Fluid ejector having an anisotropic surface chamber etch

1. A method of forming a fluid ejector comprising:

providing a substrate having a surface;

depositing a first material layer on the surface of the substrate, the first material layer being differentially etchable with respect to the substrate;

defining a fluid chamber boundary region by removing a portion of the first material layer thereby forming a patterned first material layer that includes a region exposing the surface of the substrate;

after forming the patterned first material layer, depositing a sacrificial material layer over the patterned first material layer;

further defining the fluid chamber boundary location by removing a portion of the sacrificial material layer deposited over the patterned first material layer thereby forming a patterned sacrificial material layer that includes a region of sacrificial material that is in contact with the surface of the substrate;

depositing at least one additional material layer over the patterned sacrificial material layer;

after depositing the at least one additional material layer, etching a hole through the at least one additional material layer, said hole terminating at the region of the sacrificial material layer that is in contact with the surface of the substrate within the fluid chamber boundary location;

after etching the hole, removing the sacrificial material layer in the region of the sacrificial material layer that is in contact with the surface of the substrate within the fluid chamber boundary location by introducing a first etchant through the hole;

forming the fluid chamber by introducing a second etchant through the hole to etch substrate material within the fluid chamber boundary location that was exposed after removing the sacrificial material layer; and

forming a source of fluid impedance.

2. The method according to claim 1 , the surface being a first surface, wherein forming the source of fluid impedance comprises:

forming a pit in the first surface of the substrate, the substrate having a second surface opposite the first surface; and

filling the pit with a material which will form a protrusion extending from the first material layer toward the second surface of the substrate,, the protrusion remaining as a region of constriction in a fluid passageway after the fluid chamber is formed.

3. The method according to claim 2 , wherein forming the pit in the first surface of the substrate comprises forming the pit in the first surface of the substrate within the fluid chamber boundary location.

4. The method according to claim 2 , wherein forming the pit in the first surface of the substrate comprises etching the pit in the first surface of the substrate.

5. The method according to claim 4 , wherein etching the pit includes etching the pit using an anisotropic etching process.

6. The method according to claim 4 , wherein etching the pit includes etching the pit using an orientation dependent etching process to provide a pit having a plurality of sloping walls.

7. The method according to claim 4 , wherein etching the pit includes etching the pit using an isotropic etching process.

8. The method according to claim 1 , wherein forming the fluid chamber includes using an orientation dependent etching process to provide a fluid chamber having a plurality of sloping walls.

9. The method according to claim 1 , the hole being a first hole, wherein forming the source of fluid impedance comprises:

depositing an opaque material layer over the at least one additional material layer prior to forming the first hole extending from the at least one additional material layer to the sacrificial material layer, the first hole also extending through the opaque material layer;

forming a second hole extending from the opaque material layer to the sacrificial material layer;

depositing a photopatternable polymer material over the at least one additional material layer such that the polymer material fills the fluid chamber, the first hole, and the second hole;

providing a mask over the first hole;

photoexposing at least some of the photopatternable material;

removing that portion of the photopatternable material which remains unexposed; and

forming a post extending through the second hole from the at least one additional material layer to a wall of the fluid chamber by curing the photopatternable polymer material.

10. The method according to claim 9 , wherein depositing the photopatternable polymer material over the at least one additional material layer comprises depositing an epoxy.

11. The method according to claim 10 , wherein depositing the epoxy includes depositing an SU-8 epoxy.

12. The method according to claim 9 , wherein curing the photopatternable polymer material anchors the post to the wall of the fluid chamber.

13. The method according to claim 9 , wherein forming a second hole extending from the opaque material layer to the sacrificial material layer includes forming a plurality of second holes thereby forming a plurality of posts.

14. The method according to claim 1 , wherein the first etchant is the same as the second etchant.

15. The method according to claim l, wherein the substrate is a silicon substrate.

16. The method according to claim 1 , wherein the sacrificial material layer includes a polycrystalline silicon material.

17. The method according to claim 1 , further comprising:

etching a fluid delivery channel in the substrate using an etchant, the fluid delivery channel connecting with the fluid chamber such that the source of fluid impedance is disposed between the fluid delivery channel and the hole.