Area-Selective Deposition by a Combination of Organic Film Passivation and Atomic Layer Deposition

Abstract

Area-Selective Deposition (ASD) has the potential to enable self-aligned patterning schemes, which are implemented in the effort of keeping pace with the more and more challenging downscaling of the integrated circuit components. ASD can be achieved by exploiting surface-sensitive deposition techniques, such as Atomic Layer Deposition (ALD). However, the inherent selectivity of ALD is confined to very few ALD cycles (very thin films). Self-Assembled Monolayers (SAMs) are evaluated as a metal passivation coating to extend the ASD inhibition window. We present a successful strategy to achieve the selective deposition of Al oxide on Cu/SiO2 patterned substrate down to 50 nm half-pitch (HP) lines. We exploit the selective chemisorption of 1-octadecylthiol (ODT) on Cu to confine Al2O3 deposition on Si oxide. A study of ODT deposition on Cu allows to determine the best deposition conditions, which enable the demonstration of ASD of 6 nm Al2O3 film at relevant nano-scale dimensions. Selectivity toward Cu is demonstrated through the absence of Al signal in energy dispersive X-ray spectroscopy.

Nanomechanical Characterization of Organic Surface Passivation Films on 50 nm Patterns during Area-Selective Deposition

“…As all these measurements are combined together, a clear assessment of the ASD experiment results is possible at critical dimensions as low as 15 nm. 17 Since self-assembled monolayers (SAMs) are the most extensively employed passivation method for ASD purposes, especially at relevant nanoscale dimensions, 16,17,21,28,29 the proposed characterization method is tested on a SAM-enabled ASD process (Figure 1). In SAM-based ASD processes, the monolayer is selectively grafted to the areas that must be deactivated prior to the ALD.…”

“…Indeed, few characterization techniques are available to assess the selectivity of a given process as a substrate’s features approach nanometric dimensions. At such a scale, ASD results are predominantly evaluated and studied by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and AFM. ,,,,,,,,− In particular, SEM offers a relatively large field image of the patterned substrates, whereas TEM provides images of the ASD film with a resolution of a few nanometers. In addition, EDX measurements taken in conjunction with SEM or TEM enable chemical identification of the investigated samples.…”

“…SAM precursors typically consist of a reactive head group that enables the selective chemisorption of the molecules onto the intended surface, a relatively long alkyl chain that provides the driving force to the self-assembly process, and an end group that defines the organic film’s surface properties. , For ASD purposes, hydrophobic CH 3 - and CF 3 -terminated SAM are preferred since ALD precursor physisorption is hindered on such functional groups. For example, thiol-derived CH 3 -terminated SAMs have been largely studied to achieve ASD on SiO 2 versus Cu for nanoelectronics applications. ,,,,,− …”

Dielectric-on-Dielectric Achieved on SiO2 in Preference to W by Water-free Chemical Vapor Depositions with Aniline Passivation

“…Heshemi et al and other researchers demonstrated selective passivation on metals and resultant selective DOD deposition by using octadecylphosphonic acid or thiolate as the passivant. − However, these passivants do not work well with strong oxidizers and are only compatible with low-temperature (<150 °C) ALD, which normally uses water as the co-reactant . This low-temperature water-based ALD might compromise the performance of back-end-of-line (BEOL) circuits by inducing resistor capacitor time delay since a small amount of adsorbed water could lead to a significant increase in the k value of low k dielectric materials. , …”

Understanding Selectivity Loss Mechanisms in Selective Material Deposition by Area Deactivation on 10 nm Cu/SiO2 Patterns

“…This confined material growth is most commonly accomplished by exploiting well-distinguished local surface chemistries in conjunction with deposition techniques whose growth rate can be affected by the substrate’s chemical specificity. ,− Therefore, one of the most successful material deposition techniques for ASD applications is atomic layer deposition (ALD), whose well-known surface-dependent nucleation rate relies on the solid–gas self-limiting half-cycle surface reactions. ,,, Indeed, on a suitable patterned substrate, it is observed that ALD starts instantly on the GA, whereas a nucleation delay is observed on the NGA, potentially achieving ASD. To enhance the possible intrinsic selectivity offered by the ALD process, a selective surface blocking layer is used to prevent nucleation on the NGA. ,,− In these ASD strategies, commonly referred to as area-deactivation schemes, material growth blocking functionalities are either selectively grafted ,,,− or formed by gas/plasma and wet surface treatments. ,,, …”