Title page for ETD etd-04042005-171306


Type of Document Dissertation
Author Wang, Lidong
Author's Email Address wang_lidong@yahoo.com
URN etd-04042005-171306
Title Chemical Vapor Deposition of Thin Films for ULSI Interconnect Metallization
Degree Doctor of Philosophy (Ph.D.)
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Gregory L.Griffin Committee Chair
Andrew W. Maverick Committee Member
Douglas P. Harrison Committee Member
Kerry M. Dooley Committee Member
Kenneth Matthews Dean's Representative
Keywords
  • palladium
  • Cu(hfac)2
  • Pd(hfac)2
  • copper
  • interconnect metallization
  • reaction mechanism
  • chemical vapor deposition
  • tantalum
  • barrier layer
  • seed layer
  • TaF5
  • SiH4
  • electroless deposition
Date of Defense 2005-03-31
Availability unrestricted
Abstract
We have studied the kinetics of copper chemical vapor deposition (CVD) for interconnect metallization using solution delivery of Cu(hfac)2 (Cu(II) hexafluoroacetyl-acetonate) dissolved in isopropanol. We observe a growth rate of 17.7 b 1.5 nm/min at reference conditions of 300aC substrate temperature, 0.025 Torr Cu(hfac)2 partial pressure, 1.6 Torr isopropanol (reducing agent), and 80 Torr H2 (carrier gas). The film resistivity approaches the bulk value of copper for film thickness greater than 100 nm. Reaction order experiments show first-order kinetics with respect to Cu(hfac)2 partial pressure and zero-order with respect to isopropanol.

A series reaction mechanism including three kinetically significant steps (adsorption of Cu(hfac)2, dissociation of (hfac) ligand, and desorption of (hfac)) is used to describe the observed kinetic results. The proposed rate determining step is the dissociation of (hfac) ligand when the pressure ratio of Cu(hfac)2 to isopropanol is low, and becomes the desorption of (hfac) when the pressure ratio is high.

We also examined a low temperature chemical vapor deposition process for the growth of tantalum thin films using SiH4 reduction of TaF5. Using a temperature of 350aC and reactant partial pressures of 0.2 Torr TaF5 and 0.3 Torr SiH4, we obtain a growth rate of 2.2 1.7 nm/min. The XPS analysis results show that the Ta film is Si free, but contains relatively high oxygen concentration because of residual gas contamination.

Lastly, we have studied a batch CVD process for palladium seed layer deposition using H2 reduction of Pd(hfac)2 (Pd(II) hexafluoroacetylacetonate). Nano-sized Pd particles with nuclei density between 1 to 14 clusters/m2 are observed using AFM. The quality of the Pd seed layer is examined by depositing electroless copper film. We have investigated the influence of CVD operating conditions (deposition time, activation temperature, and precursor concentration) on the activity of the Pd seed layers (i.e., by monitoring visual appearance and deposition rates of the ELD Cu films). At the optimized conditions we can deposit uniform Cu films at a rate of 3.4 b 1.4 nm/s. Additional work is needed to improve the resistivity and adhesion of the films.

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