Nanometer-sized etching of magnetic tunnel junction stack for magnetic random access memory

Park, Ik Hyun; Min, Su Ryun; Park, Wang Hyun; Shin, Kyung-Hun; Chung, Chee Won

doi:10.1016/j.jmmm.2006.01.130

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Journal of Magnetism and Magnetic Materials

2006

DOI: 10.1016/j.jmmm.2006.01.130

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Nanometer-sized etching of magnetic tunnel junction stack for magnetic random access memory

Ik Hyun Park¹,

Su Ryun Min²,

Wang Hyun Park³

et al.

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Cited by 6 publications

(1 citation statement)

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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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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

View full text Add to dashboard Cite

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Etch characteristics of magnetic tunnel junction stack using a high density plasma in a HBr/Ar gas

Min

Cho

Noh

et al. 2007

Phys. Status Solidi (c)

Self Cite

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Etch characteristics of magnetic tunnel junction (MTJ) stack masked with TiN thin films were investigated using an inductively coupled plasma reactive ion etching in HBr/Ar gas for the application of magnetic random access memory. The effect of HBr gas concentration on the etch profile of MTJ stacks was examined. As HBr gas concentration increased, the sidewall angles of etched patterns of MTJ stacks were slightly improved. The effect of etch parameters including coil rf power, dc-bias voltage, and gas pressure on the etch profile of MTJ stack was explored. At low coil rf power, low dc-bias voltage, and high gas pressure, the etching of MTJ stack displayed better etch profile. A high degree of anisotropic etching of MTJ stacks without redeposition was achieved using HBr/Ar gas at the optimized etch conditions.

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Etch characteristics of CoFeB thin films and magnetic tunnel junction stacks in a H2O/CH3OH plasma

Hwang

Garay

Lee

et al. 2014

Korean J. Chem. Eng.

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Nanometer-sized etching of magnetic tunnel junction stack for magnetic random access memory

Cited by 6 publications

References 6 publications

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

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

Etch characteristics of magnetic tunnel junction stack using a high density plasma in a HBr/Ar gas

Etch characteristics of CoFeB thin films and magnetic tunnel junction stacks in a H2O/CH3OH plasma

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