Selective metal/metal oxide etch process

1. A process for selectively etching molybdenum or titanium relative to a oxide semiconductor film, comprising:

providing a substrate comprising a layer of oxide semiconductor and a layer comprising molybdenum or titanium on the layer of oxide semiconductor;

preparing the substrate by applying a photoresist layer over the layer comprising molybdenum or titanium, and then patterning and developing the photoresist layer to form an exposed portion of the layer comprising molybdenum or titanium;

providing a composition comprising ammonia or ammonium hydroxide, a quaternary ammonium hydroxide and a peroxide; and

applying the composition to the exposed portion for a time sufficient to etch and remove the exposed portion of the layer comprising molybdenum or titanium, wherein the etching selectively removes the molybdenum or titanium relative to the oxide semiconductor,

wherein the composition comprises:

3-10 wt. % ammonia;

0.01-0.5 M quaternary ammonium hydroxide; and

0.1-7 wt % hydrogen peroxide.

2. The process according to claim 1 wherein the selective etch removes substantially all of the exposed portion of the layer comprising molybdenum or titanium and substantially none of the layer of oxide semiconductor.

3. The process according to claim 1 wherein the selective etch exhibits a metal/oxide semiconductor selectivity of at least 6:1.

4. The process according to claim 1 wherein the oxide semiconductor comprises IGZO or ITZO.

5. The process according to claim 1 wherein the layer comprising molybdenum or titanium further comprises a layer of aluminum or a layer of copper on the layer of molybdenum or titanium on the layer of oxide semiconductor.

6. The process of claim 5 , wherein the layer comprising molybdenum or titanium further comprises a second layer of molybdenum or titanium on the layer of aluminum or on the layer of copper, forming a Mo/Al/Mo sandwich, a Mo/Cu/Mo sandwich, a Ti/Al/Ti sandwich or a Ti/Cu/Ti sandwich.