Method of fabricating printhead integrated circuit with backside electrical connections
View Patent ↗A method of fabricating a printhead integrated circuit configured for backside electrical connections. The method comprises the steps of: (a) providing a wafer comprising a plurality of partially-fabricated nozzle assemblies on a frontside of the wafer and through-silicon connectors extending from the frontside towards a backside of the wafer; (b) depositing a conductive layer on the frontside of said wafer and etching to form an actuator for each nozzle assembly and a frontside contact pad over a head of each through-silicon connector; (c) performing further MEMS processing steps to complete formation of nozzle assemblies ink supply channels through-silicon connectors; and (d) dividing the wafer into individual printhead integrated circuits. Each printhead integrated circuit thus formed is configured for backside-connection to the drive circuitry via the through-silicon connectors the contact pads.
1. A method of fabricating a printhead integrated circuit configured for backside electrical connections, said method comprising the steps of:
providing a wafer comprising a plurality of partially-fabricated nozzle assemblies on a frontside of the wafer and one or more through-silicon connectors extending from said frontside towards a backside of said wafer;
depositing a conductive layer on said frontside of said wafer and etching said conductive layer so as to form, concomitantly, an actuator for each nozzle assembly and a frontside contact pad over a head of each through-silicon connector, said frontside contact pad connecting said through-silicon connector to drive circuitry in said wafer;
performing further MEMS processing steps to complete formation of said nozzle assemblies, ink supply channels for said nozzle assemblies and said through-silicon connectors; and
dividing said wafer into a plurality of individual printhead integrated circuits, each printhead integrated circuit being configured for backside-connection to said drive circuitry via said through-silicon connectors and said contact pads.
2. The method of claim 1 , wherein said conductive material is selected from the group consisting of: titanium nitride, titanium aluminium nitride, titanium, aluminium, and vanadium-aluminium alloy.
3. The method of claim 1 , wherein said actuator is selected from the group consisting of: a thermal bubble-forming actuator and a thermal bend actuator.
4. The method of claim 1 , wherein said further MEMS processing steps comprise depositing a material onto said contact pad so as to seal or encapsulate said contact pad.
5. The method of claim 1 , wherein a CMOS layer comprises said drive circuitry, and said nozzle assemblies are disposed in a MEMS layer formed on said CMOS layer.
6. The method of claim 1 , wherein said further MEMS processing steps comprise oxidatively removing sacrificial material.
7. The method of claim 1 , wherein said further MEMS processing steps comprise coating a frontside face with a hydrophobic polymer layer.
8. The method of claim 7 , wherein said hydrophobic polymer layer is comprised of PDMS.
9. The method of claim 1 , wherein said further MEMS processing steps comprise etching a backside of said wafer so as to define said ink supply channels and a backside recessed portion for each printhead integrated circuit.
10. The method of claim 9 , wherein said ink supply channels and said backside recessed portion have a same depth.
11. The method of claim 9 , wherein said backside etching exposes a foot of each through-silicon connector in said backside recessed portion, each foot comprising an integrated circuit contact.
12. The method of claim 9 , wherein said through-silicon connectors are positioned along a longitudinal edge region of each printhead integrated circuit, and said backside recessed portion extends along said longitudinal edge region.
13. The method claim 11 , wherein said integrated circuit contacts are positioned for connection to corresponding contacts of a TAB film.
14. The method of claim 1 , wherein one or more conductor posts extend linearly between said contact pad and said CMOS layer and/or between said actuator and said CMOS layer.
15. The method of claim 14 , wherein said conductor posts are formed prior to deposition of said conductive layer.
16. The method of claim 14 , wherein said conductor posts are formed concomitantly with said through-silicon connectors.
17. The method of claim 16 , wherein said conductor posts and said through-silicon connectors are formed by deposition of a conductive material into predefined vias.
18. The method of claim 17 , wherein said conductive material is deposited by an electroless plating process.
19. The method of claim 17 , wherein each of said predefined vias has a diameter proportionate with a depth such that said all said vias are filled evenly by said deposition.
20. The method of claim 17 , wherein said conductive material is copper.