Chemical etching was used for selective patterning of magnetic soft (or free) layers, principally Permalloy, in MRAM stacks. Passive films formed in the prior cap layer patterning step played a critical role in the etching behavior of the magnetic layers. The novel use of a sulfur-based additive to inhibit Permalloy passivation, thus enabling selective etching in weak acid etchants, was demonstrated. Aqueous etch solutions of
-dicarboxylic acids were found to etch Permalloy films whose surfaces contained a chemisorbed, sulfur-based, passivation inhibitor, but left the alumina tunnel barrier intact. High values of array quality factors for magnetic switching were demonstrated for chemically etched arrays of Permalloy elements.
By: E. J. O'Sullivan, D. W. Abraham, A. G. Schrott
Published in: RC23232 in 2004
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