Built-in Self-Limitation of Masked Aluminum Anodization using Photoresist

AbstractThis paper reports on a simple method for wafer-scale production of precisely-shaped 2D patterns of porous anodic alumina (PAA) by masked anodization of aluminum films. The produced dielectric PAA structures, featuring cylindrical nano-pores of very high aspect ratio (>100), are useful for several applications including the production of nanowires and miniature MEMS packages. The fabrication process utilizes a photoresist mask; but to overcome the instability of the photoresist during the anodization process, special borderlines are included in the mask design. These borderlines act as self-synchronized switches for the anodization current, preventing the undesired photoresist delamination and lateral extension of the PAA structures. Employing such borderlines resulted in a reduction of the lateral extension of masked Al anodization on 200mm wafers from more than 300μm to approximately 6μm