Hollow nano-microbump member, and method for manufacturing a hollow nano-microbump member

Abstract

The present invention provides a component that can achieve sufficient joint strength even at low temperatures and low loads, and a method for manufacturing the component. [Solution] The hollow nano-microbump member 10A has a hollow 12 surrounded by a thin metal film and has hollow nano-microbumps 11A that taper from the base layer 14 towards the tip (upper part).

Description

[Technical Field]

[0001] The present invention relates to a hollow nano-microbump member and a method for manufacturing a hollow nano-microbump member. [Background technology]

[0002] In the manufacturing process of semiconductor devices, joining different components is a crucial step. In the die bonding process, where semiconductor chips are bonded to printed circuit boards, LED (light-emitting diode) chips and power devices are mounted to the board using, for example, flip-chip mounting methods, which utilize bumps (solder bumps) pre-formed on the electrode portions. Similar bonding technologies are also used in the packaging (hermetic sealing, vacuum sealing) of MEMS and sensors. Various shapes of the aforementioned bumps are known, and in recent years, pyramidal and conical bumps have been developed with the aim of concentrating stress at the bonding interface of materials to achieve adhesion, and are used as mounting technology for stacking chips in three dimensions at low temperatures. For example, Patent Document 1 discloses an electrode bump that is disposed on the electrode pad of a semiconductor chip and contacts and connects to the electrode pad of another semiconductor chip or circuit board, characterized in that the tip portion is formed to deform more significantly under stress than the base portion. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2005-243714 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When sharp bumps, such as those described in Patent Document 1, are applied to the mounting of devices that have a quantum well structure inside, such as semiconductor laser chips, there is a problem that stress concentrates at the point of contact of the sharp bumps, easily damaging the active layer and causing the device to degrade. In order to reduce damage to the device, it is necessary to be able to bond with a lower load. Furthermore, in order to obtain sufficient bonding strength with a low load, a structure is needed that can plastically deform with a low load and form a new surface.

[0005] The object of this invention is to provide a member that can achieve sufficient bonding strength even at low temperatures and low loads, and a method for manufacturing the member. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, the inventors have found that a processing method combining template stripping and surface activation bonding can form nano-microbumps (hollow nano-microbumps) having a hollow structure surrounded by a thin metal film, and that by utilizing the easily plastic deformable properties of these hollow nano-microbumps, bonding to the object to be bonded becomes possible at lower temperatures and with lower loads, while more effectively suppressing damage to the object to be bonded. This invention was completed after further consideration based on these findings.

[0007] In other words, the above-mentioned problems of the present invention were solved by the following means. [1] A component with hollow nano-microbumps, having a hollow structure surrounded by a thin metal film, and tapering from the bottom to the tip (top) of the bump. [2] The hollow nano-microbump member according to [1], wherein the metal thin film comprises at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten. [3] The hollow nano-microbump member according to [1] or [2], wherein the bump height of the hollow nano-microbump is 0.05 to 500 μm. [4] The hollow nano-microbumps are cone-shaped, with a base area of ​​1.0 × 10⁻⁶ -4 ~2.5×10 5 μm 2 A hollow nano-microbump member according to any one of [1] to [3] above, wherein the pitch is 0.01 to 5000 μm. [5] A smooth bump member, wherein the hollow nano-microbumps of the hollow nano-microbump member described in any of [1] to [4] above are compressed in the height direction to form a smooth surface. [6] A step of forming a first metal thin film in a mold in which a recess has been formed, A step of forming a second metal thin film on the substrate surface, A step of activating the surfaces of the first metal thin film and the second metal thin film, The process includes the steps of joining the activated first metal thin film and the second metal thin film, removing the mold, and forming hollow nano-microbumps on the substrate surface. A method for manufacturing hollow nano-microbumped components. [7] A method for manufacturing a hollow nano-microbump member according to [6], wherein the first metal thin film and / or the second metal thin film comprises at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten. [8] A method for manufacturing a hollow nano-microbump member according to [6] or [7], wherein the thickness of the first metal thin film is 3 μm or less. [9] A method for manufacturing a hollow nano-microbump member according to any one of [6] to [8], wherein the first metal thin film and the second metal thin film are formed by sputtering.

[10] A method for manufacturing a hollow nano-microbump member according to any one of [6] to [9], wherein the bump height of the hollow nano-microbump is 0.05 to 500 μm. 〔11〕 The hollow nano-micro bump has a cone shape, and the bottom area is 1.0×10 -4 ~2.5×10 5 μm 2 , and the pitch is 0.01~5000 μm. A method for manufacturing a member with a hollow nano-micro bump according to any one of the above [6] to

[10] .

[0008] In the present invention or this specification, a numerical range described using "~" means a range including the numerical values described before and after it as the lower limit value and the upper limit value.

Advantages of the Invention

[0009] The member with a hollow nano-micro bump of the present invention has a hollow structure inside and a tapered shape, so that it can be firmly joined to a joining object even at low temperature and low load. As a result, damage to the joining object during joining can be reduced. Moreover, according to the method for manufacturing a member with a hollow nano-micro bump of the present invention, a member with a hollow nano-micro bump having the above excellent characteristics can be manufactured.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1(a) is a schematic diagram showing three-dimensionally an example of an embodiment of the member with a hollow nano-micro bump of the present invention. FIG. 1(b) is a schematic diagram of the state of observing the member with a hollow nano-micro bump shown in FIG. 1(a) from the front in the Y-axis direction. [Figure 2] FIG. 2 is a schematic diagram showing three-dimensionally an example of another embodiment of the member with a hollow nano-micro bump of the present invention. [Figure 3] FIG. 3 is a drawing substitute photograph showing a schematic diagram of the member with a hollow nano-micro bump of the present invention provided on a semiconductor chip and an enlarged view of its surface. [Figure 4] FIG. 4 is a schematic diagram showing three-dimensionally an example of a member with a smooth bump. [Figure 5]Figure 5 is an explanatory diagram showing the flow of the method for producing the hollow nano-microbumps of the present invention. [Figure 6] Figure 6(a) is a photograph used as a substitute for a drawing, showing the hollow nano-microbump member created in this embodiment. Figure 6(b) is a photograph used as a substitute for a drawing, showing a magnified view of the hollow nano-microbump within the hollow nano-microbump member created in this embodiment. [Figure 7] Figure 7 is a photograph used as a substitute for a drawing, showing the joint surface after die shear strength measurement in Experimental Example 1. [Figure 8] Figure 8 is a graph showing the die-shear intensity for experimental examples 1-6. [Figure 9] Figure 9 is a photograph used as a substitute for a drawing, showing the buckling state of the hollow nano-microbump in a longitudinal section during bonding in Experimental Example 1. [Figure 10] Figure 10 shows the simulation results of stress when pressure is applied from above to members having hollow nano / microbumps and members having non-hollow nano / microbumps, respectively. [Figure 11] Figure 11 is a graph showing the simulation results of the relationship between load (N) and displacement (μm) for both the hollow nano-microbumps and the non-hollow nano-microbumps shown in Figure 10. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will now be described, but the present invention is not limited to the embodiments described below, except as provided for in the present invention.

[0012] [Hollow nano / microbump-equipped components] The hollow nano-microbump member of the present invention (hereinafter also referred to as the "member of the present invention") has a hollow structure surrounded by a thin metal film, and has nano-microscale bumps that taper from the bottom to the tip (upper part). Because the bumps taper from the bottom to the tip, when the member of the present invention comes into contact with an object to be joined, the bumps easily deform plastically, exposing a newly formed metal surface, and a strong bond can be formed with the object to be joined at low temperature and with low load. In other words, compared to conventional sharp bumps without hollows, it is more easily deformable plastically and absorbs stress easily, contributing to a reduction in damage to the substrate on which the member of the present invention is placed and to the object to be joined. That is, the member of the present invention exhibits excellent properties as a so-called joining member. In this invention and specification, the term "bump" is used simply to mean a protrusion. In other words, the term "bump" does not limit the use of the component of the present invention in any way (for example, it is not limited to applications such as connecting electronic components in the manufacturing process of semiconductor devices). Furthermore, the term "nano-microbump" refers to a bump whose size (such as bump height) is on the nano-order or micro-order. The preferred size of the bump will be described later.

[0013] The components of the present invention are preferably used to join different parts or materials together. For example, the components of the present invention can be used in the joining portion when joining semiconductor chips, printed circuit boards, etc., in the semiconductor device manufacturing process. In this case, the hollow nano- and micro-bumps can also function as protruding electrodes. Furthermore, the components of the present invention can also be used, for example, for packaging semiconductor devices (hermetic sealing, vacuum sealing). Furthermore, the applications of the hollow components of the present invention are not limited to those described above. For example, they can also be used as components that generate surface plasmons due to their hollow nano-microbump structure.

[0014] Preferred embodiments of the components of the present invention and the method for manufacturing the hollow nano-microbumped components of the present invention (hereinafter also referred to as the manufacturing method of the present invention) will be described below with reference to the drawings. However, the present invention is not limited to the embodiments described below, except as specified in the present invention.

[0015] Figure 1 is a schematic diagram (explanatory diagram) showing an example of a preferred embodiment of the member of the present invention. The number of hollow nano-microbumps in the member of the present invention may be one or two or more, and can be appropriately set according to the overall size of the member of the present invention and the shape of the hollow nano-microbumps. The member 10A of the present invention shown in Figure 1 has one hollow nano-microbump 11A. The hollow nano-microbump 11A has a square base shape and is a square pyramidal shape that tapers from the bottom to the tip (in the Z-axis direction). In other words, the hollow nano-microbump 11A can also be said to be a pyramidal shape formed on the upper plane 15. The surface shape of the hollow nano-microbump 11A is formed by a cover layer 13 made of a thin metal film and has a hollow 12 inside. The hollow 12 is a space (hollow structure) composed of the cover layer 13 and the base layer 14. In Figure 1, the interface between the cover layer 13 and the base layer 14 is shown by a dashed line; however, in reality, the cover layer 13 and the base layer 14 are joined together. Figure 1(b) is a schematic diagram of the component 10A of the present invention shown in Figure 1(a) when viewed from the front in the direction of the Y-axis. In Figure 1(b), h1 is the vertical height from the upper plane 15 to the top of the hollow nano-microbump 11A (bump height), h2 is the vertical height of the component 10A of the present invention (component thickness), and w is the average thickness of the cover layer 13 made of a thin metal film.

[0016] Figure 2 also shows a part of the component 10B of the present invention, which has one hollow nano-microbump with a different shape from that shown in Figure 1. Note that in Figure 2, only the hollow nano-microbump 11B on the upper plane 15 is shown, and other components are omitted. The bottom shape of the hollow nano-microbump 11B shown in Figure 2 is rectangular, and it has a hip roof shape that tapers towards the tip (Z-axis direction). The hollow nano-microbump 11B has a shape similar to the hollow nano-microbump 11A shown in Figure 1 extended in the X-axis direction, and the hollow nano-microbump 11B has a hollow 12 inside that is surrounded by a cover layer 13 made of a thin metal film. In both members 10A and 10B, the hollow nano-microbumps 11A and 11B have a tapered shape from the bottom to the tip (top) of the bump, and because they have a hollow interior, they are easily plastically deformed during joining, exposing the newly formed metal surface, thereby enabling a strong bond with minimal damage.

[0017] The components of the present invention are preferably formed from the same material. That is, it is preferable that the cover layer and the base layer are made of the same material. The components of the present invention do not include the adhesion layer described later. The size of the component of the present invention is not particularly limited and can be set as appropriate depending on the purpose. For example, when the component of the present invention is used in the manufacturing process of semiconductor devices as a bonding material for semiconductor chips, the size of the component can be matched to the size of the semiconductor chip. Also, when the component of the present invention is used as a sealing material for packaging, the size can be matched to the desired sealing area. For example, the thickness (h2) of the component of the present invention is preferably 0.07 to 500 μm, and more preferably 0.12 to 10 μm.

[0018] The following describes each component of the present invention.

[0019] (Hollow nano-microbumps) The shape (surface shape) of the hollow nano-microbump is not particularly limited as long as it tapers from the bottom to the tip (top) of the bump, and can be set as appropriate depending on the purpose. For example, it may be a conical shape such as a square pyramidal shape or a cone shape as shown in Figure 1, or it may be a bell shape. It may also be a hip roof shape as shown in Figure 2. Furthermore, it may be a shape made by combining multiple of these, for example, a square ring shape made by combining four hip roof shapes as shown in Figure 2. Furthermore, the aforementioned "tapered shape" may be a shape in which the area on the XY plane decreases continuously from the bottom to the tip of the bump, or it may be a shape in which it decreases in stages. In addition, even if there is a part (a constriction) in which the area on the XY plane decreases, like a gourd, if the area of ​​the tip is smaller overall than the area of ​​the bottom, it will be included in the aforementioned "tapered shape".

[0020] The hollow nano-microbumps are formed from a thin metal film. The thin metal film preferably contains at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten, and more preferably is a thin film of a metal or alloy selected from gold, silver, copper, aluminum, platinum, tin, indium, and tungsten. The thickness of the cover layer made of the metal thin film is not particularly limited and can be set appropriately so as to form a hollow inside the nano-microbumps. The average thickness (w) of the cover layer can be 10 μm or less, and preferably 3 μm or less. The average thickness (w) may also be 0.01 μm or more, or 0.05 μm or more. A preferred range for such an average thickness (w) is 0.01 to 10 μm, and preferably 0.05 to 3 μm. In particular, by forming the nano-microbumps with a metal thin film with a thickness of 1 μm or less (setting the average thickness (w) to 1 μm or less), the size of the metal crystal grains forming the metal thin film can be controlled to be smaller, which contributes to increasing the bonding strength due to atomic diffusion and enables bonding without pressure (for example, bonding pressure being only the amount of pressure due to the weight of the substrate on which the component of the present invention is placed or the object to be bonded).

[0021] The bottom surface shape of the hollow nano / micro bump (the shape of the boundary with the upper plane 15) is not particularly limited. For example, it may be a regular polygon shape as shown in FIG. 1 (the bottom surface shape of the hollow nano / micro bump 11A in FIG. 1 is a square), or it may be a circle. Also, as shown in FIG. 2, the bottom surface shape may be a polygon shape other than a regular polygon shape (the bottom surface shape of the hollow nano / micro bump 11B in FIG. 2 is a rectangle), or it may be an elliptical shape. Also, the height (h1) of the hollow nano / micro bump is not particularly limited and can be appropriately set according to the purpose. For example, the bump height can be 0.05 to 500 μm, and more preferably 0.1 to 10 μm.

[0022] The number of the hollow nano / micro bumps provided on the member of the present invention is not particularly limited and can be appropriately set according to the shape and size of the hollow nano / micro bump and the size of the member of the present invention. By providing a plurality of hollow nano / micro bumps on the member of the present invention, more stable bonding can be achieved. For example, in FIG. 3, in the member 10 of the present invention provided on the bonding portion 21 of the semiconductor chip 20, an electron micrograph showing the upper plane 15 and a plurality of hollow nano / micro bumps 11 is shown. The shape of the hollow nano / micro bump 11 shown in FIG. 3 is a pyramid shape. When the member of the present invention is used in the manufacturing process of semiconductor devices or the like, the bottom area per hollow nano / micro bump (the area of the shape of the boundary with the upper plane 15) is 1.0×10 -4 ~2.5×10 5 μm 2 is preferable. Also, the pitch width a of such a plurality of hollow nano / micro bumps is preferably 0.01 to 5000 μm.

[0023] (Hollow) As described above, the hollow space is a space surrounded by a thin metal film. In the component of the present invention, because the nano-microbump has a hollow space inside, the bump easily buckles and plastically deforms at a lower bonding pressure during joining, creating a new metal surface. Therefore, compared to conventional bumps, a stronger bond can be achieved at a lower temperature and with a lower load.

[0024] As described above, the hollow space is a space surrounded by a cover layer made of a thin metal film and a base layer. Preferably, the hollow space is located in the center of the nano-microbump when viewed from above. The size of the hollow section is not particularly limited and can be determined by the shape of the bump and the thickness of the cover layer.

[0025] <Joining conditions> When the member of the present invention is used for joining purposes, the joining temperature is preferably 300°C or less, more preferably 25 to 200°C, and even more preferably 25 to 150°C. The joining pressure is preferably 200 MPa or less, more preferably 100 MPa or less, and even more preferably 50 MPa or less. In addition, in the present invention, sufficient joining strength is obtained by exposing a newly formed surface due to the plastic deformation of the bump, so joining can be performed without surface activation treatment such as plasma treatment. In this invention and specification, the bonding pressure is the load divided by the upper surface area of ​​the bonding portion of the substrate on which the component of the present invention is placed. For example, in the case of the semiconductor chip 20 shown in Figure 3, the upper surface area is the area of ​​the bonding portion 21 (terrace portion) (1.5 mm × 1.5 mm).

[0026] [Smooth bumped component] The member of the present invention may have a smooth surface pre-formed on the upper part of the hollow nano-microbumps before joining, for example. That is, another preferred embodiment of the present invention is a member with smooth bumps, in which the hollow nano-microbumps of the member with hollow nano-microbumps are compressed in the height direction (Z-axis direction) to form a smooth surface on the upper part of the bumps. The method for forming the smooth surface on the upper part of the hollow nano-microbumps is not particularly limited and can be formed, for example, by coining using a Si substrate. By performing coining using an extremely smooth surface such as a Si substrate, the resulting smooth surface can be made highly smooth. Furthermore, it is practically difficult to directly and appropriately specify the technical features of the smooth bumped member of the present invention based on its structure, composition, and properties. Therefore, in order to clarify the invention by clearly indicating the differences from conventional products, the manufacturing method (process) of the smooth bumped member of the present invention is specified.

[0027] Figure 4 shows a schematic example of a smooth bump member of the present invention after coining treatment. By applying pressure to the member 10A of the present invention from above with a Si substrate 16, the side surface (cover layer 13) made of a thin metal film of the hollow nano / microbump 11A buckles and folds into the hollow 12 inside, forming a smooth surface 17 on the top. Since the hollow nano / microbump 11A is made of a thin metal film, the crystal grains of the metal constituting the thin metal film are controlled to be within a sufficiently small range. Therefore, the resulting smooth surface 17 is highly smooth, and when joining with an object to be joined using the smooth bump member, joining is possible without pressure (for example, the joining pressure is only the amount of pressure exerted by the weight of the substrate on which the member of the present invention is placed and the object to be joined).

[0028] The coining process is not particularly limited as long as it can form a desired smooth surface on the top of the hollow nano-microbumps, and the conditions can be set appropriately according to the purpose.

[0029] [Manufacturing method for hollow nano / microbump-attached components] The manufacturing method of the present invention includes the steps of: forming a first metal thin film in a mold having a recess formed therein; forming a second metal thin film on the surface of a substrate; activating the surfaces of the first metal thin film and the second metal thin film; joining the activated first metal thin film and the second metal thin film, removing the mold, and forming hollow nano-microbumps on the surface of the substrate. In other words, a processing method combining surface activation treatment and template stripping can be used to realize a component having nano-microbumps with hollow interiors. The manufacturing method of the present invention can be used to obtain the component of the present invention described above. The substrate surface is the surface on which the component of the present invention is provided, and is usually at least one surface of the substrate. Figure 5 is an explanatory diagram that schematically shows one example of a preferred embodiment of the manufacturing method of the present invention. Hereinafter, the preferred form of each step of the manufacturing method of the present invention will be described with reference to the drawings.

[0030] <Mold preparation process> In the manufacturing method of the present invention, a mold with recesses is used. The shape of these recesses becomes the surface shape of the hollow nano-microbumps. The type of mold and the method of forming the recesses are not particularly limited and are set up so as to form the hollow nano-microbumps for the above purpose. The preparation step of the mold with recesses can be, for example, the following steps. The above-mentioned recesses can be formed by crystal anisotropic etching using Si material as a template material. Figure 5(a) shows how an inverted pyramidal recesses are formed on the Si material (Si template) 31 by performing crystal anisotropic etching using a TMAH (tetramethylammonium hydroxide) solution, using a patterned oxide film (SiO2 film) 32A formed on the surface of the Si material 31 as a mask. The method for patterning the oxide film (SiO2 film) 32A is not particularly limited; for example, a mask with a desired pattern can be formed on the surface of the oxide film (SiO2 film) using photoresist, and the unmasked parts of the oxide film (SiO2 film) can be etched using photolithography and CF4 gas plasma. After crystal anisotropic etching, the oxide film (SiO2 film) 32A used as a mask is removed with an HF (hydrofluoric acid) solution, and a new oxide film (SiO2 film) 32B is formed by heat treatment. Figure 5(b) shows the formation of the new oxide film (SiO2 film) 32B on the surface of the Si material, including the recess formed as described above. By forming an oxide film on the surface, the peelability between the Si material and the first metal thin film can be improved. The mold 30 formed in this manner can be used in the manufacturing method of the present invention.

[0031] <Step of forming a first metal thin film in a mold with a recess formed therein> A first metal thin film 33 is formed on the surface of the mold 30 obtained as described above. Figure 5(c) shows the first metal thin film 33 being formed on the oxide film (SiO2 film) 32B. The method for forming the metal thin film is not particularly limited and can be sputtering, vapor deposition, ion plating, or plating. The above-mentioned first metal thin film serves as a cover layer in the hollow nano-microbump of the component of the present invention. That is, the thickness of the first metal thin film can be 0.01 to 10 μm, and more preferably 0.05 to 3 μm. Furthermore, the first metal thin film preferably contains at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten, and more preferably is a thin film of a metal or alloy thereof selected from gold, silver, copper, aluminum, platinum, tin, indium, and tungsten.

[0032] <Process for forming a second metal thin film on the substrate surface> A second metal thin film is formed on the surface of the substrate. The substrate is the substrate on which the component of the present invention is arranged. That is, the substrate and the substrate surface may be, for example, a semiconductor chip and the substrate surface may be the connection surface (joining surface with other components) of the semiconductor chip, or a circuit board and the substrate surface may be the connection surface (joining surface with other components) of the circuit board. Alternatively, the substrate may be a desired component and the substrate surface may be a connection surface (joining surface with other components) for sealing. Figure 5(c) shows that a Ti layer 35, which is an adhesion layer, is formed on the surface of the substrate 34, and a second metal thin film 36 is formed on the surface of the Ti layer 35. The method for forming the second metal thin film 36 is not particularly limited, and for example, the same method as the method for forming the first metal thin film 33 can be used. Furthermore, the formation of the second metal thin film 36 is not limited to the Ti layer 35, and it may be formed without using the Ti layer 35, or it may be formed on the surface of another adhesion layer instead of the Ti layer 35. The above-mentioned second metal thin film serves as the base layer in the hollow nano-microbump of the component of the present invention. Specifically, the thickness of the second metal thin film is preferably 0.01 to 10 μm, and more preferably 0.05 to 3 μm. Furthermore, the second metal thin film preferably contains at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten, and more preferably is a thin film of a metal or alloy selected from gold, silver, copper, aluminum, platinum, tin, indium, and tungsten. Typically, the material of the second metal thin film and the material of the first metal thin film are the same.

[0033] The first and second metal thin films are subjected to an activation treatment on their surfaces. A general method can be used for the surface activation treatment, such as using an atomic beam, ion beam, low vacuum plasma, or atmospheric pressure plasma. In particular, treatment with an atomic beam or ion beam can remove contaminants and inert layers such as oxide films from the surface of the metal thin films, allowing the two metal thin films to be joined in a subsequent step. Figure 5(d) shows the activation treatment being applied to the surfaces of the first and second metal thin films.

[0034] <A process of joining an activated first metal thin film and a second metal thin film, removing the mold, and forming hollow nano- and micro-bumps on the substrate surface.> The second metal thin film, after the surface activation treatment, is joined to the second metal thin film by overlapping it with a mold on which the first metal thin film is formed, so that the two metal thin films are in contact with each other. Since the mold is removed after joining, it is preferable to determine the joining conditions so that the adhesion force between the joined first metal thin film and the second metal thin film is greater than the adhesion force between the oxide film (SiO2 film) of the mold and the first metal thin film. For example, the joining temperature can be room temperature and the joining pressure can be 5 to 100 MPa. After joining, the mold can be removed to obtain a member with a hollow structure and nano-microbumps formed on it. Figure 5(e) shows how the mold 30 on which the first metal thin film 33 is formed and the substrate 34 on which the second metal thin film 36 is formed are joined so that the first metal thin film 33 and the second metal thin film 36 are in contact with each other. Figure 5(f) shows how, after joining, the mold 30 is removed, and a member 10 having a hollow interior 12 is formed on the surface of the substrate. [Examples]

[0035] The present invention will be described in more detail based on examples. Except as otherwise provided herein, the present invention is not limited to the following examples.

[0036] <Manufacturing of hollow bump substrates> As shown in Figure 5, a hollow bumped Si substrate was fabricated by combining template stripping and surface activation bonding. The specific steps were as follows (a) to (f). All of the following processes were performed at room temperature.

[0037] (a) A thermal oxide film (SiO2 film) was formed on a Si template, a mask of the desired pattern was formed with photoresist, and the unmasked areas of the thermal oxide film (SiO2 film) were etched using photolithography and CF4 gas plasma. Then, the photoresist was removed, and anisotropic etching using a TMAH solution was performed using the remaining thermal oxide film (SiO2 film) as a mask to fabricate an inverted pyramidal cavity on the Si template. (b) The thermal oxide film (SiO2 film) was removed using HF solution, and a thermal oxide film (SiO2 film) was formed again on the etched Si template. (c) A thin Au film was sputtered onto the thermal oxide film (SiO2 film) formed in step (b) to a thickness of 1 μm. In addition, a thin Ti film (thickness: 10 nm) was formed on a Si substrate different from the Si template above to form an adhesion layer, and a thin Au film was sputtered onto this adhesion layer to a thickness of 0.1 μm. (d) The surfaces of the Au thin film on the Si template and the Au thin film on the Si substrate were surface-activated using an Ar fast atomic beam. The irradiation conditions for the Ar fast atomic beam were a current of 60 mA, a voltage of 0.6 kV, an Ar flow rate of 12 sccm, and an irradiation time of 5 minutes. (e) The Si template and Si substrate after surface activation were bonded together so that the Au thin film faced each other, and the bond was maintained at a bonding pressure of 44 MPa at room temperature for 5 minutes. (f) By mechanically peeling the Si template from the Si substrate, the Au thin film on the Si template is transferred to the Si substrate, and hollow bumps are formed on the Si substrate, resulting in a Si substrate with hollow bumps.

[0038] Figures 6(a) and (b) show an overall photograph of the Si substrate with hollow bumps fabricated as described above, and magnified photographs of the hollow bumps. The magnified photographs of the hollow bumps were taken using a scanning electron microscope. The dimensions of the Si substrate used were 2 mm in length and 2 mm in width. The hollow bumps fabricated as described above were pyramidal, with a square base measuring 6 μm x 6 μm. The bump height was approximately 5 μm, and the bump pitch was 12 μm.

[0039] [Joint strength evaluation] To clarify the bonding characteristics of the hollow bumps obtained as described above, a Si substrate with hollow bumps formed on it was solid-state bonded to a Si substrate with an Au thin film deposited by sputtering (hereinafter referred to as the "counter substrate"), and the bonding strength (die shear strength) was then evaluated. For comparison, a Si substrate with an Au thin film without hollow bumps (rms surface roughness: 1.4 nm) was used instead of the Si substrate with hollow bumps. A Cr layer (thickness: 5 nm) was used as an adhesion layer for the Au thin film of the counter substrate to be bonded. The bonding conditions are shown in Table 1 below. In each of the experimental examples 1 to 6, bonding was performed by thermocompression bonding at a bonding temperature of 150°C, a bonding pressure of 31 to 102 MPa, and for 10 minutes in air. Bonding strength was evaluated by die shear test. Die shear strength is calculated by the load at fracture over the bonding area (1.5 × 1.5 mm²). 2 The value was calculated by dividing by ( ) and the average of three tests was used. The RMS surface roughness of each sample was measured using a white light interferometer (product name: Nexview, model number: NX2, manufactured by Zygo). Die shear tests were performed using a die shear tester (product name: Bonding Tester, model number: PTR-1100, manufactured by Resca). The results are shown in Table 1, Figure 7, and Figure 8 below.

[0040] [Table 1]

[0041] Figure 7 is a photograph used as a diagram to show the surface of the mating substrate after the die-shear test in Experimental Example 1. The die-shear test caused the Si substrate to shatter into tiny pieces, demonstrating that the bonding strength reached the fracture strength of the Si bulk.

[0042] The graph shown in Figure 8(a) compares the die shear strength with and without hollow bumps in Experimental Examples 1 and 2. As shown in Experimental Example 1, using a Si substrate with hollow bumps achieved sufficient die shear strength exceeding the standard value (×2.0, 12 MPa) according to the MIL-STD-883 standard. In contrast, as shown in Experimental Example 2, the bonding strength was significantly weaker when using a Si substrate without hollow bumps, and it was shown that bonding was insufficient under the same low-pressure, low-temperature bonding conditions as in Experimental Example 1 (bonding pressure 102 MPa, bonding temperature 150°C). Figure 8(b) is a graph comparing the die shear strength at different bonding pressures in Experimental Examples 1, 3, and 4. Sufficient die shear strength was obtained in all experimental examples within the bonding pressure range of 31–102 MPa. Figure 8(c) is a graph comparing the die shear strength in experimental examples 4, 5, and 6, based on differences in the surface roughness of the Au thin film on the mating substrate. In all experimental examples, it was shown that sufficient die shear strength could be achieved over a wide range of surface roughness of the Au thin film, from 0.6 to 24 nm. In particular, it was shown that the smoother the surface roughness of the Au thin film, the higher the die shear strength.

[0043] Figure 9 is a photograph used as a substitute for a drawing, showing the bonded cross-section of the sample bonded in Experimental Example 6 after cutting and processing with ion milling to expose the bonded surface, and then observing it with a scanning electron microscope. After bonding, the hollow bumps undergo significant plastic deformation and are shown to be in close contact with the Au thin film of the mating substrate. It is presumed that this large plastic deformation of the hollow bumps exposes active new surfaces, enabling a strong bond. Furthermore, fine crystal grains were observed in the hollow bump region. The grain boundary diffusion coefficient of Au was nearly 20 orders of magnitude larger (8 × 10⁻¹⁰) than the self-diffusion coefficient. -19 m 2 ( / s) has also been reported (G. Casillas et al., Nanoscale, 5, p. 6333, (2013)). It was thought that by limiting the film thickness and suppressing the crystal grain size, surface diffusion and grain boundary diffusion could be effectively utilized.

[0044] To compare the elastoplastic deformation and stress distribution when bumps are compressed with and without hollow structures, finite element analysis was performed using COMSOL Multiphysics. Figure 10(a) shows the simulation results of elastoplastic deformation and stress when the same load is applied, for the case using hollow bumps, and Figure 10(b) shows the simulation results for the case using bumps with the same external shape as the hollow bumps but without hollow structures. Figure 11 is a graph showing the simulation results of the relationship between load (N) and displacement (μm) for both the hollow bumps and the non-hollow bumps. As shown in Figures 10 and 11, hollow bumps deform more easily than conventional non-hollow bumps and can adhere closely to the surface to be joined. Furthermore, the contact area is larger, and the internal stress on the object being joined to the bump is smaller.

[0045] The present invention demonstrates that by using the component, a strong bond can be achieved with the object to be joined at low temperatures and low loads. Furthermore, the characteristic structure of the component absorbs stress during joining, enabling joining with less damage. [Explanation of Symbols]

[0046] 10, 10A, 10B components 11, 11A, 11B Hollow Nano-Microbumps 12 Hollow 13. Cover layer 14 Basal layer 15 Upper plane 16 Si substrate 17 Smooth surface 20 semiconductor chips 21. Joint (Terrace section) 30 molds 31 Si material 32A, 32B Oxide film (SiO2 film) 33 First metal thin film 34 Base material 35 Ti layer 36 Second metal thin film h1 Bump height h2 Member thickness w Cover layer thickness a pitch width

Claims

1. A hollow nano-microbump component having a hollow structure surrounded by a thin metal film, with hollow nano-microbumps that taper from the bottom to the tip.

2. The hollow nano-microbump member according to claim 1, wherein the metal thin film comprises at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten.

3. The hollow nano-microbump member according to claim 2, wherein the bump height of the hollow nano-microbump is 0.05 to 500 μm.

4. The hollow nano-microbumps are cone-shaped, with a base area of ​​1.0 × 10⁻⁶ －４ ~2.5 x 10 ５ μm ２ The hollow nano-microbump member according to claim 3, wherein the pitch is 0.01 to 5000 μm.

5. A smooth bump member, wherein a smooth surface is formed on the upper part of the hollow nano-microbumps of the hollow nano-microbump member according to any one of claims 1 to 4.

6. A step of forming a first metal thin film in a mold in which a recess has been formed, A step of forming a second metal thin film on the substrate surface, A step of activating the surfaces of the first metal thin film and the second metal thin film, The process includes the steps of joining the activated first metal thin film and the second metal thin film, removing the mold, and forming hollow nano-microbumps on the substrate surface, A method for manufacturing hollow nano- and micro-bumped components.

7. The method for manufacturing a hollow nano-microbump member according to claim 6, wherein the first metal thin film and / or the second metal thin film comprises at least one of gold, silver, copper, aluminum, platinum, tin, indium, and tungsten.

8. The method for manufacturing a hollow nano-microbump member according to claim 7, wherein the thickness of the first metal thin film is 3 μm or less.

9. The method for manufacturing a hollow nano-microbump member according to claim 8, wherein the first metal thin film and the second metal thin film are formed by sputtering.

10. A method for manufacturing a hollow nano-microbump member according to claim 9, wherein the bump height of the hollow nano-microbump is 0.05 to 500 μm.

11. The hollow nano-microbumps are cone-shaped, with a base area of ​​1.0 × 10⁻⁶ －４ ~2.5 x 10 ５ μm ２ A method for manufacturing a hollow nano-microbump member according to claim 10, wherein the pitch is 0.01 to 5000 μm.

Images