From PVD to CVD to ALD for interconnects and related applications

As interconnect features migrate towards sub-100 nm structures, BEOL thin film technologies are forced to change. PVD, followed by collimated and I-PVD, is limited by directionality as well as bias-sputter-induced bevel formation. CVD fixes some problems but is challenging for high purity, ultra-thin high aspect ratio films. Atomic Layer Deposition (ALD) replaces both of these technologies in the sub-100 nm BEOL (but not until that point), with the promise of high purity, conformal, low temperature deposition controlled at the atomic scale. ALD initiation steps are critical and substrate-material dependant. The Ti (TiN) and Ta (TaN) ALD systems have been explored at 25 C and 150 C for a variety of interconnect materials and the results suggest some substrate interactions which may enhance the usage of ALD.