Current capacity evaluation of a cantilever probe

Abstract

The tungsten-rhenium (WRe) 3mil cantilever probe is widely used in wafer probe at ON Semiconductors. The maximum current that can be supplied to a DUT is restricted by the current capacity of the probe needles. A typical 3 mil tip probe can carry 2 - 3 Amps at a short burst current (I short) for a <;10 ms pulse time. Probing at a higher current level with minimal number of probes can cause current over crowding at probe tip which produces excessive heat due to electric charge and contact resistance. This heat can melt surface material and contaminant which can attach to the probe tip causing it to be deformed thus increasing resistance and temperature at the contact point. Accordingly more heat is generated by this causing the contaminant at probe tip to be further oxidized producing an insulating layer between DUT and probe. This results in spark occurrence during high current testing which may cause damage to the device. This paper describes the experiments carried out to guarantee the appropriate pulsed current level that can be carried through a single 3 mil tip probe without causing the probe tip to melt, get oxidized and generate sparks which could lead to devices damage due to EOS. Two MOSFET devices with current ratings of 2.0 Amps and 2.6 Amps respectively were used for this evaluation to determine the allowable operating pulsed current a probe can withstand. A Total of 85 K dies were probed, assembled and final tested. The test fallouts that were analyzed did not show any indication of an EOS signature on die cause by probe needles.