Ajm Adrie Mackus

Surface reactions during atomic layer deposition of Pt derived from gas phase infrared spectroscopy

Infrared spectroscopy was used to obtain absolute number information on the reaction products during atomic layer deposition of Pt from (methylcyclopentadienyl)trimethylplatinum [(MeCp)PtMe3] and O2. From the detection of CO2 and H2O it was established that the precursor ligands are oxidatively decomposed during the O2 pulse mainly. Oxygen atoms chemisorbed at the Pt lead to likewise ligand oxidation during the (MeCp)PtMe3 pulse however the detection of a virtually equivalent density of CO2 and CH4 also reveals a concurrent ligand liberation reaction. The surface coverage of chemisorbed oxygen atoms found is consistent with the saturation coverage reported in surface science studies.

Optical emission spectroscopy as a tool for studying, optimizing, and monitoring plasma-assisted atomic layer deposition processes

In this note it is demonstrated that optical emission spectroscopy (OES) is an easy-to-implement and valuable tool to study, optimize, and monitor thin film growth by plasma-assisted atomic layer deposition (ALD). The species in the plasma can be identified through the analysis of the light emitted by the plasma. OES provides therefore information on the reactant species delivered to the surface by the plasma but it also yields unique insight into the surface reaction products and, as a consequence, on the reaction mechanisms of the deposition process. Time-resolved measurements reveal information about the amount of precursor dosing and length of plasma exposure needed to saturate the self-limiting half reactions, which is useful for the optimization of the ALD process. Furthermore, time-resolved OES can also be used as an easy-to-implement process monitoring tool for plasma-assisted ALD processes on production equipment; for example, to monitor reactor wall conditions or to detect process faults in real time.

Nucleation and growth of Pt atomic layer deposition on Al2O3 substrates using (methylcyclopentadienyl)-trimethyl platinum and O2 plasma

The nucleation and growth of Pt atomic layer deposition (ALD) on Al2O3 substrates was studied using (methylcyclopentadienyl)-trimethyl platinum (MeCpPtMe3) and O2 plasma as the reactants. The nucleation of Pt ALD was examined on Al2O3 ALD substrates at 300 °C using a variety of techniques including spectroscopic ellipsometry, x-ray reflectivity, x-ray photoelectron spectroscopy, and scanning electron microscopy. These techniques revealed that Pt ALD does not nucleate and grow immediately on the Al2O3 ALD substrates. There was negligible Pt ALD during the first 38 ALD cycles. The Pt ALD growth rate then increased substantially during the next 12 ALD cycles. Subsequently, the Pt ALD growth rate reached a steady state linear growth regime for >50 ALD cycles. These measurements suggest that the Pt ALD first forms a number of nanoclusters that grow slowly during the first 38 ALD cycles. These islands then merge during the next 12 cycles and yield a steady state Pt ALD growth rate of ∼0.05 nm/cycle for >50 ALD ...

Remote Plasma ALD of Platinum and Platinum Oxide Films

Platinum and platinum oxide films were deposited by remote plasma atomic layer deposition (ALD) from the combination of (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe 3 ) precursor and O 2 plasma. A short O 2 plasma exposure (0.5 s) resulted in low resistivity (15 μΩ cm), high density (21 g/cm 3 ), cubic Pt films, whereas a longer O 2 plasma exposure (5 s) resulted in semiconductive PtO 2 films. In situ spectroscopic ellipsometry studies revealed no significant nucleation delay, different from the thermal ALD process with O 2 gas which was used as a benchmark. A broad temperature window (100―300°C) for remote plasma ALD of Pt and PtO 2 was demonstrated.

Local deposition of high-purity Pt nanostructures by combining electron beam induced deposition and atomic layer deposition

An approach for direct-write fabrication of high-purity platinum nanostructures has been developed by combining nanoscale lateral patterning by electron beam induced deposition (EBID) with area-selective deposition of high quality material by atomic layer deposition (ALD). Because virtually pure, polycrystalline Pt nanostructures are obtained, the method extends the application possibilities of EBID, whereas compared to other area-selective ALD approaches, a much higher resolution is attainable; potentially down to sub-10 nm lateral dimensions.

Synthesis and in situ characterization of low-resistivity TaNx films by remote plasma atomic layer deposition

Remote plasma atomic layer deposition (ALD) of TaNx films from Ta[N(CH3)2]5 and H2, H2-N2, and NH3 plasmas is reported. From film analysis by in situ spectroscopic ellipsometry and various ex situ techniques, data on growth rate, atomic composition, mass density, TaNx microstructure, and resistivity are presented for films deposited at substrate temperatures between 150 and 250°C. It is established that cubic TaNx films with a high mass density (12.1gcm−3) and low electrical resistivity (380μΩcm) can be deposited using a H2 plasma with the density and resistivity of the films improving with plasma exposure time. H2-N2 and NH3 plasmas resulted in N-rich Ta3N5 films with a high resistivity. It is demonstrated that the different TaNx phases can be distinguished in situ by spectroscopic ellipsometry on the basis of their dielectric function with the magnitude of the Drude absorption yielding information on the resistivity of the films. In addition, the saturation of the ALD surface reactions can be determined...

Nanopatterning by direct-write atomic layer deposition

A novel direct-write approach is presented, which relies on area-selective atomic layer deposition on seed layer patterns deposited by electron beam induced deposition. The method enables the nanopatterning of high-quality material with a lateral resolution of only ∼10 nm. Direct-write ALD is a viable alternative to lithography-based patterning with a better compatibility with sensitive nanomaterials.

Remote Plasma and Thermal ALD of Platinum and Platinum Oxide Films

Platinum and platinum oxide films were deposited using thermal and remote plasma ALD. The combination of MeCpPtMe3 precursor and O2 gas or a short (0.5 s) O2 plasma exposure resulted in high purity, low-resistivity (15 microOhm cm), high-density (21 g/cm3), cubic platinum films. The combination of MeCpPtMe3 precursor with a longer (5 s) O2 plasma exposure resulted in semi-conductive PtO2 films with a band gap of ~1.5 eV. The long nucleation delay observed with the thermal process could be overcome by using the remote plasma process where atomic oxygen is provided from the gas phase. The ALD process dependence on substrate temperature was investigated, where both the thermal and the remote plasma Pt process revealed a temperature window from 200 C to 300 C and the remote plasma PtO2 process had a temperature window from 100 C to 300 C.

In situ spectroscopic ellipsometry during atomic layer deposition of Pt, Ru and Pd

The preparation of ultra-thin platinum-group metal films, such as Pt, Ru and Pd, by atomic layer deposition (ALD) was monitored in situ using spectroscopic ellipsometry in the photon energy range of 0.75–5 eV. The metals’ dielectric function was parametrized using a ‘flexible’ Kramers–Kronig consistent dielectric function because it was able to provide accurate curve shape control over the optical response of the metals. From this dielectric function, it was possible to extract the film thickness values during the ALD process. The important ALD process parameters, such as the nucleation period and growth per cycle of Pt, Ru and Pd could be determined from the thickness evolution. In addition to process parameters, the film resistivity in particular could be extracted from the modeled dielectric function. Spectroscopic ellipsometry thereby revealed itself as a feasible and valuable technique to be used in research and development applications, as well as for process monitoring during ALD.