Wafer Fab:  Dielectric                                                                  

Aside from the passivation and glass layer deposited over the surface of the die to protect it from mechanical damage and corrosion, dielectric layers are also used for isolating components or structures in the active circuit from each other, and as dielectric structures for MOS transistors, capacitors, and the like.  

Other uses for dielectric layers include: 1) masking for diffusion and ion implant processes; 2) diffusion from doped oxides; 3) overcoating of doped films to prevent dopant loss; 4) gettering of impurities; and 5) mechanical and chemical protection.

Silicon dioxide (SiO2), the oxide of silicon, is the most widely used dielectric in wafer fabrication.  There are many ways to grow  silicon dioxide on the surface of silicon, but it is most often done through a process known as thermal oxidation.  Thermal oxidation consists of exposing the silicon to oxidizing agents such as water and oxygen at elevated temperatures. This process has good control over the thickness and properties of the SiO2 layer.