Reactive and anisotropic etching of magnetic tunnel junction films using pulse-time-modulated plasma

In this review, we discuss the progress of emerging dry processes for nanoscale fabrication. Experts in the fields of plasma processing have contributed to addressing the increasingly challenging demands in achieving atomic-level control of material selectivity and physicochemical reactions involving ion bombardment. The discussion encompasses major challenges shared across the plasma science and technology community. Focus is placed on advances in the development of fabrication technologies for emerging materials, especially metallic and intermetallic compounds and multiferroic, and two-dimensional (2D) materials, as well as state-of-the-art techniques used in nanoscale semiconductor manufacturing with a brief summary of future challenges.

Section: Future Challengesmentioning

confidence: 99%

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

Ishikawa

Karahashi

Ichikı

et al. 2017

“…However, this method is known to exhibit problems in the application to nanoscale MRAM integrated circuit processing due to heavy redeposition on the sidewall of the patterns, lack of selectivity, and slow etch rate. [13][14][15] Therefore, plasma etching techniques such as reactive ion etching (RIE), inductively coupled plasma (ICP) etching, etc. have been investigated as alternate techniques in improving these disadvantages.…”

Section: Introductionmentioning

confidence: 99%

A study on the etching characteristics of magnetic tunneling junction materials using DC pulse-biased inductively coupled plasmas

Yang

Jeon

Yeom

2014

The etching properties of magnetic materials composing the magnetic tunnel junction (MTJ) such as CoPt, MgO, CoFeB, and CoPt/MgO/CoFeB were investigated in DC pulse biased CO/NH 3 inductively coupled plasmas (ICPs) and their etch characteristics were compared with those etched by RF CW biased ICPs. The use of DC pulse biased ICPs instead of RF CW biased ICPs improved the etch selectivity of the MTJ materials over W and also decreased the residue on the surface of the etched materials possibly due to the more stable and volatile etch product formation during the DC pulse off time and the enhanced removal of the etch products by mono-energetic ions during the DC pulse on time. When MTJ materials masked with W were etched, more anisotropic etch profile could be also observed when the MTJ materials were etched with the DC pulse biasing of 60% duty percentage compared with those etched with RF CW biasing due to the decreased redeposition of etch products on the sidewall of the etched feature in addition to the enhanced etch selectivity over W.

“…They reported that the magnetic characteristics were also significantly improved by using the source powerpulsed plasma because of reduced residues in addition to the improvement of the etch profile. 29) Even though it was reported that the source power pulsing improved the MTJ etch characteristics, it is believed that the bias power pulsing instead of the source power pulsing can also improve the etch characteristics of MTJ materials. In this study, an RF pulse-biasing technique has been applied in the etching of MTJ materials, such as CoFeB and MgO, and W has been used as one of the hard mask materials and its effect on the etch characteristics was investigated in an ICP system using a CO/NH 3 gas mixture, which has been investigated to show high etch rates in previous studies.…”

Section: Introductionmentioning

confidence: 99%

Selective Etching of Magnetic Tunnel Junction Materials Using CO/NH₃ Gas Mixture in Radio Frequency Pulse-Biased Inductively Coupled Plasmas

Jeon

Kim

Yang

et al. 2013

The etch characteristics of magnetic tunneling junction (MTJ) materials and the etch selectivity over W have been investigated using RF pulsebiased conditions in addition to the continuous wave (CW) bias condition with a CO/NH 3 gas combination in an inductively coupled plasma system. By using a time-averaged substrate DC bias voltage condition for the RF pulse biasing, the etch rates of MTJ materials for the RF pulsebiased conditions were generally similar to those etched using the CW RF bias condition even though the etch rates were slightly decreased with decreasing the duty percentage of the RF pulse biasing. However, the use of the RF pulse biasing improved the etch selectivity of the MTJ materials over mask materials such as W. When the surface roughness and the residual thickness remaining on the etched surface of the MTJ material such as CoFeB were investigated by using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively, it was clear that the use of the RF pulse biasing instead of CW RF biasing also decreased the residual thickness and the surface roughness. This is believed to be related to the formation of a more uniform chemically reacted layer on the etch CoFeB surface during the RF pulse-biased etching condition.