Wafer probes and probe stations are marvels of mechanical engineering. They are capable of delicately maneuvering measurement probe contacts onto micron-sized circuit features with enough contact force to make meaningful measurements without causing damage to the circuits. As semiconductor wafers have grown in size, designers of wafer probe stations have responded with probe stations capable of handling larger wafers with precision. At higher frequencies, it is the precision needed for millimeter-wave S-parameter measurements. Modern probes and probe stations provide the placement precision for on-wafer measurements to 70 GHz and beyond.
Semiconductor wafer probing systems are available as manual, semi-automated, and fully automated systems. Working with test probes mounted in micro positioners, they can achieve the precision needed to place a probe tip onto a miniature test point, such as an IC’s probe pads. With that contact made, microwave test equipment such as a vector network analyzer (VNA) can be used to characterize circuit or device electrical behavior for modeling and packaging purposes.