The main steps in lithography are:

• Applying the vapor prime
•  Applying the photoresist
• Soft bake
• Aligning the mask with the wafer and exposing the wafer to light through the mask
• Post exposure bake
• Develop the resist
• Hard bake
• Develop inspect
• Etch
• Final inspect

• First the wafer is heated to remove water (dehydration bake 200oC) - only one H₂O layer remains
• HMDS (Hexamethyldisilazan) or vapor prime is applied by spin coating
  • Purpose: promotes adhesion, without HMDS, the resist may not adhere well to the wafer, and lift-off may appear, causing the wafer to be exposed to etchants
  • The picture shows how HMDS molecules establish a chemical connection between substrate and photoresist