JP3022151B2 - Capillary for wire bonding apparatus and method for forming electrical connection bump using the capillary - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for mounting a semiconductor device on a circuit board, and more particularly to a capillary for a wire bonding apparatus, and a terminal electrode of the circuit board and a semiconductor device using the capillary. And a method of forming an electrical connection contact (bump) for electrically connecting an electrode pad of the semiconductor device.

[0002]

2. Description of the Related Art In recent years, the degree of integration of ICs has increased, and the size of packages of semiconductor devices and the number of connection terminals have been increasing. The number of electrode pads per LSI chip has increased and the spacing between connection terminals has become narrower, making it difficult to mount a semiconductor device with conventional soldering techniques.

Recently, semiconductor devices such as LSI chips have been
Various methods for mounting directly on input / output terminal electrodes of a circuit board have been devised. Among them, a method of flip-chip mounting a semiconductor device on a circuit board in a face-down state is useful because the electrical connection between the semiconductor device and the circuit board can be made at once and the mechanical strength after connection is strong. It is said to be the way. The bumps (protruding electrodes) for electrically connecting the semiconductor device and the electrode pads of the circuit board are formed by a ball bonding method using an electrolytic plating method, a dipping method in a solder layer, a vapor deposition method, a wire bonding method, or the like. It is formed.

A conventional capillary for a wire bonding apparatus is described in, for example, a bonding handbook and a capillary catalog of Micro Switzerland.
FIG. 19 shows a conventional capillary 100 for a wire bonding apparatus as an example, and FIG. 20 (a) is a view schematically showing a cross section of a tip portion 110 thereof. FIG. 20 (b)
The shape of the capillary tip 110 is shown in more detail.

As shown in FIG. 20A, a cylindrical capillary 100 has a wire outlet hole 102 for inserting a metal wire for bonding therein. The size of the wire outlet hole 102 is 25 μmφ to 50 μm.
It is about μmφ. Tip portion 110 of capillary 100
Is formed at an angle α of about 30 ° in consideration of the bonding interval and the shape and size of the metal wire (or bump) after bonding.

For example, the shape of the tip of the capillary 110 when a metal wire of about 25 μmφ is used is shown in FIG. In this case, the hole diameter H: 3
8 μm, tip diameter T: 203 μm, and chamfer diameter CD: 74 μm. Such a capillary 10
By using 0, a bump can be formed on an electrode pad of a semiconductor device or an electrical connection to a terminal electrode of another circuit board can be made. The capillaries as shown in FIGS. 20A and 20B are usually used for bonding having a bonding pitch of about 120 to 140 μm.

FIGS. 21, 22 (a) and 22 (b) show another conventional capillary 200 for a wire bonding apparatus. The capillary 200 is usually
Used for bonding with a bonding pitch of 140 μm or less. As shown in FIG. 21, the cylindrical capillary 200 has a bottle neck 210 having a narrow tip portion in order to accommodate a narrower bonding pitch. The height NH of the bottleneck 210 is usually 5
In the example shown in FIG.
60 μm. Like the capillary 100, the capillary 200 has a wire lead-out hole 102 for inserting a metal wire for bonding inside. The size of the wire outlet hole 102 is approximately 25 μmφ to 50 μmφ. Bottleneck part 210 of capillary 200
Is formed at an angle β of about 10 ° in consideration of the bonding interval and the shape and size of the metal wire (or bump) after bonding.

For example, when a metal wire of about 25 μmφ is used, the shape of the tip of the capillary 200 is shown in FIG.
2 (b). In this case, the hole diameter H: 38
μm, tip diameter T: 152 μm, and chamfer diameter CD: 64 μm. Such a capillary 200
By using a semiconductor device, a bump can be formed on an electrode pad of a semiconductor device, or an electrical connection can be made to a terminal electrode of another circuit board.

Next, a conventional method for forming a bump of a semiconductor device by a ball bonding method using the above-described capillary for wire bonding will be described. For example, JP-A-2-34949 discloses an electric connection bump having a two-step projection shape (hereinafter referred to as a two-step bump).
And a conventional method for forming a two-stage bump using a capillary.

FIGS. 23A to 23D show a method of forming a two-stage bump 107 by using a capillary 101 on an electrode pad 103 formed on an IC chip 106 by a conventional ball bonding method. Is shown schematically.

First, as shown in FIG. 23A, a metal wire 104 of 25 μmφ is passed through a wire lead-out hole 102 of a capillary 101. Then, by applying heat energy to the tip of the metal wire 104 by gas flame, electric pulse, ultrasonic vibration, or the like, a ball 105 having a diameter approximately two to three times the diameter of the metal wire 104 is formed. .

Next, as shown in FIG. 23B, the ball 105 formed at the tip of the metal wire 104 is moved down the capillary 101 so that the IC chip 10
6 is brought into contact with the electrode pad 103. The ball 105 is fixed to the electrode pad 103 by a method of thermocompression bonding or by applying ultrasonic vibration, and the bottom 109 of the bump 107 is formed (first bonding). The bottom 109 has an outer diameter of about 80 to 90 μmφ and a height of about 15 to 30 μm.

Then, as shown in FIG. 23C, the capillary 101 is formed into a loop while the bottom 109 of the bump 107 and the metal wire 104 passed through the wire lead-out hole 102 of the capillary 101 are connected. Move. The capillary 101 first rises vertically above the bottom 109 of the bump 107, moves so as to draw a loop-shaped trajectory, and then cuts the metal wire 104 while descending vertically (second bonding: FIG. 23).
(D)). As shown in FIG. 23D, the metal wire 104 is formed in a ring shape or an inverted U shape on the bottom 109 by the loop-shaped movement of the capillary 101. This portion forms the top 108 of the bump 107.
The two-stage bump 107 is formed by cutting the metal wire 104 by the edge portion 111 at the end of the capillary 101, as shown in FIG.

The bonding pressure is set in the range of 20 to 45 g per bump depending on the material and diameter of the wire for both the first and second bonding. FIG.
FIG. 4 shows the shape of a typical two-stage bump formed by a conventional ball bonding method. The outer diameter R of the two-stage bump 107 (stud bump) is 80 to 90 μm.
φ, and the overall height h ₁ is about 60 to 80 μm.

The two-stage bump 10 obtained as described above
In order to make the heights 7 uniform, a leveling step of pressing the bump 107 with a smooth surface is usually performed (see FIG. 25).
The bumps formed by the ball bonding method
This is because the variation in height is larger than that of bumps formed by other methods. When a conductive adhesive is used for the bonding layer between the semiconductor device and the circuit board, leveling is performed to stabilize the transfer amount of the conductive adhesive.

As shown in FIG. 25, in the leveling step, the two-stage bump 107 formed on the electrode pad 103 of the IC chip 106 is pressed against the smooth surface 112 in a face-down state. The leveling load is
Usually, it is about 50 g per bump. The leveling load is adjusted according to the material and diameter of the wire. A typical shape of the leveled two-stage bump 107 is shown in FIG.
Is shown in By leveling, the two-stage bump 107
Total height h ₁ of is aligned in the range of 40 to 50 .mu.m.

[0017]

The conventional capillary and the conventional bump forming method as described above require a step of forming a bump on a semiconductor device and a leveling step for further shaping the formed bump. costly. Further, an apparatus for performing leveling is also separately required.

However, if the leveling is not performed, the following problems occur, and it is not preferable to omit the leveling step. First, since the top 108 of the bump (not leveled) formed by the ball bonding method has a ring shape or an inverted U-shape, the area of the end 113 of the top 108 is small. (Figure 2
4), and the contact area with the terminal electrode of the circuit board is small.
In addition, since the bumps vary greatly in height, a highly reliable connection cannot be made if the bumps are mounted as they are. Second, when a conductive adhesive is used for the bonding layer,
In the above-described shape of the bump before leveling, the amount of the conductive adhesive transferred to the bump tip portion is small, and the variation in the transferred amount is large, so the adhesive strength after the conductive adhesive is cured is small, so the bonding is performed. Low reliability. Also, the connection resistance value increases.

In the conventional bump forming method as described above, a typical bump 107 shown in FIG.
27 (a) to 27 (c) in addition to the shape shown in FIG. The shape of the bump shown in FIGS. 27A and 27B is called “secondary peeling”, and after the capillary 101 cuts the metal wire 104, the ring-shaped or inverted U-shaped portion 114 becomes the bump 1.
07 has been removed from the main body. FIG.
The shape of the bump shown in (c) is called “tail standing”. The tail part 115 that protrudes beside the bump
However, a bump having a diameter exceeding 1/4 of the diameter at the bottom of the bump is defective. Such bumps occur when the metal wire 104 is not successfully cut in place by the edge 111 of the capillary 101. Bumps of these shapes are undesirable bumps as connection contacts.

In the bump shown in FIG. 27A, the top 116 is broken into two parts, so that sufficient strength cannot be obtained. Further, in the case of the bump shown in FIG. 27C, the tail 115 extends laterally, so that when the conductive adhesive is held at that portion and spreads,
The danger of shorting with adjacent bumps or electrodes is greatly increased. Therefore, these unfavorably shaped bumps lead to poor connection or short-circuit, so that the semiconductor device and the circuit board cannot be connected with high reliability.

FIGS. 28 (a) and 28 (b) show the shapes of defective bumps generated in the conventional leveling process. These bumps have an unfavorable shape due to the fact that the tops fall laterally during leveling.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to form a bump for connecting a semiconductor device and a circuit board easily and with high reliability by a separate process. It is an object of the present invention to provide a ball bonding capillary which can be formed without adding a hole, and a bump forming method using the capillary.

It is another object of the present invention to provide a ball bonding capillary which prevents formation of a bump having an unfavorable shape and which can form a bump having a stable shape with little variation, and a capillary for the ball bonding. An object of the present invention is to provide a method for forming a used bump.

[0024]

The method of forming an electrical connection bump according to the present invention is a method of forming a bump on an electrode pad of a semiconductor device by using a capillary for ball bonding. (A) forming a portion in a ball shape, and (b) forming a bottom portion of a bump by pressing the tip of the ball shape on the electrode pad.
If, (c) forming a top portion over the bottom portion, wherein
(D) pressing and shaping the apex with a leveling surface provided on the side surface of the capillary to level the apex. In the step (c), the capillary moves so as to draw a loop trajectory above the bottom of the bump, and the metal wire forming the top of the bump is formed on the bottom in a ring shape or an inverted U shape. It is characterized by being performed. Before SL capillary presses the ball-shaped tip of the metal wire on the bottom to the electrode pad, the ball-shaped tip having a pressing surface for crimping the electrode pad, the center of the pressing surface , said metal wire lead-out hole is provided for supplying the distance between the the sides of the capillary leveling surface for the pressing shaping is being provided top of the bump, and the pressing surface and the leveling face Is the same as the height of the bump to be formed . Further, the leveling surface has an uneven surface. Further, the leveling surface has a guide portion formed so as to protrude downward.

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

In the steps (b), (c) and (d), the capillary performs an operation in the Z direction, and the stage of the bonding apparatus (bonder) performs an operation in the XY direction, and the movement is performed. By combining
A desired two-stage bump (stud bump) may be formed.

[0038]

The present invention provides a method for forming a bump on an electrode pad of a semiconductor device by providing a member for leveling the bump formed on the electrode pad on a capillary for forming the bump by a ball bonding method. At the same time, bump leveling can be performed. The leveling member is preferably provided as a protrusion projecting from the outer periphery of the capillary. The capillary has a pressing member (lower end portion of the capillary) for pressing the top end of the metal wire on the ball to the electrode pad,
After the bump is formed on the electrode pad, the metal wire connected to the bump is cut by the edge of the pressing member.
As soon as the metal wire is cut, the bump is pressed and shaped by the leveling member. Since the lower end surface (second lower end surface) of the leveling member is formed at a predetermined height from the lower end surface (first lower end surface) of the capillary, it is pressed until the lower end surface of the capillary contacts the electrode pad. Thereby, the height of the bump is adjusted to a predetermined height.

As described above, since the leveling is performed simultaneously in the bump forming process, the number of processes can be reduced. Therefore, the cost can be reduced.

[0040]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a view showing a capillary 1 for ball bonding according to a first embodiment of the present invention.
(A) is a schematic sectional view of the tip portion 10. FIG.
(B) shows the shape of the tip portion 10 of the capillary 1 in more detail.

As shown in FIG. 1, the cylindrical capillary 1 has a protruding portion 3 which is a leveling member provided on the outer peripheral portion of the distal end portion 10. The capillary 1 is made of ceramic or artificial ruby. As shown in FIG. 2A, the lower end surface (leveling surface) 31 of the protrusion 3 is substantially parallel to the face (lower end surface) 11 of the capillary 1, and
Is provided so that the height from the face 11 at the front end of the is a predetermined value d. The size of the lower end face 31 can be set in accordance with the bonding pitch and the size of the tip diameter of the bump to be leveled.

Inside the capillary 1, a wire lead-out hole 2 for inserting a metal wire for bonding is provided. The size of the wire outlet hole 2 is 25 μmφ or more.
It is about 50 μmφ. An angle α of about 10 to 30 ° is provided outside the tip portion 10 of the capillary 1 in consideration of the bonding interval and the shape and size of the metal wire (or bump) after bonding.

For example, when a metal wire of about 25 μmφ is used, the shape of the tip of the capillary 10 is shown in FIG.
(B). In this case, the hole diameter H: 38 μm, the chip diameter T: 203 μm, and the chamfer diameter CD: 74
μm.

The above-described capillary 1 is used, for example, by being attached to a bonder 500 as shown in FIG. In bonder 500, capillary 1
Is attached to the tip of an arm 510 which is also an ultrasonic transmission tool, and a device (IC chip) 501 to be bonded is placed on a bonding stage 520. The capillary 1 moves up and down in the vertical direction together with the arm 510, and the device 501 moves or rotates in the horizontal direction (XY directions) together with the bonding stage 520. The combination of these vertical and horizontal movements allows the capillary 1 to make any movement with respect to the device 501.

Next, the capillary 1 according to the first embodiment will be described.
A method of forming a bump of a semiconductor device by a ball bonding method using the method will be described. FIG. 4 (a) to (d)
Can be manufactured by the ball bonding method according to the present invention.
The outline of a method of forming the two-stage bump 7 using the capillary 1 on the electrode pad 13 formed on the chip 6 is shown.

First, as shown in FIG. 4A, a metal wire 4 of 25 μmφ is passed through a wire lead-out hole 2 of a capillary 1. Then, by applying thermal energy to the tip of the metal wire 4 by ultrasonic vibration, gas flame, electric pulse, or the like, a ball 5 having a diameter about 2 to 3 times the diameter of the metal wire 4 is formed. .

The material of the metal wire 4 is Au, Al, Cu
Any metal can be used as long as it can use the wire bonding method. The material and wire diameter of the metal wire 4 can be selected according to the outer diameter and height of the bump 7 to be formed.

Next, as shown in FIG. 4B, by lowering the capillary 1, the ball 5 formed at the tip of the metal wire 4 is brought into contact with the electrode pad 13 of the IC chip 6.
Contact. The ball 5 is fixed to the electrode pad 13 by a thermocompression bonding method or by applying ultrasonic vibration to form the bottom 9 of the bump 7 (first bonding). This first bonding is performed using the face 11 at the lower end of the capillary 1. The bottom 9 has an outer diameter of 80 to 90 μm
It is formed to have a size of about φ and a height of about 20 to 30 μm.

Then, as shown in FIG. 4C, the capillary 1 is connected to the IC chip 6 while the bottom 9 of the bump 7 and the metal wire 4 passed through the wire lead-out hole 2 of the capillary 1 are connected. Move in a loop.
The capillary 1 first rises vertically above the bottom 9 of the bump 7 and then moves so as to draw a loop-shaped trajectory. As shown in FIG. 4D, the capillary 1 moves in a loop with respect to the IC chip 6 so that the bottom 9 is moved.
The metal wire 4 is formed in a ring shape or an inverted U shape on the top. This portion forms the top 8 of the bump 7. The height of the top 8 at this stage is about 40 to 50 μm.

Thereafter, the edge portion 21 of the capillary 1
Is moved to the outer periphery of the bottom 9 of the bump 7, and the metal wire 4 is cut by the edge portion 21 while descending vertically (see FIG. 4 (e)). The capillary 1 continues to descend as it is, and as shown in FIG. 5, the bump 7 is pressed and shaped by the lower end face 31 of the protruding portion 3 provided on the outer periphery of the capillary 1 (second bonding). At this time, the capillary 1 descends until the face 11 contacts the electrode pad 13. The overall height of the bump 7 is the face 11 of the capillary 1
And the lower end face 31 of the projection 3 and the height difference (that is, the predetermined value d) are equalized, and leveling is performed.

The pressure during bonding may be, for example,
The bonding pressure is 25-45 g per bump, the second
The bonding pressure can be set in the range of 70 to 95 g per bump. The pressure at the time of this bonding is adjusted by the material and diameter of the wire.

FIG. 6 shows the shape of a typical two-stage bump formed by the ball bonding method according to this embodiment. The two-stage bump 7 (stud bump) has an outer diameter R of about 80 to 90 μmφ and an overall height h ₁ of 40 to 5 μm.
About 0 μm, the diameter r of the tip 81 of the top 8 is 40 to 50 μm
It is about. The height h ₂ of the bottom 9, 15～25Myu
m. These values can be changed according to the bonding pitch.

As described above, according to the present embodiment, in the step of forming the bumps 7, the leveling of the bumps 7 can be performed simultaneously. The time required for this step is substantially the same as the time required for forming the bump 107 in the conventional technique. Therefore, the time required for the conventional leveling process can be reduced as it is.

According to the bonding method of the present invention, since the bump 7 is pressed and shaped (leveled) at the same time as the formation of the bump 7, the bump 7 is formed as shown in FIGS.
Are difficult to form. As shown in FIG. 5, the capillary 1 descends until the face 11 contacts the electrode pad 13 and presses the bump 7, so that the metal wire 4 forming the top 8 of the bump 7 is easily cut. .

Also, at the time of leveling, one side of the bump is supported by the side of the capillary 1, so that
It is possible to prevent the top portion from falling down during leveling as shown in FIG.

As described above, according to the present invention, it is possible to prevent the formation of a bump having an undesired shape (defective bump) which cannot be improved by the conventional leveling process, and to keep the bump shape constant. Can be more reliably connected to the circuit board.

Further, in this embodiment, the shape of the capillary 1 is cylindrical, and the shape of the protruding portion 3 is basically the shape of the lower end face 31 in consideration of the workability in manufacturing the capillary 1. It is formed in a cylindrical shape so as to be circular (see FIGS. 7A and 7D). The projection 3 is the capillary 1
Any other shape may be used as long as it has a lower end face that protrudes from the outer periphery of the bump and is used to level the bump 7. For example, as shown in FIGS. 7 (b) and 7 (e), a disc-shaped projection 3a may be used, and as shown in FIGS. 7 (c) and 7 (f), the projection 3b Can also be provided. In addition, the lower end surface 31 of the protrusion 3 is
It is desirable that the leveling be made parallel to the IC chip 6.

Next, some examples of the semiconductor unit in which the semiconductor device (IC chip) on which the bumps 7 are formed as described above are mounted on a circuit board will be described. In the following examples, the shape of the two-stage bump 7 is schematically illustrated in the drawings.

FIG. 8 shows a semiconductor unit 600 in which the semiconductor device formed as described above is mounted on a lead (terminal electrode) group 12 formed on a flexible resin film via a bump 7. I have. In this example, bump 7 is A
u bump. The material of the lead group 12 can be formed by Au plating or Sn plating with Ni as a base, Al, Cu, solder, or the like. After the bumps 7 and the lead groups 12 are aligned so as to be at predetermined positions, the bumps 7 and the lead groups 12 are pressurized by a heated bonding tool.
The bump 7 and the lead group 12 formed on the flexible resin film are electrically connected by alloying the materials or by performing thermocompression bonding. In the case of thermocompression bonding, ultrasonic vibration may be used together,
Alternatively, pressure bonding using only ultrasonic vibration may be used. The material of the lead group 12 may be Au or Sn plating with Ni as a base, or any of Al, Cu and solder.

FIGS. 9A and 9B show a method of bonding the bumps 7 of the semiconductor device on the terminal electrodes 12 'of the circuit board 15 with the conductive adhesive 14, and the semiconductor mounted in this manner. A unit 700 is shown. FIG.
As shown in (a), a conductive adhesive 14 is applied to the tip of the bump 7 of the semiconductor device by a transfer method or a printing method. By using the bumps 7 formed in a two-step projection shape, it is possible to prevent the conductive adhesive 14 in a necessary amount or more from adhering to the bumps 7 and to apply an appropriate amount of the conductive adhesive 14. After the application of the conductive adhesive 14, FIG.
As shown in (1), the semiconductor device is mounted on the circuit board 15 in a face-down state. After the positioning is performed so that the bump 7 comes into contact with a predetermined position of the terminal electrode 12 ′ of the circuit board 15, the conductive adhesive 14 is thermally cured at 80 to 150 ° C. to form a bonding layer. As a result, the bumps 7 of the semiconductor device are electrically connected to the terminal electrodes 12 'on the circuit board 15, and the semiconductor device is mounted on the circuit board.

According to the present embodiment, it is possible to prevent the formation of a defective bump having secondary peeling or tailing, so that
There is no possibility that the conductive adhesive is held and spread at the peeled portion or the tail portion, and there is little danger of short-circuiting with an adjacent bump or electrode. Therefore, the semiconductor device and the circuit board can be connected with high reliability.

FIGS. 10A and 10B show a semiconductor unit in which a semiconductor device is electrically connected to a terminal electrode 12 'of a circuit board 15 using an anisotropic conductive material. As shown in FIG. 10A, the semiconductor unit 8
At 00, the terminal electrode 1 formed on the circuit board 15
A thin anisotropic conductive material 16 is disposed on 2 ′. The semiconductor device on which the bumps 7 are formed is mounted thereon in a face-down state. By heating the semiconductor device while pressing it against the circuit board 15, the portion of the anisotropic conductive material 16 sandwiched between the bump 7 and the terminal electrode 12 ′ is thermocompression bonded to establish electrical connection. Obtainable.

In the portion of the anisotropic conductive material 16 to be thermocompression-bonded, the conductive particles contained in the anisotropic conductive material 16 are pressed by the bumps 7 and pressed together, and the conductive particles are pressed by the terminal electrode 12 ′. The bump 7 and the terminal electrode 12 'are electrically connected by being immersed in the surface of the substrate. Since the conductive particles are separated from each other in the portion that is not pressed, the electrical insulation is maintained.

FIG. 10B shows an anisotropic conductive material 16 ′ thicker than the sum of the height of the bump 7 and the thickness of the terminal electrode 12.
9 shows a semiconductor unit 900 in the case of using. On the terminal electrode 12 formed on the circuit board 15, a thick anisotropic conductive material 16 'is arranged, and the semiconductor device having the bumps 7 formed thereon is placed face down. By heating the semiconductor device while pressing it against the circuit board 15, the portion of the anisotropic conductive material 16 ′ sandwiched between the bump 7 and the terminal electrode 12 ′ is thermocompression-bonded and electrically connected. Can be obtained. Also in this case, only the portion sandwiched between the bump 7 and the terminal electrode 12 'is pressure-bonded, and the other portions are kept electrically insulative. The anisotropic conductive material 16 'other than the crimped portion acts as an insulating adhesive, and bonds the semiconductor device and the circuit board by thermosetting the resin. (Embodiment 2) FIG. 11 is a diagram showing a capillary 41 for ball bonding according to a second embodiment of the present invention.
FIG. 2A is a schematic sectional view of the tip portion 40. FIG.
(B) shows the shape of the tip portion 40 of the capillary 41 in more detail. The capillary 41 has a bottleneck 400 having a thin tip portion in order to form a bump at a finer bonding pitch. The height of the bottleneck 400 is usually about 500 μm, and FIG.
In the example shown in FIG. 2A, it is 460 μm.

As shown in FIG. 11, the cylindrical capillary 41 has a projection 43 provided on the outer periphery of the bottleneck 400. The capillary 41 is made of ceramic or artificial ruby. FIG.
As shown in (a), the lower end surface (leveling surface) 431 of the protrusion 43 is substantially parallel to the face 411 at the tip of the capillary 41, and the height of the tip of the capillary 41 from the face 411 is predetermined. Is provided. Inside the capillary 41, similarly to the capillary 1, a wire lead-out hole 2 for inserting a metal wire for bonding is provided. The size of the wire outlet hole 2 is about 25 μmφ to 50 μmφ. The outer side of the tip of the capillary 41 (bottleneck 400) is formed at an angle of about 10 ° in consideration of the bonding interval and the shape and size of the metal wire (or bump) after bonding.

For example, when a metal wire of about 25 μmφ is used, the shape of the tip of the capillary 41 is changed as shown in FIG.
This is shown in FIG. In this case, the hole diameter H: 38 μm, the chip diameter T: 152 μm, and the chamfer diameter CD: 6
4 μm.

The capillary 41 as described above is used by being attached to, for example, a bonder 500 as shown in FIG. Capillary 4
The method of forming the two-step bumps 7 using the method 1 is exactly the same as the method described in the first embodiment.

As described above, according to the second embodiment, even in the case of a finer bonding pitch, similar to the first embodiment, the bump 7 can be formed without providing a separate leveling step.
In the process of forming the bumps, the bumps 7 can be simultaneously leveled.

According to the second embodiment, even in the case of a finer bonding pitch, formation of an undesired bump (defective bump) which cannot be improved by the conventional leveling process is prevented, and the bump shape is reduced. Can be kept constant, so that the semiconductor device can be more reliably connected to the circuit board. (Embodiment 3) FIG. 13 is a sectional view of the tip of a capillary 51 for ball bonding according to a third embodiment of the present invention. In the third embodiment, as shown in FIG. 13, the cylindrical capillary 51 has a protruding portion 53 provided on the outer peripheral portion of the distal end. An uneven surface 54 is formed on the lower end surface (leveling surface) 531 of the protrusion 53. The “irregular surface” means a surface roughened by forming fine grooves in a range of 0.1 to 10 μm in various directions. Other portions of the capillary 51 can be formed in the same manner as the above-described capillary 1 or the capillary 41 according to the bonding pitch.

The method of forming two-stage bumps using the capillary 51 is the same as the method described in the first embodiment. In the present embodiment, in the second bonding in which the bump 57 is pressed and shaped by the lower end surface 531 of the projecting portion 53 provided on the outer peripheral portion of the capillary 51, the lower end surface 531
An uneven surface 58 is formed on the top of the bump 57 by the uneven surface 54 formed on the substrate. At that time, ultrasonic vibration may be applied in order to form the uneven surface 58 more effectively.
FIG. 14 shows a two-stage bump 57 formed using the capillary 51. FIGS. 15A and 15B show a method of bonding the bump 57 of the semiconductor device on the terminal electrode 12 ′ of the circuit board 15 by the conductive adhesive 14, and the semiconductor unit 710 mounted in this manner. Is shown. The bonding method is the same as that described in Example 1 with reference to FIGS.

By using the bumps 57 formed in a two-step projection shape, it is possible to prevent the conductive adhesive 14 more than necessary amount from adhering to the bumps 57 and to apply an appropriate amount of the conductive adhesive 14. . In this embodiment, the bump 57
By forming the uneven surface 58 on the top of the substrate, the bonding area of the conductive adhesive 14 can be increased. further,
When the charged particles of the conductive adhesive 14 enter the concave portions of the uneven surface 58, more reliable electrical conductivity can be obtained. Therefore, a more reliable semiconductor unit can be obtained.

FIGS. 16A and 16B show semiconductor units 810 and 9 in which a semiconductor device is electrically connected to terminal electrodes 12 of circuit board 15 using an anisotropic conductive material.
10 is shown.

Semiconductor units 810 and 910 are mounted in the same manner as semiconductor units 800 and 900 described in the first embodiment, respectively. Semiconductor unit 810
In steps 910 and 910, the bumps 57 are formed with the uneven surface 58 at the tip end, so that the conductive particles
The surface area in contact with 7 is increased, and the electrical contact is improved. Further, since the uneven surface 58 is formed, the surface area of the conductive particles of the anisotropic conductive material 16 or 16 ′ in contact with the bump 57 and the bonding area of the resin are increased, so that the conductivity and the bonding strength are increased. A more reliable connection can be obtained.

Since the size of the conductive particles in the anisotropic conductive material is about 1 μm to 10 μm, the uneven surface formed at the tip of the bump is required so that electrical contact can be effectively obtained. It is necessary to appropriately select the size of the 58 irregularities and the size of the conductive particles.

Although the uneven surface 54 is provided over the entire lower end surface 531 of the protruding portion 53 in FIG. 13, it may be provided only on a necessary part. Further, in the present embodiment, the shape of the capillary 51 is cylindrical, and the shape of the protruding portion 53 is basically circular in shape of the lower end surface 531 in consideration of workability when manufacturing the capillary 51. As shown in FIG. If the protruding portion 53 protrudes from the outer periphery of the capillary 51 and has a lower end surface and an uneven surface for leveling the bump 57,
Other shapes can be used as described in the first embodiment. It is desirable that the lower end surface 531 of the protrusion 53 be parallel to the IC chip 6 when leveling. (Embodiment 4) FIG. 17 is a sectional view of a tip portion of a capillary 61 for ball bonding in a fourth embodiment of the present invention. In the fourth embodiment, as shown in FIG. 17, the cylindrical capillary 61 has a protruding portion 63 provided on the outer peripheral portion at the distal end. The lower end surface 631 of the protrusion 63 has a leveling surface 65 and a guide portion 64. As shown in FIG. 17, the leveling surface 65 of the protrusion 63 is substantially parallel to the face 611 at the lower end of the capillary 61, and the height from the face 611 at the tip of the capillary 61 is a predetermined value d. It is provided as follows. The value of the height d is set according to the height of the bump to be formed.

The guide portion 64 is a portion provided along the outer periphery of the lower end surface 631 and protruding in the vertical direction (downward). The guide portion 64 is for holding the top 68 of the two-stage bump 67 in the second bonding (leveling) and preventing the top 68 of the two-stage bump 67 from falling down as shown in FIG. . The shape of the guide portion 64 is not particularly limited as long as the shape of the top portion 68 of the bump 67 to be formed can sufficiently hold the transferred adhesive. For example, the top 68 can be formed such that the sides of the top 68 are vertical. FIG. 18A shows a two-stage bump 67 formed using the capillary 61.

Other portions of the capillary 61 can be formed in the same manner as the capillary 1 or the above-described capillary 41 according to the bonding pitch. The method of forming the two-stage bump 67 using the capillary 61 is as follows.
This is the same as the method described in the first embodiment. In the present embodiment, in the second bonding, the bump 67 is pressed and shaped by the leveling surface 65 of the lower end surface 631 of the projecting portion 63 provided on the outer peripheral portion of the capillary 61, and at this time, formed on the outer peripheral portion of the lower end surface 631 Guide part 6
4 supports the top 68 of the bump 67. This can prevent the top 68 of the two-stage bump 67 from falling down. Further, it is possible to prevent the occurrence of defective bumps which have occurred in the conventional leveling process as shown in FIGS. 28 (a) and 28 (b).

Further, by providing the guide portion 64, the area of the tip of the top portion 68 of the bump 67 can be formed to a substantially constant size. Therefore, the bump 67 can be formed in a stable shape with less variation. Can be.

Although the guide portion 64 is provided over the entire outer periphery of the lower end surface 631 in FIG. 17, it may be provided only on a necessary part. In the present embodiment, the shape of the capillary 61 is cylindrical, and
The shape of No. 3 is formed in a cylindrical shape so that the shape of the lower end face 631 is basically circular in consideration of workability in manufacturing the capillary 61. The projection 63 is the capillary 6
If it is provided with a leveling surface for projecting from the outer periphery of the first and a leveling surface for leveling the bump 67 and a guide portion for supporting the top portion 68 of the bump 67, another shape as described in the first embodiment is used. Can also. It is desirable that the leveling 65 of the projection 63 be parallel to the IC chip 6 when leveling.

[0080]

As described above, according to the present invention, there is provided a method of forming a bump on an electrode pad of a semiconductor device by using a capillary for ball bonding, wherein the tip of a metal wire is formed in a ball shape. A step of forming a bottom of a bump by pressing a ball-shaped tip on the electrode pad, a step of forming a top on the bottom, and a step of crushing and leveling the top. In the step of forming the bumps of the device, the bumps can be leveled at the same time, so that a bump having a desired height and shape can be obtained without providing a separate leveling step, and the process time and cost can be reduced. . Also, on the side of the capillary, a leveling surface for crushing the top of the bump is provided.In leveling, one side of the bump is supported by the side of the capillary. It is possible to keep the shape of the bump constant while preventing it. In addition, since the distance between the pressing surface and the leveling surface is set to the height of the bump to be formed, the height of the bump after leveling can be made substantially constant, and a bump having a stable shape with little variation can be formed. .

As a result, the semiconductor device and the circuit board can be more reliably electrically connected and bonded, so that an extremely stable and highly reliable semiconductor device can be mounted. Further, the number of manufacturing steps can be reduced and the effect more than before can be obtained at low cost, so that the versatility is extremely high in practical use.

[Brief description of the drawings]

FIG. 1 is a side view of a capillary for ball bonding according to a first embodiment of the present invention.

2A is a schematic cross-sectional view of the tip of the capillary shown in FIG. 1; FIG. 2B is a cross-sectional view showing the shape of the tip of the capillary in detail;

FIG. 3 is a configuration diagram showing an example of a bonder to which the capillary of the present invention is attached.

FIGS. 4A to 4E are process diagrams schematically showing a method of forming a two-stage bump using a capillary according to the present invention.

FIG. 5 is a cross-sectional side view showing a state where a bump is pressed and shaped using a capillary according to the present invention.

FIG. 6 is a side view showing the shape of a typical two-stage bump formed by a ball bonding method using a capillary according to the first embodiment.

7 (a) to 7 (f) are perspective views and cross-sectional views of a capillary showing possible shapes of a projection of the capillary of the present invention, respectively.

FIG. 8 is a side view showing an example of a package (semiconductor unit) of a semiconductor device having two-step bumps formed according to the present invention.

FIGS. 9A and 9B are cross-sectional views showing a state before a semiconductor device having a two-stage bump formed according to the present invention is bonded to a circuit board with a conductive adhesive and a mounted semiconductor unit. Side view

FIGS. 10A and 10B are cross-sectional views of a semiconductor unit in which a semiconductor device having two-stage bumps formed according to the present invention is electrically connected to a circuit board using an anisotropic conductive material. Side view

FIG. 11 is a side view showing a capillary for ball bonding according to a second embodiment of the present invention.

12A is a schematic cross-sectional view of the tip of the capillary shown in FIG. 11, and FIG. 12B is a cross-sectional view showing the shape of the tip of the capillary in more detail.

FIG. 13 is a cross-sectional view of a tip portion of a capillary for ball bonding according to a third embodiment.

FIG. 14 is a side view showing the shape of a two-stage bump formed using a capillary according to the third embodiment.

FIGS. 15A and 15B are cross-sectional views showing a state before a semiconductor device having two-stage bumps formed according to the present invention is bonded to a circuit board with a conductive adhesive and a mounted semiconductor unit. Side view

FIGS. 16 (a) and (b) are cuts of a semiconductor unit in which a semiconductor device having a two-stage bump formed according to the present invention is electrically connected to a circuit board using an anisotropic conductive material. Side view

FIG. 17 is a sectional view of a tip portion of a capillary for ball bonding according to a fourth embodiment.

FIG. 18A is a side view showing a two-stage bump formed using a capillary according to a fourth embodiment; FIG. 18B is a side view showing the shape of a two-stage bump having a top that has fallen;

FIG. 19 is a side view showing an example of a conventional capillary for a wire bonding apparatus.

20A is a schematic cross-sectional view of the tip of the capillary shown in FIG. 19, and FIG. 20B is a cross-sectional view showing the shape of the tip of the capillary in more detail.

FIG. 21 is a side view showing another example of a conventional capillary for a wire bonding apparatus.

22A is a schematic cross-sectional view of the tip of the capillary shown in FIG. 21. FIG. 22B is a cross-sectional view showing the shape of the tip of the capillary in more detail.

FIGS. 23A to 23D are process diagrams schematically showing a conventional method of forming a two-stage bump by a ball bonding method using a capillary.

FIG. 24 is a side view showing the shape of a typical two-stage bump formed by a conventional ball bonding method.

FIG. 25 is a side view showing a leveling step by a conventional ball bonding method.

FIG. 26 is a side view showing a typical shape of a bump leveled by a conventional ball bonding method.

FIGS. 27A to 27C are side views each showing an undesired shape of a two-stage bump formed by a conventional ball bonding method.

FIGS. 28 (a) and (b) are side views showing a shape of a defective bump generated in a conventional leveling step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capillary 2 Wire lead-out hole 3 Projection 4 Metal wire 6 IC chip 7 Bump 8 Bump top 9 Bump bottom 11 Capillary face 13 Electrode pad 31 Lower end face of projection

Claims (5)

(57) [Claims] 1. A method of forming a bump on an electrode pad of a semiconductor device using a capillary for ball bonding, wherein a step of forming a tip portion of a metal wire into a ball shape (a).
And, the ball-shaped tip is pressed on the electrode pad,
A step (b) of forming a bottom of the bump, a step (c) of forming a top on the bottom, and a step of press-shaping and leveling the top with a leveling surface provided on a side surface of the capillary (d) ). 2. In the step (c), the capillary is
The metal wire moving in a loop-like trajectory above the bottom of the bump and forming the top of the bump is formed on the bottom in a ring or inverted U-shape.
3. The method for forming an electrical connection bump according to item 1. 3. A capillary for ball bonding for forming a bump on an electrode pad of a semiconductor device, wherein the capillary presses a ball-shaped tip of a metal wire against the electrode pad at its lowermost part. The ball-shaped tip has a pressing surface for pressing the electrode pad against the electrode pad, and a center portion of the pressing surface is provided with a lead-out hole for supplying the metal wire, and a side surface of the capillary is provided with the bumps. A leveling surface for pressing and shaping the top is provided, and the distance between the pressing surface and the leveling surface is
Capillary for wire bonding equipment with the same height as the bumps to be formed . 4. The capillary for a wire bonding apparatus according to claim 3 , wherein the leveling surface has an uneven surface. 5. The capillary for a wire bonding apparatus according to claim 3 , wherein the leveling surface has a guide portion formed to project downward.