Pre-Baking, also known as soft baking, is the physical process of converting a liquid photosensitive polymer into a solid film. The pre-baking process is similar to the curing process, but is performed at a much lower temperature. The pre-bake temperature varies in range from 70-110 'C, depending on the material. During pre-bake, the solvents are removed from the polymer coating and temporary adhesion of the polymer to the substrate is established.

Pre-baking plays a very critical role in photolithography. The polymer coatings become photosensitive, or imageable, only after softbaking. Over-baking will degrade the photosensitivity of resists by either reducing the developer solubility or actually destroying a portion of the sensitizer. Under-baking will prevent light from reaching the sensitizer. Positive photosensitive polymers are incompletely exposed if considerable solvent remains in the coating. This under-baked positive polymer is then readily attacked by the developer in both the exposed and unexposed areas, causing less etching resistance.

• Prebake temperature
• Prebake time
• Polymer thinning rates and ratios
• Resist Adhesion