I am using SU-8 1060 (20micrometer thickness), but find difficulty in optimizing exposure dose for 10micron features.Larger features upto 250micron developed good on exposure time 4-5sec for Intenisty=23mW/cm2 (MJB4). Similarly large features developed on 10sec & 20 sec too. But I am unable to get better results for smaller features. I need to develop 10 micron features.
Hello Amina,
What defects are you observing? Do you have images? There are many factors that can affect the results.
General recommendations are to ensure very good contact between the mask and film. Check the softbake duration- extending it will reduce solvent concentration and therefore dark erosion during development, improving resolution. However, you run the risk of introducing new problems such as swelling, adhesion failure, etc., so be cautious. Also make sure that your developer solution is in date.
With thicker SU-8 films I have had to use a long-pass optical filter (ZJB360, Omega Optical) to reduce 'T-topping', DOI: 10.3390/s16122128.
What is the substrate and thickness? For instance I have found there is a large difference between required parameters for borosilicate glass when compared to silicon. For glass I have also had to place a film between the wafer/die and the chuck to reduce reflections.
How good is the adhesion between the resist and substrate? How are you cleaning the substrates?
You could dilute the SU-8 with cyclopentanone to get a thinner film, see: https://www.researchgate.net/post/How_do_you_get_an_uniform_50nm_film_thickness_of_SU-8_direct_on_the_glass_substrate).
I have also attached a link to a 'photolithography troubleshooter' that you may find useful.
Finally there is a wealth of information here: http://memscyclopedia.org/su8.html
Let us know how you get on.
Jules
http://www.microchemicals.com/technical_information/exposure_photoresist.pdf
Thanks alot for the detailed answer. My film thickness is 20-micrometer and its okay. My small features are not developing ...either under or over exposed or something else. FEATURES UPTO 250 MICRMETER and larger DEVELOPED very well on 4-5sec (intensity =23mW/cm2). Tell me whether i have to decrease or increase exposure time for small features. My soft bake and PEB temperatures are 65C (10min) and 95C(30min)
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