Electromigration in Cu thin films with Sn and Al cross strips

Abstract

Initial void formation in bamboo Al-Cu(1%) two-level structure AIP Conf. Electromigration in Cu thin films is studied in a cross-strip configuration. Cu lines with isolated areas of Cu͑Al͒ or Cu͑Sn͒ are tested between 250 and 390°C with the following results. The hillock and void marker motion indicates that Sn moves in the direction of electron flow. The marker polarity indicates that it decreases the grain boundary electromigration of Cu, in agreement with previous studies. This study also finds evidence of active surface migration in Cu. During tests in forming gas, hillocks and voids form adjacent to a native Al 2 O 3 layer at all temperatures, indicating the likelihood that Cu migrates faster through the Cu free surface than the interface between the surface layer of Al 2 O 3 and Cu͑Al͒. Active surface migration in Cu thin films is also evidenced by the growth of hillocks with highly developed facets, most of which are attached to the underlying film by narrow necks.

Effect of electrodeposition parameters on the hydrogen permeation during Cu–Sn alloy electrodeposition

“…On the other hand, Cu-Sn alloy plating is widely used in coal machinery industry, microelectronic applications and anode materials in specific electrochemical reactions due to its excellent properties, such as low cost, good decorative, superior corrosion resistance, appropriate hardness and high electro-migration resistance [13][14][15][16][17][18][19]. It was often performed in the cyanic elec- trolyte.…”

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

“…[376][377][378][379][380][381][382][383] Numerous different types of dopants elements beyond Si have been reported for Cu with Sn, Al, Mg, and Mn being perhaps the most popular. In this method, the improvements in electromigration are believed to be due to the dopant atom segregating from the bulk Cu and diffusing to the Cu/DB interface and helping passivate the Cu surface and/or improving the adhesion strength between Cu and the DB.…”

“…Many of the reported methods involve either doping the Cu lines with a few percent of select alloying elements, [376][377][378][379][380][381][382] or selectively forming an additional surface passivation layer material between the DB and Cu. [383][384][385][386][387][388][389][390][391][392][393] In most cases, these methods involve additional processing steps separate from the DB deposition process.…”

Stress relaxation induced faceted Cu and W particles on the surfaces of Cu–Zr and W thin films

“…In this process, the minimization of surface and strain energy is the thermodynamic driving force. Similar faceted Cu particles were also observed in the study of electromigration of Cu thin films [9]. Surface energy can be lowered by cutting its vertices and exposing (1 0 0) faces, obtaining a truncated octahedron.…”

“…Copper (Cu) rich hillocks [2] and pure Cu hillocks [9] were observed during the annealing of Cu-Mo composite thin films as well as in the electromigration test on Cu-Sn systems. Various mechanisms, such as interfacial diffusion [10], surface diffusion [11] and grain boundary diffusion [5], have been proposed for hillock formation.…”