Beside original trading units for production lines, for many of our resists we also offer small volume units (e.g. 250, 500 and 1.000 ml) rebottled in our clean room area class 10 in order to meet the demand of universities and research institutes.
Storage conditions of resists
The ageing of photo resist appears in particle formation and loss of the photo active compound. While the latter reflects in a reduced photo speed and easily can be compensated with a higher development time, particle formation impacts on lithographic performance and impacts more stronger on smaller structure sizes. For minimum ageing even beyond the nominal expire date, we recommend cooling the resist at a temperature of optimum 5-8°C. In this case, it is indispensable to bring the resist to room temperature before opening, otherwise condensing water might destroy the resist. Beyond original sales units, MicroChemicals offers 250 ml, 500 ml and 1000 ml bottles for all standard resists. If the operator anyway prefers to refill resist bottles into smaller units, we recommend a double-stage cleaning process of the bottles with i) acetone and ii) isopropyl. Since isopropyl deteriorates the resist, care has to be taken to remove traces of isopropyl before filling the bottles with resist.
Storage conditions of developers
The ageing of aqueous alkaline solutions appears in CO2 adsorption from air. As a consequence, the activity of the developer decreases thus increasing the development time. For this reason, we recommend the storage of developers in well-closed original bottles. If used over a period of several days in open tanks, a N2 stream will minimize the CO2 adsorption.