Photolitography process with positive resists.

A typical positive resist (such AZ 4533 and AZ 4562) is composed of three major components: a photoactive compound (inhibitor), a base resin, and a suitable organic solvent systems. All or most of the solvent is lost afterspin and bake. The base resin alone is moderately soluble in the aqueous alkaline developer. Resist is appied to the wafer by spinning. The thickness of the resist film is a function of the spin speed. Final thickness is also affected by subsequent heating steps.
Resist films are usually chosen to be between 0.3 and 2.5 µm thick, depending on the application.


Lithography consists of six basic steps:

• Wafer Preparation
  
• Photoresist coating
  
• Softbake
  
• Exposure
  
• Development
  
• Post-Exposure Bake