A semiconductor substrate for a micro-fluid ejection head. The substrate includes a plurality of fluid ejection actuators disposed on the substrate. Each of the fluid ejection actuators includes a thin heater stack comprising a thin film heater and one or more protective layers adjacent the heater. The thin film heater is made of a tantalum-aluminum-nitride thin film material having a nano-crystalline structure consisting essentially of AlN, TaN, and TaAl alloys, and has a sheet resistance ranging from about 30 to about 100 ohms per square. The thin film material contains from about 30 to about 70 atomic % tantalum, from about 10 to about 40 atomic % aluminum and from about 5 to about 30 atomic % nitrogen.