Novel strategies for surface micromachining TiN thin films deposited by filtered arc

TiN is used commercially as a wear resistant coating on cutting tools and as a diffusion barrier in microelectronics. TiN has gained increased interest as a material for MEMS, however there has been very little work carried out in the area of patterning and releasing TiN for use as a structural MEMS material. This thesis presents an investigation into the patterning and release of filtered arc deposited TiN thin films using surface micromachining techniques. Two novel strategies are presented for patterning TiN thin films and are achieved using excimer laser micromachining and photolithographic wet-etching. TiN was deposited onto single crystal Si and Cr and Cu sacrificial layers on Si. The use of Cr as a sacrificial layer was found to facilitate the best quality patterning of the TiN and hence the majority of the work involved using Cr sacrificial layers. TiN was deposited using partial filtration and full filtration and differences in the ability to selectively laser pattern the TiN from the Cr sacrificial layer are presented. Various analytical techniques were employed to investigate the origin of the difference in laser patterning the TiN thin films. The establishment of TiN and Cr as a novel material combination for surface micromachined MEMS was extended by etching the Cr sacrificial layer to facilitate the release of TiN stress-measurement structures. The major finding of this thesis is that filtered arc deposited TiN thin film on Cr can be used as a material combination to surface micromachine freestanding TiN structures as high quality patterning and etch selectivity can be achieved using both excimer laser micromachining and photolithographic wet-etching.