Magnetization losses in submicrometer CoFeB dots etched in a high ion density Cl2-based plasma

Abstract

Faceting of the etch masks and chlorinated etch residues can reduce the magnetization of patterning magnetic materials substantially, and therefore, constitutes a considerable concern. To get more insight into the magnetization losses, CoFeB dots were etched in a high ion density Cl2-based plasma with a width ranging from 0.3to6.4μm. The magnetic properties of the CoFeB dots were measured by magnetometry. Submicrometer CoFeB dots showed significant magnetization reductions despite H2O rinsing. Scanning electron microscopy (SEM) studies revealed that etching in a Cl2-based plasma caused faceting of the masks, leading to sloped sidewalls. SEM pictures were used to determine the geometric volume, which was compared to the effective magnetic volume resulting from the magnetometry measurements. The SEM data are in good agreement with the magnetometry data, and a chloride penetration depth of only a few nanometers could be derived, indicating that the postetch rinsing is sufficient to prevent considerable corrosion of the CoFeB dots.

Etch Characteristics of Magnetic Tunnel Junction Materials Using Bias Pulsing in the CH<SUB>4</SUB>/N<SUB>2</SUB>O Inductively Coupled Plasma

“…However, MTJ-related materials do not easily form the volatile compounds at low substrate temperatures and, for conventional halogen-based etch gases, corrosion of etched MTJ stack tends to occur during the etching. [10][11][12] Therefore, these materials have been etched by physical sputtering rather than conventional reactive ion etching methods. For the etching of MTJ materials, etch residue is formed on the sidewall of the etched MTJ stack due to the low volatility and it leads to a leakage current path during the operation of MRAM devices.…”