Backside infrared probing for static voltage drop and dynamic timing measurements

Due to the increased number of metal layers and flip-chip packaging, most high-performance microprocessors use optical solutions to probe internal nodes from the backside of the die. Existing probing systems use a focused infrared (1.064/spl mu/m) laser to probe internal diffusions from the backside of a chip thinned down to 100/spl mu/m. However, this optical probing setup does not provide accurate information about DC voltage levels. Also, because of the stroboscopic sampling used in laser probing, jitter measurements are difficult. This approach overcomes these limitations using alternative optical non-invasive techniques based on the infrared radiation emitted by hot electrons in saturated nMOS transistors under both static bias and switching conditions.