Basic fabrication steps of P-N junction

1. BASIC FABRICATION
STEPS
a) Oxidation
b) Lithography
c) Diffusion and ion implantation
d) Metallization

2. Description
1) Oxidation:
The development of high quality silicon dioxide(SiO2) has helped to establish the
dominance of Si in the production of commercial ICs .Generally silicon dioxide
functions as an insulator
In a number of device structures or as a
Barrier to diffusion or implantation in device
fabrication. In fabrication of p-n junction the
SiO2 film is used to define the junction area.
There are two Sio2 growth methods,dry and
wet oxidation.
Fig:silicon Dioxide

3. 2) Lithography
Another technology called photolithography is used to define the geometry
of the P-N junction.After the formation of SiO2 wafer it is coted with an ultraviolet
light sensitive material called photoresist.Which is spun on the surface of the wafer
with a high speed spinner.

4. 3)Diffusion and Ion implantation
In the diffusion process the semiconductor surface not protected by the oxide is
exposed to a source with a high concentration of opposite type impurity.the
impurity moves to the surface of the semiconductor crystal by solid state diffusion.
In the Ion implantation method ,the intended impurity is introduced into the
semiconductor by accelerating the impurity ions to a high energy level.

5. 4) Metallization
After the Ion implantation process the mettalization process is continued toi form
Ohmic contacts and interconnections.Metal film can be formed vby physical
vapour deposition and chemical vapour deposition.with the completion of the
metallization the P-N junction becomes functional.