China
Africa
Explore chapters and articles related to this topic
Fundamentals of MEMS Fabrication
Published in Sergey Edward Lyshevski, Mems and Nems, 2018
Atmospheric pressure and low pressure chemical vapor deposition (APCVD and LPCVD) are used to deposit metals, alloys, dielectrics, silicon, polysilicon and other semiconductor, conductor and insulator materials and compounds. The chemical reactants for the desired thin film are introduced into the CVD chamber in the vapor phase. The reactant gases then pyrochemically react at the heated surface of the wafer to form the desired thin film. Epitaxial growth, as the CVD process, allows one to grow a single crystalline layer upon a single crystalline substrate. Homoepitaxy is the growth of the same type of material on the substrate (e.g., p+ silicon etch-stop-layer on an n-type substrate for a layer formation). Heteroepitaxy is the growth of one materials on a substrate which is a different type of medium. Silicon homoepitaxy is used in bulk micromachining to form the etch-stop-layers. Plasma enhanced chemical vapor deposition (PECVD) uses a RF induced plasma to provide additional energy to the reaction. The major advantage of PECVD is that it allows one to deposit thin films at lower temperatures compared with conventional CVD.
Low-Temperature Plasma-Enhanced Chemical Vapor Deposition of Silica-Based Membranes
Published in Stephen Gray, Toshinori Tsuru, Yoram Cohen, Woei-Jye Lau, Advanced Materials for Membrane Fabrication and Modification, 2018
Hiroki Nagasawa, Toshinori Tsuru
One promising solution for reducing the fabrication temperature is the plasma-enhanced chemical vapor deposition (PECVD) technique. PECVD is one of the commonly used techniques for thin-film deposition, which involves a series of gas phase and surface reactions of volatile precursors induced by plasma discharge. PECVD has been utilized for many different applications. For example, deposition of silicon-based thin films such as silica, silicon nitride, and silicon carbonitride for microelectronics (Maex et al., 2003; Volkesen et al., 2010) and optical devices (Martinu and Poitras, 2000) is a major application of PECVD. An important advantage of PECVD is that the processing temperature can be greatly reduced compared to that in conventional CVD and sol-gel processing (Barranco et al., 2004). Thin films can be deposited even at room temperature, so deposition can be performed onto thermally sensitive substrates. Moreover, because of the high reactivity of chemical species in plasma discharges, the films deposited by PECVD usually have a highly cross-linked structure with strong adhesion on various substrates. These features of PECVD could enable the fabrication of high-performance silica-based membranes on various types of substrates.
Optical MEMS: An introduction
Published in Guangya Zhou, Chengkuo Lee, Optical MEMS, Nanophotonics, and Their Applications, 2017
The chemical vapor deposition (CVD) process also takes place in a chamber where the substrates are placed in a holder. Reactive gases are introduced into the chamber and form a thin film on the substrate surface. The produced by-product then exits the chamber. Due to this film-forming mechanism, both the reactive chemicals and the by-product in the CVD process need to be volatile while creating a non-volatile solid film. The energy for the reaction is supplied by thermal methods, photons, or electrons. The advantage of CVD over PVD is its high deposition rate and good step coverage. CVD can be conducted in atmospheric pressure and in reduced pressures. However, a lower chamber pressure allows better control in the deposition rate while also reducing the contamination. Figure 1.4a illustrates low-pressure CVD (LPCVD) which is operated in reduced pressure and allows for batch processing. The heater around the chamber provides the thermal energy for the chemical reaction. Plasma can also be an energy source for the chemical reaction. This system is called plasma-enhanced CVD (PECVD) as illustrated in Figure 1.4b. The gases in the chamber are highly reactive due to the plasma created by the applied bias. This allows for film formation on the substrates placed in the chamber. PECVD allows for film deposition with a high rate but at lower temperatures compared to LPCVD.
A comprehensive review on the synthesis and photothermal cancer therapy of titanium nitride nanostructures
Published in Inorganic and Nano-Metal Chemistry, 2023
Ikhazuagbe H. Ifijen, Muniratu Maliki
The deposition of the target product can be accomplished by: 1) Plasma enhanced chemical vapor deposition (PECVD).[73] 2) Thermally active chemical vapor deposition (TACVD)[73,74] and 3) Photoinitiated chemical vapor deposition (PICVD). Thermally activated chemical vapor deposition is not appropriate for substrates that are sensitive to temperatures like polymers.[75,76] Plasma enhanced chemical vapor deposition technique has scale-up problems due to distinct operational conditions.[77] The low energy remedies and a broad range of potential variations emerge for the photo-initiated methods as photoinitiated chemical vapor deposition.[78] Furthermore, the photo-initiated procedure does not need technological tools in ambient temperature and pressure situations.[79] Plasma is developed in the vacuum compartment and deposited as a thin film on the surface of the substrate by the chemical reactions of reacting gases during the plasma-enhanced chemical vapor deposition strategy. Inductive coupling (electric current) electromagnetic induced electric current and radiofrequency (AC frequency) microwave are also employed in this approach. It can be operated comparatively at a lower temperature so it is useful for wide-scale industrial utilization and the assembly of nanotubes and graphene nanostructure.[80]
PECVD process parameter optimization: towards increased hardness of diamond-like carbon thin films
Published in Materials and Manufacturing Processes, 2018
Ranjan Kumar Ghadai, Kanak Kalita, Subhas Chandra Mondal, Bibhu Prasad Swain
Plasma enhanced chemical vapor deposition (PECVD) is used for deposition of DLC thin film coatings. The p-type Si (100) with resistivity 1–10 Ω-cm are used for DLC deposition. The Si-substrates are firstly cleaned in 2% HF solution for 2 minutes to remove oxide layer, followed by ultrasonically cleaning in deionized water for 10 minutes. As shown in Table 1, Argon-C2H2 flow rate, Hydrogen flow rate and deposition temperature are considered as input parameters for the optimization of hardness. Scanning electron microscope (JSM-5510) of JEOL make is used for microstructural characterization of DLC thin films. Nano-hardness tester (NHTX-55–0019) of CSM Instruments make is used for carrying out the Nano-indentations (Fig. 1). A 20 μm radius of curvature Berkovich diamond indenting tip (B-I 93) is used. The maximum indentation load is considered as 10 mN at three different locations the indentations over the sample and their average number is reported. The Oliver–Pharr method [16,17] is used for hardness calculation. The Raman spectroscopy of the thin films are characterized by Horiba JobinYvon at room temperature using the 488 nm line of an Ar+ laser as an excitation source. Innova SPM atomic force microscope is used for the morphological analysis of DLC thin films.