Probe contact resistance variations during elevated temperature wafer test

Localized electrical contact phenomena during wafer test can significantly affect contact resistance magnitude and stability of tungsten (W), tungsten-rhenium (WRe), beryllium-copper (BeCu), Pd-alloy (Paliney-7), and metallic-alloy (NewTek-Probe) probes. Typically, increased and unstable contact resistance (C_RES) during aluminum wafer test at 85°C with tungsten (W) and tungsten-rhenium (WRe) probe needles is attributed to adherent oxides from the aluminum bond pads. New experimental data indicates that oxide formation due to localized Joule heating at the probe tip contact “a-Spots” significantly contributes to the C_RES variations. Use of non-oxidizing probe materials could provide low and stable C_RES with reduced cleaning frequency at elevated temperatures. Preliminary production level beta testing on actual devices using NewTek probes demonstrated significant reductions in continuity failures, cleaning frequency, and operator intervention