The investigation of an alternate approach to nondestructive, nanoscale mechanical imaging for IC interconnect structures is reported. This approach utilizes a heterodyne interferometer based on a scanning probe microscope, also referred to as heterodyne force microscopy (HFM). This interferometer is sensitive to the relative phase difference of the two ultrasonic excitations due to spatial variations in the sample viscoelastic response and enables near-field, phase-sensitive imaging. Proof-of-feasibility demonstrations of this technique are presented for ultrasonic phase-imaging of Al/low-k interconnect structures. Spatial resolution <10 nm is demonstrated.