What are the different typical CMOS layers?

-> Substrate

It is a lightly doped p-type semiconductor material upon which devices are fabricated using photolithography.

-> N-/P- Well

These are lightly doped n-type (or) p-type impurities which act as an intermediate substrate for the respective MOS device. These wells are formed by ion-implantation (or) using diffusion techniques.

-> Polysilicon

Widely used as MOS transistor GATE and for local interconnect.

-> N+/P+ Diffusion

It is a process used to dope silicon so to alter its polarity and conductivity. In MOS devices, diffusion is used for the formation of SOURCE and DRAIN.

-> Insulator (SiO2)

Silicon dioxide is used as MOS Gate and metal layer insulator. It has a low k-dielectric to reduce the capacitance.

-> Contact and Vias

Contacts connect the lowest level of metal (say M1) with Poly and diffusion whereas Vias connect all other levels of metal (example M1 and M2).

-> Metal Interconnects

Metal layers are used to interconnect devices. Typically, Copper, Aluminum (or) Copper-Aluminum alloy is used as material for the metal.