Hybrid bonding substrate, hybrid bonding structure, and manufacturing method thereof

Abstract

To provide a hybrid bonding substrate in which conductive portions formed by plating can be sufficiently bonded to each other, a manufacturing method thereof, a bonding method, a hybrid bonding structure in which a bonding state between the conductive portions is good, and a manufacturing method thereof.SOLUTION: A manufacturing method of a hybrid bonding substrate comprising a substrate, a seed layer, and a copper plating layer, comprises: a seed layer forming step of forming a seed layer including a nickel layer, a cobalt layer, a ruthenium layer, or a molybdenum layer, on a surface of the substrate; and a plating step of forming a copper plating layer on an upper layer of the seed layer. A hybrid bonding substrate comprises: the substrate; the seed layer; and the copper plating layer, in which the seed layer is provided between the substrate and the copper plating layer, and which contains the nickel layer, the cobalt layer, the ruthenium layer, or the molybdenum layer. The present invention provides a hybrid bonding structure in which the hybrid bonding substrates are bonded to each other via the copper plating layer, and a manufacturing method thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hybrid bonding substrate, a hybrid bonding structure, and a method for manufacturing the same. [Background technology]

[0002] Hybrid bonding technology, which bonds multiple substrates having conductive portions such as metal electrodes and insulating portions on their surfaces, has been known as a technique for achieving miniaturization, high functionality, and high integration in semiconductor devices. Hybrid bonding is a technique in which, for example, two substrates are bonded together, and then, as necessary, heat treatment or pressure treatment is performed to bond the conductive portions and / or insulating portions together. This hybrid bonding directly bonds multiple substrates without using solder such as microbumps, making it possible to achieve a narrower pitch in the bonded substrates (bonded structure). Furthermore, because the conductive portions and insulating portions on multiple substrates can be simultaneously bonded together, this can contribute to improving productivity, reducing weight, and reducing costs in addition to increasing the functionality of semiconductor devices.

[0003] One method for forming conductive parts such as electrodes on a substrate used for hybrid bonding (hereinafter also referred to as "substrate for hybrid bonding") is to plate the substrate or the base material that constitutes it with a metal such as copper or gold.

[0004] For example, Patent Document 1 discloses a method of forming a gold thin film on a substrate and then electroplating a gold alloy from above a pattern mask. Patent Document 2 discloses a semiconductor device having a copper plating layer on a conductor provided inside an insulating layer, and Patent Document 3 discloses a method of electroplating copper on a barrier layer. Plating methods also enable efficient production of conductive parts of desired thickness in targeted locations, resulting in advantages such as narrower pitch, higher density, lighter weight, and improved productivity for substrates. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-130981 [Patent Document 2] Japanese Patent Application Publication No. 2019-165110 [Patent Document 3] Special Publication No. 2022-528073 Summary of the Invention [Problem to be solved by the invention]

[0006] While hybrid bonding of substrates having conductive portions of plating layers has the advantages of enabling the aforementioned narrow pitch and high density, it also has the drawback of easily insufficient bonding between conductive portions such as electrodes. Increasing the temperature or pressure during bonding to improve the bonding condition may lead to deterioration of the substrate, increased manufacturing costs, reduced productivity, etc.

[0007] As a method for reducing the heating temperature during bonding, Patent Document 1 discloses a bonding method in which a gold plating layer on one substrate is made nanoporous and is then abutted against a thin gold film on another substrate, applying a pressure of 10 to 50 MPa. While this method can reduce the heating temperature, the microporous structure of the bonded portion can result in insufficient bonding. Furthermore, the semiconductor device described in Patent Document 2 aims to reduce the temperature of the bonding process (annealing treatment) by forming an aluminum layer or other material below the copper plating layer, but the quality of the bonding between the plating layers is not examined. Furthermore, Patent Document 3 describes a hybrid wafer bonding method in which a seed layer of copper doped with metal impurities is provided below the copper plating layer, and the substrate structure is given a distinctive feature, but the bonding state of the resulting bonded structure is not disclosed. Thus, there are many aspects of the bonding state of the plating layers in hybrid bonding that have not been examined.

[0008] The present inventors have found that when a conductive part such as an electrode is produced by plating a metal such as copper, an electrode with a good bonded state cannot be obtained unless an intermediate layer between the plating layer and the substrate, a so-called seed layer, is appropriate. As shown in the comparative example (conventional example) described later, in a hybrid bonded structure obtained by overlapping ordinary copper plating layers and applying pressure, heat treatment, etc., the interface (bonding interface) of the copper phase that is generated when the plating layers are bonded together often remains.

[0009] In order to solve the above-mentioned problems, the present invention aims to provide a hybrid bonding substrate in which conductive parts formed by plating can be sufficiently bonded to each other, a manufacturing method and bonding method thereof, and a hybrid bonding structure in which the conductive parts are well bonded to each other and a manufacturing method thereof. [Means for solving the problem]

[0010] The present inventors have conducted research to solve the above problems, and as a result, have found that providing a seed layer containing a nickel layer as an intermediate layer between the base material and plating layers that constitute the substrate allows for good bonding between the plating layers in hybrid bonding, and have completed the present invention.

[0011] That is, the present invention provides the following (1) to (16). (1) A method for producing a hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, comprising: a seed layer forming step of forming the seed layer including a nickel layer on the surface of the base material; a plating step of forming the copper plating layer on the seed layer; A method for manufacturing a substrate for hybrid bonding, comprising: (2) A method for producing a hybrid bonding substrate having a base material, a seed layer, and a copper plating layer, comprising: a seed layer forming step of forming the seed layer on the surface of the substrate, the seed layer including one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer; a plating step of forming the copper plating layer on the seed layer; A method for manufacturing a substrate for hybrid bonding, comprising: (3) The seed layer forming step forming a titanium layer in contact with the surface of the substrate; forming the nickel layer as an upper layer of the titanium layer; and forming a copper layer as an upper layer of the nickel layer. The method for producing a substrate for hybrid bonding according to (1) above. (4) The method for producing a substrate for hybrid bonding according to (1) or (3) above, wherein in the seed layer forming step, the nickel layer is formed by sputtering. (5) A hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, the seed layer is provided between the substrate and the copper plating layer and includes a nickel layer; Substrate for hybrid bonding. (6) A hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, the seed layer is provided between the substrate and the copper plating layer, and includes one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer; Substrate for hybrid bonding. (7) The hybrid bonding substrate according to (5) above, wherein the seed layer is formed by laminating a titanium layer in contact with the surface of the base material, the nickel layer, and a copper layer in this order. (8) A method for manufacturing a hybrid bonded structure formed by hybrid bonding substrates each having a base material, a seed layer, and a copper plating layer, comprising: As the substrate, any one of the hybrid bonding substrates (5) to (7) above is used, a bonding step of overlapping and bonding the two substrates via the copper plating layer, A method for manufacturing a hybrid joint structure. (9) A method for manufacturing a hybrid bonded structure formed by hybrid bonding substrates each having a base material, a seed layer, and a copper plating layer, comprising: a substrate manufacturing process in which the substrate is manufactured by carrying out any one of the methods (1) to (4) above; a bonding step of overlapping and bonding the two manufactured substrates with the copper plating layer interposed therebetween; A method for manufacturing a hybrid joint structure, comprising: (10) The method for producing a hybrid bonded structure according to (8) or (9), wherein the bonding step is performed by applying a pressure of 0.1 to 30 MPa. (11) A hybrid bonding structure in which substrates each having a base material, a seed layer, and a copper plating layer are bonded together via the copper plating layer, In each of the substrates, the seed layer is provided between the substrate and the copper plating layer and includes a nickel layer; Hybrid joint structure. (12) A hybrid bonding structure in which substrates each having a base material, a seed layer, and a copper plating layer are bonded together via the copper plating layer, In each of the substrates, the seed layer is provided between the substrate and the copper plating layer and includes one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer; Hybrid joint structure. (13) In each of the substrates, the seed layer is formed by laminating a titanium layer in contact with the surface of the base material, the nickel layer, and a copper layer in this order; Hybrid joint structure (11) above. (14) A hybrid joint structure according to any one of (11) to (13) above, wherein the substrate comprises a substrate-1 having a copper plating layer thickness t1 and a substrate-2 having a copper plating layer thickness t2; In the copper plating layer, a parallel plane P1 of the substrate-1, which is imaginary at a position t1 away from the end face of the copper plating layer on the substrate-1 side; and a parallel plane P2 of the substrate-2, which is imaginary at a position t2 away from the end face of the copper plating layer on the substrate-2 side; A hybrid bonded structure with a copper crystalline phase that penetrates both the metal and the alloy. (15) A method for bonding substrates each having a base material, a seed layer, and a copper plating layer, comprising: As the substrate, any one of the hybrid bonding substrates (5) to (7) above is used, a step of overlapping and hybrid-bonding the two substrates via the copper plating layer, Method of joining boards. (16) The method for bonding substrates according to (15) above, wherein in the step, hybrid bonding is performed by applying a pressure of 0.1 to 30 MPa. [Effects of the Invention]

[0012] By using the hybrid bonding substrate of the present invention for bonding, a bonded structure in which the copper plating layers are sufficiently bonded to each other (e.g., a hybrid-bonded substrate) can be obtained. Furthermore, the manufacturing method or bonding method of the present invention makes it possible to easily obtain the above-mentioned hybrid bonding substrate or hybrid bonded structure. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing one embodiment of a hybrid bonding substrate of the present invention. [Figure 2] 1 is an explanatory diagram showing one embodiment of a method for manufacturing a hybrid joint structure of the present invention. [Figure 3] 1 is a cross-sectional view showing an embodiment of a hybrid joint structure of the present invention. [Figure 4] FIG. 2 is a photograph of a SIM image of a hybrid joint structure in Example 1 according to the present invention. [Figure 5] FIG. 1 is a photograph of a SIM image of a hybrid joint structure in Comparative Example 1. [Figure 6] FIG. 2 is an explanatory diagram showing the state of a copper plating layer in a hybrid joint structure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below based on embodiments, but the present invention is not limited to these embodiments.

[0015] <Hybrid bonding substrate and manufacturing method thereof> The hybrid bonding substrate of the present invention is a hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, characterized in that the seed layer is provided between the base material and the copper plating layer and includes a nickel layer.

[0016] The hybrid bonding substrate of the present invention is also a hybrid bonding substrate comprising a substrate, a seed layer, and a copper plating layer, wherein the seed layer is provided between the substrate and the copper plating layer and includes one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer.

[0017] The method for manufacturing a hybrid bonding substrate of the present invention includes a seed layer formation step of forming a seed layer containing a nickel layer on the surface of a substrate, and a plating step of forming a copper plating layer on the seed layer. Note that in this specification, the terms "upper layer," "lower layer," "upper layer," etc., are based on a positional relationship in which the substrate is on the lower side and the side on which the seed layer or plating layer is formed is on the upper side, as shown in the drawings, and do not necessarily indicate a relationship with the direction of gravity during use, etc.

[0018] The method for producing a hybrid bonding substrate of the present invention also includes a seed layer formation step of forming a seed layer on the surface of a base material, the seed layer including one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer, and a plating step of forming a copper plating layer on top of the seed layer.

[0019] The manufacturing method of the present invention makes it possible to easily manufacture the above-described substrate for hybrid bonding of the present invention. The present invention also includes a substrate for hybrid bonding obtained by the manufacturing method of a substrate for hybrid bonding of the present invention.

[0020] By using the hybrid bonding substrate of the present invention for bonding, a structure can be formed in which the copper plating layers are well bonded to each other. Although the present invention is not limited by a particular theory, it is thought that the reason why the present invention is effective is that the nickel layer, or the cobalt layer, ruthenium layer, or molybdenum layer in the seed layer may affect the crystallinity of the copper plating layer.

[0021] Generally, metal layers such as nickel, cobalt, ruthenium, and molybdenum, especially nickel and cobalt layers, tend to have fine crystals. The copper plating layer formed on top of these layers may also contain many fine crystal grains due to the fine crystals of these metal layers. In fact, X-ray diffraction patterns of copper plating layers immediately after formation may show broader peaks than those of ordinary copper. Copper plating layers containing many fine crystal grains and with high grain boundary energy tend to leave ample room for the growth of copper crystalline phases within the layer when they are abutted against other copper plating layers and subjected to pressure and / or heat. Therefore, in the hybrid bonding substrate of the present invention, the copper crystalline phase and copper particles in the plating layer grow during bonding with other bonding substrates, potentially forming crystalline phases or particles that penetrate the surfaces (bonding surfaces) where the copper plating layers are superimposed. As a result, it is believed that the copper phase interface (bonding interface) that occurs at the bonding surface between the copper plating layers disappears in part or in whole, resulting in a good bond.

[0022] As will be shown in the examples below, in a bonded structure in which hybrid bonding substrates of the present invention are bonded together, copper particles or copper crystalline phases penetrating the bonding surface, and even copper particles or copper crystalline phases that have grown to a thickness exceeding the thickness of the original plating layer, are often observed. In other words, in many of these bonded structures, part or all of the bonding interface is lost, which can be expected to result in excellent bonding strength, conductivity, and the like. As will be described below, the present invention also encompasses hybrid bonding structures in which such copper particles or copper crystalline phases are present in the copper plating layer, for example, hybrid bonding structures in which the bonding interface is lost. However, the hybrid bonding substrate of the present invention will first be described in more detail below based on the embodiment shown in FIG. 1.

[0023] <One embodiment of a hybrid bonding substrate> FIG. 1 is a cross-sectional schematic diagram showing one embodiment of a hybrid bonding substrate of the present invention. The hybrid bonding substrate 1 of this embodiment includes a substrate 2, a seed layer 3, and a copper plating layer 4. In the hybrid bonding substrate 1, the seed layer 3 is provided between the substrate 2 and the copper plating layer 4. The seed layer 3 also includes a layer of one or more metals selected from the group consisting of nickel, cobalt, ruthenium, and molybdenum, preferably a nickel layer 6. For simplicity of explanation, the layer of one or more metals selected from the group consisting of nickel, cobalt, ruthenium, and molybdenum will be abbreviated as a "metal layer" below, and may also be represented by a "nickel layer," which is a particularly preferred embodiment. Unless otherwise specified, the explanation of the nickel layer also applies to the cobalt layer, the ruthenium layer, and the molybdenum layer.

[0024] 1 shows a cross section of only the conductive portion of the hybrid bonding substrate 1 for the purpose of explanation, but the hybrid bonding substrate of this embodiment may also include an insulating portion, etc. Furthermore, the conductive portion may also include a member other than the copper plating layer 4, such as a surface electrode or embedded electrode made of copper, silver, gold, etc. The shape of the substrate may not be a plate-like shape as shown in FIG. 1 but may have uneven or curved portions, such as through-holes, non-through-holes, via holes, trenches (grooves) for fine wiring, lands, embedded electrodes, penetrating electrodes, etc.

[0025] The hybrid bonding substrate of this embodiment may have any structure, and its configuration is not particularly limited, as long as it includes the seed layer 3 containing the above-mentioned metal layer, such as the nickel layer 6, together with the base material 2 and the copper plating layer 4. For example, it may have various shapes and include various conductive members, insulating members, and even semiconductor members in various configurations. The following will particularly describe the seed layer 3, which is an important component of this embodiment.

[0026] Seed Layer The hybrid bonding substrate of this embodiment is characterized by having a seed layer 3 including a metal layer of nickel, cobalt, ruthenium, molybdenum, or the like, especially a nickel and cobalt layer, and particularly a nickel layer 6. By providing such a seed layer, when bonding to another substrate, the copper plating layers 4 of the substrate and the copper plating layers 4 can be easily bonded to each other.

[0027] Although FIG. 1 shows the seed layer 3 as having a three-layer structure including the nickel layer 6, the seed layer of the hybrid bonding substrate of this embodiment is not limited to this configuration. For example, it may be composed of only one layer, such as the nickel layer 6, or may have a two-layer or four-layer or more structure including the nickel layer 6. In the embodiment shown in FIG. 1, the nickel layer 6 is thicker than the titanium layer 5 and thinner than the copper layer 7, but the thickness of each layer within the seed layer is not particularly limited. The configuration of the seed layer 3, such as the number of layers and thickness ratio, may vary from one portion to another within the same hybrid bonding substrate. In the hybrid bonding substrate of this embodiment, the seed layer 3 is only required to include the nickel layer 6, and other components are not particularly limited. Next, the nickel layer 6 will be described.

[0028] (nickel layer) The most important requirement for a particularly preferred hybrid bonding substrate of this embodiment is the inclusion of a nickel layer 6. The presence of the nickel layer 6 facilitates bonding of the upper copper plating layer 4. Depending on the type of substrate, the nickel layer 6 may also function as a barrier layer that prevents copper in the copper plating layer 4 from diffusing toward the base material 2.

[0029] The nickel layer 6 may be any layer containing nickel, and there are no particular limitations on its composition, crystal structure, etc. For example, it may be an alloy layer made of nickel and other metals such as chromium, cobalt, ruthenium, molybdenum, or tungsten. However, from the viewpoint of facilitating the formation of the copper plating layer 4 and improving the bonding between the copper plating layers 4, the proportion of nickel in the nickel layer 6 is, for example, 80 mass % or more, preferably 90 mass % or more, and particularly 95 mass % or more, and ideally almost the entire amount excluding unavoidable impurities.

[0030] (Cobalt layer, Ruthenium layer, Molybdenum layer) The hybrid bonding substrate of this embodiment may also include one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer, instead of or in addition to the nickel layer. Like the nickel layer, the metals constituting these layers may also be alloy layers made of other metals such as nickel, chromium, and tungsten. Preferably, these metal layers contain 80 mass % or more of cobalt, ruthenium, or molybdenum, ideally almost entirely, excluding unavoidable impurities.

[0031] There is no particular limitation on the thickness of these metal layers such as the nickel layer 6, and the desired thickness can be set depending on the intended use of the hybrid bonding substrate 1, the physical properties required of the structure after bonding, the material of the base material 2, and the thickness of the copper plating layer 4. However, from the viewpoint of improving the bonding properties of the copper plating layer 4 and achieving a narrow pitch, the thickness of the nickel layer 6 etc. is preferably 10 to 1000 nm, more preferably 30 to 500 nm, even more preferably 50 to 200 nm, and particularly preferably about 70 to 150 nm.

[0032] Such a nickel layer 6 and the like can be formed by any conventional method. Examples include, but are not limited to, electroless plating, vapor deposition, sputtering, and the like. Depending on the type of target substrate, they can also be formed by electrolytic plating. However, considering that the base material 2 may be an insulator, as described below, it is preferable to form the nickel layer 6 and the like by electroless plating, vapor deposition, or sputtering. Sputtering is particularly preferred because it can easily form a metal layer that has excellent adhesion to the underlying layer.

[0033] (Other layers in the seed layer) As described above, in the hybrid bonding substrate of this embodiment, the seed layer 3 may have any structure as long as it includes a metal layer such as the nickel layer 6, and may have, for example, a single-layer structure consisting of only the nickel layer 6. However, from the viewpoints of adhesion to the base material 2 and the copper plating layer 4, ease of forming the nickel layer 6 itself, and adhesion, it is preferable to provide a layer of another metal below and / or above the nickel layer 6.

[0034] For example, forming a layer of titanium, tantalum, copper, tungsten, or a nitride thereof as a lower layer of the nickel layer 6, etc., particularly as a layer in contact with the surface of the substrate, can facilitate the formation of the nickel layer 6, etc., or can further improve the bonding of the upper copper plating layer 4. Furthermore, forming a layer of copper or a copper alloy as an upper layer of the nickel layer 6, etc., particularly as a layer in contact with both the nickel layer 6 and the copper plating layer 4, can further facilitate the formation of the copper plating layer 4 and provide improved adhesion. The seed layer 3 can also have a two-layer structure consisting of such a lower or upper layer and the nickel layer 6, or a three-layer or greater structure including a lower layer and an upper layer. It is also possible to form multiple lower layers, nickel layers 6, etc., and / or upper layers. Instead of the nickel layer 6, a composite layer formed of two or more layers selected from a nickel layer, a cobalt layer, a ruthenium layer, and a molybdenum layer may be formed.

[0035] In the hybrid bonding substrate of this embodiment, the seed layer 3 is more preferably configured by laminating, in this order, a titanium layer 5 in contact with the surface of the base material 2, the nickel layer 6 or the like, and the copper layer 7. In particular, by forming the copper plating layer 4 in contact with the copper layer 7, it becomes easier to form the copper plating layer 4 and the bondability of the copper plating layer 4 can be further improved. Note that the titanium layer 5, the nickel layer 6 or the like, the copper layer 7, and the copper plating layer 4 may or may not be in contact with each other.

[0036] There are no particular limitations on the thickness of these lower and upper layers, and they can be set arbitrarily depending on the material of the substrate 2 and the thicknesses of the copper plating layer 4 and nickel layer 6. For example, the thickness of the lower layer may be 5 to 200 nm, preferably 10 to 100 nm, further 10 to 50 nm, and particularly about 20 to 50 nm, and the thickness of the upper layer may be 50 nm to 2 μm, preferably 100 nm to 1 μm, further 100 to 500 nm, and particularly about 200 to 500 nm.

[0037] In particular, when the seed layer 3 has a three-layer structure consisting of a titanium layer 5, a nickel layer 6, etc., and a copper layer 7, the thickness of the titanium layer 5 is, for example, 5 to 200 nm, preferably 10 to 100 nm, further 10 to 50 nm, and particularly about 20 to 50 nm; the thickness of the nickel layer 6, etc. is 10 to 1000 nm, preferably 30 to 500 nm, further 50 to 200 nm, and particularly about 70 to 150 nm; and the thickness of the copper layer 7 is 50 nm to 2 μm, preferably 100 nm to 1 μm, further 100 to 500 nm, and particularly about 200 to 500 nm, thereby providing advantages such as even better bonding of the copper plating layer 4.

[0038] The overall thickness of the seed layer 3 is preferably, for example, 10 nm to 3.2 μm, particularly 100 nm to 2.0 μm, further 200 nm to 1.0 μm, and particularly preferably about 400 to 800 nm, from the viewpoint of further improving the bondability of the upper copper plating layer 4.

[0039] The lower layer such as the titanium layer 5 and the upper layer such as the copper layer 7 can be formed by any conventional method, such as electroless plating, electrolytic plating, vapor deposition, or sputtering. The lower layer, the nickel layer 6, and the upper layer can also be formed by separate methods. From the standpoint of the bondability of the copper plating layer 4 and the ease of forming the seed layer 3, it is preferable to form all of the layers, for example, the lower layer such as the titanium layer 5, the nickel layer 6, and the upper layer such as the copper layer 7, by sputtering. However, the lower layer in particular may be formed by a method appropriate for the material of the substrate 2 on which it is to be formed. The substrate 2 on which the seed layer 3 is to be formed will be described below.

[0040] [Base material] The hybrid bonding substrate of this embodiment may have any structure as long as it has a seed layer 3 including a metal layer such as a nickel layer 6. Therefore, there are no particular limitations on the shape of the base material 2 that constitutes it. For example, base materials of various shapes and sizes can be used, such as plate-like base materials, film-like base materials, and base materials having irregularities including through holes, non-through holes, via holes, trenches, lands, embedded electrodes, penetrating electrodes, etc.

[0041] The material of the substrate 2 is not particularly limited. Various materials can be used depending on the purpose, such as semiconductors such as silicon and gallium arsenide, insulators such as glass and ceramics, and conductors such as metal. Flexible substrates using resins such as polyimide, polyamide, and polyester as the substrate may also be used. It is also possible to use composite materials combining multiple of these materials, such as a multilayer wiring board, as the substrate 2.

[0042] The surface of the substrate 2 on which the seed layer 3 and the copper plating layer 4 are to be formed may be modified by oxide film formation, physical or chemical etching, or the like. Surface modification facilitates the formation of the seed layer 3 and the copper plating layer 4 on the substrate 2 and can also further improve the adhesion between these layers. Next, the copper plating layer 4 formed on the seed layer will be described.

[0043] [Copper plating layer] The hybrid bonding substrate of this embodiment has a copper plating layer 4 on a seed layer 3 containing a nickel layer 6 and the like. In this embodiment, the term "copper plating layer" broadly refers to the entire plating layer containing copper and copper alloys, and also encompasses both electrolytically plated layers and electrolessly plated layers. From the perspective of further improving the bondability of the hybrid bonding substrate 1, it is preferable that the copper plating layer 4 be 70 mass % or more, particularly 80 mass % or more, and particularly 90 mass % or more, and ideally almost entirely, excluding unavoidable impurities, made of copper. Furthermore, it is preferably an electrolytic copper plating layer.

[0044] The thickness of the copper plating layer 4 is not particularly limited and may be set to a desired thickness depending on the intended substrate and bonding structure. For example, the thickness may be about 10 nm to 10 μm, particularly about 50 nm to 7 μm, or about 100 nm to 5 μm. The copper plating layer 4 may be formed in multiple layers, and may include, for example, an electroless copper plating layer and an electrolytic copper plating layer.

[0045] [Other materials] As described above, the hybrid bonding substrate of this embodiment includes the base material 2, the seed layer 3 including the nickel layer 6 and the like, and the copper plating layer 4, but may also include various other components such as an insulating member, a semiconductor member, a through electrode, and a barrier layer. Because the hybrid bonding substrate 1 of this embodiment has good bonding properties of the copper plating layer 4, good hybrid bonding between substrates can be achieved even in a structure in which such insulating members and / or semiconductor members are provided, particularly on the substrate surface.

[0046] <One embodiment of manufacturing a substrate for hybrid bonding> The hybrid bonding substrate can be manufactured through a seed layer formation process in which a seed layer 3 including a nickel layer 6 is formed on the surface of the base material 2 as described above, and a plating process in which a copper plating layer 4 is formed on top of the seed layer 3.

[0047] The hybrid bonding substrate can also be manufactured through a seed layer formation process of forming a seed layer 3 on the surface of a base material 2, the seed layer 3 including one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer, and a plating process of forming a copper plating layer 4 on top of the seed layer 3.

[0048] The method for manufacturing a substrate for hybrid bonding will be described below using a preferred embodiment as an example, but the method of the present invention is not limited to this embodiment and can be carried out using various conventional techniques and conditions. Prior to the seed layer formation step, the surface of the substrate 2 may be pretreated.

[0049] [Surface treatment of substrate] There are no particular limitations on the surface treatment method for the base material 2, and a desired method may be selected from among degreasing and cleaning with an organic solvent, cleaning with pure water (including a drying step if desired), cleaning to remove organic impurities using plasma containing oxygen, etc., depending on the material of the base material 2 and the desired substrate.

[0050] [Seed layer formation process] In the seed layer formation step, the seed layer 3 including the nickel layer 6 and the like may be formed on the substrate 2 by any method and under any conditions. Examples include, but are not limited to, techniques such as electroless plating, electrolytic plating, vapor deposition, and sputtering. From the viewpoints of ease of operation and the bondability of the copper plating layer 4 to be formed later, it is preferable to form the nickel layer 6 and the like by electroless plating, vapor deposition, or sputtering, particularly by sputtering.

[0051] Here, there is no particular limitation on the sputtering method, and it can be performed under desired conditions depending on the type of the target substrate and the material of the base material 2. For example, it can be performed using a magnetron sputtering device or the like.

[0052] The seed layer forming step is preferably carried out so that the thickness of the nickel layer 6 or the like is about 10 to 1000 nm, preferably about 30 to 500 nm, more preferably about 50 to 200 nm, and even more preferably about 70 to 150 nm.

[0053] In a more preferred embodiment, the seed layer formation step includes a step of forming a titanium layer 5 in contact with the surface of the substrate 2, a step of forming the nickel layer 6 or the like as an upper layer on the titanium layer 5, and a step of forming a copper layer 7 as an upper layer on the nickel layer 6 or the like. Like the nickel layer 6, the titanium layer 5 and the copper layer 7 can be formed by electroless plating, electrolytic plating, vapor deposition, sputtering, or the like, but it is preferable to form both by sputtering. Here, the titanium layer 5, the nickel layer 6, or the like, and the copper layer 7 and the copper plating layer 4 may be formed so as to be in contact with each other, or may be formed with another layer, such as a layer of another metal, sandwiched between them.

[0054] It is preferable that the steps of forming the titanium layer 5 and the copper layer 7 are carried out so that the thickness of the titanium layer 5 is, for example, 5 to 200 nm, preferably 10 to 100 nm, further 10 to 50 nm, and particularly about 20 to 50 nm, as described above, and the thickness of the copper layer 7 is, for example, 50 nm to 2 μm, preferably 100 nm to 1 μm, further 100 to 500 nm, and particularly about 200 to 500 nm.

[0055] [Plating process] Next, in the plating step, a copper plating layer 4 is formed on the seed layer 3 obtained as described above. In the plating step, electrolytic plating is preferably used, but electroless plating may also be employed, and any method can be used depending on the material of the base material 2 and the desired properties. It is also possible to perform both electroless copper plating and electrolytic copper plating.

[0056] There are no particular restrictions on the copper plating conditions. Depending on the physical properties of the desired copper plating layer 4, various plating solutions containing copper ions, such as a general-purpose copper sulfate plating solution, may be used, for example, at a solution temperature of about 20 to 40°C and a cathode current density of 0.05 to 20 A / dm 2 Plating can be carried out under conventional conditions, such as the degree of plating. The plating time can be set appropriately depending on the purpose of plating. Furthermore, during plating, the solution may be agitated by aeration, pump circulation, paddle stirring, etc.

[0057] [Other processes] In the method for producing a hybrid bonding substrate of this embodiment, pretreatments such as degreasing, water washing, cleaning, plasma treatment, etc. may be performed before the above-mentioned surface treatment step, seed layer formation step, and plating step. Furthermore, after plating, operations such as application of a solder resist or the like, rust prevention treatment, planarization by CMP or the like, cleaning, and even formation of a plating layer other than copper may be performed.

[0058] The hybrid bonding substrate manufactured in this manner has excellent bonding properties in the copper plating layer, and therefore a structure with a good bonding state can be produced. The hybrid bonding structure of the present invention will be described below.

[0059] <Hybrid joint structure and manufacturing method thereof> The hybrid junction structure can be produced by overlapping and joining two of the above-mentioned hybrid junction substrates with their copper plating layers facing each other, as shown in FIG. 2, for example.

[0060] The present invention also includes a hybrid bonding structure in which substrates each having a base material, a seed layer, and a copper plating layer are bonded together via the copper plating layer, and in each substrate, a seed layer is provided between the base material and the copper plating layer and includes a nickel layer.

[0061] The present invention also encompasses a hybrid joint structure in which substrates each having a base material, a seed layer, and a copper plating layer are joined via the copper plating layer, wherein in each substrate, a seed layer is provided between the base material and the copper plating layer and includes one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer. The hybrid joint structure of the present invention will be described in more detail below based on the embodiment shown in FIG.

[0062] <One embodiment of hybrid joint structure> 3 is a cross-sectional schematic diagram showing one embodiment of the hybrid joint structure of the present invention. The hybrid joint structure 10 of this embodiment includes a substrate 12 based on each of the joined substrates, a seed layer 13, and a copper plating layer 14. In the hybrid joint structure 10, each seed layer 13 is provided between the substrate 12 and the copper plating layer 14. Each seed layer 13 also includes one or more layers selected from the group consisting of a nickel layer, a cobalt layer, a ruthenium layer, and a molybdenum layer, preferably a nickel layer 16.

[0063] 3 shows a cross section of only the conductive portion of the hybrid junction structure 10 for the sake of explanation, but the hybrid junction structure of this embodiment may, like the hybrid junction substrate, include insulating members, semiconductor members, surface electrodes, embedded electrodes, through holes, non-through holes, via holes, trenches (grooves) for fine wiring, lands, penetrating electrodes, solder resist layers, plating layers other than copper, etc. Furthermore, the two base materials 12 and seed layers 13 may be the same as shown in FIG. 3, or may be different in material, shape, and / or thickness.

[0064] The substrate 12, seed layer 13, and copper plating layer 14 in the hybrid bonding structure of this embodiment are the same as the substrate 2, seed layer 3, and copper plating layer 4 in the hybrid bonding substrate 1 described above. For example, the seed layer 13 may have a single-layer structure consisting of only a nickel layer 16 or the like, or may have a titanium layer 15 or the like as an underlying layer of the nickel layer 16 or the like, or may have a copper layer 17 or the like as an upper layer of the nickel layer 16 or the like. It is also possible to form multiple layers of the underlying layer, nickel layer 16 or the like, and / or upper layer.

[0065] In the hybrid junction structure of this embodiment, similarly to the hybrid junction substrate 1, the thickness of the nickel layer 16 etc. is preferably about 10 to 1000 nm, more preferably 30 to 500 nm, even more preferably 50 to 200 nm, and particularly preferably about 70 to 150 nm.

[0066] In the hybrid bonding structure of this embodiment, similarly to the hybrid bonding substrate 1, the seed layer 13 is preferably configured by laminating a titanium layer 15 in contact with the surface of the base material 12, the nickel layer 16 and the like, and a copper layer 17 in this order. The titanium layer 15, the nickel layer 16 and the like, the copper layer 17, and the copper plating layer 14 may or may not be in contact with each other. The thickness and material of each metal layer are also similar to those in the hybrid bonding substrate 1.

[0067] In the hybrid joint structure of this embodiment, copper particles and copper crystalline phases often penetrate the joint surface in the joined copper plating layer 14 and even grow to a size in the thickness direction that exceeds the thickness of the original plating layer. The dashed line P in FIG. 3 represents an imaginary plane (imaginary parallel plane) that corresponds to the joint surface when the substrates are overlapped during joining. As will be shown in the examples described later, in the hybrid joint structure of this embodiment, part or all of the interface (joining interface) at the time of joining often disappears from this imaginary parallel plane P. This is why the term "imaginary parallel plane" is used to correspond to the "joining surface." In a more preferred embodiment, the joint interface almost completely disappears, and the copper plating layer 14 can become a single phase macroscopically, as shown in FIG. 3.

[0068] 4 and 5 are photographs of SIM images of Example 1 according to this embodiment and Comparative Example 1, which does not have the nickel layer 6, respectively. In the hybrid joint structure according to this embodiment, the copper crystal phase grows significantly in the copper plating layer as shown in FIG. 4, and the joint interface as shown in FIG. 5 disappears.

[0069] A particularly preferred embodiment of the hybrid joint structure will be described with reference to Fig. 6. In the embodiment of Fig. 6, the substrates are composed of Substrate-1 with a copper plating layer thickness t1 and Substrate-2 with a copper plating layer thickness t2. In the copper plating layer 14 of the joint structure, copper crystalline phases are provided that penetrate both a parallel plane P1 of Substrate-1, which is located at a distance t1 from an end face 21 of the copper plating layer on the Substrate-1 side, and a parallel plane P2 of Substrate-2, which is located at a distance t2 from an end face 22 of the copper plating layer on the Substrate-2 side (which, as will be described later, approximately coincide with the imaginary parallel plane P and the joint surface). In these copper crystalline phases, grain boundaries intersect with the joint surface, and the thickness dimension is sometimes larger than the thicknesses (t1, t2) of the plating layers of the substrates before joining.

[0070] Note that parallel planes P1 and P2 in FIG. 6 are imaginary planes that are parallel to the copper-plated surfaces of Substrate-1 and Substrate-2 before bonding, respectively, at the same positions (heights t1 and t2) as the copper-plated surfaces of Substrate-1 and Substrate-2 before bonding. Because the copper-plated layer becomes slightly thinner due to the pressure applied during bonding, P1 and P2 are drawn slightly offset from the position of bonding surface 23. To illustrate this point, FIG. 6 is slightly exaggerated; in reality, both parallel planes P1 and P2 almost coincide with bonding surface 23 (imaginary parallel plane P in FIG. 3). In the embodiment of FIG. 6, parallel planes P1 and P2 (and therefore bonding surface 23) intersect with the grain boundaries of the copper crystalline phase, and the bonding interface disappears to the extent that it cannot be discerned in the cross-sectional photograph.

[0071] In other words, a particularly preferred embodiment is a hybrid joint structure in which the substrates consist of substrate-1 having a copper plating layer thickness t1 and substrate-2 having a copper plating layer thickness t2, and in the copper plating layer 14 of the joint structure, there is provided a copper crystalline phase having grain boundaries that intersect with both: a parallel plane P1 of substrate-1, which is assumed to be located t1 away from end face 21 of the copper plating layer on the substrate-1 side; and a parallel plane P2 of substrate-2, which is assumed to be located t2 away from end face 22 of the copper plating layer on the substrate-2 side.

[0072] As described above, the hybrid joint structure of this embodiment comprises the substrate 12, the seed layer 13 including the nickel layer 16, etc., and the copper plating layer 14, but may also comprise various other components such as insulating members and semiconductor members, as well as through holes, non-through holes, via holes, trenches, lands, embedded electrodes, penetrating electrodes, solder resist layers, and plating layers other than copper.

[0073] <One embodiment of the joining method> As described above, the hybrid bonding structure can be manufactured by, for example, overlapping and bonding two hybrid bonding substrates with a copper plating layer interposed therebetween. One embodiment of the present invention is a method for bonding substrates each including a base material, a seed layer, and a copper plating layer, the method including using the above-described hybrid bonding substrate as the substrate and overlapping and hybrid bonding the two substrates with the copper plating layer interposed therebetween.

[0074] As a similar embodiment, there can be mentioned a method for manufacturing a hybrid joint structure formed by hybrid-joining substrates each having a base material, a seed layer, and a copper plating layer, the method including using the above-mentioned hybrid bonding substrate as the substrate and joining the two substrates together via the copper plating layer. These methods will be described below based on the embodiment shown in FIG. 2.

[0075] Figure 2 is an explanatory diagram showing one embodiment of the bonding method (which is also a method for producing a hybrid bonded structure). First, two hybrid bonding substrates 1 are stacked together with their copper plating layers 4 interposed between them, as shown in Figure 2(a). Next, as shown in Figure 2(b), pressure is applied and, if necessary, heating is performed to bond the substrates 1 together, thereby producing a hybrid bonded structure 10, as shown in Figure 2(c), in which the copper plating layers are preferably integrated. Here, the insulating members 8 may also be integrated together.

[0076] The bonding step in these embodiments can be a (hybrid) bonding step in which a pressure of, for example, 0.1 to 30 MPa, particularly 0.2 to 15 MPa, and particularly 0.3 to 13 MPa is applied. The bonding step can also be carried out at a temperature of, for example, 100 to 700°C, particularly 200 to 600°C, and particularly 300 to 500°C. The pressure application time in the bonding step varies depending on the pressure and temperature conditions, but can generally be about 15 minutes to 10 hours, particularly 30 minutes to 5 hours, and particularly 1 to 3 hours.

[0077] <Another embodiment of the joining method> The hybrid bonded structure of this embodiment can also be manufactured by a method for manufacturing a hybrid bonded structure formed by hybrid-bonding substrates each having a base material, a seed layer, and a copper plating layer, the method including: a substrate manufacturing process for manufacturing the substrate by carrying out the above-described method for manufacturing a hybrid bonded substrate; and a bonding process for overlapping and bonding the two manufactured substrates via the copper plating layer. The materials and thicknesses of each layer that can be used in this manufacturing process, and the temperature, pressure, and other conditions in the bonding process can be the same as those in the previously described embodiment.

[0078] [Preprocessing] When manufacturing the hybrid bonding structure and bonding the hybrid bonding substrate, the copper plating layer 4 (and the insulating member 8, if desired) may be subjected to pretreatments such as cleaning, anti-rust treatment, planarization by CMP or the like, plasma treatment, etc. These pretreatments can further improve the bonding properties of the copper plating layer.

[0079] <Applications of hybrid joint structures> In the hybrid bonded structure manufactured as described above, the bonding state via the copper plating layer is good, and excellent bonding strength and conductivity can be expected. Furthermore, since high temperature and high pressure conditions are often not required for bonding, thermal degradation of each component is unlikely to occur. Therefore, the hybrid bonded structure of this embodiment is useful for various semiconductor substrates, semiconductor manufacturing equipment components, automotive control boards, computer components, medical device control boards, and various other printed circuit boards. [Example]

[0080] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these descriptions in any way.

[0081] Example 1 A thermal oxide film was formed on the surface of a silicon wafer with a diameter of 200 mm and a thickness of 750 μm. Next, a magnetron sputtering device (Charger UBM PVD manufactured by APPLIED MATERIALS) was used to form a 30 nm thick titanium layer, a 100 nm thick nickel layer, and a 400 nm thick copper layer as seed layers on one side of the silicon wafer. Next, a general-purpose copper sulfate plating solution was used, and the cathode current density was 1 A / dm. 2 Copper plating was carried out for 22 minutes and 30 seconds under conditions of a liquid temperature of 25°C, to form a copper plating layer having a thickness of 5 µm on the seed layer.

[0082] The hybrid bonding substrates obtained as described above were stacked together with the copper-plated layers facing inward, and then heat-treated at 400°C under a pressure of 0.48 MPa for two hours to produce a bonded structure. Figure 4 shows an example of a SIM image of the resulting hybrid bonded structure. This SIM image was obtained using a Hitachi High-Technologies FB-2100 focused ion beam (FIB) system. The copper crystal phase observation results based on the SIM image are shown in Table 1, which will be described later.

[0083] Comparative Example 1 Except for not forming a nickel layer as a seed layer, the same operation as in Example 1 was carried out. An example of a SIM image of the obtained hybrid joint structure is shown in Figure 5, and the observation results are shown in Table 1 below.

[0084] Examples 2 to 4 The same operations as in Example 1 were carried out, except that the thickness of the nickel layer in the seed layer and the bonding conditions were changed as shown in Table 1 below. The results of observation of the copper crystal phase based on SIM images of the obtained hybrid bonded structure are shown in Table 1 below.

[0085] Example 5 The same operations as in Example 1 were carried out, except that a 30 nm thick titanium layer, a 100 nm thick copper layer, a 100 nm thick nickel layer, and a 400 nm thick copper layer were formed in this order as seed layers, and the nickel layer was formed by electroless plating (seed layers other than the nickel layer were formed by sputtering). The electroless plating was carried out for 1 minute and 30 seconds at a solution temperature of 35°C. The observation results of the copper crystalline phase are shown in Table 1.

[0086] [Table 1]

[0087] In the hybrid bonding structures of Examples 1 to 5, which have a nickel layer as a seed layer according to the present invention, disappearance of the bonding interface was observed, as shown in Figure 4. On the other hand, in the hybrid bonding structure of Comparative Example 1, which does not have a nickel layer, the interface at the time of bonding remained over the entire area, as shown in Figure 5. It was shown that in the hybrid bonding substrate provided with a seed layer containing a nickel layer according to the present invention, the conductive parts formed by plating were sufficiently bonded to each other, and a hybrid bonding structure with a good bonding state was obtained.

[0088] In the hybrid bonding structure according to the present invention, as shown in Fig. 6, copper crystalline phases were observed penetrating the imaginary parallel planes P1 and P2 (including the bonding surface 23). In addition, the thickness of some of the crystalline phases was greater than the plating layer thicknesses t1 and t2 before bonding. This suggests that in the hybrid bonding substrate according to the present invention, the copper crystalline phase in the copper plating layer is more likely to grow during bonding. [Explanation of symbols]

[0089] 1. Hybrid bonding substrate 2 Base material 3 Seed layer 4 Copper plating layer 5 titanium layers 6 Nickel layer 7 copper layers 8 Insulating material 10 Hybrid joint structure 12 Base material 13 Seed layer 14 Copper plating layer 15 titanium layer 16 Nickel layer 17 copper layer 21, 22 End surface of copper plating layer 23 Joint surface P Virtual parallel plane P1 Parallel surface of board-1 P2 Parallel surface of board-2

Claims

1. A method for manufacturing a hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, comprising: a seed layer forming step of forming the seed layer including a nickel layer on the surface of the base material; a plating step of forming the copper plating layer on the seed layer; A method for manufacturing a substrate for hybrid bonding, comprising:

2. A method for manufacturing a hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, comprising: a seed layer forming step of forming the seed layer on the surface of the substrate, the seed layer including one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer; a plating step of forming the copper plating layer on the seed layer; A method for manufacturing a substrate for hybrid bonding, comprising:

3. The seed layer forming step includes: forming a titanium layer in contact with the surface of the substrate; forming the nickel layer as an upper layer of the titanium layer; and forming a copper layer as an upper layer of the nickel layer. A method for producing the hybrid bonding substrate according to claim 1.

4. In the seed layer forming step, the nickel layer is formed by sputtering. A method for producing the substrate for hybrid bonding according to claim 1 or 3.

5. A hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, the seed layer is provided between the substrate and the copper plating layer and includes a nickel layer; Substrate for hybrid bonding.

6. A hybrid bonding substrate comprising a base material, a seed layer, and a copper plating layer, the seed layer is provided between the substrate and the copper plating layer, and includes one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer; Substrate for hybrid bonding.

7. the seed layer is formed by laminating a titanium layer in contact with the surface of the base material, the nickel layer, and a copper layer in this order; The hybrid bonding substrate according to claim 5 .

8. A method for manufacturing a hybrid bonded structure formed by hybrid bonding substrates each having a base material, a seed layer, and a copper plating layer, comprising: The hybrid bonding substrate according to any one of claims 5 to 7 is used as the substrate, a bonding step of overlapping and bonding the two substrates via the copper plating layer, A method for manufacturing a hybrid joint structure.

9. A method for manufacturing a hybrid bonded structure formed by hybrid bonding substrates each having a base material, a seed layer, and a copper plating layer, comprising: a substrate manufacturing process in which the substrate is manufactured by carrying out the method according to any one of claims 1 to 3; a bonding step of overlapping and bonding the two manufactured substrates with the copper plating layer interposed therebetween; A method for manufacturing a hybrid joint structure, comprising:

10. In the bonding step, bonding is performed by applying a pressure of 0.1 to 30 MPa. The method for manufacturing the hybrid joint structure according to claim 8 .

11. A hybrid bonding structure in which substrates each having a base material, a seed layer, and a copper plating layer are bonded together via the copper plating layer, In each of the substrates, the seed layer is provided between the substrate and the copper plating layer and includes a nickel layer; Hybrid joint structure.

12. A hybrid bonding structure in which substrates each having a base material, a seed layer, and a copper plating layer are bonded together via the copper plating layer, In each of the substrates, the seed layer is provided between the substrate and the copper plating layer and includes one or more layers selected from the group consisting of a cobalt layer, a ruthenium layer, and a molybdenum layer; Hybrid joint structure.

13. In each of the substrates, the seed layer is formed by laminating a titanium layer in contact with the surface of the base material, the nickel layer, and a copper layer in this order; The hybrid joint structure according to claim 11.

14. The hybrid joint structure according to any one of claims 11 to 13, wherein the substrates are composed of a substrate-1 having a copper plating layer thickness t1 and a substrate-2 having a copper plating layer thickness t2; In the copper plating layer, a parallel plane P1 of the substrate-1, which is imagined at a position t1 away from the end face of the copper plating layer on the substrate-1 side; and a parallel plane P2 of the substrate-2, which is imagined at a position t2 away from the end face of the copper plating layer on the substrate-2 side; A hybrid bonded structure with a copper crystalline phase that penetrates both the metal and the alloy.

15. A method for bonding substrates each having a base material, a seed layer, and a copper plating layer, comprising: The hybrid bonding substrate according to any one of claims 5 to 7 is used as the substrate, a step of overlapping and hybrid-bonding the two substrates via the copper plating layer, Method of joining boards.

16. In the above step, hybrid bonding is performed by applying a pressure of 0.1 to 30 MPa. The method for bonding substrates according to claim 15.

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