We are confronted with electrostatic discharge in day-to-day life more frequently than we would want – sometimes simply the harmless touch of a door handle is enough for us to feel an unpleasant sensation. Compared to electronic systems and technologies, however, human beings are relatively insensitive: even low voltage levels are sufficient to trigger anything from small-scale damage to serious disruption, especially in the case of high-speed technologies. This problem is further compounded by the ongoing miniaturization trend in microelectronics, which at the same time results in a reduction of the maximum permitted discharge voltage. Improved ESD protection is therefore crucial, especially in the environment of automated production. The aim is to create exposure models in order to test individual components for their ESD stability. However, conventional testing methods are already reaching their limits in terms of accuracy and reproducibility, so more precise methods of measurement are required.
Fraunhofer EMFT has joined forces with Cisco to tackle this challenge by means of an industrial project in which the standardized method Charged Device Model (CDM) is compared to an innovative exposure method. So-called Capacitively Coupled Transmission Line Pulsing (CC-TLP) was developed at Fraunhofer EMFT, a method that enables more precise and reliable measurement. The great advantage of this measurement method is that unlike the CDM method, it does not produce uncontrollable air discharge that can hinder reproducible measurements. As such, the CC-TLP model achieves a higher level of reproducibility and precision. Tests on various product circuits indicate a very good correlation with the CDM in terms of both the failure threshold and the error signature.
One particularly useful feature is the possibility of testing circuits directly on a wafer so as to be able to detect ESD protection weaknesses at an early stage. The CC-TLP model is thus a valuable supplement to standardized measuring methods and may even offer an alternative in future.