Air bubbles often occur when resist bottles are e.g. shaken or moved around before coating, or if a resist is diluted. They may also appear if the coating step is performed immediately after opening of the resist bottle, particularly if the resist temperature is not allowed to adjust to room conditions.
When new and clean substrates (wafers) are used, a heating at approximately 200 °C for several minutes (2-3 min, hot plate) is sufficient for drying. Substrates should however subsequently be processed quickly.
Process procedure e-beam resist
Development of PMMA films PMMA films can only be developed with solvent-based developers. Aqueous-alkaline PMMA developers will not attack PMMA – PMMA is even used as protective coating in the presence of strongly alkaline solutions.
Photoresists are light-sensitive, their properties change in the presence of light or elevated temperatures. Resists age during storage and are therefore supplied in light-protected amber glass bottles,