Recent findings validate that the company’s Sao™ copper electroplating chemistry does not impact the underlayer for damascene processes
MASSY, France – Jan. 23, 2018 – Aveni S.A., today announced surface analysis results that support the continued use of copper in the back end of line (BEOL) for advanced interconnects.
Small openings and high aspect ratio features reduce the ability to deposit continuous thin film layers into damascene structures – most notably the barrier and seed layers. Thus, alternative integration schemes for BEOL interconnects are being investigated. These include thinning the barrier metal, such as TaN (tantalum nitride) that prevents copper diffusion into the insulating material. Thinning of the cobalt liner and the copper seed layer, to which the copper electroplating solution adheres, are also common integration scheme practices. However, TaN, cobalt, and copper react with, or are etched in acidic copper electroplating solutions, causing discontinuity and oxidation of the thin film layers, resulting in electrical shorts.
Aveni has studied the integrity of the barrier and seed layers using XPS (x-ray photoelectron spectroscopy), with findings published July 19, 2018 in the Journal of the Electrochemical Society. http://jes.ecsdl.org/content/165/10/D439.short.Caillard et al,compared the chemical compositional changes that occur using acidic copper plating solutions versus Aveni’s alkaline ligand-based electroplating chemistry. Aveni’s alkaline plating solution prevent setching and oxidation of the barrier and seed layers.
Of interest is the cobalt liner, on which the copper is electrodeposited. Galvanic displacement and chemical etching both occur in acidic and alkaline plating chemistries; however, with Aveni’s alkaline plating solution, the rate of the galvanic displacement reaction is minimal compared with acidic plating solutions.
Since those layersare not oxidized, Aveni’s alkaline copper plating chemistry opens potential for cobalt liner removal and copper seed thinning, showing electrical and yield improvement from 22nm node to the most advanced nodes. Elimination of the costly cobalt liner allows more room for the electroplating solution to fill the vias. Additionally, high quality interfaces between the barrier and alkaline electroplated copper are achieved with Aveni’s electroplating solution. The high-quality interface is demonstrated by minimal micro-voiding and minimal oxidation, leading to minimal electromigration.
Frédéric Raynal, chief technical officer at Aveni, commented, “The results our R&D achieved are a breakthrough for the semiconductor industry. Aveni’s alkaline chemistry, which has already been demonstrated to achieve filling of 20:1 aspect ratios for through-silicon-vias, has now been shown to eliminate the use of the cobalt liners, resulting in higher electrical performance, reliability and yield.”
About Aveni S.A.
Aveni is the leading developer and supplier of market-disrupting wet deposition technologies and chemistries for advanced node interconnects and 3D through-silicon-via packaging using their patented Electrografting™ chemistries and processes. Headquartered in Massy, France, the company has a worldwide reputation for providing transformative chemistries and processes, coupled with the technology transfer capability to enable smooth transitions of its solutions into production.
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