Advancements in the semiconductor industry require new materials with
improved performance. With the introduction of copper as the interconnect material for
integrated circuits, efficient diffusion barriers are required to prevent the diffusion of
copper into silicon, which is primarily through grain boundaries. This dissertation
reports the processing of high quality stoichiometric thin films of TiN, TaN and HfN,
and studies their Cu diffusion barrier properties.
Epitaxial metastable cubic TaN (B1-NaCl) thin films were grown on Si(001)
using an ultra-thin TiN (B1-NaCl) seed layer which was as thin as 1 nm. The TiN/TaN
stacks were deposited by Pulsed Laser Deposition (PLD), with the TiN thickness
systematically reduced from 15 to 1 nm. Microstructural studies included X-ray
diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM
(HRTEM). Preliminary Cu diffusion experiments showed that the TiN seed layer
thickness had little or no obvious effect on the overall microstructure and the diffusion
barrier properties of the TaN/TiN stacks. Epitaxial and highly textured cubic HfN (B1-NaCl) thin films (~100 nm) were
deposited on MgO(001) and Si(001) using PLD. Low resistivities (~40 mu omega-cm) were
measured with a four point probe (FPP). Microstructural characterizations included
XRD, TEM, and HRTEM. Preliminary Cu diffusion tests demonstrated good diffusion
barrier properties, suggesting that HfN is a promising candidate for Cu diffusion
barriers.
Cubic HfN (B1-NaCl) thin films were grown epitaxially on Si(001) substrates by
using a TiN (B1-NaCl) buffer layer as thin as ~10 nm. The HfN/TiN stacks were
deposited by PLD with an overall thickness less than 60 nm. Detailed microstructural
characterizations included XRD, TEM, and HRTEM. The electrical resistivity measured
by FPP was as low as 70 mu omega-cm. Preliminary copper diffusion tests showed good
diffusion barrier properties with a diffusion depth of 2~3 nm after vacuum annealing at
500 degrees C for 30 minutes.
Additional samples with Cu deposited on top of the cubic HfN/TiN/Si(001) were
vacuum annealed at 500 degrees C, 600 degrees C and 650 degrees C for 30 minutes. The diffusivity of copper
in the epitaxial stack was investigated using HRTEM. The measured diffusion depths,
2 Dt , were 3, 4 and 5 nm at 500 degrees C, 600 degrees C and 650 degrees C respectively. Finally, the
diffusivity of Cu into epitaxial HfN was determined to be D=D0 exp(-Q/kT)cm2s-1 with D0=2.3x10-14cm2s-1 and Q=0.52eV.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-12-159 |
| Date | 14 January 2010 |
| Creators | Araujo, Roy A. |
| Contributors | Wang, Haiyan, Cagin, Tahir |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation |
| Format | application/pdf |
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