JVD flow and pressure conditions can be easily modified in the nozzle and jet to promote high rate nucleation, growth, and deposition of nanoclusters. The key advantage is that cluster deposition is far more directional than atom deposition. Once the heavier nanocluster has been accelerated, its high inertia constrains its trajectory to be almost exactly perpendicular to the wafer. In consequence, there is little shadowing by resist walls, and since sidewall deposition is also reduced, there is reduced breadloafing. For small windows in the photoresist, where the aspect ratio is high, hole filling by nanoclusters is far more efficient than filling with atoms. We have been putting this key nanocluster capability of JVD to increasing use in making small solder bumps in dense arrays. For example, with nanocluster AuSn we have deposited arrays of solder bumps 4 microns in diameter with a pitch of 8 microns.
For more information on our clean and green nanoclusters, please click here for the 2011 EPA SBIR success story in "Science Matters" newsletter: www.epa.gov/sites/production/files/2015-06/documents/jetprocess.pdf