Overview
PMMA (Polymethyl methacrylate) is a positive resist used for direct electron beam writing and as a polymeric coating for wafers. 495 indicates that the PMMA is of molecular weight 495K.
NANO 495 PMMA
Process and Preparation
- Substrate should be clean and dry, oxygen plasma can be used as well as solvents such as acetone and isopropanol alcohol (IPA). Dry using a nitrogen gun
- Select the appropriate spin speed for desired film thickness
- Prebake wafer on hotplate for 60 - 90 seconds at 180 °C
- Cool to room temperature place on spinner and set spinner parameters
- Deposit resist onto wafer and start spin process
- Perform post-bake at 100 °C for 60 - 90 seconds
- Check for dust particles, color consistency in the resist (except at edges).
- Expose using various means, such as electron beam.
- Develop, typically using MIBK, MIBK diluted with IPA (1:1, 1:2, or 1:3).
- To terminate development and prevent scumming place the developed sample into a fresh solution of MIBK/IPA at 1:3 or 1:4, dry using nitrogen gun.
- Remove PMMA resist, this can be done using cleanroom solvents, acetone, PR thinners, and positive photoresist removers.
Materials
- Oxygen Plasma
- Solvents such as IPA, acetone, PR thinners, positive photoresist removers
- Nitrogen gun
- Hot plate
- Spinner
- MIBK
Safety
- Avoid contact with eyes, skin, and clothing
- Use adequate ventilation and avoid breathing in fumes
- Wear chemical resistant eye protection, protective gloves and clothing
- In case of PMMA eye contact flush eyes with water for fifteen minutes and contact a physician
General Documentation
- SDS
- SOP
- NANO 495 PMMA
Equipment
- Developer Bench
- PR Bench