JPH0562977A - Bump electrode of integrated circuit device - Google Patents

Abstract

PURPOSE:To enable the bump electrodes of an integrated circuit device bonded and connected to a mounting object through the intermediary of conductive resin at mounting to be lessened in arrangement pitch in a chip. CONSTITUTION:A bump electrode 21 is composed of a pillar-shaped main body 21 whose circumferential face stands vertically from the surface of a chip 10 and a cap-shaped top 22 which protrudes laterally from the circumferential face of the main body 21, where the height (h) of the top 22 is set as large as 5-25% of the overall height H of the electrode 21, and the circumferential edge 22a of the top 22 is made to face obliquely to form a protrudent curved surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to bump electrodes used in so-called flip chips of integrated circuits, which are bonded and connected to a counterpart through a conductive resin during mounting.

[0002]

2. Description of the Related Art As is well known, an integrated circuit device configured as a flip chip having bump electrodes is directly mounted on a wiring board or the like in a chip state, and is mounted in a package once and then mounted. Compared with this, it is possible to reduce the cost of various products by saving extra labor, and moreover, it is possible to reduce the space required for mounting and to downsize the device. Therefore, it is mainly used for electronic devices such as display devices and printing devices. Has been widely adopted as an integrated circuit device suitable for mass-production devices, especially when there are many external connection points per chip.

When mounting this flip chip,
Conventionally, the bump electrodes made of gold, copper, solder, etc. are often joined to the wiring conductor such as the wiring board, which is the mounting partner, by thermocompression bonding or soldering.
Since a high temperature of ° C and a pressure of several tens of g are required for each bump electrode, there is a limit to the improvement of the mounting speed during mass production, and the risk that the bump electrode or the chip is damaged during bonding cannot be completely eliminated. Therefore, when the current capacity of the flip chip is not so large, the mounting method of bonding and connecting the bump electrode to the other party by the conductive resin becomes advantageous. The present invention relates to a flip chip bump electrode suitable for mounting using such a conductive resin, and a conventional technique thereof will be described below with reference to FIG.

FIG. 3 (a) shows the procedure for providing the bump electrodes 20 on the chip 10, and FIG. 3 (b) shows the procedure for mounting the chip 10 on the wiring board 30. FIG. 3A is an enlarged cross-sectional view of a very small part of the chip 10 in which the integrated circuit is formed in the semiconductor region 1. An aluminum metal film 3 connected to an integrated circuit is provided on an insulating film 2 that covers the surface of the semiconductor region 1. The bump electrode 20 is a metal exposed in a window opened in a protective film 4 that covers the bump electrode 20. It is provided to connect to the membrane 3. Bump electrode
As a base for growing a metal for the 20 by electrolytic plating, a lower base film 5 made of titanium or the like and an upper base film 6 made of copper or the like connected to the metal film 3 in the window are formed with a very thin film thickness. Then, the upper base film 5 is patterned by photoetching so that the upper base film 5 has substantially the same size as the window of the protective film 4.

Next, a mask film M made of photoresist is spin-coated as a mask film M for electrolytic plating, and a window is opened by a photo process so that only the upper base film 6 is exposed. The metal for the bump electrode 20 is usually grown on the upper base film 6 by the electrolytic plating method using the lower base film 5 as a plating electrode film. Therefore, the metal for that purpose is grown higher as shown in the figure after filling the inside of the window of the mask film M. At this time, the upper portion of the mask film M is considerably projected laterally as shown in the figure and electrolysis is performed. Since it is plated, the bump electrode 20 is formed in a mushroom shape having a short neck 23 and a large cap 24.

In the mounting state shown in FIG. 3 (b), the flip chip 10 is mounted on the wiring board 30 or the like by a so-called face-down method with the surface on which the bump electrode 20 is projected facing downward. When the conductive resin 40 is used, it is often mounted by a so-called COG (Chip On Glass) method.
At this time, the wiring board 30 is formed by arranging a large number of wiring conductors 32 made of a very thin conductive film of 0.5 μm or less such as ITO (indium tin oxide) on a transparent insulating substrate 31 such as glass. As the conductive resin 40, for example, an Ag-Pd resin paste containing fine powder of silver and palladium is used.

In the mounting work, the chip 10 in which the conductive resin 40 is preliminarily attached to the cap 24 at the tip of the bump electrode 20 by a predetermined minute amount is placed on the wiring board 30 which is usually heated to a temperature of about 100.degree. After the positioning and mounting, the conductive resin 40 is cured while being pressed with a slight pressure of 1 g or less per bump electrode 20, whereby the bump electrode 20 is bonded to the wiring conductor 32 and at the same time the connection is achieved. During this mounting, the conductive resin 40 between the shade 24 and the wiring conductor 32 is pushed out to the side and spreads out a little, but as shown in the figure, it can be hardened in a state where it does not protrude much from the range of the shade 24. it can. As a result, the mounting work can be normally completed within a short time of 10 to 20 seconds, and even if there are considerable variations in the height of many bump electrodes 20, they are absorbed by the conductive resin 40 to ensure a reliable connection state. Is guaranteed.

[0008]

As described above, the flip-chip mounting using the conductive resin has many advantages, but the flat mushroom-shaped bump electrode 20 as shown in FIG. 3 is, so to speak, so to speak. The width of the cap 24 is 2 to 3 with respect to the neck 23 which is the main body.
Since the array pitch P of the bump electrodes 20 in FIG. 2 (b) cannot be reduced to a certain limit or less, usually about 100 μm or less, the integrated circuit device is highly integrated as in recent years. As the chip size becomes smaller, it becomes very difficult to reasonably arrange the bump electrodes 20 within the limited chip area in the flip chip 10 having 100 or more external connection points. There's a problem. This state is shown in FIG.

When the size of the bump electrodes 20 is small as shown in FIG. 4A, it is well known that the bump electrodes 20 are arranged at a narrow pitch P on the peripheral portion of the chip 10 in order to effectively use the chip area. However, the diameter of the bump electrode 20 is, for example, 2
Since it is necessary to increase the pitch P by about 1.5 times when the number of times is doubled, it is necessary to increase the chip size or arrange the bump electrodes 20 inside the chip 10 as shown in FIG. 4 (b). In the former case, the degree of integration is reduced to about half, and in the latter case, the area around the bump electrodes 20 arranged inside tends to be a wasted space, so a considerable decrease in the degree of integration is unavoidable, and the number of internal arrangements is particularly large. And the integration level drops to less than half.

To solve this problem, the bump electrode 20 can be formed in the shape shown in FIG. This is to grow only the neck 23 of the bump electrode 20 in FIG. 3 to a desired height. For this purpose, as shown in FIG. 5 (a), the mask film M has a thickness of several tens of μm. If a metal for bump electrode 20 is grown as a columnar main body 25 within the window by electrolytic plating within the window, the cap 24 as shown in FIG. It is possible to reduce the size of the bump electrode 20 to less than half that in the case of FIG. 3 without protruding laterally from the neck 23.

However, as shown in FIG. 5B, the flip chip 10 having the columnar bump electrodes 20 is mounted on the wiring board.
When it is mounted on 30, the heated conductive resin 40 flows along the surface of the insulating substrate 31 while the conductive resin 40 is still highly fluid before being cured, so that a short circuit S occurs between the connection points as shown in the figure. It has been found that the arrangement pitch P of the bump electrodes 20 needs to be about the same as in the case of FIG. 3 in order to completely prevent this.

As described above, it is very difficult to reduce the arrangement pitch of the conventional bump electrodes of the flip chip mounted by using the conductive resin to about several tens of μm, and the integrated circuit device. The current situation is that it is a bottleneck for higher integration. The present invention is based on such circumstances
It is an object of the present invention to provide a bump electrode capable of reducing the array pitch on the flip chip as compared with the conventional one.

[0013]

According to the present invention, the object is to provide a columnar main body having a peripheral surface that rises substantially vertically from the surface of the flip chip, and a flat hat-shaped tip protruding laterally from the outer periphery thereof. It is formed in a mushroom shape with a part,
The total height of the bump electrode with the tip and the body is 5
This is achieved by a bump electrode which is formed to have a height of -25% and whose peripheral edge is formed in a curved surface which is convex in the oblique direction.

It should be noted that the height of the above-mentioned tip portion is 10 of the total height.
~ 20% is more desirable, the height of the body is 10 ~
For small bump electrodes of 40 μm, the height of the tip is 2 to 10 μm.
m, more preferably 5 to 10 μm. Further, when mounting the flip chip having the bump electrode of the present invention on the other side, the bump electrode side is attached with a conductive resin as in the conventional case and then placed on the other side kept at a predetermined curing temperature. To accurately control the amount of conductive resin adhered to the bump electrodes at this time, the surface of the tip of the bump electrode should be attached to the surface of the jig where the conductive resin is applied to a specified thickness. It is advantageous to attach the conductive resin to the bump electrodes by bringing them into contact with each other. The pressure to press the flip chip against the other party while curing the conductive resin is
The amount per bump electrode is preferably 1 g or less, more preferably 0.5 g or less.

[0015]

According to the experimental results of the inventor of the present application, although the bump 24 has the disadvantage that the bump electrode 20 spreads laterally in the shade 24 of FIG. 3, the conductive resin 40 flows along the surface of the mounting partner as shown in FIG. This has the advantage of preventing the above, and the extent to which this shade 24 extends laterally from the neck 23 in FIG. 3 is approximately proportional to its height. Therefore, in the present invention, contrary to the conventional case, the height of the columnar main body portion corresponding to the neck 23 of the bump electrode is increased, and the height of the flat hat-shaped tip portion corresponding to the shade 24 is formed to be small, and The arrangement pitch of the bump electrodes is shortened as compared with the conventional one by preventing the conductive resin from flowing in the lateral direction while suppressing the spread of the bumps. For this reason, in the present invention, the tip portion of the bump electrode is formed to have a height of 5 to 25% of the total height as described in the above-mentioned configuration, and the lateral extension of the tip portion from the main body portion is suppressed to the same extent. ..

Further, according to the present invention, by utilizing the characteristic of electrolytic plating when growing a metal for a bump electrode, the peripheral edge of the tip end portion is formed in a convex curved surface in an oblique direction, so that the tip end at the time of mounting. Excessive conductive resin extruded from between the part and the other side is held on this curved surface or the protruding part of the subsequent tip part from the main body part, so that the conductive resin before curing can flow out more securely. It is intended to prevent and strengthen the adhesive strength of the conductive resin after curing.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a method of mounting a bump electrode according to the present invention and a flip chip of an integrated circuit device having the bump electrode, and FIG. 2 shows a method of manufacturing the bump electrode. Note that the same reference numerals are given to the same portions as those in FIG. 3 and subsequent figures described above in these figures, and thus the description of the overlapping portions will be appropriately omitted.

FIG. 1A is an enlarged sectional view of a part of the chip 10 showing the bump electrode 20 of the present invention. This bump electrode 20
In the present invention, as in the prior art, the lower base film 5 which is in conductive contact with the metal film 3 in the window opened in the protective film 4 is used as a plating electrode film on the upper base film 6 and a predetermined metal such as gold or copper is used. It is formed by growing a metal into a mushroom shape by electrolytic plating.
The shape of the mushroom is different from that of the conventional bump electrode shown in FIG. 3 (a), and the height of the main body portion 21 that hits the neck is large, and the height of the tip portion 22 that hits the shade is conversely small. Main body as shown
Reference numeral 21 is a columnar shape having a peripheral surface that rises substantially vertically from the chip surface, and tip portion 22 is in the shape of a flat hat extending laterally from the outer periphery thereof.

In the bump electrode 20 of the present invention, the tip 22
The height h is about 5 to 25% of the total height H, preferably 10
.About.20%, and the peripheral edge 22a of the tip portion 22 is formed into a curved surface which is convex in the oblique direction as shown in the figure. In addition, this peripheral edge 22
The extent to which a extends from the peripheral surface of the main body portion 21 is substantially the same as the height h of the tip portion 22, and the center portion 22b thereof has a slightly concave surface as shown in the figure.

The flip chip 10 having the bump electrodes 20 is mounted on the other wiring board 30 as shown in FIG. 1 (c).
A procedure for preliminarily attaching the conductive resin 40 to the tip surface of 20 is shown. To this end, the conductive resin 40 is applied on the flat surface of the jig 50 shown in the lower part of the figure by a spin coating method or a screen printing method to a predetermined thickness of about several μm, and the chip 10 is placed.
By bringing the tip of the bump electrode 20 into contact with the jig 50 with the tip facing downward, it is preferable that a predetermined minute amount of the conductive resin 40 be attached to the surface of the tip portion 22 as shown in the figure.

In the mounting step shown in FIG. 3 (c), the opponent wiring board 30 is maintained at a temperature of, for example, about 100.degree. C., and the chip 10 is accurately positioned and placed thereon and lightly pressed. By curing the conductive resin 40, the tip end portion 22 of the bump electrode 20 may be bonded and connected to the wiring conductor 32 of the wiring board 30 as shown in the drawing, and this mounting work is usually performed in a short time of 10 to 20 seconds. Complete with. The pressing pressure during this mounting is 1 g or less per bump electrode 20, preferably 0.1
It is suitable to set the weight to about 0.5 g. For example, it is preferable to cure the conductive resin 40 in a state where the weight of the number of grams corresponding to the number of bump electrodes is placed on the back surface of the chip 10.

Even under such a slight pressure, the conductive resin 40 having fluidity before curing is slightly extruded laterally from between the tip portion 22 of the bump electrode 20 and the wiring conductor 32.
Since the peripheral edge 22a of 22 is formed into a curved surface as described above, it escapes into the wedge-shaped gap between it and the wiring conductor 32 and is held there, and hardens after a short time. As described above, in the bump electrode 20 of the present invention, unless the amount of the conductive resin 40 deposited in the step of FIG.
Remains near the outer periphery of the tip 22 of the bump electrode 20 until it hardens, and there is almost no risk of a short circuit S occurring by flowing along the surface of the insulating substrate 31 of the wiring substrate 30 as shown in FIG. 5 (b). Become. Note that the width of the wiring conductor 32 is several to 10 μm from the tip 22.
If the conductive resin 40 is formed so as to be wider, the portion that cannot be held in the above-mentioned wedge-shaped gap even if the amount of the conductive resin 40 adheres excessively escapes from the main body portion 21 to the portion where the tip 22 overhangs to prevent a short circuit. It can be prevented more reliably.

In the bump electrode 20 of FIG. 1, it is preferable that the height of the main body portion 21 is in the range of 10 to 40 μm and the height h of the tip portion 22 is in the range of 2 to 10 μm. Since the bump electrodes 20 can be prevented as described above, the bump electrodes 20 can be arranged on the chip 10 at a pitch which is about twice the diameter or size of the main body portion 21 or slightly narrower. Therefore, according to the present invention, the bump electrodes 20 having an effective diameter of 50 μm can be arranged at a pitch of 100 μm or less.

Next, a method of manufacturing the bump electrode of FIG. 1 will be briefly described with reference to FIG. FIG. 2A shows a state in which a window is opened in the protective film 4 for providing a bump electrode connected to the metal film 3 provided on the insulating film 2 covering the semiconductor region 1. Same figure
(b) is a step of forming a base film for bump electrodes. It is necessary to connect the lower base film 5 such as titanium or chrome to the metal film 3.
Sputtering is performed to a film thickness of about 2 μm, and an upper base film 6 such as copper or palladium is sputtered thereon to a film thickness of about 0.5 μm.
Pattern to a size of 50 μm.

FIG. 2 (c) shows a preparation process for electrolytic plating.
A photoresist is spin-coated to a thickness of 10 to 40 μm, and a window exposing only the upper base film 6 is opened by a photo process to form a mask film M. In the electroplating process of FIG. 3D, as is customary, the lower underlayer film 5 is used as a plating electrode to grow a metal such as gold or copper on the upper underlayer film 6 by electrolytic plating to form the bump electrode 20. At this time, the portion of the mask film M grown in the window becomes the main body portion 21, and the portion grown outside the window to a height h of, for example, 2 to 10 μm and protruding outward therefrom is the tip portion. 22.

After the step shown in FIG. 2D, the mask film M is first removed as usual, and then the lower base film 6 is removed by chemical etching using the bump electrodes 20 and the upper base film 6 as a mask. As a result, the interconnections for electrolytic plating of the bump electrodes 20 are removed, and the bump electrodes 20 shown in FIG. 1A are completed. It should be noted that the growth height of the bump electrode 20 due to electrolytic plating may vary by about several percent within the surface of the chip 10, but is absorbed by the conductive resin 40 in the mounted state of FIG. 1 (c).

[0027]

As described above, according to the present invention, the pillar-shaped main body portion having the peripheral surface in which the bump electrodes for the integrated circuit device to be mounted on the other side through the conductive resin stand upright almost vertically from the chip surface. And a mushroom-like shape with a flat-hatched tip protruding laterally from the outer periphery of the tip, and the tip has a height of 5 to 25% of the total height of the bump electrode combined with the main body. The following effects can be obtained by forming the peripheral edge of the portion in a slanting direction to form a convex curved surface.

(A) The bump electrode main body is formed to have a large height and the tip portion is formed to have a small height to minimize the lateral spread of the bump electrode by the tip portion, and at the time of mounting. By preventing the lateral flow of the conductive resin by the tip portion, the arrangement pitch on the chip surface can be reduced to half or less as compared with the conventional mushroom-shaped bump electrode. As a result, a larger number of bump electrodes can be arranged on the peripheral portion of the chip than ever before, and the integration degree of the integrated circuit device can be improved. (b) The peripheral edge of the tip of the bump electrode is formed in a convex curved surface in an oblique direction, and the conductive resin extruded from between the tip and the other side during mounting is wedge-shaped gap between the curved side and the other side. By holding at, to prevent the conductive resin rich in fluidity before curing from flowing out from the connection point along the surface of the other side, and almost eliminating the possibility of short circuit between the connection points,
In addition, the adhesive strength of the conductive resin after curing can be increased to improve the reliability of connection. (c) Since shortening the curing time of the conductive resin is advantageous for preventing the conductive resin from flowing out in the lateral direction, it is essentially suitable for high-speed mounting.

As described above, according to the present invention, the arrangement pitch of the bump electrodes in the flip chip is reduced to pioneer a bottleneck in high integration of the integrated circuit device, reduce damage at the time of mounting, and improve the reliability of mounting. It is possible to obtain a remarkable effect of improving the mounting efficiency and mounting efficiency, and by implementing the present invention, it is possible to contribute to the improvement of the economical efficiency due to the miniaturization of the flip chip and the further expansion of its application.

[Brief description of drawings]

FIG. 1 shows an embodiment of a bump electrode according to the present invention.
(a) is an enlarged cross-sectional view of a portion of a chip of an integrated circuit device where bump electrodes are provided, and (b) is a side view of a chip and a conductive resin coating jig showing a preparatory process before mounting. Figure (b) is a side view of the chip and the mounting partner showing the mounting process.

FIG. 2 shows a method of manufacturing the bump electrode of FIG. 1, and FIG.
6D to 6D are enlarged cross-sectional views of a main part of the chip showing it in each of the main steps.

FIG. 3 shows a bump electrode according to a conventional technique, FIG. 3A is an enlarged cross-sectional view of a portion of a chip of an integrated circuit device in which a bump electrode is provided, and FIG. 3B is a chip showing a mounting state and a mounting partner. It is a side view.

4A and 4B show an arrangement state of bump electrodes on a chip surface. FIG. 4A is a top view of the chip when the bump electrodes are arranged only on a peripheral portion of the chip, and FIG. FIG. 6 is a top view of the chip when the chips are arranged also in the central part of FIG.

FIG. 5 is a view showing bump electrodes according to different conventional techniques.
(a) is an enlarged cross-sectional view of a portion of a chip of an integrated circuit device on which bump electrodes are provided, and (b) is a side view of a chip and a mounting partner showing a mounted state.

[Explanation of symbols]

 10 Chip of integrated circuit device 20 Bump electrode 21 Body part of bump electrode 22 Tip part of bump electrode 22a Edge of tip part 30 Mounting partner or wiring board 32 Wiring conductor to which bump electrode is connected 40 Conductive resin H Whole bump electrode Height h Height of tip of bump electrode P Pitch array pitch of bump electrode

Claims (3)

[Claims] 1. A bump electrode projecting from a chip for an integrated circuit, which is adhered and connected to a counterpart through a conductive resin at the time of mounting, and has a columnar shape having a peripheral surface which rises substantially vertically from the chip surface. Formed in a mushroom shape with a body and a flat-hatched tip that laterally overhangs from the outer periphery,
The total height of the bump electrode with the tip and the body is 5
A bump electrode for an integrated circuit device, which has a height of -25% and whose peripheral edge is formed in a convex curved surface in an oblique direction. 2. The bump electrode for an integrated circuit device according to claim 1, wherein the tip portion of the bump electrode is formed to have a height of 10 to 20% of the total height. electrode. 3. The bump electrode according to claim 1, wherein the height of the body of the bump electrode is 10 to 40 μm and the height of the tip is 2 to 10 μm. Bump electrode.