Microwave-deposition reactor

Microwave-Plasma Deposition. The operating microwave frequency is 2.45 GHz. A typical microwave plasma for diamond deposition has an electron density of approximately 10 electrons/m, and sufficient energy to dissociate hydrogen. A microwave-deposition reactor is shown schematically in Fig. 5.18 of Ch. 5.P ]P°]... 

Deposition Process. A typiceil microwave plasma for diamond deposition has an electron density of approximately 10 electrons/m and sufficient energy to dissociate hydrogen. A microwave-deposition reactor is shown schematically in Fig. 13.2.P M 1 The substrate (typically a silicon wafer) is positioned at the lower end of the plasma. Gases are introduced at the top of the reactor, flow around and react at the substrate, and the gaseous by-products are removed into the exhaust. The substrate must be heated to 800 - 1000°C for diamond to form. This can be done by the interaction with the plasma and microwave power but this is difficult to regulate and, more commonly, the substrate is heated directly by radiant or resistance heaters which provide more accurate temperature control. 

Figure 5.2. Two of the more common types of low pressure CVD reactor, (a) Hot Filament Reactor - these utilise a continually pumped vacuum chamber, while process gases are metered in at carefully controlled rates (typically a total flow rate of a few hundred cubic centimetres per minute). Throttle valves maintain the pressure in the chamber at typically 20-30 torr, while a heater is used to bring the substrate up to a temperature of 700-900°C. The substrate to be coated - e.g. a piece of silicon or molybdenum - sits on the heater, a few millimetres beneath a tungsten filament, which is electrically heated to temperatures in excess of 2200 °C. (b) Microwave Plasma Reactor - in these systems, microwave power is coupled into the process gases via an antenna pointing into the chamber. The size of the chamber is altered by a sliding barrier to achieve maximum microwave power transfer, which results in a ball of hot, ionised gas (a plasma ball) sitting on top of the heated substrate, onto which the diamond film is deposited.

Fig. 4 Schematic layout of a modified microwave CVD reactor for nanocrystalline diamond deposition.

Another illustrative example of the application of FTIR spectroscopy to problems of interest in adhesion science is provided by the work of Taylor and Boerio on plasma polymerized silica-like films as primers for structural adhesive bonding [15]. Mostly these films have been deposited in a microwave reactor using hexamethyldisiloxane (HMDSO) as monomer and oxygen as the carrier gas. Transmission FTIR spectra of HMDSO monomer were characterized by strong... 

Electron Cyclotron Resonance (ECR). A microwave plasma can also be produced by electron cyclotron resonance (ECR) (see Ch. 5, Sec. 9). An ECR-plasma reactor suitable for the deposition of diamond is shown schematically in Fig. 5.19 of Ch. 5.[ °]... 

The experimental set-up normally used is shown schematically in Fig. 8. The gases, various chlorides and oxygen, are supplied with the aid of flow controllers. Typical values of the gas flows Qi are 30 < Qo2 < 500 seem, 2 < QSici4 < 140 seem, and some tens of seem for the other chlorides in use (seem = standard (STP) cubic centimeter per minute). The reactor consists of a microwave cavity and a furnace capable of heating the substrate between room temperature and 1200 °C. The cavity is connected to a 2.45 GHz generator with a maximum power of 200 W. A sorption pump is used to maintain a clean atmosphere within the tube during deposition. The pressure in a typical run is selected between 1.3 10 3 and 2.7 10 2 bar. 

Figure 17 Deposition rate and refractive index for silicon nitride films as a function of microwave power for ECR reactor (after Matsuo26).

From the microwave supported plasma CVD, which is also used to deposit diamond films (Section 6.3.1), a method generating nanodiamond in a flow reactor is derived. The sole modification to obtain single particles is to omit the substrate from the reactor so the diamond particles formed are carried along by the gas current to precipitate only in cooler parts of the apparatus placed downstream after the oven. As carbon source, dichloromethane in a mixture with oxygen is employed. The main product obtained with this method is amorphous, graphitic material. This may, however, quantitatively be removed by a treatment with 70% perchloric... 

Boron-carbon-nitride ceramic is deposited on iron-based sliding parts by chemical vapor deposition (CVD) it is used as rotary compressor shafts, in order to improve the wear resistance [1 to 5]. Such B-C-N coatings have also been applied to dynamic pressure air bearings [6]. In gas-cooled nuclear reactors, °B-enriched B-C-N can be deposited by CVD in the fluid channels of the fuel elements for permanent deactivation in case of an emergency [7]. Radiofrequency or microwave-enhanced CVD is employed in order to deposit a diamond carbon and (3-BN superlattice structure [8]. 

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