Investigation of Detection Limits of Resistive Contact Plugs in Electron Beam Inspection Using Modeling and Simulation

Electron beam inspection has been commonly used in the semiconductor fabrication process to inspect wafers for defective metal or polysilicon plugs, plugs that fail to make an electrical contact to the underlying circuitry. Recently, there has been interest in using electron beams to inspect plugs that are not necessarily electrically floating but have a high resistive path to ground. This paper addresses the reliability of such an inspection by examining the minimum resistance value that is detectable for a given column condition and gives guidelines for optimal inspection conditions for finding such a defective plug. The investigation is done using a transient simulation in a general purpose 3-D electron beam simulator that uses Monte Carlo simulations to trace the path of an ensemble of charged particles in an electrostatic field and couples with a general purpose Poisson solver that is also used to update the electrostatic fields from evolving charge profiles.