Amorphization of Ta–Al films using magnetron sputtering

Amorphous films of alloys generally have different properties from the crystalline ones in the microstructure, resistivity and morphology. In this paper, we study the Ta/Al composition ratio effect on the formation of amorphous Ta–Al alloy films, which are used as heating materials in inkjet printhead or micro-thermal actuator. Three kinds of Ta/Al atomic composition ratios of about 2/1, 1/1 and 1/2 are prepared by different powers of Ta and Al targets in a magnetron sputtering system. The microstructure of Ta–Al film becomes amorphous at medium Al composition ratio of about 50%, while they are polycrystalline at low Al composition ratio of about 33% and at high Al composition ratio of about 67%. The amorphous TaAl film also has better properties than the others. It has the highest resistivity of 163.73 μΩ cm than the others of 125.46 and 120.71 μΩ cm, respectively. It also has the smoothest morphology with average roughness of 0.12 nm than the others' roughness of 0.39 and 7.2 nm, respectively. The smooth morphology of TaAl film with high resistivity is good for the application of micro-thermal actuator as the heating element.