Electrochemical Aspects of the Beveling of Sputtered Permalloy Films

Abstract

For the production of thin film magnetic heads, beveled steps in sputtered Permalloy films have been made using a duplex layer chemical etching technique. In this work, special attention was paid to galvanic interaction between the Permalloy base layer and the top layer metal, titanium. By changing the concentration of the etchant, the beveling angle α could be varied between 6° and 40°. The fact that (i) the rest potential of the bimetallic system lies in a region of the anodic polarization curve for titanium, in which the metal dissolution rate is almost completely independent of potential but strongly dependent on concentration, and (ii) the etch rate of Permalloy is insensitive to concentration, is important in this application. Values of α calculated on the basis of electrochemical measurements agree favorably with values found in chemical etching experiments. Factors that influence the beveling process when, as in the present case, a metal is used as the top layer to etch another metal are discussed.