Paramagnetic Defect Generation and Microstructure Change in Porous Low-k SiOCH Films with Vacuum Baking

Applied Physics Letters

et al. 2015

In this work, core-level X-ray photoelectron spectroscopy was utilized to determine the surface bandgap for various porous and non-porous low-k a-SiCOH dielectrics before and after ion sputtering. By examining the onset of inelastic energy loss in O 1s core-level spectra, the gap narrowing was universally found in Ar þ ion sputtered low-k dielectrics. The reduction of the bandgap ranges from 1.3 to 2.2 eV depending on the film composition. We show that the bandgap narrowing in these low-k dielectrics is caused by development of the valence-band tail as evidenced by the presence of additional electronic states above the valence-band maximum. Electron-spin-resonance measurements were made on a-SiCOH films to gain atomic insight into the nature of the sputtering-induced defects and reveal formation of carbon-related defects as the most probable origin of the gap states.

mentioning

confidence: 99%

Defect-induced bandgap narrowing in low-k dielectrics

Guo

Zheng

Applied Physics Letters

et al. 2015

“…56,57 Despite numerous electrical-based measurements identifying a range of bulk and interfacial point defects and traps in low and high-k materials, [58][59][60][61][62][63][64][65][66][67][68][69][70] very little is still known about the actual chemical identity and structure of these defects. A number of electron spin resonance (ESR) studies of low-k [70][71][72][73] and high-k 74-80 a) materials have provided some hints experimentally toward the identification of some point defects in these materials. However, theoretical investigations have so far provided the most insight into both the structure and chemical identity of the various possible point defects in high-k materials.…”

Section: Introductionmentioning

confidence: 99%

“…73,122 In contrast to high-k dielectrics, ESR measurements on porous and nonporous low-k SiOC:H dielectrics have pointed to a variety of different silicon and carbon dangling bond defects within the bulk of low-k materials. [70][71][72][73] However, in most cases, the location of these defects within the low-k band gap and their correlation to electrical reliability are not clear. 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.…”

Section: Introductionmentioning

confidence: 99%

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

French

2013

J. Mater. Res.

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.

“…Electron spin resonance (ESR) techniques have been utilized to detect the existence of unpaired electron "spin" defects in low-k materials, and these defects have been attributed to both silicon and carbon dangling bonds. 22,23,[25][26][27] These assignments have been based on either analogies between the position of the spin g-value with known dangling bond defects in related materials, [25][26][27] or correlations to changes in chemical bonding observed using transmission Fourier transform infra-red (FTIR) spectroscopy. 22,23,26 In both cases, these assignments are not completely definitive due to the inability to detect isotopic hyperfine interactions in the ESR spectra.…”

mentioning

confidence: 99%

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

Journal of Applied Physics

French

Mays

2013

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.