A New In Situ Microscopy Approach to Study the Degradation and Failure Mechanisms of Time-Dependent Dielectric Breakdown: Set-Up and Opportunities (original) (raw)
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Journal of Visualized Experiments, 2015
The time-dependent dielectric breakdown (TDDB) in on-chip interconnect stacks is one of the most critical failure mechanisms for microelectronic devices. The aggressive scaling of feature sizes, both on devices and interconnects, leads to serious challenges to ensure the required product reliability. Standard reliability tests and post-mortem failure analysis provide only limited information about the physics of failure mechanisms and degradation kinetics. Therefore it is necessary to develop new experimental approaches and procedures to study the TDDB failure mechanisms and degradation kinetics in particular. In this paper, an in situ experimental methodology in the transmission electron microscope (TEM) is demonstrated to investigate the TDDB degradation and failure mechanisms in Cu/ULK interconnect stacks. High quality imaging and chemical analysis are used to study the kinetic process. The in situ electrical test is integrated into the TEM to provide an elevated electrical field to the dielectrics. Electron tomography is utilized to characterize the directed Cu diffusion in the insulating dielectrics. This experimental procedure opens a possibility to study the failure mechanism in interconnect stacks of microelectronic products, and it could also be extended to other structures in active devices.
In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms
Journal of Applied Physics, 2014
An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a "tip-to-tip" structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25 C to the "tip-to-tip" structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200 C and above. V C 2014 AIP Publishing LLC.
Applied Physics Letters, 2011
Time dependent dielectric breakdown ͑TDDB͒ lifetime model study has been performed on a metal-insulator-semiconductor capacitor structure with copper directly deposited on silicon dioxide without a barrier material. The structure generates a low electric field acceleration of time-to-failure, which makes it possible to measure TDDB over a wide range of electric fields from 3.5 to 10 MV/cm and experimentally validate TDDB lifetime model without any assumption and data extrapolation. The experimental results are in good agreement with the so called 1 / E model and do not support the E, ͱE, or power-law model.
The Analysis of Dielectric Breakdown in Cu/Low-k Interconnect System
2006 European Solid-State Device Research Conference, 2006
Novel test structures were designed for TEM analysis to examine the origin of dielectric breakdown in Cu/low-k interconnect systems, and it was found to be associated with interfacial delamination. Using an electrostatic discharge zapping technique enables the dielectric breakdown monitoring progressively from the interfacial delamination between a SiC capping layer and a SiOC inter-dielectric layer to the catastrophic thermal breakdown of Cu/low-k interconnect system. The intermetal dielectric leakage current increased as the delamination becomes wider in terms of the number of electrostatic zaps.
In situ X-ray Microscopy Studies of Electromigration in Copper Interconnects
Real-time X-ray microscopy is applied for degradation studies to understand electromigration-induced transport processes in on-chip copper interconnects. The material transport in inlaid Cu line/via structures is observed with about 40 nm lateral resolution. The image sequences show void formation, migration and nucleation processes. Correlation of the real-time X-ray images with post-mortem SEM micrographs is used to discuss degradation mechanisms in inlaid copper interconnects. Due to the high penetration power of X-rays through matter and its high spatial resolution, X-ray microscopy (XRM) overcomes several limitations of conventional microscopic techniques. It utilizes the natural absorption contrast between the structures of interest, i.e. for on-chip copper interconnects embedded in dielectrics. Due to their different X-ray absorption characteristics at 0.52 keV, even different silicon compounds like Si, SiO 2 , and Si 3 N 4 can be distinguished in X-ray images of thinned layers as demonstrated. For failure analysis of thicker layers, phase contrast microscopy in the multi-keV photon energy range is proposed.
Evaluations of intrinsic time dependent dielectric breakdown of dielectric copper diffusion barriers
Thin Solid Films, 2011
Time-dependent dielectric breakdown Dielectric barriers Breakdown Copper interconnects SiCN BN Study of the intrinsic time dependent dielectric breakdown (TDDB) of dielectric copper diffusion barriers was realized using a unique planar capacitor (Pcap) test structure. The test vehicle has several advantages over the metal dot method. The most important one is the elimination of field enhancement effect which could be more than 50% in the case of metal dots. In order to test the effectiveness of this test vehicle, two different dielectric barriers, one conventional SiCN film and the other a BN film still under development, were selected for TDDB evaluations. Significant differences were observed between the two films in TDDB lifetime, the shape parameter β of the Weibull failure time distributions, and the characteristics of the current versus time curves. The BN film had a degradation of more than four orders of magnitude in TDDB lifetime than SiCN. The Weibull shape parameter β of SiCN was 8.4, among the highest values that have been reported for any dielectric barrier films, versus 1.4 for the boron nitride film. Furthermore, the SiCN film showed a decrease in current versus time curves during the initial stage of the stressing, a trend which is typically related to charge trapping in defect-free films. This was not the case for the BN film where the leakage currents were much higher. The results demonstrate that the Pcap test structure is an effective vehicle to evaluate the intrinsic reliability of dielectric barrier films.
Microstructure effect on EM-induced copper interconnect degradation: Experiment and simulation
Microelectronic Engineering, 2005
Both in situ microscopy experiments at embedded inlaid copper interconnect structures and numerical simulations based on a physical model are necessary to develop on-chip interconnect systems with a high immunity to EM-induced failures. In future, the copper microstructure will become more critical for interconnect reliability since interfaces will be strengthened, and consequently, they will not be the fastest pathways for the EM-induced mass transport anymore. As a consequence, copper microstructure characterization becomes increasingly important, and microstructure data have to be implemented into the numerical simulation. The described physical model will help to provide a closer link between the microstructure and the EM lifetime of copper interconnects.
Time-Dependent Dielectric Breakdown of Interlevel Dielectrics for Copper Metallization
Japanese Journal of Applied Physics, 1996
Bias-temperature stressing of Cu/dielectric/Si capacitors demonstrated that time-dependent dielectric breakdown (TDDB) lifetime strongly depends on dielectric materials. Phosphosilicate glass (PSG) films had much higher immunity from TDDB than thermally grown SiO2. This higher immunity of PSG films is attributed to their greater suppression of Cu diffusion. They provide good protection against Cu contamination of devices. The lifetime (τ) of plasma-enhanced chemical-vapor-deposited TEOS (PECVD–TEOS) films was found to be related to the electric field (E) by using Peek's law (E∝τ-1/4). Using this law, the lifetime becomes rapidly longer than does the previous expectation when the electric field reduces. This suggests PECVD–TEOS films have the potential to be used as interlevel dielectrics for Cu metallization.
Journal of Applied Physics, 2012
The electrical degradation of ultra low-k SiCOH dielectric before breakdown is investigated. A new technique to obtain information before breakdown has been developed to define stress conditions and observe degradation patterns before total destruction occurs. Electrical measurements and physical inspection in specifically designed test structures have been made to focus on intrinsic properties. A typical leakage current characteristic, voiding and tantalum transport have been observed. These observations have been interpreted by quantitatively adapting physical effects. This investigation provides a model that describes the observed phenomena in a qualitatively manner. V C 2012 American Institute of Physics. [http://dx.