JP2008270465A - Method of manufacturing micro transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the method of manufacturing a micro transformer, which improves throughput, prevents a crack from entering an insulating film between coils, and the micro transformer can be manufactured without the use of a mask material the selection ratio of which is large. <P>SOLUTION: An insulating film 3 is deposited on the entire surface of a semiconductor substrate 1 on a part of which an impurity diffusion region 2 is formed. A first opening portion 4 and a second opening portion 5 are formed by removing a part of the insulating film 3. Then, a first coil 7 is formed so that a center pad 8 comes into contact with the impurity diffusion region 2 via the first opening portion 4. Then, a thin insulating film 10 is deposited on the first coil 7. An insulator material 12 is pasted onto the insulating film 10 at a first coil side by use of adhesion tape 13. Then, a second coil 15 is formed on the surface of the insulator material 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a microtransformer that performs signal transmission between electrically insulated electrical circuits.

  2. Description of the Related Art Conventionally, there is a method of performing signal transmission between electrically insulated electrical circuits so that a dangerous voltage does not pass when a high voltage such as a surge is applied. One of the methods uses an inductive coupling by a transformer (for example, see Patent Document 1 below).

  Transformers are becoming smaller due to recent developments in MEMS (Micro Electro Mechanical Systems) technology. Therefore, integration of transformers and integrated circuits has become possible. Hereinafter, this small transformer is referred to as a micro-transformer, and a signal transmission system using this micro-transformer is referred to as a micro-transformer (see, for example, Patent Document 2 and Non-Patent Document 1 below).

  FIG. 11 is a cross-sectional view showing the structure of a conventional microtransformer. As shown in FIG. 11, the microtransformer includes a primary coil 7 and a secondary coil 15. The primary coil 7 and the secondary coil 15 are separated from each other by an insulating film 21. Further, in order to ensure a desired electrostatic discharge (ESD) withstand capability, in the conventional microtransformer, the thickness of the insulating film 21 needs to be 10 μm or more.

  Next, steps of a conventional method for manufacturing a microtransformer will be described. 12 to 14 are cross-sectional views sequentially showing steps of a conventional method for manufacturing a microtransformer. First, as shown in FIG. 12, the impurity diffusion region 2 is selectively formed on the semiconductor substrate 1. Next, the insulating film 3 is formed to a thickness of about 1 μm on the entire surface of the substrate by plasma CVD (Chemical Vapor Deposition).

  Next, as shown in FIG. 13, the insulating film 3 is partially removed by a photolithography process or the like, and the first opening 4 and the second opening 5 are formed. Then, a metal film is deposited on the entire surface of the substrate with a thickness of about 3 μm, and the primary coil 7 is formed by a photolithography process or the like. At this time, the center pad 8 of the primary coil 7 is brought into contact with the impurity diffusion region 2 through the first opening 4. Further, a pad 9 electrically connected to the center pad 8 of the primary coil 7 via the impurity diffusion region 2 is formed. Then, the pad 9 is brought into contact with the impurity diffusion region 2 through the second opening 5. Although not shown, an outer end pad is formed on the outer end portion of the primary coil 7.

  Next, as shown in FIG. 14, an insulating film is deposited on the primary coil 7 by plasma CVD or the like. Then, the surface of the insulating film is flattened, and an insulating film 21 having a thickness of about 10 μm is formed. Next, a part of the insulating film 21 is removed by a photolithography process or the like to form an opening. Thus, the pad 9 is exposed in the opening 22. Although not shown, the outer end pad is exposed at an opening other than the region shown in FIG.

  Next, as shown in FIG. 11, a metal film is deposited on the insulating film 21, and the secondary coil 15 is formed by a photolithography process or the like. The shape of the secondary coil 15 is substantially the same as the shape of the primary coil 7. In the secondary coil 15, a center pad 16 is formed at the center portion, and an outer end pad 17 is formed at the outer end portion. Simultaneously with the formation of the secondary coil 15, the opening 22 is covered with a metal film. In this case, the metal film covering the opening 22 comes into contact with the pad 9 and becomes an electrode pad at the center side end of the primary coil 7. Therefore, the signal from the primary coil 7 can be received by the secondary coil 15 and transmitted to the outside from the center pad 16 of the secondary coil 15 and the outer end pad 17 of the secondary coil.

JP 11-196136 A JP 2001-148277 A Matthias Stecher, 6 others, "Key Technologies for the Automotive I Industrial S & E Electronic Energy and Industrial Applications, Inc. ON POWER ELECTRONICS), VOL. 20, NO. 3, May 2005

  However, the conventional manufacturing method described above has a problem in that throughput is reduced because the insulating film 21 needs to be formed thick on the primary coil 7. In addition, since the insulating film 21 is thick, there is a problem that cracks occur in the insulating film 21 due to stress. Further, when part of the insulating film 21 is removed by etching, there is a problem that throughput is lowered. Moreover, when performing this etching, there exists a problem that it is necessary to use a mask material with a large selection ratio.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a microtransformer that can improve the throughput in order to eliminate the above-described problems caused by the prior art. It is another object of the present invention to provide a method of manufacturing a microtransformer that can prevent cracks in the insulating film between coils. Furthermore, an object of the present invention is to provide a method of manufacturing a microtransformer that can be manufactured without using a mask material having a large selection ratio.

  In order to solve the above-described problems and achieve the object, a manufacturing method of a microtransformer according to a first aspect of the invention first forms an impurity diffusion region selectively on the surface of a semiconductor substrate. Next, a first insulating film is deposited on the surface of the semiconductor substrate on which the impurity diffusion region is formed. Then, the first opening and the second opening are respectively formed in the first insulating film so as to reach the impurity diffusion region. Next, a first conductive film is stacked over the first insulating film, the first opening, and the second opening. The first conductive film is processed into a desired shape centering on a portion of the first conductive film above the first opening. Next, a second insulating film is deposited on the first insulating film and the first conductive film. Then, a part of the second insulating film is removed to expose a portion of the first conductive film above the second opening. Next, an insulator material is bonded onto the second insulating film. Then, a second conductive film having a desired shape is formed on the surface of the insulator material.

  According to the first aspect of the present invention, the second insulating film need not be deposited to a thickness necessary for a desired breakdown voltage. Therefore, the throughput in the process of the manufacturing method can be improved. Further, since the second insulating film is thin, it is possible to prevent the second insulating film from being cracked by stress. Further, a flexible material can be used as the insulator material. In this case, the secondary coil can be formed using the primary coil side as the support substrate.

  According to a second aspect of the present invention, there is provided a method for manufacturing a microtransformer according to the first aspect of the present invention, wherein after the second conductive film is processed, a part of the insulator material is removed to obtain the first conductive film. A portion of the film above the second opening is exposed.

  According to the second aspect of the invention, since the insulator material can be processed into a desired size by a laser, it is not necessary to remove a part of the insulator material by etching. Therefore, a decrease in throughput due to etching can be prevented. Moreover, a microtransformer can be manufactured without using a mask material having a high selectivity.

  According to a third aspect of the present invention, there is provided a manufacturing method of a microtransformer according to the second aspect of the present invention, wherein after the second conductive film is processed, the insulating material is made to be larger than the chip size of each completed microtransformer. The edge periphery of the insulator material is removed so as to reduce the size.

  According to the third aspect of the present invention, for example, when a plurality of microtransformers are simultaneously fabricated on a semiconductor wafer, it is possible to prevent the insulator material from being cracked by dicing or the like for separating the microtransformers.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a microtransformer according to the second aspect of the present invention, wherein the second insulating film is processed after the second conductive film is processed and before the insulating material is partially removed. A third insulating film is deposited on the second conductive film. Then, an opening reaching the second conductive film is formed in the third insulating film.

  According to the fourth aspect of the present invention, after the third insulating film is deposited as a protective film on the secondary coil in advance, the insulator material can be processed into a desired size. Therefore, since the third insulating film can be removed together with the insulator material, the throughput in the manufacturing method can be improved.

  According to a fifth aspect of the present invention, there is provided a method of manufacturing a microtransformer according to any one of the first to fourth aspects, wherein the conductor material is formed on the surface of the insulator material in a desired shape. It is characterized by being directly attached.

  According to the fifth aspect of the present invention, for example, the secondary coil can be formed even when the surface of the insulator material is uneven or the insulator material is a flexible material.

  According to a sixth aspect of the present invention, there is provided a method of manufacturing a microtransformer according to the first aspect of the present invention, wherein the size of the insulator material is set to the second size before the insulator material is bonded onto the second insulating film. The opening is processed into a size that does not cover the opening.

  According to the sixth aspect of the present invention, since the insulator material can be processed into a desired size, it is not necessary to remove the insulator material by etching after forming the secondary coil. Therefore, a decrease in throughput due to etching can be prevented. Moreover, a microtransformer can be manufactured without using a mask material having a high selectivity.

  According to the method of manufacturing a microtransformer according to the present invention, there is an effect that throughput can be improved. Further, the present invention has an effect that it is possible to prevent cracks from entering the insulating film between the coils. Furthermore, the present invention has an effect that a macro transformer can be manufactured without using a mask material having a large selection ratio.

  Exemplary embodiments of a process for producing a microtransformer according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment 1)
First, the structure of the microtransformer manufactured by the manufacturing method according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing the structure of a microtransformer manufactured by the manufacturing method according to the first embodiment of the present invention. As shown in FIG. 1, the microtransformer includes a primary coil 7 and a secondary coil 15. The primary coil 7 and the secondary coil 15 are separated from each other by an insulating film 10, an adhesive tape 13, and an insulator material 12. Specifically, the insulating film 10 is made of an insulator such as an oxide, nitride, or polyimide. The insulator material 12 is made of an insulator such as glass, quartz, sapphire, polyimide, or ceramic, and has a plate shape or a sheet shape. The insulator material 12 may be a flexible material. The adhesive tape 13 only needs to have adhesiveness on both surfaces and be resistant to heat applied in a subsequent bonding step. The adhesive tape 13 is specifically a DAF (Die Attach Film) tape or the like.

  An impurity diffusion region 2 is selectively formed on the surface of the semiconductor substrate 1. An insulating film 3 is deposited on the entire surface of the substrate including the impurity diffusion region 2. A first opening 4 and a second opening 5 are formed in the insulating film 3. The first opening 4 is provided at the center of the substrate, and the second opening 5 is provided at the edge of the substrate. The center pad 8 of the primary coil 7 is in contact with the impurity diffusion region 2 through the first opening 4. The pad 9 is in contact with the impurity diffusion region 2 through the second opening 5. The pad 9 is exposed without being covered with the insulating film 10. Therefore, the pad 9 is electrically connected to the center pad 8 of the primary coil 7 through the impurity diffusion region 2 and serves as a lead electrode at the center side end of the primary coil 7. Although not shown in FIG. 1, an outer end pad is provided on the outer end portion of the primary coil 7. For example, the outer end pad is provided in the back of the pad 9 in FIG. This outer end pad is also exposed without being covered with the insulating film 10.

  2-7 is sectional drawing which shows the process of the manufacturing method of the microtransformer concerning Embodiment 1 of this invention in order. First, as shown in FIG. 2, an impurity diffusion region 2 is selectively formed on the surface of the semiconductor substrate 1. The semiconductor substrate 1 is, for example, a silicon substrate. Next, the insulating film 3 is formed on the entire surface of the substrate by plasma CVD or the like. Here, the thickness of the insulating film 3 is suitably about 1 μm, for example. The insulating film 3 is specifically an oxide film, a nitride film, a polyimide film, or the like.

  Next, as shown in FIG. 3, a part of the insulating film 3 is removed by a photolithography process or the like to form a first opening 4 and a second opening 5. Next, a metal film 6 is deposited on the entire surface of the substrate. Here, it is appropriate that the thickness of the metal film 6 is about 1 to 3 μm. Further, the thickness of the metal film 6 is preferably thicker in order to reduce the resistance value of the device. The metal film 6 is in contact with the impurity diffusion region 2 in each of the first opening 4 and the second opening 5.

  Next, the metal film 6 is partially removed by a photolithography process or the like to form the primary coil 7. The shape of the primary coil 7 is, for example, a spiral shape. The planar shape of the spiral may be a circular shape or a cornered shape (for example, a square shape). A center pad 8 is formed at the center of the primary coil 7. Further, an outer end pad (not shown) is formed on the outer end portion of the primary coil. The center pad 8 of the primary coil 7 is in contact with the impurity diffusion region 2 through the first opening 4. Simultaneously with the formation of the primary coil 7, the pad 9 is formed on the second opening 5. The pad 9 is in contact with the impurity diffusion region 2 through the second opening 5.

  Next, as shown in FIG. 4, an insulating film is deposited on the entire surface of the substrate by plasma CVD or the like. Then, this film is polished to flatten the surface, and the insulating film 10 is formed. The thickness of the insulating film 10 is suitably about 0 to 10 μm from the upper surface of the primary coil 7. Thus, the primary coil 7 may not be covered with the insulating film 10. That is, when the insulating film 10 is planarized, the insulating film may be polished until the surface of the primary coil 7 is reached. Next, when the pad 9 and the outer end pad are covered with the insulating film 10, the insulating film 10 on the pad 9 and the outer end pad is partially removed by a photolithography process or the like. As a result, the pad 9 is exposed at the opening 11 and the outer end pad is exposed at the opening (not shown).

  Next, as shown in FIG. 5, the insulating material 12 is bonded to the entire surface of the insulating film 10 on the primary coil side via the adhesive tape 13. The thickness of the insulator material 12 is set to a thickness necessary for the withstand voltage according to the use of the microtransformer. Specifically, the thickness of the insulator material 12 is appropriately about 20 to 200 μm. In the present invention, since the adhesive tape 13 is used, the insulating material 12 and the insulating film 10 on the primary coil side may have some unevenness on the surfaces to be bonded to each other.

  Next, as shown in FIG. 6, a metal film 14 is deposited on the entire surface of the insulator material 12. The thickness of the metal film 14 is suitably about 1 to 3 μm. Further, the thickness of the metal film 14 is preferably larger in order to reduce the resistance value of the device. Next, the metal film 14 is partially removed by a photolithography process or the like, and the secondary coil 15 is formed. The shape of the secondary coil 15 is substantially the same as that of the primary coil 7. A center pad 16 is formed at the center of the secondary coil 15. An outer end pad 17 is formed on the outer end portion of the secondary coil 15.

Next, as shown in FIG. 7, the region 18 covering the pad 9 and the region covering the outer end pad of the primary coil 7 (not shown) of the insulating material 12 and the adhesive tape 13 are respectively removed by a laser or the like. Further, the peripheral edge portion 19 of the insulator material 12 may be removed together with the adhesive tape 13 by a laser or the like. This laser is, for example, an excimer laser, a CO ₂ laser, a UV-YAG (Ultra Violet Yttrium Aluminum Garnet) laser, or the like. By removing the region 18 covering the pad 9 and the region covering the outer end pad of the primary coil 7, the outer end pad of the pad 9 and the primary coil 7 is exposed. Here, for example, when a plurality of microtransformers are manufactured on a semiconductor wafer at the same time, the microtransformers must be separated by dicing or the like. By removing the peripheral edge portion 19 of the insulator material 12, it is possible to prevent the insulator material 12 from cracking during dicing.

  As shown in FIG. 8, after forming the secondary coil 15, the insulating film 20 may be deposited on the entire surface of the substrate by plasma CVD or the like. In this case, the insulating film 20 is partially removed by a photolithography process or the like. Then, the center pad 16 of the secondary coil 15 and the outer end pad 17 of the secondary coil 15 are exposed. Further, as shown in FIG. 9, when the insulator material 12 in the region 18 covering the pad 9 and the region covering the outer end pad of the primary coil 7 is removed by a laser or the like, it is deposited on these. The insulating film 20 is also removed together. As a result, the pad 9 and the outer end pad of the primary coil 7 are exposed.

  As described above, according to the first embodiment, the withstand voltage is secured by the insulator material 12, and therefore the insulating film 10 on the primary coil 7 can be made thinner than the thickness required for the desired withstand voltage. Accordingly, it is possible to prevent a decrease in throughput due to the thick formation of the insulating film 10. Further, since the insulator material 12 is bonded by the adhesive tape 13, no cracks are generated in the insulator material 12 due to stress.

  Furthermore, according to the first embodiment, even when a flexible material is used as the insulator material 12, the primary coil side serves as the support substrate, so that the secondary coil 15 can be formed. On the other hand, when the secondary coil 15 and the primary coil side are bonded together after forming the secondary coil 15 on the insulator material 12, the primary coil side does not become a support substrate. Flexible materials cannot be used. Further, by removing the insulating material 12 with a laser, the pads 9 and the outer end pads of the primary coil 7 are exposed, so that it is not necessary to perform etching for exposing these pads. This can prevent a decrease in throughput due to etching. In addition, since there is no thick insulating film etching step, a microtransformer can be manufactured without using a mask material having a high selectivity.

  Further, according to the first embodiment, since the secondary coil 15 is formed after the insulator material 12 is bonded to the primary coil side, the displacement between the primary coil 7 and the secondary coil 15 can be eliminated. On the other hand, when the secondary coil 15 and the primary coil side are bonded together after forming the secondary coil 15 on the insulator material 12, there is a possibility that a deviation occurs at the moment of bonding due to the presence of the adhesive tape 13. There is. If the positions of the primary coil 7 and the secondary coil 15 are shifted, the signal transmission characteristics are deteriorated. In the present embodiment, since this deviation does not occur, it is possible to reduce the rate of occurrence of defective signal transfer characteristics.

(Embodiment 2)
Next, steps of the method for manufacturing the microtransformer according to the second embodiment of the present invention will be described. Since the structure of the microtransformer manufactured by the manufacturing method according to the second embodiment of the present invention is the same as the structure of the microtransformer manufactured by the manufacturing method according to the first embodiment, description thereof is omitted. The second embodiment differs from the first embodiment in the method of forming the secondary coil 15. In the second embodiment, first, the steps of the manufacturing method shown in FIGS. 2 to 5 described in the first embodiment are performed.

  Next, in the step shown in FIG. 6, the secondary coil 15 having a desired shape is formed on the surface of the insulator material 12 by a direct circuit drawing method in which conductive ink or paste is directly applied or sprayed onto the insulator material 12. . Next, the secondary coil 15 is cured by annealing at about 200 ° C. According to this direct circuit drawing method, the secondary coil 15 is formed by, for example, spraying metal nanoparticle paste ink into a desired shape by a known ink jet technique or the like. Next, as shown in FIG. 7, the region 18 covering the pad 9 of the insulator material 12 and the edge peripheral portion 19 of the insulator material 12 are selectively removed by a laser or the like.

  As described above, according to the second embodiment, it is not necessary to perform etching in order to form the secondary coil 15. The secondary coil 15 can also be formed when the surface of the insulator material 12 on which the secondary coil 15 is formed has some unevenness, or when the insulator material 12 is a flexible material.

(Embodiment 3)
Next, steps of the method for manufacturing the microtransformer according to the third embodiment of the present invention will be described. Since the structure of the microtransformer manufactured by the manufacturing method according to the third embodiment of the present invention is the same as the structure of the microtransformer manufactured by the manufacturing method according to the first embodiment, description thereof is omitted. The third embodiment is different from the first embodiment in the size of the insulator material 12 to be bonded onto the insulating film 10 on the primary coil side. In the third embodiment, first, the steps of the manufacturing method shown in FIGS. 2 to 4 described in the first embodiment are performed. Next, as shown in FIG. 10, the insulator material 12 is processed into a size that does not cover the pad 9 and the outer end pad of the primary coil (not shown). Next, the insulator material 12 is bonded to the insulating film 10 on the primary coil side. Then, as in the first embodiment, the secondary coil 15 is formed.

  As described above, according to the third embodiment, after the secondary coil 15 is formed, it is not necessary to delete a part of the insulator material 12 by etching, laser, or the like. Can be prevented. Further, it is possible to prevent the pad 9 and the insulating film 10 from being damaged by a laser or the like. The third embodiment can be applied to the second embodiment. In that case, the same effect can be obtained.

  In the present invention, the plasma CVD method is used for forming the insulating film, but the present invention is not limited to this. Specifically, any method that can form an insulating film may be used. In the present invention, the photolithography process and the direct circuit drawing method are used for forming the coil. However, the present invention is not limited to this. Specifically, any method that can form a coil may be used. In the present invention, the photolithography process is used to remove the metal film and the insulating film, but the present invention is not limited to this. Specifically, any method that can remove the metal film and the insulating film may be used.

  As described above, the method for manufacturing a microtransformer according to the present invention is useful for the production of a microtransformer that performs signal transmission between electrically insulated electrical circuits. It is suitable for the manufacture of a microtransformer that performs isolated transmission of a control signal indicating conduction and non-conduction and a state signal of a switching element.

2 is a cross-sectional view showing the structure of a microtransformer manufactured by the manufacturing method according to the first embodiment. FIG. FIG. 6 is a cross-sectional view showing a process of the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of forming an insulating film on the secondary coil by the microtransformer manufacturing method according to the first embodiment. FIG. 6 is a cross-sectional view showing a process of forming an insulating film on the secondary coil by the microtransformer manufacturing method according to the first embodiment. It is sectional drawing which shows the process of the manufacturing method of the microtransformer concerning this Embodiment 3. It is sectional drawing which shows the structure of the conventional microtransformer. It is sectional drawing which shows the process of the manufacturing method of the conventional microtransformer. It is sectional drawing which shows the process of the manufacturing method of the conventional microtransformer. It is sectional drawing which shows the process of the manufacturing method of the conventional microtransformer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Impurity diffusion area 3, 10 Insulating film 4 1st opening part 5 2nd opening part 6, 14 Metal film 7 Primary coil 8 Central pad of primary coil 9 Pad 11 Opening part 12 Insulator material 13 Adhesive tape 15 Secondary coil 16 Center pad of secondary coil 17 Outer pad of secondary coil

Claims (6)

An impurity diffusion region forming step of selectively forming an impurity diffusion region on the surface of the semiconductor substrate;
A first insulating film is deposited on the surface of the semiconductor substrate on which the impurity diffusion region is formed, and the first opening and the second opening reach the impurity diffusion region respectively on the first insulating film. A first insulating film deposition step formed in
A first conductive film is stacked on the first insulating film, the first opening, and the second opening, and a portion of the first conductive film above the first opening A first conductive film processing step for processing the first conductive film into a desired shape,
A second insulating film is deposited on the first insulating film and the first conductive film, a part of the second insulating film is removed, and the second conductive film is formed on the second conductive film. A second insulating film deposition step for exposing a portion above the opening of
A bonding step of bonding an insulator material on the second insulating film;
A second conductive film treatment step of forming a second conductive film of a desired shape on the surface of the insulator material;
A process for producing a microtransformer comprising:   After the second conductive film processing step, an insulator material removing step of removing a part of the insulator material to expose a portion of the first conductive film above the second opening. The manufacturing method of the microtransformer of Claim 1 characterized by the above-mentioned.   The insulator material removing step is characterized in that the peripheral portion of the insulator material is removed so that the size of the insulator material is smaller than the chip size of each completed micro-transformer. 3. A method for producing a microtransformer according to 2.   A third insulating film is deposited on the insulator material and the second conductive film between the second conductive film processing step and the insulator material removing step, and the third insulating film is formed on the third insulating film. 3. The method of manufacturing a microtransformer according to claim 2, further comprising a third insulating film deposition step of forming an opening reaching the second conductive film.   The said 2nd electrically conductive film process process makes a conductor material adhere directly to the surface of the said insulator material so that a desired shape may be made. Of manufacturing a microtransformer.   2. The microtransformer manufacturing method according to claim 1, further comprising an insulator material processing step of processing the size of the insulator material into a size that does not cover the second opening before the bonding step. Method.

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