JPH0786287A - Method for forming bump - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a bump forming method used for joining a semiconductor element and a mounting substrate, and an object thereof is to form a bump with high productivity and high accuracy. [Structure] A photoresist material 11 is applied to a substrate 10, and the photoresist material 11 is exposed by using a mask 12 having a predetermined pattern corresponding to the formation position of the electrode portion 4 and a position corresponding to the formation position of the electrode portion 4. Adhesive part 11 with adhesiveness only
a is formed, and the fine conductive particles 13 to be the bumps 2 are attached onto the adhesive portion 11a, and the substrate 10 having the fine conductive particles 13 attached is brought into contact with the semiconductor element 1 to form the fine conductive particles 13
Is fixed to the electrode portion 4 formed on the semiconductor element 1,
Then, the substrate 10 is separated from the semiconductor element 1 while maintaining the state where the fine conductive particles 13 are fixed to the semiconductor element 1, and the bumps 2 are formed on the electrode portions 4 of the semiconductor element 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming bumps used for joining a semiconductor element and a mounting board.

In recent years, as the speed and density of semiconductor elements have increased, chip-on-board (COB) has been advanced,
There is a tendency for face down bonding of semiconductor elements by solder bumps or the like to form multi-chips, especially CCB.
(Controlled Collapse Bonding) method is expected to achieve high integration.

In order to cope with this COB process and to realize the CCB method, it is necessary to form bumps on a semiconductor element with high accuracy and high productivity.

Therefore, there is a demand for a bump forming method which is excellent in accuracy and productivity.

[0005]

2. Description of the Related Art FIGS. 3A and 3B show a semiconductor device 1 having bumps 2. FIG. 3A shows the semiconductor device 1.
3B is a bottom view of the semiconductor element 1. FIG. As shown in each drawing, the semiconductor element 1 has a structure in which a plurality of bumps 2 are formed on the bottom surface of the main body 3. The bumps 2 are formed of, for example, solder or gold (Au).

FIG. 2 shows a conventional method for forming the bump 2. Hereinafter, a conventional method for forming the bump 2 will be described with reference to FIG. FIG. 2A shows the semiconductor element 1 before the bump 2 is formed. In this state, a plurality of electrode portions 4 are formed at predetermined positions on the bottom surface 3a of the body portion 3.

In order to form the bump 2, first, as shown in FIG.
As shown in FIG. 3, the plating electrode 5 made of a conductive material is formed on the entire bottom surface 3a by the vacuum deposition method or the sputtering method. Subsequently, as shown in FIG. 2C, a photoresist material 6 is applied over the entire upper surface of the plated electrode 5.

When the photoresist material 6 is applied, an opening 8 is formed at a position facing the electrode portion 4 of the photoresist material 6 by using the photolithography method. Specifically, as shown in FIG. 2D, the photoresist material 6 is exposed using a mask 7 having a pattern opening 7a at a position corresponding to the position where the electrode portion 4 is formed, followed by development, By performing post-baking, the photoresist material 6 in the exposed portion is removed.
FIG. 2E shows a state where the photoresist material 6 in the exposed portion is removed, and in this state, the plating electrode 5 is exposed at the formation position of the electrode portion 4.

Subsequently, the main body 3 having the opening 8 formed therein is dipped in a plating solution to perform plating to form the bump 2 at the position where the opening 8 is formed as shown in FIG. 2 (F). . Subsequently, as shown in FIG. 2G, the photoresist material 6 is removed, and the plating electrode 5 is patterned, so that the pump 9 shown in FIG.
The semiconductor element 1 having is formed.

[0010]

However, in the above-described conventional bump forming method, the coating of the photoresist material 6
A number of steps such as exposure, development, post-baking, and removal are required, the manufacturing process is complicated, the efficiency of forming the pump 9 is poor, the productivity of the semiconductor element 1 is reduced, and the manufacturing cost is increased. It was

Further, since the bumps 2 are formed by the plating method, it takes a long time to form the bumps 2, which also causes a problem that the production efficiency of the semiconductor element 1 is lowered.

Further, when the bumps 2 are manufactured by the plating method, the height of the bumps 2 is varied and the accuracy of forming the bumps 2 is lowered. As a result, there is a problem in that the mountability when mounting the semiconductor element 1 on the mounting board is reduced.

The present invention has been made in view of the above points, and an object thereof is to provide a bump forming method capable of forming a bump with high productivity and high precision.

[0014]

In order to solve the above problems, according to the present invention, in a bump forming method for forming bumps on electrode portions formed on a semiconductor element, a step of applying a photosensitive material to a substrate, The exposed photosensitive material is exposed to light using a mask having a predetermined pattern corresponding to the formation position of the electrode portion, and adhesiveness is selectively imparted only to the position corresponding to the formation position of the electrode portion. And a step of adhering fine conductive particles to be bumps on the photosensitive material selectively provided with adhesiveness, abutting the substrate on which the fine conductive particles are attached to a semiconductor element, Fixing the fine conductive particles to an electrode part formed on the semiconductor element, and separating the substrate from the semiconductor element while maintaining the state where the fine conductive particles are fixed to the semiconductor element. ,Previous It is characterized in that provided a step of forming bumps on electrodes of the semiconductor element.

Further, when adhering the fine conductive particles to be the bumps on the photosensitive material, first, the fine conductive particles are sprayed on the entire surface of the selectively adhesively provided photosensitive material to improve the adhesiveness. By attaching the fine conductive particles on the photosensitive material having the adhesive, and then removing the fine conductive particles existing on the photosensitive material having no adhesive property, the fine conductive particles are adhered only on the photosensitive material having the adhesive property. A method of attaching fine conductive particles may be used.

When the substrate to which the fine conductive particles are attached is brought into contact with the semiconductor element, a conductive resin or active metal film may be formed in advance on the electrode portion.

Further, copper (Cu) or gold (Au) particles may be used as the fine conductive particles.

[0018]

[Operation] By forming bumps by the above method,
Adhesiveness is provided only at a predetermined position (a position corresponding to the electrode part) of the photosensitive material, and fine conductive particles are attached to the part having the adhesiveness and fixed to the electrode pad of the semiconductor element. By transferring the substrate to the semiconductor element and forming the bumps, it is not necessary to develop and remove the photosensitive material from the substrate, and the bump forming process can be simplified.

Further, since the fine conductive particles to be the bumps are formed in advance, the bump deposition time at the time of forming bumps, which is required in the conventional plating method, is unnecessary, and the bumps can be formed in a short time. Therefore, the production efficiency of semiconductor elements can be improved.

Further, a technique for producing fine particles has been established, and the fine conductive particles can be accurately formed into a predetermined diameter dimension. Therefore, the diameter of the fine conductive particles is made uniform, and the height of the bump is made uniform while being fixed to the semiconductor element. Therefore, the mountability when mounting the semiconductor element on the mounting substrate can be improved.

[0021]

Embodiments of the method of the present invention will now be described with reference to the drawings. FIG. 1 shows a method of forming a bump 2 according to an embodiment of the present invention in accordance with a forming procedure. In the following description, the same components as those described in FIG. 3 will be designated by the same reference numerals.

To form the bumps 2, first, a substrate 10 having an area substantially equal to or larger than the size of the semiconductor device 1 is prepared. The substrate 10 is made of, for example, ceramic or glass, and its surface 10a is a smooth surface.

The upper surface 10a of the substrate 10 is shown in FIG.
A photoresist material 11 is applied as shown in FIG.
The photoresist material 11 has a photo-softening property and is generally used in the manufacturing process of semiconductor devices. Further, the photoresist material 11 generally has some adhesiveness in a softened state, and can function as an adhesive as described later.

When the photoresist material 11 is applied onto the substrate 10, the photoresist material 11 is exposed using the mask 12. The mask 12 has a pattern opening 12a at a position corresponding to the position where the electrode portion 4 of the semiconductor element 1 is formed.
Is formed, and the light is exposed only to the position facing the pattern opening 12a of the photoresist material 11. On this occasion,
Since the upper surface 10a of the substrate 10 is a smooth surface, the upper surface of the photoresist material 11 is also a smooth surface, which enables highly accurate exposure processing.

The size of the pattern opening 12a is
It is set to be smaller than the pattern opening 7a formed in the mask 7 used in the conventional technique described with reference to FIG. 2, and specifically, about 1 of the diameter dimension of the bump 2 to be formed and used.
The size is / 2.

When the exposure process is performed as described above, the post-baking process is subsequently performed. As described above, since the photoresist material 11 has a photo-softening property, the portion which is not exposed by the post-baking treatment (the portion indicated by the reference numeral 11b in FIG. 1C.
The non-bonded part) is cured. On the other hand, the exposed portion (the portion indicated by reference numeral 11a in FIG. 1C.
The adhesive portion) is not cured even by the post-baking treatment, and maintains the adhesive state. In addition, the exposed portion is the semiconductor element 1
Since it corresponds to the formation position of the electrode portion 4, the formation position of the adhesive portion 11a also corresponds to the formation position of the electrode portion 4.

When the adhesive portion 11a and the non-adhesive portion 11b are formed on the photoresist material 11 as described above, the fine conductive particles 13 made of copper (Cu) or gold (Au) are subsequently formed.
Are sprayed on the entire upper surface of the photoresist material 11. The fine conductive particles 13 will be the bumps 2 later, and are small-diameter spherical particles manufactured in a separate process in advance. Techniques for forming such small-diameter spherical particles have been established, and it is possible to accurately form spherical particles having a predetermined diameter. Therefore, the fine conductive particles 13 are processed with high precision to the predetermined diameter size of the bump 2.

As described above, the adhesive portion 11a and the non-adhesive portion 11b are formed on the photoresist material 11, and the fine conductive particles 13 are sprayed on the entire upper surface of the photoresist material 11, so that the upper portion of the adhesive portion 11a is covered. The fine conductive particles 13 located at are bonded to the bonding portion 11a,
The fine conductive particles 13 located above the non-adhesive portion 11b are simply placed on the non-adhesive portion 11b. This state is shown in FIG.

The fine conductive particles 1 are formed on the photoresist material 11.
When 3 is sprayed, the fine conductive particles 13 located above the non-bonded portion 11b are subsequently removed. Non-bonded part 1
As a method for removing the fine conductive particles 13 on 1b,
Micro conductive particles that are not adhered by blowing compressed air 1
A method of blowing away 3 or a method of removing it with a brush can be considered. As described above, even if the compressed air is blown or a brush is used, the fine conductive particles 13 located on the upper portion of the adhesive portion 11a are adhered to the adhesive portion 11a, so that they are not removed and the photoresist material 11 is not removed. Remain on top. FIG. 1 (E) shows the fine conductive particles 1 on the non-adhesive portion 11b.
3 shows a state in which 3 is removed.

Since the diameter of the pattern opening 12a of the mask 12 is about 1/2 of the diameter of the fine conductive particles 13 as described above, the diameter of the adhesive portion 11a is also small. It is about 1/2 of the diameter of the conductive particles 13. Therefore, the plurality of fine conductive particles 13 are not bonded to the bonding portion 11a, and the bonding position is positioned at a predetermined position (position where the electrode part 4 is formed) with high accuracy.

Since the formation position of the adhesive portion 11a corresponds to the formation position of the electrode portion 4 as described above, the fine conductive particles 13 adhered to the adhesive portion 11a also correspond to the formation position of the electrode portion 4 formed on the semiconductor element 1. It corresponds to the formation position.

When the fine conductive particles 13 are bonded to the bonding portion 11a as described above, the semiconductor element 1 on which the bumps 2 are to be formed and the substrate 10 are arranged to face each other. At this time, the electrode portions 4 formed on the semiconductor element 1 and the fine conductive particles 13 disposed on the substrate 10 are positioned and face each other. In addition, the electrode portion 4 formed on the semiconductor element 1
In advance, a conductive resin or an active metal film is formed in advance.

Then, by pressing the substrate 10 against the semiconductor element 1, the fine conductive particles 13 are pressed onto the electrode portion 4. A conductive resin or an active metal film having good bondability with copper (Cu) or gold (Au) is arranged in advance in the electrode part 4, and the bondability between the electrode part 4 and the fine conductive particles 13 is improved. It is designed to be strong. On the other hand, the adhesive force between the fine conductive particles 13 and the adhesive portion 11a is weak.
This is because the photoresist material 11 is originally not an adhesive agent and has a small adhesive force, and the minute conductive particles 13 are spherical and are in point contact with the adhesive portion 11a.

Therefore, as shown in FIG.
After pressing the semiconductor element 1 onto the semiconductor element 1, the substrate 10 is attached to the semiconductor element 1
Away from the adhesive portion 11a of the photoresist material 11
The fine conductive particles 13 adhered to the are bonded and fixed to the electrode portion 4. By performing the series of processes described above, the bump 2 can be formed on the semiconductor element 1 as shown in FIG. Thus, by simply transferring the fine conductive particles 13 from the substrate 10 to the semiconductor element 1, the bumps 2
Since the bumps 2 can be formed, the bumps 2 can be reliably formed in a short time.
Can be formed in the semiconductor element 1. Therefore, the semiconductor element 1 can be formed with high productivity, and the manufacturing cost of the semiconductor element 1 can be reduced.

Further, since the fine conductive particles 13 have a uniform particle size and are accurately formed to have a predetermined bump diameter, the height dimension of the semiconductor element 1 from the main body 3 varies. Rather, the mountability when mounting the semiconductor element 1 on the mounting substrate (not shown) can be improved. Further, the size of the bumps 2 can be reduced to the processing limit by the photolithography method or the formation limit diameter of the fine conductive particles 13, and it is possible to cope with high density and high integration of the semiconductor element 1.

Although the photoresist material 11 that reacts to light is used as the photosensitive material in the above-described embodiments, the photosensitive material is not limited to the one that reacts to light, and other radiation such as X-rays may be used. As a matter of course, a reaction type may be used.

In this embodiment, the photosensitive material is made to have adhesive properties at predetermined positions, so that the fine conductive particles 13 are attached to the substrate 1.
Although it is configured to be detachably held at a predetermined position of 0, for example, a recess may be formed at a predetermined position of the substrate, and fine conductive particles may enter the recess to be held on the substrate.

[0038]

As described above, according to the present invention, adhesiveness is provided only at a predetermined position (a position corresponding to the electrode portion) of the photosensitive material, and the fine conductive particles are attached to the portion provided with the adhesiveness. Then, by fixing this to the electrode pad of the semiconductor element and transferring it from the substrate to the semiconductor element to form a bump, development on the photosensitive material and removal from the substrate are not required, and the bump forming process can be simplified. Therefore, the manufacturing cost of the semiconductor element can be reduced.

Further, since the fine conductive particles to be the bumps are formed in advance, the bump deposition time at the time of bump formation, which was necessary in the conventional plating method, is unnecessary, and the bumps can be formed in a short time. As a result, the production efficiency of the semiconductor device can be improved, and the manufacturing cost of the semiconductor device can also be reduced by this.

Further, a technique for producing fine particles has been established, and since the fine conductive particles can be accurately formed to have a predetermined diameter, the diameter of the fine conductive particles can be made uniform and the semiconductor element can be manufactured. The bumps are made uniform in height in the state of being fixed to the substrate, and thus the mountability when mounting the semiconductor element on the mounting substrate can be improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a bump forming method according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a conventional bump forming method.

FIG. 3 is a diagram for explaining a structure of a semiconductor device having bumps formed thereon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor element 2 Bump 3 Body part 4 Electrode part 10 Substrate 11 Photoresist material 11a Adhesive part 11b Non-adhesive part 12 Mask 12a Pattern opening 13 Micro conductive particles

Claims (4)

[Claims] 1. A bump forming method for forming a bump (2) on an electrode portion (4) formed on a semiconductor element (1), the method comprising applying a photosensitive material (11) to a substrate (10). And a predetermined pattern (12) corresponding to the formation position of the electrode part (4) on the photosensitive material (11) applied to the substrate (10).
exposing using a mask (12) having a), and selectively adhering only at a position (11a) corresponding to the formation position of the electrode part (4); On the photosensitive material (11a) that has the property,
Attaching a fine conductive particle (13) to be a bump (2); and the substrate (1) to which the fine conductive particle (13) is attached.
0) is brought into contact with the semiconductor element (1) to fix the fine conductive particles (13) to the electrode part (4) formed on the semiconductor element (1); and the substrate (10). Is separated from the semiconductor element (1) while maintaining the state where the fine conductive particles (13) are fixed to the semiconductor element (1), and the semiconductor element (1)
Forming a bump (2) on the electrode part (4) of the above. 2. When depositing the fine conductive particles (13) to be the bumps (2) on the photosensitive material (11), first, the fine conductive particles (1) are formed on the entire surface of the photosensitive material (11).
3) is sprayed onto the photosensitive material (11a) having adhesiveness to attach the fine conductive particles (13), and then the fine conductive particles present on the photosensitive material (11b) having no adhesiveness. The fine conductive particles (13) are adhered only on the photosensitive material (11a) having the adhesive property by removing (13).
A method for forming a bump as described above. 3. When the substrate (10) to which the fine conductive particles (13) are attached is brought into contact with the semiconductor element (1), a conductive resin or an active metal film is previously applied to the electrode portion (4). The bump forming method according to claim 1, wherein the bump is formed. 4. The fine conductive particles (13) are made of copper (C).
4. The bump forming method according to claim 1, wherein the bump is made of u) or gold (Au).