Positive resist

Photoresist, polymer varnish which is practically insoluble after drying. However, the varnish has a radiation-sensitive additive, a so-called photo initiator. When exposed to light, it transforms to become H₂CO₃ , which makes the coat of varnish easy to dissolve in weak alkaline solutions. Thus, only the non-exposed areas are removed after exposure and subsequent development, the exposed areas remain stable.