Bandgap measurements of low-k porous organosilicate dielectrics using vacuum ultraviolet irradiation

Zheng, Huifeng; King, Sean W.; Ryan, Vivian; Nishi, Yoshio; Shohet, J. L.

doi:10.1063/1.4865407

Cited by 15 publications

(11 citation statements)

References 17 publications

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“…This bandgap range of low-k dielectrics is similar to the one of amorphous SiO 2 , which is between 8.0 and 8.8 eV. The reflection electron energy loss spectroscopy results from King et al, 10 the ellipsometric data from Marsik et al, 13 the vacuum ultraviolet (VUV) spectroscopy measurements from Zheng et al 14 and the X-ray photoelectron spectroscopy analysis from Nichols et al 15 support that the bandgap of most porous SiOCH type low-k dielectrics (k = 2.0-3.3) are in the range between 7.5 to 10 eV. In addition, the barrier height at both the low-k/metal and the low-k/Si interfaces can be measured with internal photoemission experiments.…”

Section: Bandgap and Conduction Mechanisms In Low-k Dielectricsmentioning

confidence: 99%

Electrical Reliability Challenges of Advanced Low-k Dielectrics

Baklanov

et al. 2014

ECS J. Solid State Sci. Technol.

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We review the latest studies that address the fundamental understanding of low-k dielectric electrical properties and reliability. We focus on the results discussing the nature of process induced defects, leakage currents and breakdown behavior, as they are important factors to reveal material modification and damage. Issues related to the use of porogen based PECVD techniques during dielectric deposition are discussed, where we focus on the selection of matrix and porogen precursors and on the improvements related to post-deposition treatments. During damascene integration, low-k dielectrics are subjected to several processes that induce material damage, where we review recent learning about plasma exposure, barrier deposition and chemical mechanical polishing. In order to have a successful implementation of advanced ultralow-k films in back-end-of-line interconnects, we argue that more research efforts are needed with respect to its material development, integration and reliability and make some proposals for future work. The development and integration of reliable low-k materials is a key challenge for next generation interconnect technologies. Driven by the requirement of performance increase, highly porous low-k dielectrics are incorporated in deeply scaled back-end-of-line (BEOL) interconnects. In general, there are three important concerns during the study of low-k dielectric electrical properties and reliability: a) the k-value of the dielectric after integration should maintain relatively unchanged, b) the leakage current of the dielectric between metal lines should be low, and c) the time dependent dielectric breakdown (TDDB) failure time of the integrated BEOL structure at operating conditions should meet its specifications. 1Porous SiOCH low-k dielectrics deposited by plasma enhanced chemical vapor deposition (PECVD) techniques are the dominant choice for k>2.2 film depositions and are also potential candidates for ultralow-k (k<2.2) dielectric applications.2 In the past years, significant efforts have been spent to understand their material properties and integration challenges. The bond structures of low-k dielectrics is complex due to the non-equilibrium nature of the PECVD technique.

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Section: Bandgap and Conduction Mechanisms In Low-k Dielectricsmentioning

confidence: 99%

Electrical Reliability Challenges of Advanced Low-k Dielectrics

Baklanov

et al. 2014

ECS J. Solid State Sci. Technol.

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“…The highest peak was observed in the VUV photoemission spectrum at an energy of 7.6 eV. Since 7.6 eV is lower than the band gap of the tested sample, 14 electrons in the valence band of SiCOH could not absorb enough energy from these photons to be emitted into the vacuum. Therefore, this implies that there must be a defect center within the band gap of SiCOH from which level the electrons could be emitted into vacuum condition after absorbing 7.6 eV from the irradiated photons.…”

Section: Effects Of Vacuum Ultraviolet Irradiation On Trapped Chargesmentioning

confidence: 92%

“…12,13 By measuring the VUV photoemission spectra, peaks in the measured photoemission currents at various photon energies can be detected. By comparing the photon energy at which the electrons are excited with the measured bandgap of the tested samples reported in the previous work, 14 the presence of electron traps and their energy distribution can be found.…”

Section: Effects Of Vacuum Ultraviolet Irradiation On Trapped Chargesmentioning

confidence: 98%

“…Therefore, this implies that there must be a defect center within the band gap of SiCOH from which level the electrons could be emitted into vacuum condition after absorbing 7.6 eV from the irradiated photons. Since the threshold energy for electrons in the test samples to be emitted from the valance band of dielectrics into vacuum is 8.9 eV, 14 it is plausible that the trap center is located 1.3 eV above the valence band of SiCOH. In addition, it can be concluded that VUV irradiation with photon energies between 7.6 and 8.9 eV can efficiently reduce the trapped charges within the dielectrics by photoemission.…”

Section: Effects Of Vacuum Ultraviolet Irradiation On Trapped Chargesmentioning

confidence: 99%

“…This is comparable to the VUV photon fluence emitted during a typical plasma process. 8,14,21 Photon energies were specifically selected to mimic those emitted by processing plasmas. 22 Specifically, photons of 8.4 eV energy (147.6 nm wavelength) were used to mimic the strong emission lines generated from a Xe plasma 23 which is a typical inert feed gas utilized in thin-film deposition.…”

Section: Effects Of Vacuum Ultraviolet Irradiation On Trapped Chargesmentioning

confidence: 99%

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Effects of vacuum ultraviolet irradiation on trapped charges and leakage currents of low-k organosilicate dielectrics

Zheng

Guo

Pei

et al. 2015

Applied Physics Letters

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Vacuum ultraviolet (VUV) photoemission spectroscopy is utilized to investigate the distribution of trapped charges within the bandgap of low dielectric constant (low-k) organosilicate (SiCOH) materials. It was found that trapped charges are continuously distributed within the bandgap of porous SiCOH and the center of the trapped states is 1.3 eV above the valence band of the tested sample. By comparing photoemission spectroscopic results before and after VUV exposure, VUV irradiation with photon energies between 7.6 and 8.9 eV was found to deplete trapped charge while UV exposure with photon energies less than 6.0 eV induces more trapped charges in tested samples. Current-Voltage (IV) characteristics results show that the reliability of dielectrics is improved after VUV irradiation with photon energies between 7.6 and 8.9 eV, while UV exposure results in an increased level of leakage current and a decreased breakdown voltage, both of which are harmful to the reliability of the dielectric. This work shows that VUV irradiation holds the potential to substitute for UV curing in microelectronic processing to improve the reliability of low-k dielectrics by mitigating the leakage currents and trapped charges induced by UV irradiation.

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