Etching of Magnetic Tunnel Junction Materials Using Reactive Ion Beam

Abstract

Magnetic tunnel junction (MTJ) materials such as CoPt, CoFeB, and MgO and the hard mask material such as W were etched with a reactive ion beam system using Ar, NF 3 , CH 3 OH, and CO/NH 3 as etch gases. The effects of etch gas and the energy of the ion beam on the etch characteristics were then investigated. When the MTJ materials were etched with an Ar ion beam, the etch selectivities of the MTJ materials over W and the etch profiles of the etched MTJ patterns masked with W were generally poor, possibly due to the nonselective etching, physical sputtering without chemical reaction, and severe redeposition of the nonvolatile etch residues on the sidewall of the etched features. The use of NF 3 → CH 3 OH → CO/NH 3 reactive ion beam showed better etch selectivities over W and better etch profiles due to the higher etch selectivities of MTJ materials over W and less sidewall deposition. For reactive gases such as CH 3 OH and CO/NH 3 , the use of higher ion energy by increasing the 1st grid voltage of the ion beam up to +250 V also improved the MTJ etch profiles, possibly due to the increased effective chemical assisted physical sputtering of the etch products and the minimization of sidewall etch residues by removing etch products more effectively.

Progress and prospects in nanoscale dry processes: How can we control atomic layer reactions?

“…The etching of metals also has the problem of the redeposition of etching by-products. 12,[188][189][190][191][192][193][194][195][196][197] In self-limiting formation, another difficulty arises for intermetallic compounds or alloys such as CoFe, NiFe, CrFe, and PtMn. Simply, in etching processes for compounds such as high-k materials, dichalcogenides, GaAs, GaP, and GaN, it is difficult to maintain the surface stoichiometry during and after the etching.…”

Etch characteristics of magnetic tunnel junction materials using H2/NH3 reactive ion beam

“…However, the tilting of the ion beam is limited to the etching of low density MRAM cells because the tilting of ion beam can induce a shadow effect caused by adjacent cells, especially, in the case of high density MRAM devices required for next generation STT-MRAM devices. Therefore, reactive ion beam etching (RIBE) processes using reactive gases such as CO/NH 3 instead of Ar have been investigated and, by using the RIBE without tilting the ion beam, anisotropic etch profiles of MTJ without sidewall residues could have been observed [13,14]. However, due to the use of the etch gas mixture containing oxygen, a possibility of chemical damages on the MTJ material surface during the etching and a thin oxide layer on the patterned sidewall of MTJ material still remains.…”

Photopatternable Magnetic Hollowbots by Nd-Fe-B Nanocomposite for Potential Targeted Drug Delivery Applications

“…These methods could result in good purity of magnetic materials for small samples, but they are expensive and time-consuming for large ones. Etching and cutting [ 26 ] are subtractive methods to obtain magnetic microstructures. These methods can achieve good density of magnetic materials, but lack in precision.…”