ITO liftoff

A lift-off process is specified for an ITO (Indium Tin Oxide) film deposited by RF sputtering in the Denton Explorer 14 System. The process requires the film to be deposited at room temperature, and then annealed - if necessary - after lift-off.
The process is not finalized yet and is released for reference only.

1-    PHOTO
1.1-    Prepare Substrate (may not be necessary)
        Use appropriate cleaning steps
Dry bake wafer to remove residual surface moisture
Apply HMDS as a PR adhesion promoter
1.2-    Spin PR on Substrate (dispense, spin, sofbake)
        Shipley 1813 with Site Coater to required PR thickness (see 3.1)
1.3-    Photo Exposure
        As required with EVG Aligner
1.4-    Toluene immersion (may not be necessary)
        10 minutes immersion at Room Temperature
        This is to get a negative PR slope after develop, to facilitate lift-off
        Toluene is toxic - be careful
1.5-    Develop PR on Site Coater
        DO NOT HARDBAKE THE PR! This would make it difficult to lift-off
        Then proceed to next step immediately

2.1-    Rinse & Dry
        Rinse in DIW and Blow Dry with N2 gun
2.2-    Oxygen Plasma Descum
        Use to clear residual PR if necessary
        See TVA Tepla Asher Manual for descum details
        Excessive descum may harden the PR and make lift-off more difficult
        Then proceed to next step immediately

3.1-    Sputter ITO in Denton
        Room Temperature RF deposition (no substrate heating: very important!)
        Recipe ITOCOLD with deposition time as required
        Maximum ITO thickness = 25% of PR or 500 nm, whichever is smaller
    3.2- Proceed to next step within 24 hours

    4.1-    Acetone immersion
        US bath @ 40 C x 20 min OR Simple bath @ RT x 60 min
        Repeat with new bath if necessary
        Then proceed to next step immediately
4.2-    Acetone spray rinse
        This is to flush lift-off debris from the wafer
        Then proceed to next step immediately
4.3-    IPA immersion
Simple bath @ RT x 5 min
        This is to dissolve as much acetone residues as possible
        Then proceed to next step immediately
4.4-    IPA spray rinse
        This is to flush acetone residues from the wafer
        Then proceed to next step immediately
    4.5-    Dry
Blow-dry with N2 gun AND/OR Spin-rinse & Dry in Verteq