Paper EM-ThM3
Moving Across the Periodic Table: Amorphous Hydrogenated Boron Carbide for Low-k Dielectric Applications

Thursday, October 22, 2015, 8:40 am, Room 211C

A major challenge facing the semiconductor industry is the development of new low-dielectric-constant (low-k) materials for metal interconnects to mitigate the issues surrounding resistance–capacitance (RC) delays as dimensionality is reduced. Such materials include not only bulk inter-/intra-layer dielectrics (ILDs), but also more specialized layers such as Cu diffusion barriers, etch stop layers, and hard masks. Traditional materials for these purposes have been derived from the Si family; however, it is becoming increasingly challenging to tailor these to meet all of the integration requirements, particularly maintaining mechanical and chemical resilience as k is lowered. Toward this end, amorphous hydrogenated boron carbide (a-B_xC:H_y) is an intriguing alternative. Amorphous B_xC:H_y is a unique solid based on six-coordinate icosahedral ‘molecular’ units. As a semi-insulating low-density solid with one of the lowest possible average atomic numbers, Z (H = 1, B = 5, C = 6), a-B_xC:H_y is expected to feature a low dielectric constant, while also inheriting the appealing properties of crystalline BC, which include extreme hardness, as well as thermal and chemical robustness. We describe novel a-B_xC:H_y materials for low-k ILD, diffusion barrier, and etch stop applications with dielectric constant (<3.5), leakage current (<10^–8 A/cm² at 2 MV/cm), and mechanical properties (Young’s modulus >100 GPa) that meet or surpass those of Si-based materials currently being used for these applications. We further explore some of the fundamental similarities and differences between Si- and BC-based classes of materials.