Cold wall

The second indication is a faint smoke-like cloudiness in the zone of the tube which is being heated by the Bunsen this is readily visible as the interior of the tube is normally quite clear and bright. This is a later stage of development of the flash-back than the rise of pressure, already mentioned, and should be counteracted by moving the Bunsen immediately to the point of the combustion tube where heating was commenced. In either case the Bunsen should then be moved slowly forwards as before. A flash-back is attended by the deposition of carbon particles, carried back by the explosion wave, on the cold walls of the tube. Care should be taken that these are completely burnt off as the Bunsen is slowly moved forward again. 

QeS total cold wall heat input total required weight of TP system for a given backface temperature (X) AH regions. 

The CVD process is accomplished using either a hot-wall or a cold-wall reactor (Fig. 13). In the former, the whole chamber is heated and thus a large volume of processing gases is heated as well as the substrate. In the latter, the substrate or substrate fixture is heated, often by inductive heating. This heats the gas locally. 

Cold walls, as in coolers or condensers, usually have somewhat decreased corrosion rates for the reason just described. However, in some cases, the decrease in temperature may allow the formation of a more corrosive second phase, thereby increasing corrosion. 

If the cooling bath for the first trap is lowered much below — 15°, plugging of the trap is likely to occur. These traps are connected so that the vapor enters the larger, annular space, impinging on the cold wall before entering (and possibly plugging) the smaller inner tube. 

Radiant asymmetry <10 °C for cold wall < 23°C for warm wall < 14 °C for cold ceiling < 5 °C for warm ceiling PPD < 5% with respect to cold wall, warm wall, cold ceiling, and warm ceiling... 

Convection is the heat transfer in the fluid from or to a surface (Fig. 11.28) or within the fluid itself. Convective heat transport from a solid is combined with a conductive heat transfer in the solid itself. We distinguish between free and forced convection. If the fluid flow is generated internally by density differences (buoyancy forces), the heat transfer is termed free convection. Typical examples are the cold down-draft along a cold wall or the thermal plume upward along a warm vertical surface. Forced convection takes place when fluid movement is produced by applied pressure differences due to external means such as a pump. A typical example is the flow in a duct or a pipe. 

Carbon steel, cold wall as opposed to hot wall. ... 

Stripper shell Carbon steel, cold wall with 4 in. (10 cm) medium weight refractory lining... 

The riser and the reactor can be replaced with a cold-wall design. 

The regenerator is already a cold-wall vessel re-rating is not often practical. High regenerator temperature typically requires installing either catalyst coolers, operating with partial combustion, or injecting a quench stream into the riser. 

Thermal CVD requires high temperature, generally from 800 to 2000°C, which can be generated by resistance heating, high-frequency induction, radiant heating, hot plate heating, or any combination of these. Thermal CVD can be divided into two basic systems known as hot-wall reactor and cold-wall reactor (these can be either horizontal or vertical). 

Cold-Wall Reactors. In a cold-wall reactor, the substrate to be coated is heated directly either by induction or by radiant heating whi 1 e th e rest of the reactor remains cool, or at least cooler. Most CVD reactions are endothermic, i.e., they absorb heat and deposition takes place preferentially on the surfaces where the temperature is the highest, in this case the substrate. The walls of the reactor, which are cooler, remain uncoated. A simple laboratory-type reactor is shown... 

Figure 5.7. Cold-wall laboratory reactor for tungsten deposition.

Another example of a cold-wall reactor is shown in Fig. 5.9. It uses a hot plate and a conveyor belt for continuous operation at atmospheric pressure. Preheating and cooling zones reduce the possibility of thermal shock. The system is used extensively for high-volume production of silicon-dioxide coatings for semiconductor passivation and interlayer dielectrics. 

Figure 5.8. Schematic of cold-wall production reactorfor silicon epitaxy.

Figure 5.9. Continuous operation cold-wall reactor for atmospheric pressure deposition of Si02-...

Figure 5.10. Cold-wall reactor with radiant heating.

Typical Reactor Design. Table 5.1 lists typical CVD production reactors which include cold-wall and hot-wall reactors operating at low or atmospheric pressures. The decision to use a given system should be made after giving due consideration to all the factors of cost, efficiency, production rate, ease of operation, and quality. 

BPSG(boro-phopho- passivation of cold wall ca. 1 Torr... 

An RF plasma is generated at a frequency of 13.56 MHz. A typical equipment consists ofparallel electrodes as shown inFig. 5.20. It is a cold-wall design which is used extensively forthe deposition of silicon nitride and silicon dioxide for semiconductor applications. 

Naiijj Na apor exists. Above this T, the sodium pressure is no longer sufficient to prevent the thermal dissociation of NaB, and syntheses lead to a second phase with a lower Na content, Na Bu. However, Na,(B 5 can be prepared at < 1100°C, as long as the sodium pressure in the vapor phase is kept low by having a cold wall in the reactor or, e.g., by substituting a Na-K alloy for sodium. ... 

Jarosinski, J., Flame quenching by a cold wall, Combust. Flame, 50 167,1983. 

HfCl2[N(SiMe3)2]2 was synthesized with the reaction of anhydrous HflCU and Na[N(SiMe3)] in toluene [5]. The films were grown in a cold-wall flow-type ALD reactor on (100) oriented p-Si substrates in the temperature range of 150-400 °C. Prior to deposition. Si substrate was etched in dilute HF solution to remove the native oxide and then rinsed in deionized water. The pressure in the reactor was fixed at about 0.5 torr. Argon (99.99995%) was used as a... 

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