Resolution scaling in noncontact scanning impedance imaging

Noncontact scanning impedance imaging has been presented as a method to provide high resolution, high contrast images for a variety of material systems. This technique combines electrical impedance measurements with very high resolution scanning. This article reports on efforts to scale this technique down to the very important single micron range and reveals measurements for both thick and thin samples with a measured minimum resolution below $30 μm$⁠. A design for a shielded impedance probe applicable to this process is outlined and probes of several different sizes were made and tested. Fabrication of these impedance probes is explained and a testing methodology to characterize the probes’ imaging capability is outlined. Measured results are reported and compared to a predictive model based on image blurring. Two-dimensional impedance images of objects have also been made indicating good image contrast and high resolution. Based on measured data and the model, scaling down to submicron resolution dimensions should be possible given small diameter probes and thin test samples.