| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS+TF-MoA |
| Session: | Plasma Deposition |
| Presenter: | H. Li, Osaka University, Japan |
| Authors: | H. Li, Osaka University, Japan Y. Muraki, Osaka University, Japan K. Karahashi, Osaka University, Japan S. Hamaguchi, Osaka University, Japan |
| Correspondent: | Click to Email |
Based on highly developed reactive ion etching (RIE) technologies, micro-fabrication of Si-based semiconductor devices has been considerably developed for the last few decades. However, as non-conventional micro devices, such as magnetic random access memory (MRAM) devices, have been developed recently, there has been a considerable demand for RIE processes of non-conventional materials such as magnetic materials with nonconventional gases such as CO/NH3 and methanol. In this study, we examine sputtering yields and surface reaction characteristics for MRAM etching by CO/NH3 or methanol plasmas. Especially we focus on effects of oxygen and nitrogen in incident ions that are likely to induce selectivity of magnetic materials over Ta, i.e., a widely used mask material in such processes. In this study, we use a multi-beam system (i.e., mass-selected ion beam system), which allows only selected ions with specified energy to be injected into a sample substrate set in an ultra-high-vacuum (UHV) chamber. Using the beam system, rather than an actual plasma etching system, we can examine specific surface reactions caused by a specific combination of a sample material and incident ions (and/or radicals). In the beam system, chemical surface compositions are analyzed by in-situ XPS. In this study, the incident ion energy and angle of incidence were varied from 300eV to 1000eV and from 0° to 75 ° . The sputtering yields were measured as functions of energy and/or angle of incidence for various materials including Ni, Fe, Co, Ta, and TaOx . It has been found that, in most cases, etching processes for these materials are nearly of physical sputtering. For simple physical sputtering (by, e.g., Ar+ ions), the sputtering yield of Ta is much lower than the magnetic materials (Ni, Co, Fe), which justifies the use of Ta as a mask material. Furthermore, from XPS spectrum observation, it has been found that, when N or O are in the incident ionic species, Ta form a nitride or an oxide and its sputtering yield becomes even lower. These results have confirmed that, in CO/NH3 or methanol plasma etching processes of magnetic materials with Ta masks, the observed selectivity is essentially caused by the formation of hard-to-etch oxides and/or nitrides of masks, rather than enhanced etching yields of magnetic materials by these plasmas.