Abstract

In this paper, we present our recent applications of scanning capacitance microscopy (SCM) on specific devices with sampling window as small as 100nm. The dopant related root causes were successfully identified on those devices fabricated with 90nm CMOS technology. The key step in our approach is the development of a sample preparation technique that allows us to precisely x-section through a transistor without being affected by focused ion beam (FIB) artifacts. FIB was used to mark the area of interest with high precision, but it did not expose the devices of interest. Optical microscope and atomic force microscope (AFM) were used to inspect the mechanically polished surface, thus avoiding beam effects from FIB or SEM. In the first application, a doping anomaly was identified in a PFET poly gate, in a single bit failed SRAM cell. In the second application, an asymmetry of a PWell implant profile in a window of 150nm was identified as the cause of leakage in a capacitor array. Our approach may be applied to other scanning probe microscopy (SPM) techniques in the same category, i.e., scanning spreading resistance microscopy (SSRM) or scanning microwave microscopy (SMM).

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