A fast wafer-level screening test for VLSI metallization

A method for screening out poor-quality metallizations from VLSI fabrication lines by wafer-level probing is proposed. Theoretical analysis suggests a linear dependence of the metal line conductance on the square of the current density, at thermal equilibrium. The limit to this linearity for ideally perfect metallizations occurs at the metal melting point, at which there is a sudden decrease in the conductance value to zero. In real interconnects, nonidealities such as localized defects or nonuniform surrounding dielectric at isolated points could lead to a deviation of the conductance from ideal expectations. Using this as a diagnostic, a universal methodology for assessing metal quality, independently of the physical parameters of the metal line, is described. Qualitative correlation with electromigration lifetime results is used to validate the method.<
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