Fabrication of NMOS transistor:-

Diffusion Mask -

The first modification of the device wafers was the application of an oxide layer to serve as a diffusion mask. The target thickness of this mask was 8000 Angstroms and the goal was to make it as uniform and contain as little impurities as possible. The thickness and purity of the layer is affected by many external conditions.

Doping Active Regions -

The device wafers are doped with boron (B155). Once the B155 is coated on all the wafers, they are placed into the furnace at approximately 1000°C for 90 minutes to diffuse the dopant into the wafer. A representation of this can be shown below -

Field Oxide and Gate Oxide -

The field oxide is prepared by wet oxidation process. The target field oxide thickness is 5000 Angstroms. After the field oxide is applied, the gate oxide is taken. The thickness of gate oxide is 500 Angstroms.

Mask Layout of PMOS Transistor:-