ELECTRICAL CHARACTERIZATION OF THE EPITAXIAL INTERFACE BETWEEN Ba0.7Sr0.3O AND SILICON

Open Access
Author:
Billman, Curtis A
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
July 26, 2007
Committee Members:
  • Darrell Schlom, Committee Chair
  • Suzanne E Mohney, Committee Member
  • Jerzy Ruzyllo, Committee Member
  • Susan E Trolier Mckinstry, Committee Member
  • Fredrick Walker, Committee Member
Keywords:
  • epitaxial interface
  • conductance technique
  • in situ probe station
Abstract:
Methodologies were developed to electrically characterize the epitaxial interface of barium strontium oxide (Ba0.7Sr0.3O) on silicon. Ba0.7Sr0.3O is reactive with moisture in air; therefore, these methodologies enable the fabrication of and characterization of Ba0.7Sr0.3O metal oxide semiconductor (MOS) devices in ultra-high vacuum (UHV). Silicon lattice matched Ba0.7Sr0.3O was expected to tie up Si dangling bonds and result in essentially no interface states, but conductance and capacitance measurements revealed evidence of Bloch states due to the growth method and well-ordered structure of the interface between Ba0.7Sr0.3O and Si. The conductance can measure interface states through an energy loss associated with charge exchange between the interface states and the silicon. Conductance measurements of the interface states between Ba0.7Sr0.3O and Si show energy loss peaks that can be modeled using a single relaxation time in contrast to interface states at the amorphous SiO2 / Si interface, and this is evidence that the interface states exhibit Bloch state characteristics and not localized interface state characteristics. These are the first measurements of Bloch states at an epitaxial interface. In situ device fabrication and characterization methodologies are especially advantageous for not only testing this material system, but also for testing other device structures as dimensions approach the nano-scale and environmental sensitivity becomes a concern. Excellent agreement was obtained between an air ambient ex situ and in situ probe station measurements utilizing a sapphire capacitor standard compatible with UHV. The measurements show less than 0.3 % dispersion for frequencies from 20 Hz to 1 MHz. MOS capacitors measurements show a sensitivity to a density of interface states of 1x1010 states cm-2 eV-1. These measurements also show 0.5 % dispersion for measurement frequencies from 20 Hz to 1 kHz and less than 0.1 % from 1 kHz to 1 MHz.