Near-field measurements of VLSI devices

This short paper describes a technique for the measurement of the electric near field at the package surface of microprocessors and other VLSI devices. The technique uses precision stepper motors for highly accurate placement of an electric field probe at the surface of the device to be measured. Structural resolution across the device is on the order of 400-600 mu m. Typical scans accumulate 10 000 data points across a variable scan area, which can be defined by device package dimensions or by the die dimensions. Characterizing a device involves a repeated series of surface scans at harmonics of the fundamental clock frequency. This paper describes the electric near field at the surface of a multichip module (MCM) composed of a processor, a flash memory, and application specific integrated circuit (ASIC). The MCM was measured while in operation in the actual circuit application.