SU-8 Handling Protocol
Where and how you can use SU-8, from substrate prep through final development, in SNF.
- When working with SU-8, it is important to remember that one person’s resist is another’s contaminant. One must make sure that each part of a process is accompanied by steps to prevent and eliminate SU-8 contamination of lab equipment.
- Remember that SU-8 is a flammable and toxic substance. Refer to the MSDS sheet for complete hazard information.
- Before working with SU-8, make sure that you are double-gloved.
- Like all chemicals in the SNF, SU-8 and SU-8 developer should be transported in a metal cart. Return these items to the flammable chemical storage bin in which they are kept as soon as you are done using them. Do not leave them out unattended.
- Wafers must be transported in a personal cassette only. Using lab cassettes will contaminate them, any wafers subsequently placed in them, with SU-8.
- Any personal equipment such as cassettes, glassware, or tweezers used to handle wafers coated with SU-8 must be labeled with your CORAL login and a warning of SU-8 contamination. This equipment should only be used with wafers coated with SU-8 and only in equipment approved for use with SU-8.
- If you have any questions with regard to handling SU-8 in the laboratory, please do not hesitate to ask SNF staff. Asking questions now will prevent mistakes in the future that could be costly, both in terms of time and money, to correct.
- Refer to www.microchem.com for spin speeds, baking times, and exposure energies for desired thicknesses. These are great starting points, but may require adjustment.
Preparation and Priming
- If you are using a very dilute form of SU-8 (such as 2000.5), a piranha clean is recommended to increase uniformity and coverage of spincoating.
- Priming the wafer with HMDS in the yes over or on the svgcoat track is recommended to increase adhesion of SU-8 to the wafer. Wafers must be free of photoresist or any polymer prior to priming in the yes oven.
- Spincoating SU-8 must be performed on the headway2 only to prevent contamination of other instruments.
- The basin and rim must be covered in several layers of clean aluminum foil. The previous user should have done this, but it is your duty to make sure this has been done before you use it.
- Cover the surface with foils or wipes; place the bottle on the cover surface only.
- This makes cleanup up much easier.
- After dispensing resist on the wafer, either move it to your personal cassette or begin prebaking. See the following Prebaking section for proper protocol during this step.
- When you are done spin coating, remove all aluminum foil from the instrument and place it in a plastic bag. Remove your gloves and place them in the bag. Seal the bag and put on a new pair of gloves.
- It is wise to try to clean the chuck at solvent bench immediately, the longer it sits the harder to clean the polymer off of it. Squirt generous amount of acetone and follow it up with methanol and isopropyl over the solvent bench.
- Inspect the basin and bench top. Remove any SU-8 from these surfaces by first with acetone followed by isopropanol. Place any used wipes in the plastic bag.
- Deposit the bag in the headway2 trash bin.
- When you are confident the headway2 is free of SU-8, cover the basin and rim in several layers of fresh aluminum foil.
- If photoresist is present on the headway2 when a labmember comes to use it, it is that labmember’s responsibility to report the problem on CORAL and clean up the photoresist. The previous user will be placed on Community Service.
Prebaking and Postbaking
- Baking wafers coated with SU-8 must be performed on a hot plate covered with aluminum foil. This will prevent contamination of any subsequent users’ wafers with your SU-8.
- When baking is completed, remove the aluminum foil from the hot plates and place it in a plastic bag. Dispose of the bag properly.
- SU-8 on wafers must be cured (prebaked) prior to use in any exposure instrument. Never place an uncured wafer on any exposure chuck!
- Wafers coated with SU-8 can only be exposed on Karlsuss and Evalign instruments. Use of any other exposure instrument (including ASML) is strictly prohibited.
- Development of wafers coated with SU-8 must be done in personal glassware in a solvent wet bench. Remember that this dish must be labeled as SU-8 contaminated and has your name on it. Contaminated beakers can not be left on the solvent bench.
- If you are using my beakers for development you need to clean them, dry them and put back in the box. Again contaminated beakers can not be left on the solvent bench. We will show you where the box is during training.
- SU-8 developer is very volatile. To prevent its fumes from reaching the common lab environment, the developer dish should be placed in the rear of the fume hood.
- A blue hazard info sheet must be filled out and placed under the dish while it is in use.
- Following development, spray both sides of the wafer with isopropanol and dry with the air gun over the solvent waste bin.
- All spent developer must go in the carboy in solvent bench.
- When you are finished, spray the inside of the dish with isopropanol and dry with the air gun over the solvent waste bin.
- When using shared lab equipment, make sure the area is clean and free of resist when you are finished.
- Report any problems encountered during your process with lab equipment on CORAL.
- Need help? Ask a Litho Staff member.