Filling deep trenches and cavities is currently accomplished by copper electro-less plating technology utilizing super-conformal deposition methods. Unlike typical electrolyses processes, where an electric potential is applied between the anodes to activate the plating reaction, electro-less plating relies on chemical agents to activate deposition. To achieve super-conformal deposition, special electrolytic paths must be used. This poses a challenge to the fabrication of narrower trenches, and thus requires the development of other deposition schemes. This work proposes an alternative solution to the filling of deep trenches that avoids the difficulties outlined above, using a forced convection magneto-electroplating method. The technique operates as in typical electrolysis processes, however, with forcing the flow of the plating electrolyte, by hydro-dynamic means, in the presence of an externally applied magnetic field. This arrangement introduces a Lorentz type of force that enhances the transport of deposit species toward desired locations, such as deep regions in interconnect trenches. The proposed method is demonstrated by filling interconnect trenches with aspect ratio as high as 3:1. Quality of samples filled using the proposed magneto-electroplating method is compared with the quality of samples filled by typical electroplating method.
The presented work demonstrates that the ability of localized electro-deposition to fabricate truly three dimensional microstructures does not only require accurate control of the deposition electrode, but also demands a fabrication strategy that highly affects deposition resolution, characteristics, and the economical return of the technology. For this purpose, a synchronous deposition strategy is proposed utilizing two tip displacement algorithms. Both algorithms view three dimensional microstructures as stacks of lateral trajectories forming the structure's boundaries. In the first algorithm the synchronized tip positioning is implemented using tip stepped displacement, where the tip is moved from a point on a deposition trajectory to a neighboring location only upon sufficient deposition at the current location. The second algorithm, however, is implemented using continuous electrode displacement that allows deposition at all points along a trajectory while the tip is kept in continuous motion. The proposed synchronous deposition algorithms are demonstrated through the fabrication of micro-chambers and enclosures of arbitrary size and geometries. Comparison between both algorithms is concluded from SEM images of deposited structures in terms of deposit characteristics and strategy artifacts. The stepped displacement algorithm provides a shorter fabrication time but suffers from stepping artifacts. The continuous displacement algorithm, on the other hand, provides smooth boundaries but requires longer fabrication time that depends on the displacement speed of the deposition tip relative to the deposition growth rate.