JP2005142537A - Longitudinal vibration bonding method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of misregistration due to the inability of uniform bonding with transverse vibrations used conventionally in order to reduce damages, and a problem of not being effective for an object requiring a high load in a large area like a wafer in a bonding device for bonding a plurality of superposed objects to be bonded by vibrational energy. <P>SOLUTION: This invention provides a bonding device using longitudinal vibrations and reducing damages. Moreover, arranging a plurality of piezo-actuators side by side prevents flexure, and allows a large area to be vibrated with high energy under a high load. Moreover, three-dimensional motions are permitted, and the structure is effective for reductions in loads and voids in bonding, and moreover effective to an object requiring a high load in a large area such as a wafer that is mainly handled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a joining method and a joining apparatus for joining a plurality of superposed objects by applying vibration. Especially in the field of mounting semiconductor chips with high precision and wafer bonding.

Conventionally, as a method of joining a plurality of stacked objects to be joined by ultrasonic vibration, as shown in Patent Document 1 and Patent Document 2, both ends are supported, a vibrator is attached horizontally, and transverse vibration is used. The method is adopted. This is because the longitudinal vibration is an operation like hitting the chip with a hammer from above, and is easily damaged. In the lateral vibration, the vibration is distorted by a frictional force, so that the damage is hardly caused. Therefore, particularly when one of the objects to be bonded is made of a semiconductor chip, the lower layer metal portion of the metal protrusion serving as a semiconductor electrode is susceptible to damage due to micro cracks caused by ultrasonic vibration. In the case of the ultrasonic vibration head, the longitudinal vibration is suppressed within 5%. The ultrasonic vibration having a amplitude of about 4 to 8 μm at 40 to 60 kHz is used. The amplitude of 4 to 8 μm due to the longitudinal vibration is not a range that can be absorbed by the elastic deformation of the semiconductor chip, but an operation of impacting the chip from above with a gap between the object holding means and the chip.

  However, when ultrasonic bonding is performed using lateral vibration, stress is applied to the peripheral portion due to elastic deformation of the metal protrusion due to lateral vibration, and the metal protrusion does not become uniform as shown in FIG. Only the periphery will be joined. It can be seen from FIG. 5 that uniform bonding can be achieved in the case of longitudinal vibration. FIG. 5 shows an interfacial stress analysis for joining metal bumps by longitudinal vibration and transverse vibration. It is considered that a portion having a high stress is joined by a new surface appearing due to elongation of the interface.

  Of course, mounting with a high accuracy of several μm is difficult because the horizontal amplitude causes a mounting position shift.

  In addition, as shown in Patent Document 3 and Patent Document 4, a technique is disclosed in which the bonding surfaces are cleaned with energy waves and bonded at room temperature in an activated state. Since high temperature is not required, the problem of thermal expansion does not occur, and mounting with high accuracy within 1 μm is possible, and is attracting attention. However, when gold metal protrusions are bonded, as shown in Table 1, bonding cannot be performed unless they are crushed with a high pressure of about 300 Mpa at room temperature. When this bump is on the surface of the semiconductor circuit, the circuit is generally damaged at 200 Mpa or more.

  The conditions in Table 1 are as follows: a semiconductor chip using gold bumps of 50 μm square, 20 μm in height and 1 μm in bump height, which are metal protrusions on the semiconductor chip, and ultrasonic bonding to a gold thin film substrate and room temperature bonding This is the data when In the case of room temperature bonding, bonding was possible for the first time at 80 g / bump, but when ultrasonic waves were applied, bonding was possible with a load of 40 g / bump or more. Therefore, it can be seen that it is necessary to crush bumps of 1 μm or more as a bump crushing allowance. In the case where a bump having a height of 20 μm is formed by gold plating, it is necessary to crush the bumps of this degree because it is the limit to suppress the height variation to 1 μm.

従来、特許文献１に示すようにホーンに対し１つの振動子でホーンを共振させる振動手段であった。

Conventionally, as shown in Patent Document 1, it has been a vibrating means for resonating a horn with one vibrator with respect to the horn.

  The method shown in Patent Document 2 has a structure in which two vibrators are provided in a perpendicular direction so that a two-dimensional trajectory can be drawn.

In Patent Document 6, the surface of the metal junction is sputter-etched with an Ar ion gun in a high vacuum of 10 ⁻⁵ Torr or less to remove the oxide film and organic layer on the surface, and the metals are directly connected to each other at room temperature. A technique called room temperature bonding for bonding is disclosed. It is a high-vacuum device of research level that is difficult to use in mass production called an ion gun, usually at a high vacuum of ^10-8 to ^10-5 Torr.

  Patent Document 7 describes a method in which the surface of a wafer is activated by adsorbing OH groups to the bonding surface with oxygen plasma to activate the surface and heat bonding.

Patent No. 291530 JP-A-11-307597 JP2002-50861 JP 2001-318992 A JP 2000-176653 A JP 54-124853 A JP-A-3-91227

As a conventional problem, when joining objects to be joined by ultrasonic vibration, if longitudinal vibration is used, since uniform joining and mounting displacement do not occur, high-accuracy mounting is possible, but damage occurs. If lateral vibration is used, damage can be reduced, but uniform bonding cannot be achieved, and misalignment also occurs.

  Further, in room temperature bonding by surface activation, high-precision mounting is possible, but high pressure is required, and if there are bumps on the circuit surface, the circuit is damaged. Moreover, as shown in Patent Document 3 and Patent Document 4, a chamber composition in an inert atmosphere is required, resulting in a large-scale apparatus.

  In particular, in the field of mounting semiconductor chips with high accuracy, high-precision mounting within 1 μm is preferably required for metal bonding at low temperatures, and the above-described problem solving is particularly desired.

Conventionally, transverse vibration has been used to reduce damage, but it can be seen that longitudinal vibration is effective from the problem of bonding uniformity and displacement. However, since longitudinal vibration causes damage, the problem is how to reduce the damage and join by longitudinal vibration. In addition, uniform bonding and high-precision mounting have been achieved in room temperature bonding, but high pressure remains as a problem.
In the method according to Patent Document 1, since the horn is resonated by one vibrator, the vibration is in one direction and cannot be moved three-dimensionally. Moreover, since it is one, the energy is small. Moreover, a large area cannot be vibrated.
Further, in the method shown in Patent Document 2, it is a transverse vibration in a direction perpendicular to the pressing surface, and a three-dimensional operation cannot be performed even if a two-dimensional trajectory can be drawn.
When considering a joining device, the frictional force cannot be vibrated greatly by transverse vibration to join in a large area. However, longitudinal vibration is advantageous for bonding in a large area because stress can be applied to the bonding interface while the bonding surface is in contact. FIG. 5 shows the stress distribution analysis result by the transverse vibration and the longitudinal vibration when the metal protrusions are joined by the vibration in the ultrasonic region. When bonding is performed using lateral vibration, stress is applied to the peripheral portion due to elastic deformation of the metal protruding portion with respect to the lateral vibration, resulting in a non-uniform bonding as shown in FIG. 5 and bonding only around the metal protruding portion. It will be. It can be seen from FIG. 5 that uniform bonding can be achieved in the case of longitudinal vibration. FIG. 5 shows an interfacial stress analysis for joining by means of longitudinal vibration and transverse vibration of the metal protrusion, and it is considered that the portion with high stress is joined by the emergence of a new surface due to the elongation of the interface. Of course, mounting with a high accuracy of several μm is difficult because the horizontal amplitude causes a mounting position shift. However, if the pressure is vibrated evenly while the stress is concentrated on a part of the time and moved, joining of a large area is possible with a small vibration pressure source. For this purpose, a three-dimensional operation is required.

  Further, in Patent Document 6, although the surface activated bonding technique does not leave bubbles or residuals, it requires a high vacuum process for preventing re-adhesion using an ion gun or the like, resulting in an expensive and complicated apparatus. Moreover, since it was normal temperature, a high load of 300 MPa was essential, which hindered mass production. Moreover, there existed a subject that it was not applicable except metals.

  In Patent Document 7, OH groups are adsorbed and the wafers are surface-bonded by hydrogen bonding, but heating at a high temperature is required. Therefore, it cannot be used for a semiconductor or MEMS device having a heat-resistant problem, and warpage occurs at the junction between different kinds of materials having different linear expansion coefficients, which causes the worst cracking.

  In addition, there are particles that become small dust on the bonding surfaces of a plurality of objects to be bonded that are in close contact with each other, and in the methods of Patent Documents 3, 4, and 6, when bonded as a solid layer at a low temperature, There are gaps around the particles and they become large voids that are not joined. In particular, when wafers are bonded to each other, there are 10 or more particles of 0.2 μm or more in a normal wafer. This is the value that is already on the ready-made catalog. For this reason, when wafers are actually bonded together at a low temperature solid layer, voids having a size of about 10 mm remain in several places. In order to remove this, it is impossible with ordinary cleaning methods, and it is practically impossible because particles adhere when the wafer is handled after cleaning.

  Accordingly, the present invention has been made in view of the circumstances as described above, and a plurality of superimposed objects to be joined are added between the head and the stage, which are the object holding means supported by the joining mechanism. Vibration is transmitted from the vibrator held by pressure and coupled to the object-holding means to the object-holding means, and longitudinal vibration is used in the joining device where multiple stacked objects are joined by vibration energy. Then, it is providing the method and joining apparatus which join a to-be-joined object, and reduce damage. It is another object of the present invention to provide a method and a joining apparatus for joining an object to be joined having a large area using longitudinal vibration. In addition, a method of pressurizing objects to be pressed, wherein a plurality of piezo actuators are in contact with the object to be pressed and the facing surface of at least one holding tool among the holding tools that hold both objects to be pressed. It is an object of the present invention to provide a method and a pressurizing device for applying longitudinal vibration by an expansion / contraction operation of a piezo actuator in a state where both pressurized objects are contact-pressed in a connected joining mechanism.

The means of both the joining method and the joining apparatus according to the present invention for solving the above-described problems will be described collectively below. In particular, in the field of mounting semiconductor chips with high accuracy, high-precision mounting of about 1 μm is required for metal bonding at low temperatures, and the above-described problem solving is particularly desired.

  (Claim 1) In order to solve the above-described problem, a bonding method and a bonding apparatus according to the present invention are configured such that a plurality of stacked objects to be bonded are between a head and a stage which are objects to be bonded holding means in a bonding mechanism. In a bonding apparatus in which vibration is transmitted from a vibrator coupled to a workpiece holding means to the workpiece holding means and vibration is applied to a plurality of stacked workpieces to be joined. It consists of a method of joining objects to be joined using vibration. In addition, a plurality of stacked objects to be bonded are pressed and held between the head and the stage, which are the objects to be bonded holding means in the bonding mechanism, and bonded from the vibrator coupled to the objects to be bonded holding means. A joining apparatus that transmits vibrations to the object holding means and applies vibrations to a plurality of overlapped objects to be joined to each other and includes joining apparatuses that join the objects to be joined using longitudinal vibration. The object holding means is a horn part in a conventional ultrasonic vibration device, and has a function of transmitting vibration from a vibrator, amplifying by resonance, and holding an object to be bonded by adsorption or the like. It is a part. In this joining mechanism, the part including the upper article holding means is divided into the head side and the stage side, and the part including the lower article holding means is called the stage. In addition, as a method for joining objects to be joined, a method for joining by applying ultrasonic vibration has been known. The term “vibration” as used herein refers to a range from a low frequency to an ultrasonic region, and the frequency is not particularly limited and is included in the present invention. Also, ultrasonic waves are often used for bonding, which is preferable. Further, it is preferable that a large energy can be output by resonating with the object holding means. Conventionally, transverse vibration has been used to reduce damage, but it can be seen that longitudinal vibration is effective from the problems of joint uniformity and misalignment as described above. Further, in a large-area bonding such as a wafer, vibration cannot be applied to the interface from frictional force by lateral vibration, but can be transmitted by longitudinal vibration. A method for vibrating and bonding the large area will be described later. The longitudinal vibration ratio is 10% or more. Moreover, it consists of the joining apparatus whose ratio of the said longitudinal vibration is 10% or more. Conventionally, the method using the horizontal vibration has suppressed the vertical vibration within 5% from the reduction of damage, but in the present invention, the vertical vibration of 10% or more is used. Moreover, 50% or more is preferable.

  (Item 2) Further, the method according to the above, wherein the amplitude of the vibration is 1 μm or less. The bonding apparatus according to item 1, further comprising an oscillating unit that sets the amplitude of the vibration to 1 μm or less. The amplitude measurement point generally refers to the amplitude at the object holding means. Since longitudinal vibration causes damage, the point is how to reduce the damage and join by longitudinal vibration. The solution is to set the amplitude to 1 μm or less. By doing so, the amplitude of 1 μm can be absorbed by the elastic deformation of the bumps in the case of a semiconductor chip with, for example, 20 μm high metal bumps.

  (Item 3) Further, the method according to Item 1 or Item 2, wherein the object is held by at least one object holding means or its supporting member via an elastic body. The joining apparatus according to Item 1 or 2, wherein the joining device holding means or the supporting member thereof has an elastic body and is held via the elastic body. Moreover, the impact by a longitudinal vibration can be absorbed by attaching an elastic material to the front-end | tip of a to-be-joined object holding means. The impact of longitudinal vibration becomes a problem because the operation is such that the tip is impacted by a hammer with a gap between the object holding means and the tip. Therefore, damage can be reduced if it is absorbed by an elastic material or a bump so as not to open a gap. In joining, since a stress change is transmitted to the joining interface, there is no problem because a new surface appears due to the crushing movement of particles at the interface and the joining proceeds. Further, not only the tip portion but also the workpiece holding means, the support member that supports the workpiece holding means, the head, or the stage is held by an elastic body, so that the workpiece is relieved in the vibration direction. Can absorb strong vibrations.

  (Claim 4) In the joining mechanism in which the longitudinal vibration direction and the pressurizing direction are the same, the joining mechanism has a pressurizing means that can move in the pressurizing direction at the time of joining. It consists of the method in any one of claim | item 1 -3 which controls pressure. In a joining mechanism with the same longitudinal vibration direction and pressurizing direction, it has a pressurizing means that can move in the pressurizing direction during joining, and pressurization control is performed with a constant pressure while being movable in the longitudinal vibration direction during vibration application. It consists of a joining apparatus in any one of claim | item 1 -3 which has a pressurization means. By pressurizing and controlling at a constant pressure while being movable in the longitudinal vibration direction during application of vibration, the object to be joined escapes in the longitudinal vibration direction, and excess longitudinal vibration can be absorbed.

  (Item 5) The method according to any one of Items 1 to 4, wherein the vibrator and the object-to-be-bonded holding unit are a capillary method in which a ratio of longitudinal vibration is 10% or more. Item 5. The bonding apparatus according to any one of Items 1 to 4, wherein the vibrator and the object holding unit are capillary systems having a longitudinal vibration ratio of 10% or more.

  (Claim 6) The vibrator and the object-to-be-joined holding means are a composite vibration head in which a ratio of longitudinal vibration is 10% or more, and a plurality of vibrators are arranged in the vertical periphery of the vertical-type object to be joined holding means. It consists of the method in any one of claim | item 1 -4. Item 1 is a composite vibration head in which the vibrator and the object-to-be-attached holding means have a longitudinal vibration ratio of 10% or more, and the plurality of vibrators are arranged in the vertical periphery of the vertical-type object-to-be-attached holding means. It consists of a joining apparatus in any one of -4.

  (Item 7) The method according to any one of Items 1 to 4, wherein the vibrator, the object-to-be-bonded holding unit, and the object to be bonded are bonded in a vertically arranged state. Moreover, it consists of the joining apparatus in any one of claim | item 1 -4 to which the said vibrator | oscillator, to-be-joined object holding means, and to-be-joined object were arranged vertically. As a head structure in a joining apparatus using these longitudinal vibrations, an efficient vibrator including a longitudinal vibration of 50% or more shown in FIG. 2, an object holding means, and an object to be joined are vertically arranged. There are types to join. Other than that, there are the following two types that swing the object holding means including longitudinal vibration of 10% or more. First, the method shown in FIG. 4 is a method in which the vibrator and the object holding means are of a capillary type. Also, the method shown in FIG. 3 is a method in which a plurality of vibrators are composite vibration heads arranged in the vertical periphery of the vertical object holding means.

  (Item 8) Hereinafter, a method and an apparatus in which a plurality of vibrators capable of bonding a large area such as a wafer in the bonding method and apparatus in Item 7 will be described in parallel. Among the holding tools that are to be bonded holding means for holding both the objects to be bonded to each other, bonding in which a plurality of piezo actuators that are the vibrators are in contact with or connected to the objects to be bonded of at least one holding tool Item 8. The method according to Item 7, wherein in the mechanism, both the objects to be bonded are contacted and pressurized, and longitudinal vibration is applied by the expansion and contraction operation of the piezo actuator. In addition, among the holding tools that are to be bonded holding means for holding both of the objects to be bonded to each other, a plurality of piezo actuators that are the vibrators are in contact with or connected to the surface to be bonded to the objects to be bonded of at least one holding tool. The joining apparatus according to Item 7, wherein the joining mechanism is configured to apply longitudinal vibration by joining and contracting operation of the piezo actuator in a state where both the objects to be joined are in contact with pressure. As a method for joining objects to be joined, a method for joining by applying ultrasonic vibration has been known. The term “vibration” as used herein refers to a vibration that includes an ultrasonic region from a low frequency, and is included in the present invention. Also, ultrasonic waves are often used for bonding, which is preferable. Further, it is preferable that a large energy can be output by resonating with the holding tool. Conventionally, a method of connecting a single vibrator in series is generally used, but by connecting a plurality of vibrators in parallel, energy can be increased and large-area vibration is possible. In addition, when a large area and a high load are applied, if the vibrator is singly received at the center, peripheral deflection occurs, and uniform vibration energy cannot be transmitted on the front surface. Therefore, it is possible to prevent deflection by arranging a plurality of piezoelectric actuators serving as vibrators in parallel, and to vibrate a large area with a high load under high load. In addition, what was conventionally only capable of two-dimensional movement can be subjected to a three-dimensional operation by receiving it at a plurality of locations in parallel. In addition, in the case of bonding by heating or in the case of bonding by surface activation, since the stress at the bonding interface is increased by applying vibration, bonding is performed with a bonding load of approximately half. This is because an increase in stress due to vibration contributes to the fact that the unevenness at the minute interface needs to be crushed and brought into close contact for bonding. In addition, in the case where the object to be bonded is a large area such as a wafer, a plurality of piezoelectric elements are provided on a surface opposite to the object to be bonded of at least one holding tool. In the joining mechanism in which the actuator is contacted or coupled, the above-described method is effective in which longitudinal vibration is applied and joined by the expansion / contraction operation of the piezo actuator in a state where both the objects to be joined are contacted and pressurized.

  (Item 9) The method according to item 8, wherein the number of piezoelectric actuators arranged is 3, and the piezoelectric actuators are arranged at equal intervals on the circumference. The number of piezoelectric actuators is 3, and the joining apparatus according to item 8 is arranged on the circumference at equal intervals. For example, the piezoelectric actuator serving as a vibrator is disposed at equal intervals from the center of the wafer, which is an object to be bonded, at equal intervals. It is preferable because it is easy. The minimum number is 3 to receive without tilting the surface. Moreover, 3 is preferable also when performing a three-dimensional operation | movement. The minimum number of three places on the circumference is efficient and stable.

  (Item 10) Item 8 or Item 9 in which the vibration phase between a plurality of piezoelectric actuators is controlled in a state in which both the objects to be bonded are in contact with each other and are expanded and contracted so that waves are sequentially generated in the rotation direction. It consists of the method. In addition, a means for controlling the vibration phase between the plurality of piezo actuators is provided, and the vibration phase between the plurality of piezo actuators is controlled in a state where both of the objects to be bonded are in contact with pressure so that the waves are sequentially generated in the rotation direction The joining apparatus according to Item 8 or 9, further comprising an oscillating means for joining by expanding and contracting. By controlling the vibration phase of the piezoelectric actuators arranged in parallel, a three-dimensional operation is possible. In particular, in the case where they are arranged at three positions at equal intervals on the circumference, if an expansion / contraction voltage composed of, for example, a sine curve is applied by the vibration applying means and the phase is shifted by 120 ° at three positions, a wave is sequentially generated in the rotation direction. Thus, a three-dimensional vibration operation can be performed. As described above, it is possible to remove voids generated from gaps in the interface that are generated even in the air and vacuum that are bitten at the time of operation when the operation is performed so that a wave like a wave is generated rather than simply longitudinal vibration. This can be done by extruding. In addition, since concentrated load sequentially flows in the joining, it is also effective for joining the minute irregularities based on the above principle. In particular, as compared with the case where the entire surface is evenly pressurized, it is easy to join with a small load by moving while applying a concentrated load to a certain portion. The vibration here includes such a three-dimensional continuous operation.

  (Item 11) The method according to any one of Items 8 to 10, wherein the surface of at least one holding tool is pressure-bonded with a convex shape at the center. Moreover, it consists of the joining apparatus in any one of claim | item 8 -10 which makes the center of the surface of at least one holding tool high convex. From the viewpoint of removing the void, the central convex shape that spreads from the center to the periphery, but since the void due to air entrainment is pushed away from the center during pressing, voids are unlikely to occur. In addition, the gaps in the vacuum are sequentially crushed from the center so that they are easily joined without wrinkling. The shape is preferably an R shape, which is a convex shape at the center that spreads from the center to the periphery and is shown as a gentle circumferential shape.

  (Item 12) The method according to Item 11, wherein the surface is resin-coated. The bonding apparatus according to Item 11, wherein the surface is coated with a resin. In the above description, it is preferable that the convex shape is made of an elastic body. From that viewpoint, coating with a resin is easy and preferable.

  (Claim 13) In a state where both the objects to be bonded are contacted and pressurized, the vibration phase between the plurality of piezo actuators is controlled, the expansion / contraction operation is performed so that the wave is sequentially generated in the rotation direction, and the amplitude is changed to perform the bonding. It consists of the method of claim | item 11 or claim | item 12. Further, a means for controlling the vibration amplitude between the plurality of piezo actuators is provided, and the vibration phase between the plurality of piezo actuators is controlled in a state where both the objects to be bonded are in contact with pressure so that the waves are sequentially generated in the rotation direction. The joining apparatus according to Item 11 or 12, wherein the joining device is joined by expanding and contracting and changing the amplitude. By shifting the above-mentioned phase, it can be operated as if a wave flows, and this is an R-shaped holding tool having a convex center and a smooth circumference, and the amplitude is also changed every other rotation while controlling the phase. By increasing in steps, a spiral trajectory can be drawn from the center to the periphery. The state is shown in FIG. It can be seen that the contact is shifted from the center to the periphery by increasing the amplitude. By doing so, voids can be removed and a single point concentrated load can be applied, so that a lower load and a higher load can be joined. In addition, it is possible to select a method such as gradually decreasing the increased amplitude or increasing it again after returning to the initial. The vibration here includes such a three-dimensional continuous operation.

  (Item 14) In a joining mechanism in which a pressure detection element is arranged on at least one of the holding tools, after applying pressure to detect the inclination between the holding tools with the pressure detection element and correcting the inclination with the piezoelectric actuator, Item 14. The method according to any one of Items 8 to 13, in which the vibration voltage is applied by using a value obtained by adjusting the output voltage of the piezoelectric actuator in parallel as a bias. In addition, in a joining mechanism with a plurality of pressure detection elements, where pressure detection elements are arranged on at least one of the holding tools, pressure is applied to detect the inclination between the holding tools, and the inclination is corrected by a piezo actuator. After that, in the joining apparatus for joining by applying vibration of the piezo actuator, any one of items 8 to 13 provided with a vibration applying means for applying the oscillating voltage with a value obtained by adjusting the output voltage of the piezo actuator in parallel. It consists of a joining apparatus of description. Since the surfaces need to be brought into close contact with each other as described above, parallel adjustment between the objects to be joined is also required on the submicron range. Also, if this parallelism is deviated, it will be displaced with high precision by forcibly changing it. In addition, when applying vibration, it is necessary to apply vibration after adjusting in parallel. In the present invention, parallel adjustment on a micron level can be performed by automatically performing parallel adjustment so that the pressure distribution is uniform by a plurality of pressure detection elements arranged in parallel. In addition, it is preferable that the pressure detection element is arranged in the same manner as the piezo actuator and arranged on the opposite surface or on the rear portion of the piezo because it is easy to control. When applying vibration, it is necessary to apply amplitude in a state of parallel adjustment. This can be achieved by applying a vibration voltage to each piezo actuator using a value obtained by adjusting the output voltage of the piezo actuator in parallel as a bias. In addition, since the amount of expansion and contraction of the piezo is limited to a few μm, it is necessary to use it efficiently.

  (Item 15) The method according to any one of Items 8 to 14, wherein in the joining process in which the longitudinal vibration is applied and joined, the pressurizing force and / or the vibration energy is increased by a rising curve. The joining apparatus according to any one of Items 8 to 14, further comprising: a vibration applying unit that increases a pressurizing force and / or vibration energy in a joining process in which the longitudinal vibration is applied and joined. The vibration energy is preferably increased in proportion to the contact area, and excess energy is generated because it causes damage. For this reason, as described above, the area where the minute unevenness at the interface closely adheres as bonding progresses, so by increasing the vibration energy with a curve that increases, optimal energy can be supplied without damage. be able to. In addition, since there is no excessive vibration, it is possible to achieve highly accurate positioned bonding on the submicron level without any positional deviation.

  (Item 16) The method according to any one of Items 8 to 15, wherein in the joining process in which the vibration is applied, the pressure during the vibration is detected by the pressure detecting means to control the vibration energy. Item 16. The item according to any one of Items 8 to 15, further comprising: a vibration application unit that detects vibration pressure and controls vibration energy by the pressure detection unit in the bonding process of applying the vibration and bonding. It consists of a joining device. By arranging a plurality of the first-stage pressure detection elements, it is possible to detect vibrations generated by the piezoelectric actuator. For example, when excessive vibration is applied, feedback control such as reducing vibration energy and amplitude may be performed if the pressure detection location is equal to or higher than a set peak value. Further, it is preferable in terms of control that the pressure detection element is disposed at the opposite position or the rear portion at the same position with respect to the position of the piezoelectric actuator.

  (Item 17) The method according to any one of items 8 to 16, wherein the bonding load is 300 MPa or less. Moreover, it consists of the joining apparatus in any one of claim | item 8 -16 term provided with the pressurization means whose said joining load is 300 Mpa or less. In normal temperature bonding as in Patent Documents 3 and 4, as shown in Table 1, a relatively soft metal, gold, required a pressure of 300 MPa or more. However, the addition of vibration reduced the load. It becomes possible. For example, joining at 150 MPa was possible.

  (Item 18) The method according to any one of Items 8 to 17, wherein the bonding is performed in a reduced pressure chamber. The bonding apparatus according to any one of Items 8 to 17, wherein the bonding is performed in a vacuum chamber. By joining under reduced pressure, it is possible to prevent the generation of voids due to entrainment of air or joining involving air especially during joining. Moreover, the means for supporting the decompression chamber and the holding tool is separated, and comprises the above-mentioned joining device having a sealing structure that can slide. When applying pressure or vibration, if it is connected to the chamber, it will be affected by the distortion of the chamber during evacuation. Moreover, since the same influence also occurs in the alignment accuracy, it is desirable to separate the means for supporting both holding tools and the decompression chamber while providing a sealing structure that can slide with an O-ring or a bellows.

  (Item 19) The method according to any one of Items 8 to 18, wherein one or more particles are on the bonding surface. The bonding apparatus according to any one of Items 8 to 18, wherein one or more particles are on the bonding surface. Particles that become small dust exist on the bonding surfaces of multiple objects to be bonded that are in close contact with each other, and when bonded as a solid layer at low temperatures, gaps are created around the particles and large voids are not bonded. . In order to remove this, by applying vibration at the time of joining, since stress concentrates on the particle part, it can be crushed or buried in the base material. Moreover, since what was joined in the vacuum can be joined as long as the gap is in contact, the gap can be brought into contact and joined by expansion and contraction due to vibration. A surface activated bonding surface is particularly effective.

(Item 20) The method according to any one of Items 1 to 19, wherein the bonding surfaces of both objects to be bonded are surface-activated by energy waves before the bonding, and then bonded in a solid layer. Further, the bonding apparatus according to any one of Items 1 to 19, further comprising energy wave irradiation means, wherein the bonding surfaces of both objects to be bonded are surface-activated by energy waves before the bonding and then bonded in a solid layer. . The surface activation treatment using energy waves refers to treatment that facilitates bonding by bringing the bonding interface into an activated state with an atomic beam, ion beam, or plasma. The bonding principle by surface activation can be considered as follows. In a substance such as a metal, deposits such as organic substances and oxide films on the surface are removed by etching to generate dangling bonds of active metal atoms on the surface, and the other dangling bonds are bonded to each other. In the case of an oxide containing Si, glass, SiO ² , or ceramic, the bonding surface is activated with OH groups and bonded with the other OH groups by a hydrophilic treatment with oxygen or nitrogen plasma. . In addition, uniform bonding and high-precision mounting have been achieved in room temperature bonding, but high pressure remains as a problem. Therefore, it consists of a method in which at least one of the bonding surfaces of the objects to be bonded is surface activated by energy waves in advance and the objects to be bonded are bonded using longitudinal vibration. As shown in Table 1, by applying ultrasonic vibration, it is possible to join at a pressure of 300 MPa to 150 MPa. Due to the longitudinal vibration, there is no problem of displacement, and joining is possible under a low load at room temperature. Further, since vibration is also applied to the bonded state, it is possible in the atmosphere even if the chamber structure is not particularly used as in Patent Documents 3 and 4. Even in the surface activation, if atmospheric pressure plasma is used, it can be entirely performed in the atmosphere. In addition, as shown in Patent Document 7, if the surface activation is performed by adsorbing OH groups to the bonding surface by oxygen plasma, the bonding can be performed in the air or in a vacuum even after exposure to the air. Subsequently, if the surface activated state is maintained in vacuum and bonded by vibration, there is no deposit and the surface is activated. Those that could not be joined can be joined. In addition, the bonding load can be reduced to a practical level of about 100 to 150 MPa, which is half or less than that of the conventional surface activated bonding. As an example in which the bonding weight can be reduced, a comparison is made between a case where gold bumps are bonded at room temperature as shown in Patent Document 3 and a case where bonding is performed by applying vibration. When gold metal protrusions are bonded, bonding cannot be performed unless they are crushed at a high pressure of about 300 MPa at room temperature. When this bump is on the surface of the semiconductor circuit, the circuit is generally damaged at 200 Mpa or more. When vibration was applied, bonding was possible with a load of 150 Mpa. It was also found that it was necessary to crush bumps of 1 μm or more as the bump crushing allowance. Further, as described above, even at the interface where voids are opened by particles or the like, the voids are brought into contact with each other by expansion and contraction due to vibration application, and the surface is activated. Further, the energy wave is a low-pressure plasma, and the cleaning is performed in a vacuum chamber having a reduced pressure. Further, the energy wave is a low-pressure plasma, comprising the low-pressure plasma irradiation means, and comprising the above-described bonding apparatus for cleaning in a vacuum chamber. Compared with the conventional room-temperature bonding, which cannot be bonded if there is even a slight reattachment, since vibration is used together, it is not necessary to have a high vacuum of about 10 ⁻⁸ to 10 ⁻⁵ Torr as in the room-temperature bonding, and it is simple. Since a low vacuum of about 10 ⁻² Torr is possible, a simple plasma can be used instead of an ion beam or an atomic beam that is not suitable for mass production. Since it is possible with a simple device, the cost of equipment can be reduced and simplified, making it suitable for mass production.

  (Item 21) The method according to Item 20, wherein the energy wave is atmospheric pressure plasma. Item 20. The bonding apparatus according to Item 20, wherein the energy wave irradiation unit is an atmospheric pressure plasma irradiation unit. If the plasma is atmospheric pressure plasma, it can be easily used in the atmosphere. Moreover, it is suitable for chemical treatment such as attachment of OH groups and nitrogen substitution.

  (Item 22) The method according to Item 20, wherein the energy wave is low-pressure plasma, and the cleaning step using the energy wave and the bonding step using longitudinal vibration are performed in the same chamber. Item 21. The joining apparatus according to Item 20, further comprising a decompression chamber and decompression means, wherein the energy wave irradiation means is a decompression plasma irradiation means, and the cleaning step using the energy wave and the joining step using longitudinal vibration are performed in the same chamber. If the plasma is a low-pressure plasma, the etching power is strong and impurities can be removed efficiently. In addition, since the bonding can be performed immediately after the surface activation treatment by performing in the same chamber, the bonding can be performed before the redeposition and activation decrease. Further, since handling of an object to be joined becomes unnecessary, adhesion of particles and the like can be prevented. The method according to item 20, wherein the contact is performed while irradiating the energy wave. Moreover, the energy which contacts while irradiating the said energy wave consists of a joining apparatus of claim | item 20 with an irradiation means. If bonding is performed while irradiating energy waves, the surfaces are cleaned and activated until just before contact, so that bonding is easier. In particular, activation requires bonding before dangling bonds disappear, and some materials disappear in a short time. Item 21. The semiconductor device according to Item 20 or 20, wherein at least one of the objects to be bonded is a semiconductor, and the bonding surface of each object to be bonded is cleaned with plasma composed of an RF plasma power source that switches between + and both electric fields or a plasma power source using a pulse wave. It consists of a method. Item 21. The apparatus according to Item 20, wherein at least one of the objects to be bonded is a semiconductor, and includes a plasma irradiation unit including an RF plasma power source or a pulsed wave plasma power source that switches a bonding surface of each object to + -both electric fields. It consists of a joining device. In addition, the RF plasma Vdc can be adjusted, or the pulse wave width can be adjusted. The bonding apparatus includes the plasma power source capable of adjusting the Vdc of the RF plasma or the plasma power source capable of adjusting the width of the pulse wave. When at least one of the objects to be bonded is a semiconductor, when + ions or −electrons collide with the circuit surface of the semiconductor, the circuit, particularly a gate oxide film, is charged up. In order to avoid this, it is possible to neutralize before charge is charged by colliding + ions and − electrons alternately. By doing so, it becomes possible to avoid charge-up damage. The alternating power source includes a method and a joining device in which the alternating power source is switched evenly from 1: 5. The charge-up damage can be reduced if the ratio of switching alternately is more than 1: 5. Moreover, it is more preferable if it is more equal than 1: 2. The alternating power supply includes a method and a bonding apparatus in which Vdc is a negative value and a positive region is 20% to 40%. Further, since Ar, oxygen plasma, and the like become + ions, in order to accelerate and collide with the cleaning surface and perform etching, the electrode that holds the object to be bonded needs to be a negative electric field. Therefore, the Vdc value is preferably −. Further, the method includes a plasma method and a bonding apparatus including an alternating power source capable of adjusting the Vdc value. If +-is made too uniform, the chance of + ions colliding decreases and the cleaning ability decreases. Also, charge-up damage due to electrons occurs. Therefore, by making it possible to adjust the optimum Vdc value for each application, the optimum cleaning ability can be exhibited without causing charge-up damage, which is effective. The alternating power supply includes a method and a bonding apparatus in which RF plasma is used. By using RF plasma consisting of alternating current as an alternating power source, it is possible to easily switch the electric field alternately between + and-. Further, the ratio of + and − can be easily adjusted by adjusting the Vdc value. The alternating power source includes a method and a bonding apparatus in which the alternating power source is a plasma composed of a pulse wave. A pulse wave can be used as an alternating power source. If it is a pulse wave, sharp rise and fall are possible, and the cleaning ability is also improved. In addition, the method includes a method and a bonding apparatus in which the pulse wave is plasma including an alternating power source capable of adjusting the + region time and the −region time. In addition to adjusting the Vdc value, by adjusting the pulse width and interval, it is possible to manage the rate of + − and the collision time, so that it is possible to set more finely than RF, which is alternating current, and it is easy to find the optimum value. Moreover, it consists of the method in any one of claim | item 20-claim | item 22 which heats within 180 degreeC at the time of the said joining. Moreover, it consists of the joining apparatus in any one of the claim | item 20 thru | or 22 provided with the heating means heated within 180 degreeC at the time of the said joining. The joint margin is increased by using heating at the time of joining. Also, it is possible to join those that could not be joined at room temperature. In particular, those with a short activation time re-attach quickly, and when used together with heating, the grain boundary diffusion at the joining interface is facilitated and joining becomes easy. In conventional low temperature bonding, since lead tin solder is 183 ° C., it is effective that bonding can be performed at a temperature lower than that. In addition, bonding at 150 ° C. or less and 100 ° C. or less is possible and preferable. Moreover, it is better if it is room temperature. In particular, gold is preferable because it is easy to bond at room temperature.

  (Item 23) Further, the method includes the method according to any one of Items 1 to 22, wherein the object to be bonded is provided with metal protrusions on at least one object to be bonded, and at least one object to be bonded is a semiconductor wafer or a chip. Item 22. The bonding apparatus according to any one of Items 1 to 22, wherein the object to be bonded is provided with metal protrusions on at least one object to be bonded, and at least one object to be bonded is a semiconductor wafer or a chip. The present invention is particularly suitable for the field of semiconductor chip mounting where high-precision mounting is desired because the lower metal portion of the metal projection portion that becomes a semiconductor electrode is susceptible to microcracks due to ultrasonic vibration. If the object to be joined is a semiconductor wafer or chip provided with bumps that serve as electrodes, the joint becomes a large number of protrusions, so ultrasonic bonding is performed sequentially on each bump as compared to surface bonding that bonds the entire area at once. Is suitable for vibration bonding.

  (Item 24) The method according to any one of Items 8 to 22, wherein the object to be bonded is a wafer bonded on a surface. Item 23. The bonding apparatus according to any one of Items 8 to 22, wherein the object to be bonded is a wafer bonded on a surface. In particular, when wafers are bonded to each other, there are 10 or more particles of 0.2 μm or more in a normal wafer, which is a value that is already in the catalog of ready-made products. Therefore, when the wafers are actually bonded to each other by a low temperature solid layer, voids having a size of about 10 mm remain in several places, so this method is particularly effective.

  (Item 25) A semiconductor device or a MEMS device including a wafer or a chip manufactured by the method according to any one of Items 1 to 24. In a MEMS device, bonding as a structure that does not use an adhesive is desired, and there is a high demand for surface bonding that does not use an adhesive that generates gas from a structure that seals an actuator portion. In addition, highly accurate positioning is required. Also, in semiconductor devices, there is a demand for bonding at low temperature from the problem of heat resistance and the bonding of electrodes at a fine pitch to the bonding in a normal state with high accuracy. The present invention is suitable for these devices.

In the above-described joining method and apparatus according to the present invention, in the joining apparatus for joining the objects to be joined by vibration, by using longitudinal vibration, uniform joining is obtained, and high accuracy without positional deviation is obtained. Implementation becomes possible. Moreover, damage can be reduced by setting the amplitude within 1 μm or attaching an elastic material to the tip of the object holding means. Further, in the normal temperature bonding by surface activation by energy waves, the present invention using the longitudinal vibration can solve the problem of high pressurization in the normal temperature bonding and can achieve high precision mounting within 1 μm. Further, the chamber structure is not required and bonding in the atmosphere is possible. The present invention is particularly suitable for the field of semiconductor chip mounting that is particularly easily damaged and requires high-precision mounting.

  Conventionally, a method of connecting one vibrator in series is generally used, but by connecting a plurality of vibrators in parallel, energy can be increased and large-area vibration can be achieved. Further, by arranging a plurality of piezoelectric actuators serving as vibrators in parallel, it is possible to prevent deflection and vibrate a large area with high energy under a high load. In addition, what was conventionally only capable of two-dimensional movement can be subjected to a three-dimensional operation by receiving it at a plurality of locations in parallel. This is effective for reducing the load and reducing voids in joining. In addition, this structure is effective for a large area requiring a high load such as a wafer to be handled mainly.

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an ultrasonic vibration bonding apparatus according to an embodiment of the present invention. In explaining the transmission of the ultrasonic vibration, the order of the objects to be joined from which the vibration is transmitted from the resonator side is referred to as first and second. In this embodiment, an apparatus for bonding the chip 20 as the first object to be bonded and the substrate 22 as the second object to be bonded is taken as an example. The joint surface of the chip 20 has a large number of metal protrusions 21 that are connection terminals. On the bonding surface of the substrate 22, metal pads 23, which are connection terminals, are arranged at positions facing the metal protrusions 21. The chip 20 is surface-mounted on the substrate 22 by bonding the chip-side metal protrusion 21 and the substrate-side metal pad 23 by ultrasonic vibration.
The ultrasonic vibration bonding apparatus roughly includes a vertical driving mechanism 25, a head unit 26, a bonding mechanism 27 including a stage 10 and a stage table 12, a position recognition unit 29, a gantry frame 13, a conveyance unit 30, and a control device 24. . The vertical drive mechanism 25 moves the head portion 26 up and down while being guided by the vertical guide 3 by the vertical drive motor 1 and the bolt / nut mechanism 2. The head portion 26 is guided in the vertical direction by the head escape guide 5, cancels its own weight, and detects the applied pressure while being pulled by the head weight counter 4 for pushing against the applied pressure detecting device 32. 32 and the vertical drive mechanism are grounded. The head portion 26 includes a workpiece holding means 7 that holds the chip 20 by suction, and a workpiece holding means holding portion 6 that holds the workpiece holding means in a manner that does not hinder the vibration of the workpiece holding means. Yes. Further, an article holding means heater 9 is embedded in the article holding means. The mounting mechanism 28 includes a stage 10 that holds the substrate 22 by suction, and a stage table 12 that has a movement axis for parallel movement and rotational movement for aligning the position of the chip and the substrate. A stage heater 11 is built in the stage 10. The mounting mechanism and the joining mechanism are connected by a gantry frame 13. The position recognizing unit 29 is inserted between the opposed chip and the substrate to move the upper and lower mark recognizing means 14 and the upper and lower mark recognizing means 14 to recognize the position recognition marks on the upper and lower chips and the substrate horizontally and / or vertically. It comprises a recognition means movement table 15 for movement. An amplitude detecting means 33 is provided at the tip of the upper and lower mark recognizing means 14 and can be moved to an arbitrary position by the recognizing means moving table 15 to measure a vibrating object. Moreover, when measuring the amplitude of both the 1st and 2nd to-be-joined objects, a some amplitude detection means may be provided. Further, when it cannot be installed at the tip of the upper / lower mark recognition means 14, it may be installed separately from the gantry frame 13. The transport unit 30 includes a substrate transport device 16 that transports the substrate 22, a substrate transport conveyor 17, a chip supply device 18 that transports the chips 20, and a chip tray 19. The control unit 31 includes overall control of the apparatus and an operation unit. Particularly in the pressure control, the torque of the vertical drive motor 1 is controlled by a signal from the pressure detection means 32 to control the pressure related to the joining.
Next, a series of operations will be described. The chip 20 is supplied from the chip tray 19 to the object holding means 7 by the chip supply device 18 and is sucked and held. The substrate 22 is supplied from the substrate transfer conveyor 17 to the stage 10 by the substrate transfer device 16 and held by suction. The upper and lower mark recognition means 14 is inserted by the recognition means moving table 15 between the chip 20 and the substrate 22 whose holding surfaces are opposed to each other, and the alignment marks of the opposing chip 20 and substrate 22 are positioned by the upper and lower mark recognition means 14. recognize. Using the stage 20 as a reference, the position of the substrate 22 is aligned and moved in the direction of parallel movement and / or rotational movement by the stage table 12. In a state where both the joining positions are aligned, the head portion 26 is lowered by the vertical drive mechanism 25, and the chip 20 and the substrate 22 are grounded. The position of the head portion 26 in the height direction is detected by the head height detecting means 24. The contact timing of the chip 20 and the substrate 22 is detected by the pressure detection means 32, and the vertical drive motor is switched from position control to torque control. Ultrasonic welding is started in a state in which a constant pressure is applied between the workpieces by the torque of the motor. The head height is monitored by the head height detecting means 24 even during joining which is switched to torque control. After the ultrasonic bonding is completed, the suction of the chip 20 is released and remains on the stage with the chip 20 mounted on the substrate 22 side. This is again discharged to the substrate transfer conveyor 17 by the substrate transfer device 16 and the series of operations is completed.
Further, in the joining process, the amplitude of the vibrating object is measured by the amplitude detecting means 33, and the ultrasonic vibration energy is controlled so as to become the target value, or the applied pressure and / or the ultrasonic vibration energy proportional to the joining area is increased. Let The object holding means, the first object to be bonded, and the second object to be bonded can be measured as measurement points of the vibrating object. Further, the bonding area can be estimated from the amplitude of the vibrating object because the applied pressure and ultrasonic vibration energy at that time are known.

In the case where the bonding surface is cleaned in advance with energy waves and activated and bonded, as shown in Patent Document 3 and Patent Document 4, the apparatus of FIG. 1 is covered with a chamber and a cleaning unit is provided. Become. In addition, since the ultrasonic wave is applied to the bonded state, it is possible in the atmosphere without using a chamber structure. Even in cleaning, if atmospheric pressure plasma is used, all can be performed in the atmosphere.
When this method is particularly suitable, the object to be bonded is provided with metal protrusions on at least one object to be bonded, and at least one object to be bonded is a semiconductor chip. The lower metal part of the metal projection that becomes the semiconductor electrode is easily damaged by microcracks due to ultrasonic vibration. Further, a high mounting accuracy within 1 μm is required. Therefore, this method is particularly suitable.
As a head structure in the joining apparatus using these longitudinal vibrations, there is an efficient type including a vibrator, an object holding means, and an object to be joined that are vertically arranged including 50% or more of the longitudinal vibration shown in FIG. is there. Other than that, the following two types can be used as the type for swinging the object holding means including 10% or more of longitudinal vibration. First, the vibrator and the object holding means shown in FIG. 4 have a capillary type structure. Moreover, it consists of a structure which is a composite type vibration head shown in FIG. 3 in which a plurality of vibrators are arranged in the vertical periphery of the vertical type object holding means.
Although the embodiment of the chip and the substrate has been described as an embodiment, the object to be bonded may be a material other than a semiconductor. In addition, gold, Al, copper, and the like are suitable for the joint, but any other metal or other metal may be used as long as it can be joined by ultrasonic vibration.
As the energy wave, as shown in Patent Document 3 and Patent Document 4, any of plasma, ion beam, atomic beam, radical beam, and laser can be used. It also includes plasma cleaning in the atmosphere. In addition, since the vibration is applied to the bonding state, it is possible in the atmosphere even without using a chamber structure.
In addition, since the vibration is applied to the bonding state, it is possible in the atmosphere even without using a chamber structure. Even in cleaning, if atmospheric pressure plasma is used, all can be performed in the atmosphere.
The elastic material is attached to the tip of the object holding means, but the attachment method may be any method such as adhesion or coating. In addition, the present invention includes a case where it is attached to the surface of the first object to be bonded or a case where it is supplied as a sheet or the like between the object holding means and the first object to be bonded.
Patent Document 5 shows an example in which an interference member is inserted between an ultrasonic horn and a chip, but this only absorbs thickness variations and inclinations of the first and second objects to be joined. Similar to Patent Document 1 and Patent Document 2, the structure mainly includes lateral vibration and does not absorb longitudinal vibration.
The chip may be in any form such as a chip or a wafer. The metal protrusions may have a plurality of independent shapes, or may have a connected shape confining a certain region. Further, the entire surface may be a bonding surface.
The bonded object holding means side of the bonded objects to be bonded is referred to as a first bonded object and the stage side is referred to as a second bonded object. Two or more objects to be joined may be overlapped and joined.
In order to obtain the amplitude between the first and second objects to be bonded, it is preferable to provide a plurality of amplitude detecting means and measure simultaneously, but the first and second objects to be bonded in order by one amplitude detecting means. After measuring an object, the amplitude difference on the same time axis can also be calculated. If the first and second objects to be joined are thin and it is difficult to provide a plurality of amplitude detecting means from one side, they can be individually set from both sides.

A preferred second embodiment of the present invention will be described below with reference to the drawings. FIG. 6 shows a joining apparatus for joining by applying vibration in a reduced pressure after surface activation according to an embodiment of the present invention. In this embodiment, the apparatus is exemplified as an apparatus for bonding an upper wafer as a first object to be bonded and a lower wafer as a second object to be bonded.

  First, the apparatus configuration will be described. A holding tool 125 for holding an upper wafer, which is a part of the head 107, and a stage 108 for holding a lower wafer are arranged in a decompression chamber 111, and the head is a Z-axis lifting mechanism 102 to which a torque-controlled lifting drive motor 101 is connected. And an XY alignment table 106 for aligning the head portion in the XY horizontal direction, and an X, Y, θ direction alignment moving means and a Z direction elevating means. By feeding back the applied pressure detected by the pressure detecting means 104 arranged in the holding tool holding unit 124 to the torque-controlled lifting drive motor 101, position control and pressure control can be performed while switching. ing. Further, as shown in FIGS. 8, 10 and 11, the pressure detecting means 104 has three pressure detecting elements 131 arranged at equal intervals on the circumference, and can be used for parallel adjustment of the holding tool, or to apply vibration. Also used for measuring amplitude during pressure. When it is used for head load control, it feeds back to the servo motor with three totals. Moreover, it can utilize also for the contact detection of to-be-joined objects. The XY alignment table 106 uses means that can be used even in a vacuum. However, since the Z and θ axis mechanisms are installed outside the decompression chamber, the head portion and the outside are movably blocked by the bellows 105. The stage 108 can be slid by the slide moving means 129 between the joining position and the standby position. A high-precision guide and a linear scale for recognizing the position are attached to the slide moving means, and the stop position between the joining position and the standby position can be maintained with high precision. In addition, the moving means is built in the decompression chamber, but it is possible to place a cylinder, linear servo motor, etc. outside by disposing the moving means outside and connecting them with a packed connecting rod. It is. Alternatively, a ball screw can be placed in a vacuum and a servo motor can be installed outside. The moving means may be any moving means. The head and stage to-be-bonded object holding means may be a mechanical chucking method, but is preferably provided with an electrostatic chuck. In addition, a heater for heating is provided and serves as a plasma electrode, and has three functions of holding means, heating means, and plasma generating means.

  As shown in FIGS. 8, 10, and 11, at least one of the holding tools is provided with three piezoelectric actuators 130 on the circumference for parallel adjustment. In addition, since the head unit also uses vibration including an ultrasonic region at the time of joining, the head 107 includes a holding tool holding unit 124, a holding tool 125, and a vibrator 126, and vibrations from the vibrator are transmitted to the holding tool to vibrate. Is transmitted to the workpiece to be held by the holding tool. As shown in FIG. 8, piezo actuators 130 serving as vibrators are arranged in parallel at equal intervals on three circumferences, and the wave operation and amplitude in which waves flow by controlling the phase are increased and decreased. A three-dimensional operation such as an operation can be performed. The holding tool holding unit includes a holding tool and a means for holding the vibration so as not to kill the vibration of the vibrator. Further, it is preferable to control the applied pressure in proportion to the bonding area as the bonding proceeds. In addition, when bonding a large area such as a wafer, it is impossible for a transverse vibration type vibration head to have a large bonding area in order to cause a lateral vibration. Surface bonding is also possible.

  As the decompression means, a vacuum pump 117 is connected to the exhaust pipe 115, and opening and closing and flow rate adjustment are performed by the exhaust valve 116, so that the degree of vacuum can be adjusted. On the intake side, an intake gas switching valve 120 is connected to the intake pipe 118, and opening / closing and flow rate adjustment are performed by the intake valve 119. As the suction gas, two kinds of plasma reaction gases can be connected, and for example, Ar and oxygen or oxygen and nitrogen can be connected. The other is connected to the atmosphere or nitrogen for release. The degree of vacuum and the reaction gas concentration can be adjusted to optimum values by adjusting the flow rate including opening and closing of the intake valve 119 and the exhaust valve 116. Moreover, automatic feedback can be performed by installing a vacuum pressure sensor in the decompression chamber.

  An alignment mark recognizing unit comprising an alignment optical system is disposed outside the decompression chamber above the stage standby position and below the head. The number of recognition means should be at least one on the stage and head side. If a small object such as a chip is to be recognized, the shape of the alignment mark can also read the θ direction component and two marks within one field of view. Although it is possible to read sufficiently even with one recognition means by arranging, it is possible to read with high accuracy in the θ direction when two large ones in the radial direction such as a wafer are arranged at both ends as in this embodiment. It is preferable because it is possible. Further, the recognition means may be provided with means that can move in the horizontal direction or the focal direction so that the alignment mark at an arbitrary position can be read. The recognition means is a camera with an optical lens made of, for example, visible light or IR (infrared) light. A window made of a material, for example, glass, that can be transmitted through the optical system of the recognition means is disposed in the decompression chamber, and the alignment mark of the object to be bonded in the decompression chamber is recognized through the window. For example, alignment marks are provided on the surfaces of the upper wafer and the lower wafer facing each other on the object to be bonded so that they can be recognized with high positional accuracy. The alignment mark preferably has a specific shape, but a part of a circuit pattern or the like provided on the wafer may be used. Further, when there is no mark, an outline such as an orientation flat can be used. Both alignment marks on the upper and lower wafers are read at the stage standby position, the stage is moved to the bonding position, and the alignment is moved in the X, Y, and θ directions on the head side. In order to reflect the reading result of the standby position at the joining position, it is necessary to have an accuracy so that the relative movement distance vectors of the standby position of the stage and the joining position are repeatedly the same. For this reason, a guide having a high repeatability is used, and a linear scale that reads position recognition on both sides with high accuracy is arranged. If the linear scale is fed back to the moving means to improve the stopping position accuracy and the moving means is a simple cylinder or backlash like a bolt / nut mechanism, the linear scale should be Therefore, it is possible to easily achieve high accuracy by making corrections by taking into account when the head-side alignment moving means is moved. For fine alignment with high accuracy at the nano level, after rough positioning, the head side recognition means is used for both visible light and IR (infrared) with the upper wafer and lower wafer close to about a few μm. By using a recognition means and providing a transmission hole or transmission material at the position of the alignment mark on the stage, the alignment mark on both wafers is transmitted through the stage from the bottom and transmitted through the infrared rays, and is simultaneously recognized. , Θ direction can be aligned. When the recognition means has a movement means in the focal direction, it can be recognized separately in the upper and lower directions, but it is more preferable in terms of accuracy to make the recognition close and simultaneously recognize. When fine alignment is performed, accuracy can be improved by repetitive alignment. In addition, since the θ direction is affected by the runout, the accuracy is reduced to the nano level by performing alignment only in the XY direction after entering within a certain range. It can be improved. By using a sub-pixel algorithm as an image recognition means, it is possible to obtain recognition accuracy that is higher than the infrared resolution. In addition, if they are aligned close to each other, the amount of Z movement required at the time of bonding will be within a minimum of a few μm, so the backlash and inclination with respect to Z movement can be kept to a minimum and high-precision nano-level alignment accuracy is achieved. Can be achieved.

Next, the operation flow will be described with reference to FIG. First, as shown in FIG. 1, the upper wafer and the lower wafer are held on the stage and the head while the front door of the decompression chamber is opened. This may be done manually, but may be automatically loaded from the cassette. Next, as shown in 2, the front door is closed and the pressure in the vacuum chamber is reduced. In order to remove impurities, the pressure is preferably reduced to 10 ⁻³ Torr or less. Subsequently, as shown in 3 and 4, for example, Ar, which is a plasma reaction gas, is supplied, and a plasma power source is applied to the plasma electrode at a certain degree of vacuum, for example, about 10 ⁻² Torr to generate plasma. The generated plasma ions collide toward the surface of the wafer held on the power source side, and surface deposits such as an oxide film and an organic layer are etched to activate the surface. Alternatively, oxygen or nitrogen can be used as a reactive gas to make the surface hydrophilic, and the surface can be activated by OH groups. Both wafers can be cleaned at the same time, but can also be cleaned alternately by switching one matching box. Subsequently, as shown in 5, the alignment marks on the upper and lower wafers are read in vacuum by the recognition means on the head side and the stage side at the stage standby position to recognize the positions. Subsequently, as shown in 6, the stage slides to the joining position. The relative movement between the recognized standby position and the sliding joint position at this time is performed with high accuracy using a linear scale. When nano-level high accuracy is required, the process shown in 7 is added. After rough positioning, visible light and IR (infrared) recognition means are used as the head side recognition means with the upper wafer and the lower wafer brought close to each other by several μm. By providing a hole and a transmission material, the alignment marks on both wafers can be simultaneously recognized through the stage from below, and alignment in the X, Y, and θ directions can be performed again. In this case, it is possible to improve accuracy by repeatedly aligning, and the θ direction is affected by the runout, so after entering within a certain range, the accuracy can be improved to the nano level by performing alignment only in the XY direction. . Subsequently, as shown in FIG. 8, the head is lowered, both the wafers are brought into contact with each other, and pressure is switched from position control to pressure control. In a state where the contact is detected by the pressure detection means and the height position is recognized, the value of the pressure detection means is fed back to the torque control type lifting drive motor to control the pressure so as to become the set pressure. In a state where initial pressurization is applied, first, parallel adjustment is performed between the upper and lower workpieces by a piezo actuator so that the values of the pressure elements arranged at equal intervals on the circumference are uniform. If high-precision positioning is required, parallel adjustment can be performed in advance before surface activation, and the value can be stored and contacted in a state of parallel adjustment. Next, arbitrary vibration including the three-dimensional operation as described above is applied, and the stress at the bonding interface increases, so that the bonding proceeds with a low load. It is preferable to increase the applied pressure in proportion to the increase in the bonding area. In addition, there are particles that become small dust on the bonding surface of objects to be bonded that are in close contact with each other like a wafer, and when bonded as a solid layer at low temperature, gaps are created around the particles, and large voids and Will not be joined. In order to remove this, by applying vibration at the time of joining, since stress concentrates on the particle part, it can be crushed or buried in the base material. In addition, by applying vibration to the gap formed by the gap at the interface, the interface is already activated by bringing the gap into contact with the gap, thereby reducing the voids. The surfaces cannot be joined by ultrasonic vibration, but since the joining force is joined by surface activation, the vibration is used to pulverize and / or bury the particles and to contact the voids. Since it is in a vacuum, it can be joined without a gap if there are no particles. Further, heating is applied at the time of joining as necessary. In addition, in the case of heating after vibration bonding in order to remove residual stress or increase bonding strength, heating can be performed in a state where accuracy is maintained by raising the temperature after contacting at normal temperature. Subsequently, as shown in 9, the head side holding means is released and the head is raised. Subsequently, as shown at 10, the stage is returned to the standby position, and the inside of the decompression chamber is released to the atmosphere. Subsequently, as shown at 11, the front and rear wafers are taken out by opening the front door. Although it may be manual, it is preferable to automatically unload the cassette.

  In the above embodiment, the wafer is raised as the object to be bonded, but it may be a chip and a substrate. As long as the bonding area is large, such as a wafer, the object to be bonded is not limited to a wafer, a chip, and a substrate, and may have any shape.

  Separately from the head, the vibration head is placed between the stage standby position and the head position, aligned, and after the upper and lower objects are mounted on the head, the stage is moved and pressurized from above by the vibration head. Alternatively, bonding may be performed by applying vibration. By doing so, the means for holding the object to be joined by the holding tool and the plasma electrode function become unnecessary, and the design of the holding tool becomes easy.

  Further, plasma cleaning may be performed with another apparatus, and only bonding may be performed with this apparatus. In that case, the means for moving the stage to the standby position becomes unnecessary.

  The holding means for the object to be joined is preferably an electrostatic chuck method, but may be a mechanical chucking method. In addition, a method of mechanically chucking after first vacuum-sucking and adhering in the atmosphere is preferable because adhesion is improved.

  In the embodiment, the head side has an alignment moving means and a lifting shaft, and the stage side has a slide shaft. However, the alignment moving means, the lifting shaft, and the slide shaft may be combined in any way on the head side and the stage side. It may be duplicated. Further, even if the head and the stage are not arranged vertically, it does not depend on the arrangement direction, such as left and right arrangement or diagonal.

  When plasma cleaning is performed while the stage is slid, the electric field environment is similar because the electrode shape of the head and the stage and the surrounding shape are similar. Therefore, the matching box for automatically adjusting the plasma power source can be switched to the head side and the stage side sequentially by switching the electrodes by one without using an individual one. By doing so, compactness and cost reduction can be achieved.

  The vibration frequency may not be in the ultrasonic region. Especially in the case of the longitudinal vibration type, the effect is sufficiently exhibited even at a low frequency.

  In this example, the surface activation by Ar plasma was increased, but plasma was used with oxygen or nitrogen as a reaction gas, the surface was activated with OH groups by hydrophilization, hydrogen-bonded, and strongly eutectic by heating. Bonding methods can also be used. This method is particularly effective for oxides including Si, glass, SIO2, and ceramics.

  As shown in FIG. 11, it is arranged to be held on the same side as the piezo actuator, but when the pressure detecting element is arranged on the stage side facing the piezo actuator as shown in FIG. It is preferable because it is possible. Further, as shown in FIG. 10, the piezoelectric actuator and the pressure detection arrangement may be reversed. Also, as shown in FIG. 10 and FIG. 11, the support is connected with a support and the support is sealed with an O-ring, and the pressure detection element is arranged outside the decompression chamber, so that it is not subject to drift due to temperature change, so that it can be detected with high accuracy. it can.

  As the timing of parallel adjustment, a value adjusted in advance can be held. Further, it can be performed more precisely by performing parallel adjustment at each contact or by correcting at the time of pressurization. In addition, when it is necessary to align with high accuracy, it is preferable to perform parallel adjustment before alignment. Moreover, when joining by surface activation, it is necessary to adjust in parallel before surface activation processing.

It is a schematic block diagram of the vibration joining apparatus which concerns on one embodiment of this invention. FIG. 4 is a structural diagram of an ultrasonic head that joins a vibrator, a workpiece holding means, and a workpiece to be bonded in a vertically arranged state. It is an ultrasonic head structure figure which is a compound type vibration head with which a plurality of vibrators are arranged in the vertical periphery of a vertical type object holding means. FIG. 3 is a structural diagram of an ultrasonic head in which a vibrator and a workpiece holding means are of a capillary type. It is an interface stress analysis figure for joining by longitudinal vibration and lateral vibration of a metal projection bump. Vibration pressure bonding equipment configuration diagram Joining operation flow chart Pressure sensing element and piezo actuator layout Uzumaki type vibration operation flow chart Pressure sensing element and piezoelectric actuator layout part 2 Pressure sensing element and piezo actuator layout 3

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vertical drive motor 2 Bolt / nut mechanism 3 Vertical guide 4 Head self-weight counter 5 Head escape guide 6 Bonded object holding means holding part 7 Bonded object holding means 8 Vibrator 9 Bonded object holding means heater 10 Stage 11 Stage heater 12 Stage table 13 Mounting frame 14 Vertical mark recognition means 15 Recognition means moving table 16 Substrate transport device 17 Substrate transport conveyor 18 Chip supply device 19 Chip tray 20 Chip 21 Metal protrusion 22 Substrate 23 Metal pad 24 Head height detection means 25 Vertical drive mechanism 26 Head part 27 Joining mechanism 28 Mounting mechanism 29 Position recognition part 30 Conveying part 31 Control device 32 Pressure detection means 33 Amplitude detection means 34 Elastic material

101 Torque Control Type Elevating Drive Motor 102 Z Axis Elevating Mechanism 103 θ Axis Rotating Mechanism 104 Pressure Detection Unit 105 Bellows 106 XY Alignment Table 107 Head 108 Stage (Plasma Electrode, Heater, Holding Unit)
109 Lower wafer 110 Upper wafer 111 Depressurization chamber 112 Head side wafer recognition camera 113 Stage side wafer recognition camera 114 Glass window 115 Exhaust pipe 116 Exhaust valve 117 Vacuum pump 118 Intake pipe 119 Intake valve 120 Intake gas switching valve 121 Ar
122 O2
123 Atmosphere 124 Holding tool holder 125 Holding tool (plasma electrode, heater, holding means)
126 Vibrator 127 Upper alignment mark 128 Lower alignment mark 129 Slide moving means 130 Piezo actuator 131 Pressure detecting element 137 Post

Claims (50)

A plurality of stacked objects to be joined are pressed and held between the head and the stage, which are the objects to be joined in the joining mechanism, and are held from the vibrator coupled to the objects to be joined. A method of joining objects to be joined using longitudinal vibration in a joining apparatus that transmits vibrations to means and applies vibrations to a plurality of joined objects to be joined. The method according to claim 1, wherein an amplitude of the vibration is 1 μm or less. The method according to claim 1 or 2, wherein the object is held on at least one of the objects to be bonded or the supporting member via an elastic body. A joining mechanism having the same longitudinal vibration direction and pressurizing direction has a pressurizing means that can move in the pressurizing direction at the time of joining, and is controlled to pressurize at a constant pressure while being movable in the longitudinal vibration direction during vibration application. Item 4. The method according to any one of Items 1 to 3. The method according to any one of claims 1 to 4, wherein the vibrator and the object-to-be-joined holding means are of a capillary type in which a ratio of longitudinal vibration is 10% or more. The vibrator and the object-to-be-bonded holding means are composite vibration heads in which the ratio of longitudinal vibration is 10% or more, and the plurality of vibrators are arranged in the vertical periphery of the vertical-type object to be bonded holding means. 5. The method according to any one of 4. The method according to claim 1, wherein the vibrator, the workpiece holding means, and the workpiece are joined in a vertically arranged state. Among the holding tools that are to be bonded holding means for holding both the objects to be bonded to each other, bonding in which a plurality of piezo actuators that are the vibrators are in contact with or connected to the objects to be bonded of at least one holding tool The method according to claim 7, wherein in the mechanism, the longitudinal vibration is applied by the expansion and contraction operation of the piezo actuator in a state where both the objects to be bonded are in contact and pressure. The method according to claim 8, wherein the number of piezoelectric actuators arranged is 3, and the piezoelectric actuators are arranged at equal intervals on the circumference. 10. The method according to claim 8, wherein, in a state where both the objects to be bonded are in contact and pressure, the vibration phase between the plurality of piezoelectric actuators is controlled, and the members are bonded by extending and contracting so that waves are sequentially generated in the rotation direction. The method according to any one of claims 8 to 10, wherein the surface of at least one holding tool is pressure-bonded with a convex shape having a high center. The method of claim 11, wherein the surface is resin coated. 12. In a state where both of the objects to be joined are contacted and pressurized, a vibration phase between a plurality of piezo actuators is controlled, an expansion / contraction operation is performed so that a wave is sequentially generated in a rotation direction, and an amplitude is changed to join. 13. The method according to any one of 12. In a joining mechanism in which a pressure detection element is arranged on at least one of the holding tools, pressure is applied, the inclination between the holding tools is detected by the pressure detection element, the inclination is corrected by the piezoelectric actuator, and then the vibration of the piezoelectric actuator is applied. The method according to any one of claims 8 to 13, wherein in the joining method, the oscillating voltage is applied with a value obtained by adjusting the output voltage of the piezoelectric actuator in parallel as a bias. The method according to any one of claims 8 to 14, wherein in the joining process in which the longitudinal vibration is applied and joined, the pressurizing force and / or the vibration energy is increased by a curve that rises. The method according to any one of claims 8 to 15, wherein in the joining process in which the vibration is applied and joined, the pressure at the time of vibration is detected and the vibration energy is controlled by the pressure detecting means. The method according to any one of claims 8 to 16, wherein the bonding load is 300 Mpa or less. The method according to claim 8, wherein the joining is performed in a vacuum chamber. The method according to claim 8, wherein one or more particles are on the bonding surface. The method according to any one of claims 1 to 19, wherein the bonding surfaces of both objects to be bonded are surface-activated by energy waves before the bonding, and then bonded in a solid layer. 21. A method according to any of claims 20 wherein the energy wave is atmospheric pressure plasma. 21. The method according to claim 20, wherein the energy wave is low-pressure plasma, and the cleaning process using the energy wave and the bonding process using longitudinal vibration are performed in the same chamber. The method according to any one of claims 1 to 22, wherein the object to be joined comprises a semiconductor wafer or a chip provided with a plurality of minute bumps. The method according to any one of claims 8 to 22, wherein the object to be bonded comprises a wafer bonded on a surface. 25. A semiconductor device or MEMS device comprising a wafer or chip made by the method of claim 1-24. A plurality of stacked objects to be bonded are held between the head and the stage, which are the objects to be bonded holding means in the bonding mechanism, by pressure, and held by the vibrator coupled to the objects to be bonded holding means. A joining device for joining a workpiece using longitudinal vibration in a joining device for transmitting vibration to a means and applying vibration to a plurality of stacked workpieces to be joined. 27. The bonding apparatus according to claim 26, further comprising an oscillating unit that sets an amplitude of the vibration to 1 μm or less. 28. The joining apparatus according to claim 26 or 27, wherein at least one object to be joined holding means or a supporting member thereof has an elastic body and holds the elastic body through the elastic body. In a joining mechanism with the same longitudinal vibration direction and pressurizing direction, it has a pressurizing means that can move in the pressurizing direction during joining, and pressurization control is performed with a constant pressure while being movable in the longitudinal vibration direction during vibration application. The joining apparatus according to any one of claims 26 to 28, further comprising a pressure unit. 30. The joining apparatus according to any one of claims 26 to 29, wherein the vibrator and the object to be joined holding means are of a capillary type in which a ratio of longitudinal vibration is 10% or more. 27. The vibrator / bonded object holding means is a composite vibration head in which a ratio of longitudinal vibration is 10% or more, and a plurality of vibrators are arranged in the vertical periphery of the vertical bond object holding means. 29. The joining apparatus according to any one of 29. 30. The bonding apparatus according to claim 26, wherein the vibrator, the workpiece holding means, and the workpiece are arranged vertically. Two holding tools to be bonded holding means for holding both of the bonded objects facing each other, a lifting shaft for moving and pressing at least one holding tool in the pressure axis direction, a plurality of piezo actuators, and a plurality of piezos A plurality of piezo actuators serving as the vibrators are in contact with or coupled to the surface of the holding tool that holds both of the objects to be bonded, facing the object to be bonded, out of the holding tool that holds the objects to be bonded to each other. 33. The joining apparatus according to claim 32, wherein in the joined mechanism, the longitudinal vibration is applied by the expansion and contraction operation of the piezo actuator in a state where both the objects to be joined are contact-pressed. 34. The joining apparatus according to claim 33, wherein the number of piezoelectric actuators arranged is 3, and the piezoelectric actuators are arranged at equal intervals on the circumference. A means for controlling the vibration phase between a plurality of piezo actuators is provided, and the vibration phase between the plurality of piezo actuators is controlled in a state where both the objects to be bonded are in contact with pressure, so that a wave is sequentially generated in the rotation direction. The joining apparatus according to claim 33 or 34, further comprising an oscillating means for operating and joining. 36. The joining device according to any one of claims 33 to 35, wherein at least the surface of the one holding tool has a convex shape with a high center. The joining apparatus according to claim 36, wherein the surface is coated with a resin. A means for controlling the vibration amplitude between a plurality of piezo actuators is provided, and the vibration phase between the plurality of piezo actuators is controlled in a state in which both the objects to be bonded are in contact with pressure so that the waves can be sequentially stretched in the rotation direction. 38. The joining apparatus according to claim 36 or 37, wherein the joining is performed while the amplitude is changed. In a joining mechanism that includes a plurality of pressure detection elements and the pressure detection elements are arranged on at least one of the holding tools, after applying pressure to detect the inclination between the holding tools with the pressure detection element and correcting the inclination with a piezo actuator 39. The bonding apparatus according to any one of claims 33 to 38, further comprising: a vibration applying unit that applies a vibration voltage using a value obtained by adjusting the output voltage of the piezoelectric actuator in parallel as a bias in the bonding apparatus that performs bonding by applying vibration of the piezoelectric actuator. Joining device. 40. The joining apparatus according to any one of claims 33 to 39, further comprising vibration applying means for increasing a pressurizing force and / or vibration energy in a joining process for joining by applying the longitudinal vibration. The joining apparatus according to any one of claims 33 to 40, further comprising vibration applying means for detecting vibration pressure and controlling vibration energy by the pressure detecting means in the joining process in which the vibration is applied. . The joining apparatus according to any one of claims 33 to 41, further comprising a pressurizing unit having a joining load of 300 MPa or less. The joining apparatus according to any one of claims 33 to 42, wherein the joining is performed in a reduced pressure chamber. 44. The joining apparatus according to claim 43, wherein means for supporting the decompression chamber and both holding tools are separated and have a sealing structure capable of sliding. 45. The joining apparatus according to claim 33, wherein one or more particles are on the joining surface. 46. The joining apparatus according to any one of claims 26 to 45, further comprising energy wave irradiation means, wherein the joining surface of at least one object to be joined is activated in advance by energy waves before the joining and then joined in a solid layer. . 47. The bonding apparatus according to claim 46, wherein the energy wave irradiation unit is an atmospheric pressure plasma irradiation unit. 47. The joining apparatus according to claim 46, comprising a decompression chamber and decompression means, wherein the energy wave irradiation means is a decompression plasma irradiation means, and the cleaning step using the energy wave and the joining step using longitudinal vibration are performed in the same chamber. The bonding apparatus according to any one of claims 26 to 48, wherein the object to be bonded is provided with a metal protrusion on at least one object to be bonded, and at least one of the objects to be bonded is a semiconductor wafer or a chip. 49. The bonding apparatus according to any one of claims 33 to 48, wherein the object to be bonded includes a wafer bonded on a surface.

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