Precision Probing Techniques for Planar S-Parameter Measurements

Abstract

On-wafer measurement system is useful for measurement and characterization of integrated planar circuits and components at radio-frequency (RF) to sub-mm frequencies. However, traceable S-parameter measurements of planar circuits at sub-mm frequencies has been a challenge due to complexity of measurement technique. First and foremost intricacy is accurate probe posi tioning. This report presents detailed development of precision probe positioning techniques for planarization, alignment and contacting of probe on top of on-wafer device. Using 3D EM models of probe in CAD software, each probing technique was first validated in simulation environment. Results of subsequently performed experiments show that image processing tech niques combined with VNA-measurement based techniques can accurately align the probe with accuracy less than 2µm which can be further improved by using higher resolution microscope. Similarly, automated probe planarization and contacting techniques developed ensure proper probe-device electrical contact. This increases the life time of device as number of probe con tacts possible increase by at least 5 times the usual 20 probe contacts with manual probing. These probing techniques were incorporated in the MATLAB based software which will be used to control measurement system hardware to perform calibration and then measurements of planar devices.