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YES Image Reversal Oven

Photoresist image reversal oven

YES-58SM Image Reversal Oven Backup: Edward Camacho , Michael Skvarla


The YES 58-SM 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 600 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 after lift-off to promote good adhesion of deposited material


  • NH3 environment
  • Undercut profiles for liftoff

Additional Resources:

Image Reversal Basics
YES Image Reversal Oven Instructions

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