Fundamentals of Vacuum and Plasma Technology
Vacuum is required for achieving high-purity conditions during a process and also for reducing molecular scattering. Therefore, an understanding of vacuum chambers, vacuum pumps, and their principles becomes imperative for anyone working with device fabrication and process development. A vacuum system consists of a vacuum chamber, vacuum pumps, connecting hoses, vacuum measuring devices, and other accessories. The chapter examines the principles of vacuum creation and the factors that influence the lowest pressure that can be achieved in a practical system. The turbo molecular pump is an example of a high-vacuum pump. Unlike the roughing pump, the pumping speed here is fairly constant through most of its operating pressure range. Plasmas have many desirable properties in semiconductor device fabrication. While RF and DC excitations are the most commonly used methods, other excitation techniques can also be found in many semiconductor processes. RF excitation also requires an impedance matching network to maximize the power delivered to the plasma.