Electrodeposition on Ni from a Sulfamate Electrolyte Part 1: Effect of a Stress Relief on Annealing Behavior and Film Metallurgy

Abstract

Ni and Ni alloys are being developed as baseline materials for LIGA technology and prototyping at Sandia National Laboratories. A conventional, additive-free sulfamate electrolyte has been chosen for pure Ni electrodeposition due to its simplicity and ability to produce ductile, low-stress films. When depositing certain Ni alloys, saccharin is typically employed as an electrolyte bath additive. While saccharin is well known and effective as a stress reliever, it has a significant impact on the microstructure of the deposit and its annealing behavior.The electrodeposition of pure Ni in the presence of saccharin is studied here to understand its effects in the absence of an alloying element (such as Co or Fe). The grain structure and Vickers hardness of Ni deposited with and without saccharin on a rotating disk electrode were all found to be consistent with previous studies available in the literature. The following observations were made:1) The fine, columnar morphology obtained without saccharin became an equiaxed, nanosized grain structure with saccharin (from ~1.5 mm to ~40 nm nominal grain size, respectively). The grain refinement resulting from saccharin is not accompanied with an increase in film stress, in contrast to the grain refinement associated with certain Ni alloys. 2) A change in the deposit texture from weak (210) to (111) along the film growth direction with the addition of saccharin. 3) An increase in Vickers hardness by a factor of ~2 (from ~170 to ~320) upon the addition of saccharin. 4) A rapid decrease in hardness with annealing from the high, as-deposited values for films deposited with saccharin to a value lower than that of annealed Ni from an additive-free bath. 5) Accelerated grain growth during annealing for films deposited with saccharin; this has not been observed previously in the literature to the authors' best knowledge. 4ACKNOWLEDGMENT

Photoresist Deposition and Nickel Electrodeposition for Metallic Substrate Microfabrication with Nickel Lines

“…The electrolytic solution is the key to the nickel electrodeposition technique. The electrolyte composition of the nickel electrodeposition solution is also known as Nickel Sulfamate Solution [6]. The elements and concentrations of an electrolytic solution varied according to the needs of the research group.…”

“…Saccharin reduces stress levels at the master [15]. Sodium dodecyl sulfate (SDS) improves the high-resolution detail, avoids stress level, and avoids deformation at the electrodeposited material [6].…”