Microscopic four-point probe based on SU-8 cantilevers

A microscopic four-point probe (mu 4PP) for resistivity measurements on thin films was designed and fabricated using the negative photoresist SU-8 as base material. The device consists of four microscopic cantilevers, each of them supporting a probe tip at the extremity. The high flexibility of SU-8 ensures a stable electrical point contact between samples and probe tip with all four electrodes even on rough surfaces. With the presented surface micromachining process, mu 4PPs with a probe-to-probe spacing of 10-20 mu m were fabricated. Resistivity measurements on thin Au, Al, and Pt films were performed successfully. The measured sheet resistances differ by less than 5% from those obtained by a commercial macroscopic resistivity meter. Due to the low contact forces (F-cont < 10(-4) N), the mu 4PP is suitable to be applied also to fragile materials such as conducting polymers. Here the authors demonstrate the possibility of performing resistivity measurements on 100-nm-thick pentacene (C22H14) films with a sheet resistance R-s>10(6) Omega/square. (c) 2005 American Institute of Physics.