Strem Chemicals UK releases a novel precursor for CVD/ALD for the production of ruthenium containing films
This ruthenium amidinate precursor is expected to have many applications in next generation DRAM, LOGIC and NAND Devices
Ruthenium has become one of the most promising materials for next-generation semiconductor devices. Ru is considered the best candidate for the electrode capacitor in DRAM applications. It possesses all of the required properties including high melting point, high oxidation resistance, and low resistivity, making it an excellent candidate for gate electrode material in CMOS transistors. Ruthenium’s lower resistivity and ease of dry etching give it a significant advantage over iridium and platinum. Ru also shows promise as a glue-layer or seed-layer material for copper. Ruthenium oxide is conductive so that the diffusion of oxygen coming from adjacent materials or processes will not affect the device. In addition, recent research mentions the use of ruthenium-based materials as an electrode for ferroelectric applications.
Many types of Ruthenium precursors are available and have been used to grow CVD and ALD films. Most of these, however, have negative properties including low vapor pressure and high impurity levels, such as carbon and oxygen, which get incorporated in the films. Additionally, there are other concerns such as long incubation times (which affect the throughput and process controllability), poor film adherence and non-uniformity in deep trenches. Amidinate precursors such as Bis(N,N’-di-t-butylacetamidinato)ruthenium(II) dicarbonyl (44-0056) CAS Number: 949113-49-9 have characteristics that overcome some of these issues. Each amidinate ligand chelates the metal centre through two metal-nitrogen bonds. These relatively weak M-N bonds and strong by product N-H bonds lead to lower ALD growth temperatures.
However, the M-N bonds are strong enough to provide stability to the precursor at the standard temperatures used. Also, since the amidinato ligands chelate to the metal centre, they are thermally stable yet have high and self-limited reactivity to water vapor which is essential for ALD.1 Amidinates do not have any oxygen-metal bonds thus enabling the deposition of metallic films with very low oxygen content in the film and at the interface with the sub-layer.
Thin films deposited by ALD using Bis(N,N’-di-t-butylacetamidinato)ruthenium(II) dicarbonyl have been found to be highly conductive, dense and pure. Analysis by atomic probe microscopy showed crystallites nearly free of carbon impurity with a low level segregated near the grain boundaries.2 Highly pure and conductive films have been conformally deposited inside holes with aspect ratios of 40:1.3 TheseRu films also exhibited strong adhesion.2 This precursor was found to be thermally stable in a bubbler at 1300C for months and showed very clean TGA vaporization with only trace residue (0.2%).4
CAS Number: 949113-49-9
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