WAFER PLATING INNOVATIONS
The photo above is the Beaker-on-a-Stick™ laboratory wafer plating tool. The chemistry is poured into the vessel and it is raised to the proper anode cathode separation distance. Only 500 mls. of plating solution is needed to process a 100mm wafer. A programmable stepper motor actuates the anode to provide agitation.
Cu, Ni, Au, Pt, Pd, In, Sn, Ag, Co, Rh, magnetic alloys of Ni, Fe & Co, Solder alloys of PbSn, and lead free solder alloys of AuSn & SnAg are processes currently available.
Intra-wafer uniformity of 5% of deposit thickness has been demonstrated on 20 um thick gold bumps plated on 125mm diameter wafers. Uniformity of 6% has been achieved on 3um thick copper plated on 200mm wafers.
Several sources of process drift have been eliminated:
Process drift due to build-up of plated material on the contact locations has been eliminated by using contacts that are sealed off from the plating solution. Sealed contacts are essential when plating extremely small exposed surface areas on the wafer. This is because any build up of plated material on the contacts can be significant enough to change the actual surface area being plated. Sealed contacts are also required when plating very thick films because they prevent welding of the wafer to the contact point.
Mass transport (agitation) related process drift has been virtually eliminated due to the multi-directional mechanical agitation method being used. There are no nozzles to clog or wear out. There are no sliding bushings to wear out either.
Chemically related process drift has been virtually eliminated due to the plating machine’s single shot process platform.
Chemistry is used once for each wafer and then recycled and re-qualified before being used again. Therefore, every wafer in the batch is processed with identical chemistry.
Process drift due to thieving ring build up has been eliminated due to the di-electrically enclosed electrode design. This design contains electric fringe fields thereby eliminating the need for thieving rings.