Plasma-Enhanced Atomic Layer Deposition of Boron Carbide for Interconnect Applications

Abstract

As the semiconductor industry endeavors to scale integrated circuit dimensions— decreasing layer thicknesses while increasing the aspect ratio of fillable features—the need for novel interconnect materials with highly specialized properties continues to rise. Meeting the requirements for the numerous types of materials needed, including low-k dielectrics, etch stops, metal diffusion barriers, hardmasks, spacer layers, and other pattern-assist layers, with traditional silicon-based materials is becoming increasingly challenging. As an alternative to silicon, amorphous hydrogenated boron carbide (a BC:H), grown through plasma-enhanced chemical vapor deposition (PECVD), has been demonstrated to possess excellent dielectric properties, combined with very high Young’s modulus, electrical properties rivaling those of SiOC:H variants, very good chemical stability, and unique and useful etch chemistry. However, a problem with PECVD growth that will limit its long-term utility is its inability to scale while maintaining uniform, conformal coatings for very thin films. To combat the issues arising from PECVD grown boron carbide, a plasma enhanced molecular-layer-deposition-based process for the growth of BC films on metal (copper) substrates using solid carborane precursors was proposed. This thesis describes the design and construction of a reactor chamber capable of this hypothesized film growth as well as the characterization of those preliminary depositions. Monolayer carborane growths on copper substrates were demonstrated with characterization including in situ spectroscopic ellipsometry, as well as ex situ contact angle analysis and X-ray photoelectron spectroscopy. The surface of the monolayer was then plasma treated and preliminary multi-layer growths were tested.