Did you carefully clean the glass slide prior to SU8 deposition? Glass slides are often contaminated with hydrocarbon and sometimes silicone contaminants which can have a negative impact on adhesion. Clean first in alkanox soap solution in water and rinse in IPA. Take care not to redeposit any contaminants on the glass. Carefully dry with dry nitrogen.

In the Semicon industry they would do a much more extensive cleaning of Silicon wafters prior to photoresist application (RCA cleaning method?).

Use primer such as A1100 before applying the adhesive

As recommended by Greg, clean first in alkanox soap solution in water and rinse in IPA. Take care not to redeposit any contaminants on the glass. Carefully dry with dry nitrogen.

If you need truly highest level of adhesion, it would be good to use the following procedure:

(1) wipe the surface (2x) with IPA,

(2) expose the surface to oxidising treatment, e.g.: corona jet / atmospheric plasma / corona discharge /  flame treatment,.

(3) apply 0.1%-0.5% (p.w.) of epoxy-functional silane [e.g. such, as recommended by Alisa Buchman (A-1100), or Dow Corning's Z-6040],

(4) dry it overnight at RT or, better: dry in the convection oven at 140 degrees C for approx. 20-25 minutes.

The above protocol should provide superior strength of adhesion and good long-term durability. 

I

Hi Paresa, 

As suggested above by RG members I would recommend cleaning you slides carefully.   This is the protocol I use for cleaning my glass slides before coating

i.  Clean beakers using Decon 90 and rinse with deionised water.

ii. Warm a solution of 5% decon in deionised water on hot plate at ~60 for about 10 minutes.  Put samples on a sample holder and place beaker in ultrasonic bath and clean for 8 minutes.  Rinse with deionised water afterwards. 

iii Repeat same step with 0.5% decon and then just deionised water. 

iv. Bathe in IPA and blow dry with nitrogen into the fume cupboard.  Warm on hot plate to about 45 C for a short period to boil off IPA. (Don't use higher temperature than this hope you now why :) )

Please avoid dust while your are transferring your sample from coating to the hot plate. Use a petri plate to cover the slides while doing transfer and cover them using the same while doing softbake. 

Hope this helps 

Cheers 

Akhshay