JP3090414B2 - Solder bump connection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor module using solder bumps capable of high-precision, high-density terminal connection and excellent workability, and a method of connecting solder bumps.

[0002]

2. Description of the Related Art Conventional methods for connecting terminals between a semiconductor chip and a wiring board include a wire bonding method and TAB (Tape A).
The utomated bonding method and the flip chip method are generally known (reference examples: Handbook for Semiconductor Packaging Technology, published by Science Forum Co., Ltd.). The wire bonding method is a method for easily connecting terminals using a fine bonding wire such as Au or Al.
It is said that a wire having a diameter of about 30 μm is used, and the terminal pitch is about 150 μm as a limit. The TAB method is a method of connecting using lead terminals plated with Au. At present, the terminal width is about 50 μm.
It is said that the limit is about 100 μm pitch in m. On the other hand, the flip-chip method is a method of connecting between a semiconductor chip and a substrate by using small solder bumps having a diameter of about 100 μm. Terminals can be taken out from the entire surface of the semiconductor chip, so that high-density connection is possible. is there. Also, since the connection length is short, the stray capacitance and the parasitic inductance of the connection portion can be reduced as much as possible, so that it has become an important technique as a terminal connection method for a high-speed LSI.

However, the conventional flip-chip method requires a step of forming solder directly on the electrode terminals after forming a semiconductor element or the like on a semiconductor substrate, so that the process is complicated, the yield is low, and the productivity is low. There was a problem of inferiority. For this reason, a method has been developed in which a large number of solder bumps are formed on a carrier substrate, the bumps are transferred onto electrodes of a semiconductor element, and flip-chip connected to the substrate (see Japanese Patent Application No. 3-335287). . FIG. 8 shows schematic steps of this method.

That is, after a dot-shaped solder layer 2 is formed on a transfer carrier substrate 1 having poor solder wettability by patterning (a), the transfer carrier substrate 1 is positioned on the electrodes 4 of the semiconductor chip 3. Then, by melting the solder, the solder layer 2 on the transfer carrier substrate 1 is transferred onto the electrodes 4 of the semiconductor chip 3 to form the solder bumps 5 (c). Further, the semiconductor chip 3 is aligned with the electrode 7 on the wiring board 6 (d), and the solder bump 5
This is a method (e) of flip-chip connection by reflowing.

[0005]

However, in the steps of FIGS. 8B and 8C in which the solder layer 2 is transferred onto a desired electrode 4 to form a solder bump 5, a large number of solder layers are completely removed. Transferring and forming the solder bumps 5 is an issue. Therefore, as shown in FIG.
There is a method in which a small electrode 8 having excellent wettability with solder is formed and transferred on the surface of the transfer carrier substrate 1 where the solder layer 2 is formed so that the position does not move. Under the above melting conditions, not only the solder bumps 5 transferred onto the electrodes 4 but also the bumps 5A which cannot be transferred onto the electrodes 4 are generated. FIG. 10 shows the transfer carrier substrate 1 so that the position of the solder bump 5 does not move.
There is a method in which a small concave portion 12 is formed and transferred. However, under the solder melting conditions using the flux 9, the bump 5A that cannot be transferred to the electrode 4 as shown in FIG.
The problem is to completely transfer a large number of solder bumps 5 onto a desired electrode 4.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional transfer bump method and to provide a method of connecting solder bumps in which a solder layer is completely transferred onto electrodes and a semiconductor chip on which solder bumps are formed is obtained. To provide.

[0007]

According to a first aspect of the present invention, before forming a dot-shaped solder layer on a transfer carrier substrate, the dot-shaped solder layer is formed on the transfer carrier substrate below the solder layer. It is smaller than the shape of the solder layer, has a pattern shape that increases in area toward the center, and has at least two layers. The upper layer is a metal film that has excellent wettability with solder and is alloyed with solder. A metal film for transfer, which is a metal film having poor wettability, is used as a carrier substrate for transfer.

In a second aspect of the present invention, before the dot-shaped solder layer is formed on the transfer carrier substrate, the solder layer is formed on the transfer carrier substrate below the solder layer and has a shape smaller than the shape of the solder layer. A concave portion having a pattern shape whose area increases toward the center is formed, and this is used as a transfer carrier substrate.

In a third aspect of the present invention, before forming a dot-shaped solder layer on the transfer carrier substrate, the shape of the solder layer is smaller than the shape of the solder layer on the transfer carrier substrate below the solder layer. A concave portion having a pattern shape whose area increases toward the bottom is further formed, and further, at least two layers are formed on the concave portion, the upper layer is a metal film excellent in wettability with solder and alloyed with solder, and the lower layer is formed of solder. A transfer metal film is formed as a metal film having inferior wettability, and is used as a transfer carrier substrate.

A fourth aspect of the present invention is characterized in that a single-layer film made of a material having excellent wettability with a solder layer is used as the transfer metal substrate instead of the two-layer film as the transfer metal film. Is what you do.

[0011]

According to the present invention, there is provided a material having a pattern shape in which the area increases toward the center on a transfer carrier substrate and a material having excellent wettability with a solder layer or a material having poor wettability by the above-described method. Forming a transfer metal film made of a material having excellent wettability with a single layer film or a multilayer film made of a desired material combination, or forming a concave portion having a pattern shape in which the area increases toward the center Or,
The solder layer can be melted by using a combination of these metal films and concave portions, or by using a single-layer film with excellent wettability with solder and using a metal that alloys the solder as a transfer metal film. In the process of forming a ball-shaped bump, the molten solder tends to gather at the center.

[0012]

1 to 7 show the first to third embodiments of the present invention. 1, 2, 4, 5, 6, and 7, the solder layer 2 is shown as being transparent. 1 to 7 show only one solder layer 2.

Embodiment 1 FIGS. 1 to 3 show a first embodiment of the present invention.
1 and 2 are explanatory views of a transfer carrier substrate, and FIG. 3 is an explanatory view of a process of forming solder bumps. As shown in FIG. 1, a star-shaped pattern shape as a pattern shape whose area increases toward the center on the transfer carrier substrate 1, and a material excellent in wettability with the solder layer 2 and a material poor in wettability A two-layer film made of a combination of the desired materials described above, wherein the lower layer is formed of a metal film 12 having poor wettability with solder such as Ti, and the upper layer is formed of a metal film 13 having excellent wettability with solder such as Au. Transfer metal film 1
1 is formed and used as the carrier substrate 1 for transfer. As a substrate material having poor wettability with solder, for example, a transfer metal film 11 having a star pattern shape having a diameter smaller than the diameter of the solder layer 2 is formed on a transfer carrier substrate 1 made of silicon, titanium, molybdenum or the like. For example, Ti / Au (the lower side is Ti and the upper side is Au) is formed. Next, a film-like thick film resist (for example, "Liston" (trade name of DuPont) or a liquid resist (for example, AZ-based resist of Hoechst)) is applied on the transfer metal film 11, and the solder layer 2 is formed. Is formed by exposing and developing a portion for forming a solder layer, and after forming a large number of solder layers 2 at the same time by a vacuum deposition method or the like, the resist is removed by a lift-off technique to form the solder layer 2 as shown in FIG.

FIG. 2 shows a state in which the solder is melted to form a solder ball (solder bump). When heated and melted in a vacuum, a reducing atmosphere such as hydrogen, or a flux atmosphere, the transfer metal film is formed. Since the pattern 11 has a pattern shape in which the area increases toward the center, the molten solder tends to concentrate at the center (see FIG. 2A), and the metal film having excellent inner wettability of the transfer metal film 11. No. 13 is a metal film 1 which is alloyed with solder and has poor wettability with solder.
2, that is, leaving the Ti, the solder bump 5 can be formed at the same center position as the center of the transfer metal film 11 (FIG. 2B).
reference).

FIG. 3 shows an alignment of the semiconductor chip 3 on which the electrodes 4 are formed at positions opposed to the solder layer 2 (see FIG. 3A), in a vacuum, in a reducing atmosphere such as hydrogen, or in a flux atmosphere. When the inside is heated and melted, the solder bump 5 having the same center position as the center of the underlying metal film 12 can be formed as described with reference to FIG. 2 (see FIG. 3B). Subsequent bonding steps are the same as those shown in FIGS. 8D and 8E.

In this embodiment, the transfer metal film 11 has a two-layer structure. However, the transfer metal film 11 may have a multi-layer structure. In short, the uppermost layer is easily wettable with the solder and is alloyed with a metal film. The base may be any metal film that is hardly wetted by solder.

[Embodiment 2] FIGS. 4 and 5 show a second embodiment of the present invention, in which a star-shaped pattern is formed on a transfer carrier substrate 1 so that its area increases toward the center. This is an embodiment of a method of forming a concave portion 14 having a shape and using the concave portion 14 as a transfer carrier substrate.

FIG. 4 shows a specific configuration.
As a substrate material having poor wettability with solder, for example, a concave portion 14 having a star pattern shape smaller in diameter than the diameter of the solder layer 2 is formed on a transfer carrier substrate 1 made of silicon, titanium, molybdenum or the like. It is formed by etching or reactive ion etching. Next, the solder layer 2 is formed on the concave portion 14 by the method shown in FIG.

FIG. 5 shows a state in which the solder is melted and the solder bumps 5 are formed in the second embodiment. The pattern shape in which the area of the concave portion 14 increases toward the center when heated and melted is shown. Therefore, the molten solder is easily concentrated at the center (see FIG. 5A), and the solder bump 5 can be formed at the same center position as the center of the concave portion 14 (FIG. 5).
(B)). The process of forming the transfer solder bumps 5 on the semiconductor chip is substantially the same as that shown in FIG. 3, and when heated and melted, the vicinity of the same center position as the center of the concave portion 14, that is, the opposite semiconductor chip The solder bumps 5 can be formed on the electrodes. The subsequent bonding step is the same as that shown in FIGS. 8D and 8E.

[Embodiment 3] FIGS. 6 and 7 show a third embodiment of the present invention. On a transfer carrier substrate 1, a star-shaped pattern having an area increasing toward the center is shown. The lower layer is wetted with a two-layer film made of a desired material combination of a material having excellent wettability with the solder layer 2 and a material having poor wettability on the recess 14 while forming the concave portion 14 having a pattern shape. This is an embodiment of a method in which a metal film 12 made of a material having poor wettability and a metal film 13 whose upper layer is made of a material excellent in wettability are used as the carrier substrate 1 for transfer.

FIG. 6 shows a specific configuration. As a substrate material having poor wettability with solder, a transfer carrier substrate 1 made of, for example, silicon, titanium, molybdenum, or the like is used. After forming a concave portion 14 having a star-shaped pattern shape with a diameter smaller than the diameter by chemical etching or reactive ion etching,
A two-layer film made of a desired material combination of a material having excellent wettability with the solder layer 2 and a material having poor wettability on the concave portion 14, the lower layer being the metal film 12 having poor wettability, and the upper layer being wettability. The transfer metal film 11 made of the excellent metal film 13 is formed, and the concave portion 15 with the transfer metal film is formed. Next, the solder layer 2 is formed on the transfer metal film-provided concave portion 15 by the method shown in FIG.

FIG. 7 shows that the solder is melted and the solder bump 5
7 shows that when the solder is heated and melted, the molten solder tends to concentrate at the center because the pattern shape is such that the area of the concave portion 15 with the metal film for transfer increases toward the center (FIG. 7 ( a)), the solder bump 5 having the same center position as the center of the concave portion 14 can be formed.
(B)). The process of forming the transfer solder bumps 5 on the semiconductor chip is substantially the same as that shown in FIG. 3, and when heated and melted, the vicinity of the same center position as the center of the concave portion 14, that is, the opposite semiconductor chip Solder bumps 5 can be formed on the electrodes. The subsequent bonding step is the same as that shown in FIGS. 8D and 8E.

In this embodiment, the transfer metal film 11 has a two-layer structure. However, the transfer metal film 11 may have a multi-layer structure. It is sufficient that the base is a metal film that is not easily wetted by solder.

Embodiment 4 In Embodiments 1 and 3,
Although the transfer metal film 11 was composed of the metal film 12 having poor wettability and the metal film 13 having excellent wettability, the transfer metal film 11 was excellent in wettability with solder in place of the two-layer transfer metal film 11, and Alternatively, a single-layer film of a metal alloying with solder can be used.

In each of the embodiments described above, the configuration in which the transfer metal film 11 and the concave portion 14 are formed in the form of a star pattern is shown. However, any pattern may be used as long as the area increases toward the center. It is obvious that the simplest example has a triangular pattern shape and is not limited by the pattern shape. The same applies to the material of the transfer carrier substrate 1 and the transfer metal film 11.

[0026]

As described above, the present invention has a pattern shape in which the area increases toward the center on the carrier substrate for transfer, and is a material excellent in wettability with the solder layer or poor in wettability. A transfer metal film whose uppermost layer is made of a material having excellent wettability with a single-layer film or a multilayer film composed of a desired material combination of materials, or a concave portion having a pattern shape in which the area increases toward the center. Forming or
With the configuration in which the transfer metal film and the concave portion are combined, the molten solder easily gathers at the center in the step of melting the solder layer to form a ball-shaped bump, and the central position of the transfer metal film and the concave portion is reduced. Solder balls can be formed on the substrate.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of the first embodiment of FIG. 1;

FIG. 3 is an explanatory diagram of an operation of the first embodiment of FIG. 1;

FIG. 4 is a plan view and a sectional view of a main part showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of the operation of the second embodiment.

FIG. 6 is a plan view and a sectional view of a main part showing a third embodiment of the present invention.

FIG. 7 is an explanatory diagram of the operation of the third embodiment of FIG. 6;

FIG. 8 is an explanatory view of a conventional flip-chip soldering method.

FIG. 9 is an explanatory view of a conventional flip-chip soldering method.

FIG. 10 is an explanatory view of a conventional flip-chip soldering method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transfer carrier substrate 2 solder layer 3 semiconductor chip 4 electrode on semiconductor 5 solder bump 5A bump that cannot be transferred onto electrode 6 wiring board 7 electrode on wiring board 8 electrode 9 flux 10 recess 11 transfer metal film 12 with solder Metal film with inferior wettability 13 Metal film with excellent wettability with solder 14 Star-shaped pattern concave part 15 Concave part with metal film for transfer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nobuo Sato 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (56) References JP-A-6-84922 (JP, A) Kaihei 5-243232 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/60

Claims (4)

(57) [Claims] 1. A plurality of dot-shaped solder layers having a desired shape and pitch are formed on a transfer carrier substrate having poor wettability with solder, and an electrode portion of a semiconductor chip is formed at a position facing the solder layer. By aligning and heating and melting the solder layer, the solder layer is transferred to the electrode portion of the semiconductor chip to form a solder bump.Furthermore, the semiconductor chip on which the solder bump is formed is connected to a wiring board or After being aligned with the electrode portion of another semiconductor chip, the solder bump is heated and melted again,
In a method for connecting a solder bump for connecting terminals between an electrode portion of the semiconductor chip and an electrode of the wiring board or another semiconductor chip, it is preferable that, before forming a dot-shaped solder layer on the transfer carrier substrate, On the transfer carrier substrate below, a pattern shape smaller than the shape of the solder layer, the area increases toward the center, and at least two layers are formed, and the upper layer has excellent wettability with solder, and A transfer metal film is formed as a metal film that is alloyed with the metal, and the lower layer is a metal film having poor wettability with solder. A transfer bump is formed by using the transfer metal film as a transfer carrier substrate, and a wiring board or other semiconductor is formed. A method of connecting solder bumps, which comprises connecting bumps to a chip. 2. A plurality of dot-shaped solder layers having a desired shape and pitch are formed on a transfer carrier substrate having poor wettability with solder, and an electrode portion of a semiconductor chip is formed at a position facing the solder layer. By aligning and heating and melting the solder layer, the solder layer is transferred to the electrode portion of the semiconductor chip to form a solder bump, and further, the semiconductor chip on which the solder bump is formed is connected to a wiring board or After being aligned with the electrode portion of another semiconductor chip, the solder bump is heated and melted again,
In a method of connecting a solder bump for connecting a terminal between an electrode portion of the semiconductor chip and an electrode of the wiring board or another semiconductor chip, the method further comprises: forming a dot-shaped solder layer on the transfer carrier substrate; On the transfer carrier substrate below, a recess having a pattern shape smaller than the shape of the solder layer and having an area increasing toward the center is formed, and a transfer bump is formed using this as a transfer carrier substrate. And a bump connection to a wiring board or another semiconductor chip. 3. A plurality of dot-shaped solder layers having a desired shape and pitch are formed on a transfer carrier substrate having poor wettability with solder, and an electrode portion of a semiconductor chip is formed at a position facing the solder layer. By aligning and heating and melting the solder layer, the solder layer is transferred to the electrode portion of the semiconductor chip to form a solder bump, and further, the semiconductor chip on which the solder bump is formed is connected to a wiring board or After being aligned with the electrode portion of another semiconductor chip, the solder bump is heated and melted again,
In a method of connecting a solder bump for connecting a terminal between an electrode portion of the semiconductor chip and an electrode of the wiring board or another semiconductor chip, the method further comprises: forming a dot-shaped solder layer on the transfer carrier substrate; On the transfer carrier substrate below, a concave portion having a pattern shape smaller than the shape of the solder layer and increasing in area toward the center is formed, and further, at least two layers are formed on the concave portion and the upper layer is formed of solder. A transfer metal film is used, which is a metal film that has excellent wettability with solder and is alloyable with solder, and the lower layer is a metal film with poor wettability with solder. Forming a bump and connecting the bump to a wiring board or another semiconductor chip. 4. A metal film for transfer according to claim 1 or 3, wherein a metal having excellent wettability with a single layer film and alloying with the solder is used instead of the two layer film. The connection method of the solder bump.