Photolithography Process
Photoresist
Photoresist is a sensitive material. It is used for temporarily coated on the substrate. Actually, it works to transfer design image on substrate through exposure. It is very similar to the photo sensitive coating on the film for the camera. There are two types of photoresist.
1. Positive Photoresist :
2. Negative Photoresist :
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Negative Photoresist
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Positive Photoresist
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Becomes insoluble after exposure.
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Become soluble after exposure.
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When developed, the unexposed parts dissolved.
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When developed, the exposed parts dissolve.
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Give cheap resolution.
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Give better resolution.
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Photoresist Composition :
1. Polymer
2. Solvents
3.Sensitizers
4. Additives
Polymer :
PR is a solid organic material types. It transfers designed pattern to wafer surface. When UV light exposed PR react with it. For
Positive PR: from insoluble to soluble
Negative PR: from soluble to insoluble
Solvent :
It dissolves polymers into liquid and allows the application of thin PR layers by spinning.
Sensitizer :
It controls or modifies photochemical reaction of resist during exposure. It determines exposure time and intensity.
Additive :
Various added chemical to achieve desired process results, such as dyes to reduce reflection.
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