Atomic layer deposition precursor

Several patents dealing with the use of volatile metal amidinate complexes in MOCVD or ALD processes have appeared in the literature.The use of volatile amidinato complexes of Al, Ga, and In in the chemical vapor deposition of the respective nitrides has been reported. For example, [PhC(NPh)2]2GaMe was prepared in 68% yield from GaMes and N,N -diphenylbenzamidine in toluene. Various samples of this and related complexes could be heated to 600 °C in N2 to give GaN. A series of homoleptic metal amidinates of the general type [MIRCfNROilnl (R = Me, Bu R = Pr, BuO has been prepared for the transition metals Ti, V, Mn, Fe, Co, Ni, Cu, Ag, and La. The types of products are summarized in Scheme 226. The new compounds were found to have properties well-suited for use as precursors for atomic layer deposition (ALD) of thin films. 

Atomic layer deposition is a high vacuum process where small amounts of the precursors are leaked into the system sequentially with intermittent evacuations. The ALD enables the conformal deposition of atomically thin layers with precise thickness control at low temperatures without the typical aggregate formation in the gas-phase. 

An alternative method for producing thin deposits consists in avoiding single-step processes by chemisorbing the precursor and then having it decomposed thermally [1]. Such a method, often named atomic layer deposition or gas phase impregnation-deposition, provides very thin deposits due to the presence of a... 

Keywords Atomic layer deposition Thin films Metal alkyl precursors ... 

The fifth contribution by M. Putkonen and L. NiinistO presents an overview of Organometallic Precursors for Atomic Layer Deposition (ALD). The key principle of ALD in contrast to CVD is the exclusion of any gas-phase prereaction allowing the thin film growth to be fully controlled by surface reactions and adsorption/desorption kinetics. ALD is thus ideally suited for the growth of ultra-thin layers and atomically abrupt interfaces needed in future nanoelectronic devices. While CVD and ALD have many aspects in common, precursors suitable for ALD generally need to be much more reactive than those used for CVD. Another challenge is to combine low steric demand with very high selectivity of the surface reactions. 

In earlier work, no molecular structural data were available on mononuclear M amides, but this has changed markedly in the last three (and particularly last two) decades. Another significant development has been the use of the title compounds, and especially the homoleptic dimethylamides M(NMe2)3, as reagents, or synthons for the preparation of bridging binuclear imides 7 (Section 10.3) or cluster imides (e.g. 3 7) (Section 10.4), or Bi[N(SiMe3)2]3 as a precursor for atomic layer deposition.Heteroleptic amidometal chlorides have featured as precursors to cationic metal(III) amides (Section 10.2.4). 

Thin semiconductor films (and other nanostructured materials) are widely used in many applications and, especially, in microelectronics. Current technological trends toward ultimate miniaturization of microelectronic devices require films as thin as less than 5 nm, that is, containing only several atomic layers [1]. Experimental deposition methods have been described in detail in recent reviews [2-7]. Common thin-film deposition techniques are subdivided into two main categories physical deposition and chemical deposition. Physical deposition techniques, such as evaporation, molecular beam epitaxy, or sputtering, involve no chemical surface reactions. In chemical deposition techniques, such as chemical vapor deposition (CVD) and its most important version, atomic layer deposition (ALD), chemical precursors are used to obtain chemical substances or their components deposited on the surface. 

Atomic layer deposition, also known as atomic layer epitaxy (Suntola and Antson, 1977), is a chemical vapor deposition technique capable of producing extremely thin uniform films (Ritala and Leskela, 2001 Leskela and Ritala, 2003). The method differs from conventional chemical vapor deposition in that the precursors, of which there are typically two, are not exposed to the substrate simultaneously. Rather, the first precursor is introduced into the reaction chamber, where it binds to the substrate at complete monolayer coverage a Langmuir... 

Because of the sequential nature of atomic layer deposition, it is a slow method for preparing thin films. The sequential nature, however, also produces a film of uniform thickness, referred to as a conformal film. This is important when the surface being coated is not atomically flat, but rather, has troughs and islands to be coated. Some of the most important technological materials, such as silicon and germanium, have not shown themselves to be amenable to the atomic layer deposition technique. This points to the need for continued research in the field of precursor synthesis. 

Atomic layer deposition (also termed atomic layer epitaxy) a process in which alternate pulses of two volatile precursors are passed over the substrate to promote layer-by-layer film growth... 

This chapter is intended to cover major aspects of the deposition of metals and metal oxides and the growth of nanosized materials from metal enolate precursors. Included are most types of materials which have been deposited by gas-phase processes, such as chemical vapor deposition (CVD) and atomic layer deposition(ALD), or liquid-phase processes, such as spin-coating, electrochemical deposition and sol-gel techniques. Mononuclear main group, transition metal and rare earth metal complexes with diverse /3-diketonate or /3-ketoiminate ligands were used mainly as metal enolate precursors. The controlled decomposition of these compounds lead to a high variety of metal and metal oxide materials such as dense or porous thin films and nanoparticles. Based on special properties (reactivity, transparency, conductivity, magnetism etc.) a large number of applications are mentioned and discussed. Where appropriate, similarities and difference in file decomposition mechanism that are common for certain precursors will be pointed out. 

Many techniques for the preparation of nanosized materials (sol-gel, thermal treatment of polymeric precursor, electrochemical deposition, atomic layer deposition [ALD], etc.) lead to amorphous or low-crystallinity compounds by quenching of a liquid-state local structure or a very disordered state. At a given temperature, two phenomena can be at the origin of the broadening of the Raman spectrum (1) the loss of periodicity because of the large contribution of surface atoms, and (2) a low crystallinity, that is to say, short-range disorder or bond distortion, hi many cases the exact origin is not obvious and a comparison must be made with TEM. ... 

More recently, atomic layer deposition (ALD) has been pnrsned in deep nanostructures by Reijnen (2001) and Meester (2001). Gaseous metal-organic precursors... 

A controlled gas-solid phase reaction of titanium(IV) isopropoxide with silica surface pretreated at 600°C was achieved at between 110 and 180°C in an atomic layer deposition (ALD) reactor. Element determinations and DRIFTS measurements suggested the formation of two isopropoxide ligand containing complex on silica with a titanium density of -1.25 atoms/nm upport- At reaction temperatures exceeding 180°C the growth was no longer determined by the surface. The reaction at 160°C was followed by a calcination treatment at 500°C and the consecutive precursor - oxygen cycles were repeated from one to seven times. 

Atomic layer deposition (ALD, also known e.g. as ALE) is a material depositing technique originally developed for the processing of thin films. The technique is based on alternating selfisaturating gas-solid reactions in which vaporized active metal precursor is brought into contact with the support [1]. 

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