High mobility doped metal oxide thin films and reactive physical vapor deposition methods of fabricating the same
A method of forming a metal oxide includes providing a reactive deposition atmosphere having an oxygen concentration of greater than about 20 percent in a chamber including a substrate therein. A pulsed DC signal is applied to a sputtering target comprising a metal, to sputter metal particles therefrom. A doping element may be supplied from a doping source (such as an alloyed metal target) in the reaction chamber. An electrically conductive metal oxide film comprising an oxide of the metal is deposited on the substrate responsive to a reaction between the metal particles and the reactive deposition atmosphere. Related devices are also discussed.
1. A method of forming a metal oxide, the method comprising:
providing a substrate in a chamber;
providing a reactive deposition atmosphere defining a total atmosphere in the chamber comprising an oxygen concentration of greater than about 20 percent in a gas phase;
applying a pulsed DC signal to a sputtering target comprising a metal to sputter metal particles therefrom; and
depositing an electrically conductive metal oxide film comprising an oxide of the metal on the substrate responsive to a reaction between the metal particles and the reactive deposition atmosphere.
2. The method of claim 1 , wherein the pulsed DC signal is generated by a high power impulse magnetron sputtering (HiPIMS) power supply.
3. The method of claim 1 , further comprising:
supplying, into the reactive deposition atmosphere, a doping element from a doping source, wherein the doping element is different than the metal of the sputtering target,
wherein the reaction between the metal particles, the reactive deposition atmosphere, and the doping element is configured to control carrier concentration and/or carrier mobility of the conductive metal oxide film.
4. A method of forming a metal oxide, the method comprising:
providing a substrate in a chamber;
providing a reactive deposition atmosphere defining a total atmosphere in the chamber comprising an oxygen concentration of greater than about 20 percent;
applying a pulsed DC signal to a sputtering target comprising a metal to sputter metal particles therefrom;
supplying a doping element from a doping source; and
depositing an electrically conductive metal oxide film comprising an oxide of the metal on the substrate responsive to a reaction between the metal particles, the reactive deposition atmosphere, and the doping element,
wherein the reaction is configured to control carrier concentration and/or carrier mobility of the conductive metal oxide film at a thickness as low as about 10 nanometers (nm),
wherein the carrier concentration is in a range from intrinsic n-type concentration to about 5×10 20 cm −3 , and wherein the carrier mobility is about 300-550 cm 2 /(V·s).
5. The method of claim 4 , wherein the thickness of the conductive metal oxide film is about 10 nanometers (nm) to about 3 micrometers (μm), and wherein the conductive metal oxide film has an RMS roughness of about 5 nanometers (nm) or less.
6. The method of claim 5 , wherein a deposition rate of the conductive metal oxide film is about 10 nanometers (nm) per minute or more.
7. The method of claim 3 , wherein the doping source is a solid-phase target comprising Ag, In, Ce, Sn, Y, or F compound, or a gaseous-phase organic or metal organic doping source comprising CF 4 or other metal ions.
8. The method of claim 7 , wherein the doping element is generated by RF sputtering or HiPIMS.
9. The method of claim 3 , further comprising:
performing a post-deposition anneal of the conductive metal oxide film, wherein the post-deposition anneal comprises a temperature, a duration, and/or an atmospheric condition that is configured to increase organization of a crystal structure of the conductive metal oxide film, smooth surface properties of the conductive metal oxide film, change a carrier concentration of the conductive metal oxide film, and/or increase a carrier mobility of the conductive metal oxide film.
10. The method of claim 9 , wherein the temperature comprises about 600 to about 700 degrees Celsius (C), and wherein the duration does not exceed about one hour, or about 30 minutes.
11. The method of claim 9 , wherein the metal comprises cadmium (Cd), and wherein the atmospheric condition comprises a static oxygen supply, a dynamic oxygen supply, a volume of the chamber, and/or a Cd partial pressure of the chamber.
12. The method of claim 3 , wherein the doping element comprises indium (In) or yttrium (Y).
13. The method of claim 1 , wherein the oxide of the metal comprises CdO, In 2 O 3 , SnO 2 , BaSnO 3 , or ZnO.
14. The method of claim 13 , wherein the substrate comprises glass, quartz (SiO 2 ), sapphire (c-plane or r-plane), polycrystalline Alumina, MgO, Si, platinized Si, GaN, ZnO on c-plane sapphire, ZnO on Si, GaN on Si, or GaN on c-plane sapphire.
15. The method of claim 14 , wherein the film defines a heterojunction with the substrate.
16. The method of claim 1 , wherein the oxygen concentration is greater than about 40 percent, and wherein the total atmosphere in the chamber further comprises argon (Ar).