Bipolar High Power Impulse Magnetron Sputtering for energetic ion bombardment during TiN thin film growth without the use of a substrate bias

TL;DR

This study demonstrates that applying a positive voltage pulse after the HiPIMS pulse in bipolar sputtering allows for control of ion energy, leading to denser TiN films with higher hardness and stress without substrate bias.

Contribution

It introduces a method to tune ion energy in bipolar HiPIMS using a reverse voltage pulse, enhancing film density and mechanical properties.

Findings

Ion energy can be controlled by reverse voltage pulse.

Bipolar HiPIMS produces denser, harder TiN films.

Film hardness increased from 23.9 to 34 GPa.

Abstract

The effect of applying a positive voltage pulse (Urev = 10 - 150 V) directly after the negative high power impulse magnetron sputtering (HiPIMS) pulse (bipolar HiPIMS) is investigated for the reactive sputter deposition of TiN thin films. Energy-resolved mass spectroscopy analyses are performed to gain insight in the effect on the ion energy distribution function of the various ions. It is demonstrated that the energy of a large fraction of the ions can be tuned by a reverse target potential and gain energy corresponding to the applied Urev. Microscopy observations and x-ray reflectometry reveal densification of the films which results in an increase in the film hardness from 23.9 to 34 GPa as well as an increase in compressive film stress from 2.1 GPa to 4.7 GPa when comparing conventional HiPIMS with bipolar HiPIMS (Urev = 150 V).