Method for forming a microelectromechanical fluid ejection device
View Patent ↗A microelectromechanical fluid ejection device is formed upon a wafer upon which an interconnect layer is disposed. The fluid ejection device includes a number of fluid passageways that are produced by firstly forming a bore through the interconnect layer, from the interconnect layer side, to a depth that is greater than the interface. A second bore is back-etched through the underside of the wafer. The first and second bores meet to form the fluid passageway. Fabricating the ejection device in accordance with the disclosed method avoids etchant traveling along the interface and potentially damaging CMOS circuits located at the interface.
1. A method for forming a microelectromechanical fluid ejection device from a wafer in combination with a first layer covering a first surface of the wafer to form an interface therebetween, the method including the steps of:
forming a first bore into a surface of the first layer opposing the interface to a depth beyond the interface;
forming a second bore into a second surface of the wafer opposing the interface to a depth less than the interface; the first bore and the second bore meeting to form a fluid passageway; and
forming a first plurality of spaced bores identical to, and simultaneous with, the first bore and forming a second plurality of correspondingly spaced bores identical to, and simultaneous with, the second bore in order to simultaneously produce a plurality of fluid passageways.
2. A method according to claim 1 , wherein the second bore is formed after the first bore has been formed.
3. A method according to claim 1 , wherein the first bore is formed after the second bore has been formed.
4. A method according to claim 1 , wherein the wafer comprises a wafer of silicon.
5. A method according to claim 4 , wherein the first layer comprises an interconnect layer.
6. A method according to claim 1 , wherein the step of forming the first bore includes etching the first layer.
7. A method according to claim 1 , wherein the step of forming the second bore includes etching the wafer.
8. A method according to claim 1 , wherein the width of the inlet hole is between 8 microns and 24 microns.
9. A method according to claim 8 , wherein the width of the inlet hole is between 10 microns and 28 microns.