Method Of Fabricating A Printhead IC

Abstract

Provided is a method of fabricating a printhead integrated circuit (IC). The method includes the step of depositing metal layers interspersed with interlayer dielectric (ILD) layers onto a silicon wafer substrate. A passivation layer is deposited onto an outermost metal layer and at least a portion of the passivation layer is masked with a photoresist. A pit is etched into the silicon wafer substrate, said pit having a base and sidewalls. Etching is carried out along an edge of the substrate to expose the last metal layer to define bonding pads for operatively connecting a microprocessor. A step of etching portions adjacent the pit to expose the outermost metal layer to define electrode portions. The electrode portions are for supporting a heater element to be suspended in the pit.

1 . A method of fabricating a printhead integrated circuit, said method comprising the steps of:
 depositing a plurality of metal layers interspersed with interlayer dielectric layers onto a silicon wafer substrate;   depositing a passivation layer onto an outermost metal layer;   masking at least a portion of the passivation layer with a photoresist;   etching a pit in the substrate at an unmasked portion of the passivation layer, said pit having a base and sidewalls;   etching along an edge of the substrate to expose the outermost metal layer to define bonding pads for connection to a micro processor; and   etching at least two areas adjacent the pit to expose the outermost metal layer to define electrode portions for supporting a heater element to be suspended in the pit between the electrode portions.   
     
     
         2 . The method of  claim 1 , further comprising the steps of:
 depositing photoresist sacrificial material on a surface of said substrate so as to fill said pit;   removing said sacrificial material from a perimeter region within said pit and from said substrate surface surrounding said pit;   reflowing remaining sacrificial material within said pit such that said remaining sacrificial material contacts said sidewalls;   depositing heater material on said substrate surface and on said reflowed sacrificial material; and   removing said reflowed sacrificial material to form the heater element suspended between the electrodes.   
     
     
         3 . The method of  claim 2 , further comprising the step of depositing a roof material onto the filled pit and etching a printhead nozzle arrangement in the roof material over the pit. 
     
     
         4 . The method of  claim 3 , wherein the heater element forms a thermal actuator for the printhead nozzle arrangement. 
     
     
         5 . The method of  claim 2 , wherein photoresist is removed by exposure through a mask followed by development. 
     
     
         6 . The method of  claim 2 , wherein the reflowing is performed by heating the sacrificial material. 
     
     
         7 . The method of  claim 1 , wherein the sacrificial material is treated to prevent further reflow prior to deposition of the heater material. 
     
     
         8 . The method of  claim 7 , wherein the treatment comprises UV curing.