Method for directly bonding two substrates

Abstract

The invention relates to a method for directly bonding two substrates, the method comprising the following steps: (a) providing a first substrate and a second substrate respectively comprising a first hydrophilic silicon oxide bonding surface and a second hydrophilic silicon oxide bonding surface; (b) depositing a specific compound on the first hydrophilic silicon oxide bonding surface, the specific compound being derived from the ammonia molecule or the ammonium ion by at least the substitution of a hydrogen atom with a hydroxyl -OH group and / or an amino -NH2 group, the specific compound not comprising carbon atoms; and (c) bringing the first hydrophilic silicon oxide bonding surface on which the specific compound has been deposited into contact with the second hydrophilic silicon oxide bonding surface, so that the first substrate is adhered to the second substrate.

Description

[0001] DESCRIPTION

[0002] TITLE: Direct bonding process between two substrates

[0003] TECHNICAL FIELD

[0004] The invention relates to a method for direct bonding between two substrates.

[0005] STATE OF THE ART

[0006] Direct bonding is a technique widely used in microelectronics to assemble substrates and form multilayer structures. It consists of directly bringing the two surfaces to be bonded into contact, which will spontaneously adhere to each other, without additional material, particularly without the addition of a polymer adhesive. It is possible to have a few monolayers of water adsorbed on the surfaces to be bonded, particularly if they are hydrophilic, but the surfaces to be bonded must be macroscopically dry.

[0007] Spontaneous adhesion between the two surfaces to be bonded occurs under the effect of various attractive forces between the materials, for example under the effect of Van der Waals forces, capillary forces and / or hydrogen bonds involving water molecules adsorbed on the surfaces to be bonded. Covalent bonds can also be established between the two surfaces to be bonded.

[0008] For example, in the case where the surfaces to be bonded are hydrophilic silicon surfaces or silicon oxide surfaces, the adhesion between the two surfaces results mainly from condensation reactions between the silanols of the first surface to be bonded on the one hand and the silanols of the second surface to be bonded on the other hand. More precisely, each condensation reaction generates a siloxane bond between the two surfaces to be bonded and releases a water molecule according to the following reaction (I):

[0009] Sii-OH + Si2-OH -> Sii-O-Si2+ H2O (I)

[0010] The attractive forces mentioned above only act at short range and the formation of covalent bonds requires that the reactants are close enough for their molecular orbitals to overlap. Direct bonding therefore requires that the surfaces to be bonded are clean and flat, and have very low roughness, for example, a roughness below 0.5 nm. Typically, the reaction (I) mentioned above can only take place at the contact points between the two surfaces to be bonded. Furthermore, such a reaction (I) is very slow and equilibrated (not complete) at room temperature. 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 difficulties mentioned above, the bonding energy between two surfaces bonded by direct bonding at room temperature is not sufficient to guarantee good mechanical strength of the resulting multilayer structure in subsequent applications of said multilayer structure, for example if the multilayer structure is used in a process inducing high mechanical stresses on the bonding interface. Indeed, the bonding energy between two surfaces following direct bonding at room temperature of the two surfaces rarely reaches 200 mJ / m. 2 when the two surfaces adhere under the effect of the attractive forces previously mentioned. The reaction (I) of condensation of silanols does not allow to exceed 0.5 J / m 2 , even after several days.

[0011] One solution to increase the bonding energy is to heat the bonding interface after the two surfaces to be bonded have come into contact. For example, bringing two hydrophilic silicon or silicon oxide surfaces to be bonded into contact can be followed by heat treatment of the bonding interface at 200°C for 2 hours. Since the condensation reaction (I) is endothermic, the heat input will promote the said reaction.

[0012] However, such high temperatures can induce, at the bonding interface, the formation of gases and bubbles causing bonding defects, as well as significant thermal stress, particularly when the two substrates to be bonded have very different thermal expansion coefficients. Indeed, in the latter case, the difference in behavior of the two substrates under the effect of temperature variations is such that it will induce the opening of the bonding interface before it has had time to strengthen.

[0013] Document FR 3 102 771 B1 advantageously proposes to obtain a high bonding energy at low temperature between two hydrophilic bonding surfaces by depositing a specific molecule on at least one hydrophilic bonding surface prior to bringing the two substrates to be bonded into contact, the at least one hydrophilic bonding surface on which the specific molecule has been deposited being at the bonding interface. Document FR 3 102 771 B1 specifies that the specific molecule is an organic molecule that must comprise a hydrophilic group allowing the specific molecule to chemisorb onto the hydrophilic surface to be bonded, as well as a basic group allowing the pH of the water monolayers adsorbed on the surface to be increased, the hydrophilic group and the basic functional group being separated by at least one carbon atom. The bonding method described by document FR 3 102 771 B1 makes it possible to obtain bonding energies greater than 1 J / m 2with bond consolidation annealing temperatures below 100°C. However, the organic molecules described by FR 3 102 771 B1 are sources of carbon. The presence of carbon at the bonding interface can cause bonding defects due to its essentially hydrophobic nature. These defects can themselves lead to mechanical or electrical failures of the bonding interface.

[0014] Another solution is to treat at least one of the surfaces to be bonded with gaseous ammonia NH3 or with an aqueous ammonia solution NH4OH. Since ammonia partially reacts with water to generate ammonium ions NH4+ and hydroxide ions, this solution is also often called ammonium hydroxide solution. Ammonia is a weak base that will react with the water adsorbed on the surface to be bonded, and thus generate hydroxide ions OH- according to the following acid-base reaction (2):

[0015] NH3+ H2O= NH4+ + HO' (2)

[0016] The hydroxide ions generated by the acid-base reaction (2) act as catalysts for the condensation reaction (I) and therefore increase its kinetics.

[0017] However, ammonia NH3 is extremely volatile: the evaporation of surface ammonia results in a shift in the equilibrium of the acid-base reaction (2) towards the regeneration of ammonia NH3 and therefore the consumption of catalytic hydroxide ions. In other words, it is difficult to maintain and control the quantity of ammonia actually present on the surface to be bonded even though this maintenance is necessary for the proper functioning of the basic catalytic effect of the hydroxide ions as previously described.

[0018] BRIEF DESCRIPTION OF THE INVENTION

[0019] An aim of the invention is to design a method for direct bonding at low temperature between two substrates making it possible to obtain bonding energies compatible with use of the structure resulting from the bonding of the two substrates in conventional microelectronic applications such as the manufacture of Silicon On Insulator substrates or other assemblies, typically to obtain energies greater than 1J / m 2 , while overcoming the aforementioned drawbacks of the state of the art.

[0020] To this end, the invention proposes a method for direct bonding between two substrates comprising the following steps: (a) providing a first substrate and a second substrate respectively comprising a first bonding surface made of hydrophilic silicon oxide and a second bonding surface made of hydrophilic silicon oxide,

[0021] (b) depositing a specific compound on the first hydrophilic silicon oxide bonding surface, the specific compound being derived from the ammonia molecule by at least the substitution of a hydrogen atom by a hydroxyl group -OH and / or an amino group - NH2, the specific compound not comprising carbon atoms,

[0022] (c) bringing the first hydrophilic silicon oxide bonding surface on which the specific compound has been deposited into contact with the second hydrophilic silicon oxide bonding surface, so as to obtain adhesion of the first substrate with the second substrate.

[0023] For the purposes of the present invention, the term "hydrophilic silicon oxide bonding surface" means a silicon oxide surface having Si-OH silanol groups.

[0024] The specific compound as defined makes it possible to obtain, with a low thermal budget (typically without consolidation annealing after bringing the two substrates to be bonded into contact), bonding energies greater than 1 J / m 2 in reasonable times. The specific compound makes it possible to increase the bonding energy between the first substrate and the second substrate by a factor of more than 2 compared to an identical bonding process without deposition of the specific compound. For example, it is possible to obtain a bonding energy twice as high at the same time and consolidation annealing temperature, or to obtain an identical bonding energy in a much shorter time and / or a lower consolidation annealing temperature.

[0025] The inventors attribute the achievement of the previously mentioned high bonding energies at a low thermal budget to a catalytic effect of the specific compound which would thus improve the kinetics of the condensation reactions at the origin of the adhesion between the first substrate and the second substrate and would also shift the equilibrium.

[0026] The inventors propose two mechanisms that could explain the catalytic effect of the specific compound:

[0027] - the first would be based on the nucleophilic character of the amino group or the hydroxyl group of the specific compound: the nucleophilic addition or substitution of the specific compound on the silicon atoms of the first bonding surface in hydrophilic silicon oxide would generate very reactive reaction intermediates, so that the condensation reaction on these reaction intermediates would be facilitated. In this case, we speak of a nucleophilic catalytic effect of the specific compound.

[0028] - the second would be based on the basic character of the specific compound: the amino group and / or the hydroxyl group of said specific compound would react with the water adsorbed on the surface to be bonded, and thus generate hydroxide ions OH-. Said hydroxide ions would in turn act as catalysts for the condensation reaction between the two substrates, as shown in Figure 1. In this case, we speak of a basic catalytic effect of the specific compound.

[0029] Both mechanisms probably occur together, with one being able to dominate over the other depending on the nature of the specific compound (and its basic character relative to its nucleophilic character) as well as the nature of the first hydrophilic bonding surface and the second hydrophilic bonding surface and other experimental parameters.

[0030] The specific compound has the nucleophilic and / or basic character of the ammonia from which it is derived, while being less volatile than said ammonia.

[0031] Furthermore, the specific compound does not contain any carbon element, making it a low-polluting compound. The presence of carbon, particularly in the form of hydrocarbons that are not very chemically reactive with silicon and silicon oxide, will induce the formation of bonding defects that will be difficult to heal, even after extensive annealing. Nitrogen or oxygen will be much more easily integrated into the silicon oxide film.

[0032] According to other optional features of the invention taken alone or in combination when technically possible:

[0033] - the specific compound is not hydrazine;

[0034] - the method further comprises depositing the specific compound on the second hydrophilic silicon oxide bonding surface, the adhesion of the first substrate with the second substrate being obtained by bringing into contact the first hydrophilic silicon oxide bonding surface and said second hydrophilic silicon oxide bonding surface on which the specific compound has been previously deposited;

[0035] - the surface concentration of the specific compound on the first hydrophilic silicon oxide bonding surface prior to bringing the first hydrophilic silicon oxide bonding surface on which said specific compound has been deposited into contact with the second hydrophilic silicon oxide bonding surface is between 10 11 molecules / cm 2 and 10 15 molecules / cm 2 ;

[0036] - the specific compound comprises only nitrogen, oxygen and / or hydrogen atoms; - the specific compound is chosen from hydroxylamine and hydroxylhydrazine;

[0037] - the deposition of the specific compound on the first hydrophilic silicon oxide bonding surface comprises the deposition on the first hydrophilic silicon oxide bonding surface of a liquid comprising the specific compound;

[0038] - the deposition on the first hydrophilic silicon oxide bonding surface of the liquid comprising the specific compound comprises: the deposition of a volume of the liquid comprising the specific compound in the center of the first hydrophilic silicon oxide bonding surface, the spreading of said volume of the liquid comprising the specific compound by rotation of the first hydrophilic silicon oxide bonding surface, said first hydrophilic silicon oxide bonding surface being kept in rotation until ejection and evaporation of the volume of liquid comprising the specific compound;

[0039] - the method further comprises a step of exposing the first hydrophilic silicon oxide bonding surface to a plasma prior to the deposition of the volume of liquid comprising the specific compound at the center of the first hydrophilic silicon oxide bonding surface;

[0040] - the liquid comprising the specific compound is obtained by dissolving the specific compound in a solvent, preferably in water or in a mixture of water and isopropyl alcohol (IPA);

[0041] - the liquid deposition is preferably carried out at a temperature between 4°C and 28°C for a duration between 5 s and 5 min;

[0042] - depositing the specific compound on the first hydrophilic silicon oxide bonding surface comprises exposing said first hydrophilic silicon oxide bonding surface to a gas comprising the specific compound;

[0043] - the first substrate and / or the second substrate are silicon substrates;

[0044] - the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface are made of deposited oxide, thermal oxide, chemical oxide and / or native oxide;

[0045] - the contacting of the first hydrophilic silicon oxide bonding surface on which the specific compound has been deposited and the second hydrophilic silicon oxide bonding surface is carried out at a temperature between -10°C and 60°C;

[0046] - the method further comprises a step d) of consolidation annealing carried out after step c) of bringing into contact the first bonding surface made of hydrophilic silicon oxide on which the specific compound has been deposited and the second bonding surface made of hydrophilic silicon oxide, the consolidation annealing being preferably carried out at a temperature below 100°C, even more preferably below 90°C for a duration of between 15 min and 2 h; - the first substrate is made of a first material and the second substrate is made of a second material, the difference in coefficient of thermal expansion between the first material and the second material being greater than or equal to 10% in relative value;

[0047] - 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, the difference in coefficient of thermal expansion between the first material and the second material being greater than or equal to 10% in relative value;

[0048] - the first substrate comprises electronic component elements;

[0049] - the first substrate comprises a weakening zone formed by implantation of atomic or ionic species;

[0050] The invention extends to a method for transferring a layer onto a support substrate, said method comprising the following steps: a) providing a donor substrate comprising a first surface made of hydrophilic silicon oxide and a support substrate comprising a second surface made of hydrophilic silicon oxide, b) forming a weakening zone within the donor substrate so as to delimit a layer to be transferred between the first surface made of hydrophilic silicon oxide and the weakening zone, c) bonding between the donor substrate and the support substrate, the first surface made of hydrophilic silicon oxide and the second surface made of hydrophilic silicon oxide being at the bonding interface and the bonding between the donor substrate and the support substrate being implemented by a bonding method as previously described,d) detaching the donor substrate along the weakening zone so as to transfer the layer to be transferred onto the support substrate.,

[0051] BRIEF DESCRIPTION OF THE FIGURES

[0052] Other features and advantages of the invention will emerge from the detailed description which follows.

[0053] Figure 1 illustrates the nucleophilic role of the hydroxide ion in the condensation reaction of silanols which causes the formation of a Si-O-Si siloxane bond between the two surfaces to be bonded.

[0054] Figure 2 illustrates the beneficial effect on the bonding energy of the invention by comparing the evolution during the annealing of surfaces treated or not with hydroxylamine, at different concentrations.

[0055] DETAILED DESCRIPTION OF EMBODIMENTS The direct bonding method according to the invention comprises a first step of providing a first substrate comprising a first bonding surface made of hydrophilic silicon oxide and a second substrate comprising a second bonding surface made of hydrophilic silicon oxide.

[0056] Providing a first substrate comprising a first hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface.

[0057] The first substrate and / or the second substrate may be, for example, made of a material chosen from silicon Si, germanium Ge, indium phosphide InP, gallium arsenide AsGa, alumina AI2O3, silicon oxide SiO2, silicon nitride SiaN4, silicon carbide SiC, gallium nitride GaN, copper, titanium, nickel, lithium niobate LiNbOa (known to those skilled in the art by the acronym LNO) and lithium tantalate LiTaOa (known to those skilled in the art by the acronym LTO).

[0058] Alternatively, the first substrate and / or the second substrate may be multilayer structures comprising at least two layers. For example, the first substrate - respectively the second substrate - comprises a first layer made of a first material and a second layer made of a second material. The first material and the second material are for example chosen 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 comprise one or more sub-steps of assembling said layers, so as to form the first substrate and / or the second substrate.

[0059] The direct bonding method according to the invention is particularly advantageous when the first substrate and / or the second substrate comprise layers made of materials having a large difference in coefficient of thermal expansion. A large difference in coefficient of thermal expansion is understood to mean a difference in relative value of 10% or more between the values ​​of said coefficients of thermal expansion.

[0060] Furthermore, the first substrate and / or the second substrate may comprise one or more electronic component elements. For example, the first substrate and / or the second substrate comprise metal parts such as copper lines and silicon oxide insulating parts (hybrid bonding). Similarly, the step of providing a first substrate comprising a first hydrophilic bonding surface and a second substrate comprising a second hydrophilic bonding surface may in this case comprise one or more sub-steps of forming said electronic component elements.

[0061] The direct bonding method according to the invention is particularly advantageous when the first substrate and / or the second substrate comprise such electronic component elements because during heating, the different elements of such a system expand differently (metals, insulators, semiconductors) and this can generate significant stresses 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 operating temperature of the device, which is generally less than 200°C.

[0062] Finally, the first substrate and / or the second substrate may also comprise a weakening zone formed for example by implantation of atomic and / or ionic species.

[0063] The direct bonding method according to the invention is particularly advantageous when the first substrate and / or the second substrate comprise such a weakened zone because the weakened zone must then be the weakest in the material, otherwise fracture control will be difficult. All other interfaces must therefore be reinforced at the time of fracture.

[0064] The first substrate and the second substrate may be of the same nature 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 having a large difference in coefficient of thermal expansion.

[0065] First bonding surface made of hydrophilic silicon oxide and second bonding surface made of hydrophilic silicon oxide

[0066] As previously mentioned, the first substrate and the second substrate respectively comprise a first bonding surface made of hydrophilic silicon oxide and a second bonding surface made of hydrophilic silicon oxide. A hydrophilic bonding surface is understood to mean a surface that has a strong affinity with water, such that at least one monolayer of water remains naturally adsorbed on the hydrophilic bonding surface. The contact angle of a hydrophilic surface is typically less than about ten degrees. To be hydrophilic, the silicon oxide surface does not comprise, in particular, surface silicon hydride groups -Si-H, or the ratio between the number of silicon hydride groups -Si-H to the number of surface silanol groups is less than 20%. Preferably, the silicon oxide surface does not comprise surface silicon hydride groups -Si-H that will have been transformed into SiOH, for example by the action of water in a basic medium.

[0067] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be native silicon oxide surfaces. In other words, if the first substrate and / or the second substrate comprise a material naturally forming an oxide layer on its surface - called a native silicon oxide layer -, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be the surface of said native oxide layer. This is for example the case of silicon and silicon carbide which naturally form an oxide layer whose thickness is of the order of 1 nm.If the first substrate and / or the second substrate are made of silicon oxide or comprise a layer of silicon oxide, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be directly the surface of said silicon oxide.

[0068] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be thermal silicon oxide surfaces. According to this embodiment, the step of providing a first substrate comprising a first hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface may comprise a sub-step of forming a first thermal silicon oxide layer on the first substrate and / or a sub-step of forming a second thermal silicon oxide layer on the second substrate, a surface of the first, respectively of the second, thermal silicon oxide layer forming the first, respectively the second, hydrophilic silicon oxide bonding surface.

[0069] Thermal oxide means an oxide formed by direct oxidation of a material by exposing said material, at high temperature, to oxygen (dry oxidation), water (wet oxidation) or possibly other oxidants (e.g. N2O).

[0070] A thermal silicon oxide layer may be formed on the surface of a silicon substrate or a silicon carbide substrate. For this purpose, a silicon substrate is for example heated to a temperature preferably between 800°C and 1200°C and then a surface of said silicon substrate is exposed to an atmosphere of dioxygen or water vapor. The oxidation temperature conditions the growth rate of the thermal silicon oxide layer from the surface of the silicon substrate exposed to the atmosphere of dioxygen or water vapor. In the case of wet thermal oxidation, the formation of the thermal silicon oxide layer may comprise the combustion of dihydrogen by dioxygen in a torch and the exposure of the substrate to the water vapor produced by said combustion, the heat generated by this same combustion reaction being further used to bring the substrate to the temperature chosen for thermal oxidation.

[0071] The thickness of the thermal silicon oxide layer is for example between 1 nm and 1 pm.

[0072] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be chemical silicon oxide surfaces. According to this embodiment, the step of providing a first substrate comprising a first hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface may comprise a sub-step of forming a first chemical silicon oxide layer on the first substrate and / or a sub-step of forming a second chemical silicon oxide layer on the second substrate, a surface of the first, respectively of the second, chemical silicon oxide layer forming the first, respectively second, hydrophilic silicon oxide bonding surface.

[0073] A chemical oxide is understood to mean an oxide formed by oxidation of a material at low temperature (preferably at room temperature), in the presence of water or certain oxidants such as hydrogen peroxide H2O2 or ozone O3. A layer of chemical silicon oxide can be formed in this way on the surface of a silicon, silicon carbide or silicon nitride substrate, by exposing said surface at low temperature to water or to an oxidant such as previously mentioned. The thickness of the layer of chemical silicon oxide on the surface of the silicon substrate is for example between 0.5 nm and 3 nm.

[0074] For example, the first hydrophilic silicon oxide bonding surface and / or the second hydrophilic silicon oxide bonding surface may be deposited silicon oxide surfaces. 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 comprise a sub-step of depositing a first layer of silicon oxide deposited on the first substrate and / or a sub-step of depositing a second layer of silicon oxide deposited on the second substrate, a surface of the first, respectively of the second, deposited oxide layer forming the first, respectively the second, hydrophilic silicon oxide bonding surface.

[0075] A deposited oxide is an oxide formed by chemically adding material, for example in the form of vapor or plasma. A layer of silicon oxide can be deposited on almost any type of material, including IV / 1 V, III / V and II / VI semiconductors as well as oxides such as LiTaCh or LiNbOa. The thickness of the deposited silicon oxide layer is, for example, between 1 nm and 10 pm.

[0076] For the deposition of a silicon oxide layer, the precursor providing the silicon is typically silane (SiH4) while the precursor providing the oxygen is, for example, N2O or O2. For example, the substrate on which the silicon oxide layer is to be deposited is placed in a plasma chamber. Then, a carrier gas, for example dihydrogen, comprising the precursors of silicon and oxygen, for example SiH4 and N2O, is introduced into said plasma chamber. Under the effect of the plasma, the precursors decompose and react, forming a layer of silicon oxide on the surface of the substrate exposed to the plasma.

[0077] The methods for forming the silicon oxide layer previously described are given for illustrative purposes and are in no way limiting of the scope of the invention and may be adapted by a person skilled in the art to the envisaged application case. For example, the method for depositing a silicon oxide layer may comprise the application of magnetic fields or microwaves to accelerate the deposition. Other carrier gases or precursors may be used.

[0078] If the first substrate and / or the second substrate are made of silicon oxide or comprise a silicon oxide layer and / or if the first substrate and / or the second substrate are made of a material naturally forming a silicon oxide layer on the surface or comprise such a material, the provision of the first substrate comprising a first bonding surface of hydrophilic silicon oxide and of the second substrate comprising a second bonding surface of hydrophilic silicon oxide may still comprise the formation of a first thermally or chemically deposited silicon oxide layer on the first substrate and / or the formation of a second thermally or chemically deposited silicon oxide layer on the second substrate such that a surface of the first, respectively of the second, thermally or chemically deposited silicon oxide layer forms the first, respectively the second, hydrophilic silicon oxide bonding surface.

[0079] The first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface may be of the same nature or of different nature. For example, the first hydrophilic silicon oxide bonding surface may be a chemical silicon oxide surface and the second hydrophilic silicon oxide bonding surface a native silicon oxide surface. In this case, the step of providing a first substrate comprising a hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface may comprise a sub-step of forming a chemical silicon oxide layer on the first substrate. For further example, the first hydrophilic silicon oxide bonding surface may be a thermal silicon oxide surface and the second hydrophilic silicon oxide bonding surface a deposited silicon oxide surface.In this case, the step of providing a first substrate comprising a hydrophilic silicon oxide bonding surface and a second substrate comprising a second hydrophilic silicon oxide bonding surface may comprise a sub-step of forming a thermal silicon oxide layer on the first substrate and a sub-step of forming a silicon oxide layer deposited on the second substrate.

[0080] Such combinations are cited as examples and are in no way limiting of the scope of the invention. Any combination between native, chemical, thermal and deposited silicon oxide surfaces of the first substrate and the second substrate remains covered by the present invention.

[0081] Furthermore, depending on the nature of the first, respectively second, substrate that he wishes to obtain (monoblock substrate, or multilayer structure comprising materials having very different thermal expansion coefficients, possibly comprising electronic component elements and / or a weakening zone) and the application envisaged for the assembly resulting from the bonding between the first substrate and the second substrate (for example the manufacture of silicon on insulator or piezoelectric on insulator) the person skilled in the art is able to choose the nature of the silicon oxide most suitable for the first, respectively second, substrate, as well as the order of sequence of the various sub-steps previously mentioned making it possible to provide the expected first, respectively second, substrate.

[0082] Deposition of a specific compound on at least the first hydrophilic silicon oxide bonding surface The method further comprises a step of depositing a specific compound on the first hydrophilic silicon oxide bonding surface, or on both the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface.

[0083] The specific compound is a derivative of the ammonia molecule or the ammonium ion by at least the substitution of one hydrogen atom by a hydroxyl group -OH and / or an amino group -NH2, the specific compound not comprising carbon atoms.

[0084] Preferably, the specific compound only comprises nitrogen, oxygen and / or hydrogen atoms. The compound will thus be more easily incorporated by silicon oxide, in the form of a group - Si-ON, - SiOH or Si-NH.

[0085] Preferably, the specific compound is not hydrazine, since hydrazine is an explosive compound, which makes its use delicate.

[0086] More preferably still, the specific compound is chosen from hydroxylamine and hydroxylhydrazine.

[0087] Preferably, the surface concentration of the specific compound on each hydrophilic silicon oxide bonding surface on which the deposition of the specific compound has been carried out is, prior to bringing the first hydrophilic silicon oxide bonding surface into contact with the second hydrophilic silicon oxide bonding surface, between 10 11 molecules / cm 2 and 10 15 molecules / cm 2 . A concentration of 10 15 molecules / cm 2 corresponds to a monolayer and therefore to a saturation of the hydrophilic bonding surface. Below 10 11 molecules / cm 2the quantity of molecules becomes difficult to detect, and the catalytic effect is not effective enough.

[0088] The presence of the specific compound and the surface concentration of said specific compound can be characterized by different spectroscopic techniques such as X-ray fluorescence, Raman or infrared spectroscopy, or mass spectroscopy dosage.

[0089] Provision of the specific compound in liquid form

[0090] According to a particular embodiment, the deposition of the specific compound comprises the deposition of a liquid comprising the specific compound. For example, the liquid comprising the specific compound is a solution resulting from the dissolution of the specific compound in a solvent. The concentration of specific compound in said solution is preferably between 10' 6 mol / L and 1 mol / L, preferably between 10' 5 and 10' 1mol / L. In such a concentration range, the specific compound remains sufficiently soluble, so that the formation of crystals upon evaporation is avoided, while being concentrated enough to bring enough ions to the interface to accelerate the reaction. The solvent is preferably water or a mixture of water and IPA (isopropyl alcohol). IPA is used to improve the plate drying process by modifying the surface tension of the solution.

[0091] The deposition of the liquid comprising the specific compound can be carried out for example by coating, by spraying or by spin-coating (better known to those skilled in the art under the English term “spin-coating”). Whatever the method of deposition of the liquid, said liquid deposition is preferably carried out at a temperature between 4°C and 28°C for a duration between 5 s and 5 min.

[0092] Indeed, a deposition carried out at a temperature above 28°C could lead to penetration of the specific compound into the silicon oxide layer and therefore a structural modification of said silicon oxide layer. However, such a structural modification of the silicon oxide layer is not desirable, in particular because it could lead to a modification of the dielectric properties of the silicon oxide layer and in particular in the area close to the surface which is however an active area (area in which the carriers move) on very small devices: any disturbance of the electric field in such an area will modify the behavior of the final device, for example a transistor or a diode. The desired effect being a catalysis of surface reactions by the specific compound, it is important that the specific compound remains on the surface to be effective.

[0093] Spraying refers to the projection of droplets of solutions onto the surface. Liquid deposition by spraying is typically carried out at room temperature, i.e. between 4°C and 28°C, and the liquid is projected for a duration of between 5 s and 5 min.

[0094] Coating means the dipping of the plates in the solution followed by their removal. The immersion of a plate in the solution is typically carried out at room temperature, therefore at a temperature between 4°C and 28°C, for a duration between 5 s and 5 min. Preferably, the deposition of the liquid comprising the specific compound is carried out using a spinner. In other words, the deposition of the liquid comprising the specific compound comprises rotating the first hydrophilic silicon oxide bonding surface and depositing a volume of the liquid comprising the specific compound in the center of the rotating first hydrophilic silicon oxide bonding surface, for example using a pipette, the rotation of the first hydrophilic silicon oxide bonding surface making it possible to spread said volume of the liquid comprising the specific compound over the entire first hydrophilic silicon oxide bonding surface.

[0095] The volume of the liquid comprising the specific compound is preferably between 1 cm 3 and 100 cm 3 for a first substrate with a diameter of 300 mm, while the rotation speed of the first hydrophilic silicon oxide bonding surface during the deposition of said volume is preferably between 100 rpm and 3000 rpm.

[0096] Following the deposition of the volume of liquid comprising the specific compound, the first hydrophilic silicon oxide bonding surface is then kept rotating until the volume of liquid comprising the specific compound is ejected and evaporated.

[0097] Preferably, the first hydrophilic silicon oxide bonding surface is kept rotating at a rotation speed of between 100 rpm and 3000 rpm for a duration of between 1 s and 1 min.

[0098] The deposition of the liquid comprising the specific compound on the spinner is very advantageous insofar as it can be implemented in machines conventionally used for bonding substrates in the microelectronics industry. Indeed, said machines already integrate, for the purposes of cleaning and preparing surfaces for their bonding, the equipment which allows the deposition of the volume of liquid comprising the specific compound and the spreading of said volume as previously described. The person skilled in the art therefore does not need to invest in new equipment to implement the invention according to this embodiment.

[0099] Maintaining rotation of the first hydrophilic silicon oxide bonding surface until ejection and evaporation of the volume of liquid comprising the specific compound makes it possible to dry the first hydrophilic silicon oxide bonding surface, while retaining a sufficient quantity of specific compound on the first hydrophilic silicon oxide bonding surface. The choice of rotation speed makes it possible, to a certain extent, to modulate the quantity of specific compound remaining on the surface at the time of bonding by modulating the portion of the volume of liquid comprising the specific compound which is ejected relative to the portion of said volume which is evaporated. If the rotation speed is greater than 3000 rpm, too large a portion of the volume of liquid comprising the specific compound is ejected so that not enough specific compound remains on the surface.Conversely, if the speed is lower than 100 rpm, too much of the liquid volume comprising the specific compound evaporates, so that there is too much specific compound on the surface, which could create defects formed by solid particles (crystals, solid residues).

[0100] Furthermore, said amount of specific compound retained on the surface can be adjusted using different parameters, such as the concentration of specific compound of the liquid comprising the specific compound and the pH of said liquid which influences the surface charge of the oxide.

[0101] According to a particular embodiment of the deposition of the specific compound in liquid form, the deposition of the liquid comprising the specific compound may be preceded by an activation of the hydrophilic silicon oxide bonding surface using a plasma. Indeed, the activation of a silicon oxide bonding surface by plasma is known to those skilled in the art to have a beneficial effect on the bonding energy: the plasma in fact makes it possible to break numerous bonds, in particular Si-O-Si bonds and to generate highly reactive species. Upon exposure of the plasma-activated surface to water or a humid atmosphere, said reactive species will react with the water to form new surface Si-OH silanols. Thus, the plasma activation ultimately makes it possible to increase the number of surface silanol groups which will then be able to react in the condensation reactions when the substrates are brought into contact for bonding.The inventors have demonstrated a beneficial effect of the combination of plasma activation and deposition of the specific compound in liquid form since such a combination, all parameters otherwise unchanged, makes it possible to increase the bonding energy compared to simple plasma activation or to the sole deposition of the specific compound in liquid form. The inventors attribute this beneficial effect of the combination between plasma and specific compound to the formation of an induced “sponge” surface layer which makes it possible to store a greater quantity of water and specific compound.

[0102] Plasma is, for example, a plasma formed from a gas such as oxygen, nitrogen, helium, or argon. Each hydrophilic silicon oxide bonding surface on which the specific compound is to be deposited can be exposed to said plasma for a period of between 1 s and 1 min.

[0103] Intake in gaseous form

[0104] Alternatively, deposition of the specific compound may comprise exposure to a gas comprising said specific compound.

[0105] The gas comprising the specific compound may, for example, be chosen from atmospheric air (if the specific compound is volatile), rare gases, hydrogen, helium or possible mixtures including water vapor (for example, the 40% humid atmosphere of a clean room). This choice may be dictated, for example, by the desire to reduce certain defects formed during bonding, in particular edge voids.

[0106] The gas comprises the specific compound in the form of vapors, for example, hydroxylamine or hydrazine vapors.

[0107] The concentration of specific compound in the gas is preferably between 1 / 1000 and 1 and / or the partial pressure of specific compound is for example between 1 mbar and 1 bar.

[0108] Each hydrophilic silicon oxide bonding surface on which the specific compound is to be deposited is exposed to said gas for a period preferably between 1 second and 5 minutes.

[0109] The temperature of the substrates exposed to the gas is very advantageously between -10°C and 50°C to adjust the amount of specific compound adsorbed on the substrate. Indeed, the temperature of the gas makes it possible to control the amount of specific compound that adsorbs on the surface. A temperature above 50°C would lead to insufficient deposition of specific compound.

[0110] According to a particular embodiment of the deposition of the specific compound in gaseous form, the exposure of the hydrophilic silicon oxide bonding surface to the gas comprising the specific compound may be preceded by an activation of the hydrophilic silicon oxide bonding surface using a plasma. Such plasma activation may be implemented as previously described for the supply in liquid form, and makes it possible to increase the bonding energy compared to simple plasma activation or to the sole deposition of the specific compound in gaseous form.

[0111] Contacting the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface

[0112] The contacting between the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface is carried out such that the specific compound has not been removed or has been completely removed between the step of depositing said specific compound and the contacting step. In other words, for each hydrophilic silicon oxide bonding surface on which the specific compound has been deposited, the direct bonding method according to the invention does not comprise steps of cleaning and rinsing said surface between the deposition of the specific compound and the contacting of the substrates. In particular, the step of rinsing with ultrapure deionized water conventionally used to remove particles and surface contamination before bonding is limited or very preferably eliminated, so as not to remove the specific compound on the surface.

[0113] The contacting between the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface is preferably carried out at a temperature between -10°C and 60°C, even more preferably at room temperature (i.e. typically between 18°C ​​and 25°C). Temperature control is an advantageous means of controlling the adsorption of the specific compound on the surfaces to be bonded.

[0114] The contacting may comprise the application of localized pressure, so as to generate a point of contact between the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface: the bonding wave propagates from the point of contact in a few seconds over the entire bonding interface. Alternatively, the contacting may be done without applying pressure. According to this embodiment, the first substrate and the second substrate may remain against each other for a few tens of seconds until the evacuation of the air between the two substrates causes the appearance of a point of contact and the start of the propagation of the bonding wave. The vapor pressure during the contacting of the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface is preferably between 1 Pa and 10 5 Pa.

[0115] The deposition of the specific compound on at least one of the two hydrophilic silicon oxide bonding surfaces followed by bringing the two hydrophilic silicon oxide bonding surfaces into contact and maintaining the assembly resulting from said contact at room temperature (after the end of the propagation of the bonding wave), makes it possible to achieve bonding energies of the order of 1 J / m 2 at 2 J / m 2 after a few dozen hours. By comparison, such a bonding energy is only reached, without deposition of the specific compound and all other experimental parameters remaining unchanged, after several days, so that it is never actually reached because other phenomena disrupt the process. Thus, the deposition of the specific compound makes it possible to increase the bonding kinetics.

[0116] To further increase said bonding kinetics, the direct bonding method may further comprise a subsequent step of consolidation annealing of the assembly obtained after bringing the first substrate and the second substrate into contact.

[0117] The consolidation annealing may consist of applying a temperature of 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 of preferably between 15 min and 4 h, even more preferably between 15 min and 2 h. The consolidation annealing temperature is chosen according to the nature of the first substrate and the second substrate and their ability or not to withstand a given temperature, for example in the event of the presence of a weakening zone or electronic component elements in one and / or the other of the substrates.

[0118] For example, annealing at 60°C of the assembly resulting from the deposition of the specific compound and the contact between the first substrate and the second substrate makes it possible to achieve the expected bonding energy (of the order of 1 J / m 2 or 2 J / m 2) after only one hour of implementation of said annealing. Consolidation annealing therefore makes it possible to significantly increase the kinetics of condensation reactions. In addition, such an annealing temperature remains sufficiently low (less than 100 °C, preferably less than 90 °C) so as not to induce the formation of gases and bubbles causing bonding defects at the bonding interface, nor significant thermal stress (which could appear at high temperature if the substrates to be bonded have sufficiently different thermal expansion coefficients), and also remains bearable for substrates with weakened zones and / or electronic component elements.The same bonding process without deposition of the specific compound does not allow to achieve in such a short time (typically a consolidation annealing lasting less than 2 hours) and at such low temperatures (typically a consolidation annealing temperature below 100°C, preferably below 90°C) a bonding energy greater than 1 J / m. 2 . Process for transferring a layer onto a support substrate

[0119] The invention extends to a method of transferring a layer onto a support substrate.

[0120] The method of transferring a layer onto a support substrate comprises a step of providing a donor substrate comprising a first surface of hydrophilic silicon oxide and a support substrate comprising a second surface of hydrophilic silicon oxide.

[0121] The donor substrate and the support substrate are such as the first substrate and the second substrate previously described.

[0122] For example, the donor substrate and / or the support substrate comprise silicon Si, germanium Ge, indium phosphide InP, gallium arsenide AsGa, alumina AI2O3, silicon oxide SiO2, silicon nitride SiaN4, silicon carbide SiC, gallium nitride GaN, copper, titanium, nickel, LNO and / or LTO.

[0123] The donor substrate and / or the support substrate may be multilayer structures comprising at least two layers. For example, the donor substrate is a substrate referred to as a pseudo-donor substrate comprising a first layer of LTO and a second layer of silicon. For example, the support substrate is silicon.

[0124] In addition, the donor substrate and / or the support substrate may comprise one or more electronic component elements. For example, the donor substrate and / or the support substrate comprise copper connections insulated by silicon oxide portions.

[0125] Thus, the step of providing a donor substrate comprising a first hydrophilic silicon oxide surface and a support substrate comprising a second hydrophilic silicon oxide surface may comprise one or more sub-steps of arranging layers and forming electronic component elements as previously described.

[0126] As previously mentioned, the donor substrate and the support substrate respectively comprise 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 native, thermal, chemical or deposited oxide surfaces as previously described. Thus, the step of providing a donor substrate comprising a first hydrophilic silicon oxide surface and a support substrate comprising a second hydrophilic silicon oxide surface may comprise forming said native, thermal, chemical or deposited silicon oxide surfaces according to any of the previously described embodiments.

[0127] The first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface may be of the same nature (native, thermal, chemical or deposited). Alternatively, the first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface may be of different natures.

[0128] The method for transferring a layer onto a support further comprises a step of forming a weakening zone within the donor substrate so as to delimit a layer to be transferred between the first hydrophilic surface and the weakening zone. According to a preferred embodiment, the weakening zone is formed by implanting atomic species into the donor substrate, the implantation being carried out through the first hydrophilic surface. The atomic species are implanted at a determined depth, this depth fixing the thickness of the layer to be transferred. The implanted atomic species are preferably hydrogen and / or helium.

[0129] Subsequently, the method of transferring a layer onto a support substrate further comprises bonding between the donor substrate and the support substrate, the first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface being at the bonding interface and the bonding between the donor substrate and the support substrate being carried out by a direct bonding method according to any of the previously described embodiments. The provision of the specific compound may be carried out on the first hydrophilic silicon oxide surface of the donor substrate, on the second hydrophilic silicon oxide surface of the support substrate or both on the first hydrophilic silicon oxide surface of the donor substrate and on the second hydrophilic silicon oxide surface of the support substrate.

[0130] The layer transfer method finally comprises detaching the donor substrate along the weakening zone so as to transfer the layer to be transferred onto the support substrate. The detachment along the weakening zone can be triggered by a mechanical action and / or an input of thermal energy. Preferably, the detachment along the weakening zone and the consolidation annealing are combined by the application of a temperature ramp, with or without temperature steps, to stabilize the bonding interface.

[0131] Assembly comprising a first substrate and a second substrate The invention finally relates to an assembly comprising a first substrate and a second substrate, the first substrate being covered by a first surface made of hydrophilic silicon oxide and the second substrate being covered by a second surface made of hydrophilic silicon oxide, the first surface made of hydrophilic silicon oxide being bonded with the second surface made of hydrophilic silicon oxide, a specific compound being arranged between the first bonding surface made of hydrophilic silicon oxide and the second bonding surface made of hydrophilic silicon oxide, the specific compound being derived from the ammonia molecule by at least the substitution of a hydrogen atom by a hydroxyl group - OH and / or an amino group - NH2, the specific compound not comprising carbon atoms.

[0132] The first substrate, the second substrate, the first hydrophilic silicon oxide bonding surface and the second hydrophilic silicon oxide bonding surface are as previously described.

[0133] According to a particular embodiment of the assembly, the concentration of specific compound at the bonding interface between the first substrate and the second substrate is preferably between 10 11 molecules / cm 2 and 10 15 molecules / cm 2 , said concentration being able to be determined for example by mass spectroscopy assay.

[0134] Preferably, the specific compound comprises only nitrogen, oxygen and / or hydrogen atoms.

[0135] Preferably, the specific compound is not hydrazine.

[0136] Preferably again, the specific compound is chosen from hydroxylamine and hydroxylhydrazine. The presence of said compounds can be detected for example by infrared spectroscopy, by Raman spectroscopy and / or by mass spectroscopy techniques (for example by WOS according to the English acronym “Wafer Outgassing Spectroscopy” or by TDS according to the English acronym “Thermal Desorption Spectroscopy”).

[0137] The presence of the specific compound in the assembly at the bonding interface and its surface concentration can be characterized by characterization techniques well known to those skilled in the art, such as infrared absorption spectroscopy, RAMAN spectroscopy, X-ray fluorescence techniques if the specific compound comprises heavy elements or mass spectroscopy techniques by opening and then degassing the surfaces (technique known to those skilled in the art under the acronym WOS from the English term "Wafer Outgassing Spectroscopy"). Heavy elements are understood to mean elements with an atomic mass greater than or equal to that of sodium.

[0138] Example

[0139] 10mL of a hydroxylamine solution (NH2OH) is dispensed at concentrations of 10' 5 M (mol / L), 10' 3 M, or 10' 1M on a first silicon substrate 200 mm in diameter having a first bonding surface made of hydrophilic silicon oxide of thermal oxide type 100 nm thick. The system is rotated at a speed of 2000 rpm until the thickness of the hydroxylamine film is uniform. This uniformization can be conventionally observed by observing colored Newton fringes, which pass as the film thins under the combined effect of centrifugal flow and evaporation, until they disappear when the thickness of the film is below half a wavelength of visible radiation (i.e., typically less than 200 nm). Then the substrate is kept rotating for about ten additional seconds, so as to evacuate the excess aqueous hydroxylamine solution and to dry the first bonding surface made of hydrophilic silicon oxide.

[0140] A second silicon substrate of 200 mm diameter having a second bonding surface of hydrophilic silicon oxide of thermal oxide type of 100 nm thickness is provided and the same treatment as previously described for the first silicon substrate is applied.

[0141] The first hydrophilic silicon oxide bonding surface is then brought into contact with the second hydrophilic silicon oxide bonding surface at room temperature so as to obtain adhesion by direct bonding between the first substrate and the second substrate. A consolidation annealing of the newly formed structure comprising the first substrate and the second substrate is then carried out at temperatures ranging from 100°C to 500°C for a period of 2 hours.

[0142] Finally, the bonding energies obtained as a function of the temperature of said consolidation annealing are measured by the classic blade insertion method, known as the "Maszara method", in an anhydrous atmosphere. The results are shown in Figure 2 in solid triangle symbols for the surfaces exposed to hydroxylamine 10' 5 M, in solid square symbols for surfaces exposed to hydroxylamine 10' 3 M and in solid pentagon symbols for surfaces exposed to hydroxylamine 10' 1 M. It is observed that the bonding energy is greater as the concentration of the hydroxylamine solution is high. Comparative example

[0143] Exactly the same operation as in the example is carried out by replacing the hydroxylamine solutions with deionized water (DIW). The results are shown in open circle symbols in Figure 2. It is observed that the bonding energy is lower than that obtained with a hydroxylamine solution.

Claims

CLAIMS 1. Method of direct bonding between two substrates comprising the following steps: (a) providing a first substrate and a second substrate respectively comprising a first hydrophilic silicon oxide bonding surface and a second hydrophilic silicon oxide bonding surface, (b) depositing a specific compound on the first hydrophilic silicon oxide bonding surface, the specific compound being derived from the ammonia molecule by at least the substitution of a hydrogen atom by a hydroxyl group -OH and / or an amino group -NH2, the specific compound not comprising carbon atoms, (c) bringing the first hydrophilic silicon oxide bonding surface on which the specific compound has been deposited into contact with the second hydrophilic silicon oxide bonding surface, so as to obtain adhesion of the first substrate with the second substrate.

2. The method of claim 1, wherein the specific compound is not hydrazine.

3. Method according to one of claims 1 or 2, further comprising the deposition of the specific compound on the second hydrophilic silicon oxide bonding surface, the adhesion of the first substrate with the second substrate being obtained by bringing into contact the first hydrophilic silicon oxide bonding surface and said second hydrophilic silicon oxide bonding surface on which the specific compound has been previously deposited.

4. Method according to one of claims 1 to 3, in which the surface concentration of the specific compound on the first hydrophilic silicon oxide bonding surface prior to bringing the first hydrophilic silicon oxide bonding surface on which said specific compound has been deposited into contact with the second hydrophilic silicon oxide bonding surface is between 10 11 molecules / cm 2 and 10 15 molecules / cm 2 .

5. Method according to one of claims 1 to 4, in which the specific compound comprises only nitrogen, oxygen and / or hydrogen atoms.

6. Method according to one of claims 1 to 5, in which the specific compound is chosen from hydroxylamine and hydroxylhydrazine. Tl 7. Method according to one of claims 1 to 6, in which the deposition of the specific compound on the first hydrophilic silicon oxide bonding surface comprises the deposition on the first hydrophilic silicon oxide bonding surface of a liquid comprising the specific compound.

8. Method according to claim 7, in which the deposition on the first hydrophilic silicon oxide bonding surface of the liquid comprising the specific compound comprises: - depositing a volume of the liquid comprising the specific compound in the center of the first hydrophilic silicon oxide bonding surface, - spreading said volume of liquid comprising the specific compound by rotation of the first hydrophilic silicon oxide bonding surface, said first hydrophilic silicon oxide bonding surface being kept in rotation until ejection and evaporation of the volume of liquid comprising the specific compound.

9. The method of claim 8, further comprising a step of exposing the first hydrophilic silicon oxide bonding surface to a plasma prior to depositing the volume of liquid comprising the specific compound at the center of the first hydrophilic silicon oxide bonding surface.

10. Method according to one of claims 7 to 9, in which the liquid comprising the specific compound comes from the dissolution of the specific compound in a solvent, preferably in water or in a mixture of water and isopropyl alcohol (IPA).

11. Method according to one of claims 7 to 10, in which the deposition of liquid is preferably carried out at a temperature between 4°C and 28°C for a duration between 5 s and 5 min.

12. Method according to one of claims 1 to 6, wherein the deposition of the specific compound on the first hydrophilic silicon oxide bonding surface comprises exposing said first hydrophilic silicon oxide bonding surface to a gas comprising the specific compound.

13. Method according to one of claims 1 to 12, in which the first substrate and / or the second substrate are silicon substrates.

14. Method according to one of claims 1 to 13, in which the first bonding surface made of hydrophilic silicon oxide and / or the second bonding surface made of hydrophilic silicon are deposited oxide, thermal oxide, chemical oxide and / or native oxide.

15. Method according to one of claims 1 to 14, in which the contacting of the first hydrophilic silicon oxide bonding surface on which the specific compound has been deposited and the second hydrophilic silicon oxide bonding surface is carried out at a temperature between -10°C and 60°C.

16. Method according to one of claims 1 to 15, further comprising a step d) of consolidation annealing carried out after step c) of bringing into contact the first bonding surface made of hydrophilic silicon oxide on which the specific compound has been deposited and the second bonding surface made of hydrophilic silicon oxide, the consolidation annealing being preferably carried out at a temperature below 100°C, even more preferably below 90°C for a duration of between 15 min and 2 h.

17. Method according to one of claims 1 to 16, in which the first substrate is made of a first material and the second substrate is made of a second material, the difference in coefficient of thermal expansion between the first material and the second material being greater than or equal to 10% in relative value.

18. Method according to one of claims 1 to 16, in which 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, the difference in coefficient of thermal expansion between the first material and the second material being greater than or equal to 10% in relative value.

19. Method according to one of the preceding claims, in which the first substrate comprises electronic component elements.

20. Method according to one of the preceding claims, in which the first substrate comprises a weakening zone formed by implantation of atomic or ionic species.

21. A method of transferring a layer onto a support substrate, said method comprising the following steps: a) providing a donor substrate comprising a first surface of hydrophilic silicon oxide and a support substrate comprising a second surface of hydrophilic silicon oxide, b) forming a weakening zone within the donor substrate so as to delimit a layer to be transferred between the first hydrophilic silicon oxide surface and the weakening zone, c) bonding between the donor substrate and the support substrate, the first hydrophilic silicon oxide surface and the second hydrophilic silicon oxide surface being at the bonding interface and the bonding between the donor substrate and the support substrate being carried out by a bonding method according to any one of claims 1 to 19, d) detaching the donor substrate along the weakening zone so as to transfer the layer to be transferred onto the support substrate.

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