JP4047065B2 - Method for forming pad electrode part for semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a pad electrode portion for a semiconductor device and a manufacturing method thereof , and more particularly, to a pad electrode portion for a semiconductor device used for FC (flip chip) or BGA (ball grid array) having hemispherical solder bumps . The present invention relates to a structure and a manufacturing method thereof .
[0002]
[Prior art]
2. Description of the Related Art In recent years, with the miniaturization and thinning of electronic devices, high-density mounting technology for electronic components is rapidly progressing. As semiconductor devices that realize this high-density mounting, those having hemispherical solder bumps are widely used. FIG. 6 is a cross-sectional view showing such a conventional semiconductor device.
[0003]
In FIG. 6, the semiconductor device 80 includes a pad electrode 84 formed on the semiconductor chip 82 and a solder bump 88 formed on the pad electrode 84. The pad electrode 84 includes an aluminum electrode 840 formed on the semiconductor chip 82, a nickel layer 841 formed on the aluminum electrode 840, and a gold layer 842 formed on the nickel layer 841. The nickel layer 841 and the gold layer 842 constitute an UBM (under barrier metal) layer. The solder bump 88 is made of a tin alloy. Portions other than the pad electrode 84 on the semiconductor chip 82 are covered with a protective film 90.
[0004]
7 and 8, shows the method of forming solder bumps 88 formed on pad electrodes 84 of the semiconductor chip 82.
[0005]
7 and 8, first, an aluminum electrode 840 is formed on the semiconductor chip 82, and a protective film 90 is formed on the portion other than the aluminum electrode 840 with a polyimide resin (FIG. 7 [1]). These are formed using, for example, a photolithography technique and an etching technique. Subsequently, after zincate treatment is performed on the surface of the aluminum electrode 840, a nickel layer 841 and a gold layer 842 are formed on the aluminum electrode 840 by using an electroless plating method (FIG. 7 [2]). The reason for providing the UBM layer (nickel layer 841 and gold layer 842) is to impart solder wettability to the aluminum electrode 840. Finally, the solder bump 88 is formed on the pad electrode 84 by bringing the pad electrode 84 shown in FIG. 7 [2] into contact with the molten solder 92 (FIGS. 8 and 7 [3]). The semiconductor device 80 obtained in this way is electrically and mechanically connected to other semiconductor chips and wiring boards via solder bumps 88.
[0006]
[Problems to be solved by the invention]
With the further miniaturization of the semiconductor device 80 in recent years, the area of the pad electrode 84 is also becoming smaller. However, the smaller the area of the pad electrode 84, the lower the solder wettability and the case where the solder bump 88 cannot be formed has occurred.
[0007]
OBJECT OF THE INVENTION
An object of the present invention, even on a small pad electrodes in area, is to provide a structure and a manufacturing method thereof for a semiconductor device pad electrode portion that can reliably form the solder bumps.
[0008]
[Means for Solving the Problems]
The present inventor has obtained the following knowledge by repeating experiments and considerations on the phenomenon that the solder wettability decreases as the area of the pad electrode decreases.
[0009]
The smaller the area of the pad electrode, the smaller the surface area of the molten solder that contacts the pad electrode. As a result, the cohesive force of the molten solder that comes into contact with the pad electrode (that is, the force that tends to become a sphere by the surface tension) increases, so the adhesion force of the molten solder to the pad electrode decreases. This can be easily understood from the fact that the smaller the polka dots on the lotus and taro leaves, the closer to the true sphere. This is considered to be the reason why the solder wettability decreases as the area of the pad electrode is smaller.
[0010]
The present invention has been made based on this finding. That is, in order to achieve the above object, the structure of the pad electrode portion for a semiconductor device according to the present invention is composed of a pad electrode formed on a semiconductor chip and a hemispherical solder bump formed on the pad electrode. A pad electrode portion for a semiconductor device, wherein when the pad electrode is cut along a plane perpendicular to the surface of the pad electrode, the cross-sectional shape becomes wider toward the semiconductor chip. It is formed in a trapezoidal shape, that have adopted a configuration that.
[0011]
In this case, since the pad electrode itself has a convex body, it overcomes the cohesive force of the molten solder from the force on the tip of their concentrates, write no pad electrode enters into the molten solder. Therefore, the interface between the molten solder and the Pas head electrode, the alloy layer is formed. Further, since the solder is piled in the side wall of the pad electrode, solder amount of the solder bumps also increases.
[0012]
In order to achieve the above object, the structure of the pad electrode portion for a semiconductor device according to the present invention comprises a pad electrode formed on a semiconductor chip and a hemispherical solder bump formed on the pad electrode. a semiconductor device pad electrode portion formed by the pad electrode, wherein the Arumini c electrodeless held in the semiconductor chip, and a nickel layer the Arumini window stacked on electrodeless, the nickel layer constituted by a gold layer laminated on, it characterized in that the cross section of the nickel layer was trapezoidal.
[0013]
Here, the nickel layer described above, the Arumini c electrodeless but it may also be one that is laminated by electroless plating technique.
[0014]
In order to achieve the above object, a method of forming a pad electrode portion for a semiconductor device according to the present invention forms an aluminum electrode on a semiconductor chip and forms a protective film around the aluminum electrode around the aluminum electrode. A first step; a second step of forming a photoresist film on the protective film; and a second step of forming a nickel layer on the aluminum electrode surrounded by the protective film and the photoresist film by electroless plating. And a fourth step of removing the photoresist film after the electroless plating and forming a gold layer on the nickel layer exposed by the removal of the photoresist film, and the nickel layer as the gold layer. And a fifth step of forming a solder bump on the nickel layer via the gold layer.
[0015]
Furthermore, method of forming the semiconductor device for pad electrode portion, in the second step described above, the aluminum electrode on by directing light from an oblique direction against the photoresist film located in a space on the aluminum electrode It adopts a configuration referred to in the space being formed in the shape of a truncated cone, and (claim 1)
[0018]
(Delete)
[0019]
(Delete)
[0020]
(Delete)
[0021]
The present inventor made pad electrodes with various angles between the isosceles trapezoidal leg and the base, and investigated the relationship between the angle and the shape of the solder bump (at this time, the pad was printed by screen printing or solder balls). since the formation of the solder bump on the electrode, the solder of the solder bumps was constant). As a result, when the angle between the leg of the isosceles trapezoid and the base is changed, for example, from 0 ° to 90 °, the height of the solder bump gradually increases and reaches a maximum value at a certain angle and starts to decrease. Became. Therefore, it was found that by using this phenomenon, solder bumps having different heights can be obtained even with the same amount of solder.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
First, the peripheral technology devised by the inventor at the same time as the structure of the pad electrode part for a semiconductor device according to the present invention will be described, and thereafter, the embodiment of the present invention will be specifically described.
[0023]
FIG. 1 is a cross-sectional view showing an example of peripheral technology in the structure of a pad electrode portion for a semiconductor device according to the present invention.
In FIG. 1, reference numeral 10 indicates a semiconductor device, and reference numeral 12 indicates a semiconductor device chip. By this semiconductor chip solder bumps 20 formed on the remaining portion 162 on the upper and the convex member 18 projecting from the part 161 on the pad electrode 14 the convex member 18 and the pad electrode 14 of the 12, pad electrodes The part is composed . The pad electrode 14 includes an aluminum electrode 140, a nickel layer 141, and a gold layer 142. The nickel layer 141 and the gold layer 142 are UBM layers. The convex body 18 is made of copper, and the solder bump 20 is made of eutectic solder. Portions other than the pad electrode 14 on the semiconductor chip 12 are covered with a protective film 22.
[0024]
The pad electrode 14 has a disk shape with a diameter of about 50 μm. The nickel layer 141 and the gold layer 142 (UBM layer) are provided to improve the solder wettability of the pad electrode 14. The cross-sectional shape of the convex body 18 is preferably a trapezoidal shape or a triangular shape in order to concentrate the force at the tip.
[0025]
2 and 3 are cross-sectional views illustrating a method for manufacturing the semiconductor device 10. Hereinafter, description will be given based on this drawing.
[0026]
First, an aluminum electrode 140 is formed of aluminum, and a protective film 22 is formed of a polyimide resin or an oxide film (FIG. 2 [1]). These are formed using, for example, a photolithography technique and an etching technique. Subsequently, a nickel layer 141 and a gold layer 142 are formed on the aluminum electrode 140 (FIG. 2 [2]). At this time, after the zincate treatment is performed on the surface of the aluminum electrode 140, the nickel layer 141 and the gold layer 142 are formed by using an electroless plating method.
[0027]
Subsequently, a convex body 18 is projected from a part on the pad electrode 14 (FIG. 2 [3]). For example, copper is formed on the pad electrode 14 and the protective film 22 by sputtering or plating, a photoresist pattern is formed thereon, copper is etched using this photoresist pattern, and finally the photoresist pattern is formed. By removing the, the convex body 18 can be formed. When this copper is etched, if isotropic etching such as wet etching is used, a sharp convex body 18 having a trapezoidal or triangular cross section can be easily obtained.
[0028]
Finally, the semiconductor chip 12 in the state shown in FIG. 2 [3] is immersed in the molten solder 24, thereby forming the solder bumps 20 on the pad electrode 14 (FIGS. 3 and 2 [4]). The semiconductor device 10 obtained in this way is electrically and mechanically connected to other semiconductor chips and wiring boards via the solder bumps 20.
[0029]
If the convex body 18 is provided on a part of the pad electrode 14, the force concentrates on the tip of the convex body 18, so that the cohesive force of the molten solder 24 is overcome and the convex body 18 enters the molten solder 24. . The pad electrode 14 also contacts the molten solder 24 so as to be dragged by this. Therefore, an alloy layer (not shown) is formed at the interface between the convex body 18 and the molten solder 24 and at the interface between the pad electrode 14 and the molten solder 24. Further, since the convex body 18 has an action of breaking through an oxide film (not shown) on the surface of the molten solder 24, this also improves the solder wettability. Further, since the solder is also deposited on the side wall of the convex body 18, the solder amount of the solder bump 20 is also increased.
[0030]
The convex body 18 may be made of solder having the same melting point as the solder bump 20 or solder having a higher melting point than the solder bump 20. In this case, the same operation and effect can be obtained, but the manufactured semiconductor device 10 does not have the convex body 18. This is because the convex body 18 melts in the solder bump 20.
[0031]
FIG. 4 is a sectional view showing an example of another peripheral technique of the structure of the pad electrode portion for a semiconductor device according to the present invention .
Hereinafter, description will be given based on this drawing. However, the same parts as those in FIG.
[0032]
In FIG. 4, the semiconductor device 30 includes a pad electrode 32 covered with a protective film 22, a surface 34 of the pad electrode 32 protruding from the surface of the protective film 22, and a solder bump 36 formed on the pad electrode 32. It is. The pad electrode 32 has a side wall 38 protruding from the surface of the protective film 22 around the surface 34. The cross section of the pad electrode 32 perpendicular to the surface 34 of the pad electrode 32 is square. Gold plating (gold layer 322) for improving solder wettability is applied to the surface 34 and the side wall 38 of the pad electrode 32. According to the semiconductor device 30 of this embodiment, since the pad electrode 32 itself is the above-described convex body, the same operations and effects as the above-described convex body are exhibited.
[0033]
Next, an example of a method for manufacturing the semiconductor device 30 will be described. First, the aluminum electrode 140 is formed on the semiconductor chip 22. Subsequently, the protective film 22 is formed around the aluminum electrode 140 (first step) . Subsequently, a photoresist film (not shown) is formed on the protective film 22 (second step) . Subsequently, a nickel layer 321 is formed by electroless plating in a space surrounded by the protective film 22 and the photoresist film on the aluminum electrode 140 (third step) . Subsequently, the structure in which the surface 34 of the pad electrode 32 protrudes from the surface of the protective film 22 is obtained by removing the photoresist film. Subsequently, a gold layer 322 is formed on the nickel layer 321 by electroless plating (fourth step) . Finally, the solder bump 36 is formed on the pad electrode 32 by bringing the pad electrode 32 into contact with molten solder (not shown) (fifth step) .
[0034]
Further, the pad electrode 42 may be formed as follows. First, nickel is formed on the protective film 22 by sputtering or vapor deposition, a photoresist pattern is formed thereon, nickel is etched using this photoresist pattern, and finally the photoresist pattern is removed. When this nickel is etched, if the anisotropic etching such as RIE (reactive ion etching) is used, the nickel layer 321 having a square cross section can be easily obtained.
[0035]
Next, one embodiment of the structure of the pad electrode portion for a semiconductor device according to the present invention will be described with reference to FIG. Here, the same parts as those in FIG.
First, the knowledge that the inventor has completed the present invention will be disclosed.
The present inventor made pad electrodes with various angles between the isosceles trapezoidal leg and the base, and investigated the relationship between the angle and the shape of the solder bump (at this time, the pad was printed by screen printing or solder balls). Since the solder bump was formed on the electrode, the solder amount of the solder bump was constant). As a result, when the angle between the leg of the isosceles trapezoid and the base is changed, for example, from 0 ° to 90 °, the height of the solder bump gradually increases and reaches a maximum value at a certain angle and starts to decrease. Became. Therefore, it has been found that by using this phenomenon, solder bumps having different heights can be obtained even with the same amount of solder (see paragraph 0021).
[0036]
In the semiconductor device 40 according to the present embodiment, the periphery of the pad electrode 42 is covered with the protective film 22, the surface 44 of the pad electrode 42 protrudes from the surface of the protective film 22, and the solder bump 46 is formed on the pad electrode 42. It is. The pad electrode 42 has a side wall 48 protruding from the surface of the protective film 22 around the surface 44 thereof. The cross section of the pad electrode 42 perpendicular to the surface 44 of the pad electrode 42 is an isosceles trapezoid. Gold plating (gold layer 422) for improving solder wettability is applied to the surface 44 and the side wall 48 of the pad electrode 42. According to the semiconductor device 40 of the present embodiment, since the pad electrode 42 itself has the above-described convex body, the same operations and effects as the convex body in the peripheral technology described above are exhibited.
[0037]
The manufacturing method of the semiconductor device 40 is in accordance with the other peripheral technologies described above (see paragraph numbers “0026” to “0028”) .
However, when the nickel layer 421 is formed by electroless plating, the nickel layer 421 needs to be grown in a truncated cone shape. Therefore, a frustum-shaped opening is formed in the photoresist film used at this time by a method such as applying light from an oblique direction (space side wall processing step).
[0038]
Further, the pad electrode 42 may be formed as follows. First, nickel is formed on the protective film 22 by sputtering or vapor deposition, a photoresist pattern is formed thereon, nickel is etched using this photoresist pattern, and finally the photoresist pattern is removed. When etching the nickel, by using the isotropic etching such as wet etching, cross section can be easily obtained trapezoidal nickel layer 421.
[0039]
Further, the present inventor creates pad electrodes 42 with various angles θ between the legs of the isosceles trapezoid and the base, and contacts the pad electrodes 42 with molten solder (not shown) to form solder bumps 46. The relationship between the angle θ and the solder amount v and the height h2 of the solder bump 46 was examined.
As a result, when the angle θ is changed from, for example, 0 ° to 90 °, the solder amount v and the height h2 of the solder bump 46 gradually increase and reach a maximum value at a certain angle θmax and start to decrease. It was. Therefore , by utilizing this phenomenon, solder bumps 46 having different solder amounts v and heights h2 can be obtained even with the same pad electrode 42 area. Incidentally, when the angle θ is 90 ° is the pad electrode 32 shown in FIG. 4, the height of the solder bump 36 at that time is h1 (<h2).
[0040]
Incidentally, Te embodiment smell'm bumps may be used lead-free solder or the like. A wiring board (BGA) may be used instead of the semiconductor chip (FC).
[0041]
【The invention's effect】
Since the present invention is constructed and functions as described above, according to this, since the pad electrode is formed in an isosceles trapezoidal shape in cross section , solder is also deposited around the side wall as is apparent from FIG. amount of solder bumps also can be increased, which therefore, even on a small pad electrode having a surface product, to provide a structure and a manufacturing method thereof excellent semiconductor device pad electrode portions unprecedented that the solder bumps can be reliably formed Can do.
[0042]
In the case the cross section of the convex body is a trapezoidal shape, the force on the tip of the convex body is more concentrated, it can be further improved solder wettability can be discovered through background which led to the completion of the present invention It became a thing.
[0043]
Further, by isotropic etching while protecting the material to be convex body with the photoresist pattern, also know can be easily formed cross section of the convex body in a trapezoidal shape by utilizing the side etching of the lower photoresist pattern Got .
[0044]
Also, lever by the peripheral technologies and embodiments described above, the periphery of the pad electrode is covered by a protective film as described above, protrude the surface of the pad electrode from the surface of the protective film, solder bumps on the pad electrodes are formed As a result, the corners of the convex pad electrode easily enter the molten solder, whereby the pad electrode also easily contacts the molten solder, so that the solder wettability can be improved. Moreover, since the corner | angular part of a convex pad electrode pierces the oxide film of the molten solder surface, this also can improve solder wettability. Furthermore, since solder is also deposited on the side wall of the convex pad electrode, the amount of solder bumps can be increased. By these synergistic actions, solder bumps can be reliably formed even on pad electrodes having a small area.
[0045]
Further, if the cross section of the convex pad electrode is trapezoidal shaped, the force on the tip of the convex pad electrode is more concentrated, it is possible to further improve the solder wettability.
[0046]
Furthermore, when the cross section of the pad electrode perpendicular to the surface of the pad electrode is an isosceles trapezoidal shape, by changing the shape of the solder bump by changing the angle formed by the leg and the base of the isosceles trapezoidal shape, the same amount of solder can be obtained. On the other hand, solder bumps having different heights can be obtained. At this time, by forming the solder bump by bringing the pad electrode into contact with the molten solder, it is possible to obtain solder bumps having different solder amounts and heights even with the same pad electrode area.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a peripheral technique simultaneously devised by the inventors as a pad electrode part for a semiconductor device according to the present invention.
Figure 2 is a cross-sectional view showing a manufacturing method of a semiconductor device for pad electrode portion (mounting method) of definitive 1, step proceeds in order of FIG. 2 [1] to 2 [4].
3 is a cross-sectional view showing a step of FIG. 1 definitive semiconductor device pad electrode portion manufacturing method (implementation).
FIG. 4 is a cross-sectional view showing another peripheral technique simultaneously devised by the inventor as a pad electrode portion for a semiconductor device according to the present invention.
FIG. 5 is a cross-sectional view showing a structure of a pad electrode portion for a semiconductor device according to the present invention.
FIG. 6 is a cross-sectional view showing a conventional example .
7 is a cross-sectional view showing a method of manufacturing the semiconductor device in the conventional example of FIG. 6, and the process proceeds in the order of FIG. 7 [1] to FIG. 7 [3].
8 is a cross-sectional view showing a step in the method for manufacturing the semiconductor device of FIG. 6. FIG.
[Explanation of symbols]
10, 30, 40 Semiconductor device 12 Semiconductor chip 14, 32, 42 Pad electrode 161 Part on pad electrode 162 Remaining part on pad electrode 18 Convex body 20, 46 Solder bump 34, 44 Surface of pad electrode 36 Solder bump 38 , 48 Pad electrode sidewall
421 Nickel layer

Claims (1)

A first step of forming an aluminum electrode on the semiconductor chip and forming a protective film around the aluminum electrode around the aluminum electrode;
A second step of forming a photoresist film on the protective film;
A third step of forming a nickel layer on the aluminum electrode surrounded by the protective film and a photoresist film by electroless plating;
A fourth step of removing the photoresist film after the electroless plating and forming a gold layer on the nickel layer exposed by removing the photoresist film;
A fifth step of bringing the nickel layer into contact with the molten solder through the gold layer,
In the second step, a semiconductor and forming a space on the photoresist layer the aluminum electrode by applying a light from an oblique direction against the located in the space on the aluminum electrode to the frustoconical A method for forming a pad electrode part for a device.

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