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Dissertation
Development of a multi-layer metallization scheme using titanium nitride as a diffusion barrier
Doctor of Philosophy (Ph.D.), Drexel University
1988
DOI:
https://doi.org/10.17918/00007788
Abstract
As the VLSI dimensions approach 1[mu]M and smaller size, reliability of the contact metallizations is degraded due to spiking and interdiffusion between silicon and aluminum. The deposition and properties of reactively sputtered thin films were investigated for their use in integrated circuits as a diffusion barrier in the Al/TiN/Ti/Si metallization scheme. The effect of deliberate introduction of oxygen and variation of deposition parameters such as applied substrate bias and nitrogen partial pressure on the film properties was studied, and the films were characterized by RBS, AES, XPS, SEM and TEM. Depending on the sputtering parameters, two distinctly different types (brown and golden) of titanium nitride films were obtained. The golden colored films (G films) have dense microstructure and high compressive stress, while the brown films (B films) have columnar grain structure with inter-grain voids, 5-8% oxygen contamination and very small intrinsic stress. A new model based on the microstructure of thin films for the generation of intrinsic stress in sputtered thin films is presented. To examine the diffusion barrier properties of these films, Kelvin cross structures were fabricated on SOS wafers with contact holes of sizes varying from 1.0[mu]m x 0.5[mu]m to 3.0[mu]m x 3.0[mu]m in size. Different metallization schemes such as Al/Si, Al/TiN/Si, Al/TiN/Ti/Si and Al/TiOxNy/Ti/Si in the temperature range 450-600[degrees]C were compared for contact resistivity and reliability during heat-treatment. The statistical data on the failure rate and contact resistance is presented. Also, the failure analysis of the failed contacts is described. It was found that the G films are better diffusion barriers for silicon diffusion than the B films, but their effectiveness is reduced due to the formation of Al3Ti compound during heat-treatment. The incorporation of oxygen in the TiN barrier film reduces the contact failure rate by grain boundary stuffing and by inhibiting the formation of Al3Ti. Based on the results of this research, a new metallization scheme (Al/TiN(B)/TiN(G)/Ti/Si is proposed and shown to have excellent thermodynamic and electric properties.
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Details
- Title
- Development of a multi-layer metallization scheme using titanium nitride as a diffusion barrier
- Creators
- Nalin Kumar
- Contributors
- Kambiz Pourrezaei (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xix, 217 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021888890704721