Photoresist is a mixture of polymers and some compounds, among which the most important is a photo acid generator (PAG). When photons hit PAG, an acid is produced that reacts with the polymer, decomposing it and causing it to be dissolved by the developer.
Photolithography photoresist is usually divided into two types: positive photoresist and negative photoresist.
Positive photoresist: The exposed portion is soluble in the developer solution, while the unexposed portion is insoluble in the developer solution. After development, the remaining photoresist pattern on the substrate is the same as the target pattern on the mask plate.
Negative photoresist: The exposed portion is insoluble in the developer solution, while the unexposed portion is soluble in the developer solution. The remaining photoresist pattern on the substrate after development is complementary to the target pattern on the mask plate.
Therefore, for positive photoresist, etching the substrate without photoresist protection after photolithography is completed, and finally washing away the remaining photoresist, achieves the one-step construction process of semiconductor devices on the substrate surface.
