Development

 

The positive photoresist on the parts that were not masked during reacts and dissolves in the developing solution, which is alkaline. The parts that were exposed to intense light changes, and the mask pattern of photoresist is left on the surface of the wafer.

 

Developing solutions originally often contained sodium hydroxide (NaOH), a highly alkaline compound. However, sodium is deemed as an extremely undesirable contaminant in metal-oxide-semiconductor field-effect transistor (MOSFET) fabrication because it degrades the insulating properties of gate oxides. Metal-ion-free developer such as tetramethylammonium hydroxide (TMAH) is now used.