Copper-alloy barrier layers for metallization in thin-film transistors and flat panel displays
View Patent ↗In various embodiments, electronic devices such as thin-film transistors incorporate electrodes featuring a conductor layer and, disposed below the conductor layer, a barrier layer comprising an alloy of Cu and one or more refractory metal elements selected from the group consisting of Ta, Nb, Mo, W, Zr, Hf, Re, Os, Ru, Rh, Ti, V, Cr, and Ni.
1. A method of forming an electrode of a thin-film transistor, the method comprising:
providing a substrate comprising at least one of silicon or glass;
depositing over the substrate a barrier layer consisting essentially of at least one metal, the at least one metal comprising an alloy of Cu and one or more refractory metal elements selected from the group consisting of Ta, Nb, Mo, W, Zr, Hf, Re, Os, Ru, Rh, Ti, V, Cr, and Ni;
depositing over the barrier layer a conductor layer comprising at least one of Cu, Ag, Al, or Au;
forming a mask layer over the barrier layer;
patterning the mask layer to reveal a portion of the conductor layer, a remaining portion of the mask layer at least partially defining a shape of the electrode; and
thereafter, applying an etchant to remove portions of the conductor layer and the barrier layer not masked by the patterned mask layer, thereby forming a sidewall of the electrode:
comprising (i) an exposed portion of the barrier layer, (ii) an exposed portion of the conductor layer, and (iii) an interface between the exposed portion of the barrier layer and the exposed portion of the conductor layer, and
substantially free of discontinuities notwithstanding the interface.
2. The method of claim 1 , wherein the mask layer comprises photoresist.
3. The method of claim 1 , wherein the etchant comprises a mixture of phosphoric acid, acetic acid, nitric acid, and water.
4. The method of claim 1 , wherein the etchant consists essentially of 50-60 weight % phosphoric acid, 15-25 weight % acetic acid, 3-5 weight % nitric acid, and the balance water.
5. The method of claim 1 , wherein the etchant consists essentially of 50 weight % phosphoric acid, 25 weight % acetic acid, 3 weight % nitric acid, and the balance water.
6. The method of claim 1 , further comprising removing the remaining portion of the patterned mask layer.
7. The method of claim 1 , wherein (i) the barrier layer comprises a plurality of crystalline grains separated by grain boundaries, and (ii) the substrate comprises silicon.
8. The method of claim 7 , further comprising forming a particulate within at least one of the grain boundaries at least in part by annealing the electrode at a temperature sufficient to form the particulate, the particulate comprising a reaction product of silicon and at least one of the refractory metal elements.
9. The method of claim 1 , wherein the substrate comprises glass.
10. The method of claim 1 , wherein the substrate comprises silicon.
11. The method of claim 10 , wherein the substrate comprises amorphous silicon.
12. The method of claim 1 , wherein the barrier layer comprises an alloy of Cu, Ta, and Cr.
13. The method of claim 12 , wherein the barrier layer consists essentially of 1 weight % - 12 weight % Ta, 1 weight % - 5 weight % Cr, and the balance Cu.
14. The method of claim 12 , wherein the barrier layer consists essentially of approximately 5 weight % Ta, approximately 2 weight % Cr, and the balance Cu.
15. The method of claim 12 , wherein the barrier layer consists essentially of approximately 2 weight % Ta, approximately 1 weight % Cr, and the balance Cu.
16. The method of claim 1 , wherein the barrier layer comprises an alloy of Cu, Ta, and Ti.
17. The method of claim 16 , wherein the barrier layer consists essentially of 1 weight % - 12 weight % Ta, 1 weight % - 5 weight % Ti, and the balance Cu.
18. The method of claim 16 , wherein the barrier layer consists essentially of approximately 5 weight % Ta, approximately 2 weight % Ti, and the balance Cu.
19. The method of claim 1 , wherein the barrier layer comprises an alloy of Cu, Nb, and Cr.
20. The method of claim 19 , wherein the barrier layer consists essentially of 1 weight % - 10 weight % Nb, 1 weight % - 5 weight % Cr, and the balance Cu.
21. The method of claim 19 , wherein the barrier layer consists essentially of approximately 5 weight % Nb, approximately 2 weight % Cr, and the balance Cu.
22. The method of claim 1 , wherein:
the barrier layer comprises a plurality of crystalline grains separated by grain boundaries; and
a concentration of the one or more refractory metal elements within the grain boundaries is larger than a concentration of the one or more refractory metal elements within the crystalline grains.