JP5062763B2 - Fine metal bump forming apparatus and forming method - Google Patents

Description

  The present invention relates to a fine metal bump forming apparatus and method, and more particularly to a fine metal bump forming method for forming a fine cone-shaped metal bump at a predetermined location of a metal wiring formed on one surface of a substrate.

Conventionally, in an electronic component such as a MEMS (Micro Electro Mechanical Systems) device, each end of a copper wiring pattern formed on one surface of a substrate made of resin, ceramic, or the like is used for flip chip connection with other electronic components. Metal bumps are used.
As a conventional metal bump, for example, a spherical so-called solder bump 51 shown in FIG. 7A is used. However, when this solder bump 51 is used, since the solder melting point is a high temperature close to 200 ° C., thermal damage to the chip occurs, or when connected via the solder bump 51, they are adjacent as shown in the figure. There was a possibility that the bumps would come into contact with each other, resulting in a short circuit state. Furthermore, in forming the solder bump 51, there is a problem that it is difficult to reduce the size.

  In addition to the solder bumps, columnar bumps 52 as shown in FIG. 7B are also used. However, in the case of the columnar bumps 52, if all the bump heights are not matched, some bumps are subjected to high-load bonding, resulting in mechanical damage to the chip or poor connection due to poor connection. There was a problem.

In recent years, as shown in FIG. 8A, a tapered metal bump (hereinafter referred to as a cone-shaped bump 30) has attracted attention for such a problem.
When this conical bump 30 is used, even if there is a variation in bump height, the tip of the bump is liable to be crushed at the time of bonding. Therefore, in the bonding state shown in FIG. can do. Furthermore, low-temperature / low-load bonding is possible with respect to the chip, and even when the pitch is narrow, the bumps do not swell greatly during bonding, so that a short circuit can be prevented from occurring.

  By the way, the applicant of the present application uses a gas deposition method (GD method), and a fine metal that can stably and industrially form a fine cone-shaped bump at a predetermined portion of a metal member formed on one side of a substrate. A method of forming bumps is disclosed in Patent Document 1. The GD method is a vapor deposition technique in which a sample is evaporated in an inert gas, nano-sized fine particles are generated, and an inert gas is used as a carrier gas to collide with a substrate at high speed.

In the GD method disclosed in Patent Document 1, as shown in the schematic diagram of FIG. 9, for example, Au is used as a bump material in the crucible 61 in the nanoparticle generation chamber 60 under a predetermined atmospheric pressure (for example, about 1 atmosphere of He gas). Melt the metal. Then, the Au metal is evaporated and quenched with He gas above the crucible 61, thereby generating Au nanoparticles which are metal fine particles. The generated Au nanoparticles are nozzle-jetted by a carrier gas (helium gas) in a vertical direction toward a vacuum film forming chamber 65 disposed above via a transfer pipe 63 having a nozzle 62 at the tip. The
On the other hand, in the film forming chamber 65, a plate-like stage 66 capable of reciprocating scanning movement in a one-dimensional direction (Y direction) is provided, and a Si substrate chip 70 (Si chip 70) on which a bump is formed on the lower surface of the stage 66. Is fixed with the processing surface facing downward.

For example, as shown in the cross-sectional view of FIG. 10A, the Si chip 70 is formed on a metal wiring pattern 73 on one surface side of a substrate 72 on which an oxide film (SiO ₂ ) 71 as an insulating layer is formed. A resist pattern 74 is formed. That is, the Au nanoparticles are sprayed on the resist pattern 74 together with the carrier gas.
In the Si chip 70, Au nanoparticles 76 are gradually formed on the recess 75 (exposed surface of the wiring pattern) formed by the resist pattern 74 and on the resist surface, as shown in time series of FIGS. 10B and 10C. To deposit. As the deposition of the Au nanoparticles 76 proceeds, the deposited portion gradually protrudes from the exit corner 75a of the recess 75 on the resist pattern 74, and the opening of the recess 75 decreases accordingly. For this reason, the Au nanoparticle 76 deposited on the exposed surface of the wiring pattern 73 (concave portion 75) approaches a tapered shape, that is, a conical shape.

  Then, the Au nanoparticles 76 protruding from the exit corner 75a of the recess 75 on the resist pattern 74 finally close the recess 75 as shown in FIG. 10D, and then the resist pattern 74 is attached to the substrate 72. By peeling from above, the conical bumps 30 formed on the wiring pattern 73 can be obtained as shown in FIG.

  By the way, in such a bump forming method, during the film formation (deposition) process of Au nanoparticles on the resist pattern 74, the temperature of the Si chip 70 rises rapidly, and the temperature of the resist pattern 74 becomes the heat resistant temperature. Thus, as shown in FIG. 11, there is a case where the outlet corner 75a of the recess 75 is sag and becomes round. And when the exit corner | angular part of the recessed part 75 becomes a round shape in such a way, the Au nanoparticle 76 deposited on the wiring pattern 73 and the Au nanoparticle 76 deposited on the resist pattern 74 will be finally shown as shown in the figure. There is a problem that it is difficult to separate the resist pattern 74 from the substrate.

In order to prevent such a problem, the applicants of the present application in Patent Document 1 prevent the sagging of the exit corner 75a in the recess 75 and maintain the angular right-angle shape of the exit corner 75a in FIG. As shown in the plan view of FIG. 12A and the side view of FIG. 12B, a metal plate 80 as a heat sink is provided under the substrate 81, and the substrate 81 is cooled to form a hole pattern 82 on the substrate 81. A method of setting the resist pattern 83 to be lower than the heat resistant temperature has been disclosed.
International Publication 2007/114314

However, just by placing the substrate 81 on the metal plate 80 as a heat sink as in the bump forming method disclosed in Patent Document 1, the diameter is several tens of μm (for example, about 30 μm) applicable to a MEMS device. There was a possibility that it could not cope with the bump formation.
In other words, when forming bumps of several tens of μm, it is necessary to form a thick resist pattern film, so that the resist pattern volume is increased and the heat radiation action to the metal plate 80 is reduced, and the substrate temperature is sufficiently increased. Could not be kept low.
Therefore, the exit corner portion 75a of the resist recess 75 is rounded and rounded, and the metal fine particles deposited on the metal wiring pattern and the metal fine particles deposited on the resist pattern are connected in contact with each other, so that the resist pattern cannot be peeled off from the substrate. There was a problem.

  The present invention has been made under the circumstances as described above, and deposits metal particles on a predetermined portion of a metal member formed on one side of a substrate by a gas deposition method to form fine metal bumps. Apparatus for forming fine metal bumps and forming method for fine metal bumps capable of easily and efficiently forming conical bumps on a substrate by suppressing excessive temperature rise of the substrate temperature regardless of the bump size And it aims at providing the formation method.

In order to solve the above-described problems, a fine metal bump forming apparatus according to the present invention is a substrate in which a hole pattern in which a predetermined portion of the metal wiring is exposed is formed on a mask layer covering the metal wiring formed on one side. Substrate holding means for holding the metal fine particle injection means for jetting metal fine particles obtained by evaporating metal from a nozzle together with a carrier gas to one surface side of the substrate held by the substrate holding means, A fine metal bump forming apparatus for depositing metal fine particles ejected by a metal fine particle ejecting means at a predetermined position of the metal wiring and forming a cone-shaped metal bump by a gas deposition method, wherein the substrate holding means is is formed in a larger size shape the lower surface of the substrate made of a metal heat radiating plate for holding the substrate from other side a cooling member, wherein It is interposed between the plate and the cooling member, a thermally conductive sheet having flexibility, while pressing the peripheral portion of one surface of the substrate, together with fixing the substrate to the cooling member, at least It has the characteristic that it has the fixing member which consists of a metal thermal radiation member which surface-contacts with the peripheral part of the one surface side of the said board | substrate, and the said cooling member .
The heat conductive sheet is preferably a sheet formed of In (indium).

With such a configuration, the heat of the substrate can be efficiently released to the cooling member through the heat conductive member having high adhesion such as an In sheet during the film formation process of the metal fine particles on the hole pattern. . Furthermore, since the fixing member comes into surface contact with the peripheral edge of the substrate, the heat of the substrate can be released to the cooling member also from the upper surface and side surfaces of the peripheral edge of the substrate.
For this reason, even when a resist pattern having a large volume necessary for forming a cone-shaped bump having a diameter of several tens of μm is formed, an excessive temperature rise of the substrate can be suppressed.
That is, during the film forming process of the metal fine particles, the shape of the edge of the hole pattern (the recess exit corner) can be maintained in an angular shape, and excessive adhesion of the mask layer (resist pattern) to the substrate can be suppressed. . Therefore, the mask layer can be easily peeled off after forming the metal fine particles, and a cone-shaped bump having a diameter of several tens of μm can be reliably obtained.

In addition, it is preferable that the substrate holding unit further includes a spare substrate that is held by the cooling member at a side of the substrate and has a heat insulating unit with respect to the cooling member.
In this way, by providing a preliminary substrate having heat insulating means for the cooling member, it is possible to confirm whether there is no problem in the deposition state by injecting metal fine particles from the nozzle in advance, and then perform bump formation On the other hand, a film forming process of metal fine particles can be performed.

In addition, when a plurality of conical bumps are formed, the fine metal bump forming method according to the present invention forms a hole pattern in which a predetermined portion of the metal wiring is exposed on a mask layer covering the metal wiring formed on one side. Substrate holding means for holding the formed substrate, and metal fine particle injection means for injecting metal fine particles obtained by evaporating metal from a nozzle together with a carrier gas to one side of the substrate held by the substrate holding means. The substrate holding means is formed in a size and shape larger than the lower surface of the substrate, and includes a cooling member made of a metal heat radiation plate for holding the substrate from the other surface side, and the substrate and the cooling member. The substrate is fixed to the cooling member in a state where the heat conductive sheet having flexibility and the peripheral portion on the one surface side of the substrate are pressed, and at least Metal ejected by the metal fine particle ejecting means using a fine metal bump forming device having a peripheral part on one side of the substrate and a fixing member made of a metal heat radiation member in surface contact with the cooling member A method for forming fine metal bumps, in which fine particles are deposited at predetermined positions of the metal wiring, and a plurality of conical metal bumps are formed by a gas deposition method, wherein a plurality of the hole patterns are formed in a mask layer on the substrate. Are aligned so that the center axis of the nozzle coincides with the center of the hole pattern , and the plurality of hole patterns are formed so that the center axis of the nozzle passes through the center of the hole pattern. The nozzles are relatively moved along the line, and the metal fine particles are forwarded together with the carrier gas toward the hole patterns. It injected from the nozzle, having the features of the fine metal particles to be deposited in a predetermined position of the metal wiring.
In addition, it is preferable that the relative scanning movement distance of the nozzle is a distance between centers of the hole pattern at one end and the hole pattern at the other end in a row in which the plurality of hole patterns are formed.
As described above, the plurality of cone-shaped bumps can be efficiently obtained at high speed by moving the nozzles relative to the plurality of hole patterns.

  According to the present invention, in a fine metal bump forming apparatus and method for forming fine metal bumps by depositing metal particles by a gas deposition method on a predetermined portion of a metal member formed on one side of a substrate, It is possible to obtain an apparatus and a method for forming a fine metal bump that can suppress the excessive temperature rise of the substrate temperature regardless of the bump size and can easily and efficiently form the cone-shaped bump on the substrate.

Embodiments of a fine metal bump forming apparatus and forming method according to the present invention will be described below. In the fine metal bump forming apparatus of the present invention, the same structure as shown in FIG. 9 can be used as the apparatus structure for performing the gas deposition method. Therefore, in the following description, the same reference numerals are used for the same functions as those in FIG.
FIG. 1 is a perspective view showing a configuration of a heat sink substrate (substrate holding means) for holding an Si chip on which a tapered cone-shaped bump is formed in the bump forming apparatus of the present invention. The heat sink substrate 1 is arranged in place of the Si chip 70 shown in FIG.
The heat sink substrate 1 is a chip for fixing a cooling substrate 2 (cooling member) made of a metal heat radiation plate and an Si chip 10 (substrate) mounted on the lower surface of the cooling substrate 2 to the cooling substrate 2. And a fixing jig 3 (fixing member). The chip fixing jig 3 is configured to be fastened to the cooling substrate body 2 using, for example, bolts 5.

The cooling substrate 2 has a volume that can sufficiently absorb the heat of the Si chip 10 and is formed of, for example, a Cu plate subjected to Au plating.
Here, the Si chip 10 is brought into close contact with the cooling substrate 2 via a flexible heat conductive sheet of substantially the same size, specifically, an In (indium) sheet 4, and is fixed by the chip fixing jig 3. The Since the In sheet 4 is a soft member having excellent flexibility, the In sheet 4 can be in close contact with the Si chip 10 and the cooling substrate 2 without any gap. For this reason, the thermal conductivity from the Si chip 10 to the cooling substrate 2 can be improved.
The In sheet 4 is desirable as the heat conductive sheet, but a flexible sheet such as Au, Ag, or Cu may be used instead.

Further, the chip fixing jig 3 is made of a metal heat radiating member, for example, a Cu member that has been subjected to Au plating processing, and its central portion corresponds to the outer peripheral shape of the Si chip 10 as shown in the figure. The chip attachment portion 3a is formed by being cut out in a U shape. Further, a flange 3b capable of locking the outer peripheral edge of the Si chip 10 is formed on the inner peripheral edge of the U-shaped shape.
When the Si chip 10 is fixed by the chip fixing jig 3, the Si chip 10 is further disposed on the chip mounting portion 3 a via the In sheet 4 between the Si chip 10 and the cooling substrate 2. Thereby, the said collar part 3b latches to the peripheral part of the one surface side (to-be-processed surface side) of Si chip | tip 10. FIG.

Then, by fixing the chip fixing jig 3 to the cooling substrate 2 with the bolt 5, the In sheet 4 is in close contact with the Si chip 10 and the cooling substrate 2, and there is a gap between the Si chip 10 and the cooling substrate 2. There will be no state.
Further, since the flange portion 3b of the chip fixing jig 3 is locked to the peripheral edge portion of the Si chip 10, the chip fixing jig 3 is in surface contact with at least the peripheral edge portion on one surface side of the Si chip 10 and the cooling substrate 2. To do.
As a result, the heat of the Si chip 10 can be released from the contact surface with the chip fixing jig 3, and can be further conducted from the chip fixing jig 3 to the cooling substrate 2.
Therefore, the heat of the Si chip 10 is conducted to the cooling substrate 2 from the back surface (surface facing the cooling substrate main body 2 side) and the peripheral portion, so that the heat of the Si chip 10 is efficiently reduced, and the excessive temperature rise is caused. Can be suppressed.

Further, the heat sink substrate 1 is provided in a state where the surface to be processed faces in the same direction as one surface side (the surface to be processed) of the Si chip 10 in the vicinity of the fixing position of the Si chip 10. The auxiliary substrate 11 is fixed by a fixed rod 11a.
The preliminary substrate 11 is provided for performing a preliminary test for injecting Au nanoparticles from a nozzle onto the surface to be processed and observing the deposition state before the film formation process on the Si chip 10. Thereby, more reliable bump formation can be realized.
Note that the fixing rod 11a can be formed of, for example, stainless steel having low thermal conductivity, so that the heat of the preliminary substrate 11 raised in temperature during the preliminary test is difficult to conduct to the Si chip 10.

The Si chip 10 fixed to the heat sink substrate 1 having such a configuration is, for example, an insulating SiO ₂ film (for example, a 300 nm film) on a Si wafer having a predetermined thickness (for example, 380 μm) and a predetermined size (for example, 7.5 mm square). (Thickness) is formed, and an Au (for example, 500 nm) / Ti thin film (for example, 20 nm) pad is formed thereon. Further, a photoresist (for example, a film thickness of 30.5 μm), which is a mask layer for forming a cone-shaped bump, is formed on the pad. In the resist pattern, a bump is formed in a concave portion. A certain hole pattern (for example, 30 μm in diameter) is formed in a plurality of lines, for example, in line with the pad position (for example, 60 μm pitch).

The heat sink substrate 1 to which the Si chip 10 is fixed is fixed to the lower surface of the stage 66 of the film forming chamber 65 in a vacuum state (for example, 0.3 Pa) in the same apparatus configuration already described in FIG. As described above, it is arranged in place of the Si chip 70 of FIG.
The stage 66 is provided so as to be capable of reciprocating (scanning) in at least one direction (Y direction). With the heat sink substrate 1 fixed to the stage 66, the bump forming surface of the Si chip 10 faces downward. The scanning direction of the stage 66 coincides with the plurality of hole pattern columns formed.
Next, the tip of the nozzle 62 (for example, the tip inner diameter 500 μm) and the end of the chip 10 are monitored via a CCD camera or the like so that the nozzle center axis coincides with the hole center of the resist pattern. Alignment work to pass through the center of the hole pattern.

On the other hand, in the vacuumed Au nanoparticle production chamber 60 (for example, 2 × 10 ^_2 Pa), Au is melted in the crucible 61 at a predetermined temperature (for example, 1550 ° C.), evaporated from the crucible 61, and the He gas above the (For example, the supply flow rate is 30 L / min or more) and quenching, thereby generating Au nanoparticles.
The generated Au nanoparticles are transported to the film forming chamber 65 by the transport pipe 63 and are sprayed toward the Si chip 10 from the nozzle 62 heated to a predetermined temperature (for example, about 300 ° C.). As described above, the apparatus configuration of the Au nanoparticle generation chamber 60 that generates Au nanoparticles and the nozzle 62 constitute a metal fine particle injection unit.

At this time, the stage 66 continuously repeats a predetermined distance in the Y direction shown in FIG. 9 (the distance between the center of the hole pattern at one end of a row and the hole pattern at the other end where a plurality of hole patterns are formed) a predetermined number of times. The scan is moved at a predetermined speed (for example, 2 mm / s).
By this process, Au nanoparticles are deposited on the resist pattern of the Si chip 10, and when all the hole patterns are filled, the Au nanoparticle film forming process is completed.
Thereafter, the silicon chip 10 is immersed in acetone, and the photoresist is peeled off and removed, whereby a cone-shaped bump formed on the pad of the Si chip 10 can be obtained.

As described above, according to the embodiment of the present invention, the heat of the Si chip 10 during the film formation process of the Au nanoparticles on the resist pattern is used as the In sheet 4 as a heat conductive member having high adhesion. By passing through, it is possible to efficiently escape to the cooling substrate 2.
Furthermore, by fixing the Si chip 10 to the cooling substrate 2 with the chip fixing jig 3 having good thermal conductivity, at least the peripheral portion on one surface side of the Si chip 10 is in surface contact with the chip fixing jig 3. Heat can also be released from the peripheral edge of the Si chip 10.
For this reason, even when a resist pattern having a large volume necessary for forming a cone-shaped bump having a diameter of several tens of μm (for example, 30 μm) is formed, excessive temperature rise of the Si chip 10 is suppressed and the temperature is kept low. be able to.
That is, during the deposition process of Au nanoparticles, even when the resist pattern volume is large, the hole corner of the hole pattern is maintained in an angular shape, and excessive adhesion of the photoresist to the Si substrate is suppressed. Can do. Therefore, the photoresist can be easily peeled off after the Au nanoparticle film forming process, and a cone-shaped bump having a diameter of several tens of μm can be reliably obtained.
Further, a plurality of hole patterns of photoresist are formed in a line, a hole pattern at one end of a line in which a plurality of hole patterns are formed with a scan distance so that the nozzle center axis relatively passes through the center of the hole pattern. By setting the distance between the center of the hole pattern at the other end, a plurality of cone-shaped bumps can be obtained efficiently at high speed.

  The apparatus and method for forming fine metal bumps according to the present invention will be further described based on examples. In this example, a process of forming a plurality of conical bumps on the Si chip was performed according to the above embodiment, and the effect of the present invention was verified.

[Example 1]
In Example 1, a bump formation experiment was performed based on the bump formation method described in the above embodiment. In forming the Si chip, first, an insulating SiO ₂ film (film thickness: 300 nm) was formed on the entire surface of a 380 μm-thick 3 inch Si wafer by sputtering.
Next, in order to form an electrode pad for bump formation, a pad-shaped photoresist pattern is formed on the SiO ₂ film by a photolithography process, and considering the adhesion to the bump, Au (500 nm) / Ti (20 nm). ) Was continuously formed by vacuum deposition, and the excess Au / Ti thin film on the resist was removed by a lift-off process.

  As a photoresist for forming the cone-shaped bumps, a general-purpose thick film resist AZP4903 (AZ electric materials) was used to form a film to 30.5 μm by spin coating, and holes for forming the bumps were formed by alignment exposure. The hole pattern in this photoresist was designed as a circular shape with a diameter of 30 μm and a pitch of 60 μm. However, since the depth of focus of the used exposure machine is 15 μm or less, the exposure amount is excessive until the pad surface is completely exposed. The hole shape shown in the SEM photograph of FIG. 2A was finally obtained by increasing and developing.

Then, the Si wafer on which this hole pattern was formed was diced into 7.5 mm square to produce Si chips. Note that a total of 105 hole patterns are formed in a row on the upper surface of the Si chip at a position 500 μm away from the side edge.
Such a Si chip was attached to a heat sink substrate having the configuration shown in FIG. 1, and bump formation was performed by nozzle-jetting and depositing Au nanoparticles in the deposition chamber.
Other conditions in this experiment are shown in Table 1.

As a result of this experiment, a conical cone-shaped bump as shown in the SEM photograph of FIG. This bump had a height of 37.9 μm as measured by a laser microscope.
Further, since the inclination angle of this bump was 65.5 degrees and the resist film thickness was 30.5 μm, it was found that the bump tip grew 1.2 times higher than this resist film thickness.
By observing the SEM photograph of the formed bump, it was confirmed that the resist could be completely removed with an organic solvent without residual resist.
This is probably because the substrate temperature measured during the film formation process by the GD method was 63 ° C. at the maximum due to the effect of the heat sink, that is, below the baking temperature of the photoresist, so that the photoresist could be easily peeled off. It was. The substrate temperature is generally the same as the temperature of the plating bath, and it can be said that the bump forming method of the present invention is a low-temperature process.

FIG. 3 shows the shape profile in the height direction of the aggregated thin film of Au nanoparticles deposited on the Si substrate simultaneously with the formation of the cone-shaped bumps. FIG. 3A is an SEM photograph in which the Au nanoparticles formed in the scan direction (y direction) are viewed in plan, and FIG. 3B is a graph showing the deposition profile.
This shape profile was measured using a stylus profilometer. The maximum height was 91.4 μm, and it became a very smooth shape symmetrically from this apex. This vertex is considered to correspond to the nozzle center position. If the center of the hole is on the extension of the nozzle center axis, the film thickness is 91.4 μm after 100 scans, so the film thickness per scan is 0.91 μm / scan. Since the height of the bump formed in the experiment is 37.9 μm, it can be considered that the cone-shaped bump was formed in 42 scans. Under this experimental condition, since the scan is performed once every 10 seconds, the time required for bump formation is 7 minutes. That is, it is considered that the hole was completely closed in 7 minutes, and the subsequent film formation for 9 minutes and 40 seconds did not contribute to bump formation.

At this time, the scan distance was 20 mm for a 7.5 mm square chip size. Therefore, when the scan distance is 7.5 mm, which is the same as the chip size, the scan distance of 20 mm is one scan distance. While it takes 10 seconds, the 7.5 mm scan distance is shortened to 3.75 seconds, so the bump formation time is converted to 2 seconds 38 seconds. At this time, one bump can be formed in only 1.5 seconds.
Thus, even in a thick film resist having a thickness of 30 μm, it was proved that thermal damage due to high-speed film formation by the GD method can be reduced by adding a heat sink, and a 30 μm size cone-shaped bump can be formed.

If further consideration is made, the calculation example of the cone-shaped bump production time is a case where the nozzle center position is coincident with the hole, but actually, the mounting of the chip is inclined with respect to the scanning direction, The alignment accuracy with a CCD camera is not sufficient.
In FIG. 4A, the hole position is away from the central axis of the nozzle, and the film formation process cannot be completed in the middle of the film formation conditions according to this embodiment, and the film cannot be formed into a conical shape. An SEM photograph of another example is shown. FIG. 4B is a graph showing the position of the bump in the deposition profile.

  That is, since the slope of the upper surface of the bump is rising to the right, it is considered that the bump is produced at a position on the left side (x <0) from the apex on the deposition profile in FIG. When the maximum value and minimum value of the height of the upper surface, which is a characteristic point of this bump, were measured with a laser microscope, they were 30.7 μm and 25.7 μm, respectively.

  When this value is read on the deposition profile as x, they are 104.6 μm and 115.0 μm, respectively. Since the intermediate value of x is considered to correspond to the position of the bump center, it is estimated that the center position of the bump is 109.8 μm away from the nozzle center position, and the height of the bump center is 28.2 μm. Can be read from the profile. The graph of FIG. 4B is obtained by superimposing the bump on the deposition profile.

In the experiment in this example, it is considered that the inclination of the Si chip with respect to the stage scan direction (y direction) has a positional relationship as shown in FIG.
That is, as shown in FIG. 5B, it is considered that the closer the hole position is to the central axis of the nozzle, the more the hole is closed, and the Si chip is attached with the hole row inclined at an angle θ from the stage scanning direction.

  In order to calculate the mounting inclination θ of this chip, as described above, the center position of the bump is read from the deposition profile, and the inclination θ as shown in FIG. When calculating and finally calculating the average value of 10 times, the inclination θ of the chip with respect to the scanning direction was 0.8 degree. Even if the nozzle center coincides with the first of 105 holes in one row, the 105th hole 6240 μm away from the first hole is 87 μm away from the nozzle center. The thickness was reduced by 43.5% compared to the thickness at the nozzle center.

The deposition profile can be expressed as a change in deposition rate with respect to the distance from the nozzle center to the hole.
FIG. 6A shows a change in the film forming speed with respect to the hole position away from the center of the nozzle, which is obtained from the result of the deposition profile in FIG. Further, the second axis of the vertical axis in the figure shows the change in the formation time of the bump height of 37.9 μm with respect to the hole position away from the nozzle central axis.
As shown in this graph, it can be seen that when the hole position is 140 μm or more away from the nozzle central axis, the bump formation time takes 40 minutes. Therefore, if the scan distance is shortened by 7.5 mm, which is the same as the chip size, and 37.5%, the number of scans for bump formation can be achieved earlier by this amount.
In order to efficiently increase the speed of bump formation in this way, the hole position must be aligned with the nozzle center axis, and the scan distance should be shortened to the minimum necessary so that the film is formed only where the hole exists. (I.e., the relative scanning movement distance of the nozzle is the distance between the centers of the hole pattern at one end and the hole pattern at the other end of a row in which a plurality of hole patterns are formed). .

  In addition, since the bump formation time is the time when all the rows of bumps are formed in the same shape, the number of scans is an integer value. For this reason, as shown in the enlarged graph of FIG. 6B, the number of scans is the same as 42 times up to the hole position 7.9 μm away from the nozzle center position. The bump formation time at this point can be formed without changing from the nozzle center position.

That is, it was confirmed that if an optical alignment mechanism is added and alignment accuracy of a relatively coarse several μm level can be secured, bumps can be formed efficiently and at high speed.
As described above, according to this embodiment, according to the fine metal bump forming apparatus and forming method of the present invention, it is possible to suppress overheating of the substrate temperature during the film forming process by the gas deposition method regardless of the size of the bump. It was confirmed that cone-shaped bumps can be formed on the substrate.

  The present invention relates to a fine metal bump forming apparatus and method for forming fine conical metal bumps at predetermined locations on a metal member formed on one surface of a substrate.

FIG. 1 is a perspective view showing a configuration of a heat sink substrate for holding a Si chip on which a tapered cone-shaped bump is formed in the bump forming apparatus of the present invention. FIG. 2 is an SEM photograph of the hole pattern of the photoresist and the cone-shaped bump formed in the example of the present invention. FIG. 3 shows a deposition profile in the height direction of an agglomerated thin film of Au nanoparticles deposited on a Si substrate simultaneously with the formation of the cone-shaped bump in the example of the present invention. FIG. 4 shows an example in which the hole position is away from the central axis of the nozzle, and the film formation process is terminated in the middle without being able to completely close the hole under the film formation conditions of this embodiment, so that the conical shape cannot be formed. It is a graph which shows the position of this bump in the SEM photograph and the deposition profile of FIG. FIG. 5 is a graph for explaining the inclination of the Si chip with respect to the stage scan direction (y direction). FIG. 6 shows the change in the deposition rate with respect to the hole position away from the nozzle center and the change in the bump height formation time with respect to the hole position away from the nozzle center axis, obtained from the result of the deposition profile in FIG. It is a graph. FIG. 7 is a diagram for explaining a conventional metal bump. FIG. 8 is a diagram for explaining the cone-shaped bumps. FIG. 9 is a view schematically showing an apparatus using a gas deposition method applicable to the fine metal bump forming method of the present invention. FIG. 10 is a diagram for explaining, in a time series, the bump forming process by the fine metal bump forming method of the present invention and the bump forming method disclosed in Patent Document 1. FIG. 11 is a view for explaining a state in which the exit corner portion of the concave portion of the resist pattern is rounded. FIG. 12 is a diagram showing a metal plate as a heat sink disclosed in Patent Document 1. As shown in FIG.

Explanation of symbols

1 Heat sink substrate (substrate holding means)
2 Cooling substrate (cooling member)
3 Chip fixing jig (fixing member)
4 In sheet (thermally conductive sheet)
5 Volt 10 Si chip (substrate)
11 Preliminary substrate 30 Cone-shaped bump 60 Au nanoparticle generation chamber 61 Crucible 62 Nozzle 63 Transfer tube 65 Deposition chamber 66 Stage

Claims (5)

Substrate holding means for holding a substrate on which a hole pattern in which a predetermined portion of the metal wiring is exposed is formed in a mask layer covering the metal wiring formed on the one surface side;
Metal fine particle injection means for injecting metal fine particles obtained by evaporating metal from a nozzle together with a carrier gas to one side of the substrate held by the substrate holding means,
A fine metal bump forming apparatus for depositing metal fine particles ejected by the metal fine particle ejecting means on a predetermined portion of the metal wiring and forming a cone-shaped metal bump by a gas deposition method,
The substrate holding means is
A cooling member made of a metal heat radiation plate formed in a size and shape larger than the lower surface of the substrate and holding the substrate from the other surface side;
A thermally conductive sheet interposed between the substrate and the cooling member and having flexibility ;
A metal heat radiation member that fixes the substrate to the cooling member while pressing the peripheral portion on the one surface side of the substrate and is in surface contact with at least the peripheral portion on the one surface side of the substrate and the cooling member. And a fine metal bump forming apparatus. 2. The apparatus for forming fine metal bumps according to claim 1, wherein the thermal conductive sheet is a sheet formed of In (indium). The substrate holding means further includes
3. The formation of fine metal bumps according to claim 1, further comprising a spare substrate held by the cooling member at a side of the substrate and having a heat insulating means for the cooling member. 4. apparatus. A substrate holding means for holding a substrate on which a hole pattern exposing a predetermined portion of the metal wiring is formed on a mask layer covering the metal wiring formed on the one surface side; and one surface side of the substrate held by the substrate holding means In contrast, metal fine particle injection means for injecting metal fine particles obtained by evaporating metal together with a carrier gas from a nozzle, the substrate holding means is formed in a size and shape larger than the lower surface of the substrate, A cooling member made of a metal heat radiation plate held from the other surface side, a flexible heat conductive sheet interposed between the substrate and the cooling member, and a peripheral edge on one surface side of the substrate The substrate is fixed to the cooling member in a pressed state, and at least a solid heat radiation member made of a metal heat radiating member is in surface contact with the peripheral portion on one surface side of the substrate and the cooling member. And forming a plurality of conical metal bumps by a gas deposition method by depositing metal fine particles ejected by the metal fine particle ejecting means at predetermined locations of the metal wiring. A method of forming fine metal bumps,
In the mask layer on the substrate, a plurality of the hole patterns are formed in a row,
Perform alignment so that the central axis of the nozzle coincides with the center of the hole pattern,
The nozzle is relatively scanned and moved along the row in which the plurality of hole patterns are formed such that the center axis of the nozzle passes through the center of the hole pattern,
The metal fine particles are jetted from the nozzle together with a carrier gas toward each hole pattern,
A method for forming fine metal bumps, wherein the metal fine particles are deposited at predetermined positions of the metal wiring. The relative scanning distance of the nozzle is
5. The method for forming fine metal bumps according to claim 4 , wherein a distance between centers of a hole pattern at one end and a hole pattern at the other end in a row in which the plurality of hole patterns are formed is set.