Physical and Chemical Vapor Deposition
This chapter discusses the techniques used for making thin films. The techniques can be broadly classified into physical vapor deposition (PVD) and chemical vapor deposition (CVD). Within each of these categories, there are several different techniques and subcategories. In PVD, a solid source material is vaporized atom by atom, or molecule by molecule, and deposited on the substrate at a controlled rate. Sputter removal can be considered a sublimation process because the solid is turned directly to a vapor without melting. Co-sputtering is the process of sputtering different target materials from different cathodes such that they deposit on the substrate at the same time. The high temperature and conformal nature of the deposition makes low-pressure CVD ideal for making dense pinhole-free thin films. The deposition process itself introduces stresses in a film. For example, in sputter deposition the high energy of the incident species will compact the film into a compressed state.