Microcantilever Probe Cards With Silicon and Nickel Composite Micromachining Technique for Wafer-Level Burn-In Testing

A new type of probe card is designed and fabricated for wafer-level integrated circuit (IC) testing. Using micromachining technology, roughly 18000 cantilever-tip probes can be integrated in one 4-in wafer, with a minimum pitch of 90 mum for adjacent probing tips. The probe card employs a silicon-and-metal composite structure, in which the bulk-micromachined silicon cantilever arrays provide uniform probing height and good planarity for the tips, as well as, the electroplated nickel probing tips feature high hardness and satisfactory electric contact with the pads to be tested. Electroplated nickel is used to simultaneously create the probing tips and the through-wafer interconnects (TWIs), which can transfer the testing signals from the dies-under-test (at the wafer bottom side) to the input/output (I/O) interface (on the front side). The probe card makes full use of the excellent mechanical properties of single-crystal silicon and satisfactory electrical properties of electroplated nickel, with the TWIs facilitating the following solder-bump flip-chip packaging. The fabricated cantilever-tip is able to withstand a contact force of 50 mN, corresponding to a tip displacement of 33 mum. The measured contact resistances on metal thin-film specimens (Al, Cu, and Au) are all below 1 Omega, whereas the maximum current leakage across two adjacent tips is 90 pA at 5 V voltage.