JP2010091687A - Joining method, joined body and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a joining method for tightly joining two substrates to each other with high dimensional accuracy and reshaping a joined body to a predetermined shape while reducing residual stress produced at the joining interface after joining; a joined body obtained by tightly joining two substrates to each other with high dimensional accuracy by the joining method; and an optical element. <P>SOLUTION: The joining method includes: a step (first step) of preparing a first substrate 2 and a second substrate 4 having transmission for ultraviolet rays, and forming a joining film 3 by plasma polymerization on a surface of the first substrate 2; a step (second step) of applying energy to the joining film 3; a step (third step) of obtaining the joined body 5 by joining the first substrate 2 and the second substrate 4 through the joining film 3; a step (fourth step) of irradiating the joined body 5 with ultraviolet rays from the second substrate 4 side; and a step (fifth step) of reshaping the joined body 5 to a tabular shape by holding the joined body 5 in a state where it is pressed from the front and back sides by two surface plates 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bonding method, a bonded body, and an optical element.

Conventionally, when two members (substrates) are joined (adhered), a method of using an adhesive such as an epoxy adhesive, a urethane adhesive, or a silicone adhesive is often used.
The adhesive can exhibit adhesiveness regardless of the material of the member. For this reason, members composed of various materials can be bonded in various combinations.
For example, a wavelength plate is known as an optical element having a function of causing a phase difference in transmitted light. The wave plate is a combination of two birefringent crystal substrates such as quartz, and the substrates are bonded together using an adhesive.

In this way, when the substrates are bonded to each other using the adhesive, a liquid or paste adhesive is applied to the bonding surface, and the substrates are bonded to each other through the applied adhesive. Thereafter, the adhesive is cured by the action of heat or light to bond the substrates together.
However, since the adhesive is accompanied by volume shrinkage at the time of curing, a stress is generated such that the adhesive pulls the substrate after curing. In addition, when quartz substrates with different crystal axis orientations or substrates made of different materials are joined together, the thermal expansion coefficients of the substrates are different, so the stress caused by the difference in thermal expansion coefficient with changes in environmental temperature. Will occur. The stress (residual stress) generated in this way has caused the wave plate to be deformed and deteriorates the optical performance. Further, the deformed wave plate cannot be repaired and becomes a defective product, resulting in a decrease in yield.

In addition, since it is difficult to uniformly apply the adhesive with a predetermined thickness, it is inevitable that the distance between the substrates is not uniform. As a result, there has been a problem that an aberration such as wavefront aberration occurs in the wavelength plate, causing an unintended phase shift.
Furthermore, since the adhesive is composed of the resin material as described above, it has been a problem that the light resistance is poor.

Moreover, since the hardening time of an adhesive agent becomes very long, there also exists a problem that adhesion requires a long time.
On the other hand, there is a solid bonding method as a bonding method that does not use an adhesive.
Solid bonding is a method of directly bonding members without an intermediate layer such as an adhesive (see, for example, Patent Document 1).
According to such solid bonding, since an intermediate layer such as an adhesive is not used, a bonded body with high dimensional accuracy can be obtained.

However, solid bonding has a problem that the material of the member is limited. Specifically, in general, solid bonding can only be performed between the same kind of materials. Even if members made of different materials are joined together, stress is generated at the joining interface without relieving the difference in thermal expansion coefficient between the two members, leading to problems such as deformation and peeling. In addition, since the interface once bonded cannot be loosened, it is impossible to repair the deformation or the like generated after the bonding. In addition, since the materials that can be bonded are limited to silicon-based materials, some metal materials, and the like, the application range of solid bonding is extremely limited.
Furthermore, the atmosphere for performing solid bonding is limited to a reduced-pressure atmosphere, and there are problems in the bonding process, such as requiring high-temperature (about 700 to 800 ° C.) heat treatment.

JP-A-5-82404

  An object of the present invention is a bonding method that can firmly bond two substrates to each other with high dimensional accuracy, and can correct the bonded body to a predetermined shape while reducing the residual stress generated at the bonding interface after bonding, Another object of the present invention is to provide a bonded body and an optical element in which two substrates are firmly bonded with high dimensional accuracy by such a bonding method.

Such an object is achieved by the present invention described below.
In the bonding method of the present invention, a first substrate and a second substrate, at least one of which is transparent to ultraviolet rays, are prepared, and siloxane (Si—O) is formed on the surface of the first substrate by plasma polymerization. A first step of forming a bonding film including a Si skeleton having a random atomic structure including a bond and a leaving group bonded to the Si skeleton;
A second step in which energy is imparted to the bonding film, and the leaving group present at least near the surface of the bonding film is released from the Si skeleton, thereby exhibiting adhesiveness;
A third step of bonding the first substrate and the second substrate via the bonding film to obtain a bonded body;
A fourth step of irradiating the bonded body with ultraviolet rays from the side of the first substrate and the second substrate having transparency to the ultraviolet rays, and
And pressurizing the bonded body irradiated with the ultraviolet rays to correct it to a predetermined shape.
Accordingly, the two substrates can be firmly bonded with high dimensional accuracy, and the bonded body can be corrected to a predetermined shape while reducing the residual stress generated at the bonded interface after bonding.

In the bonding method of the present invention, it is preferable that the total of the Si atom content and the O atom content is 10 to 90 atomic% among atoms obtained by removing H atoms from all atoms constituting the bonding film. .
Thereby, in the bonding film, Si atoms and O atoms form a strong network, and the bonding film itself becomes strong. Further, such a bonding film exhibits a particularly high bonding strength with respect to the first substrate and the second substrate.

In the bonding method of the present invention, the abundance ratio of Si atoms and O atoms in the bonding film is preferably 3: 7 to 7: 3.
As a result, the stability of the bonding film is increased, and the first substrate and the second substrate can be bonded more firmly.
In the bonding method of the present invention, the crystallinity of the Si skeleton is preferably 45% or less.
As a result, the Si skeleton particularly includes a random atomic structure. And the joining film excellent in dimensional accuracy and adhesiveness is obtained.

In the bonding method of the present invention, it is preferable that the bonding film includes a Si—H bond.
Si-H bonds are thought to inhibit the regular formation of siloxane bonds. For this reason, the siloxane bond is formed so as to avoid the Si—H bond, and the regularity of the Si skeleton is lowered. In this way, according to the plasma polymerization method, the Si skeleton having a low crystallinity can be efficiently formed by including the Si—H bond in the bonding film.

In the bonding method of the present invention, when the peak intensity attributed to the siloxane bond is 1 in the infrared absorption spectrum of the bonding film containing the Si—H bond, the peak intensity attributed to the Si—H bond is 0. It is preferable that it is 001-0.2.
As a result, the atomic structure in the bonding film becomes relatively random. For this reason, the bonding film is particularly excellent in bonding strength, chemical resistance and dimensional accuracy.

In the bonding method of the present invention, the leaving group includes an H atom, a B atom, a C atom, an N atom, an O atom, a P atom, an S atom, and a halogen atom, or each of these atoms bonded to the Si skeleton. It is preferably composed of at least one selected from the group consisting of atomic groups arranged in such a manner.
These leaving groups are relatively excellent in binding / leaving selectivity by applying energy. For this reason, the leaving group which leaves | separates comparatively easily and uniformly by providing energy is obtained, and the adhesiveness of the bonding film can be further enhanced.
In the bonding method of the present invention, the leaving group is preferably an alkyl group.
Thereby, a bonding film excellent in weather resistance and chemical resistance can be obtained.

In the bonding method of the present invention, in the infrared absorption spectrum of the bonding film containing a methyl group as the leaving group, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the methyl group is 0. It is preferable that it is 05-0.45.
As a result, the content ratio of the methyl group is optimized, and a necessary and sufficient number of active hands are generated in the bonding film while preventing the methyl group from unnecessarily inhibiting the formation of the siloxane bond. Adhesiveness is sufficient. Further, the bonding film exhibits sufficient weather resistance and chemical resistance due to the methyl group.

In the bonding method of the present invention, it is preferable that the bonding film has an active hand after the leaving group existing at least near the surface thereof is released from the Si skeleton.
As a result, the bonding film can be strongly bonded to the second substrate based on chemical bonding.
In the bonding method of the present invention, the active hand is preferably a dangling bond or a hydroxyl group.
As a result, particularly strong bonding to the second substrate becomes possible.

In the bonding method of the present invention, the bonding film is preferably composed of polyorganosiloxane as a main material.
As a result, a bonding film superior in adhesiveness can be obtained. In addition, the bonding film has excellent weather resistance and chemical resistance, and is effectively used for bonding substrates that are exposed to chemicals or the like for a long time.
In the bonding method of the present invention, it is preferable that the polyorganosiloxane is mainly composed of a polymer of octamethyltrisiloxane.
Thereby, a bonding film having particularly excellent adhesiveness can be obtained.

In the bonding method of the present invention, in the plasma polymerization method, the high-frequency power density when generating plasma is preferably 0.01 to 100 W / cm ² .
Accordingly, it is possible to reliably form a Si skeleton having a random atomic structure while preventing the plasma gas from being added to the source gas more than necessary due to the high frequency power density.

In the bonding method of the present invention, the average thickness of the bonding film is preferably 1 to 1000 nm.
Thereby, these can be joined more firmly, preventing the dimensional accuracy of the joined body which joined the 1st board | substrate and the 2nd board | substrate significantly falling.
In the bonding method of the present invention, the bonding film is preferably a solid having no fluidity.
Thereby, the dimensional accuracy of a joined body becomes remarkably high compared with the past. In addition, stronger bonding can be achieved in a shorter time than in the past.
In the bonding method of the present invention, the refractive index of the bonding film is preferably 1.35 to 1.6.
Since such a bonding film has a refractive index relatively close to that of quartz or quartz glass, it is preferably used, for example, when manufacturing an optical component having a structure that penetrates the bonding film.

In the bonding method of the present invention, it is preferable that the substrate having transparency to the ultraviolet light among the first substrate and the second substrate is made of quartz glass or quartz.
As a result, the refractive index difference at the bonding interface is reduced, and for example, a bonded body suitable for a laminated optical component having a high light transmittance can be obtained. Moreover, since the difference in thermal expansion coefficient between the substrate and the bonding film is reduced, deformation after bonding can be suppressed.

In the bonding method of the present invention, it is preferable that the wavelength of the ultraviolet light irradiated in the fourth step is 120 to 200 nm.
By using ultraviolet rays of such a wavelength, it is possible to break chemical bonds having a lower binding energy without almost breaking the Si-O bond in the bonding film, so that the bonding film has an appropriate flexibility. Can be granted.

In the bonding method of the present invention, the ultraviolet rays irradiated in the fourth step have energy that can cut chemical bonds other than Si-O bonds without cutting Si-O bonds in the bonding film. Preferably there is.
As a result, the bonding film irradiated with ultraviolet rays leaves many chemical bonds (for example, Si—C bonds) other than Si—O bonds inside, and exhibits sufficient flexibility when irradiated with ultraviolet rays. Thus, the residual stress can be effectively reduced.
In the bonding method of the present invention, it is preferable that the ultraviolet irradiation time in the fourth step is 1 second to 10 minutes.
Thereby, energy necessary and sufficient for imparting flexibility to the chemical bond of the bonding film is imparted.
In the bonding method of the present invention, in the fifth step, it is preferable that the time for holding the bonded body in a state of being corrected to a predetermined shape is 10 seconds or more.
Thereby, the recombination of the chemical bond is completed and the flexibility of the chemical bond of the bonding film is surely lowered, and the residual stress can be sufficiently reduced and the shape of the bonded body can be sufficiently corrected.

In the joining method of the present invention, it is preferable that the joined body is heated and held in a state where the joined body is corrected to a predetermined shape.
As a result, recombination of chemical bonds in the bonding film is promoted, and the bonding film can be cured in a shorter time. For this reason, it is possible to reduce the residual stress and correct the shape of the bonded body in a shorter time.

In the bonding method of the present invention, the pressing of the bonded body in the fifth step is performed by pressing the pressing surface against the bonded body using a jig having a pressing surface including the bonded body. ,
It is preferable that the joined body is corrected by being deformed along the pressing surface of the jig.
Thereby, it is possible to press a joined body uniformly and to correct the shape correctly.

In the bonding method of the present invention, the energy is applied by irradiating the bonding film with an energy ray, heating the bonding film, applying a compressive force to the bonding film, and applying the bonding film to plasma. It is preferably performed by at least one of the exposure methods.
Thereby, energy can be imparted to the bonding film relatively easily and efficiently.
In the bonding method of the present invention, it is preferable that the application of energy is performed in an air atmosphere.
Thereby, it is not necessary to spend time and cost to control the atmosphere, and energy can be applied more easily.

In the bonding method of the present invention, in the first step, a bonding film similar to the bonding film is formed on the surface of the second substrate,
In the second step, after applying energy to the bonding films, in the third step, the bonding films are brought into close contact with each other, and the first substrate and the second substrate are bonded. It is preferable to join to obtain the joined body.
Thereby, a 1st board | substrate and a 2nd board | substrate can be joined more firmly.

The joined body of the present invention has two substrates, which are joined by the joining method of the present invention,
It has no residual stress inside.
Thereby, a joined body with high dimensional accuracy is obtained.
The optical element of the present invention includes the joined body of the present invention.
Thereby, an optical element with high dimensional accuracy and high optical performance can be obtained.

Hereinafter, the bonding method, the bonded body, and the optical element of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<Join method>
The bonding method of the present invention is a method of bonding two substrates (the first substrate 2 and the second substrate 4) via the bonding film 3. According to this method, the two substrates 2 and 4 can be firmly bonded with high dimensional accuracy. The bonding film 3 is formed by a plasma polymerization method, and includes a Si skeleton having a random atomic structure including a siloxane (Si—O) bond and a leaving group bonded to the Si skeleton. .
Such a bonding film 3 is one in which leaving groups present at least near the surface of the bonding film 3 are desorbed from the Si skeleton by applying energy. The bonding film 3 has a feature that adhesion to other adherends is exhibited in a region to which energy of the surface is imparted by elimination of the leaving group.

The bonding film 3 having such characteristics is capable of bonding the two substrates 2 and 4 firmly with high dimensional accuracy and efficiently at low temperatures. By using the bonding film 3, a highly reliable bonded body 5 formed by firmly bonding the two substrates 2 and 4 is obtained.
And the bonded body 5 with high dimensional accuracy is obtained by performing the process which corrects a shape with respect to the bonded body 5 obtained in this way, reducing a residual stress.

<< First Embodiment >>
Next, a first embodiment of the bonding method of the present invention will be described.
1 and 2 are views (longitudinal sectional views) for explaining a first embodiment of the joining method of the present invention. In the following description, the upper side in FIGS. 1 and 2 is referred to as “upper” and the lower side is referred to as “lower”.

  In the bonding method according to the present embodiment, a first substrate 2 and a second substrate 4 that is transparent to ultraviolet rays are prepared, and a bonding film 3 is formed on the surface of the first substrate 2 by a plasma polymerization method. A process of forming a film (first process), a process of applying energy to the bonding film 3 (second process), and bonding the first substrate 2 and the second substrate 4 via the bonding film 3. The step of obtaining the joined body 5 (third step), the step of irradiating the joined body 5 with ultraviolet rays from the second substrate 4 side (fourth step), and the joined body 5 with two surface plates. Is held in a state of being pressed from the front and back, and the shape of the joined body 5 is corrected to a flat plate shape (fifth step). Hereinafter, each process will be described sequentially.

[1] First, the first substrate 2 and the second substrate 4 are prepared. At least one of the first substrate 2 and the second substrate 4 needs to be transparent to ultraviolet rays. In the present embodiment, the second substrate 4 is described as having transparency. To do.
The constituent materials of the first substrate 2 are polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), cyclic polyolefin, modified polyolefin, polyvinyl chloride, and polyvinylidene chloride, respectively. , Polystyrene, polyamide, polyimide, polyamideimide, polycarbonate, poly- (4-methylpentene-1), ionomer, acrylic resin, polymethyl methacrylate, acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-styrene copolymer Polymer (AS resin), butadiene-styrene copolymer, polyoxymethylene, polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PE ), Polyester such as polyethylene naphthalate, polybutylene terephthalate (PBT), polycyclohexane terephthalate (PCT), polyether, polyether ketone (PEK), polyether ether ketone (PEEK), polyether imide, polyacetal (POM), Polyphenylene oxide, modified polyphenylene oxide, polysulfone, polyethersulfone, polyphenylene sulfide, polyarylate, aromatic polyester (liquid crystal polymer), polytetrafluoroethylene, polyvinylidene fluoride, other fluororesins, styrene, polyolefin, polychlorination Vinyl, polyurethane, polyester, polyamide, polybutadiene, trans polyisoprene, fluoro rubber, chlorinated polyester Various thermoplastic elastomers such as len, epoxy resins, phenol resins, urea resins, melamine resins, aramid resins, unsaturated polyesters, silicone resins, polyurethanes, etc., or copolymers, blends, polymer alloys mainly containing these Such as Fe, Ni, Co, Cr, Mn, Zn, Pt, Au, Ag, Cu, Pd, Al, W, Ti, V, Mo, Nb, Zr, Pr, Nd, Sm, etc. Metals or alloys containing these metals, carbon steel, stainless steel, indium tin oxide (ITO), metal materials such as gallium arsenide, silicon materials such as single crystal silicon, polycrystalline silicon, amorphous silicon , Silicate glass (quartz glass), alkali silicate glass, soda lime glass, potash lime glass, lead (alkali) glass, barium Glass, glass materials such as borosilicate glass, ceramic materials such as alumina, zirconia, ferrite, silicon nitride, aluminum nitride, boron nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, tungsten carbide, graphite Such a carbon-based material, or a composite material obtained by combining one or more of these materials.

On the other hand, the constituent material of the second substrate 4 may be appropriately selected from the constituent materials of the first substrate 2 that are transparent to ultraviolet rays.
Note that the constituent material of the first substrate 2 and the constituent material of the second substrate 4 may be the same or different from each other.
Further, the surface of the first substrate 2 may be subjected to a plating process such as Ni plating, a passivation process such as a chromate process, or a nitriding process.

In addition, although the average thickness of the 1st board | substrate 2 and the 2nd board | substrate 4 is not specifically limited, It is preferable that it is about 0.01-10 mm, respectively, and it is more preferable that it is about 0.1-3 mm. By setting the average thicknesses of the first substrate 2 and the second substrate 4 within the above ranges, the substrates 2 and 4 can be easily bent and sufficiently deformed along each other's shape. , These adhesiveness becomes higher. For this reason, the bonding strength between the substrates 2 and 4 can be increased.
Further, in the process described later, when the shape of the bonded body 5 of the first substrate 2 and the second substrate 4 is corrected, the bonded body 5 is easily bent, so that the shape can be corrected easily and accurately. It becomes possible.

Next, the bonding film 3 is formed on the surface of the first substrate 2 (first step). The bonding film 3 is located between the first substrate 2 and the second substrate 4 and bears the bonding therebetween.
As shown in FIGS. 3 and 4, the bonding film 3 includes a Si skeleton 301 including a siloxane (Si—O) bond 302 and a random atomic structure, and a leaving group 303 bonded to the Si skeleton 301. It is what you have.
The bonding film 3 will be described later in detail.

In addition, at least in the region where the bonding film 3 is to be formed on the first substrate 2, the first substrate 2 is bonded to the first substrate 2 in advance before the bonding film 3 is formed according to the constituent material of the first substrate 2. It is preferable to perform a surface treatment for improving the adhesion with the film 3.
Examples of the surface treatment include physical surface treatment such as sputtering treatment and blast treatment, plasma treatment using oxygen plasma, nitrogen plasma, etc., corona discharge treatment, etching treatment, electron beam irradiation treatment, ultraviolet irradiation treatment, ozone Examples include chemical surface treatment such as exposure treatment, or a combination of these. By performing such treatment, the region where the bonding film 3 of the first substrate 2 is to be formed can be cleaned and the region can be activated. Thereby, the bonding strength between the first substrate 2 and the bonding film 3 can be increased.

In addition, by using plasma treatment among these surface treatments, the surface of the first substrate 2 can be particularly optimized in order to form the bonding film 3.
In addition, when the 1st board | substrate 2 which performs surface treatment is comprised with the resin material (polymer material), especially a corona discharge process, a nitrogen plasma process, etc. are used suitably.
Further, depending on the constituent material of the first substrate 2, there is a material in which the bonding strength of the bonding film 3 is sufficiently high without performing the surface treatment as described above. Examples of the constituent material of the first substrate 2 that can obtain such an effect include those mainly composed of various metal-based materials, various silicon-based materials, various glass-based materials and the like as described above.

The surface of the first substrate 2 made of such a material is covered with an oxide film, and a relatively active hydroxyl group is bonded to the surface of the oxide film. Therefore, when the first substrate 2 made of such a material is used, the adhesion strength between the first substrate 2 and the bonding film 3 can be increased without performing the surface treatment as described above.
In this case, the entire first substrate 2 may not be made of the above material, and at least the vicinity of the surface of the region where the bonding film 3 is to be formed is made of the above material. That's fine.

  In the case of the second substrate 4, depending on the constituent material, the bonding strength between the first substrate 2 and the second substrate 4 is sufficiently high without performing the surface treatment as described above. is there. The constituent material of the second substrate 4 that can obtain such an effect is the same as the constituent material of the first substrate 2 described above, that is, various metal-based materials, various silicon-based materials, various glass-based materials, and the like. Can be used.

Further, in the case where the following substrate or substance is included in the region that is in close contact with the bonding film 3 of the second substrate 4, the first substrate 2 and the second substrate can be obtained without performing the surface treatment as described above. The bonding strength with 4 can be sufficiently increased.
Examples of such groups and substances include functional groups such as hydroxyl groups, thiol groups, carboxyl groups, amino groups, nitro groups, and imidazole groups, radicals, ring-opened molecules, double bonds, and triple bonds. And at least one group or substance selected from the group consisting of a saturated bond, a halogen such as F, Cl, Br, and I, and a peroxide.

Further, it is preferable to appropriately select and perform various surface treatments as described above so that a surface having such a material can be obtained.
Further, instead of the surface treatment, an intermediate layer is formed in advance in at least a region where the bonding film 3 is to be formed and a region in close contact with the bonding film 3 of the second substrate 4. Is preferred.
The intermediate layer may have any function. For example, a layer having a function of improving adhesion to the bonding film 3, a cushioning function (buffer function), a function of reducing stress concentration, and the like are preferable. By using such an intermediate layer, a highly reliable bonded body can be obtained.

Examples of the constituent material of the intermediate layer include metal materials such as aluminum and titanium, metal oxides, oxide materials such as silicon oxide, metal nitrides, and nitride materials such as silicon nitride. Carbon materials such as graphite and diamond-like carbon, silane coupling agents, thiol compounds, metal alkoxides, self-assembled film materials such as metal-halogen compounds, resin adhesives, resin films, resin coating materials, Various rubber materials, resin materials such as various elastomers, and the like can be used, and one or more of these can be used in combination.
Further, among the intermediate layers formed of these materials, the bonding strength of the bonded body 5 can be particularly increased by the intermediate layer formed of the oxide-based material.

[2] Next, energy is applied to the surface 35 of the bonding film 3 (second step).
When energy is applied, the leaving group 303 is detached from the Si skeleton 301 in the bonding film 3. Then, after the leaving group 303 is released, active hands are generated on the surface 35 and inside of the bonding film 3. Thereby, the adhesiveness with the second substrate 4 is expressed on the surface 35 of the bonding film 3. As a result, the bonding film 3 can be firmly bonded to the second substrate 4 based on chemical bonding.

  Here, the energy applied to the bonding film 3 may be applied by any method, for example, a method of irradiating energy rays, a method of heating the bonding film 3, and a compressive force (physical energy) applied to the bonding film 3. Examples thereof include a method of applying, a method of exposing to plasma (applying plasma energy), a method of exposing to ozone gas (applying chemical energy), and the like. Of these methods, any two or more methods may be appropriately combined.

In addition, as a method for applying energy to the bonding film 3, it is particularly preferable to use a method in which the bonding film 3 is irradiated with energy rays. Since these methods can apply energy to the bonding film 3 relatively easily and efficiently, they are suitable as energy applying methods.
Among these, examples of energy rays include light such as ultraviolet rays and laser light, X-rays, γ rays, electron beams, particle beams such as ion beams, and combinations of these energy rays.

  Among these energy rays, it is particularly preferable to use ultraviolet rays having a wavelength of about 126 to 300 nm. According to such ultraviolet rays, the amount of energy applied is optimized, so that the Si skeleton 301 in the bonding film 3 is prevented from being destroyed more than necessary, and between the Si skeleton 301 and the leaving group 303. Can be selectively cleaved. Thereby, adhesiveness can be expressed in the bonding film 3 while preventing the characteristics (mechanical characteristics, chemical characteristics, etc.) of the bonding film 3 from being deteriorated.

In addition, since ultraviolet rays can be processed in a short time without unevenness, the leaving group 303 can be efficiently eliminated. Furthermore, ultraviolet rays also have the advantage that they can be generated with simple equipment such as UV lamps.
The wavelength of ultraviolet light is more preferably about 160 to 200 nm.
In the case of using the UV lamp, the output may vary depending on the area of the bonding film 3 is preferably from ^1mW / cm ^{2 ~1W} / cm 2 or ^so, at 5mW / cm ² ~50mW / cm 2 of about More preferably. In this case, the distance between the UV lamp and the bonding film 3 is preferably about 3 to 3000 mm, more preferably about 10 to 1000 mm.

  Further, the time for irradiating the ultraviolet rays is such a time that the leaving group 303 in the vicinity of the surface 35 of the bonding film 3 can be released, that is, a time that the leaving group 303 inside the bonding film 3 is not released in a large amount. Is preferable. Specifically, it is preferably about 0.5 to 30 minutes, more preferably about 1 to 10 minutes, although it varies slightly depending on the amount of ultraviolet light, the constituent material of the bonding film 3 and the like.

Moreover, although an ultraviolet-ray may be irradiated continuously in time, you may irradiate intermittently (pulse form).
On the other hand, examples of the laser light include an excimer laser (femtosecond laser), an Nd-YAG laser, an Ar laser, a CO ₂ laser, and a He—Ne laser.

  The bonding film 3 may be irradiated with energy rays in any atmosphere. Specifically, the atmosphere, an oxidizing gas atmosphere such as oxygen, a reducing gas atmosphere such as hydrogen, nitrogen, An inert gas atmosphere such as argon, a reduced pressure (vacuum) atmosphere obtained by reducing these atmospheres, and the like can be given, and it is particularly preferable to perform in an air atmosphere. Thereby, it is not necessary to spend time and cost to control the atmosphere, and irradiation of energy rays can be performed more easily.

As described above, according to the method of irradiating the energy beam, it is easy to selectively apply energy to the bonding film 3. Can be prevented.
Moreover, according to the method of irradiating energy rays, the magnitude of energy to be applied can be easily adjusted with high accuracy. For this reason, it becomes possible to adjust the desorption amount of the leaving group 303 desorbed from the bonding film 3. In this way, by adjusting the amount of elimination of the leaving group 303, the bonding strength between the first substrate 2 and the second substrate 4 can be easily controlled.

That is, by increasing the amount of elimination of the leaving group 303, more active hands are generated on the surface 35 and inside of the bonding film 3, so that the adhesiveness expressed in the bonding film 3 can be further increased. On the other hand, by reducing the amount of elimination of the leaving group 303, the number of active hands generated on the surface and inside of the bonding film 3 can be reduced, and the adhesiveness expressed in the bonding film 3 can be suppressed.
Furthermore, according to the method of irradiating energy rays, a large amount of energy can be applied in a short time, so that the energy can be applied more efficiently.

  In addition, in order to adjust the magnitude | size of the energy to provide, what is necessary is just to adjust conditions, such as the kind of energy beam, the output of an energy beam, the irradiation time of an energy beam. Specifically, in the process described later, the bonded body 5 is irradiated with ultraviolet rays, but the energy beam irradiated to the bonding film 3 in this process is irradiated with energy rays so that the bonding film 3 is not destroyed. Adjust the conditions. For example, when irradiating with ultraviolet rays in this step, the irradiation time is preferably shorter than the irradiation time when irradiating the bonded body 5 described later. Moreover, you may make it use the ultraviolet of a long wavelength or low output rather than the process mentioned later.

  Further, as a method of applying energy to the bonding film 3, a method of exposing to plasma is also preferably used (see FIG. 2B). According to this method, energy can be selectively applied to the surface of the bonding film 3, so that active hands can be generated on the surface of the bonding film 3. Furthermore, since the inside of the bonding film 3 is not in contact with plasma, the state before energy application is maintained. Since this state contains a large number of leaving groups 303 and can easily break and recombine chemical bonds when energy is applied, bonding that can reliably correct the shape in the process described later. The body 5 can be obtained. In other words, such a bonding film 3 includes many chemical bonds that have room for cutting and rebonding in a process described later, so that the shape can be remarkably corrected.

  On the other hand, when energy more than necessary is applied to the bonding film 3 by the energy rays, the leaving group 303 is almost eliminated from the inside of the bonding film 3, and a bond that can be cleaved / recombined in a process described later is formed. May decrease significantly. In such a state, the flexibility of the chemical bond of the bonding film 3 may be lost. Therefore, the application of energy by the method of exposing the plasma is particularly useful in the present invention.

  As a method for exposing the bonding film 3 to plasma (plasma treatment), a method using atmospheric pressure plasma is preferable. According to atmospheric pressure plasma, plasma treatment can be easily performed without using expensive equipment such as decompression means. In addition to the direct plasma method in which plasma is generated in the vicinity of the bonding film 3, a remote plasma method or a downflow plasma method in which the object to be processed and the plasma generation unit are separated is also preferably used for this plasma treatment. According to the direct plasma method, since plasma is generated in the vicinity of the bonding film 3, plasma processing can be performed efficiently and uniformly. Further, when the object to be processed and the plasma generating part are separated from each other, the object to be processed and the plasma generating part do not interfere with each other, so that the object to be processed can be avoided from ion damage.

In addition, examples of the gas that generates plasma include Ar, He, H ₂ , N ₂ , and O ₂ , and a mixture of two or more of these may be used. Among these, in consideration of oxidation of the bonding film 3, an inert gas such as Ar is preferably used.
The plasma treatment can also be performed using a plasma polymerization apparatus 100 shown in FIG. That is, after forming the bonding film 3 using the plasma polymerization apparatus 100 shown in FIG. 5, the plasma treatment of this step can be continuously performed without taking it out from the apparatus, so that the bonding method of the present invention is simplified. Can be achieved.

  Here, the bonding film 3 before energy is applied has a Si skeleton 301 and a leaving group 303 as shown in FIG. When energy is applied to the bonding film 3, the leaving group 303 (in this embodiment, a methyl group) is detached from the Si skeleton 301. As a result, as shown in FIG. 4, active hands 304 are generated on the surface 35 of the bonding film 3 and activated. As a result, adhesiveness develops on the surface of the bonding film 3.

  By the way, “activating” the bonding film 3 means that the surface 35 of the bonding film 3 and the internal leaving group 303 are removed, and a bond that is not terminated in the Si skeleton 301 (hereinafter referred to as “unbonded bond”). "Or" dangling bond "), a state in which this dangling bond is terminated by a hydroxyl group (OH group), or a state in which these states are mixed.

Therefore, the active hand 304 means a dangling bond (dangling bond) or a dangling bond terminated by a hydroxyl group. According to such an active hand 304, particularly strong bonding to the second substrate 4 is possible.
The latter state (state in which the dangling bond is terminated by a hydroxyl group) is, for example, that the moisture in the atmosphere terminates the dangling bond by irradiating the bonding film 3 with energy rays in the atmosphere. Can be easily generated.

  In the present embodiment, the case where energy is applied to the bonding film 3 in advance before bonding the first substrate 2 and the second substrate 4 is described. It may be performed when the first substrate 2 and the second substrate 4 are bonded (overlapped) or after being bonded (overlapped). Such a case will be described in a second embodiment to be described later.

[3] Next, as shown in FIG. 1C, the first substrate 2 and the second substrate 4 are bonded so that the activated bonding film 3 and the second substrate 4 are in close contact with each other. Match. Thereby, the joined body 5 as shown in FIG. 2D is obtained (third step).
The bonded body 5 thus obtained is not bonded mainly based on a physical bond such as an anchor effect, but a short time such as a covalent bond, unlike the adhesive used in the conventional bonding method. Bonding is based on strong chemical bonds that occur in For this reason, the joined body 5 can be formed in a short time, is extremely difficult to peel off, and is less likely to cause joining unevenness.

In addition, according to such a method, unlike the conventional solid bonding, the heat treatment at a high temperature (for example, 700 ° C. or higher) is not required, so the first substrate 2 made of a material having low heat resistance. The second substrate 4 can also be used for bonding.
In addition, since the first substrate 2 and the second substrate 4 are bonded via the bonding film 3, there is an advantage that there are no restrictions on the constituent materials of the first substrate 2 and the second substrate 4.

From the above, according to the present invention, the selection range of each constituent material of the first substrate 2 and the second substrate 4 can be expanded.
Further, since solid bonding does not involve a bonding layer, when there is a large difference in thermal expansion coefficient between the first substrate 2 and the second substrate 4, stress based on the difference is concentrated on the bonding interface. However, in the bonded body (bonded body of the present invention) 5, stress concentration is relaxed by the bonding film 3, and peeling can be prevented.

  In the present embodiment, the bonding film 3 is provided on only one of the first substrate 2 and the second substrate 4 to be bonded (in the present embodiment, the first substrate 2). When forming the bonding film 3 on the first substrate 2, the first substrate 2 is exposed to plasma for a relatively long time depending on the method of forming the bonding film 3. The second substrate 4 is not exposed to plasma. Therefore, for example, even when the durability of the second substrate 4 against plasma is extremely low, according to the method according to the present embodiment, the first substrate 2 and the second substrate 4 are firmly bonded. be able to. Therefore, the material constituting the second substrate 4 has an advantage that it can be selected from a wide range of materials without much consideration of durability against plasma.

Here, the mechanism by which the first substrate 2 and the second substrate 4 are joined in this step will be described.
For example, in the case where a hydroxyl group is exposed on the bonding surface of the second substrate 4, in this step, the surface 35 of the bonding film 3 and the bonding surface of the second substrate 4 are in contact with each other. When these are bonded together, the hydroxyl group present on the surface 35 of the bonding film 3 and the hydroxyl group present on the bonding surface of the second substrate 4 are attracted to each other by hydrogen bonding, and an attractive force is generated between the hydroxyl groups. It is assumed that the first substrate 2 and the second substrate 4 are joined by this attractive force.
Further, the hydroxyl groups attracting each other by this hydrogen bond are dehydrated and condensed depending on the temperature condition or the like. As a result, at the contact interface between the first substrate 2 and the second substrate 4, the bonds in which the hydroxyl groups are bonded are bonded via oxygen atoms. Thereby, it is guessed that the 1st board | substrate 2 and the 2nd board | substrate 4 are joined more firmly.

  Note that the active state of the surface of the bonding film 3 activated in the step [2] relaxes with time. For this reason, it is preferable to perform this process [3] as soon as possible after completion of the process [2]. Specifically, after the completion of the step [2], the step [3] is preferably performed within 60 minutes, and more preferably within 5 minutes. If it is within this time, the surface of the bonding film 3 is maintained in a sufficiently active state. Therefore, when the first substrate 2 and the second substrate 4 are bonded together in this step, there is a sufficient gap between them. Can obtain a high bonding strength.

  In other words, since the bonding film 3 before activation is a bonding film having the Si skeleton 301, it is chemically relatively stable and has excellent weather resistance. For this reason, the bonding film 3 before being activated is suitable for long-term storage. Therefore, the first substrate 2 having such a bonding film 3 is manufactured or purchased in large quantities and stored, and just before the bonding in this step, only the necessary number is added to the step [2]. If the described energy application is performed, it is effective from the viewpoint of manufacturing efficiency of the bonded body 5.

As described above, the joined body (joined body of the present invention) 5 shown in FIG. 2D can be obtained.
In FIG. 2D, the second substrate 4 is overlaid so as to cover the entire surface of the bonding film 3, but their relative positions may be shifted from each other. That is, the counter substrate 4 may protrude from the bonding film 3.
The bonded body 5 thus obtained preferably has a bonding strength between the first substrate 2 and the second substrate 4 of 5 MPa (50 kgf / cm ² ) or more, preferably 10 MPa (100 kgf / cm ^2). ) Or more. The bonded body 5 having such bonding strength can sufficiently prevent the peeling.

In the case of solid bonding such as conventional silicon direct bonding, even if the surface used for bonding is activated, the active state can be maintained for only a very short time of several seconds to several tens of seconds in the atmosphere. could not. For this reason, there has been a problem that it is not possible to sufficiently secure the time required for operations such as bonding the two substrates to be bonded after the surface activation.
On the other hand, according to the present invention, since the bonding is performed using the bonding film 3 having the Si skeleton 301, the active state can be maintained for a relatively long time of several minutes or more. Therefore, it is possible to sufficiently secure the time required for the bonding operation, and it is possible to increase the efficiency of the bonding operation.

By the way, the bonded body 5 manufactured in this way often undergoes deformation such as warpage and distortion as shown in FIG. This is because internal stress (residual stress) caused by a difference in thermal expansion coefficient between the first substrate 2 and the second substrate 4, a difference in thermal expansion coefficient between the substrates 2, 4 and the bonding film 3, etc. Is mentioned. In particular, a material having a different coefficient of thermal expansion depending on the direction of the crystal axis such as quartz is likely to be deformed due to the residual stress.
Such deformation of the joined body 5 has been a problem before the use of the joined body 5. For example, in an optical element in which optical components are bonded together by the bonding method of the present invention, various aberrations such as wavefront aberration are generated along with the deformation. As a result, the optical performance of the optical component is degraded.

Therefore, in the present invention, after obtaining the joined body 5, the following steps [4] and [5] are performed in order to reduce the residual stress in the joined body 5. Hereinafter, this process will be described.
[4] As shown in FIG. 2E, ultraviolet rays are irradiated from the second substrate 4 side of the bonded body 5 (fourth step).
By this ultraviolet irradiation, a part of the chemical bond in the bonding film 3 is cut, and the flexibility of the chemical bond of the bonding film 3 is improved.

For example, the bonding film 3 formed using a silane-based gas as a raw material gas contains chemical bonds such as Si—O bonds and Si—C bonds. Among these, Si—O bonds are included. Is not cut, but is irradiated with ultraviolet rays having such energy that a chemical bond (for example, Si—C bond) having a bond energy lower than that of the Si—O bond is cut. By using such ultraviolet rays, only a part of the chemical bond in the bonding film 3 is cut while preventing the Si skeleton 301 in the bonding film 3 from being completely destroyed, and the chemical bonding of the bonding film 3 is performed. Appropriate flexibility can be imparted. As a result, the bonded body 5 can reliably reduce the residual stress through a process described later.
Here, since the ultraviolet rays pass through the bonding film 3, not only the surface of the bonding film 3 but also the internal chemical bonds are cut.

  By the way, when energy is applied to the bonding film 3 in the step [2], a chemical bond near the surface of the bonding film 3 is cut by using a method in which the bonding film 3 is exposed to plasma. The chemical bond is not broken more than necessary. For this reason, the bonding film 3 has many chemical bonds (for example, Si—C bonds) other than Si—O bonds left therein, and exhibits sufficient flexibility when irradiated with ultraviolet rays in this step. Residual stress can be effectively reduced.

  For the ultraviolet rays used in this step, those having a wavelength of about 120 to 200 nm are preferably used, and those having a wavelength of about 150 to 200 nm are more preferably used. Ultraviolet light having such a wavelength can selectively cut a chemical bond having a lower binding energy without almost cutting the Si—O bond, and therefore has an appropriate flexibility for the chemical bond of the bonding film 3. It is possible to grant.

Further, the irradiation time of ultraviolet rays is preferably about 1 second to 10 minutes, more preferably about 10 seconds to 5 minutes. With such an irradiation time, energy necessary and sufficient for imparting flexibility to the chemical bond of the bonding film 3 is imparted.
Moreover, the atmosphere when irradiating with ultraviolet rays is not particularly limited, but is preferably an inert gas atmosphere such as nitrogen gas or argon gas, and more preferably a dry inert gas atmosphere having a low water vapor content. In such an atmosphere, deterioration / deterioration due to oxidation of the bonding film 3 can be prevented, and a hydroxyl group or the like can be prevented from being bonded to the cut chemical bond in the bonding film 3.
In the present embodiment, only the second substrate 4 is permeable to ultraviolet rays. However, when the first substrate 2 is also permeable to ultraviolet rays, the bonded body is used. 5 may be irradiated with ultraviolet rays from both sides. In this case, the irradiation conditions (wavelength, irradiation time, etc.) of the ultraviolet rays applied to each surface may be the same or different.

  [5] Next, as shown in FIG. 2F, a load is applied (pressurized) to correct the bonded body 5 to a predetermined shape. And it hold | maintains for a fixed time in this state (shape correction state) (5th process). Thereby, in the bonding film 3, the chemical bond once cut in the above process is recombined while being held in the shape correction state. As a result, the bonding film 3 is hardened because its chemical bond is less flexible under a shape correction state. Further, as the chemical bond of the bonding film 3 has flexibility, the residual stress in the bonded body 5 is released and relaxed. Thereby, the joined body 5 which passed through this process is corrected to the target shape with the reduction of a residual stress. As a result, the dimensional accuracy of the joined body 5 can be improved. Moreover, since the obtained joined body 5 does not contain residual stress, the shape after correction can be maintained for a long time.

When the bonded body 5 is pressurized, a load may be applied in the thickness direction of the bonded body 5 using an appropriate jig or the like so that the bonded body 5 is corrected to a target shape. For example, when correcting the bonded body 5 in which the warp as shown in FIG. 2D has occurred to a flat plate shape that is the original shape of each of the substrates 1 and 2, as shown in FIG. The joined body 5 is sandwiched between two surface plates (jigs) 7 having a smooth surface. And if it pressurizes so that the joined body 5 may be compressed with the two surface plates 7, the high flatness of each surface plate 7 surface will be reflected in the shape of the joined body 5, and finally flatness (parallelism) Can be obtained. By using a platen 7 having a pressing surface that includes the joined body 5, it is possible to press the joined body 5 uniformly and correct its shape accurately.
Moreover, it is also possible to obtain the curved joined body 5 by using a jig having a curved surface with a predetermined curvature as required.

The time for holding the bonded body 5 in the shape correction state is not particularly limited, but is preferably 10 seconds or more, and more preferably 30 seconds or more. With such a holding time, recombination of the chemical bond is ensured, the flexibility of the chemical bond of the bonding film 3 is reduced, and the residual stress can be sufficiently reduced and the shape of the bonded body 5 can be sufficiently corrected. it can.
Further, when the bonded body 5 is held in a shape-corrected state, it is preferable to carry out while heating the bonded body 5. By heating, recombination of chemical bonds in the bonding film 3 is promoted, and the bonding film 3 can be cured in a shorter time. For this reason, it is possible to reduce the residual stress and correct the shape of the bonded body 5 in a shorter time.
In this case, the heating temperature of the joined body 5 is preferably about 25 to 100 ° C., more preferably about 50 to 100 ° C. Within such a temperature range, it is possible to reliably increase the bonding strength while preventing the bonded body 5 from being altered or deteriorated by heat.

Moreover, when performing such temperature control, the temperature control of the joined body 5 is performed by using the surface plate 7 provided with temperature changing means such as a heating means such as a heater or a cooling means such as a Peltier element or a heat exchanger. And pressurization can be performed efficiently and accurately.
Moreover, it is preferable that the pressure at the time of pressurizing the conjugate | zygote 5 is about 0.2-10 MPa, and it is more preferable that it is about 1-5 MPa.

Further, the atmosphere when the bonded body 5 is pressurized is not particularly limited, but is preferably an inert gas atmosphere such as nitrogen gas or argon gas, and more preferably a dry inert gas atmosphere or a reduced pressure with a low water vapor content. The atmosphere. In such an atmosphere, deterioration / deterioration due to oxidation of the bonding film 3 can be prevented, and a hydroxyl group or the like can be prevented from being bonded to the cut chemical bond in the bonding film 3.
In addition, it is preferable to perform this process, without leaving | separating as much time interval as possible after completion | finish of said process [4]. Specifically, it is preferably performed within 10 minutes, more preferably within 5 minutes. As a result, the above-described functions and effects are more remarkably exhibited.
As described above, the bonded body 5 (the bonded body of the present invention) having high dimensional accuracy and no residual stress is obtained.

Here, the bonding film 3 will be described in detail.
As described above, the bonding film 3 is formed by a plasma polymerization method. As shown in FIG. 3, the Si skeleton 301 including a siloxane (Si—O) bond 302 and having a random atomic structure, It has a leaving group 303 bonded to the Si skeleton 301. Such a bonding film 3 becomes a strong film that is difficult to be deformed due to the influence of the Si skeleton 301 including the siloxane bond 302 and having a random atomic structure. This is presumably because the crystallinity of the Si skeleton 301 becomes low, so that defects such as dislocations and misalignments at the grain boundaries are difficult to occur. For this reason, the bonding film 3 itself has high bonding strength, chemical resistance, and dimensional accuracy, and the finally obtained bonded body 5 also has high bonding strength, chemical resistance, and dimensional accuracy.

In such a bonding film 3, when energy is applied, the leaving group 303 is detached from the Si skeleton 301, and as shown in FIG. 4, active hands 304 are generated on the surface 35 and inside of the bonding film 3. It is. As a result, adhesiveness is developed on the surface of the bonding film 3. When such adhesiveness is developed, the bonding film 3 can be firmly and efficiently bonded to the second substrate 4 with high dimensional accuracy.
Note that the bond energy between the leaving group 303 and the Si skeleton 301 is smaller than the bond energy of the siloxane bond 302 in the Si skeleton 301. For this reason, the bonding film 3 selectively breaks the bond between the leaving group 303 and the Si skeleton 301 and prevents the leaving group 303 from being removed while preventing the Si skeleton 301 from being destroyed by the application of energy. Can be separated.

  Further, since the Si skeleton 301 in the bonding film 3 has a random atomic structure, when the shape is corrected after the chemical bond of the bonding film 3 is softened by irradiating ultraviolet rays, a new stress is applied. Can be corrected without incurring the occurrence of This is because the bonding film 3 formed by the plasma polymerization method has a higher degree of freedom in atomic arrangement than a film having high crystallinity. It is guessed that this is done.

  Further, such a bonding film 3 is a solid having no fluidity. For this reason, conventionally, the thickness and shape of the adhesive layer (bonding film 3) hardly change compared to a liquid or viscous liquid adhesive. Thereby, the dimensional accuracy of the joined body 5 becomes remarkably higher than the conventional one. Furthermore, since the time required for curing the adhesive is not required, strong bonding can be achieved in a short time.

  Note that, in the bonding film 3, among the atoms obtained by removing H atoms from all atoms constituting the bonding film 3, the total of the Si atom content and the O atom content is about 10 to 90 atomic%. Is preferable, and it is more preferable that it is about 20-80 atomic%. If Si atoms and O atoms are contained in the above-mentioned range, the bonding film 3 forms a strong network of Si atoms and O atoms, and the bonding film 3 itself becomes strong. In addition, the bonding film 3 exhibits particularly high bonding strength with respect to the first substrate 2 and the second substrate 4.

The abundance ratio of Si atoms and O atoms in the bonding film 3 is preferably about 3: 7 to 7: 3, and more preferably about 4: 6 to 6: 4. By setting the abundance ratio of Si atoms and O atoms to be within the above range, the stability of the bonding film 3 is increased, and the first substrate 2 and the second substrate 4 can be bonded more firmly. become able to.
The crystallinity of the Si skeleton 301 in the bonding film 3 is preferably 45% or less, and more preferably 40% or less. As a result, the Si skeleton 301 includes a sufficiently random atomic structure. For this reason, the characteristics of the Si skeleton 301 described above become obvious, and the dimensional accuracy and adhesiveness of the bonding film 3 become more excellent.

  Note that the crystallinity of the Si skeleton 301 can be measured by a general crystallinity measurement method, and specifically, a method of measuring based on the intensity of scattered X-rays in a crystal portion (X-ray method). , The method of obtaining from the intensity of the crystallization band of infrared absorption (infrared method), the method of obtaining based on the area under the differential curve of nuclear magnetic resonance absorption (nuclear magnetic resonance absorption method), It can be measured by a chemical method utilizing the difficulty.

  The bonding film 3 preferably contains Si—H bonds in the structure. This Si-H bond is generated in the polymer when the silane undergoes a polymerization reaction by the plasma polymerization method. At this time, if the Si-H bond inhibits the regular formation of the siloxane bond, Conceivable. For this reason, the siloxane bond is formed so as to avoid the Si—H bond, and the regularity of the atomic structure of the Si skeleton 301 is lowered. Thus, according to the plasma polymerization method, the Si skeleton 301 having a low crystallinity can be efficiently formed.

  On the other hand, the greater the Si—H bond content in the bonding film 3, the lower the crystallinity. Specifically, in the infrared absorption spectrum of the bonding film 3, when the intensity of the peak attributed to the siloxane bond is 1, the intensity of the peak attributed to the Si—H bond is about 0.001 to 0.2. It is preferable that it is about 0.002-0.05, and it is further more preferable that it is about 0.005-0.02. When the ratio of the Si—H bond to the siloxane bond is within the above range, the atomic structure in the bonding film 3 is relatively random. For this reason, when the peak intensity of the Si—H bond is within the above range with respect to the peak intensity of the siloxane bond, the bonding film 3 is particularly excellent in bonding strength, chemical resistance, and dimensional accuracy.

Further, as described above, the leaving group 303 bonded to the Si skeleton 301 acts to generate an active hand in the bonding film 3 by detaching from the Si skeleton 301. Therefore, although the leaving group 303 is relatively easily and uniformly desorbed by being given energy, it is securely bonded to the Si skeleton 301 so as not to be desorbed when no energy is given. It needs to be a thing.
In the film formation by the plasma polymerization method, the component of the source gas is polymerized to generate a Si skeleton 301 containing a siloxane bond and a residue bonded thereto. For example, this residue is a leaving group. 303.

  From this point of view, the leaving group 303 includes an H atom, a B atom, a C atom, an N atom, an O atom, a P atom, an S atom, and a halogen atom, or each of these atoms. What consists of at least 1 sort (s) selected from the group which consists of an atomic group arrange | positioned so that it may couple | bond with frame | skeleton 301 is used preferably. Such a leaving group 303 is relatively excellent in bond / elimination selectivity by energy application. For this reason, such a leaving group 303 can sufficiently satisfy the above-described necessity, and the adhesiveness of the bonding film 3 can be made higher.

Examples of the atomic group (group) arranged so that each atom as described above is bonded to the Si skeleton 301 include, for example, an alkyl group such as a methyl group and an ethyl group, and an alkenyl group such as a vinyl group and an allyl group. Aldehyde group, ketone group, carboxyl group, amino group, amide group, nitro group, halogenated alkyl group, mercapto group, sulfonic acid group, cyano group, isocyanate group and the like.
Among these groups, the leaving group 303 is particularly preferably an alkyl group. Since the alkyl group has high chemical stability, the bonding film 3 containing the alkyl group is excellent in weather resistance and chemical resistance.

Here, when the leaving group 303 is a methyl group (—CH ₃ ), the preferred content is defined as follows from the peak intensity in the infrared light absorption spectrum.
That is, in the infrared absorption spectrum of the bonding film 3, when the intensity of the peak attributed to the siloxane bond is 1, the intensity of the peak attributed to the methyl group is preferably about 0.05 to 0.45. More preferably, it is about 0.1 to 0.4, and more preferably about 0.2 to 0.3. Since the ratio of the peak intensity of the methyl group to the peak intensity of the siloxane bond is within the above range, it is necessary and sufficient in the bonding film 3 while preventing the methyl group from inhibiting the generation of the siloxane bond more than necessary. Since a number of active hands are generated, sufficient adhesiveness is generated in the bonding film 3. Further, the bonding film 3 exhibits sufficient weather resistance and chemical resistance due to the methyl group.
Examples of the constituent material of the bonding film 3 having such characteristics include a polymer containing a siloxane bond such as polyorganosiloxane and an organic group capable of forming a leaving group 303 bonded thereto.

The bonding film 3 made of polyorganosiloxane itself has excellent mechanical properties. In addition, it exhibits particularly excellent adhesion to many materials. Therefore, the bonding film 3 made of polyorganosiloxane adheres particularly firmly to the first substrate 2 and also exhibits a particularly strong adhesion force to the second substrate 4, and as a result, The first substrate 2 and the second substrate 4 can be firmly bonded.
Polyorganosiloxane usually exhibits water repellency (non-adhesiveness), but when given energy, it can easily desorb organic groups, changes to hydrophilicity, and exhibits adhesiveness. However, there is an advantage that the non-adhesiveness and the adhesiveness can be controlled easily and reliably.

  This water repellency (non-adhesiveness) is mainly due to the action of alkyl groups contained in the polyorganosiloxane. Therefore, the bonding film 3 made of polyorganosiloxane exhibits adhesiveness on the surface 35 when energy is applied thereto, and at the portion other than the surface 35, the above-described action / effect by the alkyl group is obtained. Has the advantage of being Therefore, such a bonding film 3 has excellent weather resistance and chemical resistance, and is effectively used, for example, in assembling an optical element or a droplet discharge head that is exposed to chemicals for a long time. It will be a thing.

  Further, among polyorganosiloxanes, those mainly composed of a polymer of octamethyltrisiloxane are preferred. The bonding film 3 mainly composed of a polymer of octamethyltrisiloxane is particularly excellent in adhesiveness. Moreover, since the raw material which has octamethyltrisiloxane as a main component is liquid at normal temperature and has an appropriate viscosity, there is also an advantage that it is easy to handle.

The average thickness of the bonding film 3 is preferably about 1 to 1000 nm, and more preferably about 2 to 800 nm. By setting the average thickness of the bonding film 3 within the above range, it is possible to bond them more firmly while preventing the dimensional accuracy of the bonded body 5 from significantly decreasing.
That is, when the average thickness of the bonding film 3 is less than the lower limit, sufficient bonding strength may not be obtained. On the other hand, when the average thickness of the bonding film 3 exceeds the upper limit, the dimensional accuracy of the bonded body 5 may be reduced.

Furthermore, if the average thickness of the bonding film 3 is within the above range, a certain degree of shape followability is ensured for the bonding film 3. For this reason, for example, even when unevenness is present on the bonding surface of the first substrate 2 (surface adjacent to the bonding film 3), it follows the shape of the unevenness depending on the height of the unevenness. The bonding film 3 can be deposited. As a result, the bonding film 3 can absorb the unevenness and reduce the height of the unevenness generated on the surface. And when the 1st board | substrate 2 and the 2nd board | substrate 4 are bonded together, both adhesiveness can be improved.
Note that the degree of the shape followability as described above becomes more significant as the thickness of the bonding film 3 increases. Therefore, the thickness of the bonding film 3 should be as large as possible in order to sufficiently ensure the shape following ability.

  The bonding film 3 has been described in detail above. Such a bonding film 3 is produced by a plasma polymerization method. According to the plasma polymerization method, the dense and homogeneous bonding film 3 can be efficiently produced. As a result, the bonding film 3 can be bonded particularly firmly to the second substrate 4. Furthermore, the bonding film 3 manufactured by the plasma polymerization method is maintained for a relatively long time in a state where energy is applied and activated. For this reason, the manufacturing process of the joined body 5 can be simplified and efficient.

Hereinafter, a method for producing the bonding film 3 will be described.
First, prior to explaining the method for producing the bonding film 3, a plasma polymerization apparatus used when the bonding film 3 is produced by performing plasma polymerization on the first substrate 2 will be described.
FIG. 5 is a longitudinal sectional view schematically showing a plasma polymerization apparatus used in the bonding method of the present invention. In the following description, the upper side in FIG. 5 is referred to as “upper” and the lower side is referred to as “lower”.

A plasma polymerization apparatus 100 shown in FIG. 5 includes a chamber 101, a first electrode 130 that supports the first substrate 2, a second electrode 140, and a power supply circuit that applies a high-frequency voltage between the electrodes 130 and 140. 180, a gas supply unit 190 that supplies gas into the chamber 101, and an exhaust pump 170 that exhausts the gas in the chamber 101. Among these parts, the first electrode 130 and the second electrode 140 are provided in the chamber 101. Hereinafter, each part will be described in detail.
The chamber 101 is a container that can keep the inside airtight, and is used with the inside being in a reduced pressure (vacuum) state. Therefore, the chamber 101 has pressure resistance that can withstand a pressure difference between the inside and the outside.

The chamber 101 shown in FIG. 5 has a substantially cylindrical chamber body whose axis is arranged along the horizontal direction, a circular side wall that seals the left opening of the chamber body, and a circle that seals the right opening. And side walls.
A supply port 103 is provided above the chamber 101, and an exhaust port 104 is provided below the chamber 101. A gas supply unit 190 is connected to the supply port 103, and an exhaust pump 170 is connected to the exhaust port 104.
In this embodiment, the chamber 101 is made of a highly conductive metal material and is electrically grounded via the ground wire 102.

The first electrode 130 has a plate shape and supports the first substrate 2.
The first electrode 130 is provided on the inner wall surface of the side wall of the chamber 101 along the vertical direction, whereby the first electrode 130 is electrically grounded via the chamber 101. As shown in FIG. 5, the first electrode 130 is provided concentrically with the chamber body.

An electrostatic chuck (suction mechanism) 139 is provided on the surface of the first electrode 130 that supports the first substrate 2.
With this electrostatic chuck 139, the first substrate 2 can be supported along the vertical direction as shown in FIG. Further, even if the first substrate 2 has a slight warp, the first substrate 2 can be subjected to a plasma treatment in a state where the warp is corrected by being attracted to the electrostatic chuck 139.

The second electrode 140 is provided to face the first electrode 130 with the first substrate 2 interposed therebetween. Note that the second electrode 140 is provided in a state of being separated (insulated) from the inner wall surface of the side wall of the chamber 101.
A high frequency power source 182 is connected to the second electrode 140 via a wiring 184. A matching box (matching unit) 183 is provided in the middle of the wiring 184. The wiring 184, the high-frequency power source 182 and the matching box 183 constitute a power circuit 180.
According to such a power supply circuit 180, since the first electrode 130 is grounded, a high frequency voltage is applied between the first electrode 130 and the second electrode 140. As a result, an electric field whose direction is reversed at a high frequency is induced in the gap between the first electrode 130 and the second electrode 140.

The gas supply unit 190 supplies a predetermined gas into the chamber 101.
A gas supply unit 190 shown in FIG. 5 stores a liquid storage unit 191 that stores a liquid film material (raw material liquid), a vaporizer 192 that vaporizes the liquid film material to change it into a gaseous state, and stores a carrier gas. And a gas cylinder 193. Each of these parts and the supply port 103 of the chamber 101 are connected by a pipe 194, and a mixed gas of a gaseous film material (raw material gas) and a carrier gas is supplied from the supply port 103 into the chamber 101. It is configured to supply.

The liquid film material stored in the liquid storage unit 191 is a raw material that is polymerized by the plasma polymerization apparatus 100 to form a polymer film on the surface of the first substrate 2.
Such a liquid film material is vaporized by the vaporizer 192 and is supplied into the chamber 101 as a gaseous film material (raw material gas). The source gas will be described in detail later.

The carrier gas stored in the gas cylinder 193 is a gas that is discharged due to the action of an electric field and introduced to maintain this discharge. Examples of such a carrier gas include Ar gas and He gas.
A diffusion plate 195 is provided near the supply port 103 in the chamber 101.
The diffusion plate 195 has a function of promoting the diffusion of the mixed gas supplied into the chamber 101. Thereby, the mixed gas can be dispersed in the chamber 101 with a substantially uniform concentration.

The exhaust pump 170 exhausts the inside of the chamber 101, and includes, for example, an oil rotary pump, a turbo molecular pump, or the like. Thus, by exhausting the chamber 101 and reducing the pressure, the gas can be easily converted into plasma. Further, contamination and oxidation of the first substrate 2 due to contact with the air atmosphere can be prevented, and reaction products resulting from the plasma treatment can be effectively removed from the chamber 101.
The exhaust port 104 is provided with a pressure control mechanism 171 that adjusts the pressure in the chamber 101. Thereby, the pressure in the chamber 101 is appropriately set according to the operation state of the gas supply unit 190.

Next, a method for producing the bonding film 3 on the first substrate 2 using the plasma polymerization apparatus 100 will be described.
FIG. 6 is a diagram (longitudinal sectional view) for explaining a method of producing the bonding film 3 on the first substrate 2. In the following description, the upper side in FIG. 6 is referred to as “upper” and the lower side is referred to as “lower”.
The bonding film 3 is obtained by supplying a mixed gas of a source gas and a carrier gas in a strong electric field, thereby polymerizing molecules in the source gas and depositing a polymer on the first substrate 2. Can do. Details will be described below.

First, the first substrate 2 is prepared, and the surface treatment as described above is performed on the upper surface 25 of the first substrate 2 as necessary.
Next, after the first substrate 2 is housed in the chamber 101 of the plasma polymerization apparatus 100 and sealed, the chamber 101 is depressurized by the operation of the exhaust pump 170.
Next, the gas supply unit 190 is operated to supply a mixed gas of the source gas and the carrier gas into the chamber 101. The supplied mixed gas is filled in the chamber 101 (see FIG. 6A).

Here, the ratio (mixing ratio) of the source gas in the mixed gas is slightly different depending on the type of the source gas and the carrier gas, the target film forming speed, and the like. For example, the ratio of the source gas in the mixed gas is 20 It is preferable to set to about -70%, and it is more preferable to set to about 30-60%. As a result, it is possible to optimize the conditions for formation (film formation) of the polymer film.
Further, the flow rate of the gas to be supplied is appropriately determined depending on the type of gas, the target film formation rate, the film thickness, etc., and is not particularly limited, but usually the flow rates of the source gas and the carrier gas are respectively , Preferably about 1 to 100 ccm, more preferably about 10 to 60 ccm.

Next, the power supply circuit 180 is activated, and a high frequency voltage is applied between the pair of electrodes 130 and 140. As a result, gas molecules existing between the pair of electrodes 130 and 140 are ionized to generate plasma. The molecules in the source gas are polymerized by the energy of the plasma, and the polymer is adhered and deposited on the first substrate 2 as shown in FIG. As a result, a bonding film 3 made of a plasma polymerization film is formed on the first substrate 2 (see FIG. 6C).
Further, the surface of the first substrate 2 is activated and cleaned by the action of plasma. For this reason, the polymer of the source gas is easily deposited on the surface of the first substrate 2, and the bonding film 3 can be stably formed. As described above, according to the plasma polymerization method, the adhesion strength between the first substrate 2 and the bonding film 3 can be further increased regardless of the constituent material of the first substrate 2.

Examples of the source gas include organosiloxanes such as methylsiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, octamethylcyclotetrasiloxane, and methylphenylsiloxane.
The plasma polymerized film obtained by using such a raw material gas, that is, the bonding film 3 is composed of a polymer obtained by polymerizing these raw materials, that is, a polyorganosiloxane.

In the plasma polymerization, the frequency of the high frequency applied between the pair of electrodes 130 and 140 is not particularly limited, but is preferably about 1 kHz to 100 MHz, and more preferably about 10 to 60 MHz.
Further, the power density of the high frequency is not particularly limited, and is preferably about 0.01~100W / cm ^2, more preferably about ^{0.1~50W / cm 2, 1~40W / cm} 2 More preferably, it is about. By setting the high-frequency power density within the above range, the Si skeleton 301 having a random atomic structure can be reliably secured while preventing the plasma gas from being added to the source gas more than necessary because the high-frequency power density is too high. Can be formed. That is, when the high-frequency output density is lower than the lower limit value, the molecules in the raw material gas cannot cause a polymerization reaction, and the bonding film 3 may not be formed. On the other hand, when the power density of the high frequency exceeds the upper limit, the structure that can be the leaving group 303 is separated from the Si skeleton 301 due to decomposition of the source gas or the like, and the leaving group in the resulting bonding film 3 is separated. There is a possibility that the content of 303 is lowered or the randomness of the Si skeleton 301 is lowered (regularity is increased).

Further, the pressure in the chamber 101 during film formation is preferably about 133.3 × 10 ^{−5 to} 1333 Pa (1 × 10 ^{−5 to} 10 Torr), and 133.3 × 10 ^{−4 to} 133.3 Pa ( More preferably, it is about 1 × 10 ^{−4 to} 1 Torr).
The raw material gas flow rate is preferably about 0.5 to 200 sccm, and more preferably about 1 to 100 sccm. On the other hand, the carrier gas flow rate is preferably about 5 to 750 sccm, and more preferably about 10 to 500 sccm.

The treatment time is preferably about 1 to 10 minutes, more preferably about 4 to 7 minutes.
Moreover, it is preferable that the temperature of the board | substrate 2 is 25 degreeC or more, and it is more preferable that it is about 25-100 degreeC.
The bonding film 3 is obtained as described above.

  Note that the bonding film 3 can transmit light. Further, the refractive index of the bonding film 3 can be adjusted by appropriately setting the formation conditions of the bonding film 3 (conditions during plasma polymerization, composition of raw material gas, etc.). Specifically, the refractive index of the bonding film 3 can be increased by increasing the high frequency power density during plasma polymerization, and conversely, the bonding can be achieved by decreasing the high frequency power density during plasma polymerization. The refractive index of the film 3 can be lowered.

  Specifically, according to the plasma polymerization method, the bonding film 3 having a refractive index range of about 1.35 to 1.6 is obtained. Since the refractive index of such a bonding film 3 is close to that of quartz or quartz glass, for example, it is suitably used when manufacturing an optical component having a structure in which the optical path penetrates the bonding film 3. Further, since the refractive index of the bonding film 3 can be adjusted, the bonding film 3 having a desired refractive index can be manufactured.

From this point of view, when optical components made of quartz or quartz glass are bonded to each other through the bonding film 3 having the refractive index in the above range, the difference in refractive index at the bonding interface is reduced, and the laminated optical system having high light transmittance. Parts can be obtained.
Further, since the bonding film 3 is close to the thermal expansion coefficient of quartz or quartz glass, the difference between these thermal expansion coefficients becomes small, and deformation after bonding can be suppressed.

<< Second Embodiment >>
Next, a second embodiment of the joining method of the present invention will be described.
FIG. 7 is a view (longitudinal sectional view) for explaining a second embodiment of the joining method of the present invention. In the following description, the upper side in FIG. 7 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, the bonding method according to the second embodiment will be described, but the description will focus on differences from the first embodiment, and description of similar matters will be omitted.

The bonding method according to the present embodiment is the same as that of the first embodiment except that energy is applied to the bonding film 3 after the first substrate 2 and the second substrate 4 are overlaid. .
That is, in the bonding method according to the present embodiment, the first substrate 2 and the second substrate 4 having transparency to ultraviolet light are prepared, and the bonding film 3 is formed on the surface of the first substrate 2. And a step of superimposing the first substrate 2 and the second substrate 4 so that the bonding film 3 and the second substrate 4 are in close contact with each other to obtain a temporary bonded body, and the bonding film 3 in the temporary bonded body Energy is applied to the first substrate 2 and the second substrate 4 to obtain a bonded body 5, and ultraviolet light is applied to the bonded body 5 from the second substrate 4 side. There are a step of irradiating and a step of correcting the shape of the bonded body 5 to a flat plate shape by holding the bonded body 5 in a state of being pressed from the front and back by the two surface plates 7. Hereinafter, each process of the joining method concerning this embodiment is demonstrated one by one.

[1] First, as in the first embodiment, a first substrate 2 and a second substrate 4 are prepared, and a bonding film 3 is formed on the surface of the first substrate 2 by a plasma polymerization method. (See FIG. 7A).
[2] Next, as shown in FIG. 7B, the first substrate 2 and the second substrate 4 are overlapped so that the surface 35 of the bonding film 3 and the second substrate 4 are in close contact with each other. A temporary joined body is obtained. In addition, in the state of this temporary joined body, since the 1st board | substrate 2 and the 2nd board | substrate 4 are not joined, it is possible to adjust the relative position with respect to the 2nd board | substrate 4 of the 1st board | substrate 2. it can. That is, these positions can be easily finely adjusted by shifting the positions of the temporary joined bodies. As a result, the positional accuracy of the joined body 5 can be increased.

[3] Next, energy is applied to the bonding film 3 in the temporary bonded body. When energy is applied to the bonding film 3, the bonding film 3 exhibits adhesiveness with the second substrate 4. Thereby, the 1st board | substrate 2 and the 2nd board | substrate 4 are joined, and the conjugate | zygote 5 shown in FIG.7 (d) is obtained.
Here, the energy applied to the bonding film 3 may be applied by any method. For example, a method of irradiating the bonding film 3 with energy rays, a method of heating the bonding film 3, a compressive force ( It is preferable to use at least one method of imparting physical energy). Since these methods can apply energy relatively easily and efficiently to the bonding film 3 in the temporary bonded body, they are suitable as energy applying methods.

Among these, as a method of irradiating the bonding film 3 with energy rays, the same method as in the first embodiment can be used.
In this case, the energy rays pass through the first substrate 2 or the second substrate 4 and are irradiated to the bonding film 3.
On the other hand, as shown in FIG. 7C, in the case where energy is applied to the bonding film 3 by heating the bonding film 3, the heating temperature is preferably set to about 25 to 100 ° C. It is more preferable to set the temperature to about 100 ° C. By heating at a temperature in such a range, it is possible to reliably activate the bonding film 3 while reliably preventing the substrates 2 and 4 from being altered or deteriorated by heat.

Further, the heating time may be a time that allows the leaving group 303 of the bonding film 3 to be removed. Specifically, if the heating temperature is within the above range, the heating time is about 1 to 30 minutes. preferable.
The bonding film 3 may be heated by any method, and can be heated by various methods such as a method using a heater, a method of irradiating infrared rays, and a method of contacting with a flame.
In addition, when using the method of irradiating infrared rays, it is preferable that the 1st board | substrate 2 or the 2nd board | substrate 4 is comprised with the material which has a light absorptivity. Thereby, the 1st board | substrate 2 or the 2nd board | substrate 4 irradiated with infrared rays generate | occur | produces heat | fever efficiently. As a result, the bonding film 3 can be efficiently heated.
Moreover, when using the method using a heater or the method of making it contact with a flame, it is preferable that the 1st board | substrate 2 or the 2nd board | substrate 4 is comprised with the material excellent in thermal conductivity. Thereby, heat can be efficiently transmitted to the bonding film 3 via the first substrate 2 or the second substrate 4, and the bonding film 3 can be efficiently heated.

Further, when a compressive force is applied to the bonding film 3, it is preferable to compress the first substrate 2 and the second substrate 4 with a pressure of about 0.2 to 10 MPa in a direction in which the first substrate 2 and the second substrate 4 approach each other. It is more preferable to compress at a pressure of about 5 MPa. Accordingly, it is possible to easily apply appropriate energy to the bonding film 3 simply by compressing, and the bonding film 3 exhibits sufficient adhesiveness with the second substrate 4. Although this pressure may exceed the upper limit, damage or the like may occur depending on the constituent materials of the first substrate 2 and the second substrate 4.
The time for applying the compressive force is not particularly limited, but is preferably about 10 seconds to 30 minutes. In addition, what is necessary is just to change suitably the time which provides compression force according to the magnitude | size of compression force. Specifically, the time for applying the compressive force can be shortened as the compressive force increases.
The bonded body 5 can be obtained as described above.
Thereafter, by performing the steps [4] and [5] in the first embodiment on the bonded body 5, the bonded body 5 (bonded body of the present invention) having high dimensional accuracy and no residual stress is obtained. .

<< Third Embodiment >>
Next, a third embodiment of the joining method of the present invention will be described.
FIG. 8 is a view (longitudinal sectional view) for explaining a third embodiment of the joining method of the present invention. In the following description, the upper side in FIG. 8 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, the bonding method according to the third embodiment will be described, but the description will focus on differences from the first embodiment and the second embodiment, and description of similar matters will be omitted.

The bonding method according to the present embodiment is the same as that described above except that bonding films are formed on the surfaces of the substrates 2 and 4 and the substrates 2 and 4 are bonded together so that the bonding films are in close contact with each other. This is the same as in the first embodiment.
That is, in the bonding method according to the present embodiment, the first substrate 2 and the second substrate 4 having transparency to ultraviolet rays are prepared, and the bonding film 31 is formed on the surface of the first substrate 2. , Forming a bonding film 32 on the surface of the second substrate 4, applying energy to each bonding film 31, 32 to activate each bonding film 31, 32, The step of bonding the first substrate 2 and the second substrate 4 so that the bonding films 31 and 32 are in close contact with each other to obtain the bonded body 5a, and the bonded body 5a from the second substrate 4 side. There are a step of irradiating ultraviolet rays and a step of correcting the shape of the bonded body 5a to a flat plate shape by holding the bonded body 5a pressed from the front and back surfaces with two surface plates. Hereinafter, each process of the joining method concerning this embodiment is demonstrated one by one.

[1] First, as in the first embodiment, a first substrate 2 and a second substrate 4 are prepared, and bonding films 31 and 32 are respectively formed on the surfaces of the substrates 2 and 4 by plasma polymerization. A film is formed (see FIG. 8A).
[2] Next, as shown in FIG. 8B, energy is applied to the bonding films 31 and 32, respectively. When energy is applied to each bonding film 31, 32, adhesiveness develops in each bonding film 31, 32.
In addition, as an energy provision method, the method similar to the said 1st Embodiment can be used.

Here, “activating” the bonding films 31 and 32 means that, as described above, the surfaces 351 and 352 of the bonding films 31 and 32 and the internal leaving groups 303 are released to form the Si skeleton 301. It means a state in which unterminated bonds (unbonded hands) are generated, a state in which these unbonded hands are terminated by a hydroxyl group (OH group), or a state in which these states are mixed.
Therefore, the active hand 304 refers to a dangling bond or a dangling bond terminated with a hydroxyl group.

[3] Next, as shown in FIG. 8 (c), the first substrate 2 and the second substrate 4 are bonded together so that the bonding films 31 and 32 exhibiting adhesiveness are in close contact with each other. The joined body 5a is obtained.
Here, in this step, the bonding films 31 and 32 are bonded to each other, and this bonding is assumed to be based on both or one of the following two mechanisms (i) and (ii). .

(I) For example, the case where hydroxyl groups are exposed on the surfaces 351 and 352 of the bonding films 31 and 32 will be described as an example. In this step, the first films 31 and 32 may be in close contact with each other. When the substrate 2 and the second substrate 4 are bonded together, the hydroxyl groups present on the surfaces 351 and 352 of the bonding films 31 and 32 attract each other by hydrogen bonding, and an attractive force is generated between the hydroxyl groups. It is assumed that the first substrate 2 and the second substrate 4 are joined by this attractive force.
Further, the hydroxyl groups attracting each other by this hydrogen bond are dehydrated and condensed depending on the temperature condition or the like. As a result, between the bonding films 31 and 32, the bonds in which the hydroxyl groups are bonded are bonded via oxygen atoms. Thereby, it is guessed that the 1st board | substrate 2 and the 2nd board | substrate 4 are joined more firmly.

  (Ii) When the first substrate 2 and the second substrate 4 are bonded together so that the bonding films 31 and 32 are in close contact with each other, the terminations generated on the surfaces 351 and 352 of the bonding films 31 and 32 and inside thereof. Bonds that have not been converted (unbonded hands) are recombined. Since this recombination occurs in a complicated manner so as to overlap (entangle) with each other, a network-like bond is formed at the bonding interface. As a result, the respective base materials (Si skeleton 301) constituting the bonding films 31 and 32 are directly bonded to each other, and the bonding films 31 and 32 are integrated with each other.

By the mechanism (i) or (ii) as described above, a joined body 5a as shown in FIG. 8D is obtained.
Thereafter, by performing the steps [4] and [5] in the first embodiment on the bonded body 5a, the bonded body 5a (bonded body of the present invention) having high dimensional accuracy and no residual stress is obtained. .

<< Fourth Embodiment >>
Next, a fourth embodiment of the joining method of the present invention will be described.
FIG. 9 is a view (longitudinal sectional view) for explaining a fourth embodiment of the joining method of the present invention. In the following description, the upper side in FIG. 9 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, the bonding method according to the fourth embodiment will be described, but the description will focus on differences from the first embodiment to the third embodiment, and description of similar matters will be omitted.

In the bonding method according to the present embodiment, only the predetermined region 350 of the bonding film 3 is selectively activated to partially connect the first substrate 2 and the second substrate 4 in the predetermined region 350. Except for joining, it is the same as in the first embodiment.
That is, in the bonding method according to the present embodiment, the first substrate 2 and the second substrate 4 having transparency to ultraviolet light are prepared, and the bonding film 3 is formed on the surface of the first substrate 2. A step of selectively applying energy to a predetermined region 350 of a part of the bonding film 3, the first substrate 2 and the second substrate 4 are bonded via the bonding film 3, and the bonded body 5. The step of irradiating the bonded body 5 with ultraviolet rays from the second substrate 4 side, and holding the bonded body 5 pressed from the front and back with two surface plates, And a step of correcting the shape into a flat plate shape. Hereinafter, each process of the joining method concerning this embodiment is demonstrated one by one.

[1] First, as in the first embodiment, a first substrate 2 and a second substrate 4 are prepared, and a bonding film 3 is formed on the surface of the first substrate 2 by a plasma polymerization method. (See FIG. 9A).
[2] Next, as shown in FIG. 9B, energy is selectively applied to a part of the predetermined region 350 in the surface 35 of the bonding film 3.
When energy is applied, the leaving group 303 is detached from the Si skeleton 301 in the predetermined region 350 in the bonding film 3 (see FIG. 3). Then, after the leaving group 303 is released, active hands 304 are generated on the surface 35 and inside of the bonding film 3 (see FIG. 4). As a result, adhesiveness with the second substrate 4 appears in the predetermined region 350 of the bonding film 3. On the other hand, adhesiveness is hardly expressed in regions other than the predetermined region 350 of the bonding film 3.

The bonding film 3 in such a state can be partially bonded to the second substrate 4 in the predetermined region 350.
In order to selectively apply energy to the predetermined region 350, as shown in FIG. 9B, a mask 6 having a window 61 corresponding to the predetermined region 350 is used, and bonding is performed via the mask 6. It suffices to apply energy to the film 3.

[3] Next, as shown in FIG. 9C, the first substrate 2 and the second substrate 2 are adhered so that the bonding film 3 that exhibits adhesiveness in the predetermined region 350 and the second substrate 4 are in close contact with each other. The substrate 4 is bonded together. Thereby, the joined body 5b shown in FIG.
The bonded body 5b thus obtained does not bond the entire opposing surfaces of the first substrate 2 and the second substrate 4, but partially bonds only a part of the region (predetermined region 350). It will be. At the time of bonding, the region to be bonded can be easily selected only by controlling the region to which energy is applied to the bonding film 3. Thereby, by controlling the area of the predetermined region 350, the bonding strength of the bonded body 5b can be easily adjusted. As a result, for example, a joined body 5b that can easily separate the joined portions is obtained.

Further, by appropriately controlling the area and shape of the joint portion (predetermined region 350) between the first substrate 2 and the second substrate 4 shown in FIG. 9D, local concentration of stress generated in the joint portion is alleviated. can do. Thereby, even when the thermal expansion coefficient difference between the first substrate 2 and the second substrate 4 is large, these can be reliably bonded.
Further, in the bonded body 5 b, a slight gap is generated (remains) in a region other than the predetermined region 350 to be bonded in the gap between the bonding film 3 and the second substrate 4. Therefore, by appropriately adjusting the shape of the predetermined region 350, a closed space, a flow path, and the like can be easily formed between the bonding film 3 and the second substrate 4.
The bonded body 5b can be obtained as described above.
Thereafter, by performing the steps [4] and [5] in the first embodiment on the bonded body 5b, the bonded body 5b (bonded body of the present invention) with high dimensional accuracy and no residual stress is obtained. .

«Fifth embodiment»
Next, a fifth embodiment of the joining method of the present invention will be described.
FIG. 10 is a view (longitudinal sectional view) for explaining a fifth embodiment of the joining method of the present invention. In the following description, the upper side in FIG. 10 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, the bonding method according to the fifth embodiment will be described. The description will focus on differences from the first to fourth embodiments, and the description of the same matters will be omitted.

In the bonding method according to the present embodiment, the first substrate 2 and the second substrate 4 are bonded to each other by forming the bonding film 3a only on a part of the predetermined region 350 in the upper surface 25 of the first substrate 2. The second embodiment is the same as the first embodiment except that the predetermined region 350 is partially joined.
That is, in the bonding method according to the present embodiment, the first substrate 2 and the second substrate 4 that is transmissive to ultraviolet light are prepared, and a part of the predetermined region 350 on the upper surface 25 of the first substrate 2. Only the step of forming the bonding film 3a only, the step of bonding the first substrate 2 and the second substrate 4 via the bonding film 3a to obtain the bonded body 5c, The step of irradiating ultraviolet rays from the side of the substrate 4 and the step of correcting the shape of the joined body 5c into a flat plate shape by holding the joined body 5c pressed from the front and back with two surface plates. Hereinafter, each process of the joining method concerning this embodiment is demonstrated one by one.

[1] First, in the same manner as in the first embodiment, the first substrate 2 and the second substrate 4 are prepared and bonded to only a part of the predetermined region 350 on the upper surface 25 of the first substrate 2. A film 3a is formed (see FIG. 10A).
In order to selectively form the bonding film 3a in the predetermined region 350, as shown in FIG. 10A, a mask 6 having a window portion 61 corresponding to the predetermined region 350 is used. A plasma polymerization film may be formed by a plasma polymerization method.

[2] Next, as shown in FIG. 10B, energy is applied to the bonding film 3a. When energy is applied, adhesiveness develops in the bonding film 3a.
[3] Next, as shown in FIG. 10C, the first substrate 2 and the second substrate 4 are bonded so that the bonding film 3a exhibiting adhesiveness and the second substrate 4 are in close contact with each other. The bonded body 5c shown in FIG.

  The bonded body 5c thus obtained does not bond the entire opposing surfaces of the first substrate 2 and the second substrate 4 but partially bonds only a part of the region (predetermined region 350). It will be. When forming the bonding film 3a, the region to be bonded can be easily selected only by controlling the formation region. Thereby, for example, the bonding strength of the bonded body 5c can be easily adjusted by controlling the area of the region (predetermined region 350) where the bonding film 3a is formed. As a result, for example, a joined body 5c that can easily separate the joined portions is obtained.

Further, by appropriately controlling the area and shape of the joint (predetermined region 350) between the first substrate 2 and the second substrate 4 shown in FIG. 10D, local concentration of stress generated in the joint is alleviated. can do. Thereby, for example, even when the difference in coefficient of thermal expansion between the first substrate 2 and the second substrate 4 is large, the first substrate 2 and the second substrate 4 can be reliably bonded.
Further, a gap 3 c having a separation distance corresponding to the thickness of the bonding film 3 a is formed in a region other than the predetermined region 350 between the first substrate 2 and the second substrate 4 of the bonded body 5 c. (See FIG. 10D). Accordingly, by appropriately adjusting the shape of the predetermined region 350 and the thickness of the bonding film 3a, a closed space, a flow path, or the like having a desired shape can be easily formed between the first substrate 2 and the second substrate 4. Can be formed.
The bonded body 5c can be obtained as described above.
Thereafter, by performing the steps [4] and [5] in the first embodiment on the bonded body 5c, the bonded body 5c (bonded body of the present invention) with high dimensional accuracy and no residual stress is obtained. .

<< Sixth Embodiment >>
Next, a sixth embodiment of the joining method of the present invention will be described.
FIG. 11 is a view (longitudinal sectional view) for explaining a sixth embodiment of the joining method of the present invention. In the following description, the upper side in FIG. 11 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, the bonding method according to the sixth embodiment will be described. The description will focus on the differences from the first to fifth embodiments, and the description of the same matters will be omitted.

The bonding method according to this embodiment is the same as that of the first embodiment except that, in the fourth step, only a predetermined region 350 of the bonded body 5 is irradiated with ultraviolet rays.
That is, in the bonding method according to the present embodiment, the first substrate 2 and the second substrate 4 having transparency to ultraviolet light are prepared, and the bonding film 3 is formed on the surface of the first substrate 2. And bonding the first substrate 2 and the second substrate 4 via the bonding film 3 to obtain the bonded body 5, the second portion of the bonded body 5 only in a predetermined region 350. There are a step of irradiating ultraviolet rays from the substrate 4 side, and a step of correcting the shape of the bonded body 5 to a flat plate shape by holding the bonded body 5c pressed from the front and back with two surface plates. Hereinafter, each process of the joining method concerning this embodiment is demonstrated one by one.

[1] First, as in the first embodiment, a first substrate 2 and a second substrate 4 are prepared, and a bonding film 3 is formed on the surface of the first substrate 2 by a plasma polymerization method. To do.
[2] Next, energy is applied to the bonding film 3. When energy is applied, the bonding film 3 exhibits adhesiveness.
[3] Next, the first substrate 2 and the second substrate 4 are bonded together so that the bonding film 3 exhibiting adhesiveness and the second substrate 4 are in close contact with each other, as shown in FIG. A joined body 5 is obtained.

[4] Next, as shown in FIG. 11B, only a part of the predetermined region 350 in the joined body 5 is irradiated with ultraviolet rays from the second substrate 4 side. Thereby, a part of the chemical bond in the predetermined region 350 in the bonding film 3 is selectively cut, and the flexibility of the chemical bond in the predetermined region 350 is improved. As a result, the residual stress in the bonded body 5 is released.
In order to selectively irradiate the predetermined region 350 with ultraviolet rays, as shown in FIG. 11B, a mask 6 having a window portion 61 corresponding to the predetermined region 350 is used, and bonding is performed via the mask 6. The film 3 may be irradiated with ultraviolet rays.

[5] Next, as shown in FIG. 11 (c), the joined body 5 is compressed by the two surface plates 7. Thereby, the high flatness of each surface plate 7 surface is reflected in the shape of the joined body 5, and finally the joined body 5 with high flatness (parallelism) can be obtained.
In such a method, some of the chemical bonds in the predetermined region 350 in the bonded body 5 are selectively cut. As a result, only in this portion, the flexibility of the chemical bond of the bonding film 3 is improved, thereby releasing the residual stress in this portion. Therefore, according to the present embodiment, the residual stress in a specific portion can be selectively reduced, so that the ultraviolet irradiation region can be minimized. As a result, it is possible to suppress deterioration and deterioration of the substrates 2 and 4 due to ultraviolet irradiation.

The joining method according to each of the embodiments as described above can be used to join various members.
Examples of members used for such bonding include semiconductor elements such as transistors, diodes, and memories, piezoelectric elements such as crystal oscillators, optical elements such as reflectors, optical lenses, diffraction gratings, and optical filters. , Photoelectric conversion elements such as solar cells, semiconductor substrates and semiconductor elements mounted thereon, insulating substrates and wiring or electrodes, inkjet recording heads, microreactors, microelectromechanical system (MEMS) components such as micromirrors, pressure Sensor parts such as sensors, acceleration sensors, package parts for semiconductor elements and electronic parts, magnetic recording media, magneto-optical recording media, recording media such as optical recording media, liquid crystal display elements, organic EL elements, electrophoretic display elements Such display element parts, fuel cell parts, and the like.

<Optical element>
Here, an embodiment when the joined body of the present invention is applied to an optical element will be described.
FIG. 12 is a perspective view showing a wave plate (optical element) obtained by applying the joined body of the present invention.
The wave plate 9 shown in FIG. 12 is a “½ wave plate” that gives a phase difference of ½ wavelength to transmitted light, and two crystal plates 91 and 92 having birefringence are respectively provided. Are bonded so that their optical axes are orthogonal to each other. Examples of the material having birefringence include inorganic materials such as quartz, calcite, MgF ₂ , YVO ₄ , TiO ₂ , and LiNbO ₃ , and organic materials such as polycarbonate.

When light passes through such a wave plate 9, the light is separated into a polarization component parallel to the optical axis and a polarization component perpendicular to the optical axis. The separated light is delayed on one side based on the refractive index difference associated with the birefringence of the crystal plates 91 and 92, and the phase difference described above is generated.
By the way, since the accuracy of the phase difference given to the transmitted light by the wave plate 9 and the transmittance of the wave plate 9 depend on the accuracy of the plate thickness of each crystal plate 91, 92, the plate of each crystal plate 91, 92. The thickness needs to be controlled with high accuracy.
In addition, since the gap between the crystal plate 91 and the crystal plate 92 also affects the phase of transmitted light, the gap between the crystal plate 91 and the crystal plate 92 is strictly controlled, and the gap is It must be firmly bonded so that it does not change.

  Therefore, in the present invention, the joined body of the present invention is applied to the wave plate 9. Thereby, the wave plate 9 in which the crystal plate 91 and the crystal plate 92 are firmly bonded via the bonding film can be easily obtained. Since this bonding film is very thin, the influence on the light transmitted through the wave plate 9 can be suppressed. In addition, since the refractive index of the bonding film is close to that of quartz generally used as a constituent material of each of the crystal plates 91 and 92, light loss at the bonding interface is reduced, and a decrease in transmittance of the wave plate 9 is suppressed. can do.

Further, when the wave plate 9 is manufactured, the crystal plate 91 and the crystal plate 92 are bonded to each other by the above-described bonding method of the present invention to obtain a laminated body (joined body). Along with the difference in coefficient of thermal expansion between the plates 91 and 92 and the bonding film, deformation such as residual stress and warpage accompanying it occurs. According to the bonding method of the present invention, since the shape can be corrected while reducing the generated residual stress, the wave plate 9 having high dimensional accuracy can be finally obtained. Such a wave plate 9 has high accuracy of the phase difference given to the transmitted light and high transmittance.
The wave plate 9 may be a quarter wave plate, a 1/8 wave plate or the like in addition to the half wave plate.
Examples of the optical element include an optical filter such as a polarizing filter, a compound lens such as an optical pickup, a prism, a diffraction grating, and the like in addition to the wave plate.

As described above, the bonding method, the bonded body, and the optical element of the present invention have been described based on the illustrated embodiments, but the present invention is not limited thereto.
For example, the joining method of the present invention may be any one or a combination of two or more of the above embodiments.
Moreover, in the joining method of this invention, you may add the process of 1 or more arbitrary objectives as needed.
In each of the above embodiments, the method of bonding two substrates, that is, the substrate and the counter substrate, is described. However, when three or more substrates are bonded, the bonding method of the present invention is used. May be.

Next, specific examples of the present invention will be described.
1. Manufacture of joined body In the following, in the examples, reference examples, and comparative examples, a plurality of joined bodies were manufactured.

Example 1
First, a quartz substrate having a length of 20 mm × width 20 mm × an average thickness of 2 mm was prepared as a first substrate, and a quartz substrate having a length of 20 mm × width 20 mm × an average thickness of 1 mm was prepared as a second substrate. Note that these quartz substrates are all subjected to optical polishing.
Next, each substrate was accommodated in the chamber 101 of the plasma polymerization apparatus 100 shown in FIG. 5, and surface treatment with oxygen plasma was performed.
Next, a plasma polymerization film having an average thickness of 200 nm was formed on the surface subjected to the surface treatment. The film forming conditions are as shown below.

<Film formation conditions>
-Source gas composition: Octamethyltrisiloxane-Source gas flow rate: 50 sccm
Carrier gas composition: Argon Carrier gas flow rate: 100 sccm
・ High frequency power output: 100W
・ High frequency output density: 25 W / cm ²
-Chamber pressure: 1 Pa (low vacuum)
・ Processing time: 15 minutes ・ Substrate temperature: 20 ° C.

Thereby, a plasma polymerization film was formed on each substrate.
The plasma polymerized film thus formed is composed of a polymer of octamethyltrisiloxane (raw material gas), and includes a Si skeleton including a siloxane bond and a random atomic structure, and an alkyl group (desorbed). Group). Further, the crystallinity of the plasma polymerized film was measured by an infrared absorption method. As a result, the degree of crystallinity of the plasma polymerized film was in the range of 5 to 30% although there was some variation depending on the measurement location.

Next, each plasma polymerization film obtained was subjected to plasma treatment under atmospheric pressure. Note that argon gas was used as a processing gas in the plasma processing.
Next, one minute after applying the plasma treatment, the respective substrates were overlapped so that the plasma polymerization films were in contact with each other. Thereby, the joined body was obtained.
Next, the obtained bonded body was irradiated with ultraviolet rays under the following conditions from the second substrate side.

<Ultraviolet irradiation conditions>
-Atmospheric gas composition: Air (air)
・ Atmospheric gas temperature: 20 ℃
・ Atmospheric gas pressure: Atmospheric pressure (100 kPa)
UV wavelength: 172 nm
・ UV irradiation time: 120 seconds

Next, one minute after irradiation with ultraviolet rays, the joined body was pressed in a state where the joined body was sandwiched between two surface plates, and kept in this state at a temperature of 50 ° C. for 60 seconds. The surface plate used is one having the surface polished to the same degree as the surface of the quartz substrate described above, and has a flatness prescribed in JIS B 7513.
As described above, the residual stress in the joined body was reduced and the shape of the joined body was corrected.

(Example 2)
A joined body was obtained in the same manner as in Example 1 except that ultraviolet rays were irradiated from both sides of the joined body. The condition for pressing the joined body was 60 seconds at room temperature.
(Reference example)
A joined body was obtained in the same manner as in Example 1 except that ultraviolet irradiation and weighting on the joined body were omitted.
(Comparative example)
A joined body was obtained in the same manner as in Example 1 except that the first substrate and the second substrate were bonded using an epoxy optical adhesive.

2. 2. Evaluation of Bonded Body 2.1 Evaluation of Bonding Strength (Split Strength) The bonding strength was measured for each of the bonded bodies obtained in each Example, Reference Example, and Comparative Example.
The bonding strength was measured by measuring the strength immediately before peeling off each substrate. Further, the measurement of the bonding strength was performed immediately after bonding and after repeating the temperature cycle of −40 ° C. to 125 ° C. 100 times after bonding.
As a result, the joined bodies obtained in each Example and Reference Example had sufficient joint strength both immediately after joining and after temperature cycling.
On the other hand, the bonded body obtained in the comparative example had sufficient bonding strength immediately after bonding, but the bonding strength decreased after the temperature cycle.

2.2 Evaluation of dimensional accuracy The dimensional accuracy (parallelism) in the thickness direction was measured for each of the joined bodies obtained in each of the examples, reference examples, and comparative examples.
Specifically, the thickness of the four corners of the joined body was measured with a micro gauge. And the relative inclination of both surfaces of a joined body was computed based on the difference of the thickness of four corners.
As a result, the joined bodies obtained in each Example had a parallelism of ± 1 second or less, and the variation in parallelism was small among a plurality of joined bodies.
On the other hand, the joined bodies obtained in the reference example and the comparative example had a parallelism of ± 1 second or more, and there was a large variation in parallelism between the joined bodies.

2.3 Evaluation of Light Transmittance The light transmittance (wavelength 405 nm) in the thickness direction was measured for each of the joined bodies obtained in each Example, Reference Example, and Comparative Example.
As a result, all the joined bodies had almost the same light transmittance (99.5% or more).
Moreover, after continuously irradiating light with a wavelength of 405 nm and an output of 100 mW in a 70 ° C. environment for 1000 hours, and measuring the light transmittance again as described above, the joined bodies obtained in each Example and Reference Example are as follows. While excellent light transmittance of 99.5% or more was exhibited, the light transmittance of the joined body obtained in the comparative example was reduced to 90% or less.

It is a figure (longitudinal sectional view) for demonstrating 1st Embodiment of the joining method of this invention. It is a figure (longitudinal sectional view) for demonstrating 1st Embodiment of the joining method of this invention. In the joining method of this invention, it is the elements on larger scale which show the state before energy provision of a joining film | membrane. In the joining method of this invention, it is the elements on larger scale which show the state after the energy provision of a joining film | membrane. It is a longitudinal cross-sectional view which shows typically the plasma polymerization apparatus used for the joining method of this invention. It is a figure (longitudinal sectional view) for demonstrating the method of producing a bonding film on the 1st substrate. It is a figure (longitudinal sectional view) for demonstrating 2nd Embodiment of the joining method of this invention. It is a figure (longitudinal section) for explaining a 3rd embodiment of the joining method of the present invention. It is a figure (longitudinal sectional view) for demonstrating 4th Embodiment of the joining method of this invention. It is a figure (longitudinal sectional view) for demonstrating 5th Embodiment of the joining method of this invention. It is a figure (longitudinal sectional view) for demonstrating 6th Embodiment of the joining method of this invention. It is a perspective view which shows the wavelength plate (optical element) obtained by applying the conjugate | zygote of this invention.

Explanation of symbols

  2... First substrate 25... Upper surface 3, 3 a, 31, 32... Bonding film 301... Si skeleton 302. , 352 ... surface 350 ... predetermined region 4 ... second substrate 5, 5a, 5b, 5c ... joined body 6 ... mask 61 ... window part 7 ... surface plate 100 ... plasma polymerization apparatus 101 ... ... Chamber 102 ... Grounding wire 103 ... Supply port 104 ... Exhaust port 130 ... First electrode 140 ... Second electrode 139 ... Electrostatic chuck 170 ... Pump 171 ... Pressure control mechanism 180 ... Power supply circuit 182 ... High frequency power supply 183 ... Matching box 184 ... Wiring 190 ... Gas supply part 191 ... Liquid storage part 192 ... Vaporizer 193 ... Gas cylinder 19 ...... pipe 195 ...... diffusion plate 9 ...... wavelength plates 91 and 92 ...... crystal plate

Claims (29)

First and second substrates, at least one of which is transparent to ultraviolet rays, are prepared, and random atoms including siloxane (Si—O) bonds are formed on the surface of the first substrate by plasma polymerization. A first step of forming a bonding film including a Si skeleton having a structure and a leaving group bonded to the Si skeleton;
A second step in which energy is imparted to the bonding film, and the leaving group present at least near the surface of the bonding film is released from the Si skeleton, thereby exhibiting adhesiveness;
A third step of bonding the first substrate and the second substrate via the bonding film to obtain a bonded body;
A fourth step of irradiating the bonded body with ultraviolet rays from the side of the first substrate and the second substrate having transparency to the ultraviolet rays, and
And a fifth step of pressurizing the bonded body irradiated with the ultraviolet rays to correct it into a predetermined shape.   2. The bonding method according to claim 1, wherein a sum of a content ratio of Si atoms and a content ratio of O atoms among atoms obtained by removing H atoms from all atoms constituting the bonding film is 10 to 90 atomic%.   The bonding method according to claim 1 or 2, wherein the abundance ratio of Si atoms to O atoms in the bonding film is 3: 7 to 7: 3.   The bonding method according to claim 1, wherein the crystallinity of the Si skeleton is 45% or less.   The bonding method according to claim 1, wherein the bonding film includes a Si—H bond.   In the infrared light absorption spectrum of the bonding film including the Si—H bond, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the Si—H bond is 0.001 to 0.2. The joining method according to claim 5.   The leaving group includes an H atom, a B atom, a C atom, an N atom, an O atom, a P atom, an S atom, and a halogen atom, or an atomic group arranged so that each of these atoms is bonded to the Si skeleton. The joining method according to claim 1, comprising at least one selected from the group consisting of:   The bonding method according to claim 7, wherein the leaving group is an alkyl group.   In the infrared light absorption spectrum of the bonding film containing a methyl group as the leaving group, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the methyl group is 0.05 to 0.45. The joining method according to claim 8.   The bonding method according to claim 1, wherein the bonding film has an active hand after the leaving group existing at least near the surface thereof is released from the Si skeleton.   The bonding method according to claim 10, wherein the active hand is a dangling hand or a hydroxyl group.   The bonding method according to claim 1, wherein the bonding film is made of polyorganosiloxane as a main material.   The bonding method according to claim 12, wherein the polyorganosiloxane is mainly composed of a polymer of octamethyltrisiloxane. The bonding method according to claim 1, wherein, in the plasma polymerization method, a high-frequency power density when generating plasma is 0.01 to 100 W / cm ² .   The bonding method according to claim 1, wherein an average thickness of the bonding film is 1-1000 nm.   The bonding method according to claim 1, wherein the bonding film is a solid having no fluidity.   The bonding method according to claim 1, wherein a refractive index of the bonding film is 1.35 to 1.6.   The bonding method according to any one of claims 1 to 17, wherein a substrate having transparency to ultraviolet rays among the first substrate and the second substrate is made of quartz glass or quartz.   The bonding method according to claim 1, wherein the wavelength of the ultraviolet light irradiated in the fourth step is 120 to 200 nm.   The ultraviolet ray irradiated in the fourth step has energy capable of cutting a chemical bond other than a Si-O bond without cutting a Si-O bond in the bonding film. The joining method according to any one of the above.   21. The bonding method according to claim 1, wherein the irradiation time of the ultraviolet ray in the fourth step is 1 second to 10 minutes.   The joining method according to any one of claims 1 to 21, wherein in the fifth step, the time for holding the joined body in a state of being corrected to a predetermined shape is 10 seconds or more.   The joining method according to any one of claims 1 to 22, wherein the joined body is heated and held in a state where the joined body is corrected to a predetermined shape. The pressing of the joined body in the fifth step is performed by pressing the pressing surface against the joined body using a jig having a pressing surface that includes the joined body.
The joining method according to claim 1, wherein the joined body is corrected by being deformed along a pressing surface of the jig.   The application of energy is at least one of a method of irradiating the bonding film with energy rays, a method of heating the bonding film, a method of applying a compressive force to the bonding film, and a method of exposing the bonding film to plasma. The joining method according to claim 1, wherein the joining method is performed by two methods.   The bonding method according to claim 1, wherein the energy is applied in an air atmosphere. In the first step, a bonding film similar to the bonding film is formed on the surface of the second substrate,
In the second step, after applying energy to the bonding films, in the third step, the bonding films are brought into close contact with each other so that the first substrate and the second substrate are bonded. The joining method according to any one of claims 1 to 26, wherein the joined body is obtained by joining. It has two substrates, these are joined by the joining method according to any one of claims 1 to 27,
A joined body characterized by having no residual stress inside.   An optical element comprising the joined body according to claim 28.

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