Etch rates 5000 A min were obtained for Cu in electron cyclotron resonance C12/Ar discharges at a sample temperature of 200°C for ion-neutral ratios 0.02. The rates are a strong function of ion-neutral ratio, ion flux, and ion energy through the need to have CuCl desorption rate faster than the CuCl, generation rate in order to avoid formation of a chlorinated selvedge layer. Postetch, in situ El2 plasma cleaning removes most of the chlorine residues and allows creation of clean, anistropic Cu features.

Thin films of the ferromagnetic Heusler alloy NiMnSb, of interest for magnetic multilayer devices because of their predicted half-metallic (i.e., 100% spin-polarized) transport properties, have been successfully deposited by rf magnetron sputtering from a single composite target. A novel combination of low argon gas pressure, low deposition rates, and moderate substrate temperatures (250–350 °C) are shown to result in high-quality, low-roughness polycrystalline films of the C1b-type crystal structure, with thicknesses as low as 100 Å, without the need for any post-deposition annealing. The structural properties of these films, determined by x-ray diffraction and atomic force microscopy are presented as a function of deposition conditions. The magnetic properties and resistivity are consistent with bulk MiMnSb, which suggests that they will be effective as spin-polarized conducting layers in multilayer thin-film structures.

Long term stability of dry etched magnetoresistive random access memory elementsHigh density submicron magnetoresistive random access memory (invited)A typical magnetic random access memory stack consists of NiFe/Cu/NiFeCo multilayers, sandwiched by contact and antioxidation layers. For patterning of submicron features without redeposition on the sidewalls, it is desirable to develop plasma etch processes with a significant chlorinated etch component in addition to simple physical sputtering. Under conventional reactive ion etch conditions with Cl 2 -based plasmas, the magnetic layers do not etch because of the relatively involatile nature of the chlorinated reaction products. However, in high ion density plasmas, such as inductively coupled plasma, etch rates for NiFe and NiFeCo up to ϳ700 Å min Ϫ1 are achievable. The main disadvantage of the process is residual chlorine on the feature sidewalls, which can lead to corrosion. We have explored several options for avoiding this problem, including use of in situ and ex situ cleaning processes after the Cl 2 -etching, or by use of a noncorrosive plasma chemistry, namely CO/NH 3 . In the former case, removal of the chlorine residues with in situ H 2 plasma cleaning ͑to form volatile HCl that is pumped away͒, followed by ex situ solvent rinsing, appears effective in preventing corrosion. In the latter case, the CO/NH 3 plasma chemistry produces metal carbonyl etch products, that are desorbed in the simultaneous presence of an ion flux. The etch rates with CO/NH 3 are much lower than with Cl 2 over a broad range of source powers ͑0-1500 W͒, radio frequency chuck powers ͑50-450 W͒, pressures ͑1-30 mTorr͒ and plasma compositions. We have tried substitution of CO 2 for CO, and addition of Ar to produce faster etch rates, without success. Maximum rates of ϳ300 Å min Ϫ1 for NiFe and NiFeCo were obtained with CO/NH 3 under optimum conditions. The etched sidewalls tend to be sloped because of mask erosion during plasma exposure, in contrast to the case of Cl 2 -based chemistries where the sidewalls are vertical.

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