Patent ID: 7735971

Claim:
An inkjet printhead comprising: a wafer substrate defining a planar support surface; an array of ink chambers adjacent the planar support surface of the wafer substrate, each ink chamber in the array having an elliptical nozzle with an elongate shape and an elongate thermal actuator for ejecting ink through the nozzle, the elongate shape of the nozzle having its long dimension aligned with that of the elongate thermal actuator, the elongate thermal actuator having two sections with higher resistance than the remainder of the thermal actuator and each ink chamber further having a droplet stem anchor positioned between the two sections with higher resistance of the thermal actuator; and, drive circuitry for providing the elongate thermal actuators with electrical pulses for generating a vapour bubble to eject ink through the nozzle, the drive circuitry being complementary metal oxide semiconductor (CMOS) circuitry formed on the planar support surface by a plurality of patterned metal layers interleaved with dielectric layers, the CMOS circuitry having an outer metal layer furthest from the planar support surface which defines a plurality of electrodes arranged in pairs, a trench etched into the drive circuitry extends between the electrodes in each pair; wherein, the elongate thermal actuators each have a heater element extending between two contacts, the contacts each overlaying and directly contacting one of the electrodes respectively such that the heater elements are each powered by one of the pairs of electrodes respectively, the thermal actuator being a unitary planar structure such that the heater element is suspended over the trench extending between the electrodes.