Effective Method for Decreasing Detection Limit of Dopant Concentration in Semiconductor Using Dual SDD Analysis System
An energy dispersive spectrometer (EDS) analysis system using a Si drift detector (SDD) can perform a highly sensitive elemental analysis due to its flexibilities of detector shape and size and high speed processing. In addition, the use of multiple SDD sensors can dramatically enlarge the effective area of the detector, which should shorten the measurement period while increasing detection sensitivity. Up to now, transmission electron microscopy (TEM)-EDS has not been greatly used in the analysis of elements in semiconductor doping. This is because the limit of detection (LOD) by Si(Li)-EDS is of the order of 1500-2000 ppm, which is a level of performance insufficient for dopant analysis in semiconductor industry. There has consequently been a strong desire to determine just how small an amount of elements can be detected (detection limit) using an analysis system with two SDDs. Theoretical estimation of LOD is determined with competition between the net counts for dopant element and the fluctuation of background tail of Si peak at the dopant peak energy [1]. When we measure the net counts of dopant element is three times larger than the fluctuation (sigma) of the background, it confirms the presence of the dopant with 99.7% certainty. Thus, we define a dopant concentration (Cdopant) at LOD as
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
Refinement of crystal structure parameters using convergent‐beam electron diffraction: the low‐temperature phase of SrTiO3
The method to refine crystal structure parameters (atom positions and Debye–Waller factors) using convergent-beam electron diffraction (CBED), which is applicable to crystal structure analysis of a small specimen area down to a few nm in diameter, is studied. The line profiles of higher-order Laue-zone reflections are recorded using imaging plates. Theoretical intensities are calculated based on the dynamical theory of electron diffraction with the aid of the generalized Bethe approximation to shorten calculation time. The structural parameters are determined by fitting the experimental profiles with the theoretical ones using a nonlinear least-squares method. The present method has been applied to the low-temperature phase of SrTiO3. The structural parameter or the rotation angle of the oxygen octahedron has been determined to be \varphi = 1.12 (4)°, which shows good agreement with that obtained from electron spin resonance experiments.