Open-Contact-Failure Detection of via Holes by using Voltage Contrast

摘要

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.