Spatial Atomic Layer Deposition for large-area and flexible electronics

Large-area and flexible electronics could potentially benefit tremendously from the advantages of ALD over other deposition techniques. These applications, however, require deposition on large areas and on flexible substrates at deposition rates unattainable with conventional ALD. For this purpose, spatial ALD has been developed, which relies on spatial instead of temporal separation of precursor exposures. In this article, the pivotal role of the Dutch spatial ALD community is highlighted, and several examples of current challenges in spatial ALD are discussed

Single Nucleotide Polymorphism (SNP)-Based Loss of Heterozygosity (LOH) Testing by Real Time PCR in Patients Suspect of Myeloproliferative Disease

During tumor development, loss of heterozygosity (LOH) often occurs. When LOH is preceded by an oncogene activating mutation, the mutant allele may be further potentiated if the wild-type allele is lost or inactivated. In myeloproliferative neoplasms (MPN) somatic acquisition of JAK2V617F may be followed by LOH resulting in loss of the wild type allele. The occurrence of LOH in MPN and other proliferative diseases may lead to a further potentiating the mutant allele and thereby increasing morbidity. A real time PCR based SNP profiling assay was developed and validated for LOH detection of the JAK2 region (JAK2LOH). Blood of a cohort of 12 JAK2V617F-positive patients (n = 6 25–50% and n = 6>50% JAK2V617F) and a cohort of 81 patients suspected of MPN was stored with EDTA and subsequently used for validation. To generate germ-line profiles, non-neoplastic formalin-fixed paraffin-embedded tissue from each patient was analyzed. Results of the SNP assay were compared to those of an established Short Tandem Repeat (STR) assay. Both assays revealed JAK2LOH in 1/6 patients with 25–50% JAK2V617F. In patients with >50% JAK2V617F, JAK2LOH was detected in 6/6 by the SNP assay and 5/6 patients by the STR assay. Of the 81 patients suspected of MPN, 18 patients carried JAK2V617F. Both the SNP and STR assay demonstrated the occurrence of JAK2LOH in 5 of them. In the 63 JAK2V617F-negative patients, no JAK2LOH was observed by SNP and STR analyses. The presented SNP assay reliably detects JAK2LOH and is a fast and easy to perform alternative for STR analyses. We therefore anticipate the SNP approach as a proof of principle for the development of LOH SNP-assays for other clinically relevant LOH loci

About the importance of purge time in molecular layer deposition of alucone films

The deposition rate and properties of MLD films are for a large part determined by what happens during the reactant exposure step. In some cases, however, the purge step is of equal importance, for example in MLD of alucone using trimethylaluminum (TMA) and ethylene glycol (EG). We show that infiltration of TMA into the alucone film followed by its continuous outgassing during the subsequent EG exposure step can lead to undesired CVD effects. To avoid the CVD effects, very long TMA purge times are required which in turn significantly impact the obtainable deposition rates. We also developed a kinetic model that correlates process parameters like reactant partial pressures, exposure times, purge time and deposition temperature to the CVD component in the film growth. We observed that the overall GPC decreases exponentially with TMA purge time attributed to the decreasing CVD component and after a long enough purge time reaches a steady-state value of growth only due to the MLD component. It was also observed that the CVD contributions reduced with decreasing partial pressure of TMA and increasing deposition temperature. With an intention to improve the outgassing efficiency of TMA, the influence of purge gas flow on the CVD growth component is also briefly discussed. Moreover, to mitigate the problem of infiltration, we show that a bulkier substitute of TMA like dimethylaluminum isopropoxide (DMAI) shows no infiltration and can improve the alucone deposition rate by at least an order of magnitude

Spatial atmospheric pressure molecular layer deposition of alucone films using dimethylaluminum isopropoxide as the precursor

Trimethylaluminum is the most used aluminum precursor in atomic and molecular layer deposition (ALD/MLD). It provides high growth-per-cycle (GPC), is highly reactive and is relatively low cost. However, in the deposition of hybrid alucone films, TMA tends to infiltrate into the films requiring very long purge steps and thereby limiting the deposition rate (nm s−1) of the process. From our previous studies, we know that dimethylaluminum isopropoxide (DMAI) could be a potential candidate to substitute TMA in alucone depositions as it does not seem to infiltrate into the films. In this study, we perform a more detailed investigation of MLD of alucone on an atmospheric pressure spatial MLD system using DMAI as the aluminum precursor. The effect of deposition temperature and reactant purge times on the overall GPC has been investigated and a decreasing GPC with increasing deposition temperature and increasing EG purge time has been observed. Furthermore, the DMAI alucone films have been compared for their chemical environment and degradation with the films prepared using TMA and EG, showing striking similarities between the two. The results demonstrate that DMAI can be used as an alternative precursor to TMA for MLD of alucone films and this work can be used as a guide for designing efficient MLD processes in the future

Molecular layer deposition of alucone in high aspect ratio trenches: The effect of TMA outgassing on step-coverage

Infiltration of trimethylaluminum (TMA) in molecular layer deposition-enabled alucone thin films on planar substrates is a common observation reported in the literature. An insufficient TMA purge time in such cases is often found to lead to a CVD component in the overall film growth due to the reactions between the outgassing TMA and the co-reactant. In this work, the effect of the CVD component on the step coverage of alucone films when grown in high-aspect ratio trenches is studied. The thickness was initially found to increase with increasing distance from the trench aperture before starting to decrease up to the film’s maximum penetration depth. With the support of modeling, the reason behind the observed thickness profile was investigated and attributed to the combination of an increasing outgassing rate of TMA and a decreasing ethylene glycol (EG) concentration along the trench depth. Furthermore, the maximum thickness and the position where it is obtained in the trench are found to depend on TMA and EG doses, TMA purge time, the trench height, and the trench depth. Finally, the possibility of adopting the additional CVD component in film growth for void-less gap fill of 3D trenches is discussed, as well as the suppression of the same CVD component, without compromising the growth rate, by using dimethylaluminum isopropoxide as a substitute for TMA is evaluated

Large-area spatial atomic layer deposition of amorphous oxide semiconductors at atmospheric pressure

Indium Gallium Zinc Oxide (IGZO) films are deposited using plasma-enhanced spatial Atomic Layer Deposition (sALD) on substrates as large as 32 cm x 35 cm. Excellent uniformity and thickness control leads to high-performing and stable co-planar top-gate self-aligned (SA) thin-film transistors (TFTs), demonstrating the viability of atmospheric spatial ALD as a novel deposition technique for the flat-panel display Industry