The high fluxes of ionized material available in HiPIMS have been found to allow for control of the phase formation in both elemental and compound films.One example is the control of the phase composition in Ta films. In this case, tailoring of the phase formation is achieved by controlling the magnitude of the internal stresses.
This process is particularly efficient in HiPIMS discharges owing to the degree of ionization of the Ta vapor of up to 70%.Ta forms both a low resistivity body-
centered cubic crystal structure (also known as the a phase) at elevated temperatures and a metastable high resistivity tetragonal phase (b-Ta) at room temperatures.
The abundance of Ta+ ions in the deposition flux during the HiPIMS deposition of Ta films implies a more efficient momentum transfer to the growing surface.
This is in contrast to the growth by DCMS,where the majority of the ions in the deposition flux consists of the much lighter Ar+ions. HiPIMS thus provides tools for better influencing the internal stresses of the growing Ta films and accordingly the possibility to deposit a-Ta films at room temperature (Fig. 7).
12