JP3570280B2 - Projecting electrode structure of semiconductor element and method of forming the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device, and more particularly to a protruding electrode structure of a semiconductor element used for mounting a chip on glass (COG) or the like and a method for forming the same.
[0002]
[Prior art]
Conventionally, there have been the following semiconductor device mounting methods. FIG. 2 is a view showing a mounting state of a conventional semiconductor element. The Au protruding electrode 23 formed on the electrode 22 of the semiconductor element 21 is pressure-bonded to a substrate electrode pad 25 on a glass substrate 24 or the like and fixed with an adhesive resin 26 or the like, whereby the electrode pad 25 on the semiconductor element 21 and the glass substrate 24 is fixed. It is what connects between. The Au protruding electrode 23 used in the example described above is generally formed by a stud bump method or an electrolytic plating method. In the stud bump method, a ball is formed and bonded while an Au wire is attached to an electrode pad of a semiconductor element. Next, a wire is cut at a position of several tens of μm from the ball to form a protrusion. FIG. 3 shows an example of the Au bump electrode forming process using the conventional electrolytic plating method. As shown in FIG. 3A, an Al electrode 32 is formed on the semiconductor element 31 and the periphery is covered with an insulating film 33. As shown in FIG. 2B, a Ti, W, Au thin film layer 34 is formed on the semiconductor element by a vapor phase method for ensuring adhesion of the protruding metal, preventing metal diffusion, and plating electrodes. Next, as shown in FIG. 3C, a photosensitive resist film 35 is formed, and the portions where the protruding electrodes are formed are exposed by photolithography. Further, as shown in FIG. 4D, a Au protruding electrode 36 is formed by electrolytic plating. Finally, as shown in FIG. 5E, the photosensitive resist is peeled off, and unnecessary portions of the Ti, W, and Au thin film layers are removed by etching to form Au protruding electrodes. However, the Au protruding electrode formed in this manner requires a photolithography process, a plating electrode formation, and an etching process in order to use electrolytic plating. Moreover, since the price of Au itself is expensive, it is disadvantageous in terms of cost reduction. In order to solve this problem, an electroless plating method that does not use electrolytic plating has been proposed. FIG. 4 shows an example of protruding electrode formation by the electroless plating method. As shown in FIG. 4A, an Al electrode 42 is formed on the semiconductor element 41 and the periphery is covered with an insulating film 43. As shown in FIG. 6B, zincate treatment is performed as a pretreatment for forming electroless plating, and the Al surface is replaced with Zn44. Next, as shown in FIG. 3C, the Ni protruding electrode 45 is formed by dipping in an electroless Ni plating solution. Further, as shown in FIG. 4D, an Au thin film 46 is formed on the Ni plating by dipping in an electroless Au plating solution.
[0003]
[Problems to be solved by the invention]
The method of FIG. 4 eliminates the need for plating electrodes, eliminates the need for a photolithography process, and enables cost reduction. However, the above prior art has the following drawbacks. Ordinary protruding electrodes have a plating thickness variation of 5 to 10%. When mounting on chip-on-glass (COG), etc., excessive pressure is applied to all protruding electrodes to make some or all of the protruding electrodes plastic. It must be deformed and connected. In this case, the Au protruding electrode is easily plastically deformed because the hardness of Au is low (50 to 70 HV). However, since the Ni protruding electrode has a very high hardness (500 to 700 HV), plastic deformation is not easy compared to Au. Therefore, there has been a problem that the semiconductor element or the film on the substrate is damaged during the mounting. Moreover, in order to replace the electroless Ni-plated thick film protrusion with the electroless Au-plated thick film protrusion, the plating speed of the electroless Au plating currently in practical use is very slow, so it is not suitable for forming a protruding electrode thick film. There was a problem.
[0004]
Accordingly, an object of the present invention is to solve the above-described problems and to prevent damage to the semiconductor element or the film of the substrate due to pressure when used for mounting chip-on-glass (COG) or the like at a low cost. It is an object of the present invention to provide a protruding electrode structure and a method of forming the same.
[0005]
[Means for Solving the Problems]
The present invention is for solving the above-described problems and comprises the following means.
[0006]
In a protruding electrode formed by metal plating on an electrode of a semiconductor element in which an insulating film is formed around the electrode, the protruding electrode comprises (a) the first metal plating layer on the electrode, (b A conductive ball in which an elastic ball is coated on the metal plating with a metal and a second layer in which the metal plating coexists; and (c) on a layer in which the conductive ball and the metal plating coexist. It is characterized by comprising a third layer of the metal plating, and (d) a metal plating having good adhesion to the electrode portion of the substrate to be connected further comprising a fourth layer on the metal plating. That is, the adhesion between the protruding electrode and the electrode of the semiconductor element is ensured by performing the metal plating of (a), and the layer of the conductive ball and the metal plating of (b) is formed so as to prevent the pressure bonding at the time of mounting. This makes it possible to absorb even stress. By performing the same metal plating as in (a) again in (c), the unevenness on the surface of the layer where the conductive balls and the metal plating coexist is flattened, and further, adhesion to the metal plating formed in (d) is ensured. The Here, when the metal plating having good adhesion to the electrode portion of the substrate to be mounted is used as the metal plating laminated in (a) and (c), the step (d) may be omitted. The thickness of the conductive ball plating layer (b) is desirably thicker than the height variation of the bump electrode due to the height variation of the bump electrode produced by the above method. In addition, the metal plating layers (a) and (c) may have a thickness that can provide adhesion to a contact metal, but is preferably 1 μm to 5 μm. Further, a layer in which the conductive ball and the plated metal coexist is formed in the plated metal of the protruding electrode so as to be thicker than at least the diameter of the conductive ball, and further thicker than the variation in thickness of the protruding electrode. It is characterized by that. In other words, even if there are variations in the thickness of the protruding electrodes, deformation due to stress when pressure-connected by an elastic conductive ball is possible, and good connection of the electrodes can be obtained even with a small overload. Damage to the electrode pad on the substrate side can be reduced. Further, by laminating a layer in which the conductive ball and the metal plating coexist so as to be thicker than the diameter of the conductive ball, it is possible to uniformly receive the stress when the pressure connection is made on the surface of the protruding electrode, and only a part of the stress is applied. Will not concentrate. Further, by forming the protrusion electrode thicker than the film thickness variation amount, it is possible to deform to absorb the film thickness variation. In addition, by using conductive balls, even if the balls are closely arranged, the balls are electrically connected, so there is no electrical deterioration. Further, the conductive ball is made of a resin coated with a metal such as Ni, Au, or Cu by an electroless plating method. That is, since the polymer resin particles are coated with a metal, the elastic deformation range is wide with respect to dimensional changes during thermal expansion and pressure bonding, making it suitable as a connecting member. Although the metal to coat | cover is not limited, it is desirable from the point of adhesiveness to use the same kind of metal as the plating metal of bump electrode formation. The ball is preferably spherical or pseudo-spherical. Further, the metal plating of the protruding electrode is made of Ni formed by an electroless plating method, and a thin film plating of Au formed by the electroless plating method is further laminated on the Ni plating. That is, by using the electroless plating method, an electrode for plating is unnecessary, a photolithography process is not required, and the cost can be reduced. In electroless plating, it is desirable to use conditions that prevent plating from being deposited on the balls when the conductive balls are dispersed. Further, by using electroless Ni plating as the metal material of the protruding electrode, the occurrence of pinholes is reduced and the corrosion resistance is improved. Furthermore, the controllability of the film thickness is good and a uniform surface can be obtained. In addition, it is easy to secure adhesion with the connecting part on the board side to be mounted by laminating the Au plating thin film on the Ni plating thick film, and the electroless Au plating time can be shortened by making the Au thin film. . Further, in the protruding electrode formed by metal plating on the electrode of the semiconductor element in which an insulating film is formed around the electrode, (a) a step of laminating the first metal plating on the electrode, (b) first (C) a step of dispersing the conductive ball on the metal plating of 1 and co-depositing the metal plating and the conductive ball to form a second layer in which the conductive ball and the metal plating coexist; A step of laminating a third layer of the metal plating on a layer in which the second conductive ball and the metal plating coexist; (d) a metal having good adhesion to the electrode portion of the substrate to be connected; It is characterized by forming a fourth layer on the metal plating. The metal plating is formed by an electroless plating method. That is, by forming all of the steps (a), (b), (c) and (d) using an electroless plating method, no electrode for plating is required, and no photolithography step is required, thereby reducing costs. It becomes possible.
[0007]
The present inventors have invented a method for forming a protruding electrode of a semiconductor element having the above structure, and a protruding electrode structure for a semiconductor element used for mounting chip-on-glass (COG) or the like that is low in cost and not damaged by pressure, and a method for forming the same Was successfully provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0009]
Example 1
FIG. 1 is a manufacturing process of a protruding electrode structure of a semiconductor element and a method for forming the same for explaining an embodiment of the present invention. First, as shown in FIG. 2A, Al is formed on the semiconductor element 10 by a vapor phase method, and an Al electrode 11 having a width of 100 μm, a length of 100 μm, and a thickness of 1 μm is formed by photolithography. The size of the electrode part can be freely changed according to the chip to be designed. Then, an insulating film 12 such as a SiO ₂ or SiON film is grown on the order of 2000 Å by a vapor phase method, and is etched using photolithography to form the insulating film 12 around the Al electrode. Next, as shown in FIG. 4B, zincate treatment is performed as a pretreatment for the electroless plating state, and the Al electrode surface 11 is replaced with Zn. Then, it is immersed in an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.), and the first Ni plating layer 13 is thickened. 5 μm is deposited. Next, as shown in FIG. 3C, an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L) in which conductive balls having elasticity (styrene particles: average particle diameter 1 μm, coating plating: Ni) are dispersed. , 2 g / L of propionic acid, 21 g / L of sodium hypophosphite, surfactant: 90 ° C.), the plating bath is stirred with a propeller or the like to uniformly eutect the conductive balls, The second Ni and the conductive ball eutectoid plating layer 15 taken in uniformly are formed to a thickness of 5 μm. Further, as shown in FIG. 4 (d), the sample was immersed in an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.) 3 Ni plating layer 16 is deposited to a thickness of 5 μm. Finally, as shown in FIG. 4E, an electroless Au plating solution (potassium dicyanoaurate 6 g / L, potassium cyanide 13 g / L, potassium hydroxide 11 g / L, potassium borohydride 22 g / L: temperature 75 ° C.) Immersion is performed to form an Au thin film 17 of 1 μm on the third Ni plating. The protruding electrode was formed by the above method. Further, the semiconductor chip (projection electrode 200 pieces / 1 semiconductor chip) on which the projection electrode is formed using this method has a projection electrode film thickness variation of 5 μm, and this semiconductor chip (100 chip) is mounted on a chip on glass (COG). As a result, damage to the substrate due to pressure bonding and poor connection were not recognized. With the above method, a bump electrode structure of a semiconductor element used for mounting chip-on-glass (COG) or the like that is low in cost and not damaged by pressurization and a method for forming the same have been successfully provided.
[0010]
(Example 2)
A zincate treatment is performed as a pretreatment for forming an electroless plating on an Al electrode of a semiconductor element having the same form as in Example 1, and the surface of the Al electrode is replaced with Zn. Then, it is immersed in an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.), and the first Ni plating layer has a thickness of 2 μm. Precipitate. Next, an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, hypochlorous acid) in which elastic conductive balls (styrene particles: average particle diameter 1 μm, coating plating: Ni) are dispersed. The second Ni and the conductive material are immersed in sodium phosphate (21 g / L, surfactant: 90 ° C.), the plating bath is stirred with a propeller to uniformly eutect the conductive particles, and the conductive balls are uniformly incorporated. A ball eutectoid plating layer is formed to a thickness of 10 μm. Further, it is immersed in an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.), and the third Ni plating layer 16 is thickened. 2 μm is deposited. Finally, it is immersed in an electroless Au plating solution (potassium dicyanoaurate 6 g / L, potassium cyanide 13 g / L, potassium hydroxide 11 g / L, potassium borohydride 22 g / L: temperature 75 ° C.) on the third Ni plating. An Au thin film is formed to 1 μm. The protruding electrode was formed by the above method. Further, the semiconductor chip (projection electrode 200 pieces / 1 semiconductor chip) on which the projection electrode is formed using this method has a projection electrode film thickness variation of 5 μm, and this semiconductor chip (100 chip) is mounted on a chip on glass (COG). As a result, damage to the substrate due to pressure bonding and poor connection were not recognized. With the above method, a bump electrode structure of a semiconductor element used for mounting chip-on-glass (COG) or the like that is low in cost and not damaged by pressurization and a method for forming the same have been successfully provided.
[0011]
(Comparative Example 1)
A zincate treatment is performed as a pretreatment for forming an electroless plating on an Al electrode of a semiconductor element having the same form as in Example 1, and then an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid). 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.) to deposit a Ni plating layer having a thickness of 15 μm. Immersion in electroless Au plating solution (potassium dicyanoaurate 6 g / L, potassium cyanide 13 g / L, potassium hydroxide 11 g / L, potassium borohydride 22 g / L: temperature 75 ° C.) to form 1 μm Au thin film on Ni plating To do. The protruding electrode was formed by the above method. Further, the semiconductor chip (projection electrode 200 pieces / 1 semiconductor chip) on which the projection electrode is formed using this method has a projection electrode film thickness variation of 5 μm, and this semiconductor chip (100 chip) is mounted on a chip on glass (COG). As a result, damage to the substrate due to pressure bonding and poor connection were recognized.
[0012]
(Comparative Example 2)
A zincate treatment is performed as a pretreatment for forming an electroless plating on an Al electrode of a semiconductor element having the same form as in Example 1, and the surface of the Al electrode is replaced with Zn. Thereafter, it is immersed in an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.), and the first Ni plating layer has a thickness of 8 μm. Precipitate. Next, an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, hypochlorous acid) in which elastic conductive balls (styrene particles: average particle diameter 1 μm, coating plating: Ni) are dispersed. The second Ni and the conductive material are immersed in sodium phosphate (21 g / L, surfactant: 90 ° C.), the plating bath is stirred with a propeller to uniformly eutect the conductive particles, and the conductive balls are uniformly incorporated. A ball eutectoid plating layer is formed to a thickness of 2 μm. Further, it is immersed in an electroless Ni plating solution (nickel sulfate 21 g / L, lactic acid 28 g / L, propionic acid 2 g / L, sodium hypophosphite 21 g / L: 90 ° C.), and the third Ni plating layer 16 is thickened. 5 μm is deposited. Finally, it is immersed in an electroless Au plating solution (potassium dicyanoaurate 6 g / L, potassium cyanide 13 g / L, potassium hydroxide 11 g / L, potassium borohydride 22 g / L: temperature 75 ° C.) on the third Ni plating. An Au thin film is formed to 1 μm. The protruding electrode was formed by the above method. Further, the semiconductor chip (projection electrode 200 pieces / 1 semiconductor chip) on which the projection electrode is formed using this method has a projection electrode film thickness variation of 5 μm, and this semiconductor chip (100 chip) is mounted on a chip on glass (COG). As a result, damage to the substrate due to pressure bonding and poor connection were recognized.
[0013]
【The invention's effect】
As described above, according to the protruding electrode structure and the forming method of the semiconductor element of the present invention, the protruding electrode is formed of the layer in which the elastic conductive ball and the metal plating coexist. However, if pressure connection is used during mounting, deformation due to stress is possible. In addition, by forming the protruding electrode using the electroless plating method, it is possible to eliminate the electrode formation and the photolithography process for electrolytic plating. As a result, it has become possible to provide a protruding electrode structure of a semiconductor element used for mounting chip-on-glass (COG) and the like, which are not damaged by pressure, and a method for forming the same.
[Brief description of the drawings]
FIG. 1 is a view for explaining a protruding electrode structure of a semiconductor element of the present invention and a method of forming the same.
FIG. 2 is a view for explaining a mounting state of a conventional semiconductor element.
FIG. 3 is a view for explaining a conventional bump electrode structure of a semiconductor element and a method of forming the same.
FIG. 4 is a view for explaining a conventional bump electrode structure of a semiconductor element and a method of forming the same.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Semiconductor element 11 Electrode 12 Insulation film 13 Metal plating layer 14 Conductive ball 15 Eutectoid plating layer of conductive ball and metal plating 16 Metal plating layer 17 Metal plating layer 21 ensuring adhesion with electrode of mounting side substrate 21 Semiconductor element 22 electrode 23 Au protruding electrode 24 glass substrate 25 electrode pad 31 semiconductor element 32 Al electrode 33 insulating film 34 Ti, W, Au thin film layer 35 photosensitive resist 36 Au protruding electrode 41 semiconductor element 42 Al electrode 43 insulating film 44 Zn thin film 45 Ni protruding electrode 46 Au thin film

Claims (6)

A protruding electrode formed by metal plating on an electrode of a semiconductor element having an insulating film formed around the electrode.
(A) comprising the first metal plating layer on the electrode;
(B) further comprising a conductive ball obtained by coating a metal on an elastic ball on the metal plating and a second layer in which the metal plating coexists.
(C) further comprising a third layer of the metal plating on the layer where the conductive balls and the metal plating coexist,
(D) Further, a metal plating having good adhesion to the electrode portion of the substrate to be connected is formed of a fourth layer on the metal plating.
A protruding electrode structure of a semiconductor element. A layer in which the conductive ball and the plated metal coexist is formed in the plated metal of the protruding electrode so as to be thicker than at least the diameter of the conductive ball, and further thicker than the variation in thickness of the protruding electrode. The protruding electrode structure of a semiconductor element according to claim 1. 3. The protruding electrode structure of a semiconductor element according to claim 1, wherein the conductive ball is made of a resin coated with a metal such as Ni, Au, or Cu by an electroless plating method. The metal plating of the protruding electrode is made of Ni formed by an electroless plating method, and a thin film plating of Au formed by the electroless plating method is further laminated on the Ni plating. 4. A protruding electrode structure for a semiconductor device according to claim 2 and claim 3. In a method for forming a protruding electrode formed by metal plating on an electrode of a semiconductor element in which an insulating film is formed around the electrode,
(A) laminating the first metal plating;
(B) Dispersing the conductive balls on the first metal plating and co-depositing the metal plating and the conductive balls to form a second layer in which the conductive balls and the metal plating coexist. ,
(C) laminating a third layer of the metal plating on a layer in which the second conductive ball and the metal plating coexist;
(D) A step of forming a metal having good adhesion to the electrode portion of the substrate to be connected as a fourth layer on the third metal plating.
A method for forming a bump electrode of a semiconductor element. 6. The protruding electrode forming method for a semiconductor device according to claim 5, wherein the metal plating is formed by an electroless plating method.

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