Manufacturing method for thin film battery
A thin film battery manufacturing method is provided for deposition of lithium metal oxide films onto a battery substrate. The films are deposited in a sputtering chamber having a plurality of sputtering targets and magnetrons. The sputtering gas is energized by applying a voltage bias between a pair of the sputtering targets at a frequency of between about 10 and about 100 kHz. The method can provide a deposition rate of lithium cobalt oxide of between about 0.2 and about 4 microns/hr with improved film quality.
1. A method of depositing a lithium cobalt oxide film on a
battery substrate in a sputtering chamber comprising (i) a substrate support, (ii) first and second sputtering targets, (iii) a first electrode contacting the backside surface of the first sputtering target and a second electrode contacting the backside surface of the second sputtering target, and (iv) a first magnetron comprising a first rotatable magnet assembly behind the first sputtering target and a second magnetron comprising a second rotatable magnet assembly behind the second sputtering target, the method comprising:
(a) placing an array of substrates on the substrate support;
(b) providing first and second sputtering targets in the sputtering chamber, the first and second sputtering targets each consisting of lithium metal oxide;
(c) maintaining a sputtering gas at a pressure in the sputtering chamber;
(d) energizing the sputtering gas by applying an alternating voltage from an AC power supply to the first and second electrodes at a frequency of between about 10 and about 100 kHz such that each of the first and second electrodes alternately serves as an anode or a cathode; and
(e) rotating the first and second rotatable magnet assemblies at a rotational frequency of between about 0.005 and about 0.1 Hz to provide a variable magnetic field about the first and second sputtering targets.
2. A method according to claim 1 wherein the substrate support is electrically isolated from a wall of the sputtering chamber and from the first and second sputtering targets.
3. A method according to claim 2 wherein the substrate support is powered by a biasing power supply that provides a pulsed biasing voltage.
4. A method according to claim 3 wherein the pulsed biasing voltage is from about −20V to about −200V.
5. A method according to claim 3 wherein the pulsed biasing voltage has a duty cycle from 10% to 90%.
6. A method according to claim 1 where the lithium metal oxide is lithium cobalt oxide.
7. A method according claim 1 wherein (a) comprises evacuating the sputtering chamber to maintain a pressure of less than about 5×10 −5 Torr.
8. A method according to claim 1 wherein the sputtering gas is argon.
9. A method according claim 1 wherein the sputtering gas comprises oxygen.
10. A method according claim 1 wherein (a) comprises providing a plurality of substrates that each comprise a mica sheet.
11. A method according claim 1 further comprising depositing a plurality of battery component films on the substrate before or after steps (a) through (e) the films cooperating to form a battery, and the films comprising a current collector and electrolyte, and such that the deposited lithium metal oxide film serves as an cathode.
12. A method according to claim 1 wherein the alternating voltage is applied at a frequency of from about 20 to about 80 kHz.
13. A method according to claim 12 wherein the alternating voltage is applied at a power level of from about 3 kW to about 10 kW.
14. A method according claim 1 wherein the sputtering gas comprises argon and oxygen.
15. A method according claim 14 wherein the argon is maintained at a pressure of from about 1×10 −3 to about 1×10 −2 Torr.
16. A method according claim 14 wherein the oxygen is maintained at a pressure of from about 1×10 −4 to about 5×10 −3 Torr.