Effects of spacer layer elastic properties on metallic thin film edge-induced stress gradients in bubble memory devices

Abstract

It is well-known that metallization edge-induced stresses can change the uniaxial magnetic anisotropy of a liquid phase epitaxial (LPE) garnet film near the metallization edge. We have investigated this magnetostrictive interaction of patterned metallic films with ion-implanted LPE films by using several different spacer layers such as polyimide, SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , and combinations of polyimide and SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> beneath a Cr-Cu-Cr conductor pattern. It is concluded that the stress eliminating capability of a spacer depends on the hardness parameter <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K = \frac{E_{s}(1-\nu\min{f}\max{2})}{E_{f}(1-\nu\min{s}\max{2})}</tex> where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_{s} , E_{f}</tex> are Young's moduli and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\nu_{s}, \nu_{f}</tex> are Poisson's ratios for the spacer and metallic film, respectively. The polyimide spacer with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E_{s} &lt; 10^{11}</tex> dyn/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K \leq 0.1</tex> transmits an order of magnitude of smaller stress than a SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> spacer with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K \geq 1</tex> with the stress being more uniformly distributed across the spacer.