Etch characteristics of magnetic tunnel junction stack using a high density plasma in a HBr/Ar gas (original) (raw)
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Etching Magnetic Tunnel Junction with Metal Etchers
Japanese Journal of Applied Physics, 2010
Etch performances of inductory-coupled plasma (ICP) metal etchers with several gas systems are examined under constant ion energy condition to evaluate extendibility to the 300 mm wafer magnetic tunnel junction (MTJ) etch process. The ICP-Ar sputter etch affects little on magnetic properties, and shows about the same magnetoresistive (MR) ratio with conventional Ar ion milling. Major issue is the electrical short by redeposition. The etch uniformity over the wafer and precise etch end-point detection are important. The Cl 2 addition to the ICP-Ar etch plasma shows serious pattern deformation and degradation of loop offset (H off ). Methanol (Me-OH) etch shows slightly lower MR-ratio due to material degradation. However, better H off is observed probably due to the ion protection effect by thin carbon layer over the etched surface. Dilution of Me-OH with Ar improves MR ratio. Ar/Me-OH and ICP-Ar etch processes would be the candidate for 300 mm process at present.
The damage recovery process for magnetic tunnel junctions (MTJs) after methanol-(Me-OH) based plasma etch has been demonstrated. Me-OH and O 2 plasma, which contain oxygen in the molecule, caused unavoidable modification of magnetic materials in the MTJ stack. For example, the magnetization saturation and MR ratio decreased. H 2 base reductive plasma treatment was effective in recovering from this deterioration. No harmful side effects were observed in other aspects of MTJ performance such as MTJ resistance, hysteresis loop offset, and switching field. Heavier initial damage required a longer treatment time for recovery. Other types of reductive chemistry such as NH 3 plasma deteriorated the MTJ when the treatment lasted more than 15 s, probably due to nitridation. The use of a highly selective Ar/Me-OH etch process along with He/H 2 plasma recovery treatment is very promising for the MTJs' etch process to fabricate high-density magnetic random access memory (MRAM) and non-volatile logic devices. #
Inductively coupled plasma etching of Ta, Co, Fe, NiFe, NiFeCo, and MnNi with Cl2/Ar discharges
Korean Journal of Chemical Engineering, 2004
Dry etching of the magnetic thin films such as Ta, Fe, Co, NiFe, NiFeCo, and MnNi was carried out in inductively coupled plasmas of Cl 2 /Ar mixture. All the magnetic materials went through a maximum etch rate at 25% Cl 2. The effects of the ICP source power and the rf chuck power on the etch rate and the surface roughness were quite dependent of the materials. An ion-enhanced chemical etch mechanism was important for the magnetic films. The surface roughness of the etched samples was relatively constant of the rf chuck power up to 200 W, but a rougher surface at a higher rf power was obtained. Post-etch cleaning of the etched samples in de-ionized water reduced the chlorine residues substantially.
Applied Physics Letters, 1998
Ni 80 Fe 20 tunnel junctions were grown by sputtering at room temperature on glass and Si substrates, the barrier being formed by rf sputter etching of aluminum in a Ar/O 2 plasma. The resistance is controlled for a given junction area by adjusting the oxide barrier thickness. Magnetoresistance ratios of 16% at 4.2 K and 6% at room temperature are obtained with good reproducibility over three orders of magnitude of resistance. Effects related to substrate shunting and oxidation of the bottom Co electrode are discussed.
Inductively coupled plasma etching of CoFeB, CoZr, CoSm and FeMn thin films in interhalogen mixtures
Materials Science and Engineering: B, 1999
Two new plasma chemistries (ICl and IBr) have been employed for patterning of CoFeB, CoZr, CoSm and FeMn thin films for application in magnetic memories. The interhalogen mixtures produced faster etch rates for FeMn, CoSm, and CoZr in both chemistries compared to Cl 2 plasmas under the same conditions. The etch rates are a strong function of discharge composition, pressure, ion flux and ion energy. The data are consistent with an ion-assisted desorption mechanism for the metal chloride etch products. No effect on magnetic properties of etched CoSm was detectable under our conditions. : S 0 9 2 1 -5 1 0 7 ( 9 9 ) 0 0 0 3 5 -5
Japanese Journal of Applied Physics, 2012
The comparative study of etching characteristics and mechanisms for TiO 2 thin films in CF 4 ? Ar, Cl 2 ? Ar and HBr ? Ar inductively coupled plasmas was carried out. The etching rates for TiO 2 , Si and photoresist were measured as functions of gas mixing ratios at fixed gas pressure (10 mTorr), input power (800 W) and bias power (300 W). It was found that the maximum TiO 2 etching rate of *130 nm/min correspond to pure CF 4 plasma while an increase in Ar fraction in a feed gas results in the monotonic non-linear decrease in the TiO 2 etching rates in all three gas mixtures. Plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling supplied the data on the densities of plasma actives specie as well as on particle and energy fluxes to the etched surface. It was concluded that, under the given set of experimental conditions, the TiO 2 etching kinetics in all gas systems correspond to the ion-assisted chemical reaction with a domination of the chemical etching pathway. It was found also that the differences in the absolute TiO 2 etching rates correlate with the energy thresholds for TiO 2 ? F, Cl or Br reaction, and the reaction probabilities for F, Cl and Br atoms exhibit the different changes with the ion energy flux according to the volatility of corresponding etching products.
Investigation on etch characteristics of MgO thin films using a HBr/Ar plasma
Thin Solid Films, 2011
Ti hard mask Magnetic tunnel junction Inductively coupled plasma reactive ion etching HBr/Ar gas Etch characteristics of MgO thin films were investigated using an inductively coupled plasma reactive ion etcher in a HBr/Ar plasma. As the concentration of HBr gas increased, the etch rate of MgO thin films gradually decreased, but the etch rate of Ti hard mask showed initial decrease and then increased with increasing HBr concentration. The etch profile of MgO films was improved with increasing HBr concentration and a high degree of anisotropy in etch profile was achieved at 30% HBr/Ar gas. Based on the etch characteristics and surface analysis by X-ray photoelectron spectroscopy, it can be concluded that the etch mechanism of MgO thin films in a HBr/Ar gas does not follow the reactive ion etch mechanism but the sputter etching mechanism with the assistance of chemical reactions on the film surfaces.
Plasma etching: principles, mechanisms, application to micro- and nano-technologies
2000
Nowadays, plasma-etching processes are asked to produce patterns from the nanometer to the micrometer range with the same efficiency. The very severe requirements in terms of etch rate, selectivity, profile control and surface damage plasma-etching processes lead to, have been at the origin of the development of mechanistic studies by means of plasma diagnostics and surface analysis, as well as the development of new etching devices. We review here the basic concepts of plasma etching, and using examples, we describe more in details important features. We recall, in particular, the important role of the surface layer, the ion bombardment and the substrate temperature. q