Plasma deposition system

The experimental set-up is a vacuum unit for pulsed deposition of carbon film from carbon-based plasmas at a plasma density of lO to 10 cm , ionization rate of about 95% and pulse frequency varied from 1 to 30 Hz. The pulse duration was 100 ps. Figure 11.3 schematically illustrates the plasma deposition system [10]. The system consists of a high purity graphite cathode (1), anode (2), ignition electrodes (3,4) with dielectric separator (5), second anode of auxiliary discharge (6) and substrate holder (7). The capacitors Ci and C2 are connected to a power supply unit with... 

I n addition to microwave deposition, another common plasma deposition system for diamond coatings is based on plasma-arc. Plasma-arc deposition is usually obtained in a high-intensity, low-frequency arc, generated between two electrodes by either direct or eiltemating current. The process requires a large amount of power and the equipment is costly.P l... 

DC Plasma System. Typical direct-current (DC) plasma deposition systems are shown schematically in Fig. Electrodes usually... 

Fig. 3.5 Schematic diagram of (a) coaxial pulsed arc plasma deposition system and (b) quasi-stationary model of a generated arc plasma, /is the arc current, B is the magnetic field induced by /, and F is the electromagnetic force applied to the plasma ions and electrons. (Reprinted with permission from ref. [34]. 2000 Elsevier Science S.A.) (c) Used cathode cylinder made of palladium. The plasma is generated from the circular rim on the right side, (d) A generated arc plasma. The plasma beam accelerates towards bottom of the image. (Courtesy of Ulvac-Riko, Inc.)...

Dielectric Deposition Systems. The most common techniques used for dielectric deposition include chemical vapor deposition (CVD), sputtering, and spin-on films. In a CVD system thermal or plasma energy is used to decompose source molecules on the semiconductor surface (189). In plasma-enhanced CVD (PECVD), typical source gases include silane, SiH, and nitrous oxide, N2O, for deposition of siUcon nitride. The most common CVD films used are siUcon dioxide, siUcon nitride, and siUcon oxynitrides. 

Fig. 1. Vacuum deposition system having a plasma processing capabiHty, where the dashed lines represent optional additions to a system.

A similar deposition system uses a plasma which is produced by a traveling microwave cavity. No other source of heat is required. The deposition system is shown schematically in Fig. 16.12. The reactants are the same as in the thermal CVD process. Pressure is maintained at approximately 1 Torr. In this case, the deposition occurs at lower temperature, no soot is formed and a compact glass is produced directly. A main advantage of this method is the more accurate grading of the refractive index of the cladding material. 

The plasma-catalyst system utilizes plasma to oxidize NO to NO2 which then reacts with a suitable reductant over a catalyst however, this plasma-assisted catalytic technology still comprises challenging tasks to resolve the formation of toxic by-products and the catalyst deactivation due to the deposition of organic products during the course of the reaction as well as to prepare cost effective and durable on-board plasma devices [47]. 

FIG. 5. Schematic representation of the ASTER deposition system. Indicated are (I) load lock. (2) plasma reactor for intrinsic layers. (3) plasma reactor for />-type layers. (4) plasma reactor for t -type layers, (5) metal-evaporation chamber (see text). (6) central transport chamber. (7) robot arm. (8) reaction chamber, (9) gate valve, (10) gas supply. (11) bypass. (12) measuring devices, and (13) tur-bomolecular pump. 

Luft and Tsuo have presented a qualitative summary of the effects of various plasma parameters on the properties of the deposited a-Si H [6]. These generalized trends are very useful in designing deposition systems. It should be borne in mind, however, that for each individual deposition system the optimum conditions for obtaining device quality material have to be determined by empirical fine tuning. The most important external controls that are available for tuning the deposition processs are the power (or power density), the total pressure, the gas flow(s), and the substrate temperature. In the following the effects of each parameter on material properties will be discussed. 

A systematic study of the role of the ions in the deposition process and their influence on the quality of the layers has been performed by Hamers et al. [163, 301, 332] in the ASTER deposition system. More specifically, a study has been made on the relation between the plasma parameters and the material properties in both the a- and the y -regime at typical deposition conditions. Here, the... 

In the ASTER deposition system, experiments have been carried out in which the excitation frequency was varied between 13.56 and 65 MHz [169]. The other process conditions were kept constant at a power of 10 W, a pressure of 0.16 mbar, gas flows of 30 seem SiHa and 30 seem H2, and a substrate temperature of 250°C. As in Section 1.6.2.3, plasma properties that are deduced from lED measurements are compared with material properties in Figure 63. The lEDs of SiH at four frequencies are shown in Figure 64. 

The plasma potential is about 25 V (Figure 63a). This value of the plasma potential is typical for the silane plasmas in the asymmetric capacitively coupled RF reactors as used in the ASTER deposition system, and is also commonly found in argon or hydrogen plasmas [170, 280, 327]. From the considerable decrease of the dc self-bias with increasing frequency (Figure 63a) it is inferred that the... 

Figure 3.1. Multichamber deposition system for organic light emitting diodes (S sample, RF 02 plasma generator, P vacuum pump, Sh shutter, Q quartz microbalance, C crucibles, M mask for electrode patterning, T tungsten wires for metal deposition).

Nanocarbon emitters behave like variants of carbon nanotube emitters. The nanocarbons can be made by a range of techniques. Often this is a form of plasma deposition which is forming nanocrystalline diamond with very small grain sizes. Or it can be deposition on pyrolytic carbon or DLC run on the borderline of forming diamond grains. A third way is to run a vacuum arc system with ballast gas so that it deposits a porous sp2 rich material. In each case, the material has a moderate to high fraction of sp2 carbon, but is structurally very inhomogeneous [29]. The material is moderately conductive. The result is that the field emission is determined by the field enhancement distribution, and not by the sp2/sp3 ratio. The enhancement distribution is broad due to the disorder, so that it follows the Nilsson model [26] of emission site distributions. The disorder on nanocarbons makes the distribution broader. Effectively, this means that emission site density tends to be lower than for a CNT array, and is less controllable. Thus, while it is lower cost to produce nanocarbon films, they tend to have lower performance. 

Cold-rolled steel panels were purchased from Advanced Coating Technologies, Inc. (Hillsdale, Michigan). Silane chemicals (methylsilane, trimethylsilane, and tetramethylsilane) were purchased from Petrarch Systems, Inc. The silane plasma-deposited steel was then dip-coated with a polymer film 10-25 pim thick. The polymer coating resins used were silane-modified polymers with functionalities such as hydroxyl, acrylate, or amine. 

Like CVD units, plasma etching and deposition systems are simply chemical reactors. Therefore, flow rates and flow patterns of reactant vapors, along with substrate or film temperature, must be precisely controlled to achieve uniform etching and deposition. The prediction of etch and deposition rates and uniformity require a detailed understanding of thermodynamics, kinetics, fluid flow, and mass-transport phenomena for the appropriate reactions and reactor designs. 

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