Investigating area selective chemical vapor deposition achieved by competitive adsorption
Madhyastha, Vidyesh Parampalli
As device feature sizes shrink to single digit nanometer scale, researchers and industries are moving away from the conventional top-down approach and relying on a bottom-up approach for device fabrication. Contemporary top-down techniques involving photolithography and etching result in misalignment errors at sub-5 nm scales. Area selective deposition is a recent advanced bottom-up fabrication technique with the potential to sustain the trend as described by Moore’s law. The approach involves a modified version of chemical vapor deposition (CVD) of a high dielectric constant metal oxide, Zirconia (ZrO2). High dielectric constant oxides such as Zirconia or Hafnia can replace conventional gate oxides such as silica in future generation CMOS devices. Three types of substrates namely SiO2, Cu, and Co are studied in this thesis. A procedure was identified to obtain an oxide-free surface of cobalt. Substrates are exposed to a precursor and a co-reactant, and thin film deposition was investigated using X-Ray Photoelectron Spectroscopy (XPS). A third gas phase molecule referred to as “co-adsorbate” was exploited to deposit ZrO2 thin films only on one type of surface in the presence of another. XPS was used to calculate the thickness of these thin films and to investigate their composition. Partial pressure of the co-adsorbate - 4-octyne, in the presence of N2, was measured under different flow conditions. Density Functional Theory (DFT) calculations suggest that 4-octyne binds to substrates as: Highest on Co and lowest on SiO2. Regarding Cu and SiO2, 4-octyne undergoes carbon bond rehybridization with Cu, whereas it only interacts with SiO2 by van der Waals forces. The difference in binding energies paves way to selective deposition between Cu and SiO2 at optimized substrate temperatures and vapor pressures of co-adsorbate. Preliminary AS-CVD studies were also performed between Co and Cu.
4-octyne; Area selective deposition; chemical vapor deposition; co-adsorbate; competitive adsorption; dielectric-on-dielectric
Engstrom, James R.
Xing, H. Grace
Materials Science and Engineering
M.S., Materials Science and Engineering
Master of Science
dissertation or thesis