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The key material in the photolithography process is photoresist, which mainly consists of organic resins, photosensitive compounds, and solvents. Additionally, it needs to be resistant to corrosion and ion bombardment.
Silicon Wafer Surface Treatment:
The surface of silicon wafers is usually covered with thin films, such as SiO2 and polysilicon. Photolithography silicon wafers must undergo strict chemical cleaning. Moreover, silicon wafers exposed to air will adsorb water molecules, which can form silanol groups on the surface.
Due to the hydrophilicity of the silicon wafer surface, while photoresist is generally hydrophobic, it is difficult to form a sticky uniform thin film on the silicon wafer. Improving the surface hydrophobicity is mainly achieved through vacuum baking and high-purity N2 drying. A particularly effective method is to use adhesion promoters to alter the surface state, typically hexamethyldisilazane, which replaces the hydroxyl groups on the silicon wafer surface with siloxane molecules, thereby increasing the surface hydrophobicity.