Overcoming adhesion limits in tungsten coatings by magnetron sputter ion plating

Abstract

Tungsten thin films are integral to many advanced applications due to their exceptional physical and chemical properties. However, conventional direct current magnetron sputtering (DCMS) techniques face significant limitations in achieving thick, adherent W coatings on different materials such as silicon, primarily due to residual stress leading to delamination at critical thicknesses. To overcome these challenges, this work employs magnetron sputter ion plating for the deposition of tungsten films on low activation steel (F82H) and monocrystalline silicon substrates. The deposition was carried out under varying substrate biases ranging from 0 to −1500 V. Characterization techniques such as grazing incident X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, optical profilometry, hardness measurements and scratch adhesion tests were used to evaluate the properties of the films. The results indicate that increasing the substrate bias enables the deposition of significantly thicker films, achieving up to 2000 nm at −1500 V on silicon compared to approximately 300 nm at 0 V. Additionally, higher biases reduce the residual compressive stress from 4.25 GPa to 1.5 GPa, contributing to improved adhesion. This work shows that the magnetron sputter ion plating deposition approach effectively overcomes the thickness and adhesion limitations associated with conventional DCMS-grown tungsten films.