LPCVD, Diffusion and Oxidation
Low Pressure Chemical Vapor Deposition (LPCVD) is a thermal process that deposits various films at low pressure. LPCVD processes include polysilicon, silicon nitride and silicon oxides. Diffusion (sometimes referred to as annealing) is a thermal treatment used to move dopants, or impurities, and make dopants introduced by ion implantation electrically active. Oxidation forms a silicon oxide layer on the wafer’s surface, which acts as an insulating or protective layer over it.
WHAT HAPPENS DURING LPCVD & DIFFUSION?
Diffusion is a high-temperature process that changes the electrical characteristics of layers. It is typically used to electrically activate impurities introduced by ion implantation. It can also be designed to drive dopants deeper into a film layer. Chemical Vapor Deposition (CVD) is a method of depositing materials through a chemical process during which a chemical precursor is delivered at a controlled temperature and pressure.
Performing diffusion in a batch reactor enables manufacturers to accurately control temperature and ambient conditions, simultaneously, for a large number of wafers, thus increasing productivity. CVD provides high purity thin films at high deposition rates. Batch reactors enable CVD for a large number of wafers at the same time.