Inkjet printhead having bilayered nozzle plate comprised of two different ceramic materials

1. An inkjet printhead comprising a plurality of nozzle chambers disposed on a substrate and a bi-layered nozzle plate having a plurality of nozzle apertures defined therein, said bi-layered nozzle plate being comprised of:

a lower first nozzle plate comprised of a first material; and

an upper second nozzle plate disposed on said first nozzle plate, said second nozzle plate being comprised of a second material,

wherein:

said first and second materials are different from each other and are each independently selected from the group consisting of: silicon nitride, silicon oxide and silicon oxynitride;

each nozzle chamber comprises a roof spaced apart from said substrate;

each roof is defined by part of said bi-layered nozzle plate;

each nozzle chamber comprises sidewalls extending between said roof and said substrate; and

said first nozzle plate and said sidewalls are comprised of the same material.

2. The inkjet printhead of claim 1 , wherein said first nozzle plate has a plurality of cavities filled with a filler, such that an upper surface of said first nozzle plate and an upper surface of said filler together define a contiguous planar surface on which said second nozzle plate is disposed.

3. The inkjet printhead of claim 2 , wherein said filler is photoresist.

4. The inkjet printhead of claim 1 , wherein one of said nozzle apertures is defined in each roof.

5. The inkjet printhead of claim 4 , wherein each nozzle chamber contains an actuator for ejection of ink through the nozzle aperture.

6. The inkjet printhead of claim 1 , wherein said second nozzle plate has a planar upper surface.

7. The inkjet printhead of claim 1 , wherein said second nozzle plate defines an exterior surface of said printhead.