NH3 Photoresist image reversal oven

Web-based Training: RSRCH - CNF - YES NH3 Image Reversal Oven Training Video

Additional Restrictions
  • No low temperature materials

The YES 58-TA oven uses NH3 (ammonia) gas to reverse the tone of positive photoresist. This can be used to create an undercut profile in the photoresist for lift-off processing. In the reversal process, the chamber is purged of oxygen using vacuum and heat. It is then filled with 500 Torr of NH3 (ammonia) vapor. The NH3 reacts with the acid in the exposed resist rendering it insoluble in developer. The proceeding flood exposure causes acid to form in the previously unexposed areas allowing them to be removed in development, leaving behind the negative image of the first exposure. A descum process using O2 plasma is recommended before deposition of lift-off material to promote good adhesion.

  • NH3 environment
  • Undercut profiles for liftoff
Processes Available
  • Image Reversal
  • N2 Bake