Excimer laser micromachining of TiN films from chromium and copper sacrificial layers

Abstract

This paper presents results on the laser micromachining of TiN films. Machining performance was evaluated in terms of patterning quality and the ability to remove TiN with minimal interference with an underlying sacrificial layer. TiN was arc-deposited onto (100) silicon substrate with chromium (Cr) and copper (Cu) sacrificial layers. Films were also deposited onto bare silicon substrates under the same conditions. These films were analysed for their composition and structure using Rutherford backscattering spectroscopy and x-ray diffraction techniques. Laser micromachining was performed using a KrF excimer laser at 248 nm. The effect of fluence and number of shots on the machined features has been investigated in detail. The patterned features were examined using optical, confocal and scanning electron microscopes. The characteristics observed were analysed and compared in all three sets of samples. The results showed selective removal of TiN films from Cr and Cu sacrificial layers under different conditions. The machining of TiN from (100) silicon showed relatively poor definition of patterned features. The analysis of these results indicated that laser machining of TiN from Cr and Cu layers is best explained using the explosion mechanism of removal.