VLSI masking and photolithography

[Abisheak]

hello everyone

1.Why do we mask the silicon wafer and distinguish the chip into exposed layer and unexposed layer?

2.what is photolithography?
(It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical "photoresist", or simply "resist," on the substrate)
couldnt understand this line.

thank you

 

[amitjagtap]

This process is same as Basic Photo printing....In this we get the photo film (Mask) ...and to mirror the image on photo paper we keep it under light...so that our image get transformed form phto film to paper....

In VLSI....Each Mask represents circuits/device parts on each layer of fabrication......and to fabricate it on silicon we xposre it to UV light....and remove unwanted area in that layer.
GO through CMOS transistor fabrication process....you will get an idea