Heater Stack In A Micro-Fluid Ejection Device And Method For Forming Floating Electrical Heater Element In The Heater Stack

A method for forming a floating heater element includes processing a silicon substrate to form a heater stack having the heater element on the substrate with peripheral edge portions, processing the heater stack by depositing and patterning a layer of photoresist or hard mask thereon to substantially mask the heater stack and form a trench through the photoresist or hard mask exposing a surface area of the substrate extending along the peripheral edge portions of the heater element, and processing the masked heater stack and exposed surface area of the substrate by sequentially removing the photoresist and portions of the substrate at the exposed surface area and that underlie the heater element so as to create a well in the substrate undercutting the heater element and open along the peripheral edge portions thereof, the well being capable of filling with a fluid so as to produce the floating heater element.