Photoresist is an extremely important material in integrated circuits.

Photoresists are light-sensitive polymers related to photolithography that can transfer patterns to a substrate through a radiation-induced solubility change for the fabrication of µm- and sub-µm structures. They can be used in printed circuit boards (PCB), integrated chips, and flat panel displays.

As a crucial material in the photolithography process, photoresist is mainly composed of 3 components: a polymer, a sensitizer, and a solvent. The polymer typically refers to novolac phenolic resin while the sensitizer is a photoactive compound used to limit the spectral range of reactive light. The solvent, as the largest component of photoresist, is used to keep the resist in a liquid state.

The pattern is transferred from the mask to the substrate when the photoresist film is illuminated with a specific wavelength of light. And the actual operation process of photoresists is generally divided into the following eight steps: 1) substrate preparation; 2) photoresist coating; 3) soft baking; 4) exposure; 5) medium baking; 6) development; 7) post-baking; 8) corrosion and glue removal.

Photoresists are classified as negative or positive based on the solubility of exposed portions during the development process. The exposed part of the negative photoresist is insoluble in the photoresist developer.
According to the application fields, photoresist can be classified into PCB, panel and semiconductor photoresist.
According to the exposure wavelengths, photoresist can be divided into ultraviolet photoresist, deep ultraviolet photoresist, extreme ultraviolet photoresist, electron beam photoresist, Ion beam photoresist, X-ray photoresist.