JP2003243444A - Substrate mounting structure and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate mounting structure surely formed with an underfill material unfilled region. <P>SOLUTION: The substrate mounting structure is mounted with a chip like OEIC chip 1 to a mounting substrate 5 in the form of a flip chip, and filled with the underfill material between the substrate 5 and the chip 1. A groove 3 for preventing the invasion of the underfill material is formed at at least either a part of the mounting substrate or chip 1, and there is provided the underfill material unfilled region. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a board mounting structure and a semiconductor device. In particular, it relates to flip-chip bonding mounting, and partially blocks the infill material that is normally used during flip-chip bonding to protect part of the flip-chip semiconductor chip from intruding the underfill material. To do.

[0002]

2. Description of the Related Art With the rapid increase in demand for the Internet and the like, there is an urgent need to expand communication capacity. As a method for expanding the communication capacity in optical communication, a time division multiplexing (TD) method for increasing the processing speed of each communication and multiplexing a plurality of signals is used.
The M) method and the wavelength division multiplexing (WDM) method for multiplexing signals by using a plurality of different wavelengths have been proposed. When the TDM method is adopted, it is inevitably necessary to increase the speed of the signal flowing in the fiber. However, when the speed of the electric signal becomes about 60 Gbit / s or more, the effect of the skin effect and parasitic capacitance peculiar to the electric signal becomes remarkable and the loss becomes large, which makes it difficult to input / output the high speed electric signal to / from the package. Become.

As one measure against such a problem, research and development of an optical-electrical integrated circuit (OEIC) which employs an optical interface for high-speed signals is being conducted.
As one example of adopting the optical / electrical fusion interface, a high-speed photodiode having a high saturation current characteristic and 4
A digital OEIC having a receiver function, which is a monolithically integrated InP-based digital IC capable of high-speed operation of 0 Gbit / s or more, has been realized. Here, as the photodiode, an element having a light receiving portion of a planar structure is adopted, but in this case, it is necessary to input / output an optical signal in a direction perpendicular to the electrode terminal surface of the electronic circuit, When it is inserted, it is necessary to provide the fiber connection terminal vertically to the electric terminal arranged on the side surface. Actually the OE
When mounting an IC on a package, it is extremely difficult to align the optical system, and in consideration of mounting the package on a board, the electric input / output terminal and the optical input / output terminal must be present vertically. Is not a preferred structure. Note that the wavelength normally used for optical communication is 1.55 μm
Since the band light can pass through the InP substrate, even if the signal light is incident from the back surface of the substrate, it can be supplied to the photodiode formed on the front surface of the substrate.

An OEIC in which a photodiode having a waveguide type light receiving section is integrated with an analog amplifier circuit has also been reported. When a waveguide type element is used, it has good compatibility with the optical waveguide and is excellent in connection with an external optical fiber, but its size is laterally long and there is a problem in terms of device miniaturization. Since the clad layer for confinement is required, the device structure becomes thicker than that of the planar type. For this reason, it is possible to monolithically integrate as long as it is an analog amplifier circuit, but it is extremely difficult to monolithically integrate a digital signal processing IC having a large circuit scale, and it has not been realized yet.

OEI with optical / electrical interface
In realizing C, there is a demand for arranging all the optical and electric input / output terminals on the side surface of the package from the viewpoint of mounting. Also, in order to reduce the cost of mounting,
From the "active alignment" that fixes the optical alignment between the OEIC chip and the external optical fiber while observing the characteristics, it is possible to simply install and fix both at a predetermined position without performing the alignment while observing the characteristics. A mounting method is desired because optical alignment can be performed by “sib alignment”.

As one structure to meet such demands, there has been proposed a structure in which an optical wiring structure and an optical path changing structure are manufactured on an optical semiconductor chip and mounted by using a flip chip bonding technique (FIG. 10). . The flip-chip connection is used here because the flip-chip can be extremely accurately aligned with the mounting substrate by the self-alignment function by the surface tension of the solder bump.

However, in the mounting using the flip chip bonding technique, since the mechanical connection strength between the substrate and the flip chip is weak, an adhesive agent called an underfill material is filled between the substrate and the chip to make the mechanical connection strength. It is common to reinforce. The filling of the underfill material is performed as shown in FIG. After electrically connecting the chip and the mounting substrate with solder bumps or the like, an underfill material that is a liquid is inserted into the gap between the chip and the mounting substrate by utilizing the capillary phenomenon. After that, the underfill material is dried and solidified by heat treatment or the like. This increases the mechanical connection strength. Here, in order to obtain sufficient connection strength, it is usual to fill the underfill material in an amount that spreads over the entire surface of the chip to be flip-chip connected.

When an optical semiconductor chip is flip-chip mounted, since an optical signal interface exists on the surface or side surface of the optical semiconductor chip, if an underfill material is filled between the mounting substrate and the flip chip by using a capillary phenomenon, an underfill material is generated. Since the fill material spreads over the entire chip and the side surface of the chip, there is a problem that it blocks the light input / output section.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a board mounting structure in which an underfill material non-filled region is surely formed in a portion where the underfill material is not desired to be filled.

[0010]

The board mounting structure of the present invention is a board mounting structure in which a chip is mounted on a mounting board by flip-chip and an underfill material is filled between the two. A groove structure for preventing the underfill material from entering is formed in at least one of the two or more of the above to have an underfill material non-filled region.

The underfill material includes any material that is filled between the mounting substrate and the chip and has fluidity. In particular, an adhesive is preferably used.

When the groove structure is formed on the chip side, it is preferable that the groove structure reaches the edge of the chip. In this case, the underfill material can be prevented from wrapping around from the outside of the groove structure. Therefore, intrusion of the underfill material can be prevented even more completely.

It is preferable that the groove structure is arranged so as to surround the area not filled with the underfill material. Also in this case, the underfill material can be more completely prevented from entering.

When the groove structure is formed on the mounting substrate side, it is preferable that the groove structure extends outside the mounting area of the chip. If the groove structure extends to the outside of the chip mounting region, the underfill material is less likely to wrap around the facing portion such as the optical interface, and the underfill material non-filled region can be formed more reliably.

When the groove structures are formed on both the substrate and the chip, it is preferable that both groove structures face each other. When the two groove structures are opposed to each other, the depth of the groove is equal to the depth of the both groove structures, and it is possible to better prevent the underfill material from flowing into the underfill material unfilled region.

The chip is preferably a semiconductor chip. An optical semiconductor chip is particularly preferable.

Further, the underfill material non-filled region is preferably an optical interface portion. In such a case, the input / output of light in the optical interface portion is performed without interruption. As a result, the input and output of light is surely performed.

[0018]

According to the present invention, in a structure in which a chip such as a semiconductor chip is flip-chip connected to a mounting board, a groove structure is formed in at least one of the mounting board and the chip, so that a gap between the chip and the mounting board is partially formed. Create a place where In such a widened portion, the effective surface tension of the liquid such as the underfill material entering due to the capillary phenomenon changes, so that the uniform diffusion and infiltration of the liquid such as the underfill material is hindered. In addition, when the underfill material diffuses due to the capillary phenomenon, when the groove structure is formed after the substrate interval is narrowed by the convex portion formed immediately before the groove structure, it is effective for the liquid such as the underfill material. The change in surface tension can be further increased. Therefore, the liquid such as the underfill material injected by the capillary phenomenon stops in the groove structure, and the underfill material unfilled region is formed. For example, the optical interface portion can be protected by setting the portion, such as the optical interface portion, desired to be protected from the underfill material to be the underfill material non-filling area. As the semiconductor chip to be flip-chip connected, an OEIC having an optical interface is taken as an example to show the configuration example, but if it is necessary to prevent the underfill material from entering a part between the chip to be flip-chip connected and the mounting substrate. The chip is not particularly limited to the OEIC.

Incidentally, FIG. 7 shows an image view after the underfill material is filled in this structure. It is possible to prevent the underfill material from spreading to the optical interface portion 2 arranged on the side surface of the OEIC chip 1 and blocking the optical interface portion. A state in which the underfill material is partially removed is shown in FIG. 7 (b).

[0020]

(Embodiment 1) As a first embodiment of the present invention, an example of the configuration will be shown taking an OEIC having an optical interface as a semiconductor chip for flip-chip connection. However, the OEIC is not particularly limited as long as it is necessary to prevent the underfill material from entering the part between the chip to be flip-chip connected and the mounting substrate.

As shown in FIG. 1, when the optical interface portion 2 is provided on the surface of the OEIC chip 1, the groove structure 3 is formed so as to surround the optical interface portion 2. After flip chip bonding this chip,
If the underfill material is filled from the opposite side of the optical interface portion 2 surrounded by the groove structure 3, the underfill material prevents diffusion and invasion in the groove structure, so that the optical interface portion 2 becomes an underfill material unfilled region. . Therefore, the optical interface portion 2 is not blocked by the underfill material.

FIG. 2 shows some examples of the planar shape of the groove structure, but any shape may be used as long as it can prevent the optical interface portion 2 from entering the underfill material. Further, the depth of the groove structure 3 and the cross-sectional shape of the groove structure may be any as long as they prevent the diffusion of the liquid due to the capillary phenomenon, and the depth and the cross-sectional shape are not particularly limited.

The planar shape of the groove structure is a concave shape (see FIG. 2).
(A), (d)), V shape (FIG. 2 (b), (e)), linear shape (FIG. 2 (c)) square shape (FIG. 2 (f)), etc. are illustrated. Of course, another shape such as a U shape may be used. The groove structure 3 shown in FIGS. 2A, 2B, and 2C is OEIC.
The edge of chip 1 has been reached. In this case, the underfill material can be prevented from wrapping around from the outside of the groove structure 3. Therefore, intrusion of the underfill material can be prevented even more completely.

Further, in FIG. 2 (f), the groove structure 3 is arranged so as to surround the optical interface portion 2, and in this case as well, the intrusion of the underfill material can be prevented more completely.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. The groove structure 3 is formed on the mounting substrate 5 side facing the optical interface portion 2 of the OEIC chip 1 to be flip-chip mounted. Here, the groove structure 3 is formed not only on the facing surface of the OEIC chip 1 to be flip-chip mounted but also on the O
Opposing surface of EIC chip 1 (flip chip mounting area 8)
It may be formed wider outward. The planar structure of the groove structure 3 of this example is a quadrangle. However, it goes without saying that the planar shape and the cross-sectional shape of the groove structure 3 may be any shape as long as it can prevent the optical interface portion 2 from entering the underfill material, as in the first embodiment.

(Embodiment 3) A third embodiment of the present invention is shown in FIG. The case where the groove structure 3 is formed on both sides of the OEIC chip 1 side for flip-chip mounting and the mounting substrate 5 side facing it is shown. In this case, it is desirable that the two groove structures 3 are located at the same position when they are opposed to each other, but they may not be particularly aligned. In this example, the groove structure on the OEIC chip 1 side has a V shape reaching the edge of the OEIC chip 1, and the optical interface facing portion 6 on the mounting substrate 5 side.
Also, a V-shaped groove structure 3 is provided. Needless to say, the planar shape and the cross-sectional shape of the groove structure 3 may be any shape as long as it is a shape that prevents the underfill material from entering the optical interface portion, as in the first embodiment.

(Embodiment 4) A fourth embodiment of the present invention is shown in FIG. Particularly, the case where the OEIC chip 1 having the optical interface 2 on its side surface is mounted is shown.

An optical device 12 is formed on the OEIC chip 1. An optical waveguide 11 is provided following the optical device 12 so as to input / output an optical signal to / from the optical device 12, and has an optical interface portion 2 on a side surface of the OEIC chip 1.

On the other hand, a V-shaped groove 10 for fiber storage is formed in the mounting substrate 5, and the optical fiber 9 is stored in the V-shaped groove 10 for fiber storage. Here, an example is shown in which the optical fiber 9 is mounted outside the flip chip mounting region 8 on the mounting substrate 5 in order to directly align the optical axis of the optical fiber 9. Of course, the structure outside the flip chip mounting area 8 is not limited. Further, although FIG. 5 shows a structure in which the groove structure 3 for preventing the infiltration of the underfill material is formed in the mounting substrate 5, the groove structure 3 is the chip 1 side or the mounting substrate 5 as in the first to third embodiments. It suffices if at least one side exists. Furthermore, the groove shape and the groove cross-sectional shape are not particularly limited. The flip-chip mounted OEIC may have any structure as long as the optical interface portion 2 exists on the side surface of the chip 1 as illustrated in FIG.

(Embodiment 5) FIG. 8A shows another embodiment of the present invention.

In this example, the V-shaped groove structure 3 is formed on the mounting substrate 5 side. In addition, a V-shaped convex portion 30 is formed outside the groove structure facing portion on the side opposite to the side where it is desired to prevent the underfill material from mixing in the groove structure facing portion on the chip 1 side. FIG. 8 (b) is an image diagram showing the position of each structure when the substrate and the chip 1 are stacked, and FIG. 8 (c) is a sectional view taken along the line aa '. Here, the V-shape is used as the shape of the groove structure 3 and the convex portion 30, but any shape may be used as long as it can prevent the underfill material from entering, as in the first embodiment. Needless to say. Further, in this example, the convex portion is formed on the side where the groove structure is not formed, but it may be formed on the same side as the groove structure as shown in FIG.

[0032]

As described above, according to the present invention, in the mounting method using the flip chip bonding technique, when filling an adhesive agent such as an underfill material in order to increase the mechanical strength of the connection, It is possible to realize a structure in which the underfill material is prevented from entering only in a region where it is difficult for the filler material to enter. This is extremely effective mainly when the chip to be flip-chip mounted has an optical interface such as OEIC.

[Brief description of drawings]

FIG. 1 is a diagram showing an example in which a groove structure is formed on a semiconductor chip.

FIG. 2 is a diagram illustrating the shapes of various groove structures.

FIG. 3 is an image diagram of flip-chip bonding showing an example in which a groove structure is formed on the mounting substrate side.

FIG. 4 is an image diagram of flip chip bonding showing an example in which a groove structure is formed on both a semiconductor chip and a mounting substrate.

FIG. 5 is an image diagram of flip chip bonding showing an embodiment in which an optical interface portion is present on a side surface of a semiconductor chip.

FIG. 6 is a view showing a groove structure in which an optical interface portion is present on a side surface of a semiconductor chip.

FIG. 7 is a view after filling an underfill material with respect to an example in which an optical interface portion is present on a side surface of a semiconductor chip.

FIG. 8 is a diagram showing a mounting structure according to a fifth embodiment.

FIG. 9 is a perspective view showing a mounting structure according to a modified example of the fifth embodiment.

FIG. 10 shows an example of an optical wiring structure manufactured on a semiconductor chip.

FIG. 11 is a view showing a state of filling an underfill material and a state after the filling in a flip chip bonding structure.

[Explanation of symbols]

1 OEIC chip, 2 Optical interface part (protection part), 3 groove structure, 4 bumps, 5 mounting board, 6 optical interface part, 7 bump connection pads, 8 flip chip mounting area, 10 V-shaped groove for fiber storage, 11 optical waveguide, 12 optical devices, 20 underfill material, 21 Underfill material 22 Underfill material unfilled area, 23 underfill material filling area, 30 convex

Continued front page    (72) Inventor Masami Tokumitsu             2-3-1, Otemachi, Chiyoda-ku, Tokyo Japan             Telegraph and Telephone Corporation F-term (reference) 5F044 KK02 LL01 RR18                 5F088 AA20 BA16 BB01 DA20 EA20                       JA03 JA14

Claims (10)

[Claims] 1. In a substrate mounting structure in which a chip is flip-chip mounted on a mounting substrate and an underfill material is filled between the both, an underfill is formed on at least one of the mounting substrate and the chip. A substrate mounting structure characterized in that a groove structure for preventing material intrusion is formed and has an underfill material unfilled region. 2. The board mounting structure according to claim 1, wherein the underfill material is an adhesive. 3. The substrate mounting structure according to claim 1, wherein when the groove structure is formed on the chip side, the groove structure reaches an edge of the chip. 4. The board mounting structure according to claim 1, wherein the groove structure is arranged so as to surround the underfill material non-filled region. 5. The substrate mounting according to claim 1, wherein when the groove structure is formed on the mounting substrate side, the groove structure extends to the outside of the mounting area of the chip. Construction. 6. The substrate mounting structure according to claim 1, wherein when the groove structure is formed on both the substrate and the chip, the groove structures are opposed to each other. . 7. When the groove structure is formed on at least one of the chip side and the mounting substrate side, the periphery of the groove structure or the outside of the groove structure facing portion on the side where the groove structure is not formed. The board mounting structure according to claim 1, wherein a convex portion is provided on the substrate. 8. The substrate mounting structure according to claim 1, wherein the chip is a semiconductor chip. 9. The substrate mounting structure according to claim 1, wherein the underfill non-filled region is an optical interface portion. 10. A semiconductor device having the substrate mounting structure according to claim 1. Description: