CORRELATING THERMAL PROPERTIES OF SPUTTERED TANTALUM AND TANTALUM NITRIDE THIN FILMS OF VARYING N2 CONTENT WITH MECHANICAL, ELECTRICAL AND STRUCTURAL PROPERTIES

Abstract

With rapid growth in the semiconductor industry, the need for optimization of nanofabrication processes is ever increasing. In such processes, TaN films are of great interest as they create effective diffusion barriers against Cu interconnects in integrated circuits. These circuits may be subjected to elevated temperatures during processing and it is important to study the changes in properties of materials involved. Surprisingly, limited data on the constant pressure specific heat capacity (cp) of Ta and TaN thin films exist. This thesis studies the changes in cp from room temperature to 400°C of sputter-deposited Ta and TaN thin films with varied N2 partial pressure. Parallel studies of mechanical, electrical and structural changes are conducted on as-deposited and annealed samples to correlate to changes in cp. The cp of films increases with temperature, as seen in bulk forms of Ta and TaN. Low temperature resistivity measurements are performed to study the effect of lattice vibrations decreasing. The electrical properties of TaN, deposited in greater than 23% N2 content, are found to be insulating. Annealing decreases the resistivity of Ta films which is attributed to defect healing. The hardness and Young’s modulus increase up to 27% N2 content of TaN films. The residual stress in these films range from highly tensile Ta to increasingly compressive TaN with increased N2 content. The TaN film with the lowest inducing stress was 18% N2 with a compressive stress of -5.82 MPa.