Novel optical probing technique for flip chip packaged microprocessors

A novel infrared (IR) optical probing technique which provides fast and direct access to diffusion (p-n junction) nodes directly through the silicon substrate is described. The optical probing technology allows waveform measurements to be obtained directly from internal nodes of a CMOS integrated circuit (IC). These measurements can be made on C4 (Flip Chip) mounted ICs in stand-alone, MCM or any other package type for which the chip backside is accessible and the silicon substrate can be thinned. Timing waveforms taken from state of the art Intel microprocessors running at core frequencies >400 MHz using this IR probing technique have been obtained and are presented.