| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM+AS+PS+TF-ThM |
| Session: | Materials and Process for Advanced Interconnects I |
| Presenter: | M. Nichols, University of Wisconsin-Madison |
| Authors: | M. Nichols, University of Wisconsin-Madison Q. Lin, IBM T.J. Watson Research Center S. Banna, Applied Materials Inc. Y. Nishi, Stanford University J.L. Shohet, University of Wisconsin-Madison |
| Correspondent: | Click to Email |
The experimental measurements of the electronic band gap of low-k organosilicate dielectrics are presented and discussed. The measurement of bandgap energies of organosilicates was made by examining the onset of inelastic energy loss in core-level atomic spectra using x-ray photoelectron spectroscopy (XPS). This energy serves as a reference point from which many other facets of the material can be understood, such as the location and presence of defect states in the bulk or at the interface. In order to measure the spectra due inelastic energy loss, a suitable primary photoelectron peak must be chosen. Although in principle any core-level spectra will exhibit the same inelastic losses, the measured photoelectron intensity must be large enough so that a sufficient signal to noise ratio can be achieved with suitably high resolution. It was determined that the O 1s peak is dominant for both SiO2 and for the organosilicate films used in this work.
To find the bandgap energy, a linear fit is made to the measured loss spectra curve near the approximate location of onset of inelastic losses. The energy corresponding to the onset of inelastic losses, is found by extrapolating the linear fit line and calculating its intersection with the “zero” level. The bandgap energy is equal to the difference between the core level peak energy and the onset of inelastic losses. For SiO2 this method yields a bandgap energy of 8.8 eV which is in excellent agreement with the established value of 8.9 eV. Bandgap energies were measured for 644 nm k=2.75 as-deposited SiCOH films using the linear extrapolation method, yielding a bandgap energy of Eg = 7.0 eV. For 500 nm thick k=2.65 SiCOH the bandgap energy was found to be 7.7 eV while for a 325 nm thick, k = 2.75 photopatternable low-k (PPLK) dielectric, the bandgap was found to be 8.25 eV.
This work has been supported by the Semiconductor Research Corporation under Contract No. 2012-KJ-2359 and by the National Science Foundation under Grant CBET-1066231.