Method of direct bonding between two substrates

Abstract

The invention relates to a method of direct bonding between two substrates, the method comprising the steps of: (a) providing a first substrate and a second substrate, the first substrate and the second substrate comprising respectively a first bonding surface made of hydrophilic silicon oxide and a second bonding surface made of hydrophilic silicon oxide; (b) depositing a specific compound on the first bonding surface made of hydrophilic silicon oxide, the specific compound being an organic compound consisting of a basic functional group and substituents of the basic functional group, each substituent being a hydrophobic group, (c) contacting the first bonding surface made of hydrophilic silicon oxide having deposited the specific compound with the second bonding surface made of hydrophilic silicon oxide, to adhere the first substrate to the second substrate.

Description

Technical Field

[0001] This invention relates to a method for direct bonding between two substrates. Background Technology

[0002] Direct bonding is a technique widely used in microelectronics to assemble substrates and form multilayer structures. This technique involves bringing two surfaces to be bonded into direct contact, where they will spontaneously adhere to each other without the addition of any additional materials, particularly without the use of polymeric adhesives. Some water monolayer may be adsorbed on the surfaces to be bonded, especially if they are hydrophilic, but the surfaces must be macroscopically dry.

[0003] Spontaneous adhesion between two surfaces to be bonded occurs under the influence of various attractive forces between materials (e.g., van der Waals forces, capillary forces, and / or hydrogen bonds involving water molecules adsorbed on the surfaces to be bonded). Covalent bonds can also form between the two surfaces to be bonded.

[0004] For example, when the surfaces to be bonded are hydrophilic silicon or silicon oxide surfaces, the adhesion between the two surfaces mainly arises from the condensation reaction between the silanols on the first and second surfaces. More specifically, each condensation reaction generates a siloxane bond between the two surfaces to be bonded and releases water molecules according to the following reaction (I): Si1-OH + Si2-OH -> Si1-O-Si2+ H2O (I) The aforementioned attraction only works over short distances, and the formation of covalent bonds requires the reactants to be close enough for their molecular orbitals to overlap. Therefore, direct bonding requires the surfaces to be clean and flat, with very low roughness, for example, less than 0.5 nm. Typically, the aforementioned reaction (I) can only occur at the contact point between the two surfaces to be bonded. Furthermore, this reaction (I) is very slow and remains in equilibrium (incomplete) at room temperature.

[0005] The quality of direct bonding can be assessed by a quantity called "bonding energy," which corresponds to the energy required to separate the two surfaces once bonded. Due to the aforementioned difficulties, the bonding energy between two surfaces bonded by direct bonding at room temperature is insufficient to guarantee the mechanical strength of the resulting multilayer structure in subsequent applications, such as if the multilayer structure is used in methods that induce high mechanical stresses at the bonding interface. In fact, when two surfaces adhere under the aforementioned attractive forces, the bonding energy between two surfaces directly bonded at room temperature rarely reaches 200 mJ / m. 2 At ambient temperature, the condensation reaction (I) of silanols does not produce an energy exceeding 0.5 J / m³ even after several days.2 .

[0006] One solution to improve bonding energy is to heat the bonding interface after the two surfaces to be bonded have come into contact. For example, after bringing two hydrophilic silicon or silicon oxide surfaces to be bonded into contact, the bonding interface can be heat-treated at 200°C for 2 hours. This promotes and significantly accelerates the condensation reaction of silanols.

[0007] However, such high temperatures can induce the formation of gas and bubbles at the bonding interface, leading to bonding defects and significant thermal stress, especially when the two substrates to be bonded have very different coefficients of thermal expansion. In fact, in the latter case, the different behaviors of the two substrates under the influence of temperature changes can cause the bonding interface to detach before it has time to strengthen.

[0008] Document FR 3 102 771 B1 advantageously proposes obtaining a high bonding energy between two hydrophilic bonding surfaces at low temperatures by depositing a specific molecule on at least one hydrophilic bonding surface before bringing two substrates to be bonded into contact. The at least one hydrophilic bonding surface on which the specific molecule is deposited is located at the bonding interface. Document FR 3 102 771 B1 specifies that the specific molecule is an organic molecule containing both a hydrophilic group and a basic group, wherein the hydrophilic group enables the specific molecule to be chemisorbed onto the hydrophilic surface to be bonded, and the basic group enables the increase of the pH value of the water monolayer adsorbed on the surface, and the hydrophilic group and the basic functional group are separated by at least one carbon atom. The bonding method described in document FR 3102 771 B1 allows for a bonding energy greater than 1 J / m at bonding strengthening annealing temperatures below 100°C. 2 The bonding energy.

[0009] However, the organic molecules described in FR 3 102 771 B1 are highly specific and may be difficult to obtain or expensive. Furthermore, these organic molecules are inevitably trapped at the bonding interfaces in the resulting components, and may subsequently cause electrical and mechanical failures in the components. Finally, they constitute a significant source of cleanroom contamination, as they may contaminate other steps in the process or other methods performed in the same cleanroom. Summary of the Invention

[0010] One object of the present invention is to design a low-temperature direct bonding method between two substrates, enabling the achievement of bonding energies compatible with the use of components obtained by bonding two substrates for conventional microelectronic applications (e.g., fabrication of silicon-on-insulator substrates or components for hybrid circuits), typically achieving bonding energies greater than 1 J / m. 2The energy level. The low-temperature direct bonding method must also be easy to implement, inexpensive, and capable of producing electronic components with fewer defects compared to components manufactured using existing techniques.

[0011] Therefore, the present invention proposes a method for directly bonding two substrates, the method comprising the following steps: (a) Providing a first substrate and a second substrate, the first substrate and the second substrate respectively comprising a first bonding surface made of hydrophilic silicon oxide and a second bonding surface made of hydrophilic silicon oxide. (b) Depositing a specific compound on the first bonding surface made of hydrophilic silica, the specific compound being an organic compound consisting of a basic functional group and substituents of the basic functional group, each substituent being a hydrophobic group, the specific compound containing at least one carbon atom, and the hydrophobic group being capable of referring to a single hydrogen atom. (c) Contacting the first bonding surface made of hydrophilic silicon oxide, on which the particular compound has been deposited, with the second bonding surface made of hydrophilic silicon oxide to cause the first substrate to adhere to the second substrate.

[0012] Therefore, the specific compound deposited on the first hydrophilic bonding surface is an organic compound containing only basic functional groups. In other words, the specific compound according to the invention does not contain any additional hydrophilic groups. In fact, the inventors have demonstrated that such hydrophilic groups are not necessary for the presence of the specific compound on at least one bonding surface to significantly increase the bonding energy, allowing direct bonding at low temperatures in the presence of the specific compound according to the invention to produce sufficient bonding energy for the aforementioned applications. Typically, the presence of the specific compound according to the invention at the bonding interface allows for a bonding energy greater than 1 J / m after only 1 hour of hardening annealing at 100°C. 2 The bonding energy.

[0013] Therefore, the present invention provides a wide selection of readily available organic compounds that can have very low molecular weights. For example, specific compounds according to the present invention can have the same basic functional groups as the specific molecules proposed in FR 3 102 771 B1, without additional hydrophilic groups and inserted carbons. Finally, specific compounds according to the present invention can have lower molecular weights, particularly lower carbon molecular weights. Therefore, due to this lower carbon molecular weight, the compounds according to the present invention represent smaller sources of pollution and will thus induce fewer electrical and mechanical failures such as those mentioned above.

[0014] The inventors hypothesize that the basic functional groups are sufficient to allow the specific compound to chemisorb onto the hydrophilic bonding surface. The inventors attribute the high bonding energy achieved under low thermal budget to the basic catalytic effect of the specific compound, which enhances the kinetics of the condensation reaction responsible for adhesion between the first and second substrates and shifts its equilibrium. More specifically, according to Figure 1 In the first mechanism shown, the basic functional group reacts with water adsorbed on the surface to be bonded, thereby generating hydroxide ions (OH-). - The hydroxide ions then initiate a nucleophilic attack on the silicon atoms of the surface silanol groups, thereby generating five-coordinate silicon atoms that are highly reactive to the oxygen atoms of the silanol groups on the second hydrophilic silica bonded surface. Therefore, the condensation reaction is greatly promoted.

[0015] The inventors considered a second mechanism that relies on the nucleophilic properties of the basic groups in a specific compound: the specific compound can directly induce nucleophilic addition or substitution on silicon atoms at the first hydrophilic silica bonding surface, thereby generating highly reactive reaction intermediates, which will promote condensation reactions on these reaction intermediates. This is more accurately referred to as the nucleophilic catalytic effect of the specific compound.

[0016] These two mechanisms may work together, with one potentially dominating over the other depending on the properties of the particular compound (and its basicity relative to its nucleophilicity), as well as the properties of the first and second hydrophilic bonding surfaces and other experimental parameters.

[0017] This treatment using the specific compound according to the invention is also easier to implement than treatments using ammonia or ammonium hydroxide because it allows for easier control of the amount of catalytic material deposited on the surface and the pH of the surface. In fact, ammonia and ammonium hydroxide are highly volatile compounds, thus requiring control of ammonia vapor in equilibrium with the material physically adsorbed on the surface.

[0018] Other optional features according to the invention may be used individually or in combination (where technically feasible): - The specific compound is not N-methylhydroxylamine; - The method further includes depositing the specific compound on a second hydrophilic silica bonding surface, wherein the adhesion of the first substrate to the second substrate is achieved by contacting the first hydrophilic silica bonding surface with the second hydrophilic silica bonding surface on which the specific compound has been deposited. - Before the first hydrophilic bonded surface, on which the specific compound has been deposited, comes into contact with the second hydrophilic bonded surface, the surface concentration of the specific compound on the first hydrophilic bonded surface is 10. 11 molecule / cm2 Up to 10 15 molecule / cm 2 between; - The specific compound contains 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms, and / or the molecular weight of the specific compound is less than 200 g / mol, preferably less than 100 g / mol; - The specific compound is a primary, secondary or tertiary, cyclic or acyclic, saturated or unsaturated aliphatic amine that does not contain a double bond at the terminal position, preferably selected from methylamine CH3NH2, dimethylamine (CH3)2NH, trimethylamine (CH3)3N and piperidine (CH2)5NH; - The specific compound is an organic ion, preferably an aliphatic carboxylate ion, more preferably selected from formate ions (HCOO). - and acetate ions CH3COO - The aliphatic carboxylate ion, wherein the counter ion of the organic ion is selected from ammonium NH4. + nitrite NO + and nitrogen NO2 + ; - The deposition of the specific compound on the first hydrophilic silica bonded surface includes depositing a liquid containing the specific compound on the first hydrophilic silica bonded surface; - Deposition of a liquid containing a specific compound on the first hydrophilic silica bonded surface includes: A certain volume of liquid containing the specific compound is deposited at the center of the first hydrophilic silica bonded surface. The volume of liquid containing the specific compound is spread by rotating the first hydrophilic silica bonded surface, while the first hydrophilic silica bonded surface remains rotated until the volume of liquid containing the specific compound is ejected and evaporated; - The method further includes the step of exposing the first hydrophilic silica bonded surface to plasma before depositing the volume of liquid containing the particular compound at the center of the first hydrophilic silica bonded surface; - The liquid containing the specific compound is obtained by dissolving the specific compound in a solvent, preferably water or a mixture of water and isopropanol (IPA), wherein the concentration of the specific compound in the liquid is 10. -7 mol / L to 10 -1 Between mol / L; - Deposition of the specific compound on the first hydrophilic silica bonded surface includes exposing the first hydrophilic silica bonded surface to a gas containing the specific compound; - The first substrate and / or the second substrate is a silicon substrate; - The first hydrophilic silica bonding surface and / or the second hydrophilic silica bonding surface are made of deposited oxide, chemical oxide, thermal oxide and / or native oxide; - The contact between the first bonding surface made of hydrophilic silica, on which the specific compound has been deposited, and the second hydrophilic silica bonding surface is carried out at a temperature between 0°C and 100°C. - The method further includes a hardening annealing step d) after step c) contacting the first bonding surface made of hydrophilic silica on which the particular compound has been deposited with the second bonding surface made of hydrophilic silica, the hardening annealing preferably being carried out at a temperature below 100°C, more preferably below 90°C, for a duration between 1 minute and 5 hours; - The first substrate is made of a first material, and the second substrate is made of a second material, wherein the difference in the coefficients of thermal expansion between the first material and the second material is greater than or equal to 10% in relative terms; - The first substrate is a multilayer structure comprising a first layer made of a first material and a second layer made of a second material, wherein the difference in the coefficients of thermal expansion between the first material and the second material is greater than or equal to 10% in relative terms; - The first substrate includes electronic component elements; - The first substrate includes a weakened region formed by implanting atomic or ionic material; This invention extends to a method for transferring a layer onto a supporting substrate, the method comprising the following steps: a) Providing a donor substrate including a first hydrophilic silicon oxide surface and a support substrate including a second hydrophilic silicon oxide surface, b) A weakening region is formed within the donor substrate to define the layer to be transferred between the first hydrophilic silicon oxide surface and the weakening region. c) Bonding the donor substrate and the support substrate, wherein the first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface are located at the bonding interface, and the bonding between the donor substrate and the support substrate is performed by the bonding method described above. d) Separate the donor substrate along the weakened region in order to transfer the layer to be transferred onto the support substrate. Attached Figure Description

[0019] Other features and advantages of the invention will become apparent from the following detailed description with reference to the accompanying drawings, in which: Figure 1The nucleophilic role of hydroxide ions in silanol condensation is shown, which leads to the formation of siloxane Si-O-Si bonds between the two surfaces to be bonded. - Figure 2 Two examples of nucleophilic or basic carbon molecules, namely glycine and ethanolamine, are shown, illustrating the beneficial effect on bonding energy. Detailed Implementation

[0020] The direct bonding method according to the present invention includes the first step of providing a first substrate comprising a first substrate comprising a first hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface.

[0021] A first substrate comprising a first hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface are provided.

[0022] The first substrate and / or the second substrate may be made of materials selected from: silicon (Si), germanium (Ge), indium phosphide (InP), gallium arsenide (AsGa), aluminum oxide (Al2O3), silicon oxide (SiO2), silicon nitride (Si3N4), silicon carbide (SiC), gallium nitride (GaN), copper, titanium, nickel, lithium niobate (LiNbO3, referred to as LNO by those skilled in the art), and lithium tantalate (LiTaO3, referred to as LTO by those skilled in the art).

[0023] Alternatively, the first substrate and / or the second substrate may be a multilayer structure comprising at least two layers. For example, the first substrate and the second substrate each comprise a first layer made of a first material and a second layer made of a second material, respectively. The first material and the second material are, for example, selected from the materials mentioned above. According to this embodiment, the step of providing a first substrate comprising a first hydrophilic bonding surface and a second substrate comprising a second hydrophilic bonding surface may include one or more sub-steps of assembling the layers to form the first substrate and / or the second substrate.

[0024] The direct bonding method according to the invention is particularly advantageous when the first substrate and / or the second substrate comprises layers made of materials having a large difference in their coefficients of thermal expansion. A large difference in the coefficients of thermal expansion is defined as a difference between the values ​​of said coefficients of thermal expansion of more than 10% in relative terms.

[0025] Furthermore, the first substrate and / or the second substrate may include one or more electronic component elements. For example, the first substrate and / or the second substrate may include a metallic portion such as copper wire and an insulating portion made of silicon oxide (hybrid bonding). Similarly, in this case, the step of providing a first substrate containing a first hydrophilic bonding surface and a second substrate containing a second hydrophilic bonding surface may include one or more sub-steps for forming the electronic component elements.

[0026] The direct bonding method according to the invention is particularly advantageous when the first substrate and / or the second substrate comprises such electronic components because, during heating, the different elements (metals, insulators, semiconductors) of such a system expand differently, which can generate significant stress within the device. These stresses can lead to defects such as delamination. The maximum thermal budget must not exceed the thermal budget generated at the device's operating temperature, which is typically below 200°C.

[0027] Finally, the first substrate and / or the second substrate may also include weakened regions, for example, formed by implanting atomic and / or ionic materials.

[0028] The direct bonding method according to the invention is particularly advantageous when the first substrate and / or the second substrate includes such weakened regions, because the weakened regions must subsequently be the weakest regions in the material; otherwise, fracture control would be difficult. Therefore, all other interfaces must have already been reinforced before fracture.

[0029] The first substrate and the second substrate may have the same properties, or they may be different. The direct bonding method according to the invention is particularly advantageous when the first substrate (or the layer of the first substrate at the bonding interface) and the second substrate (or the layer of the second substrate at the bonding interface) are made of materials with a large difference in their coefficients of thermal expansion.

[0030] First hydrophilic silicon oxide bonding surface and second hydrophilic silicon oxide bonding surface

[0031] As previously described, the first substrate and the second substrate each include a first hydrophilic silicon oxide bonding surface and a second hydrophilic silicon oxide bonding surface. A hydrophilic bonding surface is defined as a surface with a strong affinity for water, such that at least one water monolayer is naturally retained and adsorbed on the hydrophilic bonding surface. The contact angle of the hydrophilic surface is typically less than ten degrees.

[0032] For it to be hydrophilic, the silicon oxide surface must, in particular, be free of surface hydride silicon groups (Si-H), or the ratio of the number of hydride silicon groups (Si-H) to the number of surface silanol groups must be less than 20%. Preferably, the silicon oxide surface must be free of surface hydride silicon groups (Si-H), for example, by reacting with water in an alkaline medium without including surface hydride silicon groups (Si-H).

[0033] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface can be a native silicon oxide surface. In other words, if the first substrate and / or the second substrate contains a material on which a silicon oxide layer—referred to as a native silicon oxide layer—naturally forms on its surface, then the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface can be the surface of said native oxide layer. For example, this is the case with silicon and silicon carbide, which naturally form oxide layers with a thickness of approximately 1 nm. If the first substrate and / or the second substrate is silicon oxide or contains a silicon oxide layer, then the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface can be directly the surface of said silicon oxide.

[0034] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be a thermally heated silicon oxide surface. According to this embodiment, the step of providing a first substrate including a first hydrophilic silicon oxide bonding surface and a second substrate including a second hydrophilic silicon oxide bonding surface may include a sub-step of forming a first thermally heated silicon oxide layer on the first substrate and / or a sub-step of forming a second thermally heated silicon oxide layer on the second substrate, wherein the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface are respectively formed on the surface of the first thermally heated silicon oxide layer and the surface of the second thermally heated silicon oxide layer.

[0035] Thermal oxides are understood to be oxides formed by directly oxidizing a material by exposing it to oxygen (dry oxidation), water (wet oxidation), or optionally other oxidants (such as N2O) at high temperatures.

[0036] A thermally oxidized silicon layer can be formed on the surface of a silicon substrate or a silicon carbide substrate. For this purpose, the silicon substrate is heated to a temperature preferably between 800°C and 1200°C, and then the surface of the silicon substrate is exposed to an oxygen or water vapor atmosphere. The oxidation temperature determines the rate at which the thermally oxidized silicon layer grows from the surface of the silicon substrate exposed to the oxygen or water vapor atmosphere. In the case of wet thermal oxidation, the formation of the thermal oxide layer may involve burning hydrogen and oxygen in a torch and exposing the substrate to the water vapor produced by the combustion; the heat generated by the combustion reaction itself can also be used to raise the substrate to the temperature selected for thermal oxidation.

[0037] The thickness of the thermally oxidized silicon layer is, for example, between 1 nm and 1 µm.

[0038] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be a chemically oxidized silicon oxide surface. According to this embodiment, the step of providing a first substrate including a first hydrophilic silicon oxide bonding surface and a second substrate including a second hydrophilic silicon oxide bonding surface may include a sub-step of forming a first chemically oxidized silicon oxide layer on the first substrate and / or a sub-step of forming a second chemically oxidized silicon oxide layer on the second substrate, wherein the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface are respectively formed on the surface of the first chemically oxidized silicon oxide layer and the surface of the second chemically oxidized silicon oxide layer.

[0039] Chemical oxides are defined as oxides formed by oxidizing a material at low temperatures (preferably at room temperature) in the presence of water or certain oxidants (such as hydrogen peroxide H₂O₂ or ozone O₃). A chemical oxide layer can be formed on the surface of a silicon, silicon carbide, or silicon nitride substrate by exposing the surface of the substrate to water or the oxidant described above at low temperatures. The thickness of the chemical oxide layer on the silicon substrate surface is, for example, between 0.5 nm and 3 nm.

[0040] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be a deposited silicon oxide surface. According to this embodiment, the step of providing a first substrate including a first hydrophilic bonding surface and a second substrate including a second hydrophilic bonding surface may include a sub-step of depositing a first silicon oxide layer on the first substrate and / or a sub-step of depositing a second silicon oxide layer on the second substrate, wherein the surfaces of the first deposited oxide layer and the second deposited oxide layer respectively form the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface.

[0041] Deposited oxides are defined as oxides formed by chemically adding materials, such as in the form of vapor or plasma. Silicon oxide layers can be deposited on almost any type of material, including IV / IV, III / V, and II / VI semiconductors, as well as oxides such as LiTaO3 or LiNbO3. The thickness of deposited silicon oxide layers is, for example, between 1 nm and 10 µm.

[0042] To deposit a silicon oxide layer, the silicon precursor is typically silane (SiH4), while the oxygen precursor is, for example, N2O or O2. For instance, the substrate to which the silicon oxide layer is to be deposited is placed in a plasma chamber. Then, a carrier gas (e.g., hydrogen) containing the silicon and oxygen precursors (e.g., SiH4 and N2O) is introduced into the plasma chamber. Under the influence of the plasma, the precursors decompose and react, forming a silicon oxide layer on the substrate surface exposed to the plasma.

[0043] The above-described method for forming a silicon oxide layer is given as an example and does not limit the scope of the invention in any way. Those skilled in the art can adapt it to intended applications. For example, the method for depositing a silicon oxide layer may include applying a magnetic field or microwaves to accelerate deposition. Other carrier gases or precursors may also be used.

[0044] If the first substrate and / or the second substrate are made of silicon oxide or contain a silicon oxide layer and / or if the first substrate and / or the second substrate are made of a material in which a silicon oxide layer naturally forms on the surface or contain such a material, providing a first substrate containing a first hydrophilic silicon oxide bonding surface and a second substrate containing a second hydrophilic silicon oxide bonding surface may still include forming a first thermally or chemically deposited silicon oxide layer on the first substrate and / or forming a second thermally or chemically deposited silicon oxide layer on the second substrate, such that the surfaces of the first thermally or chemically deposited silicon oxide layer and the second thermally or chemically deposited silicon oxide layer form the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface.

[0045] The first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface can be of the same type or different types. For example, the first hydrophilic silicon oxide bonding surface can be a chemically oxidized silicon oxide surface, and the second hydrophilic silicon oxide bonding surface can be a native silicon oxide surface. In this case, the step of providing a first substrate containing a hydrophilic silicon oxide bonding surface and a second substrate containing a second hydrophilic silicon oxide bonding surface may include the sub-step of forming a chemically oxidized silicon oxide layer on the first substrate. For example, the first hydrophilic silicon oxide bonding surface can be a thermally oxidized silicon oxide surface, and the second hydrophilic silicon oxide bonding surface can be a deposited silicon oxide surface. In this case, the step of providing a first substrate containing a hydrophilic silicon oxide bonding surface and a second substrate containing a second hydrophilic silicon oxide bonding surface may include the sub-step of forming a thermally oxidized silicon oxide layer on the first substrate and the sub-step of forming a deposited silicon oxide layer on the second substrate.

[0046] These combinations are mentioned by way of example and do not limit the scope of the invention in any way. Any combination of the natural, chemical, thermal, and deposited silicon oxide surfaces of the first and second substrates is still covered by the invention.

[0047] Furthermore, depending on the nature of the first and second substrates to be obtained (monolithic substrates, or multilayer structures containing materials with very different coefficients of thermal expansion (possibly containing electronic component elements and / or weakening regions)) and the intended application of the component formed by bonding between the first and second substrates (e.g., fabrication of silicon-on-insulator or piezoelectric material-on-insulator), those skilled in the art can select the most suitable silicon oxide properties for the first or second substrate, as well as the order of the different sub-step sequences that allow for providing the first or second intended substrate.

[0048] Depositing a specific compound on at least the first hydrophilic silica bonded surface

[0049] The method further includes the step of depositing a specific compound on a first bonding surface made of hydrophilic silicon oxide, or depositing it on both the first and second hydrophilic silicon oxide bonding surfaces.

[0050] The specific compound is an organic compound.

[0051] For the purposes of this invention, an organic compound is defined as a compound consisting of several atoms connected by covalent bonds and containing at least one carbon atom, but not carbon monoxide (CO), carbon dioxide (CO2), carbonate (H2CO3), or carbonate ion (CO3). 2- Bicarbonate ions (HCO3-) - and cyanide ions CN - Except as otherwise provided. The term "organic compound" can refer to electrically neutral organic compounds, also known as organic molecules, or to charged organic compounds, also known as organic ions. However, carbon monoxide (CO), carbon dioxide (CO2), carbonate (H2CO3), and carbonate ions (CO32-) are exceptions. 2- Bicarbonate ions (HCO3-) - and cyanide ions CN - It is excluded from the group of organic compounds as defined in this invention.

[0052] When a particular compound is an organic molecule, it advantageously avoids the introduction of additional counterions, which would constitute a significant source of contamination. Therefore, this invention is particularly advantageous compared to treatment using hydroxide salt solutions, which allow hydroxide ions to be applied directly to the hydrophilic silica-bonded surface, but inevitably induce the simultaneous deposition of such counterions.

[0053] If the specific compound is a basic ion, the counter ion is not preferentially selected from alkali metals and alkaline earth metals. This is because alkali metals and alkaline earth metals are contaminants in microelectronics because they alter the properties of silicon and silicon dioxide. For example, the counter ion for organic ions is preferentially selected from ammonium (NH4). + nitrite NO + and nitrogen NO2 + .

[0054] More precisely, the specific compound is an organic compound consisting of a basic functional group and substituents of the basic functional group, each substituent being a hydrophobic group. If the basic functional group contains two substituents, these substituents may be the same or different. If the basic functional group contains three or more substituents, these substituents may be all the same, partially the same, or all different. Optionally, the basic functional group forms a first bond with one atom of a substituent and a second bond with a second atom of the same substituent, such that the specific compound is cyclic.

[0055] A functional group is defined as an atom or group of atoms that has similar chemical properties when present in different compounds. Specifically, the basic functional group according to the invention is a proton-capable functional group. In other words, a basic functional group contains one or more electron pairs capable of accepting one or more protons.

[0056] Substituents of basic functional groups are defined as atoms or groups of atoms covalently attached to the basic functional group via single, double, or triple bonds.

[0057] For example, the basic functional group is a monosubstituted amino group H2N-R1, a disubstituted amino group R1-N(H)-R2, or a trisubstituted amino group R1-N(R2)-R3, wherein R1, R2, and R3 each represent a substituent of the amino group. In other words, in this case, the specific compound is a primary amine, a secondary amine, or a tertiary amine, respectively.

[0058] For example, a basic functional group is an anionic group formed by the ionization of an acidic functional group. For instance, a basic functional group can be formed by the ionization of a sulfonic acid group (-SO3H), a carboxyl group (-COOH), or a hydroxyl group (-OH). In other words, the specific compound can be a sulfonate (R-SO3). - RCOO carboxylate - or alkoxide RO - , where R represents a substituent of a basic functional group.

[0059] For example, the basic functional group is hydroxylamine R1-N(OH)-R2, where R1 and R2 each represent a substituent of the hydroxylamine group. In other words, the specific compound is an organic molecule containing a single bond between a hydroxyl group and a nitrogen atom.

[0060] For example, the basic functional group is hydrazine R1-N(R2)-N(R3)-R4, where R1, R2, R3, and R4 each represent a substituent of the hydrazine group. In other words, the specific compound is an organic molecule containing a single bond between two nitrogen atoms.

[0061] On the other hand, the trimethoxysilane-Si-(O-Me)3 group, and more generally, all siloxane groups, are not basic functional groups in the sense of this invention.

[0062] As mentioned earlier, each substituent R, R1, R2, R3, and R4 of the basic functional group is a hydrophobic group. A hydrophobic group is defined as an atom or group of atoms that does not contain a hydrophilic functional group. In other words, a hydrophobic group does not contain a polar functional group or a functional group capable of forming hydrogen bonds with water. In particular, a hydrophobic group does not contain functional groups such as hydroxyl, ether, amide, ester, or oxo groups.

[0063] Preferably, the hydrophobic group is a hydrocarbon group containing only hydrogen and / or carbon elements.

[0064] For example, and provided that the particular compound also contains at least one carbon atom (which may be contained in a basic functional group or another substituent), the hydrophobic group may refer to a single hydrogen atom connected to the basic functional group by a single bond.

[0065] For example, the hydrophobic group may refer to an aliphatic chain, preferably a C1-C6 aliphatic chain, which is connected to the basic functional group by at least one covalent bond between a carbon atom of the aliphatic chain and an atom of the basic functional group. Optionally, the aliphatic chain is connected to the basic functional group by a first bond between a first atom of the aliphatic chain and the basic functional group and a second bond between a second atom of the aliphatic chain and the basic functional group, such that the particular compound is cyclic.

[0066] For example, the hydrophobic group may refer to an aryl group, which is connected to the basic functional group by at least one covalent bond between the carbon atom of the aryl group and the atom of the basic functional group.

[0067] For the purposes of this invention, a “C1-C6 aliphatic chain” is defined as a straight-chain or branched hydrocarbon chain, optionally forming one or more rings, and particularly comprising 1 to 6 carbon atoms. According to the invention, an aliphatic chain encompasses straight-chain or branched alkyl, alkenyl, or alkynyl groups, optionally comprising one or more rings. The aliphatic chain may optionally be substituted by one or more, for example, 1 to 3, substituents selected from C1-C6 alkyl or aryl groups.

[0068] For the purposes of this invention, the term "alkyl" refers to a saturated hydrocarbon chain. Examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl.

[0069] For the purposes of this invention, "alkenyl" is defined as a hydrocarbon chain containing at least one double bond. Examples include vinyl, propenyl, butenyl, pentenyl, and hexenyl.

[0070] For the purposes of this invention, "alkynyl" is defined as a hydrocarbon chain containing at least one triple bond. Examples include ethynyl, propynyl, butynyl, pentylyl, and hexynyl.

[0071] For the purposes of this invention, the term "aryl" refers to an aromatic hydrocarbon group, preferably comprising 6 to 10 carbon atoms and comprising one or more attached rings, such as phenyl or naphthyl. According to the invention, the aryl group may optionally be substituted by one or more, for example, 1 to 3, substituents selected from C1-C6 alkyl or aryl groups.

[0072] Preferably, before the first hydrophilic silica bonding surface is brought into contact with the second hydrophilic silica bonding surface, the surface concentration of the specific compound on each bonding surface made of hydrophilic silica, on which the specific compound has been deposited, is 10. 11 molecule / cm 2 Up to 10 15 molecule / cm 2 Between. 10 15 molecule / cm 2 The concentration corresponds to a monolayer, and therefore to the saturation of the hydrophilic bonded surface. Below 10 11 molecule / cm 2 The amount of molecules becomes difficult to detect, and the catalytic effect is not effective enough.

[0073] The presence of a specific compound and its surface concentration can be characterized by spectroscopic techniques such as X-ray fluorescence, Raman or infrared spectroscopy, or mass spectrometry.

[0074] The specific compound may advantageously contain 1 to 3 carbon atoms, or even more advantageously 1 to 2 carbon atoms. Alternatively, the specific compound may preferably have a molecular weight of less than 200 g / mol, or even more preferably less than 100 g / mol. The fewer carbon atoms the specific compound contains, the less likely it is to cause failure in components manufactured in assemblies comprising a first substrate and a second substrate at the bonding interface. Therefore, the risk of using a specific compound with fewer carbon atoms in a cleanroom is lower. In other words, contamination by such a specific compound will have fewer adverse consequences for the rest of the manufacturing chain or other manufacturing chains.

[0075] For example, the specific compound is a primary, secondary, or tertiary, cyclic or acyclic, saturated or unsaturated aliphatic amine that does not contain a double bond at the terminal position. A saturated aliphatic amine is defined as an amine that does not contain a double bond. An unsaturated aliphatic amine that does not contain a double bond at the terminal position is defined as an amine that contains at least one double bond between two carbon atoms, but does not contain a double bond between the last two carbon atoms of the aliphatic chain of any aliphatic amine.

[0076] Preferably, the specific compound is selected from methylamine (CH3NH2), dimethylamine (CH3)2NH, trimethylamine (CH3)3N, and piperidine (CH2)5NH. Amines have the advantage of being both basic and nucleophilic. In other words, amines can function according to the two mechanisms described above: either as a base to generate catalytic hydroxide ions, or as a nucleophile that directly participates in condensation reactions.

[0077] The specific compound is preferably not N-methylhydroxylamine. Surprisingly, N-methylhydroxylamine is disclosed in document FR 3 102771 B1, which describes a specific molecule defined as containing a hydrophilic functional group and a basic functional group separated by at least one atom, although N-methylhydroxylamine does not meet such a definition.

[0078] For example, the specific compound is an organic ion, preferably an aliphatic carboxylate ion, or even more preferably selected from formate ions (HCOO). - and acetate ions CH3COO - Aliphatic carboxylate ions. These compounds have the advantages of being very common, inexpensive, and relatively safe. As mentioned above, the counter ion of the organic ion is preferably selected from ammonium NH4. + nitrite NO + and nitrogen NO2 + These ions are advantageously neither alkali metals nor alkaline earth metals, and therefore have a less contaminating effect on microelectronic components than alkali metals or alkaline earth metals.

[0079] Adding specific compounds in liquid form

[0080] According to one particular implementation, the deposition of a particular compound includes the deposition of a liquid containing the particular compound.

[0081] For example, a liquid containing a specific compound is a solution obtained by dissolving the specific compound in a solvent. The concentration of the specific compound in this solution is preferably 10. -7 mol / L to 10 -1 Between mol / L, or even more preferably between 10 mol / L -6 mol / L to 10 -3 The concentration is between mol / L. Within this concentration range, the specific compound retains sufficient solubility to prevent crystal formation upon evaporation, while still being sufficiently concentrated to provide enough ions to the interface to accelerate the reaction. The solvent is preferably water or a mixture of water and isopropanol (IPA). IPA is used to improve the drying process of the plate by changing the surface tension of the solution.

[0082] Deposition of liquids containing specific compounds can be achieved, for example, by coating, spraying, or spin coating. Regardless of the deposition method, the liquid is preferably deposited at a temperature between 4°C and 28°C for a duration of 5 seconds to 5 minutes.

[0083] In practice, deposition at temperatures above 28°C can cause specific compounds to penetrate into the silicon oxide layer, thus leading to structural modification of the silicon oxide layer. However, such structural modification of the silicon oxide layer is undesirable, particularly because it can alter the dielectric properties of the silicon oxide layer, especially in the near-surface region, which is the active region (the region where charge carriers move) in very small devices: any perturbation of the electric field in such a region will change the behavior of the final device (e.g., a transistor or diode). Since the desired effect is the catalytic effect of specific compounds on surface reactions, it is important that the specific compounds remain on the surface to be effective.

[0084] Spraying refers to the projection of solution droplets onto a surface. Liquid deposition by spraying is typically carried out at ambient temperature, that is, at a temperature between 4°C and 28°C, and the duration of liquid projection is between 5 seconds and 5 minutes.

[0085] Coating involves immersing the plate in a solution and then removing it. Immersion is typically performed at room temperature, between 4°C and 28°C, for a duration of 5 seconds to 5 minutes.

[0086] Preferably, the deposition of the liquid containing the specific compound is performed using a rotating device. In other words, the deposition of the liquid containing the specific compound involves rotating a first hydrophilic silica bonded surface and depositing a certain volume of the liquid containing the specific compound at the center of the rotating first hydrophilic silica bonded surface, for example using a pipette, the rotation of the first hydrophilic silica bonded surface causing the volume of liquid containing the specific compound to spread across the entire first hydrophilic silica bonded surface.

[0087] For a first substrate with a diameter of 300 mm, the volume of the liquid containing the specific compound is preferably 1 cm³. 3 Up to 100cm 3 During the deposition of the volume, the rotational speed of the first hydrophilic silica bonding surface is preferably between 100 rpm and 3000 rpm.

[0088] After the volume of liquid containing the specific compound has been deposited, the first hydrophilic silica bonded surface is then kept rotating until the volume of liquid containing the specific compound is ejected and evaporated.

[0089] Preferably, the first hydrophilic silica bonding surface is kept rotating at a rotational speed between 100 rpm and 3000 rpm for a duration between 1 s and 1 min.

[0090] Depositing a liquid containing a specific compound using a rotary table is highly advantageous because it can be performed in machines commonly used in the microelectronics industry for bonding substrates. In fact, these machines already integrate the ability to deposit the volume of the liquid containing the specific compound, as well as the means to spread the volume as described above, for the purpose of cleaning and preparing the bonding surface. Therefore, those skilled in the art do not need to invest in new equipment to implement the invention according to this embodiment.

[0091] The first hydrophilic silica bonded surface is kept rotating until the volume of liquid containing the specific compound is ejected and evaporated, allowing the first hydrophilic silica bonded surface to dry while retaining a sufficient amount of the specific compound on the first hydrophilic silica bonded surface.

[0092] The choice of rotational speed allows, to some extent, the amount of a specific compound retained on the surface during bonding by adjusting the proportion of liquid volume containing that specific compound being ejected relative to the proportion of evaporation. Higher speeds allow for more efficient removal of excess solution and prevent droplet formation, while also increasing the evaporation rate. However, if the rotational speed exceeds 3000 rpm, too large a proportion of the liquid volume containing the specific compound is ejected, resulting in insufficient retention of that compound on the surface. If the speed is below 100 rpm, too large a proportion of the liquid volume containing the specific compound is evaporated, resulting in an excess of that compound on the surface, which can produce defects formed by solid particles (crystals, solid residues).

[0093] Furthermore, the amount of a specific compound retained on the surface can be adjusted using various parameters, such as the concentration of the specific compound in the liquid containing it and the pH value of the liquid that affects the surface charge of the oxide.

[0094] According to one particular embodiment of depositing a specific compound in liquid form, the hydrophilic silica bonded surface may be activated using plasma before depositing the liquid containing the specific compound. In fact, those skilled in the art know that plasma activation of silica bonded surfaces has a beneficial effect on bonding energy: in effect, plasma breaks many bonds, particularly Si-O-Si bonds, and generates highly reactive substances. When the plasma-activated surface is exposed to water or a humid atmosphere, these reactive substances react with water to form new surface Si-OH silanols. Thus, plasma activation ultimately increases the number of surface silanol groups, which can then react in a condensation reaction during bonding at substrate contact. The inventors emphasize the advantageous effect of combining plasma activation and depositing the specific compound in liquid form, because, all other parameters remaining constant, this combination allows for increased bonding energy compared to simple plasma activation or depositing the specific compound in liquid form alone. The inventors attribute this beneficial effect of the plasma-specific compound combination to the formation of an induced "sponge" surface layer that allows for the storage of a larger amount of water and the specific compound.

[0095] Plasma, for example, is formed from gases such as oxygen, nitrogen, helium, or argon.

[0096] Each hydrophilic silica-bonded surface on which a specific compound will be deposited can be exposed to the plasma for a duration of 1 s to 1 min.

[0097] Added in gaseous form

[0098] Alternatively, the deposition of the specific compound may involve exposure to a gas containing the specific compound.

[0099] The gas containing the specific compound may be selected from atmospheric air (if the specific compound is volatile), an inert gas, hydrogen, helium, or possible mixtures (including water vapor, e.g., a 40% humidity atmosphere in a cleanroom). This choice may be determined by, for example, the desire to reduce bonding defects formed during bonding.

[0100] The mole fraction (or partial pressure) of a specific compound in a gas, for example, in 102... -5 Up to 10 -2 Between (that is, 10 to 10,000 ppm).

[0101] The duration of exposure of each hydrophilic silica bonded surface on which a particular compound is to be deposited to the gas is between a few seconds and a few minutes, preferably between 10 seconds and 10 minutes.

[0102] The gas temperature is most advantageously between -10°C and 50°C. This temperature allows for control over the amount of specific compounds adsorbed onto the surface. Temperatures above 50°C will result in insufficient deposition of specific compounds.

[0103] According to one specific embodiment of depositing a specific compound in gaseous form, the hydrophilic silica bonding surface can be activated using plasma before being exposed to a gas containing the specific compound. Such plasma activation can be carried out by adding the compound in liquid form as described above, and allows for an increase in bonding energy compared to simple plasma activation or depositing the specific compound in gaseous form alone.

[0104] The first hydrophilic silicon oxide bonding surface is brought into contact with the second hydrophilic silicon oxide bonding surface.

[0105] The contact between the first and second hydrophilic silica bonding surfaces is carried out in such a manner that the specific compound is either not removed or has been completely removed between the step of depositing the specific compound and the contact step. In other words, for each hydrophilic silica bonding surface on which the specific compound has been deposited, the direct bonding method according to the invention does not include any step of cleaning or rinsing the surface between the deposition of the specific compound and the contact with the substrate. In particular, the rinsing step using ultrapure deionized water, which is conventionally used to remove particles and surface contaminants before bonding, is limited or more preferably eliminated so as not to remove the specific compound from the surface.

[0106] The contact between the first hydrophilic silica bonded surface and the second hydrophilic silica bonded surface is preferably carried out at a temperature between -10°C and 100°C, and even more preferably at room temperature (i.e., usually between 18°C ​​and 25°C) to control the amount of water and molecules present on the surface.

[0107] Making contact may include applying localized pressure to create a contact point between the first and second hydrophilic silicon oxide bonding surfaces. A bonding wave propagates from this contact point to the entire bonding interface within a few seconds. Alternatively, contact can be achieved without applying pressure. According to this embodiment, the first and second substrates can remain in contact for tens of seconds until air is expelled between the two substrates, causing the contact point to form and initiating bonding wave propagation. The vapor pressure when the first and second hydrophilic silicon oxide bonding surfaces are in contact is preferably between 1 Pa and 10 Pa. 5 Between Pa.

[0108] A specific compound was deposited on at least one of two hydrophilic silica bonding surfaces, the two hydrophilic silica bonding surfaces were then brought into contact, and the resulting assembly was maintained at room temperature (after the bonding wave had ceased propagation), allowing approximately 1 J / m² to be reached after several tens of hours.2 Up to 2 J / m 2 The bonding energy is on the order of magnitude higher. In contrast, without depositing the specific compound and keeping all other experimental parameters constant, such a bonding energy can only be reached after several days, and therefore is never truly reached because other phenomena interfere with the process. Therefore, depositing the specific compound improves the bonding kinetics and allows for the achievement of higher bonding energies.

[0109] To further improve the bonding dynamics, the direct bonding method may also include a subsequent hardening annealing step on the assembly obtained after the first substrate and the second substrate have come into contact.

[0110] Hardening annealing may include applying a temperature between 50°C and 250°C, preferably between 50°C and 100°C, even more preferably between 50°C and 90°C, for a duration preferably between 15 minutes and 4 hours, even more preferably between 15 minutes and 2 hours. The hardening annealing temperature is selected based on the properties of the first and second substrates and their ability or inability to withstand a given temperature.

[0111] For example, annealing components produced by depositing a specific compound and contacting a first substrate with a second substrate at 100°C allows the desired bonding energy (approximately 1 J / m²) to be achieved after only one hour of annealing. 2 or 2 J / m 2 (On the order of magnitude). Therefore, hardening annealing significantly improves the kinetics of the condensation reaction. Furthermore, it should be noted that such annealing temperatures are kept sufficiently low (below 200°C) to avoid the formation of gases and bubbles that could lead to bonding defects at the bonding interface, and to avoid generating significant thermal stress (which could occur at high temperatures if the substrates to be bonded have significantly different coefficients of thermal expansion), and it is also compatible with substrates having weakened regions and / or electronic component elements. The same bonding method, without depositing the specific compound, does not allow for a yield greater than 1 J / m through such hardening annealing. 2 The bonding energy.

[0112] Methods for transferring layers onto a supporting substrate

[0113] The present invention extends to a method for transferring a layer onto a supporting substrate.

[0114] The method of transferring a layer onto a support substrate includes the steps of providing a donor substrate comprising a first hydrophilic silicon oxide surface and a support substrate comprising a second hydrophilic silicon oxide surface.

[0115] The donor substrate and the support substrate are the first substrate and the second substrate as described above.

[0116] For example, the donor substrate and / or support substrate may contain silicon (Si), germanium (Ge), indium phosphide (InP), gallium arsenide (AsGa), aluminum oxide (Al2O3), silicon oxide (SiO2), silicon nitride (Si3N4), silicon carbide (SiC), gallium nitride (GaN), copper, titanium, nickel, LNO, and / or LTO.

[0117] The donor substrate and / or support substrate can be a multilayer structure comprising at least two layers. For example, the donor substrate is a dummy donor substrate comprising an LTO first layer and a silicon second layer. For example, the support substrate is silicon.

[0118] Furthermore, the donor substrate and / or support substrate may include one or more electronic component elements. For example, the donor substrate and / or support substrate may include copper interconnects insulated by silicon oxide portions.

[0119] Therefore, the steps of providing a donor substrate comprising a first hydrophilic silicon oxide surface and a support substrate comprising a second hydrophilic silicon oxide surface may include one or more sub-steps of layer arrangement and electronic component formation as described above.

[0120] As previously described, the donor substrate and the support substrate each include a first hydrophilic silicon oxide surface and a second hydrophilic silicon oxide surface. The first hydrophilic surface and / or the second hydrophilic surface are typically natural, thermal, chemical, or deposited oxide surfaces as previously described. Therefore, the steps of providing a donor substrate comprising a first hydrophilic silicon oxide surface and a support substrate comprising a second hydrophilic silicon oxide surface may include forming the natural, thermal, chemical, or deposited silicon oxide surfaces according to any of the foregoing embodiments.

[0121] The first and second hydrophilic silica surfaces can have the same properties (natural, thermal, chemical, or deposited). Alternatively, the first and second hydrophilic silica surfaces can have different properties.

[0122] The method of transferring a layer onto a support substrate further includes forming a weakening region within the donor substrate to define the layer to be transferred between a first hydrophilic surface and the weakening region. In a preferred embodiment, the weakening region is formed by implanting atomic material into the donor substrate, the implantation being performed through the first hydrophilic surface. The atomic material is implanted at a predetermined depth, which determines the thickness of the layer to be transferred. The implanted atomic material is preferably hydrogen and / or helium.

[0123] Subsequently, the method of transferring the layer onto the support substrate further includes bonding between the donor substrate and the support substrate, wherein the first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface are located at the bonding interface. The bonding between the donor substrate and the support substrate is achieved by a direct bonding method according to any of the foregoing embodiments. The addition of a specific compound may be performed on the first hydrophilic silicon oxide surface of the donor substrate, on the second hydrophilic silicon oxide surface of the support substrate, or simultaneously on both the first hydrophilic silicon oxide surface of the donor substrate and the second hydrophilic silicon oxide surface of the support substrate.

[0124] The layer transfer method ultimately involves separating the donor substrate along the weakened region to transfer the layer to be transferred onto the support substrate. Separation along the weakened region can be initiated by mechanical action and / or the application of thermal energy. Preferably, separation along the weakened region and hardening annealing are combined by applying a temperature ramp (with or without a temperature plateau) to stabilize the bonding interface.

[0125] Example

[0126] 10 mL of a concentration of 10 -4 g / cm 3 A solution of compounds with amino groups (glycine (also known as aminoacetic acid) ac-NH2 and ethanolamine NH2-C2H5O, respectively) was dispensed onto a first silicon substrate with a diameter of 200 mm, which had a 100 nm thick first hydrophilic silica bonded surface of the thermal oxide type. The system was rotated at 2000 rpm until the deposited solution film thickness was uniform. This uniformity could be routinely observed by the appearance of colored Newton's rings, which moved across the surface as the film thinned due to the combined effects of centrifugal flow and evaporation, until they disappeared when the film thickness was less than half the wavelength of visible light (i.e., typically less than 200 nm). The substrate was then kept rotating for about ten seconds to remove excess aqueous solution of the amino compounds and dry the first hydrophilic silica bonded surface.

[0127] A second silicon substrate with a diameter of 200 mm is provided, having a 100 nm thick thermal oxide-type second hydrophilic silicon oxide bonding surface, and is subjected to the same treatment as previously described for the first silicon substrate.

[0128] The first hydrophilic silicon oxide bonding surface is then brought into contact with a second bonding surface made of hydrophilic silicon oxide at room temperature to achieve direct bonding adhesion between the first and second substrates. The newly formed structure comprising the first and second substrates is then hardened by hardening annealing at a temperature range of 100°C to 500°C for 2 hours.

[0129] Finally, the bond energy, as a function of the hardening annealing temperature and the concentration of the deposited amine compound solution, was measured in an anhydrous atmosphere using a conventional blade insertion method known as the "Maszara method." The results were... Figure 2 Use triangle symbol (concentration 10) -4 g / cm 3 (glycine solution) and square symbols (concentration of 10) -4 g / cm 3 (The ethanolamine solution) is used to indicate this.

[0130] Comparative example

[0131] Perform the same procedures as in the examples, but use deionized water (DIW) instead of the amino compound solution. Results were... Figure 2 The symbol for the center is a hollow circle.

[0132] It can be observed that, compared with the reference exposed to deionized water, compounds containing amine groups achieve stronger bonding energies even at low annealing temperatures (100 to 200 °C).

Claims

1. A method for directly bonding two substrates, the method comprising the following steps: (a) Providing a first substrate and a second substrate, the first substrate and the second substrate respectively comprising a first bonding surface made of hydrophilic silicon oxide and a second bonding surface made of hydrophilic silicon oxide. (b) Depositing a specific compound on the first bonding surface made of hydrophilic silica, the specific compound being an organic compound consisting of a basic functional group and substituents of the basic functional group, each substituent being a hydrophobic group, the specific compound containing at least one carbon atom, and the hydrophobic group being capable of referring to a single hydrogen atom. (c) Contacting a first bonding surface made of hydrophilic silicon oxide on which the particular compound has been deposited with a second bonding surface made of hydrophilic silicon oxide to cause the first substrate to adhere to the second substrate.

2. The method according to claim 1, wherein, The specific compound is not N-methylhydroxylamine.

3. The method according to claim 1 or 2, further comprising depositing the specific compound on a second hydrophilic silica bonding surface, wherein adhesion between the first substrate and the second substrate is achieved by contacting the first hydrophilic silica bonding surface with the second hydrophilic silica bonding surface on which the specific compound has been deposited.

4. The method according to any one of claims 1 to 3, wherein the surface concentration of the specific compound on the first hydrophilic bonding surface is 10 before the first hydrophilic bonding surface, on which the specific compound has been deposited, comes into contact with the second hydrophilic bonding surface. 11 molecule / cm 2 Up to 10 15 molecule / cm 2 between.

5. The method according to any one of claims 1 to 4, wherein, The specific compound contains 1 to 3 carbon atoms, preferably 1 to 2 carbon atoms, and / or the molecular weight of the specific compound is less than 200 g / mol, preferably less than 100 g / mol.

6. The method according to any one of claims 1 to 5, wherein, The specific compound is a primary, secondary or tertiary, cyclic or acyclic, saturated or unsaturated aliphatic amine that does not contain a double bond at the terminal position, preferably selected from methylamine CH3NH2, dimethylamine (CH3)2NH, trimethylamine (CH3)3N and piperidine (CH2)5NH.

7. The method according to any one of claims 1 to 5, wherein, The specific compound is an organic ion, preferably an aliphatic carboxylate ion, more preferably selected from formate ions (HCOO). - and acetate ions CH3COO - The aliphatic carboxylate ion, wherein the counter ion of the organic ion is selected from ammonium NH4. + nitrite NO + and nitrogen NO2 + .

8. The method according to any one of claims 1 to 7, wherein, The deposition of the specific compound on the first hydrophilic silica bonded surface includes depositing a liquid containing the specific compound on the first hydrophilic silica bonded surface.

9. The method according to claim 8, wherein, The deposition of a liquid containing a specific compound on the first hydrophilic silica bonded surface includes: - A certain volume of liquid containing the specific compound is deposited at the center of the first hydrophilic silica bonded surface. - The volume of liquid containing the specific compound is spread by rotating the first hydrophilic silica bonded surface, the first hydrophilic silica bonded surface being rotated until the volume of liquid containing the specific compound is ejected and evaporated.

10. The method of claim 9, further comprising the step of exposing the first hydrophilic silica bonding surface to plasma before depositing the volume of liquid containing the particular compound at the center of the first hydrophilic silica bonding surface.

11. The method according to any one of claims 8 to 10, wherein, The liquid containing the specific compound is obtained by dissolving the specific compound in a solvent, preferably water or a mixture of water and isopropanol (IPA), wherein the concentration of the specific compound in the liquid is 10. -7 mol / L to 10 -1 Between mol / L.

12. The method according to any one of claims 1 to 7, wherein, The deposition of the specific compound on the first hydrophilic silica bonded surface includes exposing the first hydrophilic silica bonded surface to a gas containing the specific compound.

13. The method according to any one of claims 1 to 12, wherein, The first substrate and / or the second substrate are silicon substrates.

14. The method according to any one of claims 1 to 13, wherein, The first hydrophilic silica bonding surface and / or the second hydrophilic silica bonding surface are made of deposited oxides, chemical oxides, thermal oxides and / or native oxides.

15. The method according to any one of claims 1 to 14, wherein, The contact between the first bonding surface, on which the specific compound has been deposited, made of hydrophilic silica, and the second hydrophilic silica bonding surface is carried out at a temperature between 0°C and 100°C.

16. The method according to any one of claims 1 to 15, further comprising a hardening annealing step d) following step c) of contacting a first bonding surface made of hydrophilic silica on which the particular compound has been deposited with a second bonding surface made of hydrophilic silica, said hardening annealing preferably being performed at a temperature below 100°C, more preferably below 90°C, for a duration between 1 minute and 5 hours.

17. The method according to any one of claims 1 to 16, wherein, The first substrate is made of a first material, and the second substrate is made of a second material, wherein the difference in the coefficients of thermal expansion between the first material and the second material is greater than or equal to 10% in relative terms.

18. The method according to any one of claims 1 to 16, wherein, The first substrate is a multilayer structure comprising a first layer made of a first material and a second layer made of a second material, wherein the difference in the coefficients of thermal expansion between the first material and the second material is greater than or equal to 10% in relative terms.

19. The method according to any one of claims 1 to 18, wherein, The first substrate includes electronic component elements.

20. The method according to any one of claims 1 to 19, wherein, The first substrate includes a weakened region formed by implanting atomic or ionic material.

21. A method for transferring a layer onto a supporting substrate, the method comprising the steps of: a) Providing a donor substrate including a first hydrophilic silicon oxide surface and a support substrate including a second hydrophilic silicon oxide surface, b) A weakening region is formed within the donor substrate to define the layer to be transferred between the first hydrophilic silicon oxide surface and the weakening region. c) Bonding the donor substrate and the support substrate, wherein the first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface are located at the bonding interface, and the bonding between the donor substrate and the support substrate is performed by the bonding method according to any one of claims 1 to 17. d) Separate the donor substrate along the weakened region in order to transfer the layer to be transferred onto the support substrate.

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