In-line XPS metrology for area selective deposition processes on patterned structures

Selective area atomic layer deposition (ALD) processes are gaining more traction due to a high demand to improve edge placement accuracy and atomic level control. These selective deposition processes allow for a bottom-up approach without lithographic or subtractive methods and can address significant challenges posed by scaling logic technology beyond 3 nm nodes. A class of materials called self-assembled monolayers (SAM) may inhibit ALD growth and are most widely studied for area selective deposition (ASD) [1,2]. SAM chemistries can be tailored to selectively adsorb only on a certain material and not others. Integrating SAM processes in back-end-of-line (BEOL) manufacturing have been shown to enhance electrical performance through barrier less vias [3]. It is vital to monitor these deposition processes inline to ensure area selective growth occurs only in intended regions [4,5]. Additionally, the complexity increases because the intended ASD growth is only a few atomic layers and typically the same material is present elsewhere in the BEOL stack. A non-invasive method is required to accurately characterize SAM material, monitor ALD on desired surfaces and inhibition otherwise. In this study, advanced XPS algorithms were successfully developed to monitor SAM as well as TaN ASD on patterned metrology targets. Gas phase SAMs were selectively adsorbed on BEOL Cu wires with intentional line and space design variations. Subsequently, ALD TaN was grown on different surface conditions to evaluate the inhibiting layer as a selective barrier. XPS spectra and EDX scans indicate good TaN selectivity especially when SAM is not exposed to air and deposited on a pre-cleaned Cu surface.