Superconformal Electrodeposition of Co and Co–Fe Alloys Using 2-Mercapto-5-benzimidazolesulfonic Acid

Superconformal Co(Fe) filling of submicrometer trenches by electrodeposition is demonstrated in the presence of 2-mercapto-5-benzimidazolesulfonic acid (MBIS). MBIS inhibits the initiation of Co deposition. Inhibition breakdown is characterized by hysteretic voltammetry and rising chronoamperometric transients. The positive feedback process reflects the competition between MBIS adsorption and its desorption, and consumption, with the latter being closely coupled with proton reduction and the metal deposition reaction. Void-free Co trench filling proceeds by preferential metal deposition at the bottom corners leading to a V-notch interface shape that is followed by geometrical leveling. Void-free filling is also demonstrated for a via geometry. Almost identical superconformal trench filling is obtained for Co-rich Co–Fe alloys. Analytical transmission electron microscopy and energy dispersive X-ray analysis indicate that the Fe/Co ratio within the filled trenches is uniform. MBIS does not significantly perturb the magnetic properties of the Co or Co–Fe alloy deposits.