Effects of vacuum ultraviolet radiation on deposited and ultraviolet-cured low-k porous organosilicate glass

Sinha, H.; Antonelli, G. A.; Jiang, Gengwei; Nishi, Yoshio; Shohet, J. L.

doi:10.1116/1.3570818

Cited by 16 publications

(11 citation statements)

References 23 publications

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“…To complicate matters, further ESR studies have shown that additional defects can be created in low-k materials by downstream porogen removal and plasma etching processes that expose the low-k material to intense UV-VUV radiation, energetic ions, and chemically active radicals and neutrals. [123][124][125][126][127] These process-induced defects may not be present or dominant in the as-deposited material. Accordingly, understanding the exact nature of the electrical point defects in low-k materials fully integrated into actual metal interconnect structures is quite complicated and difficult to unravel.…”

Section: Introductionmentioning

confidence: 97%

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

French

King

2013

J. Mater. Res.

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The continuation of Moore's law requires new materials at both extremes of the dielectric permittivity spectrum and an increased understanding of the fundamental mechanisms limiting their electrical reliability. To address the latter, reflection electron energy loss spectroscopy has been utilized to measure the band gap of various oxide-based low and high dielectric constant (k) materials of interest to the semiconductor industry. In situ Ar 1 sputtering has been additionally utilized to simulate process-induced defect states that are believed to contribute to electrical leakage, time-dependent dielectric breakdown, charge trapping, and other fixed-charge reliability issues in nano-electronic devices. It is observed that Ar 1 sputtering predominantly generates surface oxygen vacancy defects in the upper portion of the band gap for both low and high-k dielectric materials. These results are in agreement with numerous theoretical investigations of defects in low and high-k dielectric materials and models for mechanisms that limit their reliability.

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Section: Introductionmentioning

confidence: 97%

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

French

King

2013

J. Mater. Res.

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“…1,7 For low-k materials, it has been additionally shown that electrical traps and defects can be created by downstream porogen removal and plasma etching processes that expose the low-k material to intense UV-VUV radiation, energetic ions, and chemically active radicals. [17][18][19][20][21][22][23] Further studies have shown a direct correlation between trap/defect densities, leakage currents and TDDB failures. 18,24 Unfortunately, the current understanding of the chemical identity, structure, and energy level of electrical traps and defects in low-k materials is still limited.…”

mentioning

confidence: 97%

Detection of defect states in low-k dielectrics using reflection electron energy loss spectroscopy

King

French

Mays

2013

Journal of Applied Physics

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A reverse Monte Carlo method for deriving optical constants of solids from reflection electron energy-loss spectroscopy spectra Reflection electron energy loss spectroscopy (REELS) has been utilized to measure the band gap (E g ) and energy position of sub-gap defect states for both non-porous and porous low dielectric constant (low-k) materials. We find the surface band gap for non-porous k ¼ 2.8-3.3 a-SiOC:H dielectrics to be ffi 8.2 eV and consistent with that measured for a-SiO 2 (E g ¼ 8.8 eV). Ar þ sputtering of the non-porous low-k materials was found to create sub-gap defect states at % 5.0 and 7.2 eV within the band gap. Based on comparisons to observations of similar defect states in crystalline and amorphous SiO 2 , we attribute these sub-gap defect states to surface oxygen vacancy centers. REELS measurements on a porous low-k a-SiOC:H dielectric with k ¼ 2.3 showed a slightly smaller band gap (E g ¼ 7.8 eV) and a broad distribution of defects states ranging from 2 to 6 eV. These defect states are attributed to a combination of both oxygen vacancy defects created by the UV curing process and carbon residues left in the film by incomplete removal of the sacrificial porogen. Plasma etching and ashing of the porous low-k dielectric were observed to remove the broad defect states attributed to carbon residues, but the oxygen vacancy defects remained.

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“…It must be mentioned although the density of trapped charges is relatively small, 3,7,8 that post treatment (e.g., UV exposure 12,13 and hydrogen annealing 17,18 ) might still be needed to make sure that there is no significant net charge generated due to photoemission. 13 As a result, the trapped charges within the bandgap of the dielectric are reduced, the defect states are passivated and electrical activity is mitigated 19 since trapped charges are shifted out of the band-gap of the low-k dielectric. 20 To prove this hypothesis, monochromatic photons between 7.6 and 8.9 eV were exposed on the samples.…”

Section: Effects Of Vacuum Ultraviolet Irradiation On Trapped Chargesmentioning

confidence: 99%

“…14 Higher photon energies were not selected since they could also generate large charge accumulation and affect the reliability of SiCOH films. 13 In addition, based on the relation between the wavelength of the VUV photons and their penetration depth in low-k dielectrics, 16 those photons with energies from 4.5 to 8.9 eV can easily penetrate through the dielectric layer. Finally, the normalized photoemission currents induced by different photon energies in these ranges are comparable.…”

Section: Effects Of Vacuum Ultraviolet Irradiation On Trapped Chargesmentioning

confidence: 99%

“…5 When the energy supplied by irradiation is greater than the sum of the band-gap energy and the electron affinity, photoemission can occur from the dielectrics. 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: 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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Effects of vacuum ultraviolet radiation on deposited and ultraviolet-cured low-k porous organosilicate glass

Cited by 16 publications

References 23 publications

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

Detection of surface electronic defect states in low and high-k dielectrics using reflection electron energy loss spectroscopy

Detection of defect states in low-k dielectrics using reflection electron energy loss spectroscopy

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

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