Aqueous-alkaline developers are subjected to ageing, due to an uptake of CO 2 from the air. Buffered aqueous-alkaline developers (AR 300-26, -35) are more stable in this respect than developers of the AR 300-40 -series containing TMAH. Within this series, developers with the TMAH concentration are most sensitive. TMAH developers with an 0,1 normal concentration (AR 300-49) change the development performance in an open container after 3 – 4 hours. Opened containers should be hermetically sealed immediately after removal of developer and consumed as fast as possible. Developers should be diluted immediately before use.
A frequent opening of containers may cause evaporation of solvent-based developers and alter the composition of the developer. These changes may also affect the development process. Developers should therefore be stored tightly sealed.
Of course the developers age expendably during immersion development with a growing number of processed wafers. The amount of wafers which can be developed in a bath depends on the size of the bath, the amount of exposed resist per wafer, the number of wafers and the immersion times. When the development times are extended about 20 % compared to the beginning, it is high time to change the developer.
Overview Process Chemicals- Developer