Tuesday, October 31, 2006

Photolithography process

Before spin resist it is necessary:
· Clean GaAs wafer piece in NPM hot, ID water, 2-Propanol, ID water.
· Dehydration bake @ 110° C for 5 minutes

Positive Photoresist





Negative reversal process for resist AZ 5214E


Spin-coat resist 5000rpm for 60s
Soft bake at 110° C for 60s
Expose at 10mW/cm2 with UV light for 1.8s (maskaligner MA6 or MJB3)
Bake at 110° C for 60s
Flood expose without mask for 4s
Develop in MF319 developer for 25s and rinse with ID water

Negative Photoresist






































































































































Photoresist





Spin Speed/Time





Soft bake Temp/Time





Exposure Time (assuming 10mW/cm2)





Develop Time




(Developer MF 319)





Post-Exposure Bake
Temp/Time





Thickness





AZ 5214E





5000rpm/60s





110° C/60s





3s





20s





115° C/60s





1.3um





AZ 1818





5000rpm/60s





110° C/60s





4s





22s





115° C/60s





1.6um





AZ 4533





5000rpm/60s





110° C/60s





10s





35-40s





115° C/60s





3.5um





AZ 4562





5000rpm/60s





110° C/60s





15-20s





50-60s





115° C/60s





5um


Thursday, June 22, 2006

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 ┬Ám thick, depending on the application.


Lithography consists of six basic steps:

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