Width of Anodization Mask Required to Preserve a Metallic Phase during Porous-Type Anodization of Aluminum-Copper Films

Patterned arrays with alternating regions of the metallic phase and porous aluminum oxide are fabricated by using a dense layer of barrier aluminum oxide as a mask for porous-type anodization of 99.5% Al and 0.5% Cu films. The pore curvature at the interface between the metallic phase and porous aluminum oxide is investigated as a function of anodization voltage. The degree of anisotropy, which is defined as a ratio between vertical and lateral propagation of pores, increases slightly as anodization voltage increases. The pore curvature compromises the mask transfer during anodization due to the lateral pore propagation under the anodization mask. For miniaturization of regions composed of Al-Cu, it is important to establish the width of anodization mask required to preserve the metallic phase between two regions of porous aluminum oxide. Our results show that a 2 μm wide anodization mask is necessary during porous-type anodization of 3 μm thick Al-Cu films at a chosen set of anodization conditions (40 V, 3% w/v H 2 C 2 O 4 , 5°C).