Pulse reverse plating for uniform nickel height in zone plates

Abstract

Nickel soft x-ray zone plates are fabricated by through-mask electroplating. The authors report on how a uniform nickel thickness can be obtained over the entire zone plate using pulse and pulse reverse plating. If the plating is carried out at a constant current the nickel thickness has been observed to decrease with radius. This results in lower outer zones and reduced diffraction efficiency in the outer parts of the zone plates. Here they show that the height profile can be controlled by adjusting the current density of the pulses. A high current density is found to primarily affect the edges while a low current density was observed to affect the central parts of the structures. This is true for both cathodic and anodic currents, which means that local plating and dissolution rates can be adjusted to obtain a uniform mass distribution.