Preparation of Ba-ferrite films for perpendicular magnetic recording by RF targets facing type of sputtering

Abstract

A rf Targets Facing Type of Sputtering(rf-TFTS) apparatus was used to deposit hexagonal magnetoplumbite type of Ba ferrite (BaO.6Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> : BaM) films with c-axis orientation at high rate. Although high rate sputtering of BaM was possible under stable conditions in rf-TFTS, the film composition changed drastically with total gas pressure P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">total</inf> and input power P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</inf> during sputtering. These changes in film composition corresponded well to the change in the potential difference Vd between plasma and wall, that is, the deficiency in Ba content in the films increased as V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> increased. These results indicate that the change in composition is caused by ion bombardment of the substrate during sputtering (i.e., Ba atom is resputtered preferencially), since the ions in plasma can bombard the substrate with energy about e.V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> . The value of V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> decreases as P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">total</inf> or P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</inf> increases and the BaM films with stoichiometric composition were obtained at high P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">total</inf> or at high P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</inf> . Therefore, sputtering must be performed under the condition of high sputtering power or of high sputtering gas pressure, where V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> becomes small, to deposit stoichiometric BaM films.