JP2009187682A - Method for manufacturing cathode electrode, and method for manufacturing thin film solid lithium-ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a cathode electrode, and a method for manufacturing a thin film solid lithium-ion secondary battery, in which a film-forming speed is improved, and there is no damage by energy of plasma. <P>SOLUTION: By a sputtering method, a target composed of a lithium cobaltate sintered compact is used, while superimposing and applying a high frequency electric power and DC electric power to this target, rare gas is supplied, and the cathode electrode composed of a lithium cobaltate thin film which functions as a negative electrode active material layer for the thin film solid lithium-ion secondary battery is formed under a pressure of 0.1 to 1.0 Pa. The thin film solid lithium-ion secondary battery equipped with this cathode electrode is manufactured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a cathode electrode and a method for producing a thin film solid lithium ion secondary battery.

  In recent years, with the demand for downsizing, thinning, and lightening of devices in various fields such as mobile devices and optical MEMS devices, mainly in electronic devices such as portable devices, along with downsizing of electronic components mounted on devices In addition, a battery as a driving source battery is also required to be reduced in size, thickness, and weight. As such a small, thin, and light battery, a lithium ion secondary battery that has a higher voltage, a larger charge / discharge capacity, and has no adverse effects such as a memory effect as compared with a conventional NiCd battery or the like. Is widely used. In this case, since the influence of noise cannot be ignored in the conventional method in which the power supply is provided externally as a result of lowering the driving voltage of mobile devices, optical MEMS devices, etc., the power supply is provided inside as a micro battery. There are also new demands.

It is known that an active material layer including a Li—Co—O layer as an electrode for a lithium ion secondary battery is manufactured by a sputtering method (see, for example, Patent Document 1). A thin-film solid lithium ion secondary battery usually has a cathode lead electrode layer (negative electrode current collector layer), a cathode electrode layer (negative electrode active material layer), a solid electrolyte thin film layer, an anode electrode layer (positive electrode active material) on a substrate. Layer), an anode lead electrode layer, and a lithium cobalt oxide (LiCoO ₂ ) film as a cathode electrode layer is known to be formed by a sputtering method (see, for example, Patent Document 2).

  In addition, a lithium ion secondary battery is usually provided with a liquid electrolyte in its structure. For this reason, adverse effects due to the leakage of the liquid have occurred, and problems such as battery explosion and ignition due to an element short circuit due to the formation of lithium ion dendrites have been pointed out. As a technique replacing the lithium ion battery provided with the liquid electrolyte, a thin film solid secondary battery provided with a lithium ion-containing solid electrolyte film produced by utilizing a technique such as sputtering and a method for manufacturing the same have been proposed (for example, , See Patent Document 2).

However, when a thin film solid lithium ion secondary battery, particularly a cathode electrode layer containing lithium ions or a solid electrolyte membrane for this secondary battery is produced by a sputtering process, the film formation rate is slow, so the throughput is poor, There is a problem that a film containing lithium, which is a highly volatile material, is damaged by the energy of plasma and yield is low. In order to improve the deposition rate, it is common to increase the sputtering power (RF power). However, it is only possible to introduce RF power to a large target exceeding φ120 mm (113 cm ² ) if only the power supply technology is used. This is inconvenient because the equipment becomes large-scale and the device fabrication cost increases.

JP 2003-288894 A (Claims etc.) JP 2007-103129 A (Claims, paragraph 0029, etc.)

  The inventors of the present invention have a problem in producing a thin film solid lithium ion secondary battery, and the film formation rate is low, or the film is damaged by the plasma energy by increasing the sputtering power during film formation. As a result of various studies on methods for avoiding the above, the present invention has been completed.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and to manufacture a cathode electrode composed of a lithium cobalt oxide thin film that is not damaged by plasma energy by improving the film formation rate with low sputtering power. And a method of manufacturing a thin film solid lithium ion secondary battery provided with the cathode electrode thus obtained.

  In order to solve the above problems, the present inventors have succeeded in improving the film formation rate without increasing the sputtering power. Usually, in general sputtering, when the sputtering power is increased, the electron density in the plasma is improved. The present inventors have obtained from the previous experiments that when the electron density is improved, electrons in the plasma flow toward the substrate and the film on the substrate is damaged. Therefore, when sputtering is performed with high power applied in order to improve the deposition rate, damage to the film increases as the applied power increases. Therefore, in a general method, high-speed film formation and film damage reduction are not compatible.

  The present invention has been made on the basis of the above knowledge, and when a cathode electrode made of a lithium (Li) -based oxide film is formed by a sputtering method, a high frequency (RF) power and a DC power are superimposedly applied to a target. However, the present invention relates to a method of forming a film at a predetermined pressure.

  The manufacturing method of the cathode electrode for the thin film solid lithium ion secondary battery of the present invention uses a target made of a lithium cobaltate sintered body by sputtering, and the RF power and DC power are superposedly applied to the target while diluting. A gas is supplied to form a cathode electrode made of a lithium cobaltate thin film that functions as a negative electrode active material layer for a thin film solid lithium ion secondary battery under a pressure of 0.1 to 1.0 Pa.

  As described above, high-speed film formation and low film damage can be achieved by forming a film while applying RF power and DC power superimposed on the target at a predetermined ratio. Therefore, the throughput is improved and the yield is increased. When the sputtering pressure is less than 0.1 Pa, the surface of the obtained lithium cobalt oxide thin film becomes rough and non-uniform, and when it exceeds 1.0 Pa, the film formation rate is slow, resulting in poor throughput. In addition, there is a problem that a film containing lithium (Li), which is a highly volatile material, is damaged by plasma energy and yield is low.

  In the method for producing a thin film solid lithium ion secondary battery of the present invention, a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte thin film layer, a negative electrode active material layer, and a negative electrode current collector layer are arranged in this order on a substrate. In the method of manufacturing a thin film solid lithium ion secondary battery that is laminated in the reverse order, a negative electrode active material layer is formed by sputtering using a target made of a lithium cobaltate sintered body, and RF RF is applied to this target. A rare gas is supplied while power and DC power are superimposed, and a cathode electrode made of a lithium cobalt oxide thin film functioning as a negative electrode active material layer is formed under a pressure of 0.1 to 1.0 Pa. To do.

  When the sputtering pressure is less than 0.1 Pa, the surface of the obtained electrolyte thin film becomes rough and non-uniform, and when it exceeds 1.0 Pa, the deposition rate is slow, resulting in poor throughput. There is a problem in that a film containing lithium (Li), which is a highly volatile material, is damaged by plasma energy and yield is low.

  In the manufacturing method of the thin film solid lithium ion secondary battery, when the solid electrolyte thin film layer is further formed, a rare gas and a nitrogen gas are supplied by an RF sputtering method under a pressure of 0.1 to 1.0 Pa. A solid electrolyte thin film layer comprising a nitrogen-substituted lithium phosphate thin film is formed.

  When the sputtering pressure is within the above range, high speed film formation and low film damage can be achieved. Therefore, the throughput is improved and the yield is increased. If it is out of the range, the above problems occur.

  In the method of manufacturing the thin film solid lithium ion secondary battery, when the solid electrolyte thin film layer is further formed, the target and the backing plate installed on the ceiling portion of the vacuum chamber and the back surface of the backing plate are provided. A cathode, a magnet disposed in the cathode, a substrate mounting stage disposed below the vacuum chamber so as to face the target, a lower portion of a side surface of the backing plate, and a thickness of the target A first shield plate comprising a ground shield provided opposite to the peripheral portion of the direction and the peripheral edge of the bottom surface of the backing plate, and an upper shield plate provided facing and spaced from the ground shield; A diameter larger than the diameter of the bottom surface of the backing plate, which is installed under the first deposition preventive plate so as to surround the film formation space. A parallel plate type magnetron sputtering apparatus having a second elevating and lowering-adhering plate having an upper end of the second adhering plate when the film is formed, and the earth shield and the upper adhering plate. And a gap of 1 to 3 mm is provided between the upper end of the second anti-adhesion plate and the upper anti-adhesion plate, and the second anti-adhesion plate Using a parallel plate type magnetron sputtering apparatus configured such that a gap larger than a gap between the upper end portion and the upper protective plate is provided between the upper end portion and the earth shield, by a sputtering method, Using a target composed of a lithium phosphate sintered body, supplying a rare gas and a nitrogen gas while applying RF power to the target, from a nitrogen-substituted lithium phosphate thin film under a pressure of 0.1 to 1.0 Pa Solid electrolyte And forming a membrane layer.

  If the gap provided between the upper end portion of the second deposition plate and the upper deposition plate is less than 1 mm, abnormal discharge may occur between the second deposition plate and the upper deposition plate. . If it exceeds 3 mm, the plasma may escape from the gap during sputtering. In addition, if the gap between the upper end of the second deposition preventing plate and the ground shield is equal to or smaller than the gap of 1 to 3 mm, the process gas may not be supplied to the vicinity of the target, and plasma may not be formed. There is. Therefore, a desired solid electrolyte thin film layer cannot be formed. Further, when the sputtering pressure is less than 0.1 Pa, the surface of the obtained electrolyte thin film becomes rough and non-uniform, and when it exceeds 1.0 Pa, the film formation rate is slow, resulting in poor throughput. In addition, there is a problem that a film containing lithium (Li), which is a highly volatile material, is damaged by plasma energy and yield is low.

  The method for producing a thin film solid lithium ion secondary battery of the present invention also includes forming a negative electrode current collector layer made of Pt and Ti on a substrate by a DC sputtering method, and forming lithium cobalt oxide on the negative electrode current collector layer. While applying RF power and DC power to the target in a superimposed manner, a rare gas is supplied by a sputtering method, and a negative electrode active material layer that is a cathode electrode made of a lithium cobalt oxide thin film is formed under a pressure of 0.1 to 1.0 Pa. A solid electrolyte thin film layer made of a nitrogen-substituted lithium phosphate thin film is formed on the negative electrode active material layer by supplying a rare gas and a nitrogen gas by RF sputtering under a pressure of 0.1 to 1.0 Pa. A positive electrode active material layer made of Li is formed on the solid electrolyte thin film layer by a vacuum deposition method, or V or V and Li are formed by a reactive sputtering method. To form the cathode active material layer made of an oxide film obtained from the Ranaru alloy and oxygen, then and forming a positive electrode collector layer made of Ni or Cu by DC sputtering.

  The method for producing a thin film solid lithium ion secondary battery of the present invention also includes forming a negative electrode current collector layer made of Pt and Ti on a substrate by a DC sputtering method, and forming lithium cobalt oxide on the negative electrode current collector layer. While applying RF power and DC power to the target in a superimposed manner, a rare gas is supplied by a sputtering method, and a negative electrode active material layer that is a cathode electrode made of a lithium cobalt oxide thin film is formed under a pressure of 0.1 to 1.0 Pa. When forming a solid electrolyte thin film layer on the negative electrode active material, a target and backing plate installed on the ceiling of the vacuum chamber, a cathode provided on the back of the backing plate, and the cathode A magnet disposed therein, a substrate mounting stage disposed opposite to the target below the vacuum chamber, and the backing The lower part of the side surface of the mounting plate, the peripheral part in the thickness direction of the target, and the ground shield provided facing the peripheral part of the bottom surface of the backing plate, and the upper part provided facing the ground shield and spaced apart from each other A first deposition plate made of a deposition plate, and a lower diameter of the first deposition plate, which is installed so as to surround the film formation space and has a diameter larger than the diameter of the bottom surface of the backing plate. A parallel plate type magnetron sputtering apparatus having a second deposition plate, wherein the second deposition plate has its upper end formed by the earth shield and the upper deposition plate at the time of film formation. It is comprised so that it may protrude in an opening part, A 1-3mm clearance gap is provided between the upper end part of this 2nd adhesion prevention board, and an upper adhesion prevention board, and the upper end part of this 2nd adhesion prevention board, and earth | ground The upper end between the shield Using a parallel plate magnetron sputtering device configured to provide a gap larger than the gap between the upper deposition prevention plate and a target made of a lithium phosphate sintered body by sputtering, this target While applying RF power, a rare gas and a nitrogen gas are supplied to form a solid electrolyte thin film layer made of a nitrogen-substituted lithium phosphate thin film under a pressure of 0.1 to 1.0 Pa. On the solid electrolyte thin film layer In addition, a positive electrode active material layer made of Li is formed by a vacuum vapor deposition method, or a positive electrode active material layer made of an oxide film obtained from an alloy of V or V and Li and oxygen is formed by a reactive sputtering method. Then, a positive electrode current collector layer made of Ni or Cu is formed by a DC sputtering method.

  According to the cathode electrode manufacturing method of the present invention, it is possible to improve the deposition rate with a low sputtering power and to form a cathode electrode that is not damaged by plasma energy.

  Moreover, according to the manufacturing method of the thin film solid lithium ion secondary battery of this invention, there exists an effect that the secondary battery without the liquid leakage which is reduced in size, thickness, and weight can be manufactured.

  According to the present invention, the cathode electrode layer can be manufactured using, for example, a parallel plate type magnetron sputtering apparatus as shown in FIG.

The magnetron sputtering apparatus 1 has a cylindrical vacuum chamber 11. The vacuum chamber 11 is provided with an exhaust port 12. The exhaust port 12 is connected to a TMP vacuum exhaust system (not shown). When this vacuum exhaust system is driven, the inside of the vacuum chamber 11 can be exhausted to a high vacuum. It is configured to be able to. Further, the vacuum chamber 11 is provided with a gas inlet 13, and the gas inlet 13 is connected to a gas inlet system (not shown), and a process made of a rare gas (for example, Ar) in the vacuum chamber 11. It is configured so that gas can be introduced. A cylindrical backing plate 14 is installed on the ceiling of the vacuum chamber 11 so as to be insulated from the vacuum chamber. The surface of the backing plate on the inner side of the vacuum chamber 11 is made of a LiCoO ₂ sintered body. A desired cylindrical target 15 is provided. Further, although not shown, a vacuum gauge (ion gauge) is provided on the side wall of the vacuum chamber 11.

  Inside the vacuum chamber 11, an earth shield 16 a is disposed so as to face the peripheral portion of the lower portion of the side surface of the backing plate 14, the peripheral portion in the thickness direction of the target 15, and the peripheral portion of the bottom surface of the backing plate 14, Further, an upper shield (upper protection plate) 16b is disposed facing the earth shield 16a and spaced apart by a predetermined distance. The upper deposition preventing plate 16 b is provided with an opening for supplying the gas introduced from the gas inlet 13 to the film formation space in the vacuum chamber 11. The first deposition plate 16 including the earth shield 16 a and the upper deposition plate 16 b is disposed above the vacuum chamber 11 and is fixed to the upper wall surface of the vacuum chamber 11. The earth shield 16a functions as a jig for adjusting the sputtering to be performed in the opening, and the upper protection plate 16b prevents gas and plasma from leaking out of the first protection plate 16. It functions as a jig for prevention.

  Inside the vacuum chamber 11, a first deposition plate is also provided so that a cylindrical lower shield (second deposition plate) 17 having a diameter larger than the diameter of the bottom surface of the backing plate 14 surrounds the film formation space. 16 is disposed below. The second adhesion preventing plate (lower adhesion preventing plate) 17 is configured such that the upper end portion 17a can protrude into the opening formed by the earth shield 16a and the upper adhesion preventing plate 16b during film formation. . The gap A between the upper end 17a of the second deposition preventing plate 17 and the upper deposition preventing plate 16b is configured to be a predetermined distance (for example, 1 to 3 mm). By setting such an interval, there is no abnormal discharge between the second protective plate 17 and the upper protective plate 16b, and the plasma does not escape from the gap A. The gap between the upper end portion 17a and the earth shield 16a is configured to be larger than the gap A between the upper end portion 17a and the upper protective plate 16b (for example, 8 to 10 mm). By setting such an interval, the process gas is not directly exhausted but effectively introduced into the first deposition preventing plate.

  Below the inside of the vacuum chamber 11, a stage 18 for placing the substrate S is installed facing the surface of the target 15. The stage 18 is grounded via an insulator 19. Thereby, the impedance of the stage 18 can be increased and damage to the film due to the inflow of electrons from the plasma can be suppressed. A deposition cover 20 made of quartz or the like is provided on the side surface of the stage 18. An earth block 21 may be provided opposite the outer peripheral surface of the deposition cover 20, and this earth block is installed on the bottom surface of the vacuum chamber 11.

  A high frequency power source (RF power source) 22 (a matching box (not shown) is also connected) and a DC power source 23 are connected to the target 15 via the backing plate 14 and the grounding portion. Thereby, high frequency power (RF power) and DC power are superimposed and applied to the target 15 to generate plasma between the target 15 and the first deposition preventing plate 16 so that the target 15 is sputtered. ing.

  A cathode 24 is provided on the back surface of the target 15, that is, the back surface of the backing plate 14, the surface on the atmosphere side opposite to the inside of the vacuum chamber 11, and a rotation magnet for forming magnetic field lines in the cathode 24. A magnet 25 such as is arranged. The magnet 25 is configured to be rotated by a drive source such as a motor (not shown).

  The second deposition preventive plate 17 is fixed to a guide ring 26, and this guide ring is supported by a support member 27 that can be moved up and down, so that the second deposition preventive plate 17 can be moved up and down during transport of the substrate S and during film formation. It is configured. The support member 27 may be surrounded by an adhesion cover (not shown), and is configured such that a gap of 1 to 3 mm is formed between the lower surface of the guide ring 26 and the upper surface of the adhesion cover. Is done. Thereby, abnormal discharge and discharge leakage are suppressed. In FIG. 1, 28 is a mask. In addition, the magnetron sputtering apparatus 1 shown in FIG. 1 may be provided with the component similar to the apparatus shown in the following FIG. 2 suitably according to the objective about the component which is not demonstrated.

  In the parallel plate type magnetron sputtering apparatus 1 configured as described above, a rare gas such as Ar introduced from the gas inlet 13 into the film formation space in the vacuum chamber 11 through the opening of the upper protective plate 16b. Positive ions are attracted by the negative potential applied to the target 15 and collide with the surface of the target 15. By this collision, the atoms of the material constituting the target 15 are sputtered and scattered in the film formation space in the vacuum chamber 11. Particles scattered in the atomic state move according to the cosine law, and some of the scattered particles are ionized by collisions with electrons or the like. In the magnetron sputtering apparatus 1, the direction of such ionized sputtered particles can be controlled to uniformly enter the substrate, thereby forming a uniform thin film.

  According to the embodiment of the present invention, for example, a lithium cobalt oxide thin film can be manufactured as a cathode electrode layer as follows using the parallel plate magnetron sputtering apparatus 1 shown in FIG.

  In the present invention, RF power and DC power are superimposed and applied to the target 15 to manufacture a cathode electrode made of a lithium cobalt oxide thin film. For example, at an RF power as low as 2.5 kW, the deposition rate is low, and the uniformity of the deposited lithium cobalt oxide thin film is also poor. However, as the total power is 2.5 kW, DC power is superimposed on RF power, and the ratio of DC power (DC power / (RF power + DC power)) is increased to 8% or 95%, the film formation rate increases. The film thickness uniformity is improved, and the film thickness distribution can be controlled. In this case, sputter discharge does not occur when the DC power is 100%.

  Further, it is generally known that as the film forming pressure is increased, the probability that the sputtered particles and the process gas molecules collide with each other, and as a result, it becomes difficult for the sputtered particles to enter the substrate. However, the lithium cobalt oxide thin film being formed is easily damaged and re-evaporated by the inflow of electrons in the plasma, resulting in a thin film thickness, resulting in a slow film formation rate. For this reason, it is considered necessary to reduce the plasma density in order to improve the film formation speed, and in addition to the superimposed application of RF power and DC power as described above, as the most effective technique, a low film formation pressure ( For example, a lithium cobaltate thin film is manufactured by 0.1-1.0 Pa).

According to the present invention, a lithium cobalt oxide thin film having a predetermined thickness can be manufactured by magnetron sputtering, for example, by supplying Ar gas under a known process condition and applying RF power and DC power in a superimposed manner. I can do it. For example, it can be performed under conditions of Ar gas (for example, 0 to 100 sccm), predetermined RF power (13.56 MHz), and DC power. That is, a substrate S made of a Si substrate or the like is placed on the stage 18 in the apparatus 1, and RF (13.56 MHz) power is, for example, 0.5 to 2.3 kW, and DC power is 2.0 to 0. .2 kW, and the total power of RF power and DC power is kept constant at 2.5 kW. The flow rate of Ar as a process gas is supplied in the range of 0 to 100 sccm, the gas flow rate is controlled using a mass flow controller, and the pressure outside the second deposition preventing plate 17 measured with a vacuum gauge is 0.1 to 1. Then, sputtering is performed for a predetermined time (for example, 20 minutes) to form a lithium cobaltate (LiCoO ₂ ) thin film on the substrate S. The lithium cobalt oxide thin film is formed on the solid electrolyte thin film layer described below or below the solid electrolyte thin film layer.

  In the method for producing a thin film solid lithium ion secondary battery of the present invention, the method for forming a solid electrolyte thin film can be performed using, for example, a parallel plate type magnetron sputtering apparatus 3 shown in FIG.

The magnetron sputtering apparatus 3 has a cylindrical vacuum chamber 31. The vacuum chamber 31 is provided with an exhaust port 32. The exhaust port 32 is connected to a TMP vacuum exhaust system (not shown), and when the vacuum exhaust system is driven, the inside of the vacuum chamber 31 can be exhausted to a high vacuum. It is configured to be able to. Further, the vacuum chamber 31 is provided with a gas introduction port 33, which is connected to a gas introduction system (not shown), and a rare gas (such as Ar) and N ₂ are contained in the vacuum chamber 31. A process gas composed of a gas can be introduced. A cylindrical backing plate 34 is installed on the ceiling of the vacuum chamber 31 so as to be insulated from the vacuum chamber 31. On the surface of the backing plate inside the vacuum chamber 31, Li ₃ PO ₄ or the like is provided. A desired cylindrical target 35 made of a sintered body is provided.

  Inside the vacuum chamber 31, an earth shield 37 a is disposed so as to face the peripheral portion of the lower portion of the side surface of the backing plate 34, the peripheral portion in the thickness direction of the target 35, and the peripheral portion of the bottom surface of the backing plate 34, In addition, an upper shield (upper protection plate) 37b is disposed facing the earth shield 37a and spaced apart by a predetermined distance. The upper deposition preventing plate 37 b is provided with an opening for supplying the gas introduced from the gas inlet 33 to the film forming space in the vacuum chamber 31. A first deposition plate 37 including an earth shield 37a and an upper deposition plate 37b is disposed above the vacuum chamber 31 and is fixed to the upper wall surface of the vacuum chamber 31 by a jig (ring) 37c. The earth shield 37a functions as a jig for adjusting the sputtering to be performed in the opening, and the upper protection plate 37b prevents gas and plasma from leaking out of the first protection plate 37. It functions as a jig for prevention.

  Also, in the vacuum chamber 31, a first deposition plate is formed so that a cylindrical lower shield (second deposition plate) 38 having a diameter larger than the diameter of the bottom surface of the backing plate 34 surrounds the deposition space. 37 is disposed below. The second deposition plate (lower deposition plate) 38 is configured such that an upper end portion 38a can protrude into the opening formed by the earth shield 37a and the upper deposition plate 37b during film formation. Yes. The gap A between the upper end portion 38a of the second deposition preventing plate 38 and the upper deposition preventing plate 37b is configured to have a predetermined distance (for example, 1 to 3 mm). By setting such an interval, there is no abnormal discharge between the second deposition plate 38 and the upper deposition plate 37b, and the plasma does not escape from the gap A. Further, the gap between the upper end 38a and the earth shield 37a is configured to be larger than the gap A between the upper end 38a and the upper protective plate 37b (for example, 8 to 10 mm). By setting such an interval, the process gas is not directly exhausted but is effectively introduced into the first deposition preventing plate 37.

  In addition, a stage 39 for placing the substrate S is placed below the inside of the vacuum chamber 31 so as to face the surface of the target 35. The stage 39 is grounded via the insulator 40. Thereby, the impedance of the stage 39 can be increased and damage to the film due to the inflow of electrons from the plasma can be suppressed. Moreover, although not shown in figure, the target 35 is connected with a high frequency power source and a matching box between the target 35 and the ground. Thereby, plasma is generated between the target 35 and the first deposition preventing plate 37, and sputtering of the target is performed.

  A cathode 41 is provided on the back surface of the target 35, that is, the back surface of the backing plate 34, the surface on the atmosphere side opposite to the inside of the vacuum chamber 31, and a rotation magnet for forming magnetic lines of force in the cathode 41. A magnet 42 such as is arranged. The magnet 42 is configured to be rotated by a drive source such as a motor (not shown).

  The second deposition-preventing plate 38 is fixed to a guide ring 43, and this guide ring is supported by a support member 44 that can be raised and lowered, so that the second deposition-preventing plate 38 can be lifted and lowered when the substrate S is transported and formed. It is configured. The support member 44 is surrounded by a deposition cover 45. A gap B of 1 to 3 mm is formed between the lower surface of the guide ring 43 and the upper surface of the deposition cover 45 during film formation. Thereby, abnormal discharge and discharge leakage are suppressed.

  In the parallel plate type magnetron sputtering apparatus configured as described above, the positive gas of Ar or the like introduced into the film formation space in the vacuum chamber 31 from the gas introduction port 33 through the opening of the upper protection plate 37b is positive. The ions are attracted by the negative potential applied to the target 35 and collide with the surface of the target 35. Due to this collision, the atoms of the material constituting the target 35 are sputtered and scattered in the film formation space in the vacuum chamber 31. Particles scattered in the atomic state move according to the cosine law, and some of the scattered particles are ionized by collisions with electrons or the like. In the magnetron sputtering apparatus, the direction of such ionized sputtered particles can be controlled and uniformly incident on the substrate to form a uniform thin film.

  According to the present invention, for example, a nitrogen-substituted lithium phosphate thin film is manufactured as follows as a solid electrolyte thin film for a thin film solid lithium ion secondary battery using the parallel plate magnetron sputtering apparatus 3 shown in FIG. I can do it.

  As in the case of the lithium cobalt oxide thin film formation described above, when the film forming pressure is high, the nitrogen-substituted lithium phosphate thin film being formed is easily damaged by the inflow of electrons in the plasma and re-evaporates. The thickness is reduced, and as a result, the deposition rate is reduced. Therefore, a nitrogen-substituted lithium phosphate thin film is produced with a low film formation pressure.

According to the present invention, a nitrogen-substituted lithium phosphate thin film having a predetermined thickness can be manufactured by magnetron sputtering, for example, while supplying Ar gas and N ₂ gas under known process conditions. For example, it can be performed under conditions of Ar gas (for example, 0 to 100 sccm) and N ₂ gas (for example, 0 to 100 sccm) and a predetermined cathode power (for example, 2.5 kW, 13.56 MHz). That is, a substrate S made of Si substrate or the like is placed on the stage 39 in the apparatus 3, RF (13.56 MHz) power is set to 2.5 kW, and the flow rates of Ar and N ₂ as process gases are set to 0. The gas flow is controlled in a range of ˜100 sccm, the gas flow rate is controlled using a mass flow controller, and the pressure outside the second deposition plate 38 measured by the vacuum gauge 36 is 0.1˜1.0 Pa (deposition of the present invention). Then, sputtering is performed for a predetermined time (for example, 60 minutes), and a nitrogen-substituted lithium phosphate (LiPON) thin film is formed on the substrate S. This LiPON thin film is formed under or on the cathode electrode described above.

  A thin film solid lithium ion secondary battery provided with a lithium cobaltate thin film and a nitrogen-substituted lithium phosphate thin film formed as described above has a cathode lead electrode layer (negative electrode current collector layer), a cathode electrode layer on a substrate. (Negative electrode active material layer, for example, lithium cobaltate thin film), solid electrolyte thin film layer (for example, nitrogen-substituted lithium phosphate thin film), anode electrode layer (positive electrode active material layer), anode lead electrode layer in this order or vice versa For example, it is manufactured as follows using a stainless steel mask of a predetermined shape.

For example, a cathode lead electrode made of Pt (100 nm) and Ti (20 nm) is formed on a substrate made of glass or the like under a known process condition by DC sputtering, and the RF power and DC power described above are formed thereon. A LiCoO ₂ (2.0 μm) film is formed by a sputtering method performed by superimposing and applying heat deposition (300 to 600 ° C.) by heat treatment to improve the crystallinity of the film, A cathode electrode made of the heat-treated film is formed, and a solid electrolyte thin film layer (1.0 μm) made of a nitrogen-substituted lithium phosphate thin film is formed on the cathode electrode by the above-described RF sputtering method. On the thin film layer, an electrode made of Ni or Cu (250 to 300 nm) is formed by a DC sputtering method under known process conditions. A node lead electrode and an anode electrode are formed.

  Hereinafter, the present invention will be described in detail based on examples.

1 is a parallel plate magnetron sputtering apparatus 1 shown in FIG. 1, in which a target 15 made of a LiCoO ₂ sintered body having a diameter of 300 mm and a thickness of 5 mm is installed, and the distance between the target 15 and the substrate S (φ = 200 mm) is set. Using the apparatus set to 60 mm, the film-forming process of the lithium cobalt oxide thin film was implemented.

A □ 200 mm Si substrate is placed on the stage 18 (water-cooled) in the above apparatus, and the FR power is 2.5 to 2.5 so that the sum of RF (13.56 MHz) power and DC power is 2.5 kW. Within a range of 0.5 kW, DC power is varied within a range of 0-2.0 kW, the flow rate of Ar as a process gas is set to 49 sccm, the deposition pressure is set to 0.8 Pa, and Sputtering was performed under the condition that the film formation time was 20 minutes, and a lithium cobaltate (LiCoO ₂ ) thin film was formed on the substrate S.

  FIG. 3 shows the film thickness (nm) distribution of the lithium cobalt oxide thin film formed on the substrate S in accordance with the film formation process. In FIG. 3, the curves are respectively (a) RF 2.5 kW (DC power ratio = 0%), (b) RF 2.3 kW + DC 0.2 kW (DC power ratio = 8%), and (c) RF 2.0 kW + DC 0.5 kW ( (DC power ratio = 20%), (d) RF 1.7 kW + DC 0.8 kW (DC power ratio = 32%), (e) RF 1.5 kW + DC 1.0 kW (DC power ratio = 40%), (f) RF 1.25 kW + DC 1.25 kW (DC power ratio = 50%), (g) RF 1.1 kW + DC 1.4 kW (DC ratio = 56%), (h) RF 1.0 kW + DC 1.5 kW (60%), (i) RF 0.5 kW + DC 2.0 kW (DC power ratio) = 80%) is applied. FIG. 4 shows the influence of the DC power ratio (%) on the deposition rate (nm / min) and film thickness uniformity (%) of the thin film.

  As is apparent from FIGS. 3 and 4, as the DC power ratio increases from 0% to 80%, the film forming speed is improved and the film thickness distribution can be controlled. .

  Furthermore, the DC power ratio is discharged to 95%, the deposition rate shows the same tendency as in the case of 80% or less, and is proportional to the DC power ratio, and the film thickness uniformity is also 80% or less. Similarly, it was confirmed that it was good, but in the case of 100%, sputter discharge did not occur. The DC power ratio may be appropriately selected in consideration of the film thickness distribution, depending on what deposition rate is intended.

  In this example, the RF power was kept constant (2.0 kW), and the DC power superimposed thereon was varied (0.2 to 0.8 kW), and the film forming process of Example 1 was repeated.

  The distribution of the film thickness (nm) of the lithium cobaltate thin film thus formed on the substrate S is shown in FIG. In FIG. 5, the curves are respectively (a) RF 2.0 kW (DC power ratio = 0%), (b) RF 2.0 kW + DC 0.2 kW (DC power ratio = 9.1%), and (c) RF 2.0 kW + DC 0. The result when power of 5 kW (DC power ratio = 20%) and (d) RF 2.0 kW + DC 0.8 kW (DC power ratio = 28.6%) is applied is shown. FIG. 6 shows the influence of the total power (kW) of RF power and DC power on the deposition rate (nm / min) and film thickness uniformity (%) of the thin film.

As can be seen from FIGS. 5 and 6, as the DC power ratio and the total power increase, the deposition rate increases and the film thickness distribution can be controlled.
(Comparative Example 1)

  In this comparative example, the RF power was 2.0 kW, 2.2 kW, and 2.5 kW, and the film formation process of Example 1 was repeated without superimposing DC power on this.

  Thus, the distribution of the deposition rate (nm / min) and film thickness uniformity (%) of the lithium cobalt oxide thin film formed on the substrate S is the result obtained in Example 2 (RF 2.0 kW + DC 0.2 kW, RF 2.0 kW + DC0). FIG. 7 shows a comparison with .5 kW, RF 2.0 kW + DC 0.8 kW). In FIG. 7, each curve shows (a) the deposition rate (nm / min) when RF power + DC power is superimposed and applied in Example 2, and (b) the deposition rate when RF power is applied in this comparative example. (Nm / min), (c) Film thickness uniformity (%) when RF power + DC power is superimposed and applied in Example 2, (d) Film thickness uniformity when RF power is applied in this comparative example (%) %).

  As is apparent from FIG. 7, when the deposition rate and the film thickness uniformity are compared between the case where RF power + DC power is applied in a superimposed manner and the case where the same RF power as the total power is applied, deposition is performed when the superimposed application is performed. It can be seen that the speed is high and the film thickness uniformity is good. However, simply increasing the total power does not necessarily improve the film thickness uniformity.

In the parallel plate type magnetron sputtering apparatus 3 shown in FIG. 2, the gap between the upper end portion 38a of the second deposition preventing plate 38 and the upper deposition preventing plate 37b is approximately 2 mm. A device configured such that the gap between the upper end portion 38a of the landing plate 38 and the earth shield 37a is larger than the gap between the upper end portion 38a and the upper deposition preventing plate 37b (8 to 10 mm) was used. Using this apparatus, a target 35 made of a Li ₃ PO ₄ sintered body having a diameter of 300 mm and a thickness of 5 mm was set, and the distance between the target 35 and the substrate S (φ = 200 mm) was set to 150 mm. A thin film deposition process was performed.

In the above apparatus, the Si substrate on which the cathode electrode was produced according to Example 1 was placed on a stage 39 (water-cooled), the RF (13.56 MHz) power was set to 2.5 kW, and Ar and N as process gases The flow rate of ₂ is varied in the range of 0 to 100 sccm, the flow rate of the process gas is controlled using a mass flow controller, the deposition pressure is varied in the range of 0.1 to 2.0 Pa, and the deposition time Was sputtered for 60 minutes to form a nitrogen-substituted lithium phosphate (LiPON) thin film on the substrate S. It was confirmed by impedance measurement and SEM that this LiPON thin film was an amorphous film having a function as a solid electrolyte thin film.

  FIG. 8 shows the relationship between the film forming pressure (Pa) and the film forming speed (nm / min) in the film forming process. This film formation speed is the thickness of the LiPON film deposited on the substrate per unit time, and as is apparent from FIG. 8, has a strong dependence on the film formation pressure. It turns out that it improves.

  A gap A of 2 mm is provided between the upper end 38a of the second protective plate 38 and the upper protective plate 37b, and the upper end 38a and the upper protective plate 37b are provided between the upper end 38a and the ground shield 37a. The intended purpose could be achieved by providing a gap (8 to 10 mm) larger than the gap between the two. If the gap A is less than 1 mm, abnormal discharge may occur between the second deposition plate 38 and the upper deposition plate 37b. If it exceeds 3 mm, the plasma may escape from the gap during sputtering.

  When the film formation pressure was 0.07 Pa and the film formation process was performed in the same manner as described above, the film formation speed was improved, but the SEM of the substrate cross section shown in FIGS. As apparent from the photograph, it can be seen that the surface of the deposited LiPON thin film is formed in a rough state. FIG. 9A is an SEM photograph in which the substrate cross section is tilted 20 degrees toward the front, and FIG. 9B is a cross sectional SEM photograph. Although the film was formed in such a rough surface, the flow of electrons into the substrate was suppressed by the low pressure, but the incident energy of ions per unit quantity increased. In addition, it is considered that damage to the film occurred due to the increase in the energy of the sputtered particles.

  FIGS. 10A and 10B show SEM photographs of the cross section of the substrate in order to observe the surface state of the LiPON thin film obtained when the film forming pressure is 0.1 Pa. FIG. 10A is an SEM photograph with the substrate cross section tilted 20 degrees toward the front, and FIG. 10B is an SEM photograph of the cross section. From these figures, it can be seen that the surface of the deposited LiPON thin film is flat and uniform.

  Thus, considering a practical film formation rate (preferably, 8 nm / min or more), the optimum pressure for forming the LiPON film without causing damage to the surface is in the range of 0.1 to 1.0 Pa. I understand that.

  In this example, a thin film solid lithium ion secondary battery was manufactured. All film formation was performed by in-situ mask film formation (patterning film formation) using a stainless steel mask having a predetermined shape.

A negative electrode current collector layer made of Pt (film thickness: 100 nm) and Ti (film thickness: 20 nm) was formed on a substrate (SiO ₂ / Si) by a DC sputtering method under known process conditions. On this negative electrode current collector layer, a rare gas was supplied by a sputtering method while applying RF power and DC power to a lithium cobalt oxide target in accordance with the process conditions described in Example 1, and a pressure of 0.8 Pa was applied. Below, the negative electrode active material layer (2.0 micrometers) which is a cathode electrode which consists of a lithium cobaltate thin film was formed in 300-600 degreeC heating atmosphere. On this negative electrode active material, a rare gas and nitrogen gas were supplied while applying RF power to this target by sputtering using a target made of a lithium phosphate sintered body according to the process conditions described in Example 3. Then, a solid electrolyte thin film layer (film thickness: 1.0 μm) composed of a nitrogen-substituted lithium phosphate thin film was formed under a pressure of 0.1 Pa. On this solid electrolyte thin film layer, a positive electrode active material layer made of Li is formed by a vacuum deposition method under known process conditions, or obtained from an alloy made of V or V and Li and oxygen by a reactive sputtering method. A positive electrode active material layer made of an oxide film was formed. Next, a positive electrode current collector layer (film thickness: 250 to 300 nm) made of Ni or Cu was formed by a DC sputtering method under known process conditions. Thus, the lithium cobalt oxide thin film and the nitrogen-substituted lithium phosphate thin film containing lithium, which is a highly volatile material, are not damaged by the energy of the plasma, and are formed at a high yield with a high deposition rate. An ion secondary battery was obtained.

  According to the present invention, the cathode electrode thin film and the solid electrolyte thin film, which are not damaged by the plasma energy, can be formed at a specific sputtering power and at a high film forming speed under a low film forming pressure. It can be used in the field of secondary batteries.

The typical block diagram which shows one structural example of the parallel plate type magnetron sputtering device used for the cathode electrode thin film manufacturing method of this invention. The typical block diagram which shows one structural example of the parallel plate type magnetron sputtering device used for the manufacturing method of a solid electrolyte thin film in this invention. 3 is a graph showing the distribution of film thickness (nm) of the lithium cobalt oxide thin film formed in Example 1. The graph which shows the influence which DC power ratio has on the deposition rate (nm / min) and film thickness uniformity (%) of a thin film about the lithium cobaltate thin film formed in Example 1. 5 is a graph showing the distribution of film thickness (nm) of the lithium cobalt oxide thin film formed in Example 2. The graph which shows the influence which the total electric power (kW) of RF electric power and DC electric power has on the deposition rate (nm / min) and film thickness uniformity (%) of a thin film formed in Example 2. The graph which shows the deposition rate (nm / min) and film thickness uniformity (%) distribution of the lithium cobalt oxide thin film formed in Comparative Example 1 in comparison with the results obtained in Example 2. The graph which shows the relationship between the film-forming pressure (Pa) and the film-forming speed | rate (nm / min) about the nitrogen substituted lithium phosphate thin film formed in Example 3. FIG. In Example 3, it is a SEM photograph which shows the surface state of the film | membrane obtained at the film-forming pressure of 0.07Pa, (a) is a SEM photograph in the state which inclined the substrate 20 degree | times toward this side, (b) is a cross section SEM photo. In Example 3, it is a SEM photograph which shows the surface state of the film | membrane obtained when the film-forming pressure is 0.1 Pa, (a) is a SEM photograph in the state which inclined the substrate 20 degrees, (b) is a cross section SEM photo.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetron sputter apparatus 11 Vacuum chamber 12 Exhaust port 13 Gas inlet 14 Backing plate 15 Target 16 1st deposition board 16a Earth shield
16b Upper protection plate 17 Second protection plate 17a Upper end portion 18 Stage 19 Insulator 20 Protection cover 21 Earth block 22 High frequency power source 23 DC power source 24 Cathode 25 Magnet 26 Guide ring
27 Support member 28 Mask 3 Magnetron sputtering device 31 Vacuum chamber 32 Exhaust port 33 Gas inlet 34 Backing plate 35 Target 36 Vacuum gauge 37 First deposition plate 37a Earth shield 37b Upper deposition plate 37c Jig 38 Second deposition plate 38a Upper end portion 39 Stage 40 Insulator 41 Cathode 42 Magnet 43 Guide ring 44 Support member 45 Adhesion cover S Substrate A Gap between the upper adhesion plate and the upper end portion of the second adhesion plate B Guide ring and adhesion cover Gap between

Claims (6)

Using a target made of a lithium cobaltate sintered body by sputtering, a rare gas is supplied while RF power and DC power are superimposed on the target, and a thin film solid is applied under a pressure of 0.1 to 1.0 Pa. A method for producing a cathode electrode, comprising forming a cathode electrode composed of a lithium cobaltate thin film functioning as a negative electrode active material layer for a lithium ion secondary battery. A thin film solid lithium ion secondary battery in which a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte thin film layer, a negative electrode active material layer, and a negative electrode current collector layer are stacked in this order or in the reverse order on a substrate. In this manufacturing method, when forming the negative electrode active material layer, a target made of a lithium cobalt oxide sintered body is used by sputtering, and a rare gas is supplied while RF power and DC power are superimposedly applied to the target. And forming a cathode electrode comprising a lithium cobaltate thin film that functions as a negative electrode active material layer under a pressure of 0.1 to 1.0 Pa. 3. The method for manufacturing a thin film solid lithium ion secondary battery according to claim 2, wherein when the solid electrolyte thin film layer is further formed, a rare gas and a nitrogen gas are supplied by an RF sputtering method to a thickness of 0.1 to 1.0 Pa. A method for producing a thin film solid lithium ion secondary battery comprising forming a solid electrolyte thin film layer comprising a nitrogen-substituted lithium phosphate thin film under the pressure of 3. The method of manufacturing a thin film solid lithium ion secondary battery according to claim 2, further comprising: a target and a backing plate installed on a ceiling portion of a vacuum chamber; and a back surface of the backing plate when forming a solid electrolyte thin film layer. A cathode disposed therein, a magnet disposed in the cathode, a substrate placement stage disposed in the vacuum chamber facing the target, and a lower portion of a side surface of the backing plate, A first shield comprising a ground shield provided opposite to a peripheral portion in the thickness direction of the target and a peripheral edge portion of a bottom surface of the backing plate, and an upper deposition preventing plate provided opposite to and spaced from the ground shield. The diameter of the bottom surface of the backing plate, which is installed so as to surround the film formation space below the first deposition plate and the first deposition plate. A parallel plate type magnetron sputtering apparatus having a second elevating plate having a large diameter which can be moved up and down, wherein the upper end portion of the second adhering plate is formed with the earth shield and the upper adhering plate at the time of film formation. And a gap of 1 to 3 mm is provided between the upper end portion of the second anti-adhesion plate and the upper anti-adhesion plate, and the second anti-reflection plate is formed. Sputtering method using a parallel plate type magnetron sputtering apparatus configured such that a gap larger than a gap between the upper end and the upper protective plate is provided between the upper end of the landing plate and the earth shield Using a target composed of a lithium phosphate sintered body, supplying a rare gas and a nitrogen gas while applying RF power to the target, and under a pressure of 0.1 to 1.0 Pa, a nitrogen-substituted lithium phosphate Made of thin film Method of manufacturing a thin film solid state lithium ion secondary battery and forming a body electrolyte thin film layer. A negative electrode current collector layer made of Pt and Ti is formed on a substrate by a DC sputtering method, and RF power and DC power are superimposedly applied to a lithium cobaltate target on the negative electrode current collector layer by a sputtering method. Then, a rare gas is supplied to form a negative electrode active material layer which is a cathode electrode made of a lithium cobaltate thin film under a pressure of 0.1 to 1.0 Pa. On this negative electrode active material layer, an RF sputtering method is used. A rare gas and a nitrogen gas are supplied to form a solid electrolyte thin film layer composed of a nitrogen-substituted lithium phosphate thin film under a pressure of 0.1 to 1.0 Pa. On this solid electrolyte thin film layer, Li is formed by a vacuum deposition method. A positive electrode active material comprising an oxide film obtained from an alloy comprising V or V and Li and oxygen by a reactive sputtering method. To form a layer, then a thin film solid method for producing a lithium ion secondary battery, which comprises forming a positive electrode collector layer made of Ni or Cu by DC sputtering. A negative electrode current collector layer made of Pt and Ti is formed on a substrate by a DC sputtering method, and RF power and DC power are superimposedly applied to a lithium cobaltate target on the negative electrode current collector layer by a sputtering method. Then, a rare gas is supplied to form a negative electrode active material layer which is a cathode electrode made of a lithium cobalt oxide thin film under a pressure of 0.1 to 1.0 Pa, and a solid electrolyte thin film layer is formed on the negative electrode active material In this case, the target and backing plate installed on the ceiling of the vacuum chamber, the cathode provided on the back of the backing plate, the magnet disposed in the cathode, and the lower portion in the vacuum chamber A stage for placing the substrate facing the target, a lower part of the side surface of the backing plate, a circumference in the thickness direction of the target A first shield plate comprising an upper shield plate disposed opposite to and spaced from the ground shield, and a ground shield provided opposite to the peripheral edge portion of the bottom surface of the backing plate; 1. A parallel plate type magnetron sputtering apparatus having a second elevating plate that can be moved up and down and has a diameter larger than the diameter of the bottom surface of the backing plate, which is installed so as to surround the film formation space below the deposition plate. The second protection plate is configured such that an upper end portion of the second protection plate can protrude into an opening formed by the earth shield and the upper protection plate during film formation. A gap of 1 to 3 mm is provided between the upper end portion of the attachment plate and the upper attachment prevention plate, and the upper end portion and the upper attachment prevention plate are provided between the upper end portion of the second attachment attachment plate and the earth shield. So that there is a gap larger than the gap between Using a parallel plate magnetron sputtering apparatus configured, a target composed of a lithium phosphate sintered body is used by sputtering and a rare gas and a nitrogen gas are supplied while RF power is applied to the target. A solid electrolyte thin film layer made of a nitrogen-substituted lithium phosphate thin film is formed under a pressure of 0.1 to 1.0 Pa, and a positive electrode active material layer made of Li is formed on the solid electrolyte thin film layer by a vacuum deposition method, or A positive electrode active material layer made of an oxide film obtained from an alloy made of V or V and Li and oxygen is formed by reactive sputtering, and then a positive electrode current collector layer made of Ni or Cu is formed by DC sputtering. A method for manufacturing a thin film solid lithium ion secondary battery.

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