Photoemission studies on the efficacy of self-assembled monolayers for use in transistor interconnect applications

Authors: Anita Brady-boyd (Dublin City University)
Co-authored by industrial partner: No

Type: Thesis

State: Published (Approved)
Published: November 2018

Open Access Open Access

Abstract: The thesis explores the effectiveness of incorporating amino terminated self-assembled monolayers (SAMs) into several different aspects of the back-end-of-line (BEOL) process for integrated circuit (IC) fabrication . SAMs are essentially two-dimensional nanomolecular assemblies which can display large scale ordering via weak Van der Waals interactions, when deposited on a surface. In this study SAMs are considered for four main applications (i) as a pore sealant for porous dielectrics, (ii) as an adhesion promoter between copper and SiO2, (iii) as a blocker for selective area atomic layer deposition (ALD) and (iv) as a sacrificial layer in the novel electroless deposition (ELD) of cobalt. From a pore sealing perspective, in-situ x-ray photoelectron spectroscopy (XPS) studies have shown that a manganese silicate layer is formed when a thin film of manganese is deposited and annealed on SAM terminated SiO2 and spin-on glass substrates. The presence of a silicate implies that the manganese can diffuse through the SAM and form a chemically stable barrier which could inhibit copper infiltration into the dielectric. In a separate study, XPS analysis of ultra-thin copper films (~0.5nm) deposited on three differently terminated SAMs suggests that amino terminated SAMs offer significant benefits in terms of both the nucleation and adhesion of copper overlayers on dielectric surfaces. A subsequent in-situ XPS study of the effects of atomic oxygen treatments of SAM terminated dielectric substrates displayed that highly controlled stepwise removal of the SAM could be routinely achieved which has significance for the understanding the oxidation cycle in the ALD growth of metal oxides on SAM terminated substrates. Finally, the role of SAMs in cobalt interconnect electroless deposition (ELD) has been characterised by hard x-ray photoelectron spectroscopy (HAXPES) in order to understand the optimized process to fabricate these interconnect structures.

Journal Keywords: Interconnect; Low-k dielectrics; X-ray Photoemission Spectroscopy; Self-Assembly Monolayers

Subject Areas: Physics

Instruments: I09-Surface and Interface Structural Analysis