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

Abstract

Reactive and anisotropic etching of magnetic tunnel junction (MTJ) stacked films has been achieved using pulse-time-modulated (TM) plasma. While corrosion and delamination of MTJs are observed in continuous wave discharge plasma, a chlorine pulse-time-modulated plasma achieved a high MTJ etching rate without corrosion or delamination. The authors think that the negative ions enhance the chemical reactions on the surface of magnetic films. The magnetic characteristics are also significantly improved by using TM plasma because of reduced residues and improved tapered profiles. Accordingly, TM plasma etching is a promising candidate for high-rate and damage-free MTJ etching for magnetoresistive random access memory devices.

Authors:
; ; ;  [1];  [2];  [2]
  1. Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8557, Japan and System Devices Research Laboratories, NEC Corporation, 1120 Shimokuzawa, Sagamihara 229-1198 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
20979364
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films; Journal Volume: 25; Journal Issue: 3; Other Information: DOI: 10.1116/1.2712192; (c) 2007 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANIONS; ANISOTROPY; CHLORINE; CORROSION; ETCHING; FERROMAGNETIC MATERIALS; IRON ALLOYS; MAGNETORESISTANCE; NICKEL ALLOYS; PLASMA; SUPERCONDUCTING JUNCTIONS; SURFACES; THIN FILMS; TUNNEL EFFECT

Citation Formats

Mukai, Tomonori, Ohshima, Norikazu, Hada, Hiromitsu, Samukawa, Seiji, System Devices Research Laboratories, NEC Corporation, 1120 Shimokuzawa, Sagamihara 229-1198, and Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8557. Reactive and anisotropic etching of magnetic tunnel junction films using pulse-time-modulated plasma. United States: N. p., 2007. Web. doi:10.1116/1.2712192.
Mukai, Tomonori, Ohshima, Norikazu, Hada, Hiromitsu, Samukawa, Seiji, System Devices Research Laboratories, NEC Corporation, 1120 Shimokuzawa, Sagamihara 229-1198, & Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8557. Reactive and anisotropic etching of magnetic tunnel junction films using pulse-time-modulated plasma. United States. doi:10.1116/1.2712192.
Mukai, Tomonori, Ohshima, Norikazu, Hada, Hiromitsu, Samukawa, Seiji, System Devices Research Laboratories, NEC Corporation, 1120 Shimokuzawa, Sagamihara 229-1198, and Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8557. Tue . "Reactive and anisotropic etching of magnetic tunnel junction films using pulse-time-modulated plasma". United States. doi:10.1116/1.2712192.
@article{osti_20979364,
title = {Reactive and anisotropic etching of magnetic tunnel junction films using pulse-time-modulated plasma},
author = {Mukai, Tomonori and Ohshima, Norikazu and Hada, Hiromitsu and Samukawa, Seiji and System Devices Research Laboratories, NEC Corporation, 1120 Shimokuzawa, Sagamihara 229-1198 and Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8557},
abstractNote = {Reactive and anisotropic etching of magnetic tunnel junction (MTJ) stacked films has been achieved using pulse-time-modulated (TM) plasma. While corrosion and delamination of MTJs are observed in continuous wave discharge plasma, a chlorine pulse-time-modulated plasma achieved a high MTJ etching rate without corrosion or delamination. The authors think that the negative ions enhance the chemical reactions on the surface of magnetic films. The magnetic characteristics are also significantly improved by using TM plasma because of reduced residues and improved tapered profiles. Accordingly, TM plasma etching is a promising candidate for high-rate and damage-free MTJ etching for magnetoresistive random access memory devices.},
doi = {10.1116/1.2712192},
journal = {Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films},
number = 3,
volume = 25,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • Reactive ion beam etching of ZnSe and ZnS epitaxial films was carried out using pure Cl{sub 2} as an etching gas. Electron cyclotron resonance plasma was excited at pressures of 2.5{times}10{sup {minus}4} --2.5{times}10{sup {minus}3} Torr. Chlorine ions were extracted with voltages of 0--400 V. Sputtering yields were strongly dependent on the extraction voltage and the gas pressure. The etching mechanism starts with the generation of chloride compounds, mainly ZnCl{sub {ital x}}, by the chemical reaction of the surface and chlorine radicals, mainly Cl atoms. The chloride compounds are subsequently sputtered off by the accelerated ion beam. The crystalline quality ofmore » etched ZnSe films was characterized by photoluminescence measurements. We found that high quality etched films, which have almost no damage and no Cl contamination, can be obtained at an extraction voltage of about 300 V.« less
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  • A modulated stripe width structure (MSW) has been applied to a GaAlAs/GaAs distributed feedback buried heterostructure laser to obtain complete single longitudinal mode oscillation. An MSW device having a gradual modulation scheme and antireflecting films on the cleaved facets has been fabricated using reactive ion etching (RIE). Principal results include realization of a reactive ion etched second-order grating with the grooves as deep as 0.15 ..mu..m after regrowth and a modulated stripe having extremely fine definition made possible by RIE. The device had a spectrum which agreed markedly well with an analytical result. The effective functioning of the MSW structuremore » has thereby been confirmed experimentally.« less
  • In this study, the CoFe thin film was studied using an inductively coupled plasma system in CH{sub 4}-based gas chemistries. The etch rate of the CoFe thin film was systemically studied by the process parameters including the gas mixing ratio, the rf power, the dc-bias power, and the process pressure. The best gas composition for etching was in CH{sub 4} (20%)/Ar (80%) ratio. As the rf power and the dc-bias voltage were increased, the etch rate of the CoFe thin film increased in a CH{sub 4}/Ar inductively coupled plasma system. The best process pressure condition for etching was 10 mTorrmore » in the CH{sub 4}/Ar inductively coupled plasma system. The changes in the components on the surface of the CoFe thin film were investigated with energy dispersive x ray.« less
  • A technique for anisotropically etching fine line patterns in aluminum films using the gas combination Cl{sub 2}:BCl{sub 3}:CH{sub 4} is explored. The process is designed to avoid the use of CCl{sub 4} and CHCl{sub 3}, both of which are known to be strong carcinogens. The etch is characterized by making use of statistically designed experiments to optimize the etch rate, selectivity, and anisotropy of the etch. The etching mechanism is explored by the use of Auger electron spectroscopy to study polymer sidewall deposits, caused by the use of CH{sub 4} and an organic mask, which prohibit undercutting. Using this etch,more » the authors have demonstrated the anisotropic etching of fine line features in Al films with minimum lines and spaces of 500 and 300 nm, respectively.« less