Hybrid joining method

Abstract

This hybrid joining method is a method for joining: a first joining object comprising a first joining surface that includes both a first dielectric portion and a first metal electrode portion; and a second joining object comprising a second joining surface that includes both a second dielectric portion and a second metal electrode portion. The hybrid joining method includes: a first monomolecular film formation step for using a first surface treatment liquid having a pH of 5.0 or less to form a first self-assembling monomolecular film on the first metal electrode portion of the first joining surface; a second monomolecular film formation step for using a second surface treatment liquid having a pH of 5.0 or less to form a second self-assembling monomolecular film on the second metal electrode portion of the second joining surface; and a heating step for stacking and heating the first joining surface of the first joining object and the second joining surface of the second joining object.

Description

Hybrid Joining Method

[0001] The present disclosure relates to hybrid joining methods.

[0002] The development of bonding methods is extremely important in the three-dimensional integration of semiconductor devices. Hybrid bonding, a lamination method that directly bonds wafers or chips (dies) to each other, has attracted attention in recent years because it enables shortening of wiring distances and increasing I / O (input / output) density, thereby improving power efficiency and system performance.

[0003] In hybrid bonding, surface activation of the bonding surfaces prior to bonding can increase the bonding strength and lower the bonding temperature. For example, Patent Document 1 discloses a technology in which the surfaces of the substrates are modified by plasma treatment and then hydrophilized, thereby bonding the substrates with an appropriate bonding strength.

[0004] Japanese Patent Application Laid-Open No. 2014-138136

[0005] However, surface activation by plasma treatment can cause problems such as roughening of the metal electrodes exposed at the bonding surface or oxidation to form an oxide film. Furthermore, even without plasma treatment, there is the problem of a natural oxide film inevitably forming on the metal electrodes. Therefore, electrical continuity between the bonded electrodes may not be achieved, resulting in insufficient reliability of the electrical connection between the electrodes.

[0006] An object of the present disclosure is to provide a hybrid joining method that can achieve good electrical connection reliability between electrodes.

[0007] As a result of extensive research, the inventors of the present disclosure have found that the above-mentioned problems can be solved by forming a self-assembled monolayer on the metal electrode portion at the bonding surface.

[0008] [1] A method for joining a first joining object having a first joining surface having a first dielectric portion and a first metal electrode portion, and a second joining object having a second joining surface having a second dielectric portion and a second metal electrode portion, the hybrid joining method comprising: a first monolayer forming step of forming a first self-assembled monolayer on the first metal electrode portion of the first joining surface by bringing a first surface treatment liquid into contact with the first metal electrode portion; a second monolayer forming step of forming a second self-assembled monolayer on the second metal electrode portion of the second joining surface by bringing a second surface treatment liquid into contact with the second metal electrode portion; and a heating step of overlapping and heating the first joining surface of the first joining object and the second joining surface of the second joining object, wherein the first surface treatment liquid contains a first self-assembled monolayer material and has a pH of 5.0 or less; and the second surface treatment liquid contains a second self-assembled monolayer material and has a pH of 5.0 or less. [2] The hybrid bonding method according to [1], wherein one or both of the first self-assembling monolayer material and the second self-assembling monolayer material is an azole compound (preferably a benzotriazole compound) which may have a substituent. [3] The substituent is a carboxy group, *-N(R １ ) ２ and *—Si(OR ２ ) ３ an alkyl group having 1 to 15 carbon atoms which may have one or more functional groups selected from the group consisting of groups represented by the formula ３ ) ２ (preferably an alkyl group having 1 to 15 carbon atoms which may have the functional group, more preferably an unsubstituted alkyl group having 1 to 15 carbon atoms), and R １ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a hydroxyalkyl group having 1 to 6 carbon atoms; R ２ are each independently an alkyl group having 1 to 4 carbon atoms, ３are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. [4] The hybrid bonding method according to any one of [1] to [3], in which plasma treatment of the first dielectric portion is not performed before the first monomolecular film forming step, and plasma treatment of the second dielectric portion is not performed before the second monomolecular film forming step. [5] The hybrid bonding method according to any one of [1] to [4], in which one or both of the first self-assembled monolayer and the second self-assembled monolayer have a thickness of 0.3 nm to 10 nm. [6] The hybrid bonding method according to any one of [1] to [5], in which one or both of a first plasma treatment step of plasma treating the first dielectric portion after the first monomolecular film forming step and a second plasma treatment step of plasma treating the second dielectric portion after the second monomolecular film forming step are included. [7] The hybrid bonding method according to any one of [1] to [6], in which the first metal electrode portion and the second metal electrode portion are formed of copper. [8] The hybrid bonding method according to any one of [1] to [7], wherein the first dielectric portion and the second dielectric portion are formed of silicon oxide. [9] The hybrid bonding method according to any one of [1] to [8], wherein the first bonding object and the second bonding object are each a wafer or a chip.

[10] A method for manufacturing an integrated circuit, comprising the hybrid bonding method according to any one of [1] to [9].

[11] A method for manufacturing a semiconductor device, comprising the hybrid bonding method according to any one of [1] to [9].

[0009] According to the present disclosure, it is possible to provide a hybrid joining method that can achieve good electrical connection reliability between electrodes.

[0010] FIG. 1 is a cross-sectional schematic diagram of a joining target used in a hybrid joining method according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional schematic diagram of a joined body obtained by a hybrid joining method according to an embodiment of the present disclosure. FIG. 3 is a surface chemical structure analysis result of a surface-treated sample obtained in Experimental Example 1 and a surface-untreated sample obtained in Comparative Experimental Example 1. FIG. 4 is an AFM topography image (photograph as a substitute for a drawing) of the surface-treated sample obtained in Experimental Example 1. FIG. 5 is an AFM topography image (photograph as a substitute for a drawing) of the surface-untreated sample obtained in Comparative Experimental Example 1. FIG. 6 is a graph showing the IV characteristics of the joined body obtained in Example 1 and the joined body obtained in Comparative Example 1 before an aging test. FIG. 7 is a graph showing the IV characteristics of the joined body obtained in Example 1 and the joined body obtained in Comparative Example 1 after an aging test. FIG. 8 is a cross-sectional SEM image (photograph as a substitute for a drawing) of the joined body obtained in Example 1.

[0011] Specific embodiments of the present disclosure will be described in detail below. The present disclosure is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present disclosure. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0012] In the present disclosure, the range "X to Y" means "X or more and Y or less." Furthermore, when a numerical range expressed as "X to Y" or "X or more and Y or less" is described in stages (for example, in order of preference), the upper and lower limits of each numerical range can be combined in any way.

[0013] In the present disclosure, a description such as "X such as x1, x2, and x3" lists x1, x2, and x3 as examples of X, and does not mean that X is limited to x1, x2, x3, and the like.

[0014] [Hybrid Bonding Method] A hybrid bonding method according to an embodiment of the present disclosure is a method for bonding a first object to be joined, the first object having a first bonding surface having a first dielectric portion and a first metal electrode portion, to a second object to be joined, the second object having a second bonding surface having a second dielectric portion and a second metal electrode portion, the hybrid bonding method including: a first monolayer forming step of forming a first self-assembled monolayer on the first metal electrode portion on the first bonding surface by bringing a first surface treatment liquid into contact with the first metal electrode portion; a second monolayer forming step of forming a second self-assembled monolayer on the second metal electrode portion on the second bonding surface by bringing a second surface treatment liquid into contact with the second metal electrode portion; and a heating step of overlapping the first bonding surface of the first object to be joined and the second bonding surface of the second object to be joined and heating them.

[0015] 1. Bonding Objects The first bonding object has a first semiconductor substrate and a first dielectric layer formed on the first semiconductor substrate, with a first metal electrode embedded in it. The first bonding surface of the first bonding object, which is bonded to the second bonding surface of the second bonding object, has a first dielectric portion which is the surface of the first dielectric layer, and a first metal electrode portion which is the surface of the first metal electrode exposed from the first dielectric layer.

[0016] FIG. 1 shows an example of a cross-sectional view of a first bonding object 100 taken in a direction perpendicular to a first bonding surface. In FIG. 1 , the first bonding object 100 includes a first semiconductor substrate 101 and a first dielectric layer 103 located on the first semiconductor substrate 101. A first metal electrode 105 is embedded in the first bonding object 100 so as to penetrate the first dielectric layer 103. A first bonding surface 110 of the first bonding object 100 includes a first dielectric portion 113 corresponding to a surface portion of the first dielectric layer 103 and a first metal electrode portion 115 corresponding to a surface portion of the first metal electrode 105. The first bonding object 100 may include other components not shown in FIG. 1 . Examples of such other components include various circuits and barrier metal layers such as titanium layers and titanium nitride layers. The barrier metal layer is formed between the first metal electrode 105 and the first semiconductor substrate 101 and the first dielectric layer 103. Also, although the number of first metal electrodes shown is one, it goes without saying that the number can be two or more.

[0017] The first semiconductor substrate is not particularly limited, and any semiconductor substrate can be used, such as a silicon substrate, a germanium substrate, a sapphire substrate, a silicon carbide substrate, a gallium nitride substrate, a gallium arsenide substrate, etc. Of these, the first semiconductor substrate is preferably a silicon substrate, since this facilitates bonding at a narrow pitch.

[0018] The material for forming the first dielectric layer is not particularly limited, and examples thereof include amorphous silicon, silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxide, with silicon oxide being preferred. When the first semiconductor substrate is a silicon substrate, it is particularly preferred that the first dielectric layer be formed from silicon oxide because of its high affinity with the silicon substrate.

[0019] Since the first dielectric portion at the first bonding surface corresponds to the surface portion of the first dielectric layer, the material forming the first dielectric portion is synonymous with the material forming the first dielectric layer.

[0020] The thickness of the first dielectric layer is not particularly limited, but is preferably 300 nm or more and 3,000 nm or less, more preferably 500 nm or more and 2,000 nm or less, and even more preferably 1,000 nm or more and 1,500 nm or less.

[0021] Examples of metal materials for forming the first metal electrodes include silver, copper, gold, aluminum, nickel, tungsten, titanium, and tin. Each of the first metal electrodes may be formed of a single metal or an alloy containing multiple metals, but is preferably formed of a single metal, and more preferably copper because of its excellent electrical and thermal conductivity. Furthermore, the first metal electrode is preferably formed of the same metal material as the second metal electrode.

[0022] In addition, since the first metal electrode portion on the first bonding surface corresponds to the portion of the first metal electrode that is exposed on the bonding surface, the material forming the first metal electrode portion is synonymous with the material forming the first metal electrode.

[0023] The first metal electrode portion may be recessed at the first bonding surface. This recess is generally called dishing. The recess in the first metal electrode portion is eliminated by thermal expansion of the first metal electrode during the heating process, and the first metal electrode contacts the second metal electrode portion of the second metal electrode, which has also expanded. This causes solid-state diffusion of metal atoms, resulting in bonding between the metal electrodes. The amount of dishing can be controlled depending on the metal material forming the first metal electrode, the heating temperature, and other factors.

[0024] The first bonding object can be fabricated by a damascene method, that is, by digging a groove in the first dielectric layer of a stack having a first semiconductor substrate and a first dielectric layer, filling the groove with a metal material that will form the first metal electrode, and then planarizing the surface by chemical mechanical polishing (CMP).

[0025] The second joining object is synonymous with the first joining object. Therefore, in describing the second joining object, the description of the first joining object is used by replacing "first joining object" with "second joining object," "first semiconductor substrate" with "second semiconductor substrate," "first dielectric layer" with "second dielectric layer," "first dielectric portion" with "second dielectric portion," "first metal electrode" with "second metal electrode," "first metal electrode portion" with "second metal electrode portion," "first joining surface" with "second joining surface," "second joining object" with "first joining object," "second joining surface" with "first joining surface," "second metal electrode" with "first metal electrode," and "second metal electrode portion" with "first metal electrode portion."

[0026] The hybrid bonding method according to this embodiment can be preferably applied to any of wafer-to-wafer bonding (Wafer to Wafer (W to W)), chip-to-chip bonding (Chip to Chip (C to C)), and chip-to-wafer bonding (Chip to Wafer (C to W)). Therefore, the first and second bonding objects are preferably wafers or chips, respectively. The hybrid bonding performed in this embodiment is wafer-to-wafer bonding if the first and second bonding objects are both wafers, chip-to-chip bonding if the first and second bonding objects are both chips, and chip-to-wafer bonding if the first bonding object is a wafer and the second bonding object is a chip, or if the first bonding object is a chip and the second bonding object is a wafer.

[0027] In this disclosure, the term "wafer" refers to a wafer used for integrated circuits, etc., in which metal electrodes are embedded in a laminate having a semiconductor substrate and a dielectric layer, and a circuit is formed as needed. In addition, in this disclosure, the term "chip" refers to a semiconductor chip cut out by dicing a wafer.

[0028] 2. First Monolayer Forming Step and Second Monolayer Forming Step The first monolayer forming step is a step of forming a first self-assembled monolayer (hereinafter sometimes referred to as "first SAM") on the first metal electrode portion by contacting the first surface treatment liquid with the first metal electrode portion. The second monolayer forming step is a step of forming a second self-assembled monolayer (hereinafter sometimes referred to as "second SAM") on the second metal electrode portion by contacting the second surface treatment liquid with the second metal electrode portion. The first SAM is a monolayer of the first SAM material. The second SAM is a monolayer of the second SAM material.

[0029] The first monolayer formation step and the second monolayer formation step may be the same step. That is, the bonding targets with SAMs obtained in one monolayer formation step may be used as the first bonding target and the second bonding target. Furthermore, in the first monolayer formation step, one or more first SAMs may be further deposited on the first SAM on the first metal electrode portion. Similarly, in the second monolayer formation step, one or more second SAMs may be further deposited on the second SAM on the second metal electrode portion.

[0030] The first surface treatment liquid is an acidic surface treatment liquid containing a first SAM material and having a pH of 5.0 or less. The second surface treatment liquid is an acidic surface treatment liquid containing a second SAM material and having a pH of 5.0 or less. In this disclosure, unless otherwise specified, "pH" refers to the pH at 20°C.

[0031] In this embodiment, as described below, the first SAM and the second SAM perform multiple functions during the formation stage (i.e., the surface treatment stage) and after formation, and can provide various effects (hereinafter, the first SAM and the second SAM may be collectively referred to as "SAMs". Furthermore, the first joining object and the second joining object may be collectively referred to as "joining objects", the first metal electrode portion and the second metal electrode portion may be collectively referred to as "metal electrode portions", and the first surface treatment liquid and the second surface treatment liquid may be collectively referred to as "surface treatment liquids").

[0032] First, the SAM formed on the metal electrode portion functions as a protective layer for the metal electrode portion. Protecting the metal electrode portion with the SAM can suppress natural oxidation of the metal electrode portion. Furthermore, protecting the metal electrode portion with the SAM can suppress oxidation and roughening of the metal electrode portion due to surface treatment, such as plasma treatment, even if the joining target is subjected to a surface treatment after SAM formation. Therefore, by forming a SAM on the metal electrode portion, solid-state diffusion of metal atoms between the metal electrodes can proceed smoothly without being hindered during hybrid joining, resulting in a joint with high reliability of electrical connection between the metal electrodes. Furthermore, protecting the metal electrode portion with the SAM can achieve joining at a narrow pitch. For example, as shown in the examples described below, joining between metal electrodes with a diameter of 5 μm can be formed at a pitch as narrow as 8 μm.

[0033] Second, because the SAM is a thin film, it is completely or almost completely removed from the metal electrode parts by the heat in the heating step, realizing good contact between the metal electrodes. This allows the solid-state diffusion of metal atoms between the metal electrodes to proceed smoothly without being hindered, resulting in a bonded body with high reliability in electrical connection between the metal electrodes.

[0034] Third, during the SAM formation stage, i.e., the stage in which the SAM material self-assembles to form a SAM on the metal electrode, the native oxide film formed on the surface of the metal electrode prior to SAM formation can be removed. In conventional hybrid bonding methods, prior to bonding, the bonding surfaces of the bonding targets are etched (e.g., with an acid-containing etching solution, as described below) to remove this native oxide film. In contrast, in the hybrid bonding method according to the present embodiment, an acidic surface treatment solution with a pH of 5.0 or less is used to form a SAM and remove the native oxide film, thereby eliminating the need for etching. That is, according to a preferred aspect of the present embodiment, the number of steps required for hybrid bonding can be reduced. Since the risk of particle contamination increases with the number of steps, reducing the number of steps is effective for obtaining a defect-free bonded structure. The hybrid bonding method according to the present embodiment may include an etching step (e.g., an acid etching step, as described below) to remove the native oxide film formed on the surface of the metal electrode by etching. However, from the perspective of reducing the number of steps and costs, it is preferable not to include the etching step.

[0035] Whether or not the native oxide film on the surface of the metal electrode portion has been removed by forming a SAM can be evaluated by performing a surface chemical structure analysis by X-ray photoelectron spectroscopy (XPS) on the joining object after the SAM formation. In the depth profile by XPS analysis, O corresponding to the oxide of the metal forming the metal electrode portion is detected. １ｓ Depending on the presence or absence of the peak and its intensity, it is possible to determine whether or not a native oxide film remains on the metal electrode portion and the amount of the native oxide film remaining.

[0036] In addition, by heating the joining object after the SAM formation under the same conditions as in the heating step and performing a surface chemical structure analysis by XPS on the joining object after heating, it is possible to evaluate whether or not the metal electrode portion is oxidized by heating and an oxide film is generated. The presence or absence of an oxide film generated due to heating and the amount of the oxide film generated can also be evaluated in the same manner as above. １ｓ It is judged by the presence or absence and intensity of the peak.

[0037] Fourth, by treating the surfaces of not only the metal electrode portions but also the dielectric portions of the joining targets with an acidic surface treatment solution containing a SAM material during the SAM formation stage, it is presumed that the surface of the dielectric portion is activated, thereby improving the mechanical connection reliability of the joined body. This is presumed based on the fact that, if the bonding of the dielectric portion is weak, peeling occurs at the joining surface of the joined body, separating the first joining target and the second joining target. However, in the examples described below, no such peeling was observed. In other words, this embodiment can also be expected to have an effect of improving the mechanical connection reliability of the joined body.

[0038] Based on the above, the main effects of the present disclosure can be summarized as follows. Conventional hybrid bonding methods require etching (e.g., etching with an acid-containing etchant, as described below) and plasma treatment of the bonding surfaces of the objects to be bonded prior to bonding. Etching is a process performed to remove natural oxide films that inevitably form on the bonding surfaces of the metal electrode portions. Plasma treatment is a process performed primarily to activate the bonding surfaces of the dielectric portions. These processes are essential for improving the strength of the electrical and mechanical bonds of the bonded body to a practical level. However, plasma treatment roughens the bonding surfaces of the metal electrode portions, creating gaps between the metal electrodes during bonding, which can lead to problems such as the inability to ensure reliable electrical connections between the bonded electrodes. Furthermore, plasma treatment can sometimes result in the formation of oxide films on the bonding surfaces of the metal electrodes. In contrast, according to the present embodiment, surface treatment using an acidic surface treatment solution containing a SAM material not only removes natural oxide films that inevitably form on the bonding surfaces of the metal electrode portions, but also protects the metal electrodes with the SAM, preventing oxidation of the metal electrodes. It is also believed that such surface treatment can activate the dielectric portion of the bonding surface. Therefore, the hybrid bonding method according to this embodiment can achieve a bond with high electrical connection reliability, preferably high electrical connection reliability and high mechanical connection reliability, without plasma treatment. As described below, the hybrid bonding method according to this embodiment may include a plasma treatment step. However, in terms of reducing the number of steps and costs, it is preferable not to perform plasma treatment prior to the heating step in which the bonding surfaces of at least two bonding targets are brought into contact with each other and heated. That is, in the hybrid bonding method according to this embodiment, it is preferable not to perform plasma treatment on the first dielectric portion of the first bonding surface before the first monomolecular film formation step, and not to perform plasma treatment on the second dielectric portion of the second bonding surface before the second monomolecular film formation step.

[0039] The thickness of the SAM (when two or more SAMs are stacked on the metal electrode portion, the total thickness of the two or more SAMs. In the present disclosure, the "SAM thickness" also includes the total thickness of the two or more stacked SAMs) varies depending on the type of SAM material, but is preferably 0.3 nm or more and 10 nm or less, more preferably 0.5 nm or more and 5 nm or less, even more preferably 1 nm or more and 4 nm or less, and even more preferably 1 nm or more and 3 nm or less.

[0040] By setting the SAM thickness to the above upper limit or less, the SAM material is more likely to melt and evaporate (preferably self-evaporate), or to evaporate (preferably self-evaporate) during the heating process. This allows the SAM to be easily removed from the metal electrode portion, making it less likely for the SAM to remain between the metal electrodes after bonding. Even if the SAM does not completely melt and evaporate during the heating process and some remains, the SAM is a very thin film, so its effect on the electrical resistance of the bonded metal electrodes is minimal. Therefore, by setting the SAM thickness to the above upper limit or less, a bonded body with excellent electrical connection reliability between metal electrodes can be provided. By setting the SAM thickness to the above lower limit or more, the metal electrode portion can be sufficiently protected.

[0041] The thickness of the SAM can be measured by X-ray photoelectron spectroscopy (XPS), under the conditions described in the Examples below.

[0042] The first SAM material forming the first SAM and the second SAM material forming the second SAM are not particularly limited as long as they can self-assemble to form a monomolecular film on the metal electrode portion, but compounds that have a bonding ability with the metal material forming the metal electrode portion can be preferably used.

[0043] Preferred examples of compounds that have a bond with the metal material that forms the metal electrode portion include azole compounds that may have a substituent. As described above, the metal electrode portion is preferably a copper electrode portion formed of copper. Since the azole ring has excellent bonding properties with copper, among other metals, azole compounds that may have a substituent are particularly useful as materials for forming a SAM on the copper electrode portion. Furthermore, the azole ring has weak or no bonding properties with the dielectric. Therefore, when an azole compound that may have a substituent is used as a SAM material, a SAM is hardly formed on the dielectric portion, and a SAM is selectively formed on the metal electrode portion. In this respect, azole compounds that may have a substituent are also suitable as SAM materials.

[0044] The azole compound is a nitrogen-containing five-membered heterocyclic compound, and may be a monocyclic compound or a fused ring compound (preferably a benzotriazole compound) in which the nitrogen-containing five-membered heterocyclic ring is fused with another aromatic ring. Specific examples of the azole compound include imidazole, benzimidazole, pyrazole, 1,2,3-triazole, 1,2,4-triazole, 1,2,3-benzotriazole, tetrazole, oxazole, isoxazole, thiazole, isothiazole, 1,2,3-oxadiazole, 1,2,4-oxadiazole, 1,2,5-oxadiazole, 1,3,4-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, and 1,3,4-thiadiazole. Preferred are imidazole, benzimidazole, 1,2,3-triazole, 1,2,4-triazole, 1,2,3-benzotriazole, or tetrazole, and more preferred are 1,2,3-triazole or 1,2,3-benzotriazole.

[0045] When the azole compound has a substituent, the number of the substituents is not particularly limited as long as it does not inhibit bonding with the metal material that forms the metal electrode portion, but is preferably 1 or more and 3 or less, more preferably 1 or 2, and even more preferably 1. Furthermore, when the azole compound has a substituent, the position of the substituent is not particularly limited as long as it does not inhibit bonding with the metal material that forms the metal electrode portion.

[0046] The substituent that the azole compound may have is not particularly limited as long as it does not inhibit the bond with the metal material that forms the metal electrode part. １ ) ２ and *—Si(OR ２ ) ３ an alkyl group having 1 to 15 carbon atoms which may have one or more functional groups selected from the group consisting of groups represented by the following formula (hereinafter, may be referred to as "functional group group A"); and ３ ) ２ Preferred examples of the substituent that the azole compound may have are alkyl groups having 1 to 15 carbon atoms which may have one or more functional groups selected from functional group group A, and more preferably unsubstituted alkyl groups having 1 to 15 carbon atoms, in that they are expected to be able to form a stable SAM and to impart water repellency to the SAM. Note that the number of carbon atoms in the alkyl group having 1 to 15 carbon atoms does not include the number of carbon atoms of the functional group.

[0047] The number of carbon atoms in the alkyl group having 1 to 15 carbon atoms which may have one or more functional groups selected from functional group group A is preferably 1 to 10, more preferably 1 to 6, and even more preferably 2 to 4.

[0048] Specific examples of the alkyl group having 1 to 15 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, and an n-pentadecyl group. Among these, the alkyl group having 1 to 15 carbon atoms is preferably a linear alkyl group, and more preferably a methyl group, an ethyl group, an n-propyl group, or an n-butyl group.

[0049] When the alkyl group having 1 to 15 carbon atoms has one or more functional groups selected from functional group group A, the number of functional groups is not particularly limited, but is preferably 1 or 2, and more preferably 1. Furthermore, when the alkyl group having 1 to 15 carbon atoms has one or more functional groups selected from functional group group A, the position of the functional groups is not particularly limited.

[0050] *-N(R １ ) ２ R in the group represented by １ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a hydroxyalkyl group having 1 to 6 carbon atoms. １ may be the same or different, but are preferably the same.

[0051] R １ The number of carbon atoms in the alkyl group having 1 to 6 carbon atoms represented by the formula (I) is preferably 1 to 4, more preferably 1 or 2.

[0052] R １ Specific examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-pentyl group, and an n-hexyl group.

[0053] R １The hydroxyalkyl group having 1 to 6 carbon atoms, represented by the formula (I), is a group in which one or more hydrogen atoms bonded to carbon atoms of the above-mentioned alkyl group having 1 to 6 carbon atoms are substituted with hydroxy groups. The number of carbon atoms in the hydroxyalkyl group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 or 2.

[0054] Specific examples of the hydroxyalkyl group having 1 to 6 carbon atoms include a hydroxymethyl group, a 2-hydroxyethyl group, a 1-hydroxyethyl group, a 3-hydroxypropyl group, an α-hydroxyisopropyl group, a 4-hydroxybutyl group, a 5-hydroxypentyl group, and a 6-hydroxyhexyl group.

[0055] *-N(R １ ) ２ Specific preferred examples of the group represented by the formula include an amino group, a dimethylamino group, a diethylamino group, and a bis(2-hydroxyethyl)amino group.

[0056] *-Si(OR ２ ) ３ R in the group represented by ２ are each independently an alkyl group having 1 to 4 carbon atoms. ２ may be the same or different, but are preferably the same.

[0057] R ２ The number of carbon atoms in the alkyl group having 1 to 4 carbon atoms represented by the formula (I) is preferably 1 to 3, more preferably 1 or 2.

[0058] R ２ Specific examples of the alkyl group having 1 to 4 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group, and a methyl group or an ethyl group is preferred.

[0059] *-Si(OR ２ ) ３ Specific preferred examples of the group represented by the formula include a trimethoxysilyl group and a triethoxysilyl group.

[0060] Specific preferred examples of the alkyl group having 1 to 15 carbon atoms which may have one or more functional groups selected from functional group group A include a methyl group, an ethyl group, an n-propyl group, an N,N-bis(2-hydroxyethyl)aminoethyl group, and a 1,2-dicarboxyethyl group.

[0061] *-N(R ３ ) ２ R in the group represented by ３ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and preferably a hydrogen atom. ３ may be the same or different, but are preferably the same.

[0062] R ３ The number of carbon atoms in the alkyl group having 1 to 6 carbon atoms represented by the formula (I) is preferably 1 to 4, more preferably 1 or 2.

[0063] R ３ Specific examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an isobutyl group, an n-pentyl group, and an n-hexyl group, and a methyl group or an ethyl group is preferred.

[0064] *-N(R ３ ) ２ Preferred specific examples of the group represented by the formula include an amino group, a dimethylamino group, and a diethylamino group.

[0065] Taking all of the above into consideration, preferred specific examples of the azole compound which may have a substituent include imidazole, benzimidazole, 1,2,3-triazole, 1,2,4-triazole, 1,2,3-benzotriazole, tetrazole, 5,6-dimethylbenzotriazole, 1-[N,N-bis(2-hydroxyethyl)aminoethyl]benzotriazole, 1-(1',2'-dicarboxyethyl)benzotriazole, tolyltriazole, 5-aminotetrazole, and tetrazole-5-acetic acid.

[0066] The azole compound which may have a substituent can be produced by combining any organic synthesis method (for example, known organic synthesis methods or synthesis methods similar thereto).

[0067] The first SAM material and the second SAM material may be the same material or different materials, but are preferably the same material.

[0068] The solvent for the surface treatment liquid is not particularly limited as long as it can dissolve or disperse the SAM material, and water, an organic solvent, or a mixed solvent of water and an organic solvent can be used.

[0069] Examples of organic solvents include alcohols such as methanol, ethanol, n-propanol, and isopropanol; esters such as methyl acetate and ethyl acetate; ethers such as diethyl ether, propylene glycol monomethyl ether, and tetrahydrofuran; and ketones such as acetone and methyl ethyl ketone.

[0070] The content of the SAM material in the surface treatment solution is not particularly limited as long as it is capable of forming a SAM on the metal electrode portion, but in terms of more efficient self-assembly, it is preferably 0.1 mass % or more and 5 mass % or less, and more preferably 0.5 mass % or more and 3 mass % or less.

[0071] The pH of the surface treatment solution is 5.0 or less, preferably 0.1 to 5.0, more preferably 0.5 to 4.5, even more preferably 1.0 to 4.0, still more preferably 1.5 to 3.5, and particularly preferably 2.0 to 3.0. By adjusting the pH of the surface treatment solution within the above range, the native oxide film formed on the surface of the metal electrode portion can be sufficiently removed.

[0072] The surface treatment solution may contain one or more components other than the SAM material and the solvent, such as a pH buffer, a complexing agent, and a surfactant, as long as the effects of the present disclosure are not impaired.

[0073] The method for contacting the surface treatment solution with the metal electrode portion is not particularly limited, and examples thereof include immersion methods; coating methods such as air knife coating, curtain coating, wire bar coating, gravure coating, spin coating, and slit scanning; and inkjet printing. Among these, the immersion method is preferred as the method for contacting the surface treatment solution with the metal electrode portion in both the first monomolecular film formation step and the second monomolecular film formation step, because it allows for easy and convenient formation of a SAM and provides high utilization efficiency of the SAM material. While the SAM may be formed by different methods in the first monomolecular film formation step and the second monomolecular film formation step, it is preferable to form the SAM by immersion in at least one of the first monomolecular film formation step and the second monomolecular film formation step, and it is more preferable to form the SAM by immersion in both the first monomolecular film formation step and the second monomolecular film formation step.

[0074] The contact temperature between the surface treatment solution and the metal electrode part varies depending on the contact method, but in terms of facilitating the formation of a SAM, it is preferably 10° C. or higher and 50° C. or lower, more preferably 15° C. or higher and 40° C. or lower, and even more preferably 20° C. or higher and 30° C. or lower. In this manner, in this embodiment, the surface treatment solution can be suitably brought into contact with the metal electrode part under room temperature conditions, and therefore, forming a SAM by the immersion method is excellent in workability and can also contribute to reducing production costs.

[0075] In the present disclosure, "room temperature" refers to a temperature condition in which no external heating or cooling is applied, specifically, a temperature condition of 20 to 30°C.

[0076] The contact time between the surface treatment solution and the metal electrode part is not particularly limited, but is preferably 5 to 60 seconds, more preferably 10 to 40 seconds, and even more preferably 10 to 35 seconds.

[0077] After contacting the surface treatment solution with the metal electrode, a SAM can be formed on the metal electrode by drying the solvent in the surface treatment solution or by washing the metal electrode that has been in contact with the surface treatment solution and then drying it. For washing the metal electrode, it is preferable to use pure water or ultrapure water such as purified water, distilled water, ion-exchanged water, RO water, and Elixir water. The drying method is not particularly limited, and any drying method such as natural drying, reduced-pressure drying, hot air drying, or drying by clean air blowing can be used.

[0078] 3. First Plasma Treatment Step and Second Plasma Treatment Step In this embodiment, in order to increase the mechanical bond strength between the first dielectric portion and the second dielectric portion and to achieve sufficient bond strength at a lower heating temperature, it is preferable to surface activate one or both of the first dielectric portion and the second dielectric portion by plasma treatment, and it is more preferable to surface activate both of them by plasma treatment. In other words, the hybrid bonding method according to this embodiment preferably includes one or both of a first plasma treatment step of plasma treating the first dielectric portion on the first bonding surface and a second plasma treatment step of plasma treating the second dielectric portion on the second bonding surface, and it is more preferable to include both of these steps.

[0079] As described above, when surface activation is performed by plasma treatment, the metal electrode portion is also exposed to the plasma, which may roughen the surface of the metal electrode portion or oxidize the metal electrode portion to form an oxide film, resulting in a loss of conductivity between the joined metal electrodes and a risk of insufficient electrical connection reliability between the metal electrodes. Therefore, it is preferable to perform the first plasma treatment step and the second plasma treatment step after the first monomolecular film formation step and the second monomolecular film formation step, respectively. This is because, if the metal electrode portion is protected by a SAM, even when irradiated with plasma, the surface of the metal electrode portion will not be roughened or an oxide film will not be formed on the metal electrode portion, and only the dielectric portion can be plasma-treated to activate the surface of the dielectric portion.

[0080] The method of plasma treatment carried out in the first plasma treatment step and the second plasma treatment step is not particularly limited, and any plasma treatment method used as a surface activation method for a dielectric layer can be appropriately adopted.

[0081] 4. Heating Step The heating step is a step of overlapping the first bonding surface of the first bonding object and the second bonding surface of the second bonding object and heating them after the first monolayer forming step and the second monolayer forming step. When overlapping the first bonding object and the second bonding object, they are aligned so that the first metal electrode portion and the second metal electrode portion face each other, and also so that the first dielectric portion and the second dielectric portion face each other.

[0082] In this embodiment, since the metal electrode portion is protected by the SAM, alignment and heating do not need to be performed in a vacuum, and therefore the hybrid joining method according to this embodiment is a joining method with excellent workability, in which highly accurate alignment can be performed in an air atmosphere.

[0083] The heating temperature in the heating step is not particularly limited, but is preferably 200°C or higher and 450°C or lower, more preferably 250°C or higher and 420°C or lower, and even more preferably 300°C or higher and 400°C or lower.

[0084] By setting the heating temperature to the above lower limit or higher, the SAM is easily removed, and the bonding between the first metal electrode portion and the second metal electrode portion and the bonding between the first dielectric portion and the second dielectric portion progresses, thereby improving the reliability of the electrical connection between the metal electrodes and the mechanical bonding strength between the dielectric portions. Furthermore, by setting the heating temperature to the above upper limit or lower, the reliability of the electrical connection between the metal electrodes and the mechanical bonding strength between the dielectric portions can be improved while reducing thermal damage.

[0085] The heating time in the heating step is not particularly limited, but is preferably 5 minutes to 5 hours, more preferably 10 minutes to 4 hours, even more preferably 30 minutes to 3 hours, and even more preferably 1 hour to 2 hours.

[0086] The heating step may be performed in an air atmosphere or in an inert gas atmosphere such as argon or nitrogen, but is preferably performed in an inert gas atmosphere. The heating step may be performed under normal pressure conditions or in a reduced pressure atmosphere, but is preferably performed in a reduced pressure atmosphere in that the SAM can be easily removed.

[0087] 5. Other Steps The hybrid bonding method according to this embodiment may include other steps in addition to the first monolayer forming step, the second monolayer forming step, the first plasma treatment step, the second plasma treatment step, and the heating step. Examples of other steps include, but are not limited to, an acid etching step.

[0088] The acid etching process is a process of removing a native oxide film from the metal electrode portion by etching using an etching solution containing an acid such as sulfuric acid and citric acid. Acid-containing etching solutions are known as selective etching solutions for metal oxides, particularly copper oxide, and are capable of selectively removing a native oxide film by contact with the acid-containing etching solution. The acid etching process may be performed on either the first metal electrode portion or the second metal electrode portion, or on both. Note that the acidic surface treatment solution used in the monolayer formation process in this embodiment also acts to remove a native oxide film from the metal electrode portion, but surface treatment with this surface treatment solution is not considered to be acid etching.

[0089] Natural oxidation of the metal electrode portion begins immediately after manufacture, forming a natural oxide film on the surface. When the acid etching process is performed, the natural oxide film is removed, exposing the metal material of the metal electrode portion on the bonding surface. In this embodiment, as described above, the natural oxide film is removed when forming the SAM, so the acid etching process is not essential. However, by removing the natural oxide film in advance by the acid etching process, the SAM can be formed more efficiently on the metal electrode portion.

[0090] 6. Joined Body The joined body obtained by the hybrid joining method according to this embodiment is obtained by joining the first metal electrode portion and the second metal electrode portion of the first joining object and the second joining object, and by joining the first dielectric portion and the second dielectric portion of the first joining object and the second joining object.

[0091] An example of a cross-sectional view of this bonded body taken in a direction perpendicular to the bonded surfaces is shown in Fig. 2. In Fig. 2, the bonded body 300 is formed by bonding a first bonding object 100 and a second bonding object 200 together, and has a structure in which the first metal electrode portion and the second metal electrode portion are bonded together, thereby integrating the first metal electrode 105 and the second metal electrode 205. This structure electrically connects the first metal electrode 105 and the second metal electrode 205. The bonded body 300 also has a structure in which the first dielectric layer 103 and the second dielectric layer 203 are integrated together, thereby integrating the first dielectric portion and the second dielectric portion.

[0092] The bonded structure 300 may have other components not shown in Fig. 2. Examples of the other components include various circuits and the above-mentioned barrier metal layer. Although the number of electrodes shown is one, it goes without saying that the number can be two or more.

[0093] [Application of Hybrid Bonding Method] The hybrid bonding method according to this embodiment is useful as a three-dimensional integration technique, and is therefore expected to be applied to the manufacture of integrated circuits and semiconductor devices.

[0094] Hereinafter, the embodiments of the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to these examples in any way.

[0095] [Preparation and Evaluation of Self-Assembled Monolayers] (Comparative Experimental Example 1) A copper layer having a thickness of 200 nm was formed on a silicon wafer by sputtering to obtain a silicon wafer having a copper layer as a simulated copper electrode portion. This wafer was used as a surface-untreated sample.

[0096] Experimental Example 1 The surface-untreated sample obtained in Comparative Experimental Example 1 was immersed in a surface treatment solution A containing 1,2,3-benzotriazole (1,2,3-benzotriazole concentration: 0.5% by mass, solvent: pure water, pH 2.0, SQ-1) at 25°C for 30 seconds, then washed by immersion in pure water at room temperature for 10 seconds, and dried with hot air to obtain a surface-treated sample A.

[0097] (Experimental Example 2) A surface-treated sample B was obtained in the same manner as in Experimental Example 1, except that the surface treatment liquid was changed to a surface treatment liquid B containing 5,6-dimethylbenzotriazole (5,6-dimethylbenzotriazole concentration: 0.5 mass %, solvent: pure water, pH 5.0).

[0098] Experimental Example 3 A surface-treated sample C was obtained in the same manner as in Experimental Example 1, except that the cleaning with pure water, the etching treatment, and the cleaning with pure water were not carried out before the surface treatment with the surface treatment solution.

[0099] Experimental Example 4 A surface-treated sample D was obtained in the same manner as in Experimental Example 2, except that the cleaning with pure water, the etching treatment, and the cleaning with pure water were not carried out before the surface treatment with the surface treatment solution.

[0100] [Elemental Analysis by XPS] The surface-treated samples obtained in Experimental Examples 1 to 4 and the surface-untreated sample obtained in Comparative Experimental Example 1 were each subjected to surface elemental analysis by XPS under the following measurement conditions. Furthermore, the surface-treated samples obtained in Experimental Examples 1 to 4 and the surface-untreated sample obtained in Comparative Experimental Example 1 were each heated at 85°C and 85% RH for 4 hours, and then subjected to surface elemental analysis by XPS under the following measurement conditions. The results of the elemental analysis and the thickness of the self-assembled monolayer calculated from the elemental analysis results are shown in Table 1.

[0101] (XPS measurement conditions) Apparatus: "Theta Probe simultaneous angle-resolved X-ray photoelectron spectroscopy system" manufactured by Thermo Fisher Scientific Co., Ltd. X-ray beam diameter: 400 × 200 μmφ Analysis area: 200 μmφ Photoelectron extraction angle: 50°±20° Capture area: O １ｓ (543-523eV) ・Cu １ｓ (305-275eV)

[0102] From Table 1, it was confirmed that a self-assembled monolayer was formed on the copper layer regardless of whether or not an acid etching step was performed prior to the surface treatment with the surface treatment solution.

[0103]

[0104] [Surface Chemical Structure Analysis by XPS] The surface-treated sample A obtained in Experimental Example 1 and the surface-untreated sample obtained in Comparative Experimental Example 1 were each subjected to an oxidation test (85°C, 85% RH, 1 hour), and then subjected to surface chemical structure analysis by XPS under the following measurement conditions. The results are shown in Figure 3.

[0105] (XPS measurement conditions) Apparatus: "Theta Probe simultaneous angle-resolved X-ray photoelectron spectroscopy system" manufactured by Thermo Fisher Scientific Co., Ltd. X-ray beam diameter: 400 × 200 μmφ Analysis area: 200 μmφ Photoelectron extraction angle: 50°±20° Capture area: O １ｓ (543-523eV) ・Cu １ｓ (305-275eV)

[0106] 3, in the surface-untreated sample of Comparative Experimental Example 1, in which a self-assembled monolayer was not formed on the copper layer, oxide signals were observed both before and after the oxidation test. On the other hand, in the surface-treated sample A of Experimental Example 1, in which a self-assembled monolayer was formed on the copper layer, oxide signals were not observed both before and after the oxidation test. These findings demonstrate that surface treatment using an acidic surface treatment solution containing a self-assembled monolayer material removes the native oxide film on the copper layer surface. Furthermore, it is clear that the self-assembled monolayer has the effect of protecting the copper electrode portion and preventing oxidation of the copper electrode portion.

[0107] [Atomic Force Microscope (AFM) Observation] AFM images were taken of the surface-treated sample A obtained in Experimental Example 1 and the surface-untreated sample obtained in Comparative Experimental Example 1. The AFM measurement conditions were as follows: The AFM topography image of the surface-treated sample A is shown in Figure 4, and the AFM topography image of the surface-untreated sample is shown in Figure 5.

[0108] (AFM measurement conditions) Apparatus: "Dimension Icon-PT" manufactured by Bruker Cantilever: Sb-doped Si (0.01 to 0.025 Ωcm, length 115 μm, width 30 μm, thickness 3.5 μm, spring constant 20 Nm －１ , resonance frequency 333 kHz) Scan area: 500 × 500 nm to 1 × 1 μm ２ (0.5Hz / Line)

[0109] 4 and 5, the surface-treated sample (FIG. 4) has a larger surface roughness than the untreated sample (FIG. 5). This result indicates that the copper layer was covered with a self-assembled monolayer by contacting the simulated copper electrode with an acidic surface treatment solution containing a self-assembled monolayer material.

[0110] Comparative Example 1 A silicon oxide (SiO ) film having a thickness of 100 nm was formed on a silicon wafer by thermal oxidation. ２ A silicon dioxide layer was then formed on the silicon dioxide layer by reactive ion etching. A 20 nm thick titanium layer and a 400 nm thick copper layer were then sequentially formed on the silicon dioxide layer by sputtering. A 5,000 nm thick copper layer was then formed on the copper layer by electrolytic deposition, resulting in a laminate. The copper layer was then chemically mechanically polished to a depth of 5,000 nm from the surface to planarize the surface of the laminate. The planarized laminate was diced into 7 mm x 7 mm pieces and subjected to two-fluid cleaning to obtain surface-untreated chips. As shown in FIG. 1, the surface-untreated chips had a silicon layer, a silicon dioxide layer formed on the silicon layer, and copper electrodes embedded in the silicon dioxide layer. The surface-untreated chips also had a bonding surface having a dielectric portion formed of silicon dioxide and a copper electrode portion.

[0111] Next, two untreated chips were bonded together as follows: The bonding surfaces of one untreated chip and the other untreated chip were overlapped. The copper electrodes on the bonding surfaces of one untreated chip and the copper electrodes on the bonding surfaces of the other untreated chip were aligned so as to face each other. The two overlapped untreated chips were heated at 400°C for two hours to obtain a bonded assembly.

[0112] [Example 1] The surface-untreated chip obtained in Comparative Example 1 was immersed in pure water at room temperature for 10 seconds to wash, and then etched by immersing in a 10% aqueous sulfuric acid solution at room temperature for 10 seconds. The etched chip was then immersed in pure water at room temperature for 10 seconds to wash. The washed chip was then immersed in surface treatment solution A at 25°C for 30 seconds, and then immersed in pure water at room temperature for 10 seconds to wash, and then dried with hot air to obtain a surface-treated chip in which a self-assembled monolayer was formed on the copper electrode portion on the bonding surface of the chip.

[0113] Next, the two surface-treated chips were bonded together as follows: The bonding surfaces of one surface-treated chip and the other surface-treated chip were overlapped. At this time, the copper electrode portion on the bonding surface of one surface-treated chip was aligned so as to face the copper electrode portion on the bonding surface of the other surface-treated chip. The two overlapping surface-treated chips were heated at 400°C for 2 hours to obtain a bonded assembly.

[0114] [Evaluation of current-voltage (IV) characteristics] The IV characteristics were measured for each of the bonded structure obtained in Example 1 and the bonded structure obtained in Comparative Example 1. Specifically, a Kelvin-patterned daisy chain was applied with a short needle to four measurement pads using a wafer prober, and the voltage was linearly increased to measure the resulting current value. The results are shown in FIG. 6. Furthermore, the bonded structure obtained in Example 1 and the bonded structure obtained in Comparative Example 1 were each aged by being left to stand in the air at room temperature for 456 hours, and then the IV characteristics of the bonded structures were measured in the same manner as above. The results are shown in FIG. 7.

[0115] As can be seen from Fig. 6, before aging, there was no significant difference in the electrical resistance value of the assembly obtained in Example 1 and that of the assembly obtained in Comparative Example 1. On the other hand, as can be seen from Fig. 7, after aging, there was a significant difference in the electrical resistance value of the assembly obtained in Example 1 and that of the assembly obtained in Comparative Example 1. More specifically, in Comparative Example 1, in which a self-assembled monolayer was not formed on the copper electrode portion, the electrical resistance of the copper electrode increased after aging, whereas in Example 1, in which a self-assembled monolayer was formed on the copper electrode portion, good electrical connection reliability was observed even after aging.

[0116] [Scanning Electron Microscope (SEM) Observation] A cross-sectional SEM image of the bonded body obtained in Example 1 was taken under the following measurement conditions. The results are shown in Fig. 8. The diameter of the copper electrodes measured in the SEM image was 5 µm, and the inter-electrode pitch was 8 µm.

[0117] (SEM measurement conditions) Apparatus: "SU-70 type" manufactured by Hitachi High-Tech Corporation Acceleration voltage: 0.5 to 30 kV Emission current: 50 μA Measurement magnification: 100 to 8,000,000 times Detector: PD-BSE Electron beam incident angle: 90° w.r.t. sample surface Scan speed: 10 to 30 frames / sec

[0118] SEM observations showed that by forming a self-assembled monolayer on the copper electrode using an acidic surface treatment solution containing a self-assembled monolayer material, it was possible to achieve bonding between metal electrodes with a diameter of 5 μm at a narrow pitch of 8 μm.

[0119] According to an embodiment of the present disclosure, a hybrid joining method can not only provide a joined body with high electrical connection reliability but also reduce the number of steps required for hybrid joining, which may contribute to the development of three-dimensional integration technology while reducing the energy required for joining compared to conventional methods. Therefore, an embodiment of the present disclosure may contribute to the achievement of Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and Goal 12 "Ensure sustainable consumption and production patterns" of the United Nations-led Sustainable Development Goals (SDGs).

[0120] REFERENCE SIGNS LIST 100 First bonding object 101 First semiconductor substrate 103 First dielectric layer 105 First metal electrode 110 First bonding surface 113 First dielectric portion 115 First metal electrode portion 200 Second bonding object 201 Second semiconductor substrate 203 Second dielectric layer 205 Second metal electrode 300 Bonded body

Claims

1. A method for joining a first joining object having a first joining surface having a first dielectric portion and a first metal electrode portion, and a second joining object having a second joining surface having a second dielectric portion and a second metal electrode portion, comprising: a first monolayer formation step of forming a first self-assembled monolayer on the first metal electrode portion of the first joining surface by contacting the first metal electrode portion with a first surface treatment liquid; a second monolayer formation step of forming a second self-assembled monolayer on the second metal electrode portion of the second joining surface by contacting a second surface treatment liquid with the second metal electrode portion; and a heating step of overlapping and heating the first joining surface of the first joining object and the second joining surface of the second joining object, wherein the first surface treatment liquid contains a first self-assembled monolayer material and has a pH of 5.0 or less; and the second surface treatment liquid contains a second self-assembled monolayer material and has a pH of 5.0 or less.

2. The hybrid bonding method according to claim 1, wherein one or both of the first self-assembled monolayer material and the second self-assembled monolayer material is an azole compound which may have a substituent.

3. The substituent is a carboxy group, *-N(R １ ) ２ and *—Si(OR ２ ) ３ an alkyl group having 1 to 15 carbon atoms which may have one or more functional groups selected from the group consisting of groups represented by the formula ３ ) ２ R is a group represented by １ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a hydroxyalkyl group having 1 to 6 carbon atoms; R ２ are each independently an alkyl group having 1 to 4 carbon atoms, ３ The hybrid bonding method according to claim 2 , wherein each of the groups independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

4. The hybrid bonding method according to claim 1, wherein plasma treatment of the first dielectric portion is not performed before the first monolayer forming step, and plasma treatment of the second dielectric portion is not performed before the second monolayer forming step.

5. The hybrid bonding method according to claim 1, wherein the thickness of one or both of the first self-assembled monolayer and the second self-assembled monolayer is 0.3 nm or more and 10 nm or less.

6. The hybrid bonding method according to claim 1, comprising one or both of a first plasma treatment step of plasma treating the first dielectric portion after the first monolayer formation step, and a second plasma treatment step of plasma treating the second dielectric portion after the second monolayer formation step.

7. The hybrid joining method according to claim 1, wherein the first metal electrode portion and the second metal electrode portion are formed of copper.

8. The hybrid joining method according to claim 1, wherein the first dielectric portion and the second dielectric portion are formed of silicon oxide.

9. The hybrid joining method according to claim 1, wherein the first joining object and the second joining object are each a wafer or a chip.

10. A method for manufacturing an integrated circuit, comprising the hybrid bonding method according to any one of claims 1 to 9.

11. A method for manufacturing a semiconductor device, comprising the hybrid bonding method according to any one of claims 1 to 9.

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