Abstract: A method of forming an etch barrier in the reactive ion etching of an aromatic polyamic acid/imide which comprises:coating a surface with a layer of an aromatic polyamic acid;at least partially curing the layer of aromatic polyamic acid to the corresponding aromatic polyimide;in situ converting the surface layer of the aromatic polyimide to a silicon containing alkyl polyamide/imide;applying, exposing, and developing a layer of photoresist over the silicon containing alkyl polyamide/imide to selectively expose a portion of the silicon containing alkyl polyamide/imide surface layer;reactive ion etching the exposed portion of the surface layer of the silicon containing alkyl polyamide/imide with carbon tetrafluoride to remove the exposed portion of the silicon containing alkyl polyamide/imide surface layer;reactive ion etching the resultant structure with an oxygen agent to etch an interconnect in the aromatic polyimide while removing the photoresist down to the silicon containing alkyl polyamide/imide surface