Thin film batteries and methods for manufacturing same
A method of fabricating a layer of a thin film battery comprises providing a sputtering target and depositing the layer on a substrate using a physical vapor deposition process enhanced by a combination of plasma processes. The deposition process may include: (1) generation of a plasma between the target and the substrate; (2) sputtering the target; (3) supplying microwave energy to the plasma; and (4) applying radio frequency power to the substrate. A sputtering target for a thin film battery cathode layer has an average composition of LiM a N b Z c , wherein 0.20>{b/(a+b)}>0 and the ratio of a to c is approximately equal to the stoichiometric ratio of a desired crystalline structure of the cathode layer, N is an alkaline earth element, M is selected from the group consisting of Co, Mn, Al, Ni and V, and Z is selected from the group consisting of (PO 4 ), O, F and N.
1. A method of fabricating a thin film battery cathode layer, comprising:
providing a sputtering target with an average composition of LiM a N b Z c , wherein 0.20>{b/(a+b)}>0, N is an alkaline earth element, M is selected from the group consisting of Co, Mn, Al, Ni and V, and Z is selected from the group consisting of (PO 4 ), O, F and N; and
depositing said cathode layer on a substrate using a plasma enhanced physical vapor deposition process, said depositing comprising:
applying power from a target power source to said sputtering target to generate a plasma between said sputtering target and said substrate;
during applying power from said target power source to said sputtering target, applying power from an additional power source to at least one of said sputtering target, said plasma and said substrate; and
controlling both said target power source and said additional power source to redirect plasma energy from ions in said plasma between said sputtering target and said substrate to ions travelling to said cathode layer for forming said cathode layer.
2. A method as in claim 1 , wherein 0.12>{b/(a+b)}>0.05.
3. A method as in claim 1 , wherein said cathode layer has a spinel composition and morphology, M is Mn, and Z is O.
4. A method as in claim 1 , wherein M is Co, Z is O, and said cathode layer has a composition and morphology of LiCoO 2 .
5. A method as in claim 1 , wherein said sputtering target has an electrical resistivity of less than 1E5 Ohm-centimeters.
6. A method as in claim 1 , wherein said cathode layer has an electrical resistivity of less than 1E1 Ohm-centimeters.
7. A method as in claim 1 , wherein said cathode layer has a thickness greater than 3 microns.
8. A method as in claim 1 , wherein said depositing step includes (1) generation of a plasma between said sputtering target and said substrate and (2) application of pulsed direct current to said sputtering target.
9. A method as in claim 8 , wherein said depositing step further includes (3) applying radio frequency power to said substrate, and (4) supplying microwave energy to said plasma.
10. A method as in claim 1 , wherein said depositing step includes (1) generation of a plasma between said sputtering target and said substrate and (2) supplying microwave energy to said plasma.
11. A method as in claim 1 , wherein said depositing step includes applying radio frequency power to said substrate.
12. A method as in claim 1 , wherein said depositing includes:
applying radio frequency power from said target power source to said sputtering target to generate a plasma between said sputtering target and said substrate;
during applying radio frequency power from said target power source, applying radio frequency power from said additional power source to said sputtering target; and
controlling both said target power source and said additional power source to simultaneously increase the sputter rate of said sputtering target and redirect plasma energy from ions in said plasma between said sputtering target and said substrate to ions travelling to said cathode layer.
13. A method as in claim 12 , wherein said depositing includes applying direct current power to said sputtering target.
14. A method as in claim 13 , wherein said direct current power is pulsed direct current power.
15. A method as in claim 12 , wherein said depositing includes applying radio frequency power from a substrate power source to said substrate.
16. A method as in claim 15 , wherein the frequencies generated by said target power source and said substrate power source are different.
17. A method as in claim 15 , wherein the frequencies generated by said target power source and said substrate power source are the same and are locked in phase.
18. A method as in claim 12 , wherein said sputtering target is a rotatable cylindrical target.
19. A method as in claim 12 , further comprising supplying microwave energy to said plasma.