Abstract Threshold Voltage (Vt) of MOSFET controls transistor’s on and off state. Vt is usually depends on gate oxide thickness and operating temperature. Systematic failure analysis for a Vt shift issue, should also consider the channel doping which affects the inversion layer formation. In this article, the failure case of a shift in the Vt of a Power MOSFET V is studied. Secondary Ion Mass Spectrometry (SIMS) is found to be the most direct way for detecting any abnormality in the channel doping profiles. A comprehensive simulation is performed showing that the Phosphorus level diffusion from substrate was so high that it affects the doping concentration of channel.

Abstract In this work, delineation of crystal defects in Si by preferential chemical etching (Wright etch) is discussed. Investigation of defects in Si wafers by preferential chemical etching enables the study of various types of crystal defects for large area defect distribution (up to full wafer) and root cause analysis. In the case of dislocation defects, the shapes of etch pits are different for different etching duration. We show the mechanism of the pit shape evolution under preferential etching and suggested the appropriate etching duration for defect type identification with inspection by optical microscopes. The dislocation delineation method has been applied to a case of functional failure of devices caused by abnormal process in Laser Scanning Annealing (LSA). It was shown that the distribution of dislocation defects depends largely on the direction of LSA scan direction. We discuss the relationship between dislocation defect distribution and the density and uniformity of the active-Si patterns as well as possible solutions for elimination of dislocation defects in LSA process.

Abstract In this paper, we propose a new methodology and test system to enable the early detection and precise localization of Time-Dependent-Dielectric-Breakdown (TDDB) occurrence in Back-End-of-Line (BEOL) interconnection. The methodology is implemented as a novel Integrated Reliability Test System (IRTS). In particular, through our methodology and test system, we can easily synchronize electrical measurements and emission microscopy images to gather more accurate information and thereby gain insight into the nature of the defects and their relationship to chip manufacturing steps and materials, so that we can ultimately better engineer these steps for higher reliable systems. The details of our IRTS will be presented along with a case study and preliminary analysis results.

Abstract Different epitaxial structures have been studied by high-resolution x-ray diffraction and x-ray topography, Transmission Electron Microscopy and Atomic Force Microscopy to establish correlations between epitaxial growth conditions and crystal perfection. It was confirmed that epitaxial growth under initial elastic stress inevitably leads to the creation of extended crystal defects like dislocation loops and edge dislocations in the volume of epitaxial structures, which strongly affect crystal perfection and physical properties of future devices. It was found that the type of created defects, their density and spatial distribution strongly depended on growth conditions: the value and sign of the initial elastic strain, the elastic constants of solid solutions, the temperature of deposition and growth rate, and the thickness of the epitaxial layers. All of the investigated structures were classified by their crystal perfection, using the volume density of extended defects as a parameter. It was found that the accommodation and relaxation of initial elastic stress and creation of crystal defect were up to four stages “chain” processes, necessary to stabilize the crystal structure at a level corresponding to the deterioration power of particular growth conditions.

Abstract Inclusion of cerium (Ce) oxide particles as an abrasive into chemical mechanical planarization (CMP) slurries has become popular for wafer fabs below the 45nm technology node due to better polishing quality and improved CMP selectivity. Transmission electron microscopy (TEM) has difficulties finding and identifying Ce-oxide residuals due to the limited region of analysis unless dedicated efforts to search for them are employed. This article presents a case study that proved the concept in which physical evidence of Ce-rich particles was directly identified by analytical TEM during a CMP tool qualification in the early stage of 20nm node technology development. This justifies the need to setup in-fab monitoring for trace amounts of CMP residuals in Si-based wafer foundries. The fact that Cr resided right above the Ce-O particle cluster, further proved that the Ce-O particles were from the wafer and not introduced during the sample preparation.

Abstract The distribution of Si nanoparticles, both dimensional and spatial, is a key factor affecting the performance of non-volatile flash memory devices. A new FIB method has been developed to prepare ultra-thin plan view specimens, containing only the Si nanoparticle matrix thin film layer, from fully processed nanocrystalline flash memory devices. The morphology and distribution of Si nanoparticles were then studied by EFTEM 3D tomographic reconstruction.

Abstract Transmission electron microscope based elemental analysis techniques utilize X-ray photons in EDS and inelastically scattered electrons or the energy-loss electrons in electron energy-loss spectroscopy and energy-filtered transmission electron microscopy (EFTEM). This paper discusses the applications of EFTEM to visualize polysilicon defects, gate dielectric and silicon nanocrystals using inelastically scattered low energy-loss electrons. It focuses on features that are primarily composed of silicon and silicon-oxide. Various benefits of using plasmon energy-loss electrons to image silicon nanocrystals layer in thin film storage device are also outlined. Even though this work has focused on low-loss imaging of features and defects in the front-end of the process based on silicon/silicon-oxide integrated circuits, these techniques can also be applied to technologies based on other materials by selecting appropriate plasmon peaks corresponding to those materials.