Thin Film Layer of material ranging from fractions of nanometer
to several micro meters in thickness Thin Film Process Process to
make thin film on a substrate
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Thermal oxidation Physical Vapor Deposition Vaporized material
bombards onto substrate, i.e. Si wafer. Chemical Vapor Deposition
Gaseous material reacts on substrate to form thin film
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Vacuum deposition Evaporation of material required More
expensive, but high quality Sputtering is widely used Aluminum,
Titanium, Titanium nitrate, Tungsten silicide
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Gas form of material goes under chemical reaction with
substrate to form thin film Remnant gas remains after reaction
Fast, cheap, but poor quality Forms variety of thin film
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Process to make patterns on a wafer Removes unwanted area of
thin film deposited in previous stage
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Key of Photolithography, called PR Type of organic material
Very sensitive to UV
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Two types of photoresist Positive: Exposed PR is removed
Negative: Exposed PR remains
Photoresist is organic material Must be stripped off after
etching
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Sometimes the surface has to be flattened after removing PR
Mechanically polished
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Fabricating nanoscale device is repetition of thin film process
and photolithography Up to 20~30 cycles are repeated Each layer of
semiconductor requires at least 2 photolithography masks
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Extreme UV lithography X-Ray Lithography LIGA(x-ray
lithographie galvanoformung abformtechnik), German acronym which
means x-ray lithography electro- deposition moding LIGA is good in
3D fabrication Photolithography will not be abandoned
