JP2007027498A - Method for manufacturing a semiconductor device and manufacturing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device manufacturing method that eliminates the need for flattening by pressure, and equalizes the height of each metal bump formed on a semiconductor device. <P>SOLUTION: This method forms metal bumps on a semiconductor device electrode pad, raises a capillary to a given height, and then horizontally moves the capillary to cut a metal wire. Otherwise, this method moves a capillary up to a given height, moves the capillary horizontally, and then lowers it to cut a wire with the edge of the capillary while continuing to move it horizontally. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and apparatus for manufacturing a semiconductor device, for example, in which metal bump electrodes are formed by ball bumps on electrode pads formed on a semiconductor element.

  As a method of connecting a semiconductor element to a wiring pattern of a printed wiring board, a metal protruding electrode called a bump is formed on an electrode pad on the semiconductor element, and this protruding electrode is used to connect the electrode pad on the semiconductor element and the printed wiring board. In general, the wiring pattern is connected and mounted by heating and pressing.

Hereinafter, a method for forming metal bumps by a general ball bonding method will be described with reference to the drawings.
First, an apparatus for forming metal bumps is shown in FIG.
This apparatus includes a capillary 1, a clamper 2, and a torch electrode 3.
The capillary 1 is provided with a pore 1a passing through the center portion up and down. The tip 1b of the capillary 1 is formed with an opening that communicates with the pore 1a and whose inner diameter increases toward the tip. Further, the capillary 1 can be arbitrarily moved by a drive system (not shown).
The clamper 2 is provided in the upper part of the capillary 1 and holds the metal wire 4 passed through the pore 1a of the capillary 1. The clamper 2 can also be moved in an arbitrary direction by a drive system (not shown). It has a possible configuration.
The torch electrode 3 heats and melts the metal wire 4 to form a metal ball 5 (see FIG. 15) to be a bump. The metal wire 4 passes through the pore 1a of the capillary 1 and is drawn from the tip 1b and is continuously supplied from above the capillary 1 as appropriate.

Then, using the apparatus shown in FIG. 13, metal bumps are formed as follows.
As shown in FIG. 14, with the clamper 2 closed and holding the metal wire 4, the capillary 1 and the clamper 2 are lowered to bring the tip of the metal wire 4 closer to the torch electrode 3. Then, the spark 17 emitted from the torch electrode 3 is discharged toward the metal wire 4. Thereby, the tip of the metal wire 4 is heated and melted.

  Next, by stopping the spark from the torch electrode 3 and naturally cooling, a recrystallized region 15 is formed at the tip of the melted metal wire 4 as shown in FIG. The recrystallized region 15 includes a metal ball 5 that has become spherical due to surface tension after a part of the metal wire 4 is melted by the spark 17, and a wire that is not formed into a ball and is connected to the connection portion between the metal ball 5 and the metal wire 4. It is comprised by the neck part 6 recrystallized with the shape. The neck portion 6 formed by recrystallization after melting has a brittle property and can be easily cut.

  Next, as shown in FIG. 16, the capillary 1 and the clamper 2 are moved above the electrode pads 8 on which the metal bumps are mounted. The electrode pad 8 is provided on the semiconductor element 7, and the semiconductor element 7 is installed on a stage 10 to which a heating device is attached.

  Next, as shown in FIG. 17, after opening the clamper 2, the capillary 1 is lowered. The metal ball 5 is pressed against the electrode pad 8 from above by the tip 1b of the capillary 1. At the same time, ultrasonic waves are applied from an ultrasonic transducer attached to the capillary 1 and heat is applied from the heating device of the stage 10 on the semiconductor element 7 side. Thereby, the metal ball 5 is mounted on the electrode pad 8 and the metal bump 9 is formed.

  Next, as shown in FIG. 18, the capillary 1 is raised vertically to an arbitrary height while the clamper 2 is opened.

  Next, as shown in FIG. 19, after the clamper 2 is closed and the metal wire is held and fixed, the capillary 1 and the clamper 2 are raised. Then, the metal wire 4 is cut at the neck portion 6 by the tension of the metal wire 4.

  By the above method, the metal bumps 9 are formed on the electrode pads 8 provided on the semiconductor element 7 by the ball bonding method. By repeating this process in sequence, a large number of metal bumps can be formed continuously.

  FIG. 22 shows a state in which the semiconductor element 7 and the printed wiring board 11 are connected. A wiring pattern 12 formed on the surface of the printed wiring board 11 and an electrode pad 8 provided on the semiconductor element 7 are electrically connected through metal bumps 9. The semiconductor element 7 is electrically connected by flip-chip mounting on the wiring board 11 so that the metal bumps 9 and the electrodes 12 on the wiring board 11 are connected.

In this case, in order to correctly connect the semiconductor element 7 and the electrode on the printed wiring board 11, it is desirable that the metal bumps 9 on the semiconductor element 7 have a uniform height, as shown in FIG. 22A. On the other hand, as shown in FIG. 22B, if the heights of the bumps 9 formed on the electrodes 8 of the semiconductor element 7 are different, there is a problem that connection failure occurs in some electrodes.
In addition to this, if the metal bump falls down, the position of the contact surface with the wiring board may shift, and if the recrystallization region of the neck portion 6 is insufficient when torn, the gold wire 4 will be impossible. As a result, the height of the metal bump 9 after the tearing is different, and there is a problem that a defect in appearance occurs in most of the manufactured semiconductor devices.

  However, since the temperature of the spark 17 discharged from the torch electrode 3 shown in FIG. 14 is not constant, the amount of heat transferred to the tip of the metal wire 4 is not constant. Therefore, as shown in FIG. 20, the recrystallized region 15 has a different size due to the influence of the temperature of the spark 17 being different. In particular, in the neck portion 6 formed at the tip of the metal wire 4, the range of the region to be recrystallized after melting is greatly different.

  Therefore, as shown in FIG. 21, when the metal wire 4 is cut by tension after the metal bump 9 is formed, the cut portion of the metal wire 4 is different, and the length of the neck portion 6 on the metal bump 9 is different. . Therefore, a difference occurs in the height of the metal bump 9.

Therefore, bump flattening is performed to make the bump height uniform after bump formation.
For example, as shown in FIG. 23A, there is a semiconductor element 7 in which a plurality of metal bumps 9 having neck portions 6 having different lengths are formed on an electrode pad 8. In the case of bump flattening, as shown in FIG. 23B, the semiconductor element 7 is placed on the semiconductor element cradle 14 and a plurality of metal bumps 9 formed on the semiconductor element 7 are placed on a load member having a pressing surface. 13 to make the metal bumps 9 uniform in height. With such a bump flattening apparatus, as shown in FIG. 23C, the heights of the plurality of metal bumps 9 formed on the semiconductor element 7 can be aligned in a good shape.

In addition, as another method for making the height of the metal bump uniform, there is a method of applying ultrasonic waves of a resonance frequency from the capillary to the metal wire when the metal wire at the time of forming the metal bump is cut from the metal bump. Thereby, the length of the metal wire remaining on the upper part of the metal bump is made uniform and cut, and the height of the metal bump is made uniform (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-144820

  However, in the method of flattening by pressing the bumps, it is necessary to perform bump flattening for flattening after the wafer is cut for each semiconductor element. That is, after bumps are formed in a wafer state, they are separated into individual semiconductor elements and bump flattened. In this case, the whole process increases and becomes complicated, the semiconductor production time is long, and the mass productivity is inferior. This also affects production costs.

  In addition, due to the increase in the number of pins of semiconductor elements, there are a large number of semiconductor elements exceeding 300 pins in one chip. In the case of semiconductor elements with multiple pins, a considerable weight is applied when performing collective flattening on these metal bumps. May be transmitted to the joint and cracks may occur in the joint.

  Here, a technique of enlarging the pressing surface of the pressing member and flattening the entire wafer is conceivable. However, there are a large number of gold bumps formed on the entire wafer, and a very large load is required to press all of them. A flattening apparatus having such an apparatus becomes large and expensive, and is not realistic.

  In order to solve these problems, the present invention does not require bump flattening or the like when forming metal bumps on electrode pads on a semiconductor element, and forms metal bumps on a semiconductor element at a uniform height. Provided are a semiconductor device manufacturing method and a semiconductor device manufacturing apparatus.

  According to the method of manufacturing a semiconductor device of the present invention, a metal wire is protruded from the tip end portion of the capillary through the pore of the capillary, a metal ball is formed at the tip end portion of the wire, and the capillary is placed on the electrode pad. After the metal balls are lowered and attached to the electrode pads to form metal bumps, the capillaries are raised and separated from the metal bumps, and the capillaries are moved horizontally with respect to the electrode pads. Then, the metal wire is cut from the metal bump.

  According to the semiconductor device manufacturing method of the present invention described above, in cutting the metal wire, the capillary is moved in the horizontal direction so that the metal wire is not forcibly torn off during the cutting. For this reason, the remainder of the metal wire extended upwards of a metal bump can be suppressed.

  Further, in the method for manufacturing a semiconductor device of the present invention, a metal wire is protruded from the tip end portion of the capillary through the pore of the capillary, a metal ball is formed at the tip end portion of the wire, and the capillary is connected to the electrode pad. The metal ball is attached to the electrode pad to form a metal bump, and then the capillary is raised and separated from the metal bump. Further, the capillary is horizontally oriented with respect to the electrode pad. Further, the capillary is lowered while being moved in the horizontal direction with respect to the electrode pad, and the metal wire is cut from the metal bump.

  According to the semiconductor device manufacturing method of the present invention described above, the capillary is moved in the horizontal direction and further lowered while moving the capillary in the horizontal direction, so that excessive tensile stress is not applied during cutting. For this reason, deformation of the metal wire can be prevented, wire bonding with good straightness can be performed, and contact between adjacent terminals due to the remainder of the metal wire can be prevented. In addition, since no metal wire remains, the height of the metal bumps can be kept low.

  In addition, since the metal wire is stably cut at the cracked portion, the length of the wire lead protruding from the tip of the capillary after cutting becomes substantially constant. For this reason, since the size of the metal ball formed at the tip of the metal wire is stabilized, bonding can be performed stably.

  The semiconductor device manufacturing apparatus of the present invention includes a capillary having a pore, means for holding a metal wire passing through the pore, and means for moving the capillary vertically or horizontally, A circumferential portion is provided on the outer edge of the tip of the capillary.

  According to the above-described semiconductor device manufacturing apparatus of the present invention, the circumferential portion is provided at the tip of the capillary, so that the metal wire recrystallized after melting is adapted to the metal bump main body, and the metal from the neck portion. It becomes possible to easily cut the wire.

  According to the present invention, when forming a metal bump on an electrode pad on a semiconductor element, it is possible to form a metal bump having a uniform height without requiring flattening by pressurization.

A first embodiment of the present invention will be described with reference to the drawings.
First, an apparatus for forming metal bumps is shown in FIG.
This apparatus includes a capillary 1, a clamper 2, and a torch electrode 3.
The capillary 1 is provided with a pore 1a passing through the center portion up and down. The tip 1b of the capillary 1 is formed with an opening that communicates with the pore 1a and whose inner diameter increases toward the tip. Further, the capillary 1 can be arbitrarily moved by a drive system (not shown).
The clamper 2 is provided on the top of the capillary 1 and holds a metal wire 4 suitable for the pore 1a of the capillary 1. The clamper 2 can also be moved in an arbitrary direction by a drive system (not shown). It has a possible configuration.
The torch electrode 3 heats and melts the metal wire 4 to form a metal ball 5 (see FIG. 2) to be a bump. The metal wire 4 passes through the pore 1a of the capillary 1 and is drawn from the tip 1b and is continuously supplied from above the capillary 1 as appropriate.

  As the metal wire 4, a metal excellent in ductility and conductivity, for example, 99% or more of gold can be used. Further, the thickness of the metal wire 4 is, for example, 25 μm in diameter.

Then, using the apparatus shown in FIG. 1, metal bumps are formed as follows.
As shown in FIG. 2, in a state where the clamper 2 is closed and the metal wire 4 is held, the capillary 1 and the clamper 2 are lowered to bring the tip of the metal wire 4 closer to the torch electrode 3. Then, the spark 17 emitted from the torch electrode 3 is discharged toward the metal wire 4. Thereby, the tip of the metal wire 4 is heated and melted.

  Next, by stopping the spark from the torch electrode 3 and naturally cooling, a recrystallization region 15 is formed at the tip of the molten metal wire 4 as shown in FIG. The recrystallized region 15 includes a metal ball 5 that has become spherical due to surface tension after a part of the metal wire 4 is melted by the spark 17, and a wire that is not formed into a ball and is connected to the connection portion between the metal ball 5 and the metal wire 4. It is comprised by the neck part 6 recrystallized with the shape. The neck portion 6 formed by recrystallization after melting has a brittle property and can be easily cut.

  Next, as shown in FIG. 4, the capillary 1 and the clamper 2 are moved above the electrode pads 8 on which the metal bumps are mounted. The electrode pad 8 is provided on the semiconductor element 7, and the semiconductor element 7 is installed on a stage 10 to which a heating device is attached. The electrode pad 8 is made of aluminum or copper, and the surface of the semiconductor element 7 other than the portion where the electrode pad 8 is formed is covered with a protective film.

  Next, as shown in FIG. 5, after opening the clamper 2, the capillary 1 is lowered. The metal ball 5 is pressed against the electrode pad 8 from above by the tip 1b of the capillary 1. At the same time, ultrasonic waves are applied from an ultrasonic transducer attached to the capillary 1 and heat is applied from the heating device of the stage 10 on the semiconductor element 7 side. Thereby, the metal ball 5 is mounted on the electrode pad 8 and the metal bump 9 is formed.

  Next, as shown in FIG. 6, the capillary 1 is raised vertically to an arbitrary height while the clamper 2 is opened.

  Next, as shown in FIG. 7, after closing the clamper 2, the capillary 1 and the clamper 2 are moved horizontally. Due to the movement of the capillary 1, the protrusion on the upper part of the metal bump and the metal wire 4 are stretched laterally by the tip 1 b of the capillary 1.

  Next, as shown in FIG. 8, the recrystallization region 15 is cut from the metal wire 4 by the tension between the tip 1 b of the capillary and the metal wire 4. At this time, application of ultrasonic waves or the like is not performed.

  By the above method, the metal bumps 9 are formed on the electrode pads 8 provided on the semiconductor element 7 by the ball bonding method. By repeating this process in sequence, a large number of metal bumps can be formed continuously.

  According to the first embodiment, when the metal wire 4 is cut, the metal wire 4 is not pulled upward, so that the neck portion 6 does not extend on the metal bump 9. Further, by moving the tip 1b of the capillary 1 horizontally from the neck of the metal bump 9, the metal wire 4 is cut so as to scratch the surface of the metal bump 9 with the tip 1b. Therefore, the metal bump 9 having a stable size can be formed without being affected by the size of the recrystallized region 15 and the length of the neck portion 6, and the surface is shaved to make the height constant.

  At this time, for example, when the height of the metal bump 9 is designed to be 50 μm, the height of the tip 1b of the capillary 1 is set to 50 μm from the upper surface of the electrode pad 8, and the height is maintained and this is moved in the horizontal direction. By doing so, the metal wire 4 can be cut | disconnected and the metal bump 9 of the target height can be formed.

A second embodiment of the present invention will be described with reference to the drawings.
Each process shown in FIGS. 1 to 6 is the same as that of the first embodiment.
From the state shown in FIG. 6, as shown in FIG. 9, the capillary 1 is moved in the horizontal direction to an arbitrary position. At this time, the clamper 2 remains open and no ultrasonic wave is applied. Although the clamper 2 shown in FIG. 9 is open, the clamper 2 can be opened or closed, and the metal wire may be broken by the movement of the capillary 1. Therefore, the clamper 2 is preferably open. .

Next, as shown in FIG. 10, after closing the clamper 2, the capillary 1 is lowered while moving in the horizontal direction, and the metal wire 4 is cut at the tip of the capillary 1. At this time, by closing the clamper 4, the metal wire 4 can be prevented from falling off from the capillary 1.
At this time, the protrusions on the upper part of the metal bumps 9 and the metal wires 4 stretched in the horizontal direction in FIG. 9 are crushed between the tip part 1 b of the capillary 1 and the metal bumps 9 as the capillary 1 descends. Further, the metal wire 4 is cut by the stress generated at that time.

Also according to the second embodiment, as in the first embodiment, when the metal wire 4 is cut, the metal wire 4 is not pulled upward, so that the neck portion 6 extends on the metal bump 9. Absent. Further, the surface is shaved and the height is constant without being affected by the size of the recrystallized region 15 and the length of the neck portion 6, and a metal bump having a stable size can be formed.
Furthermore, in the second embodiment, the tip 1b of the capillary 1 is lowered while being moved in the horizontal direction, and the metal wire 4 is cut so as to be crushed between the tip of the capillary 1 and the metal bump 9. The metal wire 4 can be easily cut, and the metal bump 9 having a more stable size than that of the first embodiment can be formed.
At this time, for example, when the height of the metal bump 9 is designed to be 50 μm, the height of the tip 1b of the capillary 1 is set to 50 μm from the upper surface of the electrode pad 8, and the height is maintained and this is moved in the horizontal direction. Further, the metal wire 4 can be cut by being lowered while being moved in the horizontal direction, and the metal bump 9 having a target height can be formed.

  In the present embodiment, more preferably, the shape of the tip 1b of the capillary 1 is made different from the conventional one. The difference between the tip 1b of the capillary 1 of the present invention and the tip 1b of the conventional capillary 1 will be described in comparison with the drawings.

  FIG. 11 is a diagram showing a schematic structural comparison between the conventional capillary and the capillary of the present embodiment. The conventional capillary 1 shown in FIG. 11A is not provided with a circumferential portion at the outer edge of the tip 1b of the capillary 1, whereas the capillary 1 of the present embodiment shown in FIG. A circumferential portion 16 is provided on the outer edge of 1b.

  When the circumferential portion 16 is not provided on the outer edge of the capillary tip 1b, the melted and recrystallized metal wire 4 does not conform to the metal bump 9 body, and the frictional resistance is large, so that the shape of the metal bump 9 after cutting is considered. It ’s not good. Therefore, in order to cut the metal wire 4 from the metal bump 9 satisfactorily, the angle of the circumferential portion 16 at the outer edge of the capillary tip 1b is increased. As a result, the melted and recrystallized metal wire is well adapted to the metal bump body and the frictional resistance is reduced, so that the shape of the metal bump 9 after cutting is improved.

At this time, the angle of the circumferential portion 16 at the outer edge of the tip 1b of the capillary 1 is preferably 20 degrees or more. When the angle is less than 20 degrees, the melted and recrystallized metal wire 4 and the metal bump 9 are not easily adapted to each other, so that the frictional resistance is large and the metal wire 4 is difficult to cut. When the angle of the circumferential portion 16 is 20 degrees or more, the metal wire 4 and the metal bump 9 which are melted and recrystallized are well adapted to each other, and the frictional resistance is reduced, so that the metal wire 4 is cut well.
Moreover, this circumference part may be comprised not only with a single curved surface but with several curved surfaces, and can be selected according to the shape of the target cutting | disconnection.

FIG. 12 is an enlarged photomicrograph comparing the shapes of metal bumps formed on electrode pads in the conventional and the present embodiment.
The micrograph shown in FIG. 12A is a metal bump formed by a conventional method, and the micrograph shown in FIG. 12B is a metal bump formed by the manufacturing method of the second embodiment of the present invention.
In the metal bump formed by the method of the present invention, the upper portion of the metal bump 9 is crushed and cut by the tip 1b of the capillary 1, so that an extra metal wire is formed on the metal bump, such as a conventional metal bump. It was possible to form metal bumps that were stable and uniform in height.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

It is a figure which shows the structure of the manufacturing apparatus for forming a general metal bump. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 1st embodiment of this invention. It is a figure explaining 2nd embodiment of this invention. It is a figure explaining 2nd embodiment of this invention. FIG. 11A is a diagram showing a conventional capillary, and FIG. 11B is a diagram showing the structure of the capillary according to the present embodiment. 12A is a conventional metal bump, and FIG. 12B is a micrograph of the metal bump of the present embodiment. It is a figure which shows the structure of the manufacturing apparatus for forming a general metal bump. It is a figure explaining the formation method of the conventional metal bump. It is a figure explaining the formation method of the conventional metal bump. It is a figure explaining the formation method of the conventional metal bump. It is a figure explaining the formation method of the conventional metal bump. It is a figure explaining the formation method of the conventional metal bump. It is a figure explaining the formation method of the conventional metal bump. It is a figure which shows the area | region of the metal ball and neck part of the recrystallization area | region after a fusion | melting. It is a figure which shows the difference in the height of the metal bump which cut | disconnected the metal wire with tension | tensile_strength. It is a figure which shows a mode that the A and B semiconductor element and the printed wiring board were electrically connected by the metal bump. It is a figure which shows the flattening of the semiconductor element in which AC metal bump was formed.

Explanation of symbols

  1 capillary, 1a pore, 1b tip, 2 clamper, 3 torch electrode, 4 metal wire, 5 metal ball, 6 neck, 7 semiconductor element, 8 electrode pad, 9 metal bump, 10 stage, 11 printed wiring board, 12 wiring pattern, 13 placement, 14 semiconductor element cradle, 15 recrystallization region, 16 circumference of capillary tip, 17 spark

Claims (8)

A metal wire is projected from the tip of the capillary through the capillary pore,
Forming a metal ball at the tip of the metal wire;
After forming the metal bump by lowering the capillary onto the electrode pad and attaching the metal ball to the electrode pad,
Raise the capillary away from the metal bumps,
Furthermore, the said capillary is moved to a horizontal direction with respect to the said electrode pad, and the said metal wire is cut | disconnected from the said metal bump. The manufacturing method of the semiconductor device characterized by the above-mentioned. A metal wire is projected from the tip of the capillary through the capillary pore,
Forming a metal ball at the tip of the metal wire;
After forming the metal bump by lowering the capillary onto the electrode pad and attaching the metal ball to the electrode pad,
Raise the capillary away from the metal bumps,
Moving the capillary horizontally with respect to the electrode pad;
Furthermore, the capillary is lowered while being moved in the horizontal direction with respect to the electrode pad, and the metal wire is cut from the metal bump.   2. The method of manufacturing a semiconductor device according to claim 1, wherein gold having a purity of 99% or more is used as a material of the metal wire.   The method of manufacturing a semiconductor device according to claim 2, wherein gold having a purity of 99% or more is used as a material of the metal wire.   2. The method of manufacturing a semiconductor device according to claim 1, wherein a capillary having a circumferential portion provided on an outer edge of a tip portion is used as the capillary.   3. The method of manufacturing a semiconductor device according to claim 2, wherein a capillary having a circumferential portion provided at an outer edge of a tip portion is used as the capillary. A capillary having pores;
Means for holding the metal wire through the pore;
Means for moving the capillary up and down or horizontally,
An apparatus for manufacturing a semiconductor device, characterized in that a circumferential portion is provided on an outer edge of the tip of the capillary.   The semiconductor device manufacturing apparatus according to claim 7, wherein the circumferential portion is formed at an angle of 20 degrees or more.