JP2000150556A - Method for forming bump electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently form bump electrodes with high accuracy at a low cost. SOLUTION: In a method in which bump electrodes 6 are formed by bonding conductive balls 3 onto electrode pads 5 arranged on a semiconductor device 4 by supplying ultrasonic energy, a template 1 having recesses 2 in which the conductive balls 3 can be put without allowing the balls 3 in such a way that the balls 3 are not completely buried in the recesses 2 and which are formed correspondingly to the positions of the electrode pads 5 on the device 4 is first prepared. Then the balls 3 are put in the recesses 2 of the template 1 and the balls 3 and pads 5 are brought into contact with each other by facing the template 1 and semiconductor device 4 oppositely to each other. While the pads 5 are brought into contact with the balls 3, the balls 3 are bonded to the pads 5 at the abutting portions of the balls 3 with the pads 5 by supplying ultrasonic energy A through at least either one of the template 1 and device 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a bump electrode by applying a conductive ball to an electrode pad provided on a semiconductor substrate or the like by applying ultrasonic energy. .

[0002]

2. Description of the Related Art When a semiconductor element or the like is connected to a circuit board, a method called face-down connection is often used. In this method, bump electrodes are arranged on the surface of the semiconductor element, the surface of the semiconductor element is opposed to the circuit board, and the semiconductor element is mounted on the circuit board with the bump electrodes aligned with the lands on the circuit board. And the semiconductor element is connected.

In order to make this face-down connection,
First, it is necessary to form a bump electrode on the surface of a semiconductor element or the like, which is conventionally performed by melting the tip of an Au (gold) wire into a spherical shape and pressing the electrode pad formed on the surface of the semiconductor element. Then, a method has been used in which ultrasonic waves are applied thereto and bonded to the electrodes.

Japanese Patent Application Laid-Open No. Hei 10-27803 discloses another method for forming a bump electrode. FIG.
(A) and (B) are process diagrams showing a conventional method for forming a bump electrode. In this method, first, as shown in FIG. 5A, an electronic component 11 such as a semiconductor chip is used.
The metal particles 13 are arranged on the electrode 12 formed on the surface of the electronic component 11, and then the pressing plate 14 having the funnel-shaped concave portion 14b is lowered onto the electronic component 11. And the recess 14
The position of the metal particles 13 is corrected by the taper of FIG.
(B), a force F is applied to the pressure plate 14 from above to press it. When ultrasonic vibration is applied at that time, the energy destroys the oxide film on the surfaces of the metal particles 13 and the electrodes 12, and the new surfaces come into contact with each other to cause alloying. It is said that electrodes can be formed.

[0005]

However, the above-mentioned Au
In the method of forming a ball bump using a wire, it is necessary to perform operations such as spheroidization of the tip of the Au wire, pressurization of the electrode, and supply of ultrasonic waves for each bump electrode. When the number is large, the working time becomes extremely long. In addition, when the pitch of the electrode pads is narrow, it is difficult to form bump electrodes with high precision at equal intervals. In contrast, Japanese Patent Application Laid-Open
The technique disclosed in Japanese Patent No. 27803 is advantageous in that a plurality of bump electrodes can be formed collectively, but the metal particles 13 are arranged in advance on the electrode 12 of the electronic component 11 such as a semiconductor element. This operation is extremely difficult, especially when the electrode pitch is narrow. Since the bonding of the metal particles 13 and the electrode 12 itself can be performed by ultrasonic energy, the flux necessary for ordinary solder bonding is unnecessary, but the metal particles 13 must be temporarily fixed on the electrode 12, and therefore, Requires a temporary fixing agent such as a flux. Accordingly, a cleaning step is required after the formation of the bump electrodes, which leads to a problem that the steps are complicated and the manufacturing cost is increased.

The present invention has been made to solve such a problem, and an object of the present invention is to efficiently provide a bump electrode.
Another object of the present invention is to provide a bump electrode forming method which can be formed with high precision and at low cost.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of forming a bump electrode by supplying a conductive ball to an electrode pad provided on a substrate by supplying ultrasonic energy. In the forming method, a template having a concave portion formed on the surface thereof corresponding to the position of the electrode pad on the base without the conductive ball being buried is prepared, and the concave portion of the template is formed in the concave portion of the template. The conductive ball is fitted, the template and the base face each other, the conductive ball and the electrode pad are brought into contact with each other, and ultrasonic energy is supplied through at least one of the template and the base. The conductive ball is joined to the electrode pad at a contact point between the conductive ball and the electrode pad.

In the method of forming a bump electrode according to the present invention, a bump electrode is formed by fitting a conductive ball into each concave portion and joining a plurality of conductive balls to an electrode pad on the base at a time. Even if the number of electrodes increases, bump electrodes can be formed very efficiently. Further, since the arrangement interval of the conductive balls is determined by the arrangement interval of the concave portions, the bump electrodes can be formed with high positional accuracy even when the interval between the bump electrodes to be formed is narrow. Furthermore, since the arrangement of the conductive balls is completed only by fitting the conductive balls into the recesses, the conductive balls can be easily arranged. Further, since it is not necessary to temporarily fix the conductive balls with a flux or the like, there is no need to apply a temporary fixing agent or to remove the temporary fixing agent by washing after the formation of the bump electrodes, thereby simplifying the process. In addition, since the conductive balls can be easily arranged, and a temporary fixing agent is not required and the process is simplified, the manufacturing cost can be reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. (A) to (C) of FIG.
FIG. 3 is a cross-sectional side view showing the periphery of a semiconductor element or a template on which a bump electrode is formed by an example of the bump electrode forming method according to the present invention in each step. First, a silicon template 1 shown in FIG. 1A is prepared. In the template 1, a concave portion 2 is formed on the surface corresponding to the position of the electrode pad 5 on the semiconductor element 4 as a base, in which the conductive ball 3 can be fitted without being buried. In this embodiment, the concave portion 2 is formed in a quadrangular pyramid shape, and becomes narrower as it goes deeper. Such a concave portion 2 can be formed by, for example, an anisotropic etching method.

[0010] Then, the template 1 is placed with the concave portion 2 side facing up, and conductive balls 3 are transferred into each concave portion 2.
It is fitted and arranged on the template 1. Next, the semiconductor element 4 is made to face the template 1, and the electrode pads 5 formed on the surface of the semiconductor element 4 are respectively brought into contact with the conductive balls 3 on the template 1. In this state, FIG.
As shown in (B), first, the conductive ball 3 is pressed through one or both of the semiconductor element 4 and the template 1 to deform the conductive ball 3 into a slightly crushed state. As a result, the contact area between the conductive ball 3 and the electrode pad 5 is increased, and then the semiconductor element 4 is ultrasonically vibrated in the direction indicated by the arrow A to make contact between the conductive ball 3 and the electrode pad 5. Ultrasonic energy is supplied to the contact point, and the conductive ball 3 and the electrode pad 5 are joined at the contact point between the conductive ball 3 and the electrode pad 5.

Here, even if an oxide film is formed on the surface of the conductive ball 3, this oxide film is destroyed by the ultrasonic vibration, so that the bonding between the conductive ball 3 and the electrode pad 5 is hindered. It will not be done. Thereafter, as shown in FIG. 1C, when the template 1 is excluded,
The semiconductor element 4 having the bump electrode 6 formed on each electrode pad 5 is completed. In FIG. 1C, the semiconductor element 4
Indicates a state in which they are arranged upside down.

As described above, according to the bump electrode forming method of the present embodiment, the conductive balls 3 are fitted into the respective recesses 2 and
A plurality of conductive balls 3 are collectively placed on an electrode pad 5 on a substrate.
Since the bump electrodes 6 are formed by joining the bump electrodes 6, the bump electrodes 6 can be formed very efficiently even if the number of the bump electrodes 6 increases. Further, since the arrangement interval of the conductive balls 3 is determined by the arrangement interval of the concave portions 2, even when the interval between the bump electrodes 6 to be formed is narrow, the bump electrodes 6 can be formed with high positional accuracy. Furthermore, since the arrangement of the conductive balls 3 is completed only by fitting the conductive balls 3 into the concave portions 2,
The conductive balls 3 can be easily arranged. Since it is not necessary to temporarily fix the conductive balls 3 with a flux or the like, there is no need to apply a temporary fixing agent or to remove the temporary fixing agent by washing after forming the bump electrodes, thereby simplifying the process. In addition, the conductive balls 3 can be easily arranged, and a temporary fixing agent is not required and the process is simplified, so that the manufacturing cost can be reduced.

In FIG. 1, only two concave portions 2 are formed in the template 1 and only two bump electrodes 6 are formed using the template 1. However, this is for the purpose of explanation only. Actually, in many cases, a large number of bump electrodes 6 are formed on the semiconductor element 4 and the like. In the above embodiment, the semiconductor element 4 is ultrasonically vibrated. However, even if the template 1 is ultrasonically vibrated, or both the semiconductor element 4 and the template 1 are ultrasonically vibrated, the 5 and the conductive ball 3 can be joined. In addition, in the process shown in FIG. 1B, when the semiconductor element 4 is ultrasonically vibrated, the entirety is simultaneously heated at a temperature lower than the melting point of the conductive ball 3, so that the conductive ball 3 is easily deformed. Such heating may shorten the time for applying the ultrasonic vibration or make the bonding between the conductive ball 3 and the electrode pad 5 more reliable.

Further, although the concave portion 2 is formed in the shape of a quadrangular pyramid so as to be narrower toward the inner portion, the concave portion 2 may be flat without forming an apex at the inner portion. There is no particular problem in fitting. Further, in the present embodiment, the bump electrode 6 is formed on the electrode pad 5 of the semiconductor element 4, but the bump electrode can be formed on the electrode pad on the circuit board by the same procedure. Next, a second embodiment of the present invention will be described. FIGS. 2A to 2C are cross-sectional side views showing the periphery of bump electrodes and related elements formed by the bump electrode forming method of the second embodiment for each step. In the figure,
The same elements as those in FIG. 1 are denoted by the same reference numerals. Second
This embodiment is different from the above-described embodiment in that the template 1 is formed with a hemispherical concave portion 7 instead of a quadrangular pyramid. In other respects, the second embodiment is exactly the same as the above embodiment, and therefore corresponds to FIGS. 2A to 2C corresponding to FIGS.
As shown in (A) to (C) of FIG.
The bump electrodes 6 can be formed on the semiconductor element 4 through the same process.

Therefore, in the second embodiment, the same effects as those of the above-described embodiment can be obtained.
Since the shape of the concave portion 7 is hemispherical, the conductive ball 3 can be temporarily fixed more reliably in the concave portion 2, and as a result, the contact between the conductive ball 3 and the electrode pad 5 can be superimposed. The sound wave energy is transmitted efficiently, and the bump electrode 6 can be formed more reliably and efficiently.

Next, a third embodiment of the present invention will be described. FIG. 3 is a cross-sectional side view showing the periphery of a semiconductor element when a conductive ball is bonded to the semiconductor element by the bump electrode forming method according to the third embodiment. In the figure, the same elements as those in FIG. 1 are denoted by the same reference numerals. The bump electrode forming method according to the third embodiment differs from the above-described embodiment in the structure of the template 1 and vacuum suction performed in the template 1. That is, as shown in FIG. 3, in the concave portion 2 formed in the template 1, a through-hole 8 is formed from the deep portion to the back surface of the template 1 by an etching method or the like. When fitting the conductive balls 3 into the recesses 2, vacuum suction is performed from the back side of the template 1 through the through holes 8 as shown by the arrow B, and in that state, the conductive balls 3 Is fitted into the recess 2. Then, the semiconductor element 4 is opposed to the template 1 and the electrode pads 5 on the semiconductor element 4 and the conductive balls 3 are aligned. Thereafter, the semiconductor element 4 is subjected to the same steps as in the first embodiment. A bump electrode is formed on each electrode pad 5 of FIG.

In the third embodiment, the same effects as those of the first embodiment can be obtained, and in addition, since the vacuum suction is performed through the through hole 8, the conductive balls 3 can be more securely recessed. 2 can be temporarily fixed. as a result,
Ultrasonic energy can be transmitted more efficiently,
It is possible to form the bump electrode more reliably and efficiently.

Next, a fourth embodiment of the present invention will be described. FIG. 4 is a cross-sectional side view showing the periphery of a semiconductor element when a conductive ball is joined to the semiconductor element by the bump electrode forming method according to the fourth embodiment. In the figure, the same elements as those in FIG. 1 are denoted by the same reference numerals. The fourth embodiment is different from the first embodiment in that a barrier layer made of metal or ceramic that does not react with the conductive balls 3 is formed on the entire surface of the template 1 including the inside of the recess 2. 9 is formed. Otherwise, the fourth embodiment is the same as the first embodiment, and the bump electrode 6 is formed on the semiconductor element 4 through the same steps as those of the first embodiment.

In the fourth embodiment, the same effects as those of the first embodiment can be obtained, and in addition, the barrier layer 9 is formed at the portion where the conductive ball 3 contacts. Even if the conductive ball 3 is formed of a material that reacts with silicon, the conductive ball 3 does not react with the template 1 due to the barrier layer 9 and a bump electrode can be formed correctly.

Incidentally, even if the barrier layer 9 is formed only at the location of the concave portion 2 or further only at the location where the conductive ball 3 contacts, the reaction between the conductive ball 3 and the template 1 can be avoided. The same effect can be obtained. In addition, recess 2
Is not only a quadrangular pyramid, but also a hemisphere as in the second embodiment, and further, a through hole 8 is formed as in the third embodiment. Also, the same effect can be obtained by forming the barrier layer 9. In the above four embodiments, the shape of the recess 2 is a quadrangular pyramid or a hemisphere, but the same effect can be obtained by forming the recess 2 in a conical shape.

[0021]

As described above, the present invention relates to a method for forming a bump electrode by applying a conductive ball to an electrode pad provided on a substrate by supplying ultrasonic energy. A template having a concave portion formed on the surface thereof corresponding to the position of the electrode pad on the substrate without the conductive ball being buried is prepared, and the conductive ball is fitted into the concave portion of the template. The conductive ball and the electrode pad are brought into contact with the template and the base facing each other, and ultrasonic energy is supplied through at least one of the template and the base to supply the conductive ball and the electrode. The conductive ball is joined to the electrode pad at a contact point with the pad.

Therefore, in the bump electrode forming method of the present invention, the bump electrodes are formed by fitting the conductive balls into the respective concave portions and joining the plurality of conductive balls to the electrode pads on the base at a time. Even if the number of bump electrodes increases, the bump electrodes can be formed very efficiently. Also,
Since the arrangement interval of the conductive balls is determined by the arrangement interval of the concave portions, the bump electrodes can be formed with high positional accuracy even when the interval between the bump electrodes to be formed is narrow. Furthermore, since the arrangement of the conductive balls is completed only by fitting the conductive balls into the recesses, the conductive balls can be easily arranged. Further, since it is not necessary to temporarily fix the conductive balls with a flux or the like, there is no need to apply a temporary fixing agent or to remove the temporary fixing agent by washing after the formation of the bump electrodes, thereby simplifying the process. In addition, since the conductive balls can be easily arranged, and a temporary fixing agent is not required and the process is simplified, the manufacturing cost can be reduced.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional side views showing the periphery of a semiconductor element or a template on which a bump electrode is formed by an example of a bump electrode forming method according to the present invention for each process.

FIGS. 2A to 2C are cross-sectional side views showing the periphery of bump electrodes and related elements formed by a bump electrode forming method according to a second embodiment for each step.

FIG. 3 is a cross-sectional side view showing a periphery of a semiconductor element when a conductive ball is bonded to the semiconductor element by a bump electrode forming method according to a third embodiment.

FIG. 4 is a cross-sectional side view showing a periphery of a semiconductor element when a conductive ball is bonded to the semiconductor element by a bump electrode forming method according to a fourth embodiment.

FIGS. 5A and 5B are process diagrams showing a conventional method for forming a bump electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Template, 2 ... Depression, 3 ... Conductive ball, 4 ... Semiconductor element, 5 ... Electrode pad, 6 ... Bump electrode, 7 ... Depression, 8 ... Through hole, 9 ... Barrier layer.

Claims (12)

[Claims] 1. A method for forming a bump electrode by applying a conductive ball to an electrode pad disposed on a substrate by supplying ultrasonic energy, wherein the bump is formed at a position of the electrode pad on the substrate. Correspondingly, a template having a concave portion formed on the surface that can be fitted without the conductive ball being buried is prepared, and the conductive ball is fitted into the concave portion of the template. The conductive ball and the electrode pad are brought into contact with each other, and ultrasonic energy is supplied through at least one of the template and the base to provide a conductive material at a contact position between the conductive ball and the electrode pad. Bonding a conductive ball to the electrode pad. 2. Applying pressure to the conductive ball through one or both of the substrate and the template to deform the conductive ball into a slightly crushed state before supplying the ultrasonic energy. 2. The method for forming a bump electrode according to claim 1, wherein: 3. The bump electrode forming method according to claim 1, wherein, when supplying the ultrasonic energy, the conductive ball is heated to a temperature lower than a melting point of the conductive ball. 4. The bump electrode forming method according to claim 1, wherein the concave portion is formed in a quadrangular pyramid shape, a hemispherical shape, or a conical shape that becomes narrower toward the back. 5. The method according to claim 1, wherein a material of the template is silicon. 6. The method according to claim 1, wherein the recess is formed by anisotropic etching or isotropic etching. 7. The method according to claim 1, wherein the base is made of a semiconductor or an insulator. 8. The method according to claim 1, wherein the substrate is a semiconductor device. 9. The method according to claim 1, wherein the base is a circuit board. 10. A through hole is formed in a deep portion of the concave portion to reach a back surface of the template, and the conductive member fitted into the concave portion by vacuum suction from the back surface of the template through the through hole. 2. The method according to claim 1, wherein the conductive ball is fixed. 11. The bump electrode formation according to claim 1, wherein a film made of a material that does not react with the conductive ball is formed at least at a position inside the concave portion where the conductive ball contacts. Method. 12. The method according to claim 1, wherein the material of the film is metal or ceramic.