Planar heater stack and method for making planar heater stack with cavity within planar heater substrata above substrate

A planar heater stack for a micro-fluid ejection device, comprising:

• first strata having a substantially planar configuration supporting and forming a fluid heater element responsive to repetitive electrical activation and deactivation to produce repetitive cycles of ejection of a fluid from an ejection chamber above said fluid heater element;
• and
• second strata having a substantially planar configuration coating said fluid heater element of said first strata and being contiguous with said ejection chamber;
• wherein said first strata includes
• a substrate having a top surface,
• a heater substrata including
• a lower conductive layer disposed above said top surface of said substrate and defining a pair of conductive terminal leads spaced apart from one another and having end surfaces facing toward one another so as to substantially define a cavity there between such that said substrate underlies said cavity, and
• an upper resistive layer disposed above said lower conductive layer and overlying said conductive terminal leads and defining said fluid heater element spanning between said conductive terminal leads and overlying said cavity there between such that said heater substrata encompasses said cavity on three sides above said substrate.