Nucleation and Conformality of Iridium and Iridium Oxide Thin Films Grown by Atomic Layer Deposition

Abstract

Nucleation and conformality are important issues, when depositing thin films for demanding applications. In this study, iridium and iridium dioxide (IrO) films were deposited by atomic layer deposition (ALD), using five different processes. Different reactants, namely, O, air, consecutive O and H (O + H), and consecutive O and H (O + H) pulses were used with iridium acetylacetonate [Ir(acac)] to deposit Ir, while IrO was deposited using Ir(acac) and O. Nucleation was studied using a combination of methods for film thickness and morphology evaluation. In conformality studies, microscopic lateral high-aspect-ratio (LHAR) test structures, specifically designed for accurate and versatile conformality testing of ALD films, were used. The order of nucleation, from the fastest to the slowest, was O + H > air ≈ O > O > O + H, whereas the order of conformality, from the best to the worst, was O + H > O + H > O > O. In the O process, a change in film composition from IrO to metallic Ir was seen inside the LHAR structures. Compared to the previous reports on ALD of platinum-group metals, most of the studied processes showed good to excellent results.

Saturation profile based conformality analysis for atomic layer deposition: aluminum oxide in lateral high-aspect-ratio channels

“…11b). Increased penetration depth (in PillarHall-1) with decreased GPC has been observed in earlier works by Mattinen et al 47 for iridium ALD and by Puurunen and Gao 46 for Al 2 O 3 ALD at different temperatures.…”

“…Phys., 2020, 22, 23107--23120 | 23109 axis in a way analogous to the dimensionless distance used in this article. 1,2,40,47 Advantageously, this dimensionless distance is a well-defined physical quantity that remains constant irrespective of the extent of growth, while the AR experienced by the ALD process increases during the process with increasing film thickness through narrowing of the channel.…”

Sticking probabilities of H2O and Al(CH3)3 during atomic layer deposition of Al2O3 extracted from their impact on film conformality

“…24,25 Alternatively, lateral structures can be employed 6,7,26,27 which allow for top-view diagnostics to easily and accurately quantify the conformality and properties of the deposited film. The microscopic lateral-high-aspect-ratio (LHAR) trenches developed by Puurunen and co-workers, 7,14,28,29 named as PillarHall ® technology, have been adopted in this work. In the used third generation LHAR structures (LHAR3), a polysilicon membrane, supported by a network of Si pillars, is suspended above a c-Si substrate with a nominal gap height of 500 nm.…”

Modeling growth kinetics of thin films made by atomic layer deposition in lateral high-aspect-ratio structures

“…The LHAR structures consist of a long, narrow lateral gap of typically 500 nm in height (analogous to a vertical trench but rotated 90 ) in a polysilicon membrane, supported by pillars. The first LHAR prototypes have been used for conformality analysis of the ALD Al 2 O 3 -, TiO 2 -and Ir-based thin films (Gao, 2015;Mattinen, 2016;. This work uses LHAR (PillarHall V R ) prototypes with a new all-silicon design made by a fabrication process resembling that previously reported (Gao, 2015).…”