Production CVD reactors

Figure 5.6. Production CVD reactor for the coating of cutting tools.

In Chapters 1 and 2, we not only covered the basics of thermal and plasma-enhanced CVD, but we described the general reactor configurations that researchers have explored over the years. From these concepts have come a few production CVD reactors that satisfy the commercial needs of the integrated circuit manufacturing process. 

One way to achieve high wafer throughput is to pack many wafers into each reactor load. This is what is referred to as a "batch" system. It is for this reason that most production CVD reactors today operate as batch systems. One alternative is to operate a single-wafer system, but do it in a continuous... 

Experiments of propane pyrolysis were carried out using a thin tubular CVD reactor as shown in Fig. 1 [4]. The inner diameter and heating length of the tube were 4.8 mm and 30 cm, respectively. Temperature was around 1000°C. Propane pressure was 0.1-6.7 kPa. Total pressure was 6.7 kPa. Helium was used as carrier gas. The product gas was analyzed by gas chromatography and the carbon deposition rate was calculated from the film thickness measured by electron microscopy. The effects of the residence time and the temperature... 

Features common to all CVD reactors include source evaporators with an associated gas handling system to control input gases and gas-phase precursor concentrations, a reactor cell with a susceptor heated by either radio frequency or infrared radiation, and an exhaust system to remove waste products (which may include a vacuum pump for low-pressure operations). Substrate temperatures can vary from less than 200 °C to temperatures in excess of 1000 °C, depending on the nature of the material layer and precursor used. Schematic diagrams of some simple CVD reactors are shown in Figure 4. 

The balance over the ith species (equation IV. 5) consists of contributions from diffusion, convection, and loss or production of the species in ng gas-phase reactions. The diffusion flux combines ordinary (concentration) and thermal diffusions according to the multicomponent diffusion equation (IV. 6) for an isobaric, ideal gas. Variations in the pressure induced by fluid mechanical forces are negligible in most CVD reactors therefore, pressure diffusion effects need not be considered. Forced diffusion of ions in an electrical field is important in plasma-enhanced CVD, as discussed by Hess and Graves (Chapter 8). 

In this section we will review the various types of CVD reactors scientists and engineers have used for the development of thermal CVD processes. This will be distinct from the commercial reactors used for production which will be covered in a later chapter. A similar review of reactors for development of plasma-enhanced CVD processes will be made at the end of the next chapter. We will cover the so-called cold wall systems for either single or multiple wafers first, followed by a discussion of continuous belt systems. Finally, we will review the hot wall reactor approach. 

In reality, these are only two of many arrangements that could be devised to create and deliver to a substrate large quantities of reactive species using a plasma. Since there are many shortcomings to existing commercial plasma-enhanced CVD reactors, it will be useful to explore other reactor concepts that are under development, but have yet to be widely developed commercially. Whether or not they will lead to practical production systems remains to be seen. 

The gaseous by-products from a CVD reactor can often have unpleasant... 

There are various types of CVD reactors for diamond film synthesis, and they are presented in this chapter. A recent advent of production-type CVD reactors is revolutionary changing diamond film from research to production phase. In reading the articles of CVD diamond, it shonld be noted that in some reactors, the substrate temperature cannot be controlled independently of other parameters. The gas presssure P, the microwave power Pj and other parameters influence Ts, and thus the plasma condition is concurrently changed. Therefore, a meticulous care is necessary to see whether the results intrinsically arise from T, or from the plasma condition due to the change in other parameters, when one interprets experimental data. 

Nanopowders have been of particular interest in recent years as they can be used to make high-performance products due to their superior properties. Manufacturing of these powders is therefore important. Such a system using a laser-induced cold-wall CVD reactor is shown in Figure 3.28. It mainly consists of five parts a reactor with two reaction zones, an oven for vaporising hexamethyl disilylamine (HMDS-... 

At the basic level CVD reactors fall into two classifications—open and closed reactor systems. In the closed CVD system the precursors are loaded into the CVD chamber together with the specimens to be treated. The system is then closed and the temperature increased to initiate the chemical process. The process continues for a time sufficient to produce the required effect. The temperature is then reduced to ambient so that the reactor may be opened and the specimens removed. This reactor design is frequently used for the purification of metals and chromizing parts. The dominant type of CVD reactor is the open type. Flowing precursors continuously enter this reactor and the gaseous by-products of the chemical process are continuously removed from the reactor (usually with a vacuum pump) and appropriately treated for discharge into the environment. 

Figure 1-1. Four regions of vapor reactivity within a CVD reactor. Only location 4 contributes to productive film growth. (1) In the vapor phase, homogenous, in the region of the substrate (2) in the vapor phase, homogenous, not in the region of the substrate (3) at a vapor/solid interface, heterogenous, not on the substrate however, on the reactor wall or other comparable surface (4) at a vapor/solid interface, heterogenous, on the substrate.

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