Metal film protection during printhead fabrication with minimum number of MEMS processing steps

1. A method of fabricating a printhead having a hydrophobic ink ejection face, the method comprising the steps of:

(a) providing a partially-fabricated printhead comprising a plurality of nozzle chambers filled with a first sacrificial material and a nozzle plate having a relatively hydrophilic nozzle surface, said nozzle surface at least partially defining the ink ejection face of the printhead;

(b) depositing a hydrophobic polymeric layer onto the nozzle surface;

(c) depositing a protective metal film onto at least said hydrophobic polymeric layer;

(d) depositing a second sacrificial material onto said metal film;

(e) patterning said sacrificial material to define a plurality of nozzle opening regions;

(f) defining a plurality of nozzle openings through said metal film, said hydrophobic polymeric layer and said nozzle plate;

(g) removing all of said first sacrificial material by subjecting said printhead to an oxidizing plasma, wherein said metal film protects said hydrophobic polymeric layer from said oxidizing plasma; and

(h) removing said protective metal film after removal of said first sacrificial material, thereby providing a printhead having a relatively hydrophobic ink ejection face.

2. The method of claim 1 , wherein said protective metal film is comprised of a metal selected from the group comprising: titanium and aluminium.

3. The method of claim 1 , wherein said protective metal film has a thickness in the range of 10 nm to 1000 nm.

4. The method of claim 1 , wherein step (f) is performed by sequential etching steps.

5. The method of claim 4 , wherein a first metal-etching step is followed immediately by a second etching step for removing polymeric material and nozzle plate material.

6. The method of claim 5 , wherein said second etching step is a dry etch employing a gas chemistry comprising O 2 and a fluorinated etching gas.

7. The method of claim 6 , wherein said fluorinated etching gas is selected from the group comprising: CF 4 and SF 6 .

8. The method of claim 1 , wherein step (h) is performed by wet or dry etching.

9. The method of claim 1 , wherein step (h) is performed by a wet rinse using peroxide or HF.

10. The method of claim 1 , wherein all plasma oxidizing steps are performed prior to removing said protective metal film in step (h).

11. The method of claim 1 , wherein backside MEMS processing steps are performed prior to removing said protective metal film in step (h).

12. The method of claim 11 , wherein said backside MEMS processing steps include defining ink supply channels from a backside of said wafer, said backside being an opposite face to said ink ejection face.

13. The method of claim 1 , wherein said first sacrificial material is a photoresist scaffold which is removed using an oxygen ashing plasma.

14. The method of claim 1 , wherein a roof of each nozzle chamber is defined at least partially by said nozzle plate.

15. The method of claim 14 , wherein said nozzle plate is spaced apart from a substrate, such that sidewalls of each nozzle chamber extend between said nozzle plate and said substrate.

16. The method of claim 1 , wherein said hydrophobic polymeric layer is comprised of a polymeric material selected from the group consisting of: polymerized siloxanes.

17. The method of claim 16 , wherein said polymeric material is polydimethylsiloxane (PDMS).

18. The method of claim 1 , wherein said nozzle plate is comprised of a material selected from the group consisting of: silicon nitride; silicon oxide and silicon oxynitride.

19. The method of claim 1 , wherein at least one of said first and second sacrificial materials is photoresist.