Parameter Modeling for Wafer Probe Test

This paper presents the simulation of parameters for wafer probe test by finite-element modeling with consideration of probe over-travel (OT) distance, scrub, contact friction coefficient, probe tip shapes, and diameter. The goal is to minimize the stresses in the device under the bond pad and eliminate wafer failure in probe test. In the probe test modeling, a nonlinear finite-element contact model is developed for the probe tip and wafer bond pad. Modeling results have shown that the probe test OT, probe tip shape and tip diameters, contact friction between the probe tip and bond pad, as well as the probe scrub of the probe tip on bond pad are important parameters that impact the failure of interlayer dielectric (ILD) layer under bond pad. Comparison between probe test damage and wire bonding failure shows the degree of damage to both probe test and wire bonding on the same bond pad structures. In addition that, a design of experiment (DOE) probe test with different ILD and metal thickness is carried. The correlation between the modeling and the DOE test is studied. The results show that the modeling solution agrees with the DOE probe test data. Modeling results have further revealed that probe test can induce the local tensile (or bending) first principal stress in ILD layer, which may be a root cause of the ILD failure in probe test.