Materials characterization of WN xC y, WN x and WC x films for advanced barriers

Abstract

A ternary WN x C y system was deposited in a thermal ALD (atomic layer deposition) reactor from ASM at 300 °C in a process sequence using tungsten hexafluoride (WF 6), triethyl borane (TEB) and ammonia (NH 3) as precursors. The WC x layers were deposited by a novel ALD process at a process temperature of 250 °C. The WN x layers were deposited at 375 °C using bis( tert-butylimido)-bis-(dimethylamido)tungsten ( t BuN) 2(Me 2N) 2W (imido–amido) and NH 3 as precursors. WN x grows faster on plasma enhanced chemical vapor deposition (PECVD) oxide than WC x does on chemical oxide. WN x C y grows better on PECVD oxide than on thermal oxide, which is opposite of what is seen for WN x . In the case of the ternary WN x C y system, the scalability towards thinner layers and galvanic corrosion behavior are disadvantages for the incorporation of the layer into Cu interconnects. ALD WC x based barriers have a low resistivity, but galvanic corrosion in a model slurry solution of 15% peroxide (H 2O 2) is a potential problem. Higher resistivity values are determined for the binary WN x layers. WN x shows a constant composition and density throughout the layer.