After baking at 180 o C for 60 minutes a hard dense film results which can be patterned and used as a mask for wet or dry etching of the thick polymer under layer used in tri level processing. Lower bake temperature or shorter time may result in a cracked film.
Similar considerations apply to polyamide layers.
Spin Silicafilm 13 at 3000 rpm. Bake at 180 o C in air or at higher temperatures compatible with the first polymer layer. Spin thin positive photo sensitive layer and expose and develop as per usual process. Silicafilm 13 may be patterned by etching in buffered HF solution, or by plasma etching.