No abstract

Customized 2D wires are designed for high throughput electromigration testing on model Al and Cu thin films. Two direct writing approaches for defining the 2D wires are compared with photolithography. Electromigration effects on Al and Cu thin films are studied on 2D wires obtained applying both methods. A self‐developed four‐point probe is used to apply current through the test wires while measuring the potential drop along the wires. Photolithography is selected as the main method to outline the wires in order to have reproducible results in a high throughput manner. The errors of electromigration assessment are empirically evaluated by analyzing the data scattering for a large number of measured 2D wires. Inductively coupled plasma optical emission spectrometry (ICP‐OES) is performed on the photoresist removal solution before and after the lift‐off process. No traces of metallic elements are detected in both cases confirming the proposed mechanism.

Wide range binary and ternary thin film combinatorial libraries mixing Al, Cu, and Ga were screened for identifying alloys with enhanced ability to withstand electromigration. Bidimensional test wires were obtained by lithographically patterning the substrates before simultaneous vacuum co-deposition from independent sources. Current–voltage measurement automation allowed for high throughput experimentation, revealing the maximum current density and voltage at the electrical failure threshold for each alloy. The grain boundary dynamic during electromigration is attributed to the resultant between the force corresponding to the electron flux density and the one corresponding to the atomic concentration gradient perpendicular to the current flow direction. The screening identifies Al-8 at. % Ga and Cu-5 at. % Ga for replacing pure Al or Cu connecting lines in high current/power electronics. Both alloys were deposited on polyethylene naphthalate (PEN) flexible substrates. The film adhesion to PEN is enhanced by alloying Al or Cu with Ga. Electrical testing demonstrated that Al-8 at. % Ga is more suitable for conducting lines in flexible electronics, showing an almost 50% increase in electromigration suppression when compared to pure Al. Moreover, Cu-5 at. % Ga showed superior properties as compared to pure Cu on both SiO 2 and PEN substrates, where more than 100% increase in maximum current density was identified.