Implementation structure and method for manufacturing the same

Abstract

This provides a mounting structure that allows for a greater tolerance for misalignment during mounting while ensuring strong bonding. [Solution] The mounting structure 9 comprises a first member U1 having a first electrode pad 2 and a metal bump 4 formed on its surface, and a second member U2 having a second electrode pad 7 and a second insulating layer 8. An oxide film 5 is formed on the surface of the metal bump 4. At the location where the metal bump 4 and the second electrode pad 7 come into contact, a metal joint portion 4a is formed where the metal constituting the metal bump 4 and the metal constituting the second electrode pad 7 are joined together. At the location where the oxide film 5 and the second insulating layer 8 come into contact, an oxide film joint portion 5a is formed where the oxide film 5 and the second insulating layer 8 are joined together.

Description

Technical Field

[0001] The present disclosure relates to a mounting structure obtained by joining a metal bump provided on a first member and a second electrode pad provided on a second member, and a method for manufacturing the same.

Background Art

[0002] In recent years, the density of semiconductor devices has been increasing and the number of electrode terminals has been increasing, and the pitch of electrode terminals provided on semiconductor devices has been reduced and the area of electrode terminals has been reduced. As one of the mounting technologies for mounting narrow-pitch terminals on a mounting substrate of a semiconductor device, flip-chip mounting is known.

[0003] In flip-chip mounting, protruding electrodes formed on electrode terminals of semiconductor devices such as system LSIs, memories, and CPUs are pressure-bonded and heated to electrode pads of a mounting substrate such as a circuit board or a wiring board.

[0004] Among the protruding electrodes formed on the electrode terminals, solder bumps are widely adopted. As a method for forming solder bumps in a protruding shape on the electrode terminals, for example, screen printing, dispensing, or electroplating is known. After solder is formed on the electrode terminals by these methods, the semiconductor device and the mounting substrate are heated in a reflow furnace to a temperature above the melting point of the solder to join the protruding electrodes and the electrode pads.

[0005] However, during bonding, since the solder is in a liquid state, as the pitch of the electrode terminals is reduced, short circuits between the terminals due to the solder are likely to occur. Therefore, when the requirement for reducing the pitch of the electrode terminals becomes strict, it becomes difficult to adopt solder bumps for the protruding electrodes.

[0006] Therefore, a manufacturing method is known in which, instead of solder bumps, columnar micro-metal bumps made of, for example, copper are used as electrodes formed on the electrode terminals. In this method, during the pressure-contacting and heating process when mounting flip chips, the tip of the protruding electrode is plastically deformed to make it adhere closely to the electrode pad, thereby joining the protruding electrode to the electrode pad. With this method, since the micro-bumps are not changed to a liquid state during the pressure-contacting and heating process when mounting flip chips, it is possible to prevent short circuits between terminals that occur with solder bumps.

[0007] For example, Patent Document 1 discloses a configuration in which a protruding electrode has a metal film on the outer circumference of a columnar micro-metal bump to prevent short circuits between terminals. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-294585 [Overview of the project] [Problems that the invention aims to solve]

[0009] When performing flip-chip mounting, regardless of whether solder bumps or fine metal bumps are used, misalignment during mounting can cause the bumps to deviate from the center of the electrode pad and come into contact with the insulating layer outside the electrode pad, such as silicon oxide. In semiconductor devices, as the aforementioned narrowing of the electrode terminal pitch and reduction of the electrode terminal area progresses further, it is expected that the proportion of such bumps coming into contact with the insulating layer will also increase.

[0010] However, because the metal constituting the bumps, such as copper, and the silicon oxide constituting the insulating layer are dissimilar materials, sufficient bonding strength cannot be ensured, resulting in a decrease in bonding strength at the points where the bumps and insulating layer come into contact. Furthermore, if the number of points where the bumps and insulating layer come into contact increases, or if the total area of ​​these points increases, the bonding strength between the semiconductor device with the bumps and the mounting substrate with the electrode pads decreases significantly. Similar problems arise not only with semiconductor devices and mounting substrates, but also when manufacturing mounting structures using a first component with bumps and a second component with electrode pads.

[0011] This disclosure has been made in view of the foregoing, and its purpose is to provide a mounting structure and a method for manufacturing the same that can increase the tolerance for misalignment during mounting and ensure bonding strength. [Means for solving the problem]

[0012] To achieve the above objective, an implementation structure according to one aspect of the present disclosure comprises a first member and a second member. The first member has at least a first electrode pad and a metal bump formed on the surface of the first electrode pad. The second member has at least a second electrode pad arranged opposite to the first member and joined to the metal bump, and a second insulating layer. An oxide film is formed on the surface of the metal bump. At the location where the metal bump and the second electrode pad abut, a metal joint is formed where the metal constituting the metal bump and the metal constituting the second electrode pad are joined. At the location where the oxide film and the second insulating layer abut, an oxide film joint is formed where the oxide film and the second insulating layer are joined.

[0013] A method for manufacturing a mounting structure according to one aspect of the present disclosure comprises at least a first pressurizing step, a first heating step, and a second pressurizing step. In the first pressurizing step, with the first member and the second member facing each other, a load is applied between the first member and the second member to form the metal joint at the location where the metal bump and the second electrode pad come into contact. In the first heating step, after the first pressurizing step has been performed, the first member and the second member are heated to increase the bonding area of ​​the metal joint. In the second pressurizing step, a load higher than that of the first pressurizing step is applied between the first member and the second member to form the oxide film joint at least at the location where the oxide film and the second insulating layer come into contact. [Effects of the Invention]

[0014] According to this disclosure, in a mounting structure comprising a first member provided with bumps and a second member provided with electrode pads, the tolerance for positional misalignment during mounting can be increased. Furthermore, the joint strength between the first member and the second member can be ensured. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view of the first main part of the implementation structure according to Embodiment 1. [Figure 2] This is an enlarged view of a part of the implementation structure shown in Figure 1. [Figure 3] Figure 2 is a schematic plan view of the bonding surface between the metal bump and the electrode pad in the mounting structure shown. [Figure 4] This is a schematic cross-sectional view of the second main part of the implementation structure according to Embodiment 1. [Figure 5] This is a magnified view of a part of the implementation structure shown in Figure 4. [Figure 6] Figure 5 is a schematic plan view of the bonding surface between the metal bump and the electrode pad in the mounting structure shown. [Figure 7A] This is a schematic cross-sectional view illustrating the manufacturing method of the mounting structure according to Embodiment 1. [Figure 7B]It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 7A. [Figure 7C] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 7B. [Figure 7D] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 7C. [Figure 7E] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 7D. [Figure 8] It is a diagram showing an example of the time change of temperature and load applied to the mounting structure in the manufacturing process. [Figure 9A] It is a plan schematic view of the bonding surface between the metal bump and the electrode pad when the first pressing process is being executed. [Figure 9B] It is a plan schematic view of the bonding surface between the metal bump and the electrode pad when the second pressing process is being executed. [Figure 10] It is a schematic cross-sectional view of the second main part of the mounting structure according to Embodiment 2. [Figure 11] ]>It is an enlarged view of a part of the mounting structure shown in FIG. 10. [Figure 12] It is a plan schematic view of the bonding surface between the metal bump and the electrode pad in the mounting structure shown in FIG. 11. [Figure 13A] It is a schematic cross-sectional view for explaining the manufacturing method of the mounting structure according to Embodiment 2. [Figure 13B] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 13A. [Figure 13C] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 13B. [Figure 13D] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 13C. [Figure 13E] It is a schematic cross-sectional view for explaining the subsequent steps of FIG. 13D.

Embodiments for Carrying Out the Invention

[0016] Embodiments of the present disclosure will be described below with reference to the drawings. The following description of preferred embodiments is illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0017] (Embodiment 1) [Implementation Structure] Figure 1 is a schematic cross-sectional view of the first main part of the mounting structure according to Embodiment 1. Figure 2 is an enlarged view of a part of the mounting structure shown in Figure 1. Figure 3 is a schematic plan view of the joint surface between the metal bump and the electrode pad in the mounting structure shown in Figure 2. Figure 4 is a schematic cross-sectional view of the second main part of the mounting structure according to Embodiment 1. Figure 5 is an enlarged view of a part of the mounting structure shown in Figure 4. Figure 6 is a schematic plan view of the joint surface between the metal bump and the electrode pad in the mounting structure shown in Figure 5. In the following description, the view of the mounting structure 9 in the form shown in Figures 1 and 4 will be referred to as a cross-sectional view. The stacking direction of the first member U1 and the second member U2 may be referred to as the vertical direction. In the vertical direction, the side on which the first member U1 is located may be referred to as the top or upper side, and the side on which the second member U2 is located may be referred to as the bottom or lower side.

[0018] As shown in Figures 1, 2, 4, and 5, the mounting structure 9 is made up of a first member U1 and a second member U2 positioned opposite the first member U1. In this embodiment, the first member U1 has a semiconductor device 1, a first electrode pad 2, a first insulating layer 3, and a metal bump 4.

[0019] The semiconductor device 1 is, for example, an LSI (Large Scale Integration). The main constituent materials of the semiconductor device 1 are, for example, silicon, gallium arsenide, gallium nitride, silicon carbide, indium gallium arsenide, gallium nitride, or indium phosphide. The semiconductor device 1 may be a discrete device or a monolithic IC. It may also be a transistor, rectifier, sensor, light-emitting element, or light-receiving element.

[0020] Multiple first electrode pads 2 are provided on the semiconductor device 1. The first electrode pads 2 are made of metal, and their material is, for example, gold, copper, aluminum, aluminum-silicon containing a predetermined amount of silicon, for example, 0.1% or more, an alloy of aluminum and copper, or tungsten.

[0021] The first insulating layer 3 is formed to cover the surface of the semiconductor device 1 on which the first electrode pad 2 is provided. The first insulating layer 3 also covers the periphery of the first electrode pad 2. The first insulating layer 3 is open on the surface of the first electrode pad 2, and most of it is not covered and is exposed. However, it is not limited to this, and the entire surface of the first electrode pad 2 may be exposed and not covered by the first insulating layer 3.

[0022] The metal bump 4 is made of a metal that readily forms oxides, such as copper, aluminum, titanium, or tungsten. As shown in Figures 1, 2, 4, and 5, in cross-sectional view, the metal bump 4 has a tapered shape such that the width of the portion in contact with the second electrode pad 7 is narrower than the width of the portion in contact with the first electrode pad 2. In other words, the metal bump 4 has a bottom portion 41 that contacts the surface of the first electrode pad 2 and a tip portion 42 that protrudes from the bottom portion 41 toward the second electrode pad 7, with the diameter of the bottom portion 41 being larger than the diameter of the tip portion 42. However, the shape of the metal bump 4 is not particularly limited to the shape shown in Figures 1, 2, 4, and 5.

[0023] Although not shown in the diagram, a barrier layer may be formed at the interface between the first electrode pad 2 and the metal bump 4. The barrier layer may consist of one or more layers of a high-melting-point metal such as titanium, titanium nitride, or tungsten, and will prevent the metal constituting the metal bump 4 from excessively alloying with the first electrode pad 2.

[0024] The oxide film 5 is formed on the surface of the metal bump 4, excluding the bonding surface with the first electrode pad 2 and the bonding surface with the second electrode pad 7. The oxide film 5 is a metal oxide formed by oxidizing the metal bump 4. The thickness of the oxide film 5 is approximately 10 nm to 1000 nm, but is not limited to this, and any thickness sufficient to form the oxide film junction 5a described later is acceptable.

[0025] In this embodiment, the second component U2 includes a mounting substrate 6, a second electrode pad 7, and a second insulating layer 8.

[0026] The mounting substrate 6 is a wiring substrate made of an insulating material such as resin or ceramic, with a plurality of second electrode pads 7 formed on one surface. Although not shown, wiring and land electrodes electrically connected to each of the plurality of second electrode pads 7 are formed on the same surface as the second electrode pads 7. Wiring and land electrodes that are not electrically connected to each of the second electrode pads 7 may also be formed on the same surface. Furthermore, the mounting substrate 6 may be a circuit board with electronic components (not shown) mounted on the land electrodes.

[0027] Furthermore, vias may be formed that penetrate the mounting substrate 6 in the thickness direction. In this case, the inside of the via is filled with conductive metal, and one end of the via is connected to the second electrode pad 7 or the aforementioned wiring or land electrodes. An electrode pad (not shown) may be provided on the surface opposite in the thickness direction to the surface on which the second electrode pad 7 is formed. The other end of the via is connected to this electrode pad.

[0028] Multiple second electrode pads 7 are provided on the mounting substrate 6. The second electrode pads 7 are made of metal, and their material is, for example, the same as that of the first electrode pads 2.

[0029] The second insulating layer 8 is formed to cover the surface of the mounting substrate 6 on which the second electrode pad 7 is provided. The second insulating layer 8 also covers the periphery of the second electrode pad 7. The second insulating layer 8 is open on the surface of the second electrode pad 7, and most of the surface of the second electrode pad 7 is not covered by the second insulating layer 8 and is exposed. However, this is not limited to the second insulating layer 8; the entire surface of the second electrode pad 7 may be exposed.

[0030] The second insulating layer 8 is silicon oxide (SiO x (1 <x≦2)やシリコンナイトライド(Si3N 4-x The insulating material comprises at least one of the values ​​(0 ≤ x < 1). The material of the first insulating layer 3 may be the same as or different from that of the second insulating layer 8.

[0031] The metal bump 4 and the second electrode pad 7 are joined at the surface where they contact each other. As shown in Figures 1-3, consider the case where the metal bump 4 is joined to the second electrode pad 7 without protruding from the surface of the second electrode pad 7.

[0032] In this case, as shown in Figure 3, a metal joint 4a and a dissimilar material joint 5b are formed at the joint surface between the metal bump 4 and the second electrode pad 7. The multiple circles drawn within the dissimilar material joint 5b represent voids formed inside the dissimilar material joint 5b. The voids are formed according to the surface roughness of the metal bump 4 and the second electrode pad 7.

[0033] The metal joint 4a is the portion where the metal constituting the metal bump 4 and the metal constituting the second electrode pad 7 are joined together. In this embodiment, both the metal bump 4 and the second electrode pad 7 are made of copper. Therefore, the metal joint 4a is the portion where copper is joined to copper, that is, where metals of the same type are joined together.

[0034] On the other hand, the composition of oxide film 5 is Cu a The material is O(1≦a≦2) or Cu4O3, and the dissimilar material joint 5b is Cu aThis is a portion where O or Cu4O3 and copper are joined by interatomic forces or the like. Note that the joint strength between the metal bump 4 and the second electrode pad 7 via the dissimilar material joint 5b is significantly lower than the joint strength between the metal bump 4 and the second electrode pad 7 via the metal joint 4a.

[0035] On the other hand, as shown in Figures 4-6, there are cases where the metal bump 4 is joined to the second electrode pad 7 while protruding from the surface of the second electrode pad 7. For example, if misalignment occurs during mounting of the first member U1 and the second member U2, the metal bump 4 and the second electrode pad 7 may be joined in the manner shown in Figures 4-6. Furthermore, the amount of misalignment between the metal bump 4 and the second electrode pad 7 tends to be larger when the first electrode pad 2 and the second electrode pad 7 are arranged at a narrow pitch or when there is significant warping of the mounting substrate 6.

[0036] When the aforementioned misalignment occurs, as shown in Figure 6, the joint surface between the metal bump 4 and the second electrode pad 7 forms the aforementioned metal joint 4a and the dissimilar material joint 5b. On the other hand, the contact surface between the metal bump 4 and the second insulating layer 8 is a joint surface between a metallic material and an inorganic material, and the joint strength is extremely weak. In other words, this contact surface can be said to be an unjointed portion 4b.

[0037] On the other hand, an oxide film junction 5a is formed at the contact surface between the oxide film 5 and the second insulating layer 8. At the oxide film junction 5a, the oxide film 5 and the second insulating layer 8 are covalently bonded via oxygen. In other words, the oxide film junction 5a is the portion where the oxide film 5 and the second insulating layer 8 are joined by covalent bonding via oxygen. In addition, the aforementioned voids are formed at the oxide film junction 5a, depending on the surface roughness of the metal bump 4 and the second insulating layer 8.

[0038] [Manufacturing method for the mounting structure] Figure 7A is a schematic cross-sectional diagram illustrating the manufacturing method of the mounting structure according to Embodiment 1. Figure 7B is a schematic cross-sectional diagram illustrating the process following Figure 7A. Figure 7C is a schematic cross-sectional diagram illustrating the process following Figure 7B. Figure 7D is a schematic cross-sectional diagram illustrating the process following Figure 7C. Figure 7E is a schematic cross-sectional diagram illustrating the process following Figure 7D.

[0039] Figure 8 shows an example of the time variation of temperature and load applied to the mounted structure during the manufacturing process. Figure 9A is a schematic plan view of the joint surface between the metal bump and the electrode pad during the first pressurizing process. Figure 9B is a schematic plan view of the joint surface between the metal bump and the electrode pad during the second pressurizing process.

[0040] First, metal bumps 4 are formed on the surface of the first electrode pad 2. The metal bumps 4 are formed on the surface of the first electrode pad 2 by methods such as stud bump bonding, semi-additive or fully additive plating. At this point, the shape of the metal bumps 4, in cross-sectional view, is such that the bottom portion 41a is roughly trapezoidal, narrowing towards the second member U2, and the tip portion 42a is rectangular, extending toward the second member U2 with the same width as the tip of the bottom portion 41a. In this embodiment, the diameter of the bottom portion 41a on the side closer to the first electrode pad 2 is 5.5 μm, and the diameter of the tip portion 42a is 2.5 μm. However, the shape and dimensions of the metal bumps 4 are not particularly limited and can be appropriately changed according to the size of the first electrode pad 2, etc.

[0041] As shown in Figure 7A, the first member U1 is positioned relative to the second member U2 such that the surface on which the first electrode pad 2 is provided faces the surface on which the second electrode pad 7 is provided on the second member U2. At this time, the first member U1 is aligned with the second member U2 such that the first electrode pad 2 and the second electrode pad 7, on which the metal bumps 4 are provided, overlap with a displacement of less than or equal to the allowable tolerance.

[0042] In this embodiment, the number of first electrode pads 2 provided with metal bumps 4 is 2800, but is not limited to this number.

[0043] Next, as shown in Figure 7B, the tip 42a of the metal bump 4 is brought into contact with the second electrode pad 7 from above, and the first member U1 is pressed downward toward the second member U2 (first pressing step).

[0044] As shown in Figure 8, the first pressurization step is performed at room temperature (RT). The load L1 applied to the second member U2 during the first pressurization step is 4N. During the first pressurization step, as shown in Figure 9A, at the point of contact between the metal bump 4 and the second electrode pad 7, the metal bump 4 and the second electrode pad 7 undergo plastic deformation, exposing a new surface and joining the metal bump 4 and the second electrode pad 7. In other words, a metal joint 4a is formed at the joint surface between the metal bump 4 and the second electrode pad 7.

[0045] Next, as shown in Figure 7C, the first member U1 and the second member U2 are heated while the metal bump 4 and the second electrode pad 7 are joined (first heating step). As shown in Figure 8, during the first heating step, the same load (=4N) as in the first pressurizing step is applied to the second member U2. In the first heating step, the temperature is rapidly raised to the target temperature T1 at a heating rate of 20°C / sec or more using a rapid heating method. The target temperature T1 must be set to or below the heat resistance temperature of the semiconductor device 1. For example, if the heat resistance temperature is 200°C, the target temperature T1 is set to 200°C or lower. This allows the deformation of the metal bump 4 due to heating to increase the bonding area between the metal bump 4 and the second electrode pad 7, that is, the bonding area of ​​the metal joint 4a. In addition, the bonding surfaces of the metal bump 4 and the second electrode pad 7 can be brought into close contact in a short time, and oxidation of the bonding surface can be suppressed. The target temperature T1 can be any temperature higher than room temperature.

[0046] After raising the temperature to the target temperature T1, the heating atmosphere is made oxidizing to promote the oxidation of the surface of the metal bump 4. The heating atmosphere may be, for example, a state containing water vapor with a humidity of 60% or more. Alternatively, it may be an atmosphere with a higher oxygen concentration than the atmosphere. After making the heating atmosphere oxidizing, the first member U1 and the second member U2 are heated for a certain period of time to promote the oxidation of the surface of the metal bump 4 and obtain an oxide film 5 of the desired thickness.

[0047] Next, as shown in Figures 7D and 8, the load applied to the second member U2 is increased from L1 to L2 (second pressurization step). In this embodiment, L2 is 32N.

[0048] In the second pressurizing step, a higher load is applied than in the first pressurizing step, further deforming the metal bump 4. At this time, the oxide film 5 formed on the tip of the metal bump 4 in the first heating step undergoes plastic deformation and adheres closely to the second electrode pad 7. At this time, as shown in Figure 9B, the aforementioned dissimilar material joint portion 5b is formed in the portion where the oxide film 5 and the second electrode pad 7 are in contact, and the aforementioned oxide film joint portion 5a is formed in the portion where the oxide film 5 and the second electrode pad 7 are in contact.

[0049] After the second pressurization step, the first member U1 and the second member U2 are heated for a certain period of time in the same state (the second heating step shown in Figures 7E and 8). In this way, a solid-phase reaction proceeds at the joint surface between the metal bump 4 and the second electrode pad 7, causing the metal joint portion 4a to grow and become stronger. In addition, a bond is formed at the contact surface between the oxide film 5 and the second electrode pad 7 through covalent bonding via oxygen.

[0050] In the second heating step, as shown in Figure 8, the same load (=32N) applied in the second pressurizing step is applied to the second member U2. This promotes further solid-phase reaction at the joint surface between the metal bump 4 and the second electrode pad 7. In addition, the bonding strength through oxygen-mediated covalent bonding is enhanced at the contact surface between the oxide film 5 and the second electrode pad 7. However, in the second heating step, a smaller load may be applied to the second member U2 than in the second pressurizing step.

[0051] [Effects, etc.] As described above, the mounting structure 9 according to this embodiment comprises a first member U1 and a second member U2 arranged opposite to the first member U1. The first member U1 includes at least a semiconductor device 1, a first electrode pad 2 formed on the semiconductor device 1, and a metal bump 4 formed on the surface of the first electrode pad 2. The second member U2 includes at least a mounting substrate 6, a second electrode pad 7 formed on the mounting substrate 6 and joined to the metal bump 4, and a second insulating layer 8.

[0052] An oxide film 5 is formed on the surface of the metal bump 4.

[0053] At the point where the metal bump 4 and the second electrode pad 7 come into contact, a metal joint portion 4a is formed where the metal constituting the metal bump 4 and the metal constituting the second electrode pad 7 are joined together.

[0054] At the point where the oxide film 5 and the second insulating layer 8 come into contact, an oxide film junction 5a is formed where the oxide film 5 and the second insulating layer 8 are joined together.

[0055] Furthermore, at the oxide film junction 5a, the oxide film 5 and the second insulating layer 8 are joined by a covalent bond mediated by oxygen.

[0056] According to this embodiment, even if the first member U1 and the second member U2 are mounted with the metal bump 4 protruding from the second electrode pad 7 due to misalignment during mounting, the oxide film 5 and the second insulating layer 8 are joined together to form an oxide film joint 5a. At the oxide film joint 5a, the oxide film 5 and the second insulating layer 8 are joined by covalent bonds, and therefore have a predetermined bonding strength.

[0057] These factors allow for a greater tolerance for misalignment during mounting in the mounting structure 9. Furthermore, the joint strength between the first member U1 and the second member U2 can be ensured. As a result, the connection reliability between the first member U1 and the second member U2, specifically the connection reliability between the metal bump 4 and the second electrode pad 7, can be improved.

[0058] The materials of the first electrode pad 2 and the second electrode pad 7 are preferably selected from one of the following: gold, copper, aluminum, an alloy of aluminum and copper, and tungsten.

[0059] The material of the metal bump 4 is preferably selected from one of copper, aluminum, titanium, and tungsten. The first electrode pad 2, the second electrode pad 7, and the metal bump 4 may each contain small amounts of one or more types of impurities, such as unavoidable impurities introduced during the manufacturing process.

[0060] In particular, if the metal bump 4 is made of a metal that is easily deformed by pressure, such as copper or aluminum, the deformation of the tip portion 42 in the second pressurizing step increases the contact area between the metal bump 4 and the second electrode pad 7, thereby increasing the bonding strength between the first member U1 and the second member U2. Furthermore, the reliability of the connection between the first member U1 and the second member U2 can be improved.

[0061] Furthermore, when the metal bump 4 and the second electrode pad 7 are made of the same type of metal, intermetallic compounds are not formed, thus increasing the bonding strength of the metal joint 4a, and consequently, the joint between the first member U1 and the second member U2. In addition, the reliability of the connection between the first member U1 and the second member U2 can be improved.

[0062] The material of the second insulating layer 8 preferably includes at least one of silicon oxide or silicon nitride. This makes it easy to form an oxygen-mediated covalent bond between it and the oxide film 5.

[0063] The metal bump 4 may have a bottom portion 41 that contacts the surface of the first electrode pad 2 and a tip portion 42 that protrudes from the bottom portion 41. In this case, it is preferable that the diameter of the bottom portion 41 is larger than the diameter of the tip portion 42. By doing so, when mounting the first member U1 onto the second member U2, the pressure applied to the second electrode pad 7 can be increased, and the oxide film 5 and the oxide film formed on the surface of the second electrode pad 7 are easily destroyed at the point where the metal bump 4 and the second electrode pad 7 come into contact. As a result, the metal joint portion 4a is more easily formed by the pressurization and heating during mounting, and the bonding area can be increased. As a result, the bonding strength between the first member U1 and the second member U2 can be increased. In addition, the reliability of the connection between the first member U1 and the second member U2 can be improved.

[0064] The manufacturing method for the mounting structure 9 according to this embodiment comprises at least the following steps.

[0065] In the first pressurization step, with the first member U1 and the second member U2 facing each other, a load L1 is applied between the first member U1 and the second member U2 to form a metal joint 4a at the point where the metal bump 4 and the second electrode pad 7 come into contact.

[0066] In the first heating step, after the first pressurizing step, the first member U1 and the second member U2 are heated to increase the bonding area of ​​the metal joint 4a.

[0067] The second pressurizing step applies a load L2 higher than that of the first pressurizing step between the first member U1 and the second member U2. In addition, the second pressurizing step forms an oxide film joint 5a at the location where the oxide film 5 and the second insulating layer 8 come into contact.

[0068] According to this embodiment, even if the first member U1 and the second member U2 are mounted with the metal bump 4 protruding from the second electrode pad 7 due to misalignment during mounting, a metal joint 4a is formed at the location where the metal bump 4 and the second electrode pad 7 come into contact. In addition, an oxide film joint 5a is formed at the location where the oxide film 5 and the second insulating layer 8 come into contact.

[0069] These factors allow for a greater tolerance for misalignment during mounting in the mounting structure 9. Furthermore, it ensures the joint strength between the first member U1 and the second member U2. Additionally, it improves the reliability of the connection between the first member U1 and the second member U2.

[0070] In the first heating step, it is preferable to further heat the first member U1 and the second member U2 in an oxidizing atmosphere to form an oxide film 5 on the surface of the metal bump 4. In this way, an oxide film 5 of a desired thickness can be formed on the surface of the metal bump 4. As a result, in the second pressurizing step, an oxide film joint 5a can be formed at the location where the oxide film 5 and the second insulating layer 8 come into contact, thereby ensuring the bonding strength between the first member U1 and the second member U2.

[0071] It is preferable to further include a second heating step after the second pressurization step, in which the first member U1 and the second member U2 are heated at a temperature T1 higher than that of the first heating step. In this way, a solid-phase reaction proceeds at the joint surface between the metal bump 4 and the second electrode pad 7, strengthening the metal joint 4a. In addition, the bonding strength by covalent bonding via oxygen is enhanced at the contact surface between the oxide film 5 and the second electrode pad 7, strengthening the oxide film joint 5a. As a result, the bonding strength between the first member U1 and the second member U2 can be increased. Furthermore, the reliability of the connection between the first member U1 and the second member U2 can be improved.

[0072] Furthermore, it is preferable to include a plasma treatment step before the first pressurization step in which the oxide film formed on the surfaces of the metal bump 4 and the second electrode pad 7 is reduced by plasma treatment. By doing so, in the first pressurization step, the newly formed surface can be easily exposed at the point where the metal bump 4 and the second electrode pad 7 come into contact, thereby reliably forming the metal joint 4a.

[0073] Furthermore, in the first heating step, it is preferable to grow an oxide film 5 on the surface of the metal bump 4 using a rapid heating method. By doing so, the bonding surface between the metal bump 4 and the second electrode pad 7 can be brought into close contact in a short time, and oxidation of the bonding surface can be suppressed.

[0074] Furthermore, the first heating step and the second pressurizing step may be performed simultaneously. This shortens the process time and reduces the manufacturing cost of the mounting structure 9. Similarly, the second pressurizing step and the second heating step may be performed simultaneously. This shortens the process time and reduces the manufacturing cost of the mounting structure 9.

[0075] (Embodiment 2) Figure 10 is a schematic cross-sectional view of the second main part of the mounting structure according to Embodiment 2. Figure 11 is an enlarged view of a part of the mounting structure shown in Figure 10. Figure 12 is a schematic plan view of the bonding surface between the metal bump and the electrode pad in the mounting structure shown in Figure 11.

[0076] Figure 13A is a schematic cross-sectional diagram illustrating the manufacturing method of the mounting structure according to Embodiment 2. Figure 13B is a schematic cross-sectional diagram illustrating the process following Figure 13A. Figure 13C is a schematic cross-sectional diagram illustrating the process following Figure 13B. Figure 13D is a schematic cross-sectional diagram illustrating the process following Figure 13C. Figure 13E is a schematic cross-sectional diagram illustrating the process following Figure 13D.

[0077] Figures 10 to 12 shown in this embodiment correspond to Figures 4 to 6 shown in Embodiment 1, and Figures 13A to 13E correspond to Figures 7A to 7E. In addition, the members and parts indicated by reference numeral X in Figures 4 to 7E are indicated by reference numeral 1X in Figures 10 to 13E.

[0078] In the implementation structure 19 of this embodiment shown in Figures 10-13E, the metal bump 14 differs from the metal bump 4 shown in Embodiment 1 in that it has a cylindrical pillar shape, but the other components are the same as in Embodiment 1. Therefore, a detailed explanation of Figures 10-13E is omitted.

[0079] If the metal bump 14 is made of a metal that is not easily deformed by pressure and heat, such as tungsten, having a small diameter tip portion 42a like the metal bump 4 may actually reduce the contact area between the metal bump 14 and the second electrode pad 7. In such cases, as shown in this embodiment, the shape of the metal bump 4 may be made cylindrical to ensure a sufficient contact area between the metal bump 14 and the second electrode pad 17. Note that the shape of the metal bump 14 is not limited to a cylinder; for example, it may be a polygonal prism.

[0080] (Other embodiments) The target temperature T1, heating rate, and load mentioned above are not particularly limited to the examples disclosed in this specification. They are set appropriately according to the size, shape, and material of the metal bump 4 and the second electrode pad 7.

[0081] Furthermore, the shape of the metal bump 4 shown in Embodiment 1 may be applied to the metal bump 14 shown in Embodiment 2. By doing so, in the first pressurizing step, the oxide film 15 and the oxide film formed on the surface of the second electrode pad 17 are easily destroyed, and a new surface is reliably formed at the location where the metal bump 14 and the second electrode pad 17 come into contact. As a result, the metal joint portion 14a can be easily formed.

[0082] Furthermore, the shape of the metal bump 14 shown in Embodiment 2 may be applied to the metal bump 4 shown in Embodiment 1. By doing so, the area of ​​the tip of the metal bump 4 can be increased. This increases the bonding area between the metal bump 4 and the second electrode pad 7, and the bonding area between the oxide film 5 and the second insulating layer 8, thereby increasing the bonding strength between the first member U1 and the second member U2.

[0083] Furthermore, among the components constituting the first component U1, the semiconductor device 1 may be another component, such as a mounting board like a circuit board or a wiring board. [Industrial applicability]

[0084] The mounting structure of this disclosure is useful because it can increase the tolerance for misalignment when mounting the first member and the second member, and can also ensure the joint strength between the first member and the second member. [Explanation of Symbols]

[0085] 1, 11 Semiconductor Devices 2.12 First electrode pad 3.13 First insulating layer 4.14 Metal bump 41, 41a Bottom section 42, 42a Tip 4a, 14a metal joints 4b, 14b Unjoined part 5, 15 Oxide film 5a, 15a Oxide film junction 5b, 15b Dissimilar material joints 6, 16 Mounting board 7.17 Second electrode pad 8.18 Second insulating layer 9, 19 Implementation Structure U1 First component U2 Second component

Claims

1. A first member having at least a first electrode pad and a metal bump formed on the surface of the first electrode pad, The second member comprises a second electrode pad positioned opposite the first member and joining with the metal bump, and a second insulating layer, An oxide film is formed on the surface of the metal bump. At the point where the metal bump and the second electrode pad come into contact, a metal joint is formed where the metal constituting the metal bump and the metal constituting the second electrode pad are joined together. The mounting structure is characterized in that an oxide film junction is formed at the location where the oxide film and the second insulating layer are in contact, and the oxide film and the second insulating layer are joined together.

2. The mounting structure according to claim 1, characterized in that a dissimilar material joint is formed at the location where the oxide film and the second electrode pad come into contact, and the oxide film and the second electrode pad are joined together.

3. The mounting structure according to claim 1, characterized in that the material of the first electrode pad and the second electrode pad is selected from one of the following: gold, copper, aluminum, an alloy of aluminum and copper, and tungsten.

4. The mounting structure according to claim 1, characterized in that the material of the metal bump is selected from one of copper, aluminum, titanium, and tungsten.

5. The mounting structure according to claim 1, characterized in that the material of the second insulating layer includes at least one of silicon oxide or silicon nitride.

6. The mounting structure according to claim 1, characterized in that the oxide film and the second insulating layer are joined by a covalent bond via oxygen at the oxide film junction.

7. The aforementioned metal bump is The bottom portion of the first electrode pad that is in contact with the surface, It has a tip portion that protrudes from the bottom portion, The mounting structure according to claim 1, characterized in that the diameter of the bottom portion is larger than the diameter of the tip portion.

8. A method for manufacturing an assembly structure according to any one of claims 1 to 7, A first pressing step involves applying a load between the first member and the second member while the first member and the second member are facing each other, thereby forming the metal joint at the point where the metal bump and the second electrode pad come into contact; After the first pressurization step is performed, a first heating step is performed in which the first member and the second member are heated to increase the bonding area of ​​the metal joint, A method for manufacturing a mounting structure, comprising at least a second pressing step of applying a load higher than that of the first pressing step between the first member and the second member, thereby forming the oxide film joint at least at the location where the oxide film and the second insulating layer come into contact.

9. The method for manufacturing a mounting structure according to claim 8, further comprising heating the first member and the second member in an oxidizing atmosphere in the first heating step to form the oxide film on the surface of the metal bump.

10. Before performing the first pressurization step, The method for manufacturing a mounting structure according to claim 8, further comprising a plasma treatment step of reducing the oxide film formed on the respective surfaces of the metal bump and the second electrode pad by plasma treatment.

11. The method for manufacturing a mounting structure according to claim 8, characterized in that the first heating step and the second pressurizing step are performed simultaneously.

12. The method for manufacturing a mounting structure according to claim 8, characterized in that the first heating step involves growing the oxide film on the surface of the metal bump by a rapid heating method.

13. After the second pressurization step described above, The method for manufacturing a mounting structure according to claim 8, further comprising a second heating step of heating the first member and the second member at a temperature higher than that of the first heating step.

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