Current imaging, EBIC/EBAC, and electrical probing combined for fast and reliable in situ electrical fault isolation
Abstract Using a compact nanoprobing setup comprising eight probe tips attached to piezo-driven micromanipulators, various techniques for fault isolation are performed on 28 nm samples inside an SEM. The employed techniques include nanoprobing as well as EBAC. The recently implemented Current Imaging technique is used to quickly image large arrays of contacts providing a means of locating faults. In this case, Current Imaging provides insight into the sample's behaviour yielding qualitatively comparable results to the more cumbersome cAFM technique. While the results of the TEM investigations including EDX mappings were inconclusive, the Current Imaging technique clearly shows that the root cause is located below the SiGe layer. By combining these techniques inside a FIB/SEM microscope, it is possible to locate and characterize a failure as well as prepare a TEM lamella for further investigation without the necessity to switch to a different tool.
Method of Precise Positioning for Defect Failure Analysis Based on Nano-Probing and EBAC
Failure analysis (FA) becomes increasingly crucial for semiconductor industries with the scale-down and larger integration of devices. In order to overcome the limitation of traditional optical resolution for FA techniques, this article proposed an effective method of precise positioning of circuit defect based on localized probing technique, nano-probing and electron beam absorbed current (EBAC). Open circuit, short circuit and gate/capacitor oxide defects were the most common failures in IC manufactures, therefore representative examples based on these failures were employed to illustrate the analysis procedure and effectiveness of the proposed method. Scanning electron microscope (SEM), focused ion beam (FIB) and transmission electron microscope (TEM) results were presented to verify the accuracy of the positioning. It was demonstrated that the proposed precise positioning method was able to accurately locate the defect position, and was useful for determining the failure mechanism as well. The method showed great potential for improving the success rate of FA for semiconductor devices.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.