Dear Franck, Thanks for the challenge.....As a rule we recommend a dispense volume of 1ml per inch, but obviously this is influenced by a number of other parameters, the viscosity of the resist being a key one, however I believe that as a matter of routine we are not dispensing any more than 10ml per 4inch wafer in our Applications Lab here in Newton, MA.... Other parameters that will affect the dispense volume of SU-8 100 : * Spin Coater - Here at MicroChem we use a Brewer Science CEE 100CB coater and find that for all SU-8 formulations the volume required to uniformly coat a 4 inch silicon wafer is consistently below 10ml, and for the less viscous formulations this can go as low as 2ml...What type of spin coater are you currently using ? * Coating environment - We have found a correlation between the ambient temperature of the environment where the wafers are being coated and the film thickness/uniformity....For example, a decrease in the temperature causes a significant increase in the viscosity and hence a thicker film is produced, this also has an impact on the coating uniformity and coverage of the wafer....Here at MicroChem we control the coating environment to 71F +/- 1F...All of the data included in the data sheets and on the website were generated using this setpoint...Should you be using different setpoints you will see different coatings and film thicknesses, and different dispense volumes will be required.... * Dispense Method - I believe the method you currently use is static dispense, ie the wafer is not rotating while you dispense the SU-8 100 to the substrate, is this correct ?....You may want to try rotating the wafer at around 250rpm-500rpm while you dispense the resist, then perform an intermediate spread cycle, followed by the final spin speed....this should help to keep the resist moving over the surface and provide a better coat with less material consumed.... * Final Film Thickness - The final film thickness you require can also impact the coating phase in that a higher spin speed will allow for less material to be dispensed, due to improved spreading, but will also yield a lower film thickness...By using a higher spin speed you can also obtain more uniform coatings and in fact in order to gain very thick films of greater than 300ums we recommend performing 2 or more coats so that higher spin speeds can be used to get more uniform coats without the large edge bead being produced, of course a bake step needs to be performed in between each coating phase.... I hope the information listed above is of use to you and should you have any questions please do not hesitate to contact me.... Mark Shaw Technical Sales & Applications Support MicroChem Corp. email: mshaw@microchem.com url: www.microchem.com Dear all, I'm proposing a small competition: who could use the smallest amount of SU8-100 photoresist to fully spin-coat one wafer? Please detail your method and what is the best figure you have obtained sofar expressing them in ml/inch for easier comparison. And what will be the price for the winner? Well, the eternal thanks from his peers, some disdain from the manufacturer (no, I'm sure they are not that mean :-), and for sure a full feature into http://aveclafaux.freeservers.com/SU-8.html#top! And don't be shy, the 'best' method I know of currently (pouring from the bottle a central puddle then two steps spinning, with first a few hundred rpm to dispense and then ramping to the final speed) is using more than 25ml/4inch wafer (7ml/inch...) :-( FranCk PS: don't forget it is for SU8-100 only, the most visquous in the standard MCC series.