Investigation on Etch Characteristics of Nanometer-Sized Magnetic Tunnel Junction Stacks Using a HBr/Ar Plasma

Kim, Eun Ho; Xiao, Yu Bin; Kong, Seon Mi; Chung, Chee Won

doi:10.1166/jnn.2011.4483

Cited by 14 publications

(4 citation statements)

References 6 publications

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“…However, the key problem encountered is the material degradation, Cl x species absorbed on the side-walls inducing corrosion of the CoFeB layer 5 . E.H. Kim et al 9 studied the etching of MTJ stacks in HBr/Ar plasma's. They report a benifical effect of adding HBr to Ar plasma's, resulting in more anisotropic profiles.…”

Section: And Br Based Plasma Etch Chemistriesmentioning

confidence: 99%

STT MRAM patterning challenges

Boullart

Radisic

Paraschiv³

et al. 2013

SPIE Proceedings

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In this paper we report on the patterning challenges for the integration of Spin-Transfer Torque Magneto-ResistiveRandom-Access Memory (STT MRAM). An overview of the different patterning approaches that have been evaluated in the past decade is presented. Plasma based etching, wet echting, but also none subtractive pattering approaches are covered. The paper also reports on the patterning strategies, currently under investigation at imec.

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Section: And Br Based Plasma Etch Chemistriesmentioning

confidence: 99%

STT MRAM patterning challenges

Boullart

Radisic

Paraschiv³

et al. 2013

SPIE Proceedings

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“…HBr inductively coupled plasma (ICP) has been used to etch various materials such as C, 1) Pb(Zr x Ti 1Àx )O 3 (PZT), 2) GaN, 3) indium tin oxide (ITO), 4,5) gallium indium zinc oxide (GIZO), 6) Mo, 7) CoFeB, 8) SiC, 9,10) ZnO, 11) Al-Nd, 12) InP, [13][14][15] Pt, 16) and Al 2 O 3 . [17][18][19] Most of all, HBr ICP has been extensively used for the selective etching of Si owing to its good anisotropy, high etching rate, and high selectivity in the reactive ion etching (RIE) process, and has been intensively investigated by many groups.…”

Section: Introductionmentioning

confidence: 99%

Influence of Oxygen Addition and Wafer Bias Voltage on Bromine Atom Surface Reaction in a HBr/Ar Inductively Coupled Plasma

Iino

Nojiri

Suzuki

et al. 2013

Jpn. J. Appl. Phys.

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The influence of the wafer surface material and wafer bias voltage on the Br radical density in HBr/Ar and HBr/Ar/O2 inductively coupled plasmas was investigated by appearance mass spectrometry. By increasing the bias voltage, a monotonic decrease in the Br radical density was observed irrespective of the surface material (Si, Al2O3) of the wafer. A drastic increase in Br radical density was observed after O2 addition to HBr/Ar plasma in the case of a bare Si wafer, whereas almost the same density was observed in the case of an Al2O3-sputtered Si wafer. X-ray photoelectron spectroscopy (XPS) analysis indicated that O2 addition promotes oxide formation on the Si surface. Measurement of the decay time constant for a Br radical after turning off the plasma indicated that O2 addition results in a longer decay time constant, suggesting the decrease of the surface loss probability of Br radicals for the surface-oxidized Si surface.

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“…[1][2][3][4] Generally, good etch profiles and fast etch rates of the MTJ stacks are achieved via formation of volatile etch byproducts that can be easily sputtered off. However, this particular gas chemistry has several drawbacks, such as the high toxicity of halogen gases, post etch corrosion and subsequent magnetization loss.…”

mentioning

confidence: 99%

Inductively Coupled Plasma Reactive Ion Etching of Magnetic Tunnel Junction Stacks in a CH3COOH/Ar Gas

Garay

Choi

Hwang

et al. 2015

ECS Solid State Letters

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The etch characteristics of hard masked MTJ (Magnetic Tunnel Junctions) stacks were investigated using inductively coupled plasma reactive ion etching in a CH 3 COOH/Ar gas mixture as a function of gas mixture concentration and etch time. A high degree of anisotropy in the etch profile and fast etch rates were achieved when the MTJ stacks were etched in the CH 3 COOH/Ar gas mixture. When etched in 25% CH 3 COOH for 3 min, a stack: space ratio of 1:1 was obtained and EDS analysis showed no significant redeposition along the sidewall. A high degree of anisotropy was accomplished without redepositions or etch residues.Magnetic tunnel junction (MTJ) stacks etching in halogen containing gas mixtures (Cl 2 /O 2 /Ar, BCl 3 /Ar and HBr/Ar) was previously reported. 1-4 Generally, good etch profiles and fast etch rates of the MTJ stacks are achieved via formation of volatile etch byproducts that can be easily sputtered off. However, this particular gas chemistry has several drawbacks, such as the high toxicity of halogen gases, post etch corrosion and subsequent magnetization loss. 4,13 Recent studies have focused on developing etching processes that employ non corrosive gas mixtures containing C, H, O and N, such as CO/NH 3 , CH 3 OH/Ar, CH 3 OH/H 2 O, CH 4 /Ar and CH 4 /O 2 /Ar. 5-12 MTJ stacks etching in such non corrosive gas mixtures mainly proceeds via oxidation of metals in the MTJ stack that compose each layer, formation of a protective layer and ion bombardment, which enables moderate etch rates and good etch profiles without any post etch degradation of the MTJ stacks. However, the lack of chemically reactive species in the plasma chemistry that can produce volatile etch byproducts results in heavy sidewall redeposition under certain conditions. Ion bombardment induced etch damage is also a major concern. 12 The main goal of this study was to introduce CH 3 COOH as an alternative gas for MTJ stacks etching and investigate the inductively coupled plasma reactive ion etching (ICPRIE) characteristics of MTJ stacks in a CH 3 COOH/Ar gas mixture. MTJ stacks were prepared by direct-current (dc) magnetron sputtering on a SiO 2 /Si substrate. The structure of the MTJ stacks used in this study was W(70)/TiN(100)/Ru(5)/CoFeB(2)/MgO(0.8)/ CoFeB(1.5)/Ru(0.8)/CoFe(1.5)/PtMn(15)/TiN(45)/Oxide (nm unit), among which W (70) and TiN (100) were employed as hard masks. The hard mask layers were patterned by E-beam lithography using a negative E-beam resist, then etched by ICPRIE using a Cl 2 /C 2 F 6 /Ar gas mixture. The final patterns were 90 × 90 nm 2 square array stacks of a 1:1 ratio between stacks.The MTJ stacks were etched using a conventional ICPRIE system (A-Tech System, Korea) equipped with a main chamber and a load lock chamber. Liquid CH 3 COOH (Sigma-Aldrich 99.9% purity) was evaporated using a bubbler, and a line heating system was employed to prevent condensation. CH 3 COOH vapor was fed into the main chamber with Ar gas as the etch gas. The etch rate and etch profiles of the MTJ stacks were examined under varying con...

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Investigation on Etch Characteristics of Nanometer-Sized Magnetic Tunnel Junction Stacks Using a HBr/Ar Plasma

Cited by 14 publications

References 6 publications

STT MRAM patterning challenges

STT MRAM patterning challenges

Influence of Oxygen Addition and Wafer Bias Voltage on Bromine Atom Surface Reaction in a HBr/Ar Inductively Coupled Plasma

Inductively Coupled Plasma Reactive Ion Etching of Magnetic Tunnel Junction Stacks in a CH3COOH/Ar Gas

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