Basic molecule-assisted direct bonding method

Abstract

To provide a method for manufacturing a multilayer structure by direct bonding between two substrates.SOLUTION: A method for manufacturing a multilayer structure (100) by direct bonding between a first substrate (1) and a second substrate (2) includes the steps of: providing a first substrate (1) and a second substrate (2) respectively including a first bonding surface (3) and a second bonding surface (4); contacting the first bonding surface (3) and the second bonding surface (4) so as to form a direct bonding interface (6) between the first substrate (1) and the second substrate (2); disposing at least the direct bonding interface (6) in a basic environment; and applying a heat treatment at a temperature of 20-350°C so as to obtain the multilayer structure (100).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to the field of direct bonding. In particular, this invention relates to a method for manufacturing multilayer structures by direct bonding. [Background technology]

[0002] Direct bonding is a well-known technique and is used in industrial applications, such as the production of SOI by SOITEC or STMicroelectronics for the manufacture of imaging devices. As understood herein, direct bonding is the spontaneous bonding of two surfaces without adding material to the interface between the surfaces to be bonded, and in particular without a thick layer of liquid. Nevertheless, it is possible to have several monolayers of water adsorbed on the surfaces, with a thickness of 0.25–1.25 nm, and therefore these surfaces are dry to the naked eye.

[0003] Direct bonding is conventionally performed at ambient temperature and pressure, but this is not necessary.

[0004] A key characteristic of direct bonding lies in its adhesive energy, or the energy available to spontaneously initiate bonding. This is the energy that allows the two surfaces to deform so that they come into contact at an atomic scale, thus enabling van der Waals forces. This adhesive energy partially refers to the propagation time of the bonding wave (l'onde de collage), which conventionally propagates in 9 seconds for the direct bonding of two 200 mm silicon substrates. For example, for two surfaces of silicon or hydrophilic silicon oxide, the adhesive energy is typically 30–100 mJ / m 2 That is the case.

[0005] Another important characteristic of direct bonding is its bonding energy, or, in other words, bonding energy. This is the energy required to separate the two bonding surfaces. In the context of bonding two silicon substrates covered with a thermal oxide of approximately 145 nm, this bonding energy is typically 0.14–6 J / m 2 That is the case.

[0006] To achieve spontaneous bonding, the surface is generally cleaned of organic and particulate contaminants that are detrimental to direct bonding. For example, the bonding surface is pre-cleaned using a caro-acid-based solution obtained with a mixture of 96% sulfuric acid and 30% hydrogen peroxide (3:1) at 180°C, and SC1 (a mixture of 30% ammonia, 30% hydrogen peroxide, and deionized water (1:1:5)) at 70°C. Alternatively, other highly oxidizing cleaning solutions, such as aqueous solutions containing ozone or others, may be used after treatment with UV light in the presence of gaseous ozone. The adhesive energy of an SiO2-SiO2 bond (e.g., two silicon substrates covered with approximately 145 nm of thermal oxide) chemically cleaned in a cleanroom using caro and SC1 at 70°C is approximately 140 mJ / m immediately after bonding, without heat treatment. 2 That is the case.

[0007] Bonding energy also increases with heat treatment applied after bonding at ambient temperature. Bonding energy increases as a function of the heat treatment temperature. For example, the SiO2-SiO2 bonding energy is 3 J / m at 500°C, depending on the surface treatment. 2 It rises slowly until it reaches a certain temperature, and then does not rise further than 800°C.

[0008] To further increase the bonding energy, another solution involves plasma treatment before contact. In nitrogen (N2) plasma for oxide-oxide bonding, the bonding energy is approximately 5 J / m at a treatment temperature of 300°C. 2 It increases rapidly. [Overview of the project]

[0009] However, the use of plasma may not be applicable to certain substrates, and / or its use may make industrialization more difficult due to the increased time and / or cost of the method. Plasma treatment also modifies surfaces over a thickness of several nanometers (1-10 nm). This modification can affect future devices. For example, on silicon sheets, plasma can create oxide layers that are difficult to control in terms of thickness and quality. On silicon oxide surfaces, certain plasmas, such as N2 plasma, can cause interfacial charge problems that could interfere with the electrical operation of future devices.

[0010] Patent document FR1912269 also shows that exposing the Si and / or SiO2 surfaces to specific molecules containing hydrophilic and basic functional groups before bringing the two surfaces into contact during the direct bonding method, after heat treatment in the range of 100 to 500°C, resulted in a significant increase in the bonding energy of the bonded assemblies. Pre-bonding surface exposure can be performed by a liquid or gaseous process.

[0011] One of the objectives of the present invention is to propose a direct bonding method that is easy to implement and overcomes the aforementioned drawbacks. To this end, the present invention proposes a method for manufacturing a multilayer structure by direct bonding between a first substrate and a second substrate, the method comprising the following steps: a) To provide a first substrate and a second substrate, each including a first bonding surface and a second bonding surface, b) In order to form a direct bonding interface between the first substrate and the second substrate, the first bonding surface and the second bonding surface are brought into contact. c) At least the direct bonding interface is placed in a basic environment. d) To obtain the multilayer structure, heat treatment is performed at a temperature of 20 to 1000°C, particularly 100 to 500°C, for example, 150 to 250°C.

[0012] This direct bonding method allows for the creation of multilayer structures with greater bonding energy than those obtained by a direct bonding method that omits step c) of treatment in a basic environment. This high bonding energy can be achieved at low temperatures, i.e., temperatures below 1000°C, preferably below 500°C, and more preferably at 200°C.

[0013] These bonding temperatures are suitable for many applications and / or many substrates, and the required thermal balance is small due to their properties and / or the presence of electronic and / or optoelectronic components. Furthermore, this method is applicable to many materials and is inexpensive. This method results in a multilayer structure with good mechanical strength after bonding and is compatible with subsequent methods such as Smart Cut® and / or any method that generates mechanical stress on the assembly, such as mechanical thinning. Moreover, since the use of a basic environment is performed only after the surfaces are in direct contact, this method does not affect the bonding energy. For example, the bonding wave always propagates within 9 seconds for a silicon substrate of approximately 200 mm.

[0014] The heat treatment after joining is also known to those skilled in the art as "join annealing."

[0015] According to one possibility, the heat treatment in step d) is carried out by raising the temperature from the ambient temperature to the final temperature, with the temperature rise being, for example, 0.1 to 10°C / min, more specifically 0.5 to 5°C / min, over several hours, for example, 2 hours, until the final temperature of 200 to 300°C is reached.

[0016] According to one possibility, step c), which places the direct bonding interface in a basic environment, takes approximately 1 hour to 80 days. The time of this step increases with the diameters of the first and second substrates. In fact, basic molecules in the environment of step c) need time to move across the entire direct bonding interface in order to obtain a uniform and homogeneous bonding energy. Also, the larger the diameter of the multilayer structure, the longer the time of step c).

[0017] According to one configuration, the first and / or second bonding surfaces are formed, at least in part, by a hydrophilic film composed of a material selected from natural oxide, thermal or deposited silicon oxide, silicon nitride, copper oxide, and combinations of these materials.

[0018] Typically, the hydrophilic film of copper oxide is a hybrid film composed of copper pads separated by SiO2. The copper pads are covered with native copper oxide almost instantaneously in air.

[0019] When the hydrophilic film is composed of an oxide, it is formed, for example, by a deposited oxide, a thin oxide film obtained by heat treatment (also called a thermal oxide) and / or a thin oxide film obtained by chemical treatment (also called a native or chemical oxide).

[0020] According to one variant, the first and / or second substrates are composed of an oxidizing material such as alumina, which is an essentially hydrophilic material, so the first and / or second bonding surfaces are formed by the respective materials of the first and / or second substrates. This does not exclude the presence of an additional hydrophilic film.

[0021] According to a particular example, the first bonding surface is hydrophobic (e.g., composed of a hydrophobic silicon obtained by passivation of the silicon surface and hydrogen grafting onto silicon), and the second bonding surface is hydrophilic. The second bonding surface is formed, at least in part, by a hydrophilic film selected from native oxide (such as silicon, AsGa, InP, etc. depending on the material of the second substrate), thermal oxide (of silicon), deposited oxide, silicon nitride, copper oxide, and combinations of these compounds, or the second bonding surface is composed of the material of the second substrate, which is an oxide and thus hydrophilic. By bringing the second hydrophilic surface into contact with the hydrophobic surface, the initial hydrophobic property of the latter changes to a hydrophilic property, thereby enabling direct bonding.

[0022] Specifically, the first and second bonding surfaces are generally flat. In other words, the first and second bonding surfaces lack any recesses or patterns that form a plate on a microscopic scale.

[0023] The first and / or second bonding surfaces have a roughness of the order of 1 angstrom RMS, typically less than 5 angstroms RMS.

[0024] The first bonding surface and / or the second bonding surface have a peak-to-valley roughness of less than 5 nm.

[0025] According to one possibility, the first and second substrates have a diameter of exactly more than 2.5 cm.

[0026] Advantageously, step a) further includes drying the first and second bonding surfaces before performing step b) of contact. After drying, the first and second bonding surfaces each have a surface in which at most 1 to 5 single atomic layers of H2O remain, such that the first and second bonding surfaces are dried on a macroscopic scale.

[0027] Specifically, the basic environment is a basic aqueous solution. Step c) also includes immersing at least the direct bonding interface in the basic aqueous solution. In other words, the multilayer assembly obtained in step b) is immersed whole or partially in the basic aqueous solution, insofar as the direct bonding interface is immersed in the basic solution.

[0028] According to one configuration, the pH of the basic aqueous solution is strictly above 7.5, particularly above 8, and for example above 9.

[0029] According to one possibility, a basic aqueous solution is formed by dissolving a basic compound selected from NaOH, KOH, Na2CO3, NH4OH, amino alcohols, and mixtures thereof in deionized water, wherein the amino alcohol is particularly dimethylaminoethanol (or DMAE, CAS: 108-01-0), N,N-diethyl-2-aminoethanol (or DEAE, CAS: 100-37-8), monoethanolamine (CAS: 141-43-5), N-methyl The amino alcohols are selected from diethanolamine (or MDEA, CAS: 105-59-9), aminomethanol (CAS: 3088-27-5), N-methylhydroxylamine (CAS: 593-77-1), diethanolamine (or DEA, CAS: 111-42-2), dimethanolamine (CAS: 7487-32-3), triethanolamine (CAS: 102-71-6), trimethanolamine (CAS: 14002-32-5), and mixtures thereof.

[0030] According to one characteristic, a basic solution has a molar concentration of basic compounds of 10 -7 ~5 mol / l, for example 10 -6 The concentration is approximately 1 mol / l, particularly 0.01-0.5 mol / l. A small amount of base is sufficient to ensure a strong bond, which can make the step inexpensive. Of course, higher molar concentrations are possible, but this does not necessarily result in better results.

[0031] According to another embodiment, the basic environment is an atmosphere saturated with basic molecules in the gas phase by evaporation of a basic stock solution in a sealed container, which comprises deionized water and a basic compound selected from N,N-diethylethanolamine, N,N-dimethylethanolamine, 2-aminoethanol, N-methyldiethanolamine, aminomethanol, N-methylhydroxylamine, diethanolamine, dimethanolamine, triethanolamine, trimethanolamine, ethanolamine, diethyl-NN-ethanol, ammonia, and mixtures thereof.

[0032] According to one possibility, the basic stock solution contains an amino alcohol with a molar concentration of 10 -7 ~5 mol / l dissolved in deionized water. In order to obtain a gaseous environment saturated with gaseous amino alcohol, the basic stock solution is placed in a hermetically sealed body for 1 hour. Then, the multilayer assembly obtained in step b) is placed in the hermetically sealed body in order to expose the direct bonding interface to an atmosphere saturated with basic molecules in the gas phase.

[0033] According to one configuration, the temperature of the heat treatment performed in step d) is 20~1000 °C, particularly 100~500 °C, particularly 150~250 °C.

[0034] According to one possibility, the first substrate and the second substrate are each formed of a material independently selected from semiconductors such as Si, Ge, InP, AsGa, SiC, GaN; LNO (acronym for lanthanum nickel oxide LaNiO3), LTO (acronym for lithium titanate Li2TiO3), and combinations thereof.

[0035] The first and second substrates may have the same properties or different properties.

[0036] According to a specific embodiment, the first substrate and the second substrate provided in step a) each include a silicon substrate having a diameter of 25~300 mm, for example 100~300 mm, particularly 200 mm or 300 mm, and the first bonding surface and the second bonding surface are each formed of a silicon oxide film. Step c) includes placing the direct bonding interface obtained in step b) in a basic environment for 21~40 days, particularly 30 days, and the basic environment is a basic aqueous solution formed by dissolving NaOH and having a molar concentration of 10 -7 ~0.01 mol / l, particularly about 10 -3 mol / l. Step d) includes performing a heat treatment at about 300 °C in order to obtain a direct bond between the first substrate and the second substrate having a bonding energy exceeding 5 J / m 2 .

[0037] The junction energy is measured by a double lever method with forced displacement in an anhydrous atmosphere, as described, for example, in the paper by F. Fournel, L. Continni, C. Morales, J. Da Fonseca, H. Moriceau, F. Rieutord, A. Barthelemy, and I. Radu, Journal of Applied Physics 111, 104907 (2012).

[0038] According to one modified embodiment, the first substrate provided in step a) includes one or more first vignettes derived from vignetage of the first substrate in order to obtain direct bonding of one or more first vignettes to the second substrate.

[0039] The first bonding surface is defined by the exposed surfaces of one or more first bonding layers.

[0040] In another modified example, the second substrate given in step a) includes one or more second bonding layers derived from the bonding layer formation of the second substrate in order to obtain a direct bond between one or more first bonding layers and one or more second bonding layers.

[0041] The second bonding surface is defined by the exposed portions of one or more second bonding layers.

[0042] According to another feature, the method for manufacturing a multilayer structure according to the present invention includes one or more of the following features, which may be considered individually or in combination: - The first and / or second substrates have a thickness greater than 50 micrometers, preferably greater than 100 micrometers, for example, about 725 micrometers. The first and / or second substrates may be sufficiently thick to be self-supporting.

[0043] - The first and second substrates are laminates of at least two layers of materials with different properties.

[0044] - The first and second bonding surfaces of the first and second substrates, respectively, are each formed at least partially by a hydrophilic film of native oxide, silicon oxide, silicon nitride, copper oxide, or a combination thereof.

[0045] - The first and / or second bonding surfaces of the first and second substrates are completely formed by a continuous hydrophilic film of native oxide, silicon oxide, silicon nitride, or copper oxide, respectively.

[0046] - Before contact, only the first or second bonding surface is hydrophilic.

[0047] - The first substrate and / or the second substrate each include recesses that open to the first and / or second bonding surfaces.

[0048] - The first and second bonding surfaces do not contain any material added prior to contact in step b).

[0049] - This method includes a step of plasma treatment on the bonding surfaces of the first and second substrates prior to step b) bringing the bonding surfaces into contact. Thus, it is possible to substantially reduce the temperature of the heat balance while maintaining a large bonding energy.

[0050] - Drying of the first and second bonding surfaces includes, in particular, centrifugal separation of the first and second substrates at 2000 revolutions per minute for 45 seconds.

[0051] - Drying of the first and second bonding surfaces includes drying using the Marangoni effect.

[0052] - The first and / or second bonding surfaces are washed with ozonated water before step b).

[0053] - The first and / or second joint surfaces are cleaned by the SC1 treatment and / or the SC2 treatment prior to step b).

[0054] - Contact in step b) is preferably carried out in an atmosphere with a relative humidity of about 75% or lower, or under reduced pressure (<5.10 -2 The test is performed at room temperature in millibars or under an anhydrous atmosphere (<0.5 ppm).

[0055] - The first and second substrates given in step a) each comprise a silicon substrate having a diameter of 50 to 300 mm, for example, 100 to 200 mm, and the first and second bonding surfaces are each formed by a silicon oxide film, and step c) comprises placing the direct bonding interface obtained in step b) in a basic environment for 1 to 40 days, the basic environment being particularly characterized by a molar concentration of 10 -7 ~5 mol / l, especially 10 -7 ~10 -2 mol / L, for example 10 -3 The solution is a basic aqueous solution of mol / l NaOH, and in step d), the bonding energy between the first substrate and the second substrate is 5 J / m 2 This includes heat treatment at 300°C to obtain a direct bond exceeding [a certain value].

[0056] - The first and second substrates have a diameter of 50 mm, and the time for step c) is approximately 1 to 2 days.

[0057] - The first and second substrates have a diameter of 100 mm, and the time for step c) is approximately 4 to 6 days.

[0058] - The first and second substrates have a diameter of 200 mm, and the time for step c) is approximately 15-20 days.

[0059] - Step c) of locating at least a direct bonding interface is carried out in a basic environment, at atmospheric pressure, at a temperature between 100°C from the ambient temperature, for example, about 50-60°C.

[0060] - The first and second substrates have a diameter of 300 mm, and the time for step c) is approximately 35-40 days.

[0061] - Step d), which involves heat treatment, is performed in conjunction with step c).

[0062] - Step d), which involves heat treatment, is performed during the execution of step c), but for a shorter period of time than step c).

[0063] Other aspects, purposes, and advantages of the present invention will become more apparent from the following description of some modified embodiments thereof, given as non-limiting examples and with reference to the accompanying drawings. For the remainder of the description, identical, similar, or equivalent elements in different embodiments are given the same reference numerals for simplicity. The drawings do not necessarily adhere to the scale of all elements shown in order to improve their readability. [Brief explanation of the drawing]

[0064] [Figure 1] Figure 1 is a schematic diagram showing steps a) and b) of the method according to the first embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram showing step c) of the method according to the first embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram showing step d) of the method according to the first embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram showing steps a) and b) of the method according to the second embodiment of the present invention. [Figure 5] Figure 5 is a schematic diagram showing step c) of the method according to the second embodiment of the present invention. [Figure 6] Figure 6 is a schematic diagram showing step d) of the method according to the second embodiment of the present invention. [Figure 7] Figure 7 is a schematic diagram showing step c) of a modified example of the present invention. [Modes for carrying out the invention]

[0065] As shown in Figures 1-3, the direct bonding method of the present invention includes the steps of bringing a first substrate 1 and a second substrate 2 into contact (steps a and b in Figure 1), placing them in a basic environment, i.e., a basic aqueous solution 8 with a pH strictly above 7.5 (step c in Figure 2), and a bonding annealing heat treatment step (step d in Figure 3) to obtain a multilayer structure 100 having a bonding energy exceeding that which can be obtained without performing step c) of placing them in a basic environment. The first and second substrates 1 and 2 are made of silicon and have a diameter of 200 mm and a thickness of 725 micrometers. These two substrates 1 and 2 each include a first bonding surface 3 made of native silicon oxide (not shown) and a second bonding surface 4 made of thermal silicon oxide (a hydrophilic oxide film 5 with a thickness of 145 nm). The first and second surfaces 3 and 4 are prepared before contact by washing with ozonated water, SC1 (a mixture of 30% ammonia, 30% hydrogen peroxide, and deionized water in a volume ratio of 1:1:5), followed by SC2 (a mixture of 30% hydrochloric acid, 30% hydrogen peroxide, and water in a volume ratio of 1:1:5). These washings allow for the removal of organic and particulate contaminants that would be a major obstacle in direct bonding. In a modified example not shown, the step of preparing the surfaces before contact includes conventional plasma treatment.

[0066] Then, the first and second bonding surfaces 3 and 4 are brought into contact for spontaneous direct bonding (step b). The direct bonding interface 6 of the multilayer assembly 7 thus obtained is in deionized water with a molar concentration of approximately 10 -3 It is placed in a basic environment consisting of a mol / l basic aqueous solution of NaOH (step c).

[0067] The immersion of the multilayer assembly 7 in the basic aqueous solution 8 is maintained for 30 days, at which point the multilayer assembly 7 is subjected to bonding annealing heat treatment at 300°C (step d - temperature increase from ambient temperature to 300°C at 1°C / min for 2 hours). Measurement of the bonding energy to the resulting multilayer structure 100 shows that it results in the fracture of the silicon substrates 1,2 without delamination of the substrates 1,2. This indicates that the obtained bonding energy is 5 J / m, which is the fracture energy of silicon. 2 This indicates that it is greater than step c) immersion in a basic environment. The same method, performed without step c), yields 4 J / m after annealing at 500°C. 2 This results in junction energy.

[0068] In an alternative embodiment not shown, one of the two substrates 1, 2 given in step a) has a fragile surface. The bonding annealing heat treatment contributes to a heat balance that enables fracture at the fragile surface. The resulting multilayer structure 100 includes one of the two substrates 1, 2 bonded to a transferred thin layer resulting from the fracture, and the negative of the other substrate 1, 2.

[0069] In a modified example not shown, the immersion time of the direct bonding interface 6 in a basic environment is approximately 5 hours for a substrate with a density of 25 mm / l (15 days for a substrate with a diameter of 200 mm). The immersion time is also a variable depending on the properties of the substrates 1 and 2.

[0070] As shown in Figure 4, the silicon oxide film 5 may form the bonding surfaces 3 and 4 of the first and second substrates 1 and 2. Figure 4 shows the two bonding surfaces 3 and 4 that are brought into contact to form a direct bonding interface 6. Figure 5 shows the multilayer assembly 7 obtained in step b) with a molar concentration of 10 -2Step c) of this method is shown, which involves placing the assembly in a basic environment formed by a basic aqueous solution 8 containing amino alcohol DMAE (an acronym for 2-(dimethylamino)ethanol) in a mol / l concentration. The basic environment 8 covers the level of the direct bonding interface 6, and the immersion is maintained for 20 days. Then, according to step d) of this method, the multilayer assembly 7 is subjected to bonding strengthening heat treatment at 200°C for 3 hours.

[0071] These operations are performed at any point on the direct bonding interface 6, in particular at 5 J / m 2 This makes it possible to obtain a strengthening bonding energy exceeding (a value obtained by observing the fracture of silicon during the implementation of the double lever method). If the same direct bonding method is performed without step c), the first and second substrates may separate when the double lever method is implemented.

[0072] According to the modified embodiment shown in Figure 7, the assembly 7 obtained in step b) is placed in a basic environment formed by an atmosphere saturated with basic molecules in the gas phase 8'. For this purpose, the method is used with a concentration of 10 -4 A basic stock solution 11 of mol / l ethanolamine is evaporated for 1 hour to prepare a gas-sealed inclusion 9 saturated with basic molecules in the gas phase. The assembly is then placed inside the inclusion 9 for twice the length of immersion (step c). After the direct bonding interface 6 is immersed in this atmosphere saturated with basic molecules in the gas phase 8', the assembly 7 is heat-treated at 300°C for 2 hours (step d) to enhance the bonding energy. Finally, the bonding energy, measured by the double lever method, is 5 J / m 2 Larger.

[0073] According to another possibility not shown in the diagram, the two bonding surfaces 3 and 4 are plasma treated before contact according to step b) of the present method, and the thermal annealing according to step d) is carried out at a temperature of approximately 20 to 250°C, for example 50°C, for several hours.

[0074] In a modified example not shown, the first and / or second substrates 1 and 2 are composed of materials selected from Ge, InP, AsGa, SiC, and GaN, and these have bonding surfaces composed of hydrophilic films such as native oxides of the possible materials, LNO, and LTO, which have essentially hydrophilic bonding surfaces.

[0075] According to yet another modification (not shown), the first substrate 1 given in step a) is formed in several first bonding layers, the exposed surface of which is the first bonding surface 3. The first bonding layers are bonded to the second substrate 2 (full plate) in accordance with the method described above, in accordance with a chip-plate bonding, also known as "chip-to-wafer" bonding. According to yet another modification (not shown), the second substrate 2 is also formed in several second bonding layers, and the method according to the present invention enables direct bonding of the first bonding layer and the second bonding layer.

[0076] In an alternative configuration not shown, the first bonding surface 3 and the second bonding surface 4 are prepared to have a bondable hybrid surface of copper oxide in direct bonding. These first and second hydrophilic bonding surfaces 3,4 are typically composed of copper pads having sides of 2.5 micrometers separated by 2.5 micrometers of SiO2, and are referred to as a hybrid surface having a "pitch" of 5 micrometers. Then, steps b) to d) of the present method are reproduced as described above.

[0077] Therefore, the present invention proposes a method for manufacturing a multilayer structure 100, which involves direct bonding between two substrates 1 and 2 having high bonding energy, and which allows for limiting the temperature of post-bonding thermal annealing. Preparation of the basic environment is inexpensive, and immersion step c) is applicable to many materials. In particular, it is possible to bond substrates (or thick layers) of materials with significant differences in thermal expansion coefficients. Furthermore, if the materials of the first and second substrates 1 and 2 include devices, they will not be damaged by the operating temperature.

[0078] Needless to say, the present invention is not limited to the modified embodiments described above, but includes all technically equivalents and variations of the described method, as well as combinations thereof.

Claims

1. A method for producing a multilayer structure (100) by direct bonding between a first substrate (1) and a second substrate (2), comprising: a) providing a first substrate (1) and a second substrate (2) comprising a first joining surface (3) and a second joining surface (4), respectively; b) contacting the first bonding surface (3) and the second bonding surface (4) to form a direct bonding interface (6) between the first substrate (1) and the second substrate (2); c) placing at least said direct bond interface (6) in a basic environment; d) heat treatment at a temperature of 20 to 1000 ° C. to obtain the multilayer structure (100); A manufacturing method comprising:

2. The method of claim 1, wherein step c) of placing the direct bond interface (6) in the basic environment is performed for about 1 hour to 80 days.

3. The manufacturing method according to claim 1 or 2, 10. A method for manufacturing a substrate, wherein the first joining surface (3) and / or the second joining surface (4) are at least partially formed by a hydrophilic film (5) made of a material selected from native oxides, thermal or deposited silicon oxides, silicon nitrides, copper oxides and combinations of these materials.

4. 3. The manufacturing method according to claim 1 or 2, wherein the first joining surface (3) and the second joining surface (4) are completely flat.

5. 3. The method of claim 1, wherein the basic environment is a basic aqueous solution (8).

6. The manufacturing method according to claim 5, The basic aqueous solution (8) is a solution of NaOH, KOH, Na ２ CO ３ , N.H. ４ OH, amino alcohols and mixtures of these basic compounds, said amino alcohols being selected in particular from 2-(dimethylamino)ethanol DMAE, N,N-diethyl-2-amino-ethanol, monoethanolamine, N-methyldiethanolamine, aminomethanol, N-methylhydroxylamine, diethanolamine, dimethanolamine, triethanolamine, trimethanolamine and mixtures of these amino alcohols.

7. The basic aqueous solution (8) has a molar concentration of the basic compound of 10 －７ ~5 mol / l, for example 10 －６ The process according to claim 5, wherein the concentration is from 0.01 to 0.5 mol / l.

8. The manufacturing method according to claim 1 or 2, The basic environment is an atmosphere saturated with basic molecules in a gas phase (8') by evaporation of a basic stock solution (11) in an airtight container (9), the basic environment comprising deionized water and a basic compound selected from N,N-diethylethanolamine, dimethylaminoethanol, aminoethanol, N-methyldiethanolamine, aminomethanol, N-methylhydroxylamine, diethanolamine, dimethanolamine, triethanolamine, trimethanolamine, ethanolamine, diethyl-N,N-ethanol, ammonia, and combinations thereof.

9. The manufacturing method according to claim 1 or 2, The manufacturing method, wherein the first substrate (1) and the second substrate (2) are each formed of a material selected from semiconductors such as Si, Ge, InP, AsGa, SiC, and GaN, LNO, LTO, and combinations thereof.

10. The manufacturing method according to claim 1 or 2, The first substrate (1) and the second substrate (2) provided in step a) each comprise a silicon substrate having a diameter of 25 to 300 mm, particularly 200 mm or 300 mm, and the first bonding surface (3) and the second bonding surface (4) each are completely formed by a continuous hydrophilic film (5) made of silicon oxide; The step c) comprises placing the directly bonded interface (6) obtained in the step b) in the basic environment for 21 to 40 days, the basic environment being formed by dissolving NaOH with a molar concentration of 10 －７ ~0.01 mol / l, for example, about 10 －３ mol / l of a basic aqueous solution (8), The step d) is 5 J / m ２ a heat treatment at about 300°C to obtain a direct bond between a first substrate (1) and a second substrate (2) having a bond energy exceeding 1000 kJ / cm.

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