LIFT-OFF FOR DIFFICULT TO ETCH METALS
“Lift-Off” processing for films that cannot be plasma etched due to either un-available dry chemistries; or wet chemically removed; due to line-width undercutting which result in poor critical dimension control. Metal films that have been successfully “lifted-off” include: Al., Ag., Ru., Ni., Cr., Ti., TiN, Pt., with critical dimensions ranging from the sub-microns to hundreds of microns.
Noel Technologies incorporates 1 of 3 documented “lift-off” lithography processes:
- Single layer positive
- Negative resist processing
- Bilayer process in which the “undercut” can be tailored to the customer’s specification.
- Noel has introduced a patented process called an “Inorganic Lower Layer” that generates a planarized profile in the metal that improves reliability.
- Substrates are resist coated.
- Customer specific mask designs are patterned onto the individual substrates.
- Substrates are coated with the customer’s requested metal film.
Wafers are “soaked” in either a heated NMP solvent or if easily removable; a room temperature acetone. Substrate is agitated to remove over-burden metal resist (metal on top of the resist), is completely and cleanly removed.
- Once completed through the lift-off process, the substrates are comparable to products that were patterned and etched in the conventional method; employing either plasma or wet-etch methodologies.
Please note that any metals not compatible or complementary to Noel’s existing work flow, are processed in isolated work areas to avoid cross-contamination.