Atomic Layer Deposition in MEMS Technology

Atomic layer deposition can be defined as a film deposition technique that is based on the sequential use of self-terminating gas-solid reactions. ALD can offer significant advantages in MEMS processing compared to traditional film deposition methods. This chapter describes atomic layer deposition and its different processes and applications. It also explains the basic operation principles of the ALD technique and briefly introduces the already developed ALD materials and processes. ALD is a cyclic process based on repeated reaction cycles that consist of self-terminating reaction steps followed by a purge or evacuation step. The operation principle based on separate, self-terminating reactions, which means that means that the reactions continue as long as there are suitable reactive sites on the substrates. There are two main limitations of ALD, which are the slowness of the process and the limited material and process selection. This chapter helps us to get some idea on the ALD processes. This is detailed with the help of headings such as general requirements for the reactants, metal reactants, nonmetal reactants, materials made by ALD, multi-element films by ALD etc. This chapter is explains in detail the characteristics of ALD processes and films. It gives some idea on the growth modes possible in ALD. The demerits like roughness of ALD films, stress and pinholes of ALD films are explained. The stability of ALD films in different chemical environments are also briefed in this chapter. ALD reactors, which is used to create conditions of LAD processes are detailed in this chapter.