Design and fabrication of a monolithic high-density probe card for high-frequency on-wafer testing

A novel probe card structure for high-density, high-frequency applications is described. Conventional probe tips are replaced by compliant, multilayer cantilever beams fabricated monolithically on a silicon wafer, which, if desired, can include active circuitry elements. All fabrication steps are based on standard IC processing and micromachining technologies. The mechanical and electrical characterizations of the probe card structure, based upon numerical simulations, are summarized. The principal findings are: (1) sufficient elastic deflection (>50 mu m) of a multilayer probe tip can be obtained by controlling the residual stresses in each film; (2) resisting forces produced by the elastic deformation of the beam can generate stable and relatively low contact resistances (<0.3 Omega ) for Au-to-Au contacts; and (3) the bandwidth of the system is estimated at approximately 20 GHz.<>