The CVD of Ceramic Materials Nitrides

The number of oxides is large since most metallic elements form stable compounds with oxygen, either as single or mixed oxides. However, the CVD of many of these materials has yet to be investigated and generally this area of CVD has lagged behind the CVD of other ceramic materials, such as metals, carbides, or nitrides. The CVD of oxides has been slower to develop than other thin-film processes, particularly in optical applications where evaporation. 

Gordon,R. G., Recent Advances in the CVD of Metal Nitrides and Oxides, Proc. of the Conf on MOCVD of Electronic Ceramics, Material Research Soc., Pittsburgh, PA (1994)... 

The carbides and nitrides of vanadium and titanium crystallize in the same face centered cubic (fee) system, and because of the closeness of their cell parameters (Table 15.1) form solid solutions. These ceramic materials exhibit interesting mechanical, thermal, chemical and conductive properties.1,2 Their high melting point, hardness and wide range of composition have therefore attracted considerable attention in the last decade. Moreover, their good abrasion resistance and low friction also make these ceramics attractive for protective coating applications.3-5 Chemical vapor deposition (CVD) is a commonly used technique for the production of such materials. In the conventional thermally activated process, a mixture of gases is used.6-9 In the case of TiC, TiN, VC and VN, this mixture is... 

Numerous ceramics are deposited via chemical vapor deposition. Oxide, carbide, nitride, and boride films can all be produced from gas phase precursors. This section gives details on the production-scale reactions for materials that are widely produced. In addition, a survey of the latest research including novel precursors and chemical reactions is provided. The discussion begins with the mature technologies of silicon dioxide, aluminum oxide, and silicon nitride CVD. Then the focus turns to the deposition of thin films having characteristics that are attractive for future applications in microelectronics, micromachinery, and hard coatings for tools and parts. These materials include aluminum nitride, boron nitride, titanium nitride, titanium dioxide, silicon carbide, and mixed-metal oxides such as those of the perovskite structure and those used as high To superconductors. 

Ceramic films are widely used in the fabrication of semiconductor devices. The two materials that are presently of major interest are silicon dioxide (Si02) and silicon nitride (Si3N4). These are deposited as thin films using CVD. 

AI2O3 is often used to provide a ceramic material in contact with the workpiece or to apply several multilayers of the type Al203/TiN. The thicknesses of the sublayers are on the order of about 1 pm and the total layer thickness is about 10-12 pm. Such a structure is shown in Fig. 29 for the WIDIA grade TNI 50. Most of these layers are deposited by CVD. Also a combination of PVD and CVD ( duplex ) techniques was studied and has yielded better performing layers than other titanium nitride and carbonitride coatings [110]. 

Ceramic materials such as Si3N4 [50] or TiN [51] can be coated with p-BN by plasma-enhanced or sputter chemical vapor deposition (CVD), or diamond coatings (by excited CVD) can be doped with boron upon admixture of B2H6 to the CH4/H2 plasma [52]. See Section 4.1.1.2.3, p. 13, for hard boron nitride coatings. 

There are a number of boron-containing ceramics for which the development of a polymer based synthetic route that would allow the formation of the ceramic in the form of films, fibers, coatings or other shaped materials would be advantageous. Because of its unique physical and chemical properties, boron nitride, BN, is a material of particular interest. A BN unit is isoelectronic with C2 and accordingly, boron nitride can be obtained in forms related to diamond (cubic-BN) and graphite (hexagonal-BN). The c-BN has only been formed under extreme conditions, thus boron nitride materials that have been formed from chemical precursor routes (CVD or polymer) have been obtained in amorphous, turbostratic or hexagonal forms. 

Synthetic routes derived from molecular and non-molecular precursors have expedited the development of technologically important 2- and 3- dimensional materials. Such approaches have often proved superior to conventional ceramic techniques in that high purity bulk samples or thin films can be prepared at lower temperatures much more rapidly. Predominant among the precursor methods are those based on decomposition reactions. These either involve gaseous species, such as those used in chemical vapor deposition (CVD), or solids. Examples include the pyrolysis of the gas-phase precursor [(CH3)2A1(NH2)]3 to produce aluminum nitride (i) and the thermal decomposition of solid state carbonate precursors of calcium and manganese (Cai j,Mn C03, 0 < x < 1) to produce several of the known ternary compounds in the Ca-Mn-O system (2). Single-displacement reactions are also common as precursor methods. These approaches usually involve gas-phase reactions and are also used in CVD techniques. Examples here include the formation oi... 

Ceramic superconducting films are divided into three classes, Bl-type compounds, ternary compounds, and high-temperature oxide superconductors. The Bl-type (NaCl-type structure) compound superconductors consist of nitrides and carbides with 5A, 6A, and 7A transition metals, such as TiN, ZrN, HfN, VN, NbN TaN, MoN, WN, TiC, ZrC, HfC, VC, NbC, TaC, MoC, WC, NbNi tC t, hex-MoN, and hex-MoC. Regarding the thin-film material, it is notable that NbN and NbN] (C ( (x = 0.08 and 0.15) have superconducting critical temperature, T, values of 17.3 and 17.8 K, respectively. The deposition method used is almost always sputtering or CVD. The properties of films deposited by the former method are superior. A highly reliable Josephson device was realized with an NbN film. 

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