Author: Ali Kosari Mehr
In this article, the broad classification of thin-film processes and methods is introduced. By and large, the deposition processes are divided into physical processes (i.e., physical vapor deposition) and chemical processes (chemical vapor deposition and chemical solvent deposition). Here, the processes of physical vapor deposition (CVD) and chemical vapor deposition (PVD) are presented.
Mainly, the deposition processes in which particles of materials reach a vapor phase and then deposit on the substrate as a condensed thin film are called physical vapor deposition. Accordingly, these processes are categorized into two general methods of sputtering and thermal processes; thermal processes are also classified as follows:
These processes are characterized by two major steps: First, a volatile compound to be deposited reaches a vapor phase. Second, the vaporized compound decomposes into atoms and molecules in the presence of heat sources and reacts with other gases, vapors, and liquids in the vicinity of the substrate, culminating in the formation of thin films.
In this connection, most of the CVD processes operate in the pressure range of a few Torr to a pressure higher than the atmospheric pressure of the reactants. Furthermore, a high temperature – about 1000°C – is required for these processes; there are some modified CVD processes requiring a lower operating temperature such as plasma-enhanced chemical vapor deposition (PECVD)/ plasma-assisted chemical vapor deposition (PACVD). Generally, CVD processes are sorted into three types:
In the following articles, it will be attempted to briefly present the operating procedure of each deposition method.