E-beam mechanics and net connectivity for interlayer short detection: DI: Defect inspection and reduction

The concept of layout-centric defect inspection targeting specific configurations of design is not new. The majority of design-based Micro Care Areas (MCA) relies on historical findings — translating failing topologies from Failure Analysis (FA), Design-for-Manufacturing (DFM), and other sources into targeted zones tailored for inspection. However, there exists an inherent flaw to this model tied to physical limitations of top-down optical inspection. There exists a subset of physical defects that are invisible to optical inspection tools, in particular interlayer defects that interact with prior level masks. For such applications, defect engineering will turn to Electron-Beam (E-beam) Voltage Contrast Inspection (VCI) — which compares the response of a wafer feature subjected to electron charging, measured in grey level differences, of a candidate defect to a reference. In our previous paper “Net Tracing and Classification Analysis on E-Beam Die-to-Database” [3], we illustrated the merits of factoring feature connectivity as a means of differentiating between real voltage-contrast defects, specifically that of dark voltage-contrast (DVC), and nuisance. Our novel methodology takes into consideration the inspectability of a targeted feature before generating components for design-based inspection. The process has the obvious consequence of decreasing the total area of inspection and subsequent benefit of reducing the inspection time. The concept is intuitive — a wafer feature, typically a Via, with a dark optical response when a bright response is expected is indicative of either blockage in the connected electrical net or otherwise disconnect between features. That said, DVC is but a subset of detectable defects with E-beam. This paper reports a novel approach in capturing defects of the other subset of the population, bright voltage-contrast (BVC) and its implications, through exercising the same principle of inspectability.