JPH104096A - Bump structure and bump forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the yield and reduce the number of working steps by preventing cut pieces of a metal wire from remaining during forming of bumps on pads of a semiconductor device, using a bonder. SOLUTION: The bump structure 20 is mounted on an electrode pad 2 formed on a semiconductor substrate 1 and has a cross section approximately symmetric to the vertical center axis L, approximately flat top face 17, bottom face 18 connected to the pad 2 and barrel 19 bulging from the top face 17 to the bottom face 18. The barrel 19 has a pressed recess 16 formed by butting the top end of a capillary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bump structure and a bump forming method for a semiconductor device, and more particularly, to a method for mounting a semiconductor element on an electrode pad having a fine pitch provided on a semiconductor substrate. The present invention relates to a method for forming a bump and a bump structure obtained by the method.

[0002]

2. Description of the Related Art Conventionally, many kinds of bump forming methods of this kind have been proposed, and they are generally formed by an electroplating method, an etching method, a thermal transfer method, or the like. However, in such a method,
In addition to requiring dedicated equipment such as plating and etching, it requires a large investment in equipment, and has the drawback that it is not suitable for small-lot production of other products.

[0005] Therefore, for the purpose of improving such a method, a method of forming a bump using a wire bonding apparatus has been proposed. A typical example of this method is disclosed in, for example, Japanese Patent Publication No. 4-41519. The outline of this method is as shown in FIGS. 3 (A) to 3 (E). As described above, the distal end of the metal wire 5 passed through the hole 4 for guiding the metal wire 5 of the bonding capillary (hereinafter simply referred to as a capillary) 3 is subjected to an electric discharge treatment by an electric torch, which is a known method, and is heated and melted. The ball 6 is formed.

Next, as shown in FIG. 3 (B), the capillary 3 is lowered and the ball 6 is pressed onto the electrode pad 2 provided on the semiconductor substrate 1, and in this state, the ball 6 Is subjected to ultrasonic vibration and heat treatment, and the ball 6 is thermocompression-bonded to the electrode pad 2 to form a ball 7 fixed to the electrode pad 2. Then, FIG.
As shown in FIG. 3 (C), after the capillary 3 is once pulled up slightly, the capillary 3 is moved laterally by a distance corresponding to the radius of the ball 7.

[0005] Thereafter, as shown in FIG. 3 (D), by pressing down the capillary 3 again, a strong load is applied to the metal wire 5 to form a fragile portion 14 such as a cutout portion. Then, as shown in FIG. 3 (E), the metal wire 5 and the capillary 3 are simultaneously pulled upward, so that the metal wire 5 is weakened by a weak portion 14 such as the above-described weakened cut portion. The bumps 8 are formed by being torn and cut.

However, in such a method, when the bumps are formed by moving the capillary 3 at a high speed,
Since the notched portion may not be formed stably, the uncut portion 25 occurs, so-called "whiskers" occur frequently, and there is a problem that the shape of the torn portion is not constant, and such a problem occurs. The reason for this is that if the capillary 3 is moved at a high speed by a predetermined amount and stopped, the overshoot occurs due to the variation due to the repetition accuracy of the apparatus and the inertia remaining at the tip of the capillary 3. It is considered that the stop position of the capillary does not become constant.

Therefore, when mounting and connecting the substrate and the semiconductor element, the heights of the bump structures are not uniform.
There was also a problem that another process such as leveling had to be adopted. Further, in the above method, it is necessary to press the capillary 3 against the metal ball in order to tear off the metal wire 5, so that the height of the finally formed bump 8 is reduced, and furthermore, the torso portion is reduced. By inflating,
When the bump structure 8 needs a certain height or when it is used for a semiconductor substrate having a narrow pitch electrode pad, it is not effective.

On the other hand, as a method for forming the above-mentioned cutout portion as stably as possible in the metal wire 5, for example, Japanese Patent Application No. 7-628 filed by the present applicant has filed.
As shown in No. 24, the tip of a conventionally used capillary 3 has a tapered or rounded R shape, whereas the capillary 3 has a shape as shown in FIG. The distal end face 9 of the capillary 3 is flattened, and the hole 4 of the capillary 3 for guiding the metal wire 5 and the edge 10 formed by the distal end face of the capillary 3 are processed into a right-angled sharp shape. I have.

Therefore, the notch can be formed in the metal wire 5 more stably by the capillary 3 than in the conventional capillary 3 described above.
It is possible to suppress the generation of the uncut portion, that is, the "whisker" portion. However, in the capillary 3 having such a structure,
Since the tapered portion or the R-shaped portion does not exist at the edge 10 of the hole 4 at the tip, the center of the capillary 3 and the center of the ball 6 are shifted when bonding to the electrode pad 2 of the semiconductor substrate 1. There was a problem of being bonded.

[0010] The cause is that if a hole formed at the tip of the capillary has a tapered portion or a rounded portion, the ball formed at the tip of the capillary is lowered to the pad of the semiconductor element. The position of the ball is determined by following the hole without difficulty, but in the above-described conventional method, since the tapered portion or the R-processed portion does not exist in the hole at the tip of the capillary, the ball is It is considered that a case may occur in which the tip is caught by the edge portion and does not enter the hole.

In addition, as another example of the conventional technique, a wire bonding technique of forming a bump structure through steps shown in FIGS. 5A to 5D is also known. . Such a technique is disclosed, for example, in Japanese Patent Publication No. 6-3820, in which a ball 6 is formed at the tip of the capillary 3 and the ball 6 is formed together with the capillary 3 in the same manner as in the conventional example described above. The ball 7 is pressed against the electrode pad 2 provided on the substrate 1 and fixed to the electrode pad 2 by ultrasonic vibration and thermocompression bonding. (FIG. 5
(See (A) and FIG. 5 (B).) Then, as shown in FIG. 5 (C), the capillary 3 is moved so as to draw a loop-like trajectory 12, that is, the upward, horizontal and downward movements are performed. Run continuously and finally Figure 5
As shown in (D), a part of the metal wire 5 is second-bonded near the upper side of the ball 7 so that the loop portion 13 is formed on the metal wire 5, and at the same time, the capillary 3 By pressing strongly again, the metal wire 5 is cut.

For this reason, as described above, since the bump at the portion where the capillary 3 contacts during the second bonding is greatly deformed, there is a problem that the method cannot cope with the formation of a fine pitch bump. In addition, since the entire bump is crushed and its height becomes too low, when mounting an appropriate semiconductor element on the semiconductor substrate, a connection failure or the like occurs, which causes a reduction in yield.

In the conventional method, the metal wire 5
Since the shape, length, and the like of the loop portion 13 cannot be substantially controlled, the length, height, and the like of the whisker-shaped portion become unstable, so that a leveling step is always required. . Another example in the prior art is disclosed in JP-A-3-14.
As disclosed in Japanese Patent Publication No. 235/235, after the ball is fixed on the electrode pad of the semiconductor element, the capillary is cut in the step of cutting the ball and the metal wire 5 as described in the above conventional example. The operation direction of No. 3 is appropriately changed for each electrode pad of the semiconductor element, and the metal wire on the ball is cut while being hammered in advance.

According to this method, even if there is an uncut wire above the bump, the wire can be tilted in the direction previously set in the subsequent bump leveling operation step. Can be prevented from contacting the bumps. However, in such a method, since the metal wire cannot be cut at a predetermined length, a relatively long uncut wire occurs.

Therefore, there is a problem that bumps cannot be formed on the fine pitch semiconductor elements arranged in a staggered manner. Further, it is necessary to set the moving direction of the capillary for each pad to be bonded. Since it is necessary to perform leveling after bump formation, there is also a problem that the number of steps increases.

[0016]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned drawbacks of the prior art, to eliminate the uncut residue of a metal wire when a bump is formed on a pad of a semiconductor device using a bonding apparatus, and to reduce the yield. It is an object of the present invention to provide a pump structure and a bump forming method capable of reducing the number of working steps while improving the structure.

[0017]

The present invention basically employs the following technical configuration in order to achieve the above object. That is, a first aspect of the present invention is a bump structure mounted on an electrode pad provided on a semiconductor substrate, the cross section of which is substantially symmetrical with respect to a vertical center axis. And has a substantially planar upper surface, a bottom surface connected to the pad, and a curved swelling body provided between the upper surface and the bottom surface. A bump structure in which a pressing portion formed in contact with the tip of the capillary portion is disposed on a part of the body portion, and as a second aspect according to the present invention, the bump structure is formed through a bonding capillary. The tip of the metal wire was melted by electric torch discharge,
Forming a ball of a predetermined size, lowering the bonding capillary, pressing the metal ball against an electrode pad of a semiconductor substrate, and fixing the metal ball to the electrode pad to form a bump; Moving the bonding capillary horizontally by a predetermined distance in a first direction, and moving the bonding capillary in a second direction opposite to the first direction.
And moving the metal wire away from the bump by raising the bonding capillary and moving the metal wire away from the bump by moving the bonding capillary upward and beyond the predetermined distance moved in the first direction. This is a bump formation method.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A bump structure and a bump forming method according to the present invention are directed to a capillary for passing a metal wire, a clamper for clamping the metal wire, a mechanism for moving these up and down, and a horn for transmitting ultrasonic vibrations to the capillary. Using an apparatus equipped with a bonding head comprising: an XY stage for moving the bonding head in the vertical and horizontal directions; and an electric torch for melting a metal wire at the tip of the capillary to form a ball. The unwound metal wire is melted by the discharge of an electric torch to form a ball, then the capillary is lowered together with the ball, and ultrasonic vibration is applied while pressing the electrode pad on the semiconductor substrate heated to a certain temperature. Then, a ball-shaped bump is formed on the electrode pad. Next, after the capillary is pulled up slightly with the metal wire opened, a first operation of horizontally or obliquely moving the capillary in a first direction, which is a predetermined direction, is performed.

Thereafter, the capillary is moved beyond the position where the first operation is started in a second direction which is a direction completely opposite to the first direction in the above-mentioned first operation. The second operation is executed. By performing the first and second operations, a connection portion between the ball and the metal wire is applied at least twice at the tip portion of the capillary, and a fragile portion such as deformation or cut is applied to the portion. Is formed.

Then, by pulling the capillary upward with the metal wire clamped, the metal wire is cut from the ball, and an ideal bump without so-called "whiskers" is formed. is there.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples of a bump structure and a bump forming method according to the present invention will be described in detail with reference to the drawings. That is, FIG. 1 shows a configuration of a specific example of a bump structure according to the present invention. In FIG. 1A (A), a bump structure mounted on an electrode pad 2 provided on a semiconductor substrate 1 is shown. 20, the cross section of which has a substantially symmetrical shape with respect to the vertical center axis L, and a substantially planar upper surface portion 17 and a bottom surface portion 18 connected to the pad 2 and the upper surface portion 17 A pressure portion formed in contact with the tip of the capillary portion at a part of the body portion 19; The bump structure 20 in which 16 is arranged is shown.

The upper surface portion 17 of the bump structure 20 according to the present invention is formed in a substantially horizontal shape, as shown in FIG.
As shown in the figure, the trace 2 of the wire cut is formed in the central portion of the upper surface portion 17 or in a region 21 close to the central portion.
Two are left. Further, the bump structure 2 according to the present invention
In the case of 0, the upper surface portion 17 may have a sliding mark indicating the sliding direction formed when the tip of the capillary portion comes into contact with the upper surface portion and slides. .

Next, a method of forming the bump structure 20 having the above configuration according to the present invention will be specifically described.
That is, in the bump forming method according to the present invention, as shown in FIGS. 2A to 2F, the tip of the metal wire 5 passed through the bonding capillary 3 is basically connected to an electric torch. A first step (FIG. 2 (A)) of melting by the electric discharge to form a ball 6 of a predetermined size, the bonding capillary 3 is lowered, and the metal ball 6 is moved to the electrode pad 2 of the semiconductor substrate 1. To form a bump 7 by adhering to the electrode pad, and then raise the capillary 3 upward by a certain distance in the same manner as in the related art to separate the capillary 3 from the newly formed ball 7. (FIG. 2B), a third step of horizontally moving the bonding capillary 3 by a predetermined distance d1 in the first direction D1 (FIG. 2C), and the bonding capillary 3 The first direction Moving the bonding capillary 3 horizontally in a second direction D2 opposite to 1 and by a distance d2 exceeding a predetermined distance d1 moved in the first direction (FIG. 2 (E)); A fourth step of raising the metal wire 5 and separating the metal wire 5 from the bump 7 (FIG. 2)
(F)).

In other words, the method for forming the bump structure 20 according to the present invention uses the ball 6 formed at the tip of the capillary 3.
Is pressed against the electrode pad 2 of the semiconductor substrate 1 and then the capillary 3 is swung right and left around the contact portion between the metal wire 5 and the ball 7, that is, the center of the ball 7 or its vicinity. Then, the capillary 3 is connected to the metal wire 5
And applying a physical load to the contact portion 24 between the ball 7 and
By actively forming a fragile portion including a deformation, a crack, or the like in the contact portion 24, the metal wire 5 can be moved to the ball 7 only by pulling the capillary upward.
Can be easily cut and separated.

Therefore, in the present invention, the occurrence of a "whisker" -shaped portion, which has been a problem in the prior art, is eliminated or extremely reduced, and a special operation in a post-process such as leveling is performed. Is not necessary, and when the capillary 3 presses and fixes the ball 6 to the electrode pad 2 or cuts the metal wire 5, it is not necessary to use a strong pressing force. The bumps 20 are not deformed, so that not only the height of the bumps 20 can be sufficiently maintained, but also the width of the bumps 20 can be controlled, so that mounting on the semiconductor substrate 1 using the narrow pitch electrode pads 2 is possible. It also functions effectively in operation.

In the present invention, in the first operation of the capillary 3 shown in FIG.
With the ball slightly lifted up from the ball 7, the first
Is shown, the rising distance is not specified, and in some cases, the tip of the capillary may slide in contact with the upper surface 17 of the ball 7. May be moved.

In such a case, the upper surface 1 of the bump 20
In many cases, a sliding trajectory formed when the capillary 3 slides on the upper surface portion 17 remains as a trace in 7. The movement of the capillary 3 in the first direction D1 in the first operation is, for example, movement from the center 21 of the upper surface 17 of the ball 7 in any of the radial directions. The movement distance is not particularly limited, but as an example, it is preferable that the movement distance be about half the diameter of the metal wire 5.

In the present invention, the capillary 3 is used.
The horizontal movement in the first operation may be in the horizontal direction as shown in FIG. 2C, but may move diagonally upward or diagonally downward as shown by the dotted line O or P. It may be something that causes. Next, the second operation of the capillary 3 according to the present invention will be described. In the second operation, the capillary has completed its first operation and has stopped. From the position, horizontally in a second direction D2 opposite to the first direction D1, and by a distance d2 exceeding a predetermined distance d1 moved in the first direction. The center of the capillary 3 is
It is desirable to pass through the central portion 21 of the hologram.

That is, the bonding capillary 3 is
The movement is further continued after passing through the position 21 where the movement has started in the first direction D1. Although the moving distance of the capillary 3 in the second operation is not particularly limited, it is preferable to use the diameter of the metal wire 5 as an example, for example.

In the present invention, the capillary 3 is used.
The horizontal movement in the second operation may be in the horizontal direction as shown in FIG. 2 (E), but may be diagonally upward or diagonally downward as indicated by the dotted line O ′ or P ′. May be moved. Also in such a case, the capillary 3 may move in contact with the upper surface portion 17 of the ball 7 or may move slightly away from the ball 7 in the first operation described above. Is the same as

Therefore, also in the second operation, the sliding trajectory formed when the capillary 3 slides on the upper surface 17 in the opposite direction is formed on the upper surface 17 of the bump 20. Often remains as traces. That is, at least one sliding locus formed when the capillary 3 moves in a different direction exists on the upper surface portion 17 of the bump structure 20 according to the present invention.

In the present invention, as described above, a physical load is applied to the metal wire 5 from two directions, and the metal wire 5 and the ball 7 are opposed to each other at the contact portion 24 between the metal wire 5 and the ball 7. Since the fragile portion 14 described above is formed on the surface, the metal wire 5 is reliably separated and cut at the substantially central portion 21 of the ball 7 or a region in the vicinity thereof. As a result, the size of the cut trace remaining when the metal wire 5 is cut becomes extremely small.

In the present invention, as shown in FIG. 2B, when the capillary 3 presses and fixes the ball 6 on the electrode pad 2, the ball 6 is pressed from above with a predetermined pressure. Other than the above, in each of the subsequent steps, the capillary 3
Does not press the ball 7, so that the outer surface of the bump 20, particularly the body 19, has a substantially symmetrical cross section with respect to the vertical center axis L, and the tip of the capillary portion is The pressing portion 16 formed at the time of pressing contact remains as it is.

Further, another embodiment of the bump forming method according to the present invention will be described. The tip of a metal wire passed through a bonding capillary is melted by electric discharge of an electric torch to form a ball having a predetermined size. In the first step, the bonding capillary is lowered, the metal ball is pressed against the electrode pad of the semiconductor substrate, and fixed to the electrode pad to form a bump. Then, the capillary 3 is moved at a predetermined distance. A second step of separating the capillary 3 and the newly formed ball 7 by raising the
A second 'step of raising the capillary 3 to an upper position some distance from the contact portion between the metal wire 5 and the ball 7; and bonding the capillary 3 to the bonding capillary 3 in the same manner as in the specific example described above. Capillary 3
A third step (FIG. 2C) of moving the bonding capillary 3 horizontally by a predetermined distance d1 in the first direction D1 and lowering the bonding capillary 3 again so that the upper end of the ball 7 In the third step (FIG. 2D) of lowering the bonding capillary 3 to a position where the bonding capillary 17 can contact the bonding direction, the bonding capillary 3 is moved horizontally in the second direction D2 opposite to the first direction D1, and The predetermined distance d moved in the direction of 1.
Step of moving by a distance d2 exceeding 1 (FIG. 2)
(E)) and raising the bonding capillary 3 to separate the metal wire 5 from the bump 7.
(FIG. 2F).

That is, in the present embodiment, the capillary 3 is moved up and down more aggressively when moving the capillary 3 left and right as compared with the first embodiment, thereby further improving the metal wire. The weak portion 14 is formed by applying a strong load to the joint between the bump 5 and the upper surface 17 of the bump 20. The conditions of the second specific example are substantially the same as those of the first specific example.

More specific examples of the bump structure and the bump forming method according to the present invention will be described below. That is, the pitch between the bump structures 20 formed on the electrode pads 2 of the semiconductor substrate 1 used in the present invention is, for example, 120
In the case of a micron, the capillary 3 has a passage hole 4 of the metal wire 5 having a tip portion of 33 microns and a diameter of the metal wire 5 of 25 to 7 to 65 to 7.
A ball 6 having a diameter of 0 micron is formed.

Ultrasonic thermocompression bonding is performed on the electrode pad 2 while pressing the ball 6 at a predetermined pressure by the capillary 3. At this time, the ball 7 is slightly crushed and
Is about 35 microns, and the bump diameter is about 80 microns. After that, the capillary 3 is moved 1 from that position.
Pull up about 00 micron and move horizontally 20 to 1 in the first direction.
Move about 30 microns, and at that position,
About 80 microns.

Next, the capillary 3 is moved through the center of the bump 20 in a second direction opposite to the first direction, and is moved to a position approximately 20 to 30 microns apart from the center of the bump 20 horizontally. Move. In this manner, a bump 20 having a bump diameter of about 80 microns, a pedestal height, that is, a height of about 35 microns to the pressing portion 16 in FIG. 1 and a height of about 50 microns to the upper surface of the bump is formed. It is done.

[0039]

In the bump structure and the bump forming method according to the present invention, even if the variation in the repetition accuracy of the bump forming apparatus or the overshoot of the capillary occurs,
Since a weakly fragile deformable portion is surely formed on the upper portion of the bump, the bump can be surely formed at a high speed, thereby improving workability.

In the present invention, it is not necessary to cut the metal wire by providing a notch to the metal wire at the sharp edge of the capillary tip, and the tip of the capillary is tapered. Alternatively, since the R processing is performed, even if a bump is formed at a high speed, it is possible to perform a different bonding that is shifted to a predetermined position, so that the shape of the bump structure is stabilized and its quality is improved.

Also, in the present invention, the joint between the metal wire and the bump can be weakened in the vicinity of the upper surface of the bump without strongly pressing the metal wire from above the bump with a capillary. And the height of the entire bump can be made high and uniform, so that connection failures in the mounted product can be reduced and the reliability of the final product can be improved.

Further, in the present invention, as described above,
The metal wire can be reliably cut at a fixed position on the top surface of the bump, and the height variation and the remaining metal wire can be eliminated, eliminating the need for leveling work after bump formation, reducing the number of work steps As a result, the production cost can be reduced.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view schematically showing a structure of a specific example of a bump structure according to the present invention.
FIG. 2B is a plan view of the bump structure in FIG.

FIGS. 2A to 2F are cross-sectional views schematically illustrating operations in respective steps in first and second specific examples of the bump forming method according to the present invention. is there.

FIGS. 3A to 3E are cross-sectional views illustrating an example of a conventional bump forming method.

FIG. 4 is a cross-sectional view showing a configuration example of a capillary used in a conventional bump forming method.

5 (A) to 5 (D) are cross-sectional views illustrating an example of a conventional bump forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate 2 ... Electrode pad 3 ... Bonding capillary 4 ... Metal wire through-hole 5 ... Metal wire 6, 7 ... Ball 9 ... Capillary tip part 10 ... Capillary edge part 12 ... Capillary movement locus 13 ... Loop part 14 ... Vulnerability Part 16 ... Pressing part (pedestal part) 17 ... Top part 18 ... Bottom part 19 ... Body part 20 ... Bump structure 21 ... Bump center part and its vicinity 22 ... Metal wire cutting trace part 25 ... Remaining cut part, whisker part

Claims (10)

[Claims] 1. A bump structure mounted on an electrode pad provided on a semiconductor substrate, the cross section of which has a substantially symmetrical shape with respect to a vertical center axis, and a substantially planar upper surface. A bottom portion connected to the pad and the pad and a torso swelling in a curved shape provided from the upper surface to the bottom portion, and a part of the torso, A bump structure wherein a pressing portion formed in contact with a tip of a capillary portion is arranged. 2. The method according to claim 1, wherein the upper surface portion is formed in a substantially horizontal shape, and a trace of the wire being cut is left in a central portion of the upper surface portion or a region close to the central portion. The bump structure according to claim 1, wherein 3. A sliding mark indicating a sliding direction, which is formed when the tip of the capillary portion slides by contacting the upper surface portion, is formed on the upper surface portion. The bump structure according to claim 1. 4. Melting the tip of a metal wire passed through a bonding capillary by electric torch discharge,
Forming a ball of a predetermined size, lowering the bonding capillary, pressing the metal ball against an electrode pad of a semiconductor substrate, and fixing the metal ball to the electrode pad to form a bump; Moving the bonding capillary horizontally by a predetermined distance in a first direction, and moving the bonding capillary in a second direction opposite to the first direction.
And moving the metal wire from the bump by raising the bonding capillary and moving the metal wire away from the bump by moving the bonding capillary upward and beyond the predetermined distance moved in the first direction. A bump forming method characterized in that: 5. The method according to claim 1, wherein the tip of the metal wire passed through the bonding capillary is melted by electric discharge of an electric torch.
Forming a ball of a predetermined size, lowering the bonding capillary, pressing the metal ball against an electrode pad of a semiconductor substrate, and fixing the metal ball to the electrode pad to form a bump; Ascending, moving the bonding capillary horizontally in a first direction by a predetermined distance, lowering the bonding capillary again, and moving the bonding capillary horizontally in a second direction opposite to the first direction. And a step of moving the bonding capillary again by a distance exceeding a predetermined distance moved in the first direction, and separating the metal wire from the bump by raising the bonding capillary again. Bump forming method. 6. In the step of moving the bonding capillary in the first direction, the bonding capillary is moved a predetermined distance from a movement start position in the first direction, and then moved in the first direction. 5. The method according to claim 4, wherein, when the bonding capillary is moved in the second direction, which is the opposite direction to the first direction, the bonding capillary passes through the position where the movement started in the first direction and further continues the movement. Or the bump forming method according to 5. 7. The bump forming method according to claim 4, wherein the movement start position of the bonding capillary coincides with the center of the ball. 8. The moving distance of the bonding capillary in the first direction is at least a distance corresponding to a half of the diameter of the metal wire.
8. The bump forming method according to any one of claims 1 to 7. 9. A moving distance of the bonding capillary in the second direction is at least a distance corresponding to a diameter of the metal wire.
The bump forming method according to any one of the above. 10. The method according to claim 1, wherein when the bonding capillary is moved in the second direction, the bonding capillary is moved obliquely upward or downward along the second direction. 10. The bump forming method according to any one of 4 to 9.