Display ITO Etching & Patterning
ITO is the key transparent conductor in touch/display; etching must balance undercut control with selectivity to the substrate and other films.
1Etch chemistry
ITO (In₂O₃/SnO₂) is an amphoteric, weakly acidic oxide, so acid systems (HCl, oxalic or modified blends) give gentle, controllable undercut; dedicated ITO etchants use complexation and buffering to tune rate and uniformity. Alkaline systems attack both glass and ITO with poor undercut control, so they are generally avoided for fine patterning.
2Key controls
Temperature drives etch rate and CD (line width): keep it constant and control time for stable undercut, then rinse immediately to stop the reaction. Ensure the resist mask is not attacked and selectivity to the underlying dielectric (SiO₂/SiNₓ) is good, avoiding over-etch that drifts line width or opens lines.
3Process context
ITO patterning is critical for touch/pixel electrodes; after etch, cleaning removes residue and particles before the next dielectric/metal layer. Multi-step wet processes (etch, strip, clean, develop) must work together, as residue from any step affects final yield.