19. Which photoresists are suitable for hydrofluoric acid (HF) etching?
The positive tone photoresist X AR-P 3100/10 is extremely adhesion enhanced and thus suitable for HF etching of up to 5 % HF. In particular on glass or silicon oxide, a pre-treatment of substrates with the adhesion promoter AR 300-80 is strongly recommended. With X AR-P 3100/10, a film thickness of 5 μm can be achieved at 4 000 rpm. This high thickness is advantageous to obtain a high etch resistance.
After the coating step, the hotbake should be performed on a hot plate at 85 - 90 °C for 2 min. In comparison to standard resists, this resist is less sensitive and consequently requires longer exposure times.
For the development of exposed resist films, undiluted developer AR 300-26 is recommended. The development time should amount to approximately 60 s.