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

The scaling of complementary metal oxide semiconductor transistors has led to the silicon dioxide layer, used as a gate dielectric, being so thin (14?nm) that its leakage current is too large It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (?) or 'high K' gate oxides such as hafnium oxide and hafnium silicate These oxides had not been extensively studied like SiO2, and they were found to have inferior properties compared with SiO2, such as a tendency to crystallize and a high density of electronic defects Intensive research was needed to develop these oxides as high quality electronic materials This review covers both scientific and technological issues?the choice of oxides, their deposition, their structural and metallurgical behaviour, atomic diffusion, interface structure and reactions, their electronic structure, bonding, band offsets, electronic defects, charge trapping and conduction mechanisms, mobility degradation and flat band voltage shifts The oxygen vacancy is the dominant electron trap It is turning out that the oxides must be implemented in conjunction with metal gate electrodes, the development of which is further behind Issues about work function control in metal gate electrodes are discussed

https://iopscience.iop.org/article/10.1088/0034-4885/69/2/R02/pdf

High dielectric constant gate oxides for metal oxide Si transistors

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

The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin (1.4 nm) that its leakage current is too large. It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (κ) or 'high K' gate oxides such as hafnium oxide and hafnium silicate. Little was known about such oxides, and it was soon found that in many respects they have inferior electronic properties to SiO2 ,s uch as a tendency to crystallise and a high concentration of electronic defects. Intensive research is underway to develop these oxides into new high quality electronic materials. This review covers the choice of oxides, their structural and metallurgical behaviour, atomic diffusion, their deposition, interface structure and reactions, their electronic structure, bonding, band offsets, mobility degradation, flat band voltage shifts and electronic defects. The use of high K oxides in capacitors of dynamic random access memories is also covered.

/pdf/high-dielectric-constant-oxides-cotu2e70vd.pdf

High dielectric constant oxides

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Electron paramagnetic resonance (EPR) measurements of Si/SiO2 systems began over 30 years ago. Most EPR studies of Si/SiO2 systems have dealt with two families of defects: Pb centers and E′ centers. Several variants from each group have been observed in a wide range of Si/SiO2 samples. Some of the most basic aspects of this extensive, body of work remain controversial. EPR is an extraordinary powerful analytical tool quite widely utilized in chemistry, biomedical research, and solid state physics. Although uniquely well suited for metal–oxide–silicon (MOS) device studies, its capabilities are not widely understood in the MOS research and development community. The impact of EPR has been limited in the MOS community by a failure of EPR spectroscopists to effectively communicate with other engineers and scientists in the MOS community. In this article we hope to, first of all, ameliorate the communications problem by providing a brief but quantitative introduction to those aspects of EPR which are most relevant to MOS systems. We review, critically, those aspects of the MOS/EPR literature which are most relevant to MOS technology and show how this information can be used to develop physically based reliability models. Finally, we briefly review EPR work dealing with impurity defects in oxide thin films.

/pdf/what-can-electron-paramagnetic-resonance-tell-us-about-the-45o4ny6zla.pdf

What can electron paramagnetic resonance tell us about the Si/SiO2 system?

An atomic layer deposition method to deposit a oxide thin film is provided. The method employs a nitrate ligand in a first hafnium precursor as an oxidizer for a second hafnium precursor to form the hafnium oxide. Using a hafnium nitrate precursor and a hafnium chloride precursor, the method is well suited for the deposition of a high k hafnium oxide dielectric for gate dielectric or capacitor dielectric applications on a hydrogen-terminated silicon surface.

Atomic layer deposition of oxide film

Thin-film transistors (TFTs) fabricated using amorphous oxide semiconductors (AOS) exhibit good electron mobility (5 to >; 50 cm2/V · s), they are transparent, and they can be processed at low temperatures. These new materials show a great promise for high-performance large-area electronics applications such as flexible electronics, transparent electronics, and analog current drivers for organic light-emitting diode displays. Before any of these applications can be commercialized, however, a strong understanding of the stability and reliability of AOS TFTs is needed. The purpose of this paper is to provide a comprehensive review and summary of the recently emerging work on the stability and reliability of AOS TFTs with respect to illumination, bias stress, ambient effects, surface passivation, mechanical stress, and defects, as well as to point out areas for future work. An overview of the TFT operation and expected reliability concerns as well as a brief summary of the instabilities in the well-known Si3N4/a-Si:H system is also included.

/pdf/instabilities-in-amorphous-oxide-semiconductor-thin-film-3kxb6koeq7.pdf

Instabilities in Amorphous Oxide Semiconductor Thin-Film Transistors

A method for selective ALD of ZnO on a wafer preparing a silicon wafer; patterning the silicon wafer with a blocking agent in selected regions where deposition of ZnO is to be inhibited, wherein the blocking agent is taken from a group of blocking agents includes isopropyl alcohol, acetone and deionized water; depositing a layer of ZnO on the wafer by ALD using diethyl zinc and H 2 O at a temperature of between about 140° C. to 170° C.; and removing the blocking agent from the wafer.

Method to perform selective atomic layer deposition of zinc oxide

An atomic layer deposition method to deposit an oxide nanolaminate thin film is provided. The method employs a nitrate ligand in a first precursor as an oxidizer for a second precursor to form the oxide nanolaminates. Using a hafnium nitrate precursor and an aluminum precursor, the method is well suited for the deposition of a high k hafnium oxide/aluminum oxide nanolaminate dielectric for gate dielectric or capacitor dielectric applications on a hydrogen-terminated silicon surface.

John F. Conley

Papers

What can electron paramagnetic resonance tell us about the Si/SiO2 system?

Atomic layer deposition of oxide film

Instabilities in Amorphous Oxide Semiconductor Thin-Film Transistors

Method to perform selective atomic layer deposition of zinc oxide

Nanolaminate film atomic layer deposition method