Design, simulation, fabrication and testing of microprobes for a new MEMS wafer probe card

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. 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 cm{dollar}sp2{dollar} chip with a microprobe repeat distance of {dollar}sim{dollar}50 {dollar}mu{dollar}m. Each microcantilever has an internal heater and a separate electrode carrying the signal under test and contains four separate layers plus a fifth material for the contact tip region.; Different versions of micro-actuators have been designed and made. Ohmic contacts are made with a lowest contact resistance of 250 m{dollar}Omega{dollar}. The heating efficiency various over the range 5.23 to 9.6 {dollar}mu{dollar}m/mW. Maximum reversible deflection is in the range of 300 {dollar}mu{dollar}m. Video recordings made inside the SEM clearly show ohmic contact being made to a stationery tungsten electrode. A full dynamic deflection (134 {dollar}mu{dollar}m) for a 40 x 300 {dollar}mu{dollar}m cantilever occurs in response to input frequency up to near 120 Hz, motion being dampen at higher frequency, and until reaches the first cantilever resonant frequency ({dollar}sim{dollar}6485Hz). Heat loss for devices operating in air was found to be substantially higher than for vacuum operation with heat loss ratio is about 2/1 for a heater inside structure; and 4.25/1 for a structure with the heater as an outer layer of the cantilever.