Sputter deposition of Mo-based multicomponent thin films from rotatable targets: Experiment and simulation

Abstract

Sputter deposited Mo-based thin films play a key role in the manufacturing of modern flat panel displays and microelectronic components. They are widely used as source/drain electrodes, as gate material or as metallization layer for signal and data bus lines. Within this work, the sputter performance of a Mo0.70Al0.20Ti0.10 rotatable target was investigated to correlate processing conditions to thin film growth and chemistry. An industrial-scale in-line magnetron sputter system was used to deposit a series of thin films on silicon wafers at Ar pressures from 0.25 to 0.70 Pa. The center of the substrate carrier was kept at a constant offset from the target middle axis. Film thickness and chemical composition were evaluated for substrates located at different lateral positions. The morphologies and cross-sections of the films were examined by scanning electron microscopy and focused ion beam milling, revealing dense fibrous structures opposite the target and fine isolated columnar grain structures at extended positions from the center of the target. Energy dispersive X-ray spectroscopy showed a depletion of Al in favor of Mo enrichment opposite the target and a reverse trend at extended distances. The plasma used for sputtering was modelled after realistic target geometries using the S3M computer code and served as input for subsequent SRIM scatter simulations. It is demonstrated that the combination of experiments and simulations allows to distinguish a high- and low-flux regime, leading to different film structures and chemical compositions.