Specific Process Knowledge/Lithography/SU-8: Difference between revisions
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SU-8 resist is designed to produce low defect coatings over a very broad range of films thickness. | SU-8 resist is designed to produce low defect coatings over a very broad range of films thickness. | ||
Spin Coater: RCD8 is dedicated to spin all SU-8 resist formulations, but Spin Coater: Manual All Resist can also be used. | |||
To keep clean room safe and odor free during the spinning please follow the following simple rules: | To keep clean room safe and odor free during the spinning please follow the following simple rules: | ||
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** spread cycle 500rpm, 100rpm/s, 5 sec following by | ** spread cycle 500rpm, 100rpm/s, 5 sec following by | ||
** thickness definition cycle with the final spin speed | ** thickness definition cycle with the final spin speed | ||
** layer uniformity of the thick films can be improved by using a rotation cover(Gyrset), but remember the speed limitation 3000rpm. | ** layer uniformity of the thick films can be improved by using a rotation cover (Gyrset), but remember the speed limitation 3000rpm. | ||
* For SU-8 layers thinner then 10um the spread cycle can be omitted to improve the uniformity of the films. | * For SU-8 layers thinner then 10um the spread cycle can be omitted to improve the uniformity of the films. | ||
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[[media:Spinning_curves.xls|Spinning curves for SU-8 2002 and 2005.]] | [[media:Spinning_curves.xls|Spinning curves for SU-8 2002 and 2005.]] | ||
* A rotation cover (Gyrset) can be also used in case you will spin less | * A rotation cover (Gyrset) can be also used in case you will spin less than 1um resit | ||
** 3000rpm, 300rpm/s, 30sec with gyrset gives appx. 850nm with SU-8 2002 (the test done by Thomas Buss from Nanotech). | ** 3000rpm, 300rpm/s, 30sec with gyrset gives appx. 850nm with SU-8 2002 (the test done by Thomas Buss from Nanotech). | ||
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==Exposure== | ==Exposure== | ||
The exposure step is usually done in near UV-radiation at aligners system which | The exposure step is usually done in near UV-radiation at aligners system which blocks the wavelengths below the i-line (365nm wavelength). | ||
Duration of the UV-exposure depends of resist thickness, but notice that if the UV exposure becomes long then the heating at the interface with the mask can cause formation of hard skin at the surface of SU-8 so called T-topping phenomena. The the main rule is if the dose of the exposure exceeds 250-300 mJ/cm2 it is recommended to do a multiple exposure instead and have a waiting time between the steps to allow the resist cool down. | Duration of the UV-exposure depends of resist thickness, but notice that if the UV exposure becomes long then the heating at the interface with the mask can cause formation of hard skin at the surface of SU-8 so called T-topping phenomena. The the main rule is if the dose of the exposure exceeds 250-300 mJ/cm2 it is recommended to do a multiple exposure instead and have a waiting time between the steps to allow the resist cool down. | ||