JP2011009376A - Method of forming bump, and method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a bump responding to a small pitch, and using metal nano-particle paste.SOLUTION: Under-bump metal layers 4 are formed on aluminum electrodes 2 electrically connected to an integrated circuit in a polyimide region 3 on a silicon wafer 1. Metal nano-particle paste 6 containing Sn nano-particles and a dispersant is printed by an inkjet printer in a state where flux 5 is applied to the whole surface of the wafer by a spin coat method. Thereafter, bumps 7 are formed by reflowing the wafer at the highest temperature of 260°C higher than 232°C being the melting point of Sn.

Description

  The present invention relates to a bump forming method for forming protrusions called bumps on a base electrode, and a semiconductor device manufacturing method for manufacturing a semiconductor chip, a semiconductor substrate, or the like on which bumps are formed by the bump forming method. .

  For electrical connection between substrates such as electronic devices, there is a method using protrusions called bumps formed on electrodes. In particular, in recent years, flip chip mounting using solder bumps formed on these electrodes for electrical connection between semiconductor substrates such as a semiconductor chip and a wiring board has become popular. A semiconductor chip used for such flip-chip mounting generally forms a base metal layer called an under bump metal layer in order to ensure the reliability of electrical connection at a bump forming position which is an electrode of a semiconductor wafer. After the solder layers are stacked, the solder is reflowed and melted, and then cooled and solidified to form bumps. By cutting the semiconductor wafer on which the bump is formed into individual chips, a semiconductor chip on which the bump is formed is obtained. In the case of a chip size package substrate in which rewiring and electrode formation such as Cu posts are performed at the wafer level and the surface is protected by applying resin or the like, the under bump metal layer is formed in the same process after bump formation. do not have to.

  At present, the plating method, which is the most common bump formation method, forms an under bump metal layer by sputtering and electrolytic plating, and then laminates the solder layer by electrolytic plating, and then melts and solidifies the solder layer. With bumps. In addition, as other main methods, an under bump metal layer is formed by sputtering, and a predetermined amount of solder paste made of solder powder and flux is mounted thereon by stencil printing, etc., or an under bump metal layer There is a ball mounting method in which a flux is applied on top and a single solder ball is mounted thereon, and both of them are made into bumps by melting and solidifying the mounted solder.

  By the way, with the miniaturization and high functionality of electronic devices, high-density mounting is also required in semiconductor mounting. For this reason, flip-chip mounting, which is advantageous for high-density mounting, has been rapidly adopted. In recent years, however, a narrow pitch such as an electrode pitch of 100 μm or less has been demanded. At such a narrow pitch, the paste printing method and the ball mounting method cannot be used, so the current situation is that only the plating method can be used.

  However, the plating method has a problem that, after plating the solder, when the unnecessary under bump metal layer is removed by etching, the under bump metal layer hidden under the solder is excessively etched. This problem becomes serious because an extremely narrow pitch, that is, when the area of the under bump metal layer is small, an electrical / mechanical connection failure occurs. In the paste printing method and the ball mounting method, since the under bump metal layer is formed in a separate process, the state can be confirmed after the under bump metal layer is formed.

  On the other hand, Patent Document 1 and Patent Document 2 attempt to form bumps by laminating metal nanoparticle paste containing metal nanoparticles and a dispersant by an ink jet printing method, a screen printing method, or the like, and use them for flip chip mounting. It is described in. In these methods, a predetermined amount of the metal nanoparticle paste is laminated on the electrode of the semiconductor chip and heated to remove the dispersant, and at the same time, the metal nanoparticle is sintered to form a bump, or the wiring substrate and the flip chip joint In this case, the metal nanoparticles are sintered by heating.

JP 2005-259848 A JP 2007-208082 A

  In the inkjet printing method using the metal nanoparticle paste described above, for example, in the case of a narrow pitch of 100 μm or less, it is very difficult to realize the accuracy of ± 25 μm or less required for a bump diameter of 50 μm and a space between bumps of 50 μm. . This is because the position accuracy of inkjet printing is generally about ± 5 μm, and the viscosity of the metal nanoparticle paste that can be achieved by the current inkjet printing method is low, and the metal nanoparticle paste that has landed on the electrode has a paste diameter before landing. This is because the height of the bump cannot be ensured because it expands to 5 times or more. In addition, the paste may protrude from the electrode and come into contact with the paste on the adjacent electrode. In the method of printing multiple times at the same position to ensure the bump height, the print position accuracy is not sufficient as described above, so the bump diameter further expands as the number of times of printing increases, and narrows. Pitch bump formation is still difficult.

  In addition, when using the conventional metal nanoparticle paste, the metal nanoparticles are not melted, but are heated in the stacked shape to sinter and solidify the metal nanoparticles. Bump height accuracy and position accuracy are strictly required.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a bump forming method using a metal nanoparticle paste that can cope with a narrow pitch. It is another object of the present invention to provide a method for manufacturing a semiconductor device which can easily perform flip chip connection with excellent reliability by a bump forming method using a metal nanoparticle paste.

In the bump forming method according to one aspect of the present invention, a flux is applied on a metal electrode of a base material, and then a metal nanoparticle paste containing metal nanoparticles and a dispersant is laminated on the flux, and the metal nanoparticles Bumps are formed by heating the paste.
According to another aspect of the present invention, a bump forming method includes forming an under bump metal layer on a metal electrode of a substrate, applying a flux on the under bump metal layer, and then including metal nanoparticles and a dispersant. The metal nanoparticle paste is laminated on the flux, and the metal nanoparticle paste is heated to form bumps.
In the bump forming method, the size of the flux application surface may be larger than the size of the bump formation surface and less than or equal to the entire surface of the base material.
In the bump forming method, the heating of the metal nanoparticle paste melts the metal nanoparticles.
A method for manufacturing a semiconductor device of the present invention is characterized in that bumps are formed on a base material of a semiconductor device by the bump forming method of the present invention.

According to the present invention, by applying a flux in advance on the metal electrode or the under bump metal layer, it is possible to prevent the droplet of the metal nanoparticle paste from spreading on the base material upon landing. Even in the case of a narrow pitch, connection between adjacent bumps can be prevented.
In addition, the under bump metal layer can be formed in a separate process, and a fine under bump metal layer capable of dealing with a narrow pitch can be formed accurately and appropriately.
Furthermore, by printing an appropriate amount of the metal nanoparticle paste using an ink jet printer, a minute amount of nanometal particles capable of handling a narrow pitch can be accurately stacked.
Furthermore, by melting the metal nanoparticles laminated by printing, it is possible to obtain a bump having a uniform shape by surface tension regardless of the shape of the printed paste. Also, the bump is formed at the correct position even if there is a slight misalignment during printing due to the self-alignment effect caused by the reaction between the metal nanoparticles and the under bump metal layer.
At this time, since there is a pre-applied flux, it is not necessary to mix the flux component in the metal nanoparticle paste, and the metal nanoparticle paste can be produced with only the optimum component for the ink jet printing method.
When a semiconductor device is manufactured by applying the present invention, since a high-precision bump is formed, it is possible to provide a semiconductor device that can easily perform flip-chip connection with excellent reliability.

It is a schematic sectional drawing for demonstrating the bump formation method which concerns on Example 1 of this invention, and the manufacturing method of a semiconductor device. It is a schematic sectional drawing for demonstrating the bump formation method which concerns on Example 2 of this invention, and the manufacturing method of a semiconductor device. It is a schematic sectional drawing for demonstrating the bump formation method which concerns on Example 3 of this invention, and the manufacturing method of a semiconductor device. It is a figure which shows the pattern outline of the electrode in the bump formation method which concerns on Example 4 of this invention, a flux, and a bump formation surface.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
In the bump forming method to which the present invention is applied, a flux is applied on the metal electrode of the substrate. By applying the flux, spreading of the metal nanoparticle paste at the time of landing can be suppressed. In the case of a resin such as a metal surface or polyimide used for a normal semiconductor device, the spread diameter at the time of landing is 100 μm or more for a 5 pL (picoliter) droplet, for example, without applying a flux. When the flux is applied, the sprayed paste can be suppressed to about twice the diameter when it is made spherical. That is, a 5 pL droplet has a spherical shape with a diameter of about 21 μm, but the landing diameter on the applied flux is suppressed to about 40 μm.

  When the metal nanoparticle paste is printed without flux, the spread of the paste upon landing is due to the low viscosity of the metal nanoparticle paste and the landing surface (base material, metal electrode, under bump metal layer, insulating layer, etc.) This is also because the paste has high wettability. The spread at the time of landing can be suppressed if the surface of the metal nanoparticle paste and the surface having low wettability are increased. The flux has the above-described effects, and even when the metal nanoparticle paste has a low viscosity, the spread at the time of landing can be suppressed. That is, the wettability to the metal nanoparticle paste is lower on the applied flux surface than on the surfaces of the substrate, metal electrode, undermetal layer, and insulating layer. Furthermore, the flux also has an effect of contributing to the reaction of the nano metal particles with the under bump metal layer during reflow.

  As the flux used for the above purpose, an appropriate component may be selected for the metal nanoparticle paste to be used. However, in the case of a bump composition used for ordinary solder, a rosin flux or a water-soluble flux may be used.

  The rosin-based flux is basically obtained by dissolving rosin in an organic solvent and adding an activator. As the organic solvent, rosins such as alcohols (for example, isopropyl alcohol), acetone, and esters can be dissolved. Examples of the activator include amine / hydrohalide, carboxylic acid, and amine. A matting agent, a corrosion inhibitor, a thixotropic agent, a fragrance, a colorant, and the like are added as necessary.

  The water-soluble flux is basically obtained by dissolving water-soluble organic substances such as esters, glycols, diol compounds, and alkylbenzimidazole compounds in water and adding an activator. Examples of the activator include amine hydrohalides, carboxylic acids, and amines. If necessary, water-soluble alcohols such as isopropyl alcohol, ethylene glycol, propylene glycol, ethylene glycol monobutyl ether, antioxidants, surfactants, anti-glare agents, matting agents, corrosion inhibitors, preservatives, A thixotropic agent, a fragrance, a colorant, and the like are added.

  The flux coating method includes a stencil printing method, a spin coating method, a spraying method, and the like. In the case of a narrow pitch electrode, a spin coating method that can be applied thinly and uniformly is preferable. Moreover, you may apply | coat a flux with the inkjet printing method. In the case of applying by the ink jet printing method, it is preferable to prepare another ink jet nozzle for flux separately from the metal nano particle paste ink jet nozzle.

  The size of the flux application surface may be equal to or larger than the application size of the metal nanoparticle paste. Furthermore, the size of the flux application surface is preferably larger than the size of the bump formation surface. You may apply | coat a flux to the whole surface of a base material surface. When the size of the flux application surface is equal to or less than the size of the bump formation surface, the metal nanoparticle paste to be laminated may protrude from the applied flux and spread.

  A suitable thickness of the flux is selected depending on the pitch and the electrode shape, but is at least one third of the electrode pitch, for example, 20 μm or less, more preferably 10 μm or less at a 60 μm pitch. This is because when the flux is thick, the metal in the metal nanoparticle paste flows together with the flux when melted, and a problem of bonding with adjacent bumps is likely to occur.

  The metal nanoparticle paste according to the present invention includes metal nanoparticles and a dispersant. The metal nanoparticles may be conductive metal fine particles having an average particle diameter of nanometers. In particular, fine particles (average particle diameter of 5 nm or more and less than 60 nm, more preferably 5 to less than 5 nm, which is used for ordinary solders such as Sn, Cu, Ag, In, and Ni so that the metal nanoparticles can be melted by reflow. 10 nm) is preferred. In addition, the metal nanoparticles are used either by sintering at 400 ° C. or lower, which is a temperature that does not adversely affect the semiconductor device, or by adjusting a single or a plurality of metal components so as to have a melting point of 400 ° C. or lower. When melting metal nanoparticles, it is not necessary for the metal nanoparticles to melt all the metal components, as long as the melted components react with the under bump metal layer to form a bump with a normal position and shape. .

  The metal nanoparticle paste is prepared by dispersing the above metal nanoparticles in a solvent selected from water, alcohols, organic solvents and the like with a dispersant. Although the dispersant improves the dispersibility by forming a molecular layer covering the surface of the metal nanoparticle, it does not interfere with the contact between the metal nanoparticles and the surface in the heating step. Preferably not. That is, for example, when heated to 200 ° C. or higher, those having a boiling range in which they can be easily detached from the surface of the metal nanoparticles and finally evaporated and removed are preferable. As the dispersant, for example, alkylamine, alkanethiol, alkanediol, and the like can be used.

  The content of the metal nanoparticles contained in the metal nanoparticle paste has physical properties that enable ink jet printing, and it is preferable to increase the content of the metal nanoparticles in order to reduce the number of laminations, from 40 mass% to 70 mass%. Is a more preferable range.

  The substrate according to the present invention is formed by forming metal electrodes and being electrically connected by bumps. For example, the substrate is provided with wiring, mounted with an electronic device or an optical electronic device. Examples of the substrate include a semiconductor substrate such as a semiconductor chip and its wiring substrate.

  The metal electrode according to the present invention is not particularly limited as long as it is a metal having conductivity. Usually, an Al or Cu electrode is used for a semiconductor substrate. Furthermore, an under bump metal layer may be formed on the metal electrode. Usually, the under bump metal layer is formed by sputtering, electrolytic plating, electroless plating, or the like.

  In the present invention, the formation method of the under bump metal layer is not particularly limited. However, the target narrow pitch electrode is preferably formed by sputtering. In particular, when the main component of the bump is Sn, the reliability may deteriorate due to the reaction with the under bump metal layer. Therefore, three thin films of Ti layer, Ni to Ni alloy layer, and Cu layer from the electrode side of the semiconductor device. A structure is preferred. Here, Ti ensures adhesion and barrier properties, and Ni or Ni alloys react slowly with Sn to ensure stable bonding. Further, Cu prevents oxidation of Ni or Ni alloy, and also reacts quickly with the metal in the metal nanoparticle paste during reflow to cause wetting. Although long-term reliability is inferior, a thick Cu layer may be formed instead of Ni or Ni alloy.

  In order to laminate the metal nanoparticle paste on the flux, there are an ink jet printing method, a screen printing method, and the like. In particular, the ink jet printing method is preferable as the electrode pitch becomes narrower. The ink jet method in the ink jet printing method is not particularly limited as long as ink can be ejected (jetted), and examples thereof include a bubble jet (registered trademark) method, a thermal ink jet method, and a piezo element method. Hereinafter, the inkjet printing method will be described as an example of a piezo element method.

  The ink jet printer includes an ink jet head having a mechanism for ejecting a small amount of paste from a nozzle by a piezo element, a mechanism for moving the head, and a control unit for controlling ejection. In order to efficiently stack a predetermined amount of the metal nanoparticle paste on the plurality of electrodes on the wafer, a method of spraying the paste appropriately from each nozzle while moving a head having a plurality of nozzles on the wafer is taken. In addition, when a paste containing the amount of metal nanoparticles necessary for bump formation is sprayed at a narrow pitch, contact occurs between adjacent electrodes even if there is almost no spread at the time of landing. More preferably, the necessary nano metal particles are laminated by spraying a small amount of paste a plurality of times until a target bump volume is obtained.

  The laminated metal nanoparticles are solidified by heating to form bumps. Solidification by heating is possible by sintering the metal nanoparticles or by melting some or all of the metal nanoparticles. In particular, it is preferable to melt at a melting point or higher and to solidify by cooling, and it is possible to obtain a bump having a uniform shape by surface tension regardless of the shape of the printed paste. The method of heating the metal nanoparticles may be an apparatus used for normal solder reflow, and the temperature profile may be suitable for the flux to be used.

  Hereinafter, embodiments of the invention will be described with reference to examples.

First, Embodiment 1 will be described with reference to FIGS.
FIG. 1A shows a partial cross section of an 8-inch silicon wafer 1 on which a plurality of semiconductor devices are formed, and is electrically connected to an internal integrated circuit having a pitch of 80 μm and an opening diameter of 30 μm of polyimide resin 3. An under bump metal layer 4 having a diameter of 40 μm is formed on the aluminum electrode 2. The under bump metal layer 4 has a thin film three-layer structure formed by a sputtering method. From the aluminum electrode 2 side, a Ti layer having a thickness of 0.3 μm, a Ni-7 at% V alloy having a thickness of 0.4 μm, and a Cu layer having a thickness of 0.3 μm. It is.

  FIG. 1B shows a state after the flux 5 is applied to the entire surface of the wafer by spin coating. A water-soluble flux containing glycol, organic carboxylic acid, isopropyl alcohol, and water is applied to an average thickness of 5 μm.

  FIG. 1 (c) shows an example of a metal nanoparticle paste 6 containing Sn nanoparticles (average particle size 5 nm) and a dispersant (Sn nanoparticle content: 50 mass%) by an inkjet printer having a piezoelectric element type inkjet head. Indicates the printed state. The appropriate amount of liquid at one time was 5 pL, and a total of 11 injections were performed on one electrode. The Sn content in the used Sn nanoparticle paste was 60% by mass, and about 0.25 μg of Sn was laminated on the electrode by 11 injections. Even if spraying once or spraying 11 times, the paste spreads little and does not contact the adjacent paste.

  FIG. 1D shows a state after the wafer is reflowed at a maximum temperature of 260 ° C. Here, since the melting point of Sn is 232 ° C., the Sn nanoparticles are melted by reflow. As a result, bumps 7 having a height of about 29 μm and an outer diameter of about 44 μm were formed.

  In the case of this embodiment, there are 46,656 electrodes on one chip and 74 chips on the entire 8-inch wafer, so the total number of electrodes is 3,452,544, but all the formed electrodes are normal. Bumps were formed.

  Thus, a semiconductor device (semiconductor chip) in which bumps 7 were formed on the aluminum electrode 2 applied to the silicon wafer 1 on which the semiconductor device was formed was obtained. When the semiconductor chip on which the bumps 7 were formed was flip-chip bonded to the wiring board, normal bonding was easily achieved.

  On the other hand, when a Sn nanoparticle paste was printed under the same conditions using a wafer to which a flux was not applied for comparison, the nanometal paste overlapped after printing, and the chip on which the bumps were normally formed after reflowing There was nothing. Therefore, a good semiconductor device could not be manufactured. That is, even when flip chip bonding was performed, bonding failure occurred.

Next, Example 2 will be described with reference to FIGS.
FIG. 2A shows a partial cross section of an 8-inch silicon wafer 1 on which a plurality of semiconductor devices are formed. An under bump having a diameter of 20 μm is formed on an aluminum electrode 2 having a pitch of 40 μm and an opening diameter of 15 μm of a silicon oxide film 8. A metal layer 4 is formed. The under bump metal layer 4 has a thin film three-layer structure formed by a sputtering method. From the aluminum electrode 2 side, 0.15 μm thick Ti, 0.3 μm thick Ni-7 at% Ti alloy, and 0.1 μm thick Cu alloy are sequentially formed. It is.

  FIG. 2B shows a state after the flux 5 is applied to the entire surface of the wafer by spin coating. A water-soluble flux containing glycol, organic carboxylic acid, isopropyl alcohol, and water is applied to an average thickness of 3 μm.

  FIG. 2C shows a state in which an In nanoparticle paste (In nanoparticle content: 60 mass%) containing In nanoparticles (average particle size 10 nm) and a dispersant is printed by the same ink jet printer as in Example 1. Indicates. The appropriate amount of one liquid was 1 pL, and a total of 7 injections were performed on one electrode. The In content in the used In nanoparticle paste was 60% by mass, and about 0.03 μg of In was laminated on the electrode by seven injections. Even if spraying once or spraying 7 times, the paste spreads little and does not come into contact with the adjacent paste.

  FIG. 2 (d) shows a state after the wafer is reflowed at a maximum temperature of 190 ° C. Here, since the melting point of In is 156.6 ° C., the In nanoparticles are melted by reflow. As a result, bumps 7 having a height of about 15 μm and an outer diameter of about 22 μm were formed. As a result of inspecting all the bumps on the wafer, all the bumps were formed normally.

  Thus, a semiconductor device (semiconductor chip) in which bumps 7 were formed on the aluminum electrode 2 applied to the silicon wafer 1 on which the semiconductor device was formed was obtained. When the semiconductor chip on which the bumps 7 were formed was flip-chip bonded to the wiring board, normal bonding was easily achieved.

  Regarding the reflow temperature, the same wafer was reflowed at a maximum temperature of 140 ° C. In this case, although the temperature was not higher than the melting point of In, the In nanoparticles were sintered and the bump shape accuracy was somewhat inferior, but the bump 7 could be formed.

  Thus, a semiconductor device (semiconductor chip) in which bumps 7 were formed on the aluminum electrode 2 applied to the silicon wafer 1 on which the semiconductor device was formed was obtained. When the semiconductor chip on which the bumps 7 were formed was flip-chip bonded to the wiring board, bonding was possible with a high yield.

Next, Example 3 will be described with reference to FIGS.
FIG. 3A is a partial cross-sectional view of an 8-inch silicon wafer 1 on which a plurality of semiconductor devices are formed to form a wafer-level chip size package by forming electrodes using a Cu rewiring layer 9 and a Cu post 10. Show. The Cu posts have a pitch of 100 μm and a diameter of 50 μm, and the surfaces other than the Cu posts 10 are filled with an epoxy-based sealing resin 11.

  In such a chip size package, since the electrode formed on the semiconductor device after rewiring has a function as an under bump metal layer, it is necessary to form an under bump metal layer like a semiconductor device with an aluminum electrode. Absent.

  FIG. 3B shows a state after the flux 6 is applied to the entire surface of the wafer by spin coating. A water-soluble flux containing glycol, organic carboxylic acid, isopropyl alcohol, and water is applied to an average thickness of 10 μm.

  FIG. 3 (c) shows a metal nanoparticle paste containing Sn, Ag, Cu mixed nanoparticles (average particle size 60 nm) and a dispersant (metal nanoparticle content: 50 mass) using the same ink jet printer as in Example 1. %) Is printed. The appropriate amount of liquid at one time was 10 pL, and a total of 11 injections were performed on one electrode. The metal content in the used nano metal paste was 60% by mass, and a metal of about 0.48 μm was laminated on the electrode by 11 injections. Even if spraying once or spraying 11 times, the paste spreads little and does not contact the adjacent paste.

  FIG. 3D shows a state after the wafer is reflowed at a maximum temperature of 260 ° C. In reflow, some of the metal nanoparticles are melted. As a result, bumps 7 having a height of about 37 μm and an outer diameter of about 55 μm were formed. As a result of inspecting all the bumps on the wafer, all the bumps were formed normally.

  In this way, a semiconductor device (semiconductor chip) in which bumps 7 were formed on the electrodes applied to the silicon wafer 1 on which the semiconductor device was formed was obtained. When the semiconductor chip on which the bumps 7 were formed was flip-chip bonded to the wiring board, normal bonding was easily achieved.

  After the aluminum electrode model 12 shown in FIG. 4 was formed on a silicon wafer (not shown), a rosin-based flux containing rosin, isopropyl alcohol, and amine was printed at an average thickness of 5 μm, and then Example 1 A bump (not shown) was formed thereon using the same ink jet printer and Sn nanoparticle paste (not shown). FIG. 4A shows an example in which the flux 13 a is printed with the same size as the bump forming surface 14. FIG. 4B shows an example in which the flux 13 b is printed larger than the size of the bump forming surface 14. FIG. 4C is an example in which the flux 13 c is printed so as to be larger than the size of the bump forming surface 14 and straddle the plurality of metal electrodes 12. The flux was printed on each predetermined shape using a mask by the stencil method.

  Regarding the printing of the Sn nanoparticle paste, in the same manner as in Example 1, the appropriate amount of one liquid was 5 pL, and a total of 11 injections were performed on one electrode. Sn content in the used Sn nanoparticle paste is 60 mass%, and about 0.25 μg of Sn is laminated on the electrode by 11 injections. In any of the cases shown in FIGS. 4A to 4C, even if one injection or 11 injections are performed, the paste spreads little and does not come into contact with the adjacent paste. However, with respect to FIG. 4 (a), when the Sn nanoparticle paste protrudes from the bump forming surface, the paste spreads out, so the printing speed of the Sn nanoparticle paste is slowed so that the bump forming surface does not protrude. The paste is printed.

  As a result of inspecting the wafer reflowed at the maximum temperature of 260 ° C. after printing the Sn nanoparticle paste, normal bumps were formed. Further, when simulated flip-chip connection was performed using each of the bumps, normal bonding was easily achieved.

  The present invention is applied to a semiconductor device of a type in which protruding electrodes (bumps) formed on a semiconductor chip are electrically connected to a wiring pattern of a wiring board, and supports various uses such as a memory, a logic, a discrete semiconductor, or a combination circuit thereof. Can be made.

DESCRIPTION OF SYMBOLS 1 Silicon wafer 2 Aluminum electrode 3 Polyimide resin 4 Under bump metal layer 5 Flux 6 Nano metal paste 7 Bump 8 Silicon oxide film 9 Cu rewiring layer 10 Cu post 11 Epoxy sealing resin 12 Aluminum electrode model 13a Flux 13b Flux 13c Flux 14 Bump formation surface

Claims (5)

  After applying the flux on the metal electrode of the base material, a metal nanoparticle paste containing metal nanoparticles and a dispersant is laminated on the flux, and the metal nanoparticle paste is heated to form bumps. A bump forming method.   After forming an under bump metal layer on the metal electrode of the base material and applying a flux on the under bump metal layer, a metal nanoparticle paste containing metal nanoparticles and a dispersant is laminated on the flux, and A bump forming method comprising forming a bump by heating a metal nanoparticle paste.   The bump forming method according to claim 1, wherein a size of the flux application surface is larger than a size of the bump forming surface and equal to or less than the entire surface of the base material.   The bump forming method according to any one of claims 1 to 3, wherein the heating of the metal nanoparticle paste melts the metal nanoparticles.   A bump forming method according to any one of claims 1 to 4, wherein a bump is formed on a base material of the semiconductor device.

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