Patent ID: 8070265

Claim:
A heater stack in a micro-fluid ejection device, comprising: a silicon substrate; a heater substrata of resistive and conductive layers on a front side of said silicon substrate supporting and forming an electrical fluid heater element having peripheral edge portions defining at least two opposite sides and a bight with a distal end opposite a proximate end, the resistive and conductive layers having a substantially U-shaped configuration wherein the conductive layers define a pair of laterally spaced apart legs at the proximate end of the fluid heater element to energize the fluid heater element; an anisotropically etched well formed in said silicon substrate undercutting said electrical fluid heater element and open along said peripheral edge portions at the at least two opposite sides and the distal end of said electrical fluid heater element and between the pair of laterally spaced apart legs of the conductive layers, said well capable of filling with a fluid so as to produce, in effect, a floating electrical heater element on said silicon substrate of said electrical heater stack; and a via form through said silicon substrate to said well therein underneath said electrical heater element having a sidewall extending from a back side of said silicon substrate toward said front side thereof and to said well underneath said heater element for centrally supplying the fluid into a bottom of said well spaced beneath said heater element.