Vector voltage measurement of MMICs using Electrostatic Force Microscopy

Abstract

As development in MMIC technology increases, the requirement for high frequency internal node measurement becomes increasingly important. MMIC based systems are becoming more complex with larger densities and smaller devices which demand probing instruments with high spatial and temporal resolution. Proper fault detection requires the ability to perform arbitrary internal node testing. Current probing techniques include: matched impedance[1], electro-optic[2], electron beam[3] and photoconductive sampling[4]. High frequency microwave measurements can be made using matched impedance probes. These allow for high frequency characterization of input and output characteristics of microwave circuits. Unfortunately they provide very little information concerning internal point of failure. The matched impedance probe is much too invasive to use at arbitrary nodes. Internal node probing techniques like contact probing, electro-optic, electron beam and photoconductive sampling are capable of internal node measurement. Scanning force probing techniques are becoming more popular since they rely on the non-contact interaction between a small probe and sample. They employ small micromachined probes with sharp tips (30 nm radius of curvature) which provide ample spatial resolution to probe internal MMIC components. The non-contact nature of this technique also allows for measurement of passivated circuits without the need for predefined test points. These probes typically add less than 1 fF of loading capacitance.