Novellus Systems has developed a new Hollow Cathode Magnetron (HCM) IONX PVD copper seed process that is expected to enable copper interconnects below the 2xnm technology node. The company said that the enhancement will allow the company’s HCM PVD technology, on the INOVA platform, to continue to be used for barrier and seed thin film deposition, avoiding the migration to ALD or CVD approaches.
According to the company, PVD copper barrier/seed and copper electrochemical deposition have been in use to build logic devices for long. Memory manufacturers are transitioning to copper interconnects now. As the critical dimensions (CD) of via and trench structures decrease with advanced technology nodes, PVD deposition technology becomes limited by its lack of conformality. Copper seed requirements call for about 100A of film thickness in the field to minimise the electroplating terminal effect, as well as >20A of continuous film within the structure to ensure void-free copper fill.
The company said that the excessive overhang at the top of the feature could lead to a reduction in the size of the opening, also known as ‘pinch-off’ and this constriction in the copper seed layer leads to insufficient copper fill of these small structures, resulting in voiding and poor device reliability. Extending PVD copper seed to 2xnm nodes and beyond requires a new approach that is not constrained by typical step coverage performance.
Wai-Fan Yau, general manager for Novellus’ integrated metals business unit, said: This latest innovation in HCM technology will extend PVD copper seed to the 22nm node and beyond. Our advanced copper seed offers the ability to fill ultra-small features, resulting in increased device reliability, without having to introduce more complicated and costly CVD or ALD processes into the manufacturing sequence.
The company has also developed plasma confinement and focusing magnetic for the INOVA HCM sputtering source that enables control of PVD overhang, step coverage, and bottom-up fill. The company’s copper seed process operates in a regime that results in bottom-up feature fill versus conformal deposition. This copper seed approach is claimed to reduce the pre-plating aspect ratio and increase the process window for subsequent void-free copper fill.
