Numerical study on the effectiveness of precursor isolation using N2 as gas barrier in spatial atomic layer deposition

Pan, Dongqing

doi:10.1016/j.ijheatmasstransfer.2019.118642

Cited by 12 publications

(6 citation statements)

References 30 publications

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“…ALD reactors and processes for planar wafers have been studied extensively, 17–39 whereas ALD on porous media for membrane preparation has not been investigated at the same level 7,40–49 of detail. A major difference between typical ALD and ALD for thin‐film membrane fabrication is that the former aims to completely consume available sites during each ALD cycle.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of atomic layer deposition for thin deposit formation in a mesoporous substrate

et al. 2021

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ZnO deposition in porous γ‐Al2O3 via atomic layer deposition (ALD) is the critical first step for the fabrication of zeolitic imidazolate framework membranes using the ligand‐induced perm‐selectivation process (Science, 361 (2018), 1008–1011). A detailed computational fluid dynamics (CFD) model of the ALD reactor is developed using a finite‐volume‐based code and validated. It accounts for the transport processes within the feeding system and reaction chamber. The simulated precursor spatiotemporal profiles assuming no ALD reaction were used as boundary conditions in modeling diethylzinc reaction/diffusion in porous γ‐Al2O3, the predictions of which agreed with experimental electron microscopy measurements. Further simulations confirmed that the present deposition flux is much less than the upper limit of flux, below which the decoupling of reactor/substrate is an accurate assumption. The modeling approach demonstrated here allows for the design of ALD processes for thin‐film membrane formation including the synthesis of metal–organic framework membranes.

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Section: Introductionmentioning

confidence: 99%

Numerical simulation of atomic layer deposition for thin deposit formation in a mesoporous substrate

et al. 2021

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“…Increasing the flow rate ratio (Figure 2e) for constant precursor flow rate decreased the overlap between the two precursor concentration curves and allowed us to go from film growth by CVD (Figure 2e, FRR = 1) in 48% of the substrate length to film growth by ALD (Figure 2e, FRR = 5 and FRR = 10) in the entire substrate. The fact that increasing the flow rate ratio reduced the precursor intermixing is consistent with previous results 29 and is the consequence of the increasing separation of precursors induced by the increasing flow rate of inert gas relative to those of the precursors. However, it is important to note that increasing the flow rate ratio also led to a decrease in the maximum concentration of precursors near the substrate, because the higher dilution of the precursors inside the gap reduced the diffusive transport due to the lower diffusion times associated with the larger velocities.…”

Section: Influence Of Parameters Onmentioning

confidence: 99%

“…Some of the parameters that can be leveraged to minimize the mixing of precursors during deposition of thin films have been identified. For instance, decreasing the gap between the substrate and the deposition head and increasing the flow rate of the separation gas have been shown to prevent precursor mixing in SALD systems for porous, nonporous, − and microgroove substrates. The application of a slight vacuum at the exhausts, which makes them more efficient at purging the precursors, is also known to decrease precursor intermixing, , although some deposition head designs can operate well without vacuum at the exhaust .…”

Section: Introductionmentioning

confidence: 99%

Can We Rationally Design and Operate Spatial Atomic Layer Deposition Systems for Steering the Growth Regime of Thin Films?

et al. 2023

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Fine control over the growth of materials is required to precisely tailor their properties. Spatial atomic layer deposition (SALD) is a thin-film deposition technique that has recently attracted attention because it allows producing thin films with a precise number of deposited layers, while being vacuum-free and much faster than conventional atomic layer deposition. SALD can be used to grow films in the atomic layer deposition or chemical vapor deposition regimes, depending on the extent of precursor intermixing. Precursor intermixing is strongly influenced by the SALD head design and operating conditions, both of which affect film growth in complex ways, making it difficult to predict the growth regime prior to depositions. Here, we used numerical simulation to systematically study how to rationally design and operate SALD systems for growing thin films in different growth regimes. We developed design maps and a predictive equation allowing us to predict the growth regime as a function of the design parameters and operation conditions. The predicted growth regimes match those observed in depositions performed for various conditions. The developed design maps and predictive equation empower researchers in designing, operating, and optimizing SALD systems, while offering a convenient way to screen deposition parameters, prior to experimentation.

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“…A major difference between these studies is that the SALD tool used here was not located inside a particle-controlled cleanroom unlike the conventional ALD tool, which resulted in an increased particle level during the SALD passivation. Additionally, SALD films were potentially less dense than obtained with pulsing ALD, as the growth of SALD AlOx is likely to contain a CVD-like component resulting from the intermixing of precursors during deposition 22,23 . The initial Qtot values between this study and the ones in our previous work 32 were comparable, so we speculate that the potential lower density of the film and an increased number of pinholes due to particles led to the accelerated degradation of Qtot in the SALD films.…”

Section: B Passivation Stability Under Damp Heat Exposurementioning

confidence: 99%

“…Furthermore, we investigate how the faster film growth achieved with SALD influences the film quality and thus the stability of AlOx passivation under both light soaking and damp heat exposure. SALD has a higher deposition rate compared to pulsing ALD, but the film growth in SALD might be disturbed by precursor intermixing 22,23 , leading to decreased film quality. Therefore, understanding the extent of effects induced by light, elevated temperature and moisture in SALD AlOx-passivated nanostructured silicon is vital for the wide-scale application of such devices.…”

Section: Introductionmentioning

confidence: 99%

AlOx surface passivation of black silicon by spatial ALD: Stability under light soaking and damp heat exposure

Heikkinen

Koutsourakis

Virtanen

et al. 2020

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Scientific breakthroughs in silicon surface passivation have enabled commercial high-efficiency photovoltaic devices making use of the black silicon nanostructure. In this study, we report on factors that influence the passivation stability of black silicon realized with industrially viable Spatial Atomic Layer Deposited (SALD) aluminum oxide (AlOx) under damp heat exposure and light soaking. Damp heat exposure conditions are 85°C and 85% relative humidity, and light soaking is performed with 0.6 Sun illumination at 75°C. It is demonstrated that reasonably thick (20 nm) passivation films are required for both black and planar surfaces in order to provide stable surface 2 passivation over a period of 1000 h under both testing conditions. Both surface textures degrade at similar rates with 5 nm and 2 nm thick films. The degradation mechanism under damp heat exposure is found to be different from that in light soaking. During damp heat exposure, the fixed charge density of AlOx is reduced, which decreases the amount of field-effect passivation. Degradation under light soaking, on the other hand, is likely to be related to interface defects between silicon and the passivating film. Finally, a thin chemically-grown SiOx layer at the interface between the AlOx film and the silicon surface is shown to significantly increase the passivation stability under both light soaking and damp heat exposure. The results of this study provide valuable insights on surface passivation degradation mechanisms on nanostructured silicon surfaces, and pave the way for the industrial production of highly stable black silicon devices.

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Numerical study on the effectiveness of precursor isolation using N2 as gas barrier in spatial atomic layer deposition

Cited by 12 publications

References 30 publications

Numerical simulation of atomic layer deposition for thin deposit formation in a mesoporous substrate

Numerical simulation of atomic layer deposition for thin deposit formation in a mesoporous substrate

Can We Rationally Design and Operate Spatial Atomic Layer Deposition Systems for Steering the Growth Regime of Thin Films?

AlOx surface passivation of black silicon by spatial ALD: Stability under light soaking and damp heat exposure

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