The VINSE cleanroom has expanded its photoresist catalog for micro/nanofabrication.聽 Over the summer, VINSE Tech Crew member Elsa Fong helped develop operating parameters for UniLOR N, a negative-tone resist for single-layer liftoff processes, complementing the positive-tone resists already in use, such as LOR.聽 UniLOR N will replace NR9 in the cleanroom inventory, as users have reported that UniLOR N is more reliable and easier to work with.
Photoresists act as masks during lithographic deposition and etching. UV exposure determines their tone: positive resists (e.g., LOR) become more soluble where exposed, leaving unexposed regions; negative resists crosslink in exposed areas, which remain after development. Resist choice depends on the application and pattern. Negative resists can form undercut sidewalls, useful for hole arrays before metal liftoff or dry etching. UniLOR N research has a wide range of applications, like large-area metalenses and nanoparticle-trapping apertures, which require uniform coverage and liftoff.
The above figures compare liftoff processes on indium tin oxide (ITO) on silicon, with feature sizes ranging from 5 to 20 碌m in diameter. The resulting ITO circles were produced more consistently using negative UniLOR N resist than with positive LOR + S1805 resists.
For more details on how UniLOR N or other lithography processing could benefit your research, please contact VINSE cleanroom staff.