Effect of substrate bias on Ta-Ni diffusion barrier film for copper metallization

• Main Author: Yantara, Natalia
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/15630
• Institution: Nanyang Technological University

The effects of substrate bias on the properties of Ta-Ni film as a diffusion barrier for copper metallization were investigated. Ta-Ni films with Ta:Ni ratio 2.32-2.75 were deposited on the p-type silicon (100) wafers using magnetron co-sputtering with various substrate bias ranging from 0 - 100 watt. Alpha-Step 500 Profiler, four point probe method, X-Ray Diffraction (XRD) with a Rigaku diffractometer, and Energy Dispersive X-ray (EDX) were used to characterize the film properties. Vacuum Thermal Annealing was employed to analyze the thermal stability of the film. The result revealed that higher substrate bias induced reduction on the deposition rate and resistivity of the film as well as small alteration on the film content and thermal stability of the film. Modification on the properties of the film with substrate bias is related with the oxygen content and density of the film itself. Additional 100 watt substrate bias on the Ta-Ni film during deposition showed beneficial effect on the film properties. The film was able to maintain its microstructure up to 700°C annealing temperature for 30 minutes. Thermal stability of the film decreased with incorporation of copper layer on top because copper atoms diffusion on the barrier layer might induce dissociation of the film and formation of silicides. Further copper atoms diffusion is accommodated by the grain boundaries of the silicides and produces copper silicides that are responsible for the high resistivity of the film stacks.