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Concentration at Detection Limit of Dopant for Semiconductor Samples Using Dual SDD Analysis System

Yokohama, 221-0022, Japan An energy dispersive spectrometer (EDS) analysis system using a Si drift detector (SDD) can enhance sensitivity of compositional analysis by using a large solid angle detector [1,2]. The use of multiple EDS detector system dramatically enlarge the effective area of the detector, resulting in the short measurement period. Up to now, transmission electron microscopy (TEM)-EDS has not been greatly used in the analysis of elements for semiconductor doping. This is because the detection limit by Si (Li) - EDS is of the order of 1500-2000 ppm, which is insufficient for semiconductor industry. There has consequently been a strong desire to see “limit of detection (LOD)”, that is, how small an amount of elements we can be detected, using a multiple SDD analysis system. In this study, we explore the concentration at LOD for As dopant in Si device using FETEM with a dual SDD analysis system. We used an As-doped Si wafer as a sample. The depth profile of As concentration in the Si wafer has been verified by Secondary Ion Mass Spectrometry (SIMS). We made a cross sectional lamella sample for TEM observation using an ion milling (Ion Slicer EM-09100IS, JEOL). The thickness of the TEM sample is estimated to be 140 nm judging from the count rate of X-ray and probe current. We measured several data sets of EDS spectrum imaging using a 200kV FETEM (JEM-2800 JEOL) equipped with two SDD detectors (sensor area = 100 mm 2 ). The concentration profiles were extracted and converted from the data set with a quantitative analysis system (NSS 3, Thermo Fisher Scientific). Figure 1 shows