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You are here: Home / Equipment / Dry Etching / Gasonics Aura Plasma Asher, gasonics (semi-clean) / Process Qualification Procedures

Process Qualification Procedures

Instructions on how to run a qualification process for Gasonics.



The Equipment

The Gasonics Aura Asher is an automated upstream microwave plasma system used for stripping photoresist of clean 4” silicon wafers. The system generates plasma of oxygen and nitrogen in a reaction chamber. This reactive mixture flows downstream to the process chamber where it reaches a state of “afterglow,” where it is highly reactive and no longer electrically active or damaging to the wafer surface. The dissociated oxygen chemically reacts with the photoresist effectively burning the resist off the wafer.

The machine is considered to be in the clean and semi-clean equipment group. Gasonics also offers many features including the ability to complete front and backside removal.

Process Monitoring and Machine Qualification



In order to ensure that the machine is operating properly, the qualification runs ensure that all desired photoresist has been stripped from the wafers.



These qualification runs are to be completed on a monthly basis, and information regarding the results of such shall be posted for the public to review if desired. Monitoring may also occur as needed/requested by user reports and concerns or after major repairs.




Wafers for Processing

  • One 4” Si wafer coated with 1.0 um of 3612 photoresist

  • One 4” Si wafer coated with 7.0 um of 220-7 photoresist.


Etch Process

  1. Run each wafer through the process using Recipe 3 for a strip time of 45 sec [used for 1.0 or 1.6 Micron SPR 3612 (As-Spun or Plasma Processed)].


Examining the Wafer

After the wafer has been run through the process, it is removed from the chamber and examined closely using a microscope to check for stripping efficiency. Careful observation much be taken of the etch parameters, power, pressure, and gas flow.  The photoresist should have cleared from the desired surface of the inputted wafer. The test is binary, was the photoresist removed completely or not.


Recycling Wafers

        After both wafers have been examined and the results recorded, they are available to be recycled for future qualification runs. They will only need to be repatterned (if ensured they are fully stripped) in Litho with the same photoresist requirements that were noted in the beginning of this process. This recycling helps save from the need to buy new wafers.



This monitoring will be handled on a monthly basis by the students of SUMO, but users are encouraged to run a qualification process if they feel the tool is not in good running order. The staff should be informed of the results retrieved from such a run so as to add to the previously collected data.

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