Applications of Novel High-Aspect-Ratio Ultrathick UV Photoresist for Microelectroplating

The new acrylic photoresist named AZ 125 nXT is a serious option for low-cost high-aspect-ratio UV LIGA applications. It offers advantages compared to SU-8 like good adhesion to Si substrates, rapid processing, and easy removal after electroplating. Film thicknesses of 400, 800, and 1400 μm with an aspect ratio of 20 : 1 have been shown by the authors. The photoresist's excellent electroforming behavior has been proved in an extremely acid copper electrolyte at room temperature as well as in an almost neutral nickel electrolyte at 50°C. The easy removal (wet: dimethyl sulfoxide or acetone, dry: plasma with reactive radicals) releases freestanding metal structures with aspect ratios of 13 : 1 and 16 : 1.