US Patent 7588321 Inkjet printhead with low loss CMOS connections to heaters

An ink jet printhead with an array of nozzles 3. A chamber 7 and a heater 14 correspond to each nozzle respectively. The heater has a heater element 10 extending between a pair of electrodes 15. The heater elemen 10 is suspended in the chamber 7 by the electrodes 15 to heat printing fluid and generate a vapour bubble to cause a drop of the printing fluid to eject through the nozzle 3. Integrated circuit metalization layers corresponding to each of the nozzles supply electrical energy to the heater 14. The heater 14 and the integrated circuit metalization layers 23 are substantially planar and at least partially overlapping, the metallization layers electrically connected to the heater electrodes 15 by vias, the cross sectional area of all the vias being greater than 50% of the surface area of one side of the heater 14. A relatively large number of vias lowers the electrical resistance between the electrodes and the CMOS metalization layers. Lower resistance reduces the power losses and improves the operating efficiency of the printhead.