STUDY OF DEFECT STRUCTURE AND ELECTRICAL TRANSPORT IN BACK END OF LINE DIELECTRICS AND SIC MOSFETS

Open Access
Author:
Bittel, Brad
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
December 12, 2011
Committee Members:
  • Patrick M Lenahan, Dissertation Advisor
  • Patrick M Lenahan, Committee Chair
  • Suman Datta, Committee Member
  • Joan Marie Redwing, Committee Member
  • Jerzy Ruzyllo, Committee Member
Keywords:
  • magnetic resonance
  • EPR
  • low-k
  • BEOL
  • SiC
Abstract:
SiC MOSFETs show great potential for use in high power and high temperature environments. However, the technology is still in its infancy and is limited by low field effect mobilities (25cm2/Vsec) and unstable threshold voltages (Vt shifts of 5V have been reported at 175°C). Electron paramagnetic resonance (EPR) is a tool that can identify the physical and chemical nature of point defects responsible for limiting the performance of semiconductor / dielectric systems. EPR studies have the potential to aid in the amelioration of problems caused by these defects. We utilize several magnetic resonance approaches, including conventional EPR on blanket SiC/SiO2 structures, spin dependent recombination, and a new characterization technique, spin dependent charge pumping on fully processed SiC MOSFETs. Low dielectric constant materials for use as interlayer dielectrics (ILDs) and etch stop layers (ESLs) for back end of line (BEOL) applications have been investigated with EPR. We have examined a wide array of films composed of SiOC, SiO2, SiN, SiNC, and SiC to help build an understanding of the defects which limit reliability and cause increased leakage current. A strong dependence on film chemistry as well as processing parameters such as deposition technique, post deposition anneal temperatures, and UV curing is observed with EPR defect densities, which are correlated to leakage current measurements. We further correlate leakage currents to EPR results by utilizing a technique called spin dependent trap assisted tunneling in several capacitor structures.