Defect-induced bandgap narrowing in low-k dielectrics

Abstract

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.

Charge-trapping memory based on tri-layer alumina gate stack and InGaZnO channel

“…The band edge of the carbon-related defects in the O3-Al2O3 film may shift deep into the forbidden gap, which could form band tails gap and reduce the effective band gap of the film. 31,32 The valence band offset (ΔEV = 0.45 eV) of the Al2O3 films was calculated from the valence band spectra, as shown in Fig. 5 inset of Fig.…”

Valence and conduction band offsets for sputtered AZO and ITO on (010) (Al0.14Ga0.86)2O3

“…Figure 2 shows the stacked XPS survey scans of thick (150 nm) AZO and ITO, 1.5 nm AZO and ITO on β-(Al 0.14 Ga 0.86 ) 2 O 3 , and an (Al 0.14 Ga 0.86 ) 2 O 3 reference sample. There is no evidence of metallic contamination from the sputtering process, which if present in sufficient quantities can form oxides that reduce the overall bandgap of the dielectrics and affect the resulting band alignment [47][48][49][50].…”

Measurements of Schottky barrier at the low-k SiOC:H/Cu interface using vacuum ultraviolet photoemission spectroscopy

“…[5][6][7] One critical challenge is electrical leakage at the interface between Cu and low-k dielectrics, particularly as electric fields approach 1 MV/cm or greater for <10-nm technology nodes. 8,9 Since interfacial barriers can play an important role in determining the charge transport characteristics and the potential electrical leakage mechanisms between materials, there is a critical need to understand the fundamental electronic band alignment between low-k interlayer dielectrics and Cu lines. 10,11 The other driving force that requires characterization of the band alignment between Cu/low-k dielectric interfaces is the need for reducing the k-value of the Cu capping/etch stop layer, since the capping layers (a-SiC x N y :H) typically have the highest k-values in conventional Cu interconnect structures.…”

“…The bandgap energy of the a-SiOC:H thin film was determined to be 8.1 6 0.3 eV using X-ray photoemission spectroscopy (XPS). 9 Monochromatic vacuum ultraviolet exposures were made using a synchrotron radiation apparatus described previously. 22 The incident VUV photon beam, with a crosssection of 3.0 Â 0.1 cm 2 , was oriented normally to the surface of the sample at a pressure of 10 À8 Torr.…”

“…A photon energy of 8.1 eV is approximately the bandgap energy of the low-k dielectric. 9 The VUV re-exposure was performed at the same location on the sample with the same photon dose of 5.0 Â 10 15 photons/cm 2 , as was the case for the 12 eV exposure. VUV photoemission spectroscopy was re-measured after the second exposure.…”