Facilitated by the increasing importance and demand of thin-film materials, plasma-enhanced atomic layer deposition (PEALD) has gained tremendous industrial interest as it offers a way to efficiently deposit thin-films with ultra-high conformity. Despite the variety of PEALD processes, there lacks a fundamental and general methodology to understand, characterize and control a realistic PEALD process system. To fully understand the PEALD process, a series of studies have been carried out in our previous work. First, a kinetic Monte-Carlo (kMC)-based microscopic model that describes the surface dynamics was implemented and a multiscale CFD model was developed to characterize the PEALD process. Additionally, a corresponding multiscale data-driven model was derived to efficiently explore the optimal operating condition in the process domain based-on an elementary cost-analysis. The successful development of the aforementioned models enables the further study into the process control of PEALD where disturbances in operating conditions are present. In this work, an integrated control scheme using a proportional-integral (PI) controller and a run-to-run (R2R) controller is proposed and implemented. Using the developed multiscale CFD model, the PEALD process under typical disturbances is simulated, and the controllers are applied in the process domain. The result demonstrates the successful mitigation of disturbances in operating pressure, inlet molar fraction and gas feeder temperature under the combined effort of both controllers.

Plasma-enhanced atomic layer deposition (PEALD) has demonstrated its superiority at coatingultra-conformal high dielectric thin-films, which are essential to the fin field-effect transistors (FinFETs) as well as the advanced 3D V-NAND (vertical Not-AND) flash memory cells. Despite the growing research interest, the exploration of the optimal operation policies for PEALD remains a complicated and expensive task. Our previous work has constructed a comprehensive 3D multiscale computational fluid dynamics (CFD) model for the PEALD process and demonstrated its potential to enhance the understanding of the process. Nevertheless, the limitation of computational resources and the relatively long computation time restrict the efficient exploration of the operating space and the optimal operating strategy. Thus, in this work, we apply a 2D axisymmetric reduction of the previous 3D model of PEALD reactors with and without the showerhead design. Furthermore, a data-driven model is derived based on a recurrent neural network (RNN) for process characterization. The developed integrated data-driven model is demonstrated to accurately characterize the key aspects of the deposition process as well as the gas-phase transport profile while maintaining computational efficiency. The derived data-driven model is further validated with the results from a full 3D multiscale CFD model to evaluate model discrepancy. Using the data-driven model, an operational strategy database is generated, from which the optimal operating conditions can be determined for the deposition of HfO2 thin-film based on an elementary cost analysis.

Facilitated by the increasing importance and demand of semiconductors for the smartphoneand even the automobile industry, thermal atomic layer deposition (ALD) has gained tremendous industrial interest as it offers a way to efficiently deposit thin-films with ultra-high conformity. It is chosen largely due to its superior ability to deliver ultra-conformal dielectric thin-films with high aspect-ratio surface structures, which are encountered more and more often in the novel design of metal-oxide-semiconductor field-effect transistors (MOSFETs) in the NAND (Not-And)-type flash memory devices. Based on the traditional thermal ALD method, the plasma enhanced atomic layer deposition (PEALD) allows for lower operating temperature and speeds up the deposition process with the involvement of plasma species. Despite the popularity of these two methods, the development of their operation policies remains a complicated and expensive task, which motivates the construction of an accurate and comprehensive simulation model. A series of studies have been carried out to elucidate the mechanisms and the conceptof the PEALD process. In particular, process characterization focuses on the development of a first-principles-based three-dimensional, multiscale computational fluid dynamics (CFD) model, together with reactor geometry optimizations, of SiO2 thinfilm thermal atomic layer deposition (ALD) using bis(tertiary-butylamino)silane (BTBAS) and ozone as precursors. Also, a comprehensive multiscale computational fluid dynamics (CFD) model incorporating the plasma generation chamber is used in the deposition of HfO2 thin-films utilizing tetrakis(dimethylamido) hafnium (TDMAHf) and O2 plasma as precursors. Despite the great deal of research effort, ALD and PEALD processes have not been fullycharacterized from the view point of process control. This study aims to use previously developed multiscale CFD simulation model to design and evaluate an optimized control scheme to deal with industrially-relevant disturbances. Specifically, an integrated control scheme using a proportional-integral (PI) controller and a run-to-run (R2R) controller is proposed and evaluated to ensure the deposition of high-quality conformal thin-films. The ALD and PEALD processes under typical disturbances are simulated using the multiscale CFD model, and the integrated controllers are applied in the process domain. Using the controller parameters determined from the open-loop results, the developed integrated PI-R2R controller successfully mitigates the disturbances in the reactor with the combined effort of both controllers.

Properties of thin films depend strongly upon the deposition technique and conditions chosen. In order to achieve the desired film, optimum deposition conditions have to be found by carrying out experiments in a trial-and error fashion with varying parameters. The data obtained on one growth apparatus are often not transferable to another. This is especially true for film deposition processes using a cold plasma because of our poor under standing of the mechanisms. Relatively precise studies have been carried out on the role that physical effects play in film formation such as sputter deposition. However, there are many open questions regarding processes that involve chemical reactions, for example, reactive sputter deposition or plasma enhanced chemical vapor deposition. Much further research is re quired in order to understand the fundamental deposition processes. A sys tematic collection of basic data, some of which may be readily available in other branches of science, for example, reaction cross sections for gases with energetic electrons, is also required. The need for pfasma deposition techniques is felt strongly in industrial applications because these techniques are superior to traditional thin-film deposition techniques in many ways. In fact, plasma deposition techniques have developed rapidly in the semiconductor and electronics industries. Fields of possible application are still expanding. A reliable plasma reactor with an adequate in situ system for monitoring the deposition conditions and film properties must be developed to improve reproducibility and pro ductivity at the industrial level.

Thin films of crystalline materials are typically synthesized by thermally decomposing vapor precursors on a catalytic substrate. Plasmas enable the process temperature to be lowered by assisting in decomposition of the precursor molecule through gas-phase excitation as in the case of plasma-enhanced chemical vapor deposition (PECVD) and plasma-enhanced atomic layer deposition (PEALD). In this work, we develop another plasma-assisted approach to synthesizing thin films which we term plasma-enhanced chemical film conversion (PECFC). Molecular precursors are first prepared as a thin film on a substrate by solution methods, and subsequently converted by a combination of heating and plasma treatment. In comparison to other thin film growth techniques, our approach circumvents the adsorption step to promote nucleation and reduce substrate interactions, allowing direct growth on metal-free substrates which eliminates the need for transfer. Additionally, the approach is additive, reducing materials wastage and producing materials at the point-of-need including patterned structures. Two examples of thin film materials will be presented that demonstrate the capabilities of this synthesis approach: hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2), both of which are layered materials and can be produced atomically thin. To synthesize h-BN, a single-molecular precursor, ammonia borane, is initially prepared as a thin film by spray deposition, spin coating, or ink jet printing, and subsequently converted in a cold-wall reactor with a planar, atmospheric-pressure dielectric barrier discharge. We show that h-BN synthesized by this process can be integrated in two-dimensional (2D)-based field effect transistor (FET) devices and improve the mobility by up to 4 times over silicon dioxide. To synthesize MoS2, a similar approach of converting its corresponding single-molecule precursor, ammonium tetrathiomolybdate with a plasma has been studied. In this case, a single-step conversion leads to a rough, nanostructured film. Adding a second thermal annealing step produces a very smooth (RMS

As the minimum feature size in complementary metal-oxide-semiconductor (CMOS) devices shrinks, the leakage current through the gate insulator (silicon oxide) will increase sufficiently to impair device operation. A high dielectric constant (k) insulator is needed as a replacement for silicon oxide in order to reduce this leakage. Hafnium-based materials are among the more promising candidates for the gate insulator, however, it is hampered by material quality and thus has been slow to be introduced into high volume integrated circuit production. Hafnium oxynitride films are deposited by Metalorganic Chemical Vapor Deposition (MOCVD) and downstream microwave Plasma Enhanced Chemical Vapor Deposition (PECVD) employing different oxidants including O2, N2O, O2 plasma, N2O plasma, N2O/N2 plasma, and O2/He plasma in the current research. The effects of oxidants on deposition kinetics, morphology, composition, bonding structure, electrical properties and thermal stability of the resultant films each are investigated. The possible chemical/physical causes of these observations are developed and some mechanisms are proposed to explain the experimental results. Oxygen radicals, which are known of present in oxidizing environments are determined to play an essential role in defining both structures and the resultant electronic properties of deposited hafnium oxynitride films. This systematic investigation of oxidant effects on CVD grown hafnium oxide/oxynitride layers, in the absence of post-deposition annealing, provides new understanding to this area with potential importance to the integrated circuit industry.