Apparatus of reactive cathodic arc evaporator for plating lithium-compound thin film and method thereof

Abstract

An apparatus is provided for plating a lithium (Li)-compound thin film. In the thin film, Li is obtained through thermal evaporation, and titanium (Ti) or other metal by using arc plasma. The elements converted into gas phase are co-deposited in a plasma environment with a reaction gas (oxygen) to be activated as excited atoms or molecules for reaction. In the end, all of the constituent elements are deposited on a substrate to form the Li-compound thin film. Thus, reaction efficiency is high with a fast deposition rate. The composition ratio of each element is independently determined to control its yield according to the requirement. Hence, the present invention greatly enhances the fabrication rate with lowered production cost for applications in the thin-film battery industries.

Claims

1. A method of plating said Li-compound thin film employing an apparatus of reactive cathodic arc evaporator for plating a lithium (Li)-compound thin film, the apparatus integrating thermal evaporation and arc plasma deposition, the apparatus comprising: a deposition chamber comprising a first shutter, a placing plate, and a second shutter located within the deposition chamber; said first shutter corresponding to said placing plate; a substrate is placed on said placing plate; and chemical vapor deposition is processed in said deposition chamber to deposit a Li-compound thin film on said substrate; a vacuum-system piping coupled to said deposition chamber to maintain a vacuum pressure required in said deposition chamber and gases and byproducts are discharged from said deposition chamber after deposition is finished; an arc plasma source disposed in said deposition chamber corresponding to said substrate; and said arc plasma source has a metal target and is externally connected with a plasma power supply; an evaporated-material source disposed in said deposition chamber corresponding to said second shutter; and said evaporated-material source contains a Li metallic material and is externally connected with an evaporation power supply; a gas supply source coupled to said deposition chamber to convey gas into said deposition chamber required during production; and a controller disposed outside said deposition chamber and coupled to said vacuum-system piping, said gas supply source, said evaporation power supply, and said plasma power supply to control production sequence and to adjust a vacuum pressure of said vacuum-system piping, a gas flow of said gas supply source, an evaporation source power of said evaporation power supply, and a plasma source power of said plasma power supply, the method comprising steps of: (a) obtaining the apparatus; (b) disposing said substrate on said placing plate; (c) obtaining and disposing an amount of said Li metallic material in said evaporated-material source; (d) conveying argon as a working gas in said deposition chamber through said gas supply source; (e) using said plasma power supply in said deposition chamber to generate an arc with said arc plasma source at a cathode to process a plasma reaction and hereinafter continuingly maintain said deposition chamber in a stable status of a plasma environment thus obtained; (f) using said evaporation power supply in said deposition chamber to convey a current to said evaporated-material source to process thermal evaporation to said Li metallic material; (g) after obtaining a molten state of a Li metal in said evaporated-material source and keeping evaporating out a Li gas, using said gas supply source to convey and mix oxygen into said working gas to coordinately maintain said plasma reaction; (h) under said stable status of said plasma environment, using said controller to adjust an amount of evaporated Li and an amount of said arc-evaporated metal target according to required compositions and ratios; (i) in accordance with a yield of each reactant including Li, said metal target and oxygen is independently adjusted according to each corresponding required amount of reactant, transforming said each reactant into a gas-phase precursor to be excited and activated in said plasma environment of said deposition chamber to process chemical reaction and co-depositing all of said reactants on said substrate to finally obtain said Li-compound thin film; and (j) disposing said Li-compound thin film in an annealing furnace to process annealing under an atmospheric environment to obtain said Li-compound thin film having a crystalline structure to be used as a cell electrode.

2. The method according to claim 1, wherein the yield of Li is controlled by said controller through adjusting an evaporating rate of Li in said evaporated-material source.

3. The method according to claim 1, wherein the yield of said metal target is controlled by said controller through adjusting a current intensity of said arc plasma source.

4. The method according to claim 1, wherein oxygen is adjusted by said controller to be mixed with said working gas as a reaction gas at a determined ratio to maintain said plasma environment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which

(2) FIG. 1 is the view showing the preferred embodiment according to the present invention;

(3) FIG. 2 is the flow view showing the fabrication of the lithium (Li)-compound thin film;

(4) FIG. 3 is the sectional view showing the product;

(5) FIG. 4 is the view showing the charging/discharging curves of the Li/titanium (Ti)/oxygen (O) thin-film batteries;

(6) FIG. 5 is the view showing the cycling-characteristic curves of the Li/Ti/O thin-film batteries.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(7) The following description of the preferred embodiment is provided to understand the features and the structures of the present invention.

(8) Please refer to FIG. 1 to FIG. 5, which are a view showing a preferred embodiment according to the present invention; a flow view showing the fabrication of a Li-compound thin film; a sectional view showing a product; a view showing the charging/discharging curves of Li/Ti/O thin-film batteries; a view showing the cycling-characteristic curves of Li/Ti/O thin-film batteries. As shown in the figures, the present invention is an apparatus of reactive cathodic arc evaporator for plating a Li-compound thin film, comprising a deposition chamber 10, a vacuum-system piping 11, an arc plasma source 12, an evaporated-material source 13, a gas supply source 14 and a controller 15.

(9) Within the plating chamber 10, a first shutter 101, a placing plate 102 and a second shutter 103 are allocated. A window port 104 is set on a side wall of the deposition chamber 10. The first shutter 101 is corresponding to the placing plate 102. A substrate 1 is placed on the placing plate 102. The plating chamber 10 is used to process chemical vapor deposition within to deposit a Li-compound thin film on the substrate 1.

(10) The gas supply source 11 is coupled to the deposition chamber 10 to maintain a vacuum pressure required in the deposition chamber 10 and gases and byproducts are discharged after deposition is finished.

(11) The arc plasma source 12 is set in the deposition chamber 10 and is corresponding to the substrate 1. The arc plasma source 12 is set with a metal target 121 and is externally connected with a plasma power supply 122.

(12) The evaporated-material source 13 is set in the deposition chamber 10 and is corresponding to the second shutter 103. The evaporated-material source 13 contains a Li metallic material 131 and is externally connected with an evaporation power supply 132.

(13) The vacuum-system piping 14 is coupled to the deposition chamber 10 to convey gas required, like argon or oxygen, into the deposition chamber 10 during production.

(14) The controller 15 is set outside the deposition chamber 10 and is coupled to the vacuum-system piping 11, the gas supply source 14, the evaporation power supply 132 and the plasma power supply 122 to control production sequence and adjust a vacuum pressure of the vacuum-system piping 11; a gas flow of the gas supply source 14; an evaporation source power of the evaporation power supply 132; and a plasma source power of the plasma power supply 122 for further controlling the gases; the pressures; the required compositions and ratios of the components in the Li-compound thin film; and the deposition rate of the Li-compound thin film to achieve rapidly depositing the Li-compound thin film.

(15) The metal target 121 is Ti, cobalt (Co) or manganese (Mn).

(16) The present invention has a method of depositing the Li-compound thin film, which is characterized in that each component in the composition of the thin film can be independently generated according to required ratios for further combination and composition. Therein, the element of Li is generated by an independently-operated deposition system with the lithium metallic material through thermal evaporation; the element of Ti (or other metal element) is generated by another independently-operated arc plasma system with the metal target through arc evaporation; and oxygen molecules are independently added into the deposition chamber in the form of an oxygen gas. Each reactant of atoms or molecules independently adjusts its own yield according to a required amount and is excited and activated in the plasma environment of the deposition chamber 10 to process reaction and to be deposited on the substrate 1 in the end.

(17) Next, in FIG. 2, a flow view of a method of the present invention is shown: (a) In step 201, at first, the apparatus according to the present invention is provided. (b) In step 202, the substrate 1 is put on the placing plate 102. (c) In step 203, a weighed proper amount of the Li metallic material 131 is put in an evaporating dish (tungsten boat) of the evaporated-material source 13. (d) In step 204, argon is conveyed as the working gas in the deposition chamber 10 through the gas supply source 14. (e) In step 205, the plasma power supply 122 in the deposition chamber 10 is used to generate arc with the arc plasma source 12 at a cathode to process plasma reaction and hereinafter continuingly maintain the deposition chamber 10 in a stable status of a plasma environment thus formed. (f) In step 206, the evaporation power supply 132 in the deposition chamber 10 is used to convey a current to the evaporating dish of the evaporated-material source 13 to process thermal evaporation to the Li metallic material 131. (g) In step 207, after forming a molten state of a Li metal in the evaporating dish and keeping evaporating out a Li gas, the gas supply source 14 is used to convey and mix oxygen into the working gas (argon) to coordinately maintain the plasma reaction. (h) In step 208, under the stable status of the plasma environment, the controller 15 is used to adjust an amount of evaporated Li and an amount of the arc-evaporated metal target 121 according to required compositions and ratios, such as the amount of the material of metallic Ti. (i) In step 209, after the yield of each component of reactants including Li, Ti and oxygen is independently adjusted according to each corresponding required amount, each of the component is transformed into a gas-phase precursor to be excited and activated in the plasma environment of the deposition chamber 10 to process chemical reaction and all of the reactants are co-deposited on the substrate 1 to finally obtain the Li-compound thin film 3, as shown in FIG. 3. (j) In step 210, the Li-compound thin film 3 is put in a high-temperature annealing furnace to process high-temperature annealing under an atmospheric environment. Thus, the Li-compound thin film 3 obtains a good crystalline structure to be used as a cell electrode having a good charging/discharging feature.

(18) The apparatus according to the present invention has very stable and flat charging/discharging voltages, as shown in FIG. 4; and the battery has coulombic efficiencies still remained at 100 percent after 100 cycles of charging and discharging, as shown in FIG. 5.

(19) The present invention has the following advantages: (1) The preparation of a metallic oxide target, such as lithium cobalt oxide (LiCoO.sub.2), lithium manganese oxide (LiMn.sub.2O.sub.4) or lithium phosphorus oxide (Li.sub.3PO.sub.4), in advance is not necessary. (2) The method of manufacturing a thin film through radio frequency (RF) magnetron sputtering is abandoned. Instead, thermal evaporation and an arc plasma method are combined to excite the material like Li, Ti, Co or Mn in a plasma environment to form excited atoms or molecules for further chemical reactions. Hence, the reaction efficiency is high with the deposition rate increased dramatically, which specifically improves the shortcomings of the conventional electrode plating method for Li thin-film batteries. Thus, the apparatus according to the present invention fast fabricates the Li-compound thin film through deposition. Not only the in-advance preparation of the metallic oxide target required in the conventional method is omitted; but also thin film is not obtained through the RF magnetron sputtering which is slow in fabrication. The present invention provides an apparatus of reactive cathodic arc evaporator for plating a Li-compound thin film, whose fabrication rate is about 616 times to that of the conventional RF magnetron sputtering. Therefore, the fabrication time for plating the Li-compound thin film is greatly saved with production cost reduced and production rate improved, which is of great help to large-scale commercial production for Li thin-film battery industries. This offers a great competitive edge to power supply of wearable devices, which can be applied to wearable electronics and small medical products.

(20) To sum up, the present invention is an apparatus of reactive cathodic arc evaporator for plating a Li-compound thin film, where, for the different components of a Li compound, thermal evaporation and arc are used for the materials in the Li compound to be fast evaporated separately to become precursors of thin-film reactions and, in a plasma environment built by the system, the precursors are activated with gases added to process the chemical reactions for being further co-deposited on a substrate to form a Li-compound thin film in the end; and, regarding the applications in the Li thin-film battery industries, the apparatus according to the present invention greatly improves the fabrication rate of the thin film with production cost reduced as well.

(21) The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.