Free-standing lithium phosphorus oxynitride think films and methods of their manufacture
Methods and articles of manufacture for free-standing lithium phosphorus oxynitride (LiPON) thin films are disclosed. The methods facilitate synthesizing the LiPON thin films in a free-standing form with controllable film thicknesses and areas. The free-standing LiPON thin films, absent a solid substrate contacting the LiPON thin films, enable studying fundamental properties of LiPON thin films including mechanical properties and glassy transition behavior. In some embodiments, the method includes modifying a surface of a substrate, forming a layer of LiPON on the modified surface of the substrate, and separating the layer of LiPON from the substrate. The free-standing LiPON thin films, no longer requiring solid substrates, may be used in applications requiring an ionically conductive or electronically insulating coating, film, or barrier layer.
1. A method, comprising:
modifying a surface of a substrate;
forming a layer of lithium phosphorus oxynitride (LiPON) on the modified surface of the substrate; and
separating the layer of LiPON from the substrate.
2. The method of claim 1 , wherein the layer of LiPON separated from the substrate is a free-standing and flexible thin-film layer.
3. The method of claim 1 , wherein modifying the surface of the substrate comprises depositing a sacrificial layer on the surface of the substrate, the sacrificial layer including a first removal rate greater than a second removal rate of the layer of LiPON.
4. The method of claim 3 , wherein separating the layer of LiPON from the substrate includes selectively removing the sacrificial layer between the surface of the substrate and the layer of LiPON.
5. The method of claim 3 , wherein the sacrificial layer comprises a photoresist, and wherein modifying the surface of the substrate comprises coating the surface of the substrate with the photoresist.
6. The method of claim 5 , wherein coating the surface of the substrate with the photoresist comprises:
applying the photoresist on the surface of the substrate; and
rotating the substrate with the photoresist at speeds ranging from 500 revolutions per minutes (RPM) to 2,000 RPM for durations ranging from 40 seconds to 80 seconds.
7. The method of claim 6 , further comprising:
exposing, after rotating the substrate with the photoresist, the photoresist to ultraviolet (UV) light.
8. The method of claim 5 , wherein separating the layer of LiPON comprises dissolving the photoresist using a solvent that selectively removes the photoresist.
9. The method of claim 8 , wherein the photoresist includes AZ1512 and the solvent includes dimethyl carbonate (DMC), and wherein dissolving the photoresist includes immersing the substrate with the layer of LiPON in a solution including DMC for twelve (12) hours.
10. The method of claim 1 , wherein forming the layer of LiPON comprises depositing a LiPON thin film by radio frequency (RF) sputtering a target of Li 3 PO 4 in a nitrogen (N 2 ) environment.
11. The method of claim 10 , wherein RF sputtering the target of Li 3 PO 4 comprises at least one of:
setting the RF power to 50 W with minimal reflected power;
setting the N 2 gas pressure at 15 mTorr; or
maintaining a distance between the target and the substrate at 5 cm.
12. The method of claim 11 , wherein a deposition rate of the LiPON thin film corresponds to approximately 3 nm per minutes.
13. A lithium phosphorus oxynitride (LiPON) layer, comprising:
a first surface; and
a second surface opposite to the first surface, wherein both the first and second surfaces are not in contact with an external structure.
14. The LiPON layer of claim 13 , wherein at least a portion of the LiPON layer is a free-standing and flexible thin-film layer.
15. The LiPON layer of claim 13 , wherein at least a portion of the LiPON layer has a thickness of approximately 3.7 micrometers (μm).
16. The LiPON layer of claim 13 , wherein at least a portion of the LiPON layer partially transmits visible lights and is flexible to bend responding to external force.
17. A method, comprising:
coating a surface of a glass substrate with a layer of photoresist;
depositing a layer of lithium phosphorus oxynitride (LiPON) on the layer of photoresist;
immersing the glass substrate carrying the layer of photoresist and the layer of LiPON in a solution configured to selectively dissolve the layer of photoresist; and
lifting the layer of LiPON from the solution.
18. The method of claim 17 , wherein coating the surface of the glass substrate with the layer of photoresist includes:
applying the photoresist on the surface of the glass substrate;
rotating the substrate with the photoresist at speeds ranging from 500 revolutions per minutes (RPM) to 2,000 RPM for durations ranging from 40 seconds to 80 seconds; and
exposing, after rotating the glass substrate with the photoresist, the photoresist to ultraviolet (UV) light.
19. The method of claim 17 , wherein depositing the layer of LiPON on the layer of photoresist includes:
radio frequency (RF) sputtering a target of Li 3 PO 4 in a nitrogen (N 2 ) environment based on setting the RF power to 50 W with minimal reflected power, setting the N 2 gas pressure at 15 mTorr, and maintaining a distance between the target and the glass substrate at 5 cm.
20. The method of claim 17 , wherein the photoresist comprises AZ1512, wherein the solution comprises a solvent including dimethyl carbonates (DMC), and wherein immersing the glass substrate carrying the layer of photoresist and the layer of LiPON in the solution comprises totally submerging the glass substrate carrying the layer of photoresist and the layer of LiPON in the solution for 12 hours.