One of the challenges of TSVs is that they’re deeper than other vias and features. Drilling those babies uses deep reactive ion etching (DRIE), which we discussed in our MEMS article earlier in the year. The Bosch process, in particular, consists of a series of etch and clean steps that can leave scalloped sidewalls and other rough features that can be hard to cover properly when filling with metal.
French company Alchimer, which focuses on chemical deposition of “nanometric films” for a variety of leading technologies, has announced a new barrier layer that they say guarantees 100% step coverage. The material is NiB, in contrast to the more traditional TaN and TiN, which, they claim, tend to be used mostly because of their compatibility with standard chemical and plasma vapor deposition (CVD and PVD) processes.
They claim that the NiB has barrier properties similar to TiN and copper, while having diffusion characteristics similar to Ta and TaN. But it also allows the subsequent copper to be filled without requiring a seed layer. The sum total of these benefits is said to save a number of cleaning and other miscellaneous process steps that are currently required, reducing cost.
They call their general process “electrografting”: they deposit a thin layer onto a non-conductive substrate using a water-based process that has molecules from liquid organic precursors of the film layer bonding to the electrons in the substrate. These precursors act as seeds for the rest of the layer.
More info in their release…