Magnetic Materials for Three-Dimensional Damascene Metallization: Void-Free Electrodeposition of Ni and Ni[sub 70]Fe[sub 30] Using 2-Mercapto-5-benzimidazolesulfonic Acid

Abstract

Superconformal filling of submicrometer trenches with electrodeposited Ni is demonstrated using a NiSO 4 -NiCl 2 -FeSO 4 electrolyte containing 2-mercapto-5-benzimidazolesulfonic acid ͑MBIS͒. The process offers the ability to build three-dimensional magnetically active structures that may be easily integrated with other state-of-the-art metallization schemes. MBIS acts to inhibit Ni͑Fe͒ electrodeposition, although under certain conditions rapid, autocatalytic breakdown accompanies the onset of Ni deposition. Optimal trench filling is associated with the positive feedback process, moderated by electrolyte internal-resistance losses, and manifests as a hysteretic voltammetric response on planar electrodes for an MBIS concentration ϳ100 mol/L. On freshly immersed substrates, trench filling is characterized by an initial period of uniform growth followed by the development of a v-notch geometry associated with transient depletion of MBIS within the recessed feature. Interestingly, the finest submicrometer features are filled while only minimal deposition occurs on the neighboring free surface. Continued growth of the MBIS derived v-notch geometry also results in void-free filling of the larger features by geometrical leveling. The same behavior is observed for soft magnetic alloys, such as Ni-rich Ni-Fe alloys. Preliminary experiments indicated that MBIS does not significantly perturb the low coercivity of Ni-Fe alloys, an important attribute for prospective technical applications.

A modified Damascene electrodeposition process for bottom-up filling of recessed surface features

“…The activation process corresponds to autocatalytic breakdown of the inhibiting layer whereby the flux of MBI required to maintain the passive state is overwhelmed by its consumption induced by metal deposition. Similar chronoamperometry has been reported for Ni and Co deposition in the presence of a sulfonated version of the molecule, known as MBIS [20,21].…”

“…After 300 s, bottom-up filling has progressed furthest in the widest features. This is in direct contrast to the effect of MBI or MBIS on Ni deposition on continuous Cu seed layers used in the conventional Damascene process [20,21]. At longer deposition times, 600 s, the growth front in the finer feature appears to catch up with bottom-up feature filling evident across trench arrays while negligible deposition occurs on the intervening free-surface areas.…”

“…In contrast, Ni deposition in the presence of inhibitors, such as PEI, MBIS and MBI, has been shown to result in transient inhibition of the metal deposition on the upper corners that makes void-free filling of sub-micrometer features possible [19][20][21].…”

“…More recently, the prospect of designing and building active, functional materials in 3D metallized structures has received attention and reports of superconformal electrodeposition of Ni and related iron-group magnetic alloys are available [19][20][21][22]. Addition of a single additive, such as the mercaptobenzimidazole derivatives, MBIS and MBI [20,21], or polymers such as polyethyleneimmine [19], to an additive-free Ni plating bath has been shown to be effective in generating void-free trench filling by a mechanism that is distinct from that used for the Group IB metals [15][16][17][18]. The feature filling involves an inhibition-breakdown process that initially gives rise to a v-notch shaped growth front within the trench followed by geometric leveling.…”

Electroplating of Fe-Rich NiFe Alloys in Sub-50 nm Lines

“…17 A combination of PEI and thiourea (TU) was found to improve the filling performance. Lee et al 18,19 studied the effect of a different additive, 2-mercapto-5-benzimidazolesulfonic acid (MBIS), on the plating of Ni, Ni 70 Fe 30 , Co and CoFe. They observed that the presence of MBIS inhibits the plating of these metals at less negative potential using cyclic voltammetry.…”