Specific Process Knowledge/Lithography/SU-8: Difference between revisions
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Process recommendations: | Process recommendations: | ||
* a standard process consist of spinning, soft bake, exposure, post bake and development. Please notice that the entire process must be done continuously, meaning that it is not recommendable to spin the resist and then wait until the next day before exposing. | * a standard process consist of spinning, soft bake, exposure, post bake and development. Please notice that the entire process must be done continuously, meaning that it is not recommendable to spin the resist and then wait until the next day before exposing. | ||
* exposure using radiation above 350 nm is recommended. | * exposure using radiation above 350 nm is recommended. Aligner: 6inch uses a long-pass filter which reduces the i-line and blocks shorter wavelengths, while KS Aligner and Aligner: MA6-2 both have i-line filters. | ||
* Controlled soft and post-exposure bakes are recommended and must be optimized for the specific application, but baseline parameters which can be used as a starting point will be given. | * Controlled soft and post-exposure bakes are recommended and must be optimized for the specific application, but baseline parameters which can be used as a starting point will be given. | ||
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==Exposure== | ==Exposure== | ||
The exposure step is usually done in near UV-radiation at aligners system which blocks the wavelengths below the i-line (365nm wavelength). | The exposure step is usually done in near UV-radiation at aligners system which blocks the wavelengths below the i-line (365nm wavelength). Aligner: 6inch uses a long-pass filter which reduces the i-line and blocks shorter wavelengths, while KS Aligner and Aligner: MA6-2 both have i-line filters. | ||
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. | ||