defect structure and electronic transport in low-k films used for back end of line dielectrics

Open Access
Author:
Pomorski, Thomas Anthony
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
December 03, 2013
Committee Members:
  • Patrick M Lenahan, Thesis Advisor
  • S Ashok, Thesis Advisor
  • Jerzy Ruzyllo, Thesis Advisor
  • Suzanne E Mohney, Thesis Advisor
Keywords:
  • electronic materials
  • EPR
  • low-k
  • back end of line
Abstract:
This work focuses on electronic transport and defect structure in multiple novel dielectric systems used for back end of line (BEOL) applications. BEOL dielectrics with low dielectric constants, so called low-k dielectrics, and materials which can be used as etch stop layers which have lower dielectric constants than silicon nitride, are needed for current and future integrated circuit technology nodes. However, an understanding of the defects which limit reliability, degrade performance, and contribute to leakage currents in these films is not yet developed. In this research conventional electron paramagnetic resonance (EPR), leakage current, and electrically detected magnetic resonance (EDMR) measurements were utilized to investigate a-SiC:H and SiOC:H dielectrics. These dielectrics are believed to be the most important in future technology. In this study multiple variations in processing conditions, including post-deposition anneals, film chemistry, UV irradiation, and deposition techniques were analyzed. There is a strong correlation between conventional EPR defect density measurements and leakage currents in many of these films. There is also a very strong correlation between hydrogen content and both leakage current and EPR defect density for the a-SiC:H films. The SiOC:H films have a much more complex relationship between EPR defects and leakage currents. In many cases, a close correspondence between the EPR defect density measurement and the leakage currents strongly indicates that the defects observed by EPR are largely responsible for the leakage currents. These defects therefore likely limit the dielectric reliability, but the correspondence is imperfect. Important reliability phenomena in these films, which are likely limited by defects observed in this study, are time-dependent dielectric breakdown and stress induced leakage current. Additionally, EDMR via spin dependent trap assisted tunneling (SDT) has been utilized to investigate the direct link between defects observed in EPR defects and electrical transport.