A new type of MEMS cantilever wafer probe card consists of an array of microcantilevers individually actuated by bimorph heating to make contact with the test chip was designed and fabricated. This probe card is called the CHIPP (Conformable, High-Pin count, Programmable ) card and can be designed to contact up to 800 I/O pads along the perimeter of a 1 cm2 chip with a microprobe repeat distance of ~50 µm. Each microcantilever had an internal heater and a separate electrode carrying the signal under test and contained four separate layers plus a fifth material for the contact tip region.
Different versions of micro-actuators have been designed and made in this Ph.D. research. Ohmic contacts were made with the lowest contact resistance of 250 mΩ. The deflection efficiency varied from 5.23 to 9.6 µm/mW for cantilever length from 300-500 µm. The maximum reversible deflection was in the range of 270 µm. Video recordings made inside the SEM clearly show that ohmic contact was made to a stationery tungsten electrode. A full dynamic deflection (180 µm) for a 50 x 500 µm cantilever occurred in response to input frequency up to nearly 50 Hz. The motion was damped at higher frequencies, with a strong resonance (for a 50 x 500 µm device) at 8160 Hz. Heat loss for devices operating in air was found to be substantially higher than for vacuum operation with a heat loss ratio of about 2/1 for a heater inside the structure; and 4.25/1 for a structure with the heater as an outer layer of the cantilever
