Substrate preparation method for a MEMS fabrication process
View Patent ↗Provided is a substrate preparation method for a micro-electromechanical system (MEMS) fabrication process. The method includes the step of depositing at least four 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 through the photoresist in the 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. A step of etching is carried out on either side of the pit to expose the outermost metal layer to define electrode portions. The bonding pads are for operatively connecting a microprocessor for controlling a heater element suspended in the pit between the electrode portions.
1. A substrate preparation method for micro-electromechanical system (MEMS) fabrication, said method comprising the steps of:
depositing at least four 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 through the photoresist in the substrate, said pit having a base and sidewalls;
etching along an edge of the substrate to expose the outermost metal layer to define bonding pads; and
etching on either side of the pit to expose the outermost metal layer to define electrode portions, said bonding pads for operatively connecting a microprocessor for controlling a heater element suspended in the pit between the electrode portions.
2. The method of claim 1 , having 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 , having 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.