Open-contact failure detection of via holes by using voltage contrast

We used two techniques to determine the sensitivity of a scanning-electron-microscope-based wafer-inspection system in detecting open-contact failures. (1) The correlation between the contact resistance and the brightness of the voltage-contrast image as captured by the system was obtained experimentally. (2) A voltage-contrast simulation was developed and applied to derive a correlation between resistance and brightness from these results. A close agreement between the experimental results and the calculated values was obtained. We succeeded in clarifying the determinants of the sensitivity of open-contact-failure detection. The brightness, over part of its range, appears to be proportional to log(R*I p ) where R is the resistance and I p is the irradiating electron-beam current. This relationship indicates that the sensitivity of open-contact failure detection is determined by I p . Control of I p can be used to improve the voltage contrast, and this, in turn, can improve the sensitivity of detection.