Investigation of Reactive Ion Etching Processes on Mg-Based Oxide Semiconductors: MgZnO

Mg-based oxide semiconductors, like MgZnO, hold significant potential for advanced memory and electronic applications. However, achieving damage-free patterning of this material at nanoscale while preserving its electrical properties remains a considerable challenge. This study investigates the etching mechanism of MgZnO using the reactive ion etching (RIE) method with a Cl2, CH4, and Ar-based gas chemistry. The etch byproducts consist of volatile components like Zn(CH3)2 and nonvolatile metal chlorides of Mg and Zn. As a result, the patterning process combines both physical and chemical etch mechanisms. When applied on as-deposited MgZnO layers, the etch process did not significantly impact surface composition and roughness (∼1 nm). In addition, the preservation of inherent electrical properties, such as the breakdown electric field, was evaluated. When these optimized etching conditions were applied to line/space MgZnO patterns at a scaled 90 nm pitch, challenges such as redeposition on feature sidewalls and residue formation on the field were encountered. These issues were effectively mitigated by implementing a cyclic RIE process with O2 plasma exposure. To our knowledge, this study represents a significant advancement toward the controlled patterning of MgZnO. It offers valuable insights into the etching mechanisms of oxide semiconductors for high-density memory applications, particularly those that generate both volatile and nonvolatile byproducts.