Precursor design and reaction mechanisms for the atomic layer deposition of metal films

Editors' Choice—Review—Cobalt Thin Films: Trends in Processing Technologies and Emerging Applications

“…• CoCp 2 (Co-203) with a (N 2 +H 2 ) plasma at 300 • C; a N 2 /H 2 flow ratio of 33% produced metallic Co with the lowest resistivity (20µ cm). The authors point out that this percentage corresponds to the atomic ratio in NH 3 molecule and argue for the importance of NH 3 radicals in the clean cleavage of CoCp 2 (Co-203) to yield Co. 51 The same finding was reported with CpCo(CO) 2 Co-103 and NH 3 versus H 2 plasma; the latter produced Co films with C contamination, while the former yielded pure Co at 300 • C. 20,51 • Co(MeCp) 2 (Co-204) and CoCp 2 (Co-203) were both tested with NH 3 versus H 2 plasma at 100-350 • C, 36 with only NH 3 plasma depositing Co metal. The investigators concluded that the presence of NH 3 radicals is critical to obtain Co metal, which is consistent with other reported results.…”

“…Thermal Co ALD is categorized by: (1) the introduction of the Co source precursor and co-reactant in sequential rather than simultaneous stages, with intervening purge steps to ensure that the co-reactants never cross paths in the reaction zone and that no reactions occur except on the substrate surface; and (2) Co film growth proceeding through self-limiting surface reactions that ensure precise control of film thickness and conformality with atomic level accuracy. 20,[51][52][53] These characteristics suggest the realization of excellent film conformality in extremely aggressive device topographies. The addition of plasma to one of the co-reactants (e.g., H 2 or NH 3 ) has also been shown to enhance the ALD reaction and increase film growth rates by creating a higher concentration of active co-reactant radicals.…”

Controlling the Thermal Stability and Volatility of Organogold(I) Compounds for Vapor Deposition with Complementary Ligand Design

“…While this was fruitful for gold, as shown by both reported processes using previously reported CVD precursors, this selection process only returns a handful of molecules that are often quite different from one another in their structure and chemistry. ALD precursor design for other materials is quite mature in some cases and has been proven to be a useful tool in accelerating process development for Cu, Ru, Co, Ni, and many other metallic films , . As such, we felt that a thorough study on the fundamental factors that govern thermal stability and volatility would be useful in the development of new gold ALD precursors.…”

(Invited) Catalytic Surface Reactions during Nucleation and Growth of Atomic Layer Deposition of Noble Metals: A Case Study for Platinum

“…Furthermore, also processes for the deposition of Os, Rh, Ir, and Ag have been developed (6)(7)(8)(9). The deposition of noble metals by ALD is more successful as compared to the deposition of most other transition metals due to the fact that noble metals have a positive reduction potential (10), allowing for the use of oxygen gas as the reactant. The most adopted processes for noble metal ALD therefore consists of alternating pulses of a volatile metalorganic precursor and O 2 gas at an elevated temperature of 200 -400 °C (11,12).…”