AlN capping layer inserted between Cu and SiCN dielectric barrier layer for enhancing reliability of 28 nm technological node and beyond

Abstract

The improvement of the interface adhesion between Cu and silicon carbonitride (SiCN) dielectric barrier layer is required in the back end of the line for 28 nm technological node and beyond. The main purpose of this paper was to investigate the reliability of breakdown voltage (VBD) and electromigration (EM) improved by inserting the AlN capping layer enhancing the above mentioned interfacial adhesion. The AlN capping layer was deposited by the ALD process using trimethylaluminum and ammonia precursors. The AlN capping layer was characterized by a cross-sectional transmission electron microscopy (XTEM) and energy dispersive X-ray spectrum (EDX) for the thickness and interfacial composition, electrical test for resistance-capacitance examination, reliability test for VBD and EM lifetime. XTEM observation indicated that the thickness of the AlN capping layer was about 8.5 nm, and the EDX examination indicated the Al and N elements of the AlN capping layer were distributed in the interface between Cu and SiCN dielectric barrier layer. Reliability test indicated that the VBD and EM performances were improved obviously by inserting the AlN capping layer for enhancing the interfacial adhesion between Cu and SiCN dielectric barrier layer.