Why is photoresist applied to a silicon wafer during chip manufacturing?

In the manufacturing of integrated circuits, photoresist is applied to a silicon wafer to enable the precise patterning of circuit designs through a process called photolithography.12

The photoresist acts as a light-sensitive coating that allows engineers to selectively protect or expose specific areas of the wafer. The process functions as follows:12

• Exposure: The wafer is coated with photoresist and exposed to radiation (such as ultraviolet radiation) through a mask. The mask blocks light in certain areas, ensuring only the desired pattern is transferred to the resist.12
• Development: Exposure changes the solubility of the photoresist. When the wafer is developed, the soluble portions are washed away, leaving behind a protective pattern of hardened resist.12
• Modification: The exposed, unprotected areas of the underlying substrate can then be modified through processes like etching, deposition, or implantation, while the remaining resist shields the rest of the wafer.2
• Removal: Once the specific layer is modified, the remaining photoresist is dissolved using a solvent, and the process repeats for subsequent layers.2