Fluid ejection device
View Patent ↗The present invention includes as one embodiment a method for fabricating a portion of an ink-jet printhead made of a silicon substrate, the method including selectively etching active region contact vias of a field effect transistor that has a conducting channel that is insulated from a gate terminal by a layer of oxide along with separate substrate contact vias using a single mask and forming the substrate contact vias simultaneously with the active region contact vias during the selective etching.
1. A method for fabricating a fluid ejection device, comprising:
forming a device isolation layer on a substrate;
forming an insulating layer directly on the device isolation layer in a substrate contact area;
forming a polysilicon layer under the insulating layer near a source and drain, wherein the polysilicon layer is not formed between the insulating layer and the substrate at the substrate contact area;
forming at least one substrate contact in the substrate contact area that electrically grounds the substrate; and extending at least one substrate contact through the insulating layer and the device isolation layer to the substrate.
2. The method of claim 1 , wherein at least one substrate contact includes a low conductivity layer contacting at least one of the substrate, device isolation layer and insulating layer and a high conductivity portion deposited on the low conductivity layer.
3. The method of claim 2 , wherein the low conductivity layer contacting the substrate is tantalum-aluminum, and wherein the high conductivity layer is aluminum-copper.
4. The method of claim 2 , wherein the device isolation layer is a field oxide layer.
5. The method of claim 1 , wherein the insulating layer is phosphosilicate glass (PSG).
6. The method of claim 1 , wherein the insulating layer acts as an under-layer for a heater/firing resistor in the fluid ejection device to expel out of a drop firing chamber ink accumulated from an ink supply.