The Physical Electronics Department of SRI International (formerly Stanford Research Institute) has been pioneering the development of devices fabricated to submicron tolerances for well over 20 years. In 1961, a landmark paper on electron-beam lithography and its associated technologies was published by K. R. Shoulderst (then at SRI), which set the stage for our subsequent efforts in this field. He had the foresight to believe that the building of such small devices was actually within the range of human capabilities. As a result of this initial momentum, our experience in the technologies associated with microfabrication has become remarkably comprehensive, despite the relatively small size of our research activity. We have frequently been asked to deliver seminars or provide reviews on various aspects of micro fabrication. These activities made us aware of the need for a comprehensive overview of the physics of microfabrication. We hope that this book will fill that need.