Rapid Wafer-Scale Growth of Polycrystalline 2H-MoS₂ by Pulsed Metal–Organic Chemical Vapor Deposition

Abstract

High volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultra-thin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metalorganic chemical vapor deposition (MOCVD) route for MoS2 film growth in a research-grade single-wafer reactor. Using bis(tert-butylimido)-bis(dimethylamido)molybdenum and diethyl disulfide we deposit MoS2 films from ≈ 1 nm to ≈ 25 nm in thickness on SiO2/Si substrates. We show that layered 2H-MoS2 can be produced at comparatively low reaction temperatures of 591 °C at short deposition times, approximately 90 s for few-layer films. In addition to the growth studies performed on SiO2/Si, films with wafer-level uniformity are demonstrated on 50 mm quartz wafers. Process chemistry and impurity incorporation from precursors are also discussed. This low-temperature and fast process highlights the opportunities presented by metalorganic reagents in the controlled synthesis of TMDs.

Morphology-controlled MoS2 by low-temperature atomic layer deposition

“…4c). 44 Interestingly, the sample produced at a higher temperature sulfurization shows no signals belonging to Mo 6+ , compared to the 17.4% of Mo 6+ in the sample of MoS 2 /CNT-200, which indicates that all Mo components completely convert to MoS 2 during high-temperature sulfurization. The broad peak around 228.3 eV could be ascribed to elemental S, which can be further confirmed from the S 2p spectrum.…”

“…4a). According to the literature, the low binding energy doublet can be readily ascribed to MoS 2 and the high binding energy one to the MoO 3 , 44 which could be mainly ascribed to the insufficient reduction of high valence Mo 6+ by such a low sulfurization temperature of 300°C, as well as the oxidation of the MoS 2 film at the near-surface when it is exposed to the air. In 45 Compared to the as-synthesized sample without postannealing, the MoS 2 /CNTs-200 sample with post-ALD annealing under H 2 S shows comparatively a lower binding energy of Mo 3d 5/2 , which indicates a lower valence state of Mo (Fig.…”

Large area few-layer TMD film growths and their applications

“…This method yielded highly uniform 5 cm diameter films of MoS 2 on Si/SiO 2 substrates. These growths produced smaller areas than those achieved by Kang et al, but instead of requiring 26 h they may be achieved in as little as 90 s [28]. The discretization of precursor injection allowed for precise control of layer number, with each pulse of precursor calibrated to offer around one layer's worth of reactants.…”

“…Unfortunately, low reactant flux results in a slow growth: the full process requires 26 h. Given the energetic costs of the growth process, including the demands of temperatures above 500 • C and pressures below 10 Torr, a shorter growth time would make this strategy far more practical [27]. Kalanyan et al [28] developed a novel 'pulsed' MOCVD technique, in which injection of precursors were discretized. This method yielded highly uniform 5 cm diameter films of MoS 2 on Si/SiO 2 substrates.…”

“…The discretization of precursor injection allowed for precise control of layer number, with each pulse of precursor calibrated to offer around one layer's worth of reactants. These growths relied on the sublimation of solid metalorganic precursors into the reaction chamber [28]. Choi et al [29] called the use of solid precursors into question, noting that it was generally difficult to achieve repeatable growths with them due to variability in sublimation rates.…”