consisting of two or more alternating self-limiting surface reactions. These selflimiting surface reactions enable thin-film deposition with thickness uniformity over large-area substrates, (sub-) monolayer thickness control, and conformal deposition in 3D structures. [1] During the first ALD cycles the precursors mainly react with the substrate rather than with the ALD-grown material. The surface termination of the substrate can therefore strongly affect the growth behavior during this initial period. [1][2][3] Depending on the nature of the ALD-grown material, the substrate, and the process conditions, ALD can lead to different growth regimes, resulting, for instance, in the deposition of ultrathin continuous films, deposition of highly dispersed nanoparticles, or area-selective deposition. [4] Continuous thin films have a wide variety of applications including nanoelectronics, coatings, and optical components, and their deposition requires either 2D growth or high particle density to achieve fast film closure. Nanoparticles dispersed on a surface are desired for heterogeneous catalysis, and their production requires island-type deposition with a well-defined particle size and particle density. Area-selective deposition can enable nanoscale bottom-up patterning, which allows accurate self-alignment between small features which is difficult to achieve in conventional top-down patterning. [5] To enable area-selective deposition, the growth behavior should be surface-dependent such that the deposition is at the same time favored on designated areas of the substrate and inhibited on others. For each of the aforementioned applications, an understanding of the surface dependence of the initial stages of growth can inform the tailoring of the ALD process to the desired application. [6] ALD of noble metals has received considerable attention because of its potential in applications such as catalysis [7] and nanoelectronic devices. [8] Ruthenium is considered an ideal candidate for novel nanoscale catalysts [9,10] as well as for replacing copper as a conductor in future low-level nano-interconnect structures for integrated circuits. [8] ALD of Ru however presents application-specific challenges. On one hand, nanoparticles of a specific size are desired for high catalytic activity. [10] On Understanding the growth mechanisms during the early stages of atomic layer deposition (ALD) is of interest for several applications including thin film deposition, catalysis, and area-selective deposition. The surface dependence and growth mechanism of (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl) ruthenium and O 2 ALD at 325 °C on HfO 2 , Al 2 O 3 , OH, and SiOSi terminated SiO 2 , and organosilicate glass (OSG) are investigated. The experimental results show that precursor adsorption is strongly affected by the surface termination of the dielectric, and proceeds most rapidly on OH terminated dielectrics, followed by SiOSi and finally SiCH 3 terminated dielectrics. The initial stages of growth are characterized by the formation a...

Area-selective deposition (ASD) is a promising bottom-up manufacturing solution for catalysts and nanoelectronic devices. However, industrial applications are limited as highly selective ASD processes exist only for few materials. “Passivation/deposition/defect removal” cycles have been proposed to increase selectivity, but cycling requires the passivation to be selective to the growth surface as well as the ASD-grown material. Dimethylamino-trimethylsilane (DMA-TMS) can passivate SiO2 surfaces by covering them with −Si­(CH3)3 groups. However, the interaction of DMA-TMS with materials other than SiO2 and Si remains largely unknown and its compatibility with cycling is not yet understood. This work investigates the selectivity of metal, nitride, and oxide atomic layer deposition (ALD) to DMA-TMS-passivated SiO2 as well as the surface chemistry and selectivity of the DMA-TMS reaction. The ALD coreagents O2, NH3, and H2O show low reactivity with the −Si­(CH3)3-terminated surface at temperatures up to 300 °C, but the selectivity of ALD strongly depends on the metal precursor and temperature. We demonstrate that DMA-TMS is a selective passivation agent for ASD of and on TiO2, TiN, and Ru selective to SiO2, by TiCl4/H2O, TiCl4/NH3, and EBECHRu/O2 ALD, respectively. We investigate the DMA-TMS reaction on Ru and TiN/TiO2 growth surfaces under conditions that passivate SiO2. At least 77% of the area of the growth surface remains reactive for ALD, confirming the compatibility of DMA-TMS with cycling for ASD. We investigate the impact of changes in surface composition due to patterning before ASD and find that DMA-TMS removes F impurities on TiN and TiO2 surfaces. DMA-TMS selectively passivates SiO2 on three-dimensional (3D) nanopatterns, allowing preferential TiO2 deposition on a nonpassivated growth surface. Thus, the selectivity of DMA-TMS shows great promise to expand the ASD material space as well as to increase selectivity during ASD cycles.

The demand for transistors and memory devices with smaller feature sizes and increasingly complex architectures furthers the need for advanced thin film patterning techniques. A prepatterned, sacrificial layer can be used as a template for bottomup fill of new materials which would otherwise be difficult to pattern using traditional top-down lithographic methods. This work investigates initial growth of TiN, TiO 2 , and HfO 2 thin films during thermal atomic layer deposition (ALD) onto a high density, amorphous carbon (aC) sacrificial layer. ALD of TiN by TiCl 4 / NH 3 at 390 °C, TiO 2 by Ti(OCH 3 ) 4 /H 2 O at 250 °C, and HfO 2 by HfCl 4 /H 2 O at 300 °C on as-deposited aC films resulted in uninhibited, continuous thin film growth. We find that carbon surface reduction and passivation using a H 2 plasma resulted in delayed film coalescence for TiN, TiO 2 , and HfO 2 on the aC. After 200 TiN cycles on H 2 plasma-treated aC, Rutherford backscattering spectrometry shows Ti levels below the detection limit (8 × 10 13 at/cm 2 ), whereas SiO 2 or Si 3 N 4 substrates show TiN growth of ∼6 nm, corresponding to a selectivity of ∼200:1. Exposing plasma-treated aC to H 2 O induces nucleation for TiN ALD, consistent with favorable nucleation on hydroxyl sites. Therefore, the H 2 O co-reagent in TiO 2 and HfO 2 ALD contributes to loss of selectivity compared to TiN ALD using NH 3 . We confirm scaling of selectivity to sub-50 nm patterns using 45 nm aC/Si 3 N 4 line/space patterns, where 3.5 nm TiO 2 and 5.8 nm TiN films are deposited on Si 3 N 4 with minimal particle formation on aC, with selectivity loss primarily on feature corners and edges. We conclude that improved scaling of selectivity to nanometer scale patterns can be achieved by optimizing surface loading and extent of plasma exposure, and by further understanding shape effects in nanoscale surface plasma modification.

Reaction mechanisms in the LiN[Si(CH3)3]2–O3 atomic layer deposition (ALD) process for lithium silicate were investigated in situ with a quartz crystal microbalance (QCM) and a quadrupole mass spectrometer (QMS) at several temperatures. In addition, ex situ Fourier transform infrared (FT-IR) measurements were carried out to identify the bonds present in the films. QMS indicates typical combustion byproducts such as CO2 (m/z = 44), CO (m/z = 28), H2O (m/z = 18) and NO (m/z = 30) during the ozone pulse. Signals corresponding to the fragments of the ligands are present, but their low intensities imply that there are no direct ligand exchange reactions with the hydroxyl groups on the surface. QCM results confirm the decomposition of the ligand through complex reactions upon reaching the surface. Accordingly, several reaction pathways were drawn, and DFT calculations were performed to assess the reactivity of each reaction intermediate. The influence of the deposition temperature on several characteristics of the process such as composition of the film and growth per cycle was also explained.