Semiconductor fabrication Chemical Vapor Deposition

Deposition of Thin Films. Laser photochemical deposition has been extensively studied, especially with respect to fabrication of microelectronic stmctures (see Integrated circuits). This procedure could be used in integrated circuit fabrication for the direct generation of patterns. Laser-aided chemical vapor deposition, which can be used to deposit layers of semiconductors, metals, and insulators, could define the circuit features. The deposits can have dimensions in the micrometer regime and they can be produced in specific patterns. Laser chemical vapor deposition can use either of two approaches. 

This article focuses primarily on the properties of the most extensively studied III—V and II—VI compound semiconductors and is presented in five sections (/) a brief summary of the physical (mechanical and electrical) properties of the 2incblende cubic semiconductors (2) a description of the metal organic chemical vapor deposition (MOCVD) process. MOCVD is the preferred technology for the commercial growth of most heteroepitaxial semiconductor material (J) the physics and (4) apphcations of electronic and photonic devices and (5) the fabrication process technology in use to create both electronic and photonic devices and circuits. 

Chemical vapor deposition (CVD) has grown very rapidly in the last twenty years and applications of this fabrication process are now key elements in many industrial products, such as semiconductors, optoelectronics, optics, cutting tools, refractory fibers, filters and many others. CVD is no longer a laboratory curiosity but a maj or technology on par with other maj or technological disciplines such as electrodeposition, powder metallurgy, or conventional ceramic processing. 

Chemical vapor deposition is a key process in microelectronics fabrication for the deposition of thin films of metals, semiconductors, and insulators on solid substrates. As the name indicates, chemically reacting gases are used to synthesize the thin solid films. The use of gases distinguishes chemical vapor deposition (CVD) from physical deposition processes such as sputtering and evaporation and imparts versatility to the deposition technique. 

MEMS (microelectromechanical systems) are systems with small device sizes of 1-100 pm. They are typically driven by electrical signals. To fabricate such systems materials like semiconductors, metals, and polymers are commonly used. MEMS technology fabrication is very cost-efficient. The structures are transferred by processes, which are applied to many systems on one substrate or even many of them simultaneously. The most important fabrication processes are physical vapor deposition (PVD), chemical vapor deposition (CVD), lithography, wet chemical etching, and dry etching. Typical examples for MEMS are pressure, acceleration, and gyro sensors [28,29], DLPs [30], ink jets [31], compasses [32], and also (bio)medical devices. 

Ceramic and semiconductor thin films have been prepared by a number of methods including chemical vapor deposition (CVD), spray-coating, and sol-gel techniques. In the present work, the sol-gel method was chosen to prepare uniform, thin films of titanium oxides on palladium Titanium oxide was chosen because of its versatility as a support material and also because the sol-gel synthesis of titania films has been clearly described by Takahashi and co-workers (22). The procedure utilized herein follows the work of Takahashi, but is modified to take advantage of the hydrogen permeability of the palladium substrate. Our objective was to develop a reliable procedure for the fabrication of thin titania films on palladium, and then to evaluate the performance of the resulting metalloceramic membranes for hydrogen transport and ethylene hydrogenation for comparison to the pure palladium membrane results. 

One sign of progress is the extent to which sophisticated research on transport phenomena, particularly mass transfer, has penetrated several other fields, including those described in later papers of this volume. Examples include fundamental work on the mechanics of trickle beds [17] within reactor engineering studies of dispersion in laminar flows [18] in the context of separations important to biotechnology coupling between fluid flows and mass transfer in chemical vapor deposition processes for fabrication of semiconductor devices [19] and optical fiber preforms [20] and the simulation of flows in mixers, extruders, and other unit operations for processing polymers. 

Armelao et al. (2005) fabricated LaCoOs thin films by the combination of chemical vapor deposition (CVD) and sol-gel methods. Two sequences were adopted to prepare the target film (i) sol-gel of Co-O on CVD La-O (ii) CVD of Co-O on sol-gel La-O. Losurdo et al. (2005) further investigated the spectroscopic properties of these films by ellipsometry in the near-IR and UV range. The former film has a larger crystallite size, a lower refractive index, and a higher extinction coefficient. It also presents a semiconductor-to-metal transition at a temperature of 530 K. Contrarily, the latter film has a smaller crystallite size, a higher refractive index, a lower extinction coefficient and a semiconductor behavior. 

With a view to improving device performance, Kirwan and co-workers proposed the polysilicon self-aligned gate process in 1969. This process not only improved device reliability, it also reduced parasitic capacitances. Furthermore, in 1969, the metal-organic chemical vapor deposition (MOCVD) process was developed hy Manasevit and Simpson, which found widespread adoption in the fabrication of compound semiconductors such as GaAs. 

Inside processes such as modified chemical vapor deposition (MCVD) had a different origin. Chemical vapor deposition (CVD) had long been used In the electronics industry for fabrication of silicon devices and was adapted to produce silica layers inside substrate tubes [18j. In CVD, the concentration of reactants is very low to inhibit gas phase reaction in favor of a heterogeneous wall reaction which produced a vitreous, particle-free deposit on the substrate. This is fine for the 1000 A films required for semiconductor processing, but fails to produce thick deposits required for fiber. CVD was therefore reversed, the reactant concentration was increased and large volumes of particles were produced inside the silica substrate tube. They deposited on the tube wall and were sintered to glass. 

Amorphous SiC (a-SiC) thin films can be deposited at a low temperature (e.g., 400 °C) using a plasma-enhanced chemical vapor deposition process, and have excellent chemical and temperature resistance like their crystalline counterparts. These characteristics make them suitable as etch masking layers during advanced semiconductor, solar cell, and MEMS fabrication. Although the rates of crystalline and a-SiC are expected to differ significandy, an understanding of the polish mechanisms of a-SiC slurries will help designing slurries for crystalline SiC as wed. 

Chemical vapor deposition (CVD) is a process by which reactive molecules in the gas phase are transported to a surface at which they chemically react and form a solid film. It is a well-established technique that can be used to deposit all classes of materials, including metals, ceramics, and semiconductors, for a variety of applications. Large areas can be coated and the process is amenable to mass production. Thick films or even monolithic bodies can also be produced by basically prolonging the deposition process so that the desired thickness is achieved. Table 1.3 shows some of the important reactions used for the fabrication of ceramics together with the temperature range of the reactions and the applications of the fabricated articles. 

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