Contactless Function Test of Integrated Circuits on the Wafer

Conventional needle probecard techniques suffer from several problems: needles scratch the pads causing bonding problems, the maximum test speed is limited by the poor high frequency performance of the needle contacts. This contribution presents a new contactless method to inject test stimuli and to monitor the output. On chip photo diodes and simple receiver circuits transform light pulses to proper input signals, while a capacitively coupled probe with a very sensitive charge amplifier detects the output signal. The apparational overhead to conventional test system is small as well as the chip space required for photo diode and receiver circuit.