JPH06112463A - Semiconductor device and mounting method thereof - Google Patents

Abstract

PURPOSE:To provide a semiconductor device where flip chips are easily mounted high in density and a mounting method thereof. CONSTITUTION:First bumps 5 and second bumps 6 smaller than the first bumps 5 in size but higher in melting point are provided between an IC chip 2 and a first bump 5. First of all, a self-alignment process is carried out when the first bumps 5 are formed by fusing, and then the IC chip 2 and the board 1 are very precisely positioned and connected. Then, the IC chip 2 and the board 1 are connected high in density with the second bumps 6.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention uses I through a plurality of bumps.
The present invention relates to a semiconductor device for exchanging electrical signals between a C chip and a substrate and a mounting method thereof, and particularly to a high density flip chip mounting technique.

[0002]

2. Description of the Related Art In the schematic cross-sectional views of FIGS.
The flip-chip mounting procedure described in Vol. 3, No. 12 (1984), pages 1004 to 1013 is shown. That is, in flip-chip mounting, bumps 5 made of, for example, Pb-Sn solder having a diameter of about 100 μm, which are formed by vapor deposition, are formed on the IC chip 2. On the other hand, the same bump 5 is formed on the substrate 1. The bumps 5 on the IC chip 2 thus formed are positioned with the bumps 5 on the substrate 1. The alignment at this time is performed using a half mirror before the butting. After that, when they are butted and heated and melted, the joining is completed. When the solder bumps 5 are melted, they are self-aligned at correct positions by the surface tension of the solder. Even if the bumps 5 are formed on either the IC chip 2 or the substrate 1, substantially the same effect can be expected. In addition, 3 is an input / output electrode, and 4 is a thin film.

Regarding flip chip mounting for the purpose of high density, there is a semiconductor device described in JP-A-4-155866. That is, in a photodiode for ultrahigh-speed optical communication, the diameter of the bump is as small as about 30 μm, and the self-alignment method by surface tension becomes difficult, so another method has been proposed. In the schematic sectional view of FIG.
2 shows the device shown here. According to this, OEIC1
A concave gold plating 4 is formed on the upper electrode 3 and Sn is
8 is vapor-deposited. On the other hand, the electrode 3 on the photodiode 2
On this, a convex gold plating 4 is formed. In such an apparatus, it is said that the concave and convex gold platings can be aligned with each other with high precision by fitting, and the Au-Sn eutectic alloy is formed by heating to achieve the bonding.

[0004]

However, when the method shown in FIG. 5 is used for increasing the density, the bump size becomes small, which makes positioning difficult and the surface tension also becomes small. The alignment effect cannot be expected and the desired bump connection becomes impossible. As a result, there arises a problem that the yield is significantly reduced.

On the other hand, the method shown in FIG. 6 for high density requires the formation of bumps having a complicated shape, and therefore can be used only for connecting expensive IC chips such as semiconductor lasers. Further, although the position can be confirmed relatively easily and the reliability of the connection is improved, since the connection is made by using the fitting in the solid state, a highly accurate positioning device with an error of 10 μm or less is indispensable. The mounting cost also increases and it cannot be applied to general-purpose component mounting.

The present invention has been made to solve the above problems, and provides a general-purpose semiconductor device which can be connected easily and with high reliability even in high-density flip-chip mounting, and a mounting method thereof. To do.

[0007]

The semiconductor device of the present invention comprises:
The bumps that connect the IC chip and the substrate are composed of first bumps that perform self-alignment and second bumps that have a higher melting point and a smaller size than the first bumps.

The semiconductor device mounting method of the present invention is
A step of forming a first bump material for forming a first bump after fusion bonding on an IC chip or a substrate and a second bump material for forming a second bump after fusion bonding, melting only the first bump material Then, the step of forming the first bump to form the high-precision positioning of the IC chip, and the step of melting and pressing the first bump and the second bump material after the positioning step to form the second bump are performed. It is something to give.

Further, a step of cooling the first and second bumps in a molten state after removing the applied pressure and solidifying the bumps is performed.

Then, the first bump material and the second bump material are formed of the same material at the same height on one of the IC chip and the substrate, and on the other, only the first bump material is different from the above material. It is made of material.

[0011]

In the semiconductor device of the present invention, self-alignment is performed by the first bump having a low melting point and a large size, and it is possible to easily position and connect with high precision, and the second bump having a high melting point and a small size is used. Allows density connections.

Further, in the mounting method, first, only the first bump material is melted and high-precision positioning can be performed by self-alignment without using a high-precision positioning device. Next, since the second bump material is melted and pressure-contacted to be connected, the second bump material is in a solid phase state during self-alignment, and it is possible to prevent the second bump material from being accidentally connected. The second bump provides reliable connection with high density.

Further, since the pressure is removed after the first and second bumps are melted and then cooled to solidify the bumps, the shape of the bumps can be controlled in addition to the above-mentioned action.
The long-term reliability of the joint is improved.

Then, the first bump material and the second bump material are formed on the one of the IC chip and the substrate with the same material and at the same height, and on the other, only the first bump material is formed with a material different from the above material. Therefore, the bump material forming process can be simplified.

[0015]

EXAMPLES Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1A to 1C are schematic sectional views showing a semiconductor device according to an embodiment of the present invention and a mounting method thereof in the order of steps. In the figure, 1 is a substrate, 2 is an IC chip, 3 is an input / output electrode, 4 is a thin film made of, for example, Au formed on the input / output electrode 3 for ensuring adhesion, and 5 is for self-alignment. For example, Pb40 with a melting point of 190 ° C
A first bump made of Sn60 solder, 5a is formed on the IC chip 2, 5A is a first bump material formed on the substrate 1, and in this case, the diameter is 100 μm and the height is 100 μm.
It is made of Pb40Sn60 solder which is the same as the first bump 5 in μm. 6 is a second bump made of Pb70Sn30 having a higher melting point and a smaller size than the first bump 5, for example, a melting point of 260 ° C., and 6a is formed on the IC chip 2.
6A is a second bump material formed on the substrate 1. In this case, the second bump 5 has a diameter of 30 μm and a height of 30 μm.
The same Pb70Sn30 is used. Reference numeral 7 is a pressing force for contacting the second bump.

First, the first bump materials 5a and 5A and the second bump materials 6a and 6A are laminated and vapor-deposited with Pb and Sn having the above-mentioned compositions, respectively, and then melted by heating in a nitrogen atmosphere. 1 and the IC chip 2 are formed.
The IC chip 2 is positioned and brought into contact with the substrate 1 (FIG. 1 (a)). At this time, the first bump materials 5a and 5A are in contact with each other, but the second bump materials 6a and 6A are still kept apart. Next, the first bump 5, that is, the first bump material 5
It is heated to 210 ° C. by a hot plate, for example, above the melting point of a, 5A and below the melting point of the second bump 6, that is, the second bump material 6a, 6A. As a result, the first bump material 5
Only a and 5A are melted and connected to form the first bump 5 (FIG. 1B). At this time, the positioning is performed with high accuracy by self-alignment. Further the second bump material 6
a and 6A or higher, for example, 280 ° C. to form a second bump 6 by connecting by heating and contacting (FIG. 1).
(c)). At this time, since the first bump 5 maintains a certain height due to the surface tension, it is necessary to press the IC chip 2 in order to bring the second bump materials 6a and 6A into contact with each other. In order to heat the second bump members 6a and 6A to a temperature equal to or higher than the melting point, for example, the temperature of the hot plate may be rapidly increased. It is preferable to heat. As a result, even if a plurality of IC chips 2 are mounted on the substrate 1, high-density bonding can be sequentially performed by using the pressing / heating jig. The connection is completed by cooling the IC chip 2 under pressure.

In this embodiment, only the first bump having a low melting point and a large size, that is, the first bump material is melted and the self-alignment can be performed easily and highly accurately without using a highly accurate positioning device. Gime connection is possible. At this time, the second bump material is in a solid phase state, which can prevent the second bump from being erroneously connected, and then melts the second bump material in a positioned state to have a high melting point and a large size. The small second bump facilitates reliable, high density connections. Even if a high-precision positioning device is not used, high-density flip-chip mounting can be performed without causing connection errors due to self-alignment in the conventional device.

Example 2. Another embodiment of the method of mounting the semiconductor device shown in FIG. 1 will be described. The process is the same as that of the first embodiment until the second bump 6 is heated to a temperature equal to or higher than the melting point, but the applied pressure is removed in a molten state of the first bump 5 and the second bump 6, and the bump is cooled. Solidify. Therefore, the height of the first bump 5 and the second bump 6 is increased by the amount of the pressing force. At this time, the numbers and sizes of the first bumps 5 and the second bumps 6, that is, the first bump materials 5a and 5A and the second bump materials 6a and 6A are set so that the second bumps 6 do not constrict and separate. The shape of the first and second bumps 5 and 6 can be controlled by designing from the balance of forces. It is well known that the shape of the bumps affects the long-term reliability of the joint (see Proceedings of the Japan Institute of Metals, Vol. 23, No. 12). By doing so, the life can be significantly extended.

Next, the effect of self-alignment in the semiconductor device mounting method of the above embodiment will be described with reference to the schematic sectional views of FIGS. 2 (a) to 2 (c). Here, for example, the diameter of the first bump material 5a, 5A is 100 μm, and the size of the second bump material 6a, 6A, 6b, 6B is 50 μm.
It is assumed that the distance between the bumps is about 40 μm. As shown in FIG. 2 (a), the bump position shift is 60 μm in the lateral direction,
If 30 μm is generated in the front-back direction of the paper surface, the first bumps 5 come into contact with the predetermined bump materials 5a and 5A, respectively, but the second bumps 6 have circuits different from the design and the second bump materials 6B and 6a. Will be formed in. However, as shown in FIG. 2B, when the first bumps 5 are melted, surface tension acts in the direction indicated by the arrow, and the second bump materials 6B and 6a in the solid state in which the surface tension does not act The wrong circuit is opened. As a result, self-alignment becomes possible as shown in FIG. Further, the connection is completed by heating and contacting the melting point of the second bump or higher. As described above, in the face-down assembly using the flip chip, the high density of 50 μm pitch level can be achieved with high reliability.

Further, as shown in FIGS. 1 and 2, in the above embodiment, the first bump 5, that is, the first bump material 5 is used.
Although a and 5A are formed at the corners of the IC chip 2, they are not limited to these as long as effective surface tension works. That is, as shown in the plan views of FIGS. 3 (a) and 3 (b), with respect to the positional deviation in the parallel direction, the same surface tension acts wherever the bump is formed in the IC chip surface. However, as for the rotation direction, it works as a rotation force around the IC chip,
No effect at the center. Therefore, the position and shape of the first bump 5 are arranged in consideration of the above points.

The surface tension acts on each bump,
Since the IC chip 2 is moved by the total of the forces, the number of the first bumps 5 can be easily designed by considering this point.

Although the shape of the first bump 5, that is, the first bump material 5a, 5A has been described as a spherical shape in the above embodiments of FIGS. 1 and 2, the shape is not limited to this.
It suffices that the IC chip 2 be moved by the surface tension of the first bumps 5 and highly accurate positioning be performed. For example, by forming a plurality of rectangular parallelepipeds along the vicinity of the outer periphery of the IC chip 2, the surface tension also works and self-alignment becomes possible. However, as the bump becomes longer, the flow of the bump material occurs and the clearance between the substrate 1 and the IC chip 2 changes,
Be careful as it may cause defects.

Further, in the above-mentioned embodiment, the case of the solder bump has been described, but it goes without saying that the material can be formed by a method such as vapor deposition with a material other than the solder and the same effect can be expected.

In the above embodiment, the case where the bump material is formed on both the substrate side and the IC chip side has been described, but it is not always necessary to form it on both sides, and it may be formed on at least one of them.

Further, in the above embodiment, the case where the bump material is formed of the same material as the bump has been described.
The bump material may be different from the material of the bump, and the desired bump material (composition) may be obtained by the bump material on the substrate side and the IC chip side.

Example 3. This example will be described with reference to the schematic sectional view of FIG. Only the first bump materials 5A and 5B are formed on the substrate 1 side, and the first bump materials 5a and 5B are formed on the IC chip 2 side.
b and the second bump materials 6a and 6b are formed. As the material, for example, Sn is used for the first bump materials 5A, 5B on the substrate 1 side, and the first bump materials 5a, 5b on the IC chip 2 side are used.
95Pb5Sn is used for the second bump materials 6a and 6b, respectively.
Is selected. The manufacturing method when the semiconductor device as described above is configured is similar to the above, but since the material of the first bump material is different between the substrate side and the IC chip side, the first bump on the substrate 1 side is first heated by heating. The materials 5A and 5B react with the first bump materials 5a and 5b on the IC chip side to become an alloy composition of PbSn and melt. The composition ratio of the PbSn thus formed, that is, the composition ratio of the first bump, that is, the melting point, can be controlled by the size of the first bump material on the substrate 1 side and the IC chip 2 side. For example, if the above composition has the same size, the first bump has a composition of Pb47.5Sn52.5 and a melting point of about 200 ° C.
Becomes the melting point of the second bump, that is, the second bump material (about 3
10 ° C) lower and double the size. Next, the second bumps are connected by heating and press contact with each other at a temperature higher than the melting point of the second bumps. In short, if the semiconductor device is configured such that the second bump has a higher melting point and a smaller size than the first bump, the same effect as that of the above embodiment can be obtained. In addition,
In this embodiment, since the location where the bump material is formed and the type of the bump material are specified, that is, it is sufficient to form the bump material of the same type and the same height on the substrate side and the IC chip side, respectively. The forming process can be simplified and the industrial value is greatly improved.

In the above embodiment, both the first bump and the second bump were formed on the input / output electrodes. However, the first bump is a dummy bump for positioning, and the second bump is formed on the IC chip and the substrate. It may also be a bump on the input / output electrodes for exchanging electrical signals.

[0028]

As described above, the semiconductor device of the present invention has the first bump for self-aligning the bump connecting the IC chip and the substrate, and the melting point higher and the size smaller than the first bump. Since it is configured with the second bump, self-alignment can be easily performed with the first bump for highly accurate positioning and connection, and high density connection can be achieved by using the second bump for higher packaging density. Can handle. Even if a high-precision positioning device is not used, high-density flip-chip bonding can be performed by a conventional device without causing connection errors due to self-alignment.

The method of mounting the semiconductor device is
A step of forming a first bump material for forming a first bump after fusion bonding and a second bump material for forming a second bump after fusion bonding on a chip or a substrate, melting only the first bump material. A step of forming a first bump by high-precision positioning of the IC chip, and a step of melting and pressing the first bump and the second bump material to form a second bump after the positioning step. It is a thing.

Furthermore, since the applied pressure is removed in the molten state of the first and second bumps and then the bumps are cooled to solidify the bumps, long-term reliability is ensured by controlling the shape of the bumps after connection. It is possible to improve the property.

Then, the first bump material and the second bump material are formed on the one of the IC chip and the substrate with the same material and at the same height, and on the other, only the first bump material is formed with a material different from the above material. As a result, the bump material forming process can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a method of mounting a semiconductor device according to an embodiment of the present invention in the order of steps.

FIG. 2 is a schematic cross-sectional view explaining the operation relating to the method for mounting a semiconductor device of the present invention.

FIG. 3 is a plan view illustrating a position of a first bump and an effect of self-alignment according to the present invention.

FIG. 4 is a schematic sectional view showing a method of mounting a semiconductor device according to another embodiment of the present invention.

5A to 5C are schematic cross-sectional views sequentially showing a method of mounting a conventional semiconductor device.

FIG. 6 is a schematic sectional view showing a conventional semiconductor device having a high density.

[Explanation of symbols]

 1 Substrate 4 Thin Film 5 First Bump 5a, 5A, 5b, 5B First Bump Material 6 Second Bump 6a, 6A, 6b, 6B Second Bump Material 7 Pressure

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[Procedure amendment]

[Submission date] December 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The first bump material and the second bump material are made of the same material on either the IC chip or the substrate.
Form shape, the other was only the first bump materials so as to form a different material as the material.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014] Then, form the shape of the first bump material and the second bump material to either the IC chip or the substrate of the same material, the other forms only the first bump materials with different material as the material The bump material forming process can be simplified.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

Example 3. This example will be described with reference to the schematic sectional view of FIG. Only the first bump materials 5A and 5B are formed on the substrate 1 side, and the first bump materials 5a and 5B are formed on the IC chip 2 side.
b and the second bump materials 6a and 6b are formed. As the material, for example, Sn is used for the first bump materials 5A, 5B on the substrate 1 side, and the first bump materials 5a, 5b on the IC chip 2 side are used.
95Pb5Sn is used for the second bump materials 6a and 6b, respectively.
Is selected. The manufacturing method when the semiconductor device as described above is configured is similar to the above, but since the material of the first bump material is different between the substrate side and the IC chip side, the first bump on the substrate 1 side is first heated by heating. The materials 5A and 5B react with the first bump materials 5a and 5b on the IC chip side to become an alloy composition of PbSn and melt. The composition ratio of the PbSn thus formed, that is, the composition ratio of the first bump, that is, the melting point, can be controlled by the size of the first bump material on the substrate 1 side and the IC chip 2 side. For example, if the above composition has the same size, the first bump has a composition of Pb47.5Sn52.5 and a melting point of about 200 ° C.
Becomes the melting point of the second bump, that is, the second bump material (about 3
10 ° C) lower and double the size. Next, the second bumps are connected by heating and press contact with each other at a temperature higher than the melting point of the second bumps. In short, if the semiconductor device is configured such that the second bump has a higher melting point and a smaller size than the first bump, the same effect as that of the above embodiment can be obtained. In addition,
In this embodiment, since the place where the bump material is to be formed and the type of the bump material are specified, that is, it is sufficient to form the bump material of the same type and substantially the same height on each of the substrate side and the IC chip side. The formation process of can be simplified and the industrial value is greatly improved.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

[0031] Then, form the shape of the first bump material and the second bump material to either the IC chip or the substrate of the same material, on the other so as to form only the first bump materials with different material as the material Therefore, the bump material forming process can be simplified.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 27/15 8934-4M

Claims (4)

[Claims] 1. A semiconductor device for exchanging electrical signals between an IC chip and a substrate through a plurality of bumps,
The first bump that self-aligns the above bump,
And a semiconductor device comprising a second bump having a higher melting point and a smaller size than the first bump. 2. A method for mounting a semiconductor device, wherein an IC chip and a substrate are bonded via the first and second bumps according to claim 1, wherein the first bump after fusion bonding to the IC chip or the substrate. A step of forming a second bump material for forming a second bump after fusion bonding with a first bump material for forming the first bump material, and forming a first bump by melting only the first bump material to form the first bump material. A method of mounting a semiconductor device, comprising: performing a step of performing highly accurate positioning; and a step of forming a second bump by melting and pressing the first bump and the second bump material after the positioning step. 3. The method for mounting a semiconductor device according to claim 2, wherein a step of cooling the first and second bumps in a molten state after removing the applied pressure to solidify the bumps is performed. . 4. A first bump material and a second bump material are formed of the same material at the same height on either one of an IC chip or a substrate, and on the other, only the first bump material is different from the above material. 4. The method for mounting a semiconductor device according to claim 2, wherein the mounting method is made of a material.