Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.

Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

Atomic layer deposition (ALD) is gaining attention as a thin film deposition method, uniquely suitable for depositing uniform and conformal films on complex three-dimensional topographies. The deposition of a film of a given material by ALD relies on the successive, separated, and self-terminating gas–solid reactions of typically two gaseous reactants. Hundreds of ALD chemistries have been found for depositing a variety of materials during the past decades, mostly for inorganic materials but lately also for organic and inorganic–organic hybrid compounds. One factor that often dictates the properties of ALD films in actual applications is the crystallinity of the grown film: Is the material amorphous or, if it is crystalline, which phase(s) is (are) present. In this thematic review, we first describe the basics of ALD, summarize the two-reactant ALD processes to grow inorganic materials developed to-date, updating the information of an earlier review on ALD [R. L. Puurunen, J. Appl. Phys. 97, 121301 (2005)], and give an overview of the status of processing ternary compounds by ALD. We then proceed to analyze the published experimental data for information on the crystallinity and phase of inorganic materials deposited by ALD from different reactants at different temperatures. The data are collected for films in their as-deposited state and tabulated for easy reference. Case studies are presented to illustrate the effect of different process parameters on crystallinity for representative materials: aluminium oxide, zirconium oxide, zinc oxide, titanium nitride, zinc zulfide, and ruthenium. Finally, we discuss the general trends in the development of film crystallinity as function of ALD process parameters. The authors hope that this review will help newcomers to ALD to familiarize themselves with the complex world of crystalline ALD films and, at the same time, serve for the expert as a handbook-type reference source on ALD processes and film crystallinity.

Crystallinity of inorganic films grown by atomic layer deposition: Overview and general trends

A memory cell array has a first and a second storage area. The first storage area has a memory elements selected by an address signal. The second storage area has a memory elements selected by a control signal. A control circuit has a fuse element. When the fuse element has been blown, the control circuit inhibits at least one of writing and erasing from being done on the second storage area.

Nonvolatile Semiconductor Memory Device

A structure for a field effect transistor on a substrate that includes a gate stack, an isolation structure and a source/drain (S/D) recess cavity below the top surface of the substrate disposed between the gate stack and the isolation structure. The recess cavity having a lower portion and an upper portion. The lower portion having a first strained layer and a first dielectric film. The first strained layer disposed between the isolation structure and the first dielectric film. A thickness of the first dielectric film less than a thickness of the first strained layer. The upper portion having a second strained layer overlying the first strained layer and first dielectric film.

Method for fabricating a strained structure

A method for controlling the position of air gaps in intermetal dielectric layers between conductive lines and a structure formed using such a method. A first dielectric layer is deposited over at least two features and a substrate and an air gap is formed between the at least two features and above the feature height. The first dielectric layer is etched between the at least two features to open the air gap. Then a second dielectric layer is deposited over the etched first dielectric layer to form an air gap between the at least two features and completely below the feature height.

Control of air gap position in a dielectric layer

An OXO-type inter-poly insulator (where X is a high-K metal oxide and O is an insulative oxide) is defined by forming an amorphous metal oxide layer on a silicon-based insulator (e.g., a silicon oxide layer) and then nitridating at least upper and lower sub-layers of the amorphous metal oxide with a low temperature plasma treatment that maintains temperature below the recrystallization temperature of the amorphous material. Such a plasma treatment has been found to improve breakdown voltage characteristics of the insulator. In one embodiment, the metal oxide includes aluminum oxide and it is fluorinated with low temperature plasma prior to nitridation.

Low temperature nitridation of amorphous high-K metal-oxide in inter-gates insulator stack

An interpoly dielectric stack consisting of silicon dioxide, aluminum oxide, and silicon dioxide (OAO stack) has been proposed to replace the oxide-nitride-oxide (ONO) stack in flash memory. Atomic layer deposition and annealing conditions of Al2O3 films were studied to achieve low equivalent oxide thickness (EOT) and leakage current. Aluminum oxide films were deposited from alternating pulses of trimethylaluminum and ozone. The within-wafer nonuniformity and wafer-to-wafer thickness repeatability were both typically below 1.0% (1σ). The OAO interpoly dielectric exhibited leakage current density below 0.1μA∕cm2 at an electric field of 5MV∕cm while an 11% reduction in EOT to 12.5nm was achieved as compared with an ONO stack. The OAO stack has higher breakdown field and greater charge to breakdown than the ONO stack.

Equivalent oxide thickness reduction of interpoly dielectric using ALD-Al2O3 for flash device application

A method for manufacturing a low temperature removable silicon dioxide hard mask for patterning and etching is provided, wherein tetra-ethyl-ortho-silane (TEOS) is used to deposit a silicon dioxide hard mask.

Use of TEOS oxides in integrated circuit fabrication processes

A high density plasma chemical vapor deposition (HDP-CVD) process is used to deposit silicon dioxide in trenches of various widths. The thickness of the silicon dioxide filling both narrow and wide trenches is made more uniform by reducing an HDP-CVD etch to deposition ratio. The lowered etch to deposition ratio is achieved by lowering a ratio of oxygen to silane gas, by lowering the power of a high frequency bias signal, and by lowering the total gas flow rate.

Reduced thickness variation in a material layer deposited in narrow and wide integrated circuit trenches

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