Deposition of LiCoO
In accordance with the present invention, deposition of LiCoO 2 layers in a pulsed-dc physical vapor deposition process is presented. Such a deposition can provide a low-temperature, high deposition rate deposition of a crystalline layer of LiCoO 2 with a desired <101> or <003> orientation. Some embodiments of the deposition address the need for high rate deposition of LiCoO 2 films, which can be utilized as the cathode layer in a solid state rechargeable Li battery. Embodiments of the process according to the present invention can eliminate the high temperature (>700° C.) anneal step that is conventionally needed to crystallize the LiCoO 2 layer.
1. A method of depositing a LiCoO 2 layer, comprising:
placing a substrate in a reactor;
flowing a gaseous mixture including argon and oxygen through the reactor;
applying pulsed DC power to a densified conductive ceramic LiCoO 2 sputter target having a resistivity of about 3 kΩ-10 kΩ, the densified conductive ceramic LiCoO 2 sputter target being positioned opposite the substrate, wherein the conductive ceramic LiCoO 2 sputter target comprises Li and Co oxides, Li and Co metallic additions, and at least one dopant of Ni, Si, or Nb;
applying an RF bias power to the substrate; and
filtering the RF bias power with a narrow-band rejection filter from coupling into the pulsed DC power,
wherein a crystalline layer of LiCoO 2 having a columnar structure is deposited over the substrate.
2. The method of claim 1 , wherein the crystalline layer is <101> oriented.
3. The method of claim 1 , wherein the crystalline layer is <003> oriented.
4. The method of claim 1 , wherein a grain size of the crystalline layer is between about 750 Å and about 1700 Å.
5. The method of claim 1 wherein the substrate is a material chosen from a set comprised of silicon, polymers, glasses, ceramics, and metals.
6. The method of claim 1 , further including preheating the substrate to a temperature of about 200° C.
7. The method of claim 1 , wherein the substrate is a low temperature substrate.
8. The method of claim 7 , wherein the low temperature substrate is one of a set of substrates including glass, plastic, and metal foil.
9. The method of claim 1 , further including forming an oxide layer on the substrate.
10. The method of claim 9 , wherein the oxide layer is a silicon dioxide layer.
11. The method of claim 2 , wherein the crystalline layer is deposited at a rate of greater than about 1 μm per hour.
12. The method of claim 1 , further including depositing a metal layer on the substrate.
13. The method of claim 12 , wherein the metal layer is iridium.
14. The method of claim 1 , further including annealing the crystalline layer with a low thermal budget.
15. The method of claim 12 , further including annealing the LiCoO 2 layer at a temperature of less than or equal to about 500° C.
16. The method of claim 12 , further including annealing the LiCoO 2 layer at a temperature of less than or equal to about 400° C.
17. The method of claim 1 , wherein the thickness uniformity of the crystalline layer of LiCoO 2 has a standard deviation of 3% one-sigma.