon nitride/ruthenium (SiN/Ru) HMs under two different etching mechanisms of MgZnO: reactive ion etching (RIE) and atomic layer etching (ALE). While Ru exhibits superior chemical stability compared to TiN under both RIE and ALE modes, it remains susceptible to profile rounding under the extended duration of ALE. To mitigate this degradation, we implement a pulsed plasma atomic layer etching (PALE) approach to preserve HM geometry while not compromising on the quality of the etching process for MgZnO. Our results show that PALE is a highly synergistic process and significantly reduces the erosion of the Ru HM and even has an impact on improving the nanoscale feature dimensions of MgZnO line/space patterns at a tight pitch of 90 nm. These findings highlight that SiN/Ru HM engineering, in combination with the use of the PALE approach for nanoscale patterning of MgZnO, is a promising strategy for achieving Mg-based oxide semiconductors at sub-100 nm pitches in advanced device applications, including transistors, high-density memory, light-emitting diodes, and UV photodetectors.