Method for bonding two hydrophilic surfaces

Abstract

The direct bonding method comprises the following steps: - supplying a first substrate (10) and a second substrate (20), wherein the first substrate (10) is covered by a first hydrophilic surface (11) and the second substrate (20) is covered by a second hydrophilic surface (21); - depositing a specific molecule on the first hydrophilic surface (11) and / or the second hydrophilic surface (21), wherein the specific molecule (30) comprises a hydrophilic functional group and a basic functional group separated by at least one atom; - bringing the first hydrophilic surface (11) into contact with the second hydrophilic surface (21), whereby the two hydrophilic surfaces (11, 21) are bonded to each other and the first substrate (10) and the second substrate (20) are assembled; - optionally, applying a bonding annealing heat treatment, preferably at a temperature lower than or equal to 500°C.

Description

[Technical field]

[0001] The present invention relates to a method for the direct bonding of two hydrophilic surfaces, and also to a component obtained using such a method.

[0002] The present invention is applicable to many industrial fields, for example, in particular in the manufacture of silicon-on-insulator (SOI) or in the production of imagers.

[0003] The invention is particularly interesting because it makes it possible to obtain components with good mechanical resistance for low thermal annealing budgets after bonding.

[0004] [Prior Art]

[0005] Direct bonding is a spontaneous bonding between two surfaces, without the addition of any material and in particular without the addition of thick layers consisting of liquid materials or polymers. However, there may be some single-layers of water adsorbed on the surfaces to be bonded, especially if they are hydrophilic but the latter are visually dry. Direct bonding is traditionally carried out at ambient temperature and ambient pressure, but this is not an obligation. For SiO2-SiO2 bonding, the surfaces to be bonded are usually cleaned beforehand using solutions with Caro acid base obtained using a mixture of sulfuric acid 96% and oxygenated water 30% (3:1) at 180°C and SC1 [a mixture of ammonia 30%, oxygenated water 30% and deionized water (1:1:5)] at 70°C. These cleanings make it possible to remove organic and particulate contaminations that are highly detrimental to direct bonding. Alternatively, it is possible to use other highly oxidizing cleaning solutions such as, for example, aqueous solutions containing ozone, or to employ treatment using UV light exposure in the presence of gaseous ozone.

[0006] Direct bonding can be characterized by:

[0007] - bonding energy (also called adhesion energy): This is the energy required to separate two surfaces being bonded; the bonding energy varies according to the thermal annealing applied after the bonding.

[0008] - Adhesion energy: This is the energy available for spontaneous bonding. This is the energy that makes it possible to deform the two surfaces so that they come into contact at the atomic scale with the help of van der Waals forces.

[0009] For example, for two surfaces composed of hydrophilic silicon oxide or silicon, the adhesion energy typically ranges from 30 to 100 mJ / m 2 In a clean room environment, the adhesion energy of SiO2-SiO2 without annealing was about 140 mJ / m just after bonding by using alkaline chemical cleaning of Carroll and SC1 at 70°C. 2 For bonding, the adhesion energy increases with the temperature of the thermal annealing. For example, the binding energy rises slowly and reaches 3 J / m at 500°C. 2 Connect and stagnate until 800℃( Figure 1 ).

[0010] In order to increase the binding energy, one solution consists of performing plasma treatment. Figure 1 As shown in FIG. 1 , using nitrogen plasma (N2), for oxide-oxide bonding, the binding energy rises rapidly to 5 J / m for an annealing temperature of 300°C. 2 .

[0011] However, the use of plasma may be incompatible with certain substrates and / or its use prolongs the time and / or cost of the process, which makes them less amenable to industrialization. Plasma treatment also modifies the surface over a thickness of a few nanometers (between 1 and 10 nm). This modification may disrupt future devices. For example, with silicon substrates, the plasma produces an oxide layer that is difficult to control in thickness and quality. With silicon oxide surfaces, certain plasmas (such as N2 plasma) produce interfacial charges that may disrupt electrical manipulation of future components. [Summary of the invention]

[0012] Disclosure of the Invention

[0013] The object of the present invention is to overcome the drawbacks of the prior art and to propose a method for bonding which makes it possible to obtain a strong binding energy at low temperatures, typically lower than or equal to 500° C. and preferably lower than or equal to 300° C., without using plasma treatment.

[0014] To this end, the present invention proposes a method for directly bonding two substrates, which comprises the following steps:

[0015] - supplying a first substrate and a second substrate, the first substrate being covered by a first hydrophilic surface and the second substrate being covered by a second hydrophilic surface,

[0016] - deposition of a specific molecule on the first hydrophilic surface of the first substrate and / or the second hydrophilic surface of the second substrate, the specific molecule comprising a hydrophilic functional group and a basic functional group separated by at least one atom,

[0017] - bringing the first hydrophilic surface into contact with the second hydrophilic surface, so that the first substrate and the second substrate are assembled by bonding the first hydrophilic surface and the second hydrophilic surface,

[0018] - Optionally, the application of a bonding annealing heat treatment, preferably at a temperature lower than or equal to 500°C, and even more preferably lower than or equal to 300°C.

[0019] The present invention is essentially distinguished from the prior art by the use of a specific molecule comprising a hydrophilic functional group and a basic functional group. The hydrophilic functional group allows the specific molecule to be easily chemically adsorbed onto the hydrophilic surface to be bound. The basic functional group makes it possible to increase the pH of the adsorbed monolayer of water. The presence of this molecule substantially increases the binding energy obtained.

[0020] "Hydrophilic surface" means a surface on which at least one monolayer of water is adsorbed at ambient pressure (i.e. about 1 bar) in air having a relative humidity of at least 1%. A surface is said to be hydrophilic if the angle of a water droplet is less than 90° and preferably less than 50°, and even more preferably less than 5°.

[0021] Preferably, the first hydrophilic surface and the second hydrophilic surface are made of oxide. This can be a thin layer consisting of a deposited oxide, a thin layer consisting of an oxide obtained by a thermal treatment (also called thermal oxide) and / or a thin layer consisting of an oxide obtained by a chemical treatment (also called native oxide or chemical oxide).

[0022] According to a first advantageous alternative embodiment, the specific molecule completely covers the first hydrophilic surface of the first substrate and / or the second hydrophilic surface of the second substrate. Advantageously, there are from 1 to 5 layers of specific molecules on the hydrophilic surface. Advantageously, there is only one monolayer.

[0023] According to a second advantageous alternative embodiment, the specific molecule covers from 0.05% to 10% (and preferably from 0.05% to 1%) of the first hydrophilic surface of the first substrate and / or the second hydrophilic surface of the second substrate.

[0024] According to a first advantageous alternative embodiment, the specific molecule is deposited in liquid form.

[0025] According to a second advantageous alternative embodiment, the specific molecule is deposited in gaseous form.

[0026] Advantageously, the hydrophilic functional group of the particular molecule is an alcohol and / or the basic functional group is a primary, secondary or tertiary amine.

[0027] Advantageously, the molar mass of this particular molecule is lower than or equal to 500 g / mole and preferably lower than or equal to 200 g / mole.

[0028] Advantageously, the first substrate and / or the second substrate is a silicon substrate. The substrate or substrates are covered with a thin layer of silicon oxide. The oxide layer may be a deposited layer, a thermal oxide layer or a natural oxide layer.

[0029] This method for joining has many advantages:

[0030] - the surface preparation is carried out with the specific molecule in liquid or gaseous form: the process is simple to implement and can therefore be easily industrialized,

[0031] – A small amount of a specific molecule is sufficient to ensure a strong bond,

[0032] – The method can be applied to many materials and is inexpensive,

[0033] – The use of this molecule will not increase the adhesion energy,

[0034] – No bubble formation, delamination and / or defects at the bonding interface, even after heat treatment,

[0035] – the junction temperature is compatible with many applications and / or many substrates whose nature and / or presence of electronic and / or optoelectronic components require low thermal budgets,

[0036] - The method results in an assembled structure that has good mechanical resistance after joining and is compatible with subsequent methods such as Smart Cut and / or any method that generates mechanical stress on the component (such as, for example, a mechanical thinning).

[0037] The present invention also relates to a component comprising a first substrate and a second substrate, wherein the first substrate is covered by a first hydrophilic surface, and the second substrate is covered by a second hydrophilic surface, and a specific molecule is arranged between the first hydrophilic surface of the first substrate and the second hydrophilic surface of the second substrate, and the specific molecule comprises a hydrophilic functional group and a basic functional group, and the two functional groups of the specific molecule are separated by at least one atom.

[0038] Advantageously, the hydrophilic function of the particular molecule is an alcohol function and / or the basic function is a primary, secondary or tertiary amine.

[0039] Other features and advantages of the present invention will appear from the following supplementary description.

[0040] It goes without saying that this supplementary explanation is provided merely for the purpose of illustrating the purpose of the present invention and should not be construed as a limitation to this purpose in any case.

Brief Description of the Drawings

[0041] The invention will be better understood when reading the description of specific examples given for information purposes only and in a non-limiting manner, with reference to the accompanying drawings, in which:

[0042] Figure 1 (described above) is a graph showing the binding energy according to the temperature of thermal annealing performed after direct bonding with or without plasma activation according to the prior art, each thermal annealing lasting about 2 hours;

[0043] Figure 2 Schematically showing (as a cross-sectional view) two substrates to be assembled by direct bonding, one of the substrates being covered with specific molecules according to a specific embodiment of the invention;

[0044] Figure 3 is a graph showing binding energy according to thermal annealing, which is performed after bonding [according to a specific embodiment of the present invention, when the surface of the oxide layer of one of the substrates is saturated with specific molecules];

[0045] Figure 4 is a graph showing binding energy according to thermal annealing, which is performed after bonding (according to a specific embodiment of the present invention, when the surface of the oxide layer of one of the substrates is partially covered with specific molecules);

[0046] Figure 5 is a graph of binding energy according to thermal annealing performed after bonding (according to a specific embodiment of the present invention, for different volume dilutions of a specific molecular solution);

[0047] Figure 6 An image obtained by scanning acoustic microscopy (SAM) showing the implementation of specific molecular bonding (after thermal annealing at 800° C. according to a specific embodiment of the invention).

[0048] To make the figure more legible, the different parts shown in the figure are not necessarily shown according to an equal scale.

[0049] The various possibilities (alternatives and embodiments) must be understood as not being mutually exclusive and as being combinable.

[0050] Furthermore, in the following description, terms that rely on the orientation of a structure [such as "on", "under", etc.] are applied by considering that the structure is positioned in the way shown in the figure.

[0051] [Implementation Method]

[0052] Detailed disclosure of specific examples

[0053] Although this is by no means a limitation, the present invention has particular application in the field of SOI manufacturing and imagers.

[0054] The method is a method for direct bonding of two substrates 10 , 20 , and more particularly it is a method for direct bonding of two hydrophilic surfaces, for example with oxides.

[0055] The method comprises the following steps:

[0056] a) providing a first substrate 10 and a second substrate 20, wherein the first substrate 10 is covered by a first hydrophilic surface 11, and the second substrate 20 is covered by a second hydrophilic surface 21,

[0057] b) adding a specific molecule 30 to the first hydrophilic surface of the first substrate and / or the second hydrophilic surface of the second substrate, wherein the specific molecule comprises a hydrophilic functional group and a basic functional group, and the two functional groups of the specific molecule are separated by at least one atom,

[0058] c) The first hydrophilic surface 11 is brought into contact with the second hydrophilic surface 21 , so that the two hydrophilic surfaces 11 , 21 are bonded to each other, and the first substrate 10 and the second substrate 20 are assembled.

[0059] Each substrate 10, 20 provided in step a) comprises two main surfaces parallel to each other. At least one of the main surfaces of each substrate is covered by a hydrophilic surface 11, 21 ( Figure 2 ).

[0060] The first substrate 10 and / or the second substrate 20 may be made of silica, metal, metal alloy or semiconductor material.

[0061] Preferably, the first substrate 10 and / or the second substrate 20 are made of a material selected from Si, Ge, InP, AsGa, Al2O3, SiO2, Si3N4, SiC, GaN, LNO, LTO, Cu, Ti, Ni. The first substrate and the second substrate may have the same properties or different properties.

[0062] The first substrate 10 and the second substrate 20 are covered by hydrophilic surfaces 11 and 21 , ie, there is at least one monolayer of water adsorbed on their surfaces.

[0063] Preferably, the first substrate 10 is covered with a first oxide thin layer in such a way as to form a first hydrophilic surface, and the second substrate 20 is covered with a second oxide thin layer in such a way as to form a second hydrophilic surface.

[0064] For example, the first substrate 10 and the second substrate 20 are covered with a natural oxide layer or a thermal oxide layer.

[0065] According to a first alternative embodiment, one of the substrates may be covered with a native oxide layer and the other with a thermal oxide layer.

[0066] According to another alternative embodiment, the two substrates may be covered with a thermal oxide layer.

[0067] According to another alternative embodiment, the two substrates may be covered with a native oxide layer.

[0068] In all these alternatives, the thermal oxide layer can be replaced by a deposited layer consisting of oxide.

[0069] Advantageously, before step b), one or more pre-treatments may be carried out, for example mechanical and / or chemical. For example, for silicon and its oxides, advantageously, chemical cleaning with a base of Caro's acid {obtained using a mixture of sulfuric acid 96% and oxygenated water 30% (3:1) at 180° C. and SC1 [a mixture of ammonia 30%, oxygenated water 30% and deionized water (1:1:5)]} will be used, for example at a temperature of 70° C. Other cleanings may be considered.

[0070] The substrates 10 and 20 are preferably wafers.

[0071] During step b), the specific molecules 30 are deposited in order to improve the bonding.

[0072] The specific molecule 30 is an organic molecule. It comprises a hydrophilic functional group and a basic functional group separated by at least one atom. In other words, the two functional groups are not located on the same atom, for example, they are not located on the same carbon atom.

[0073] "Basic functional group" means that the specific molecule 30 contains a protonatable group. Preferably, the basic group is a primary amine, a secondary amine or a tertiary amine. It can also be a group derived from the ionization of an acid functional group, such as from the ionization of a functional group, for example, from the sulfonic acid SO3H to -SO3 - It is also possible for this basic functionality to have an alcoholate group (RO - ).

[0074] The hydrophilic functional group is, for example, a hydroxyl functional group, an ether, an amide, an ester or a ketone.

[0075] The hydrophilic functionality is preferably a hydroxy functionality (also known as an alcohol functionality). This may be a primary, secondary or tertiary alcohol.

[0076] Even more preferably, the hydrophilic functional group is a hydroxyl functional group and the basic functional group is a primary, secondary or tertiary amine.

[0077] The specific molecule 30 may include a plurality of acid functional groups and / or a plurality of basic functional groups.

[0078] Preferably, the molecule comprises a basic functional group and at least one hydrophilic functional group. For example, it comprises a basic functional group and one, two or three hydrophilic functional groups.

[0079] The specific molecule 30 can be cyclic or non-cyclic. Preferably, it is non-cyclic. When the molecule contains an open carbon chain, the latter can be straight chain type or branched chain type. Preferably, it contains from 1 to 10 carbon atoms and more preferably from 1 to 6 carbon atoms.

[0080] Advantageously, the molecular weight of this specific molecule 30 is lower than or equal to 500 g / mole and preferably lower than or equal to 200 g / mole. Advantageously, it is greater than 40 g / mole.

[0081] For the purpose of illustration and in a non-limiting manner, the specific molecule 30 is selected from: N,N-diethyl-2-amino-ethanol (CAS: 100-37-8), dimethylaminoethanol or DMAE (CAS: 108-01-0), diethylethanolamine or DEAE (CAS 100-37-8), monoethanolamine (CAS: 141-43-5), N-methyldiethanolamine 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) and trimethanolamine (CAS: 14002-32-5).

[0082] The specific molecule 30 can be deposited:

[0083] – located on the hydrophilic surface 11 of the first substrate 10, or

[0084] - located on the hydrophilic surface 12 of the second substrate 20, or

[0085] – located on both the hydrophilic surface 11 of the first substrate 10 and the hydrophilic surface 21 of the second substrate 20 .

[0086] The specific molecules 30 may be deposited in liquid form and / or in gaseous form.

[0087] A pure solution of a particular molecule or a dilute solution of a particular molecule may be used.

[0088] Advantageously, it is possible to add a base to the solution in order to increase the pH. For example, KOH, NaOH, Na2CO3 or NH4OH can be used.

[0089] For depositing the specific molecules 30 in liquid form, any liquid deposition technique may be used, such as deposition by coating, by spraying, by spin coating. Preferably, spin coating is used.

[0090] To deposit the specific molecule 30 in gaseous form, a substrate is placed in a sealed enclosure, where a recipient containing a solution of the specific molecule (pure or diluted) is placed. The solution is then left in the sealed reactor to evaporate.

[0091] The specific molecule 30 may completely or partially cover the surface on which it is deposited.

[0092] The amount deposited may be such that a continuous monolayer is formed on the hydrophilic surface (saturation of the surface). It is also possible to have several monolayers on the surface, for example up to 5 monolayers may be present on the surface.

[0093] "Partially" means in particular less than 50%, and preferably less than 10%. Even more preferably, the specific molecule covers less than 1% (even less than 0.1%) of the surface to be joined. Advantageously, it covers at least 0.05% of the surface to be joined. According to a particularly advantageous embodiment, it covers from 0.05% to 1% of the surface to be joined, and even more preferably from 0.05% to 0.1%.

[0094] During step c), the surfaces to be bonded (i.e. the hydrophilic surfaces 11, 21) are contacted, whereupon an assembly is obtained comprising two substrates 10, 20 bonded to each other at their hydrophilic surfaces 11, 21. Step c) is preferably carried out at ambient temperature (i.e. at a temperature of approximately 20°C).

[0095] The specific molecule 30 remains attached to the hydrophilic surfaces 11, 21 and is enclosed at the bonding interface. It is trapped in the component and cannot evaporate.

[0096] The component thus obtained comprises two substrates 10 , 20 , each covered with a hydrophilic surface 11 , 21 , between which the specific molecule 30 , such as defined above, is arranged.

[0097] The method may comprise a subsequent step during which a thermal annealing is carried out after the bonding. The thermal annealing after the bonding makes it possible to strengthen the direct bond obtained in step c). The temperature range of the thermal annealing is, for example, from 100° C. to 1200° C. Preferably, the temperature range is from 100° C. to 500° C. and even more preferably from 100° C. to 300° C.

[0098] Depending on the temperature of the thermal annealing, the binding energy of the component after annealing ranges from 600 mJ to 5000 mJ. For example, for a temperature of 300° C., the binding energy ranges from 3500 mJ to 4000 mJ.

[0099] Illustrative and non-limiting examples of a specific example

[0100] In the various specific examples to be described, the substrates are silicon substrates of 200 mm diameter and 725 μm thick. They are thermally oxidized to obtain a 145 nm thick silicon oxide film on the surface. They are then cleaned with ozone water and SC1 followed by SC2 [a mixture of hydrochloric acid 30%, oxygenated water 30% and water (1:1:5)] to make their surface hydrophilic.

[0101] The specific molecule used for the conjugation here is N,N-diethyl-2-amino-ethanol (CAS: 100-37-8).

[0102] Example 1: Saturation of the surface

[0103] In a reactor with a volume of about 50 or 100 L, a beaker containing 10 mL of the pure specific molecule (undiluted) is placed. The solution is left in the sealed reactor to evaporate over 1 h30. Next, two silicon substrates are placed in this atmosphere for 3 minutes, and then they are bonded. The bonding wave then takes about 8 seconds to pass 200 mm, which is equivalent to bonding without this molecule.

[0104] The junction was annealed and the adhesion energy was measured at different temperatures. The binding energy obtained with the specific molecule was more significant than that without the specific molecule ( Figure 3 ). On the other hand, since the surface is saturated quickly, there is no dependence on the exposure time: the same results are obtained for an exposure period of 30 seconds, 8 minutes or 15 minutes.

[0105] Demonstration 2: Partial saturation of the surface

[0106] In a reactor with a volume of about 50 or 100 L, a beaker containing 1 mL of water and 0.02 mL of the specific molecule is placed. The solution is left in the sealed reactor to evaporate over 1 h30. Next, the two silicon substrates are placed in this atmosphere for 1 minute, and then they are bonded. The bonding wave then takes about 8 seconds to pass 200 mm, which is equivalent to bonding without this molecule.

[0107] The bond was annealed and the adhesion energy was measured at different temperatures. Figure 4 As shown in , the binding energy obtained with a partially saturated surface is more significant than when the surface is fully saturated. The lower concentration due to the lower saturation vapor pressure of the dilute solution makes it possible to obtain better binding energy over the entire temperature range.

[0108] Figure 5 Shows the binding energy according to the dilution of the solution of that particular molecule.

[0109] Example 3: Partial saturation of the surface from a liquid solution

[0110] Spin coating deposition is used to deposit a solution containing 1% by volume of the specific molecule on the surface of the plate: a stream consisting of a water-product mixture is generated on the surface rotating at 30 rpm until the entire surface is covered. Next, the dispensing of the product is stopped and it is rotated at 2000 rpm for 30 seconds to remove the excess. The two plates are then joined. The joining wave then takes about 8 seconds to pass 200 mm, which is equivalent to a joint without this molecule.

[0111] The bond was annealed and the adhesion energy was measured at different temperatures, and the same results as in Example 2 were obtained.

[0112] Observation under a scanning acoustic microscope (SAM) confirmed that the bond was defect-free ( Figure 6 ).

[0113] For comparison purposes, the following test was performed: Before joining them,

[0114] – Use isopropyl alcohol vapor to clean the board,

[0115] – Isopropyl alcohol vapor was used to clean the plate, then ammonia diluted to 2% was added.

[0116] No visible effect on the binding energy was observed.

Claims

1. A method for direct bonding of two substrates (10, 20), comprising the following steps: - supplying a first substrate (10) and a second substrate (20), wherein the first substrate (10) is covered by a first hydrophilic surface (11), and the second substrate (20) is covered by a second hydrophilic surface (21), - deposition of a specific molecule (30) on the first hydrophilic surface (11) or the second hydrophilic surface (21), the specific molecule (30) comprising a hydrophilic functional group and a basic functional group separated by at least one atom, - bringing the first hydrophilic surface (11) into contact with the second hydrophilic surface (21), whereby the two hydrophilic surfaces (11, 21) are bonded to each other, and the first substrate (10) and the second substrate (20) are assembled, Wherein the hydrophilic functional group is a hydroxyl functional group, wherein the basic functional group is a primary, secondary or tertiary amine, and The molar mass of the specific molecule (30) is less than or equal to 500 g / mole.

2. The bonding method according to claim 1, wherein after bringing the first hydrophilic surface (11) into contact with the second hydrophilic surface (21), the method comprises the step of applying a bonding annealing heat treatment.

3. The bonding method according to claim 2, wherein the bonding annealing heat treatment is at a temperature lower than or equal to 500°C.

4. The conjugation method according to any one of claims 1 to 3, wherein the specific molecule (30) is deposited on the first hydrophilic surface (11) and the second hydrophilic surface (21).

5. The conjugation method according to any one of claims 1 to 3, wherein the specific molecule (30) completely covers the first hydrophilic surface (11).

6. The conjugation method according to any one of claims 1 to 3, wherein the specific molecule (30) completely covers the second hydrophilic surface (21).

7. The conjugation method according to any one of claims 1 to 3, wherein the specific molecule (30) covers from 0.05% to 10% of the first hydrophilic surface (11) or the second hydrophilic surface (21).

8. The conjugation method according to claim 7, wherein the specific molecule (30) covers from 0.05% to 1% of the first hydrophilic surface (11) or the second hydrophilic surface (21).

9. The bonding method according to any one of claims 1 to 3, wherein the specific molecule (30) is deposited in liquid form.

10. The bonding method according to any one of claims 1 to 3, wherein the specific molecule (30) is deposited in a gaseous form.

11. The bonding method according to any one of claims 1 to 3, wherein the molar mass of the specific molecule (30) is lower than or equal to 200 g / mole.

12. The bonding method according to any one of claims 1 to 3, wherein the first substrate (10) or the second substrate (20) is a silicon substrate.

13. The bonding method according to any one of claims 1 to 3, wherein the first hydrophilic surface or the second hydrophilic surface is composed of an oxide.

14. The bonding method according to claim 13, wherein the first hydrophilic surface or the second hydrophilic surface is a deposited oxide, an oxide obtained by a heat treatment, or an oxide obtained by a chemical treatment.

15. A component comprising a first substrate (10) and a second substrate (20), wherein the first substrate (10) is covered by a first hydrophilic surface (11), and the second substrate (20) is covered by a second hydrophilic surface (21), wherein the first hydrophilic surface (11) is bonded to the second hydrophilic surface (21), The specific molecule (30) is disposed between the first hydrophilic surface (11) and the second hydrophilic surface (21), and the specific molecule (30) includes a hydrophilic functional group and a basic functional group separated by at least one atom. Wherein the hydrophilic functional group is a hydroxyl functional group, wherein the basic functional group is a primary, secondary or tertiary amine, and The molar mass of the specific molecule (30) is less than or equal to 500 g / mole.

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