An active substrate silicon probe card has been implemented by forming a po
lyimide membrane on a silicon substrate. The probe card combines tungsten p
robe tips and aluminum interconnects in the polyimide membrane with active
test circuitry integrated in the substrate. A monolithic prototype of the p
robe card designed to enhance the capabilities of conventional digital test
systems has been fabricated in a 2-mu m BiCMOS technology.
The benefits of the proposed probe-card technology could be further exploit
ed by integrating the timing measurement unit of a digital tester into the
probe-card substrate, An integrated tester architecture based on time digit
ization is described. A prototype of a tester combining a time digitizer an
d two test channels has been integrated in a 0.6-mu m BiCMOS technology. Th
e time digitizer in the experimental circuit employs a two-stage ring oscil
lator that is phase-locked to an external reference and makes use of phase
interpolation to achieve a timing resolution of 90 ps.