AVS 62nd International Symposium & Exhibition
    Electronic Materials and Processing Wednesday Sessions
       Session EM-WeA

Paper EM-WeA12
Bandgap Narrowing in Low-K Dielectrics

Wednesday, October 21, 2015, 6:00 pm, Room 210E

Session: Interconnects: Methods and Materials for Removing Connectivity Constraints
Presenter: Xiangyu Guo, University of Wisconsin-Madison
Authors: X. Guo, University of Wisconsin-Madison
S.W. King, Intel Corporation
P. Xue, University of Wisconsin-Madison
J.-F. de Marneffe, IMEC, Belgium
M. Baklanov, IMEC, Belgium
V. Afanas'ev, Catholic University of Leuven, Belgium
Y. Nishi, Stanford University
J.L. Shohet, University of Wisconsin-Madison
Correspondent: Click to Email
Electrical reliability in Cu interconnect structures has become a vital concern as the nano-electronics industry moves to sub-16 nm technology nodes and strives to implement insulating dielectric materials with increasingly lower dielectric constants (i.e., low-k). Studies have shown a direct correlation between trap/defect densities and electrical leakage of low-k materials,1,2 , while the knowledge of the fundamental mechanism producing the damage is still limited. The bandgap energy, often serving as a reference point from which the presence and location of defect states in the bulk or at the interface can be understood, is of fundamental importance for understanding the electrical degradation in these dielectrics. In this work, core-level X-ray photoelectron spectroscopy (XPS) was utilized to determine the surface bandgap for various non-porous and porous low-k a-SiCOH dielectrics before and after ion sputtering by examining the onset of inelastic energy loss in core-level atomic spectra. Bandgap narrowing was observed in Ar+ ion sputtered low-k dielectrics. The reduction of bandgap energies ranges from 1.3 Ev to 2.2 Ev depending on the film composition. By examining the valence-band spectra measured with high-resolution XPS, we show that the bandgap narrowing in the low-k dielectrics is contributed to the arising and uplifting of the valence-band tail as evidenced by the presence of additional electronic states above the valence-band maximum (VBM). Electron spin resonance (ESR) measurements were also performed on the a-SiCOH films and the localization of each type of defect within the dielectric band gap is analyzed and compared. A combination of these results with the band gap measurements suggests the additional electron states contributing to the narrowed bandgap originate from carbon-related defects in the material. This work was supported by the National Science Foundation under Grant CBET-1066-231 and by the Semiconductor Research Corporation under Contract 2012-KJ-2359.

1. J. Atkin, D. Song, T. Shaw, E. Cartier, R. Laibowitz, and T. Heinz, J. Appl. Phys. 103, 94104 (2008).

2. B. Bittel, P. Lenahan, and S.W. King, Appl. Phys. Lett. 97, 63506 (2010).