Abstract:
Solutions of choline base, (2-hydroxyethyl)trimethylammonium hydroxide, in water and/or lower alkanols may be stabilized by the addition of a stabilizing concentration of formaldehyde or paraformaldehyde. The stabilized solutions may be used as cleaning solutions, etchants for semiconductors and metal layers, and developers and strippers for positive working photoresists, and for other uses where a metal ion-free base is desired.