| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Thursday Sessions |
| Session EM-ThA |
| Session: | Materials and Process for Advanced Interconnects II |
| Presenter: | Y. Suzuki, University of Tokyo, Japan |
| Authors: | Y. Suzuki, University of Tokyo, Japan H. Shimizu, University of Tokyo, Japan T. Momose, University of Tokyo, Japan Y. Shimogaki, University of Tokyo, Japan |
| Correspondent: | Click to Email |
Reaction mechanism of chemical vapor deposition (CVD) for Co using amidinate precursor was examined by introducing multi-scale analysis using cold-wall reactor equipped with macrocavity. We thereby found that Co film growth by direct surface decomposition of the source precursor was negligible and the intermediate species generated by gas-phase reaction was the major species.
Ongoing shrinkage of ULSI devices manifests EM/SIV reliability issues originated from poor adhesion between Cu and underlying material. The higher effective resistivity caused by the shrinkage of Cu lines is another concern. These issues suggest the necessity of more adhesive and conductive material for Cu liner/barrier layer instead of conventional Ta/TaN bi-layer. We proposed Co(W) monolayer film as a hopeful candidate to solve these issues [1]. The poor step coverage of PVD is also a problem in future technology. We, therefore, worked on the CVD of Co(W), and proved better barrier property and lower resistivity than Ta/TaN. This paper is focusing on Co-CVD kinetics from Co(tBuNC(Et)NEt)2 (Co-amidinate) [2] and NH3 as a basis of Co(W)-CVD.
We firstly used cold-wall chamber to focus on the surface reaction kinetics. Arrhenius plot of deposition rate showed two slopes corresponding to surface-reaction- and diffusion-limited regime. Mass transfer coefficient estimated from the growth rate under diffusion-limited regime has 200 times lower than that from fluid dynamics. This suggested that major deposition species was not the precursor itself, but intermediate species generated from the precursor near by the heated substrate. Deposition rate dependence on precursor partial pressure was then studied under reaction-limited condition, which showed Langmuir-Hinshelwood reaction kinetics. Surface reaction rate constants were finally extracted.
Gas-phase reaction kinetics were analyzed by macrocavity installed in the cold-wall chamber. Macrocavity consists of two facing substrates with variable spacing. The spacing of the macrocavity controls surface to volume ratio, which in turn changes the contributions of gas-phase reaction over surface reaction [3]. Film thickness profile within the macrocavity was compared with that by finite element simulation of diffusion equations coupled with the experimentally obtained surface reaction kinetics. We could finally obtained gas-phase reaction rate constant.
As a summary, we successfully analyzed reaction mechanism of Co-CVD using amidinate precursor, which enables to design the wafer-scale reactor. Our results show the importance of controlling gas-phase reactions when we use this precursor for CVD-Co as ULSI-Cu liner application.