1/f Noise measurements for faster electromigration characterization

© 2016 IEEE. The application of 1/f noise measurements to speed up electromigration (EM) testing and provide a better understanding of the underlying mechanisms of electromigration in advanced microelectronics interconnects is investigated. It is shown that 1/f noise measurements can be used for early EM damage detection during EM stress, before any changes in the resistance of the sample are observable. Also, the temperature dependence of the low frequency noise is used to calculate activation energies, which are then demonstrated to be similar to values found for electromigration using standard EM tests. Furthermore, the 1/f noise technique is used to assess and compare the EM properties of various advanced integration schemes and different materials. The 1/f noise measurements provide new evidence for the importance of grain boundary diffusion as a dominant EM failure mechanism in highly scaled interconnects.status: publishe

Demonstration of low-frequency noise measurements for studying electromigration mechanisms in advanced nano-scaled interconnects

Electromigration (EM) strongly decreases the reliability of micro-electronics interconnects and becomes more problematic as scaling continues. Remedial measures are required, but therefore EM mechanisms first have to be understood. The standard, accelerated EM test methods are time-consuming, destructive and provide only limited physical understanding. We demonstrate that low-frequency (LF) noise measurements can be used to calculate EM activation energies, making it a fast and non-destructive alternative test method that leads to new insights into the underlying EM mechanisms. More specifically, we show 3 different approaches to calculate activation energies based on LF noise measurements and prove their equivalence.status: publishe

1/f noise measurements for faster evaluation of electromigration in advanced microelectronics interconnections

The use of 1/f noise measurements is explored for the purpose of finding faster techniques for electromigration (EM) characterization in advanced microelectronic interconnects, which also enable a better understanding of its underlying physical mechanisms. Three different applications of 1/f noise for EM characterization are explored. First, whether 1/f noise measurements during EM stress can serve as an early indicator of EM damage. Second, whether the current dependence of the noise power spectral density (PSD) can be used for a qualitative comparison of the defect concentration of different interconnects and consequently also their EM lifetime t50. Third, whether the activation energies obtained from the temperature dependence of the 1/f noise PSD correspond to the activation energies found by means of classic EM tests. In this paper, the 1/f noise technique has been used to assess and compare the EM properties of various advanced integration schemes and different materials, as they are being explored by the industry to enable advanced interconnect scaling. More concrete, different types of copper interconnects and one type of tungsten interconnect are compared. The 1/f noise measurements confirm the excellent electromigration properties of tungsten and demonstrate a dependence of the EM failure mechanism on copper grain size and distribution, where grain boundary diffusion is found to be a dominant failure mechanism.status: publishe

Study of the enhanced electromigration performance of Cu(Mn) by low-frequency noise measurements and atom probe tomography

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Study of the enhanced electromigration performance of Cu(Mn) by low-frequency noise measurements and atom probe tomography

The enhanced electromigration (EM) performance of 20 nm-wide Cu interconnects with a Mn-doped Cu seed and a Mn-based barrier is studied by means of low-frequency (LF) noise measurements and atom probe tomography (APT). While the EM activation energy of reference interconnects without Mn is 0.8 eV, standard EM tests revealed an activation energy of 1.0 eV for Cu(Mn) interconnects. The LF noise measurements confirm the activation energy of 1.0–1.1 eV in the Cu(Mn) interconnects, but also the activation energy of 0.8 eV is still visible, though less pronounced. Furthermore, the extent to which the mechanism at 0.8 eV is suppressed is strongly subjected to sample variations. These observations are confirmed by APT; Mn is found at the top surface and small clusters of Mn are present in the Cu bulk up to 5 nm away from the sidewalls. Mn segregation at the grain boundaries was not observed such that the hypothesis of Mn blocking grain boundary diffusion cannot be confirmed.status: publishe

A novel electromigration characterization method based on low-frequency noise measurements

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New breakdown mechanism investigation: barrier metal penetration induced soft breakdown in low-k dielectrics

© 2016 IEEE. A Soft Breakdown (SBD) phenomenon happening in porous low-k dielectrics during time dependent dielectric breakdown measurements was investigated. The early formation of local conductive paths was identified by monitoring leakage currents and capacitance data in the SBD phase. The nature of this conductive path was demonstrated to be related to intrinsic dielectric degradation. By comparing samples with different process conditions, we found that barrier metal penetration is an important root cause of SBD initiation. Our study of the voltage and temperature acceleration of the SBD phenomenon shows that these acceleration factors, m=22 and Ea=0.2eV, are at a reasonable level. However, further investigations on large size devices illustrate that the difference in barrier metal penetration depth between different samples could lead to a large decrease of Weibull slopes and degrade the overall reliability performance. Therefore, innovations of metal barrier deposition on porous low-k dielectrics to avoid barrier metal penetration are required for advanced technology nodes.status: publishe