TABLE OF CONTENTS "You can't see it, but it's everywhere you go."
Bridget Booher, journalist, on silicon
If we view micromachining technology as a set of generic tools, then there is no reason to limit its use to one material. Indeed, micromachining has been demonstrated using silicon, glass, ceramics, polymers, and compound semiconductors made of group III and V elements, as well as a variety of metals including titanium and tungsten. Silicon, however, remains the material of choice for microelectromechanical systems. Unquestionably, this popularity arises from the large momentum of the electronic integrated circuit industry and the derived economic benefits, not least of which is the extensive industrial infrastructure. The object of this chapter is to present the properties of silicon and several other materials, while emphasizing that the final choice of materials is determined by the type of application and economics.
The silicon-compatible material system encompasses, in addition to silicon itself, a host of materials commonly used in the semiconductor integrated circuit industry. Normally deposited as thin films, they include silicon oxides, silicon nitrides, and silicon carbides, metals such as aluminum, titanium, tungsten, and copper, and polymers such as photoresist and polyimide.
Silicon is one of very few materials that is economically manufactured in single-crystal substrates. This crystalline nature provides significant electrical and mechanical advantages. The precise modulation of silicon's electrical conductivity using impurity doping lies at the very core of the operation of electronic semiconductor devices. Mechanically, silicon is an elastic and robust material whose...
