Composite base plate material and method for producing the same

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a composite substrate material in which two or more substrates are bonded to each other, and a method for producing the same.

【0002】

[Conventional technology]

Conventionally, optical crystals such as laser crystals, light wavelength conversion crystals, and quartz glass mirrors, or optical substrates are joined to form a composite material. As a bonding method in that case, a method of bonding optical crystals to each other or optical substrates to each other using an optical adhesive or heat-sealing at a high temperature is widely known.

【0003】

However, bonding with an optical adhesive causes optical scattering and reflection loss, and further, there is a problem that the bonding portion lacks reliability for a long period of time. Especially for the optical member arranged in the laser cavity, these problems become even more remarkable.

【0004】

On the other hand, since the method of heat fusion is limited to a limited combination of materials, there is a problem that it can be applied only to some applications.

【0005】

Therefore, in recent years, a method of joining dissimilar materials called a wafer bonding technique has attracted attention. In this technique, for example, as shown in JP-A-6-90061, single crystal and polycrystalline wafers are mirror-finished, and the mirror surfaces are washed to be free of dust and organic substances to make them hydrophilic. , Both are heated in a clean atmosphere in contact with each other.

【0006】

[Problems to be Solved by the Invention]

According to the above wafer bonding technology, it is possible to form a composite substrate material having high bonding strength, but on the other hand, this technology requires a wet treatment for cleaning the substrate, which complicates the manufacturing process. The problem is recognized.

【0007】

The present invention has been made in view of the above circumstances, and can produce a composite substrate material having high bonding strength, long-term reliability of the bonded portion, and excellent environmental temperature resistance without requiring wet treatment. The purpose is to provide a method.

【0008】

Another object of the present invention is to provide a composite substrate material having high bonding strength as described above, and also having excellent long-term reliability and environmental temperature resistance of the bonded portion.

【0009】

[Means for solving problems]

In the method for producing a composite substrate material according to the present invention, a functional film having a photocatalytic effect is provided on each surface of two or more substrate materials, and the functional film is irradiated with light in the absorption wavelength range, and then the functional film is provided. It is characterized in that these substrate materials are bonded via a film.

【0010】

The above-mentioned functional film is TiO.₂A film containing the above can be preferably used, and in that case, it is desirable to apply ultraviolet light as the light to irradiate the film. When a film other than the functional film is also formed on the surface of the substrate material, the functional film is formed on the uppermost layer.

【0011】

On the other hand, the composite substrate material according to the present invention is characterized in that it is produced by each of the above-mentioned methods.

【0012】

More specifically, the composite substrate material according to the present invention is a functional film in which two or more substrate materials have a photocatalytic effect, for example, TiO.₂It is bonded via a functional membrane containing.

【0013】

As the functional film, a film that also functions as an antireflection film is preferably used. Further, this functional film may have a photocatalytic effect and may be formed thin enough to be optically negligible.

【0014】

[Effect of the invention]

TiO₂A functional film having a photocatalytic effect, such as a metal oxide film typified by the above, exhibits a photocatalytic effect when irradiated with light in the absorption wavelength range, and almost completely decomposes organic substances and the like adhering to the substrate surface. Creates a super-hydrophilic state. After this state, when the surfaces of the substrate materials are bonded to each other and the substrate materials are weighted and heated, these substrate materials are bonded with high bonding strength. Moreover, the joint has excellent long-term reliability and environmental temperature resistance.

【0015】

Since the method for producing a composite substrate material according to the present invention does not require a wet treatment, the above-mentioned effect can be obtained extremely easily.

【0016】

In particular, when a functional film that also functions as an antireflection film is used, it is possible to obtain a composite substrate material having virtually no or extremely low reflection loss at the joint surface. Further, when the functional film is formed thin enough to be optically negligible, it is possible to obtain a composite substrate material having virtually no or extremely low scattering loss at the joint surface.

【0017】

By doing so, it is possible to easily and stably realize a value of, for example, a reflectance of about 0.2% or less on the joint surface of a plurality of optical substrates (crystals), and a laser crystal, a light wavelength conversion crystal, or another crystal in a solid-state laser or the like. Can also be directly joined. Thereby, according to the present invention, it is also possible to provide an ultra-small solid-state laser having stable performance.

【0018】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a manufacturing process of a composite substrate material according to the first embodiment of the present invention.

【0019】

First, as shown in Fig. (1), two Si wafers 10 and 20 were prepared as substrate materials, and TiO, which is a functional film having a photocatalytic effect, was formed on each of the mirror-finished surfaces 10a and 20a.₂Thin films 11 and 21 are formed. In this example, the thicknesses of the Si wafers 10 and 20 are both 300 μm. Also TiO₂The thin films 11 and 21 can be formed by, for example, a sputtering or a sol-gel method.

【0020】

Next, as shown in Fig. (2), TiO₂The surfaces of the thin films 11 and 21 are irradiated with ultraviolet light 30 having a wavelength of 380 nm or less. Then TiO₂The photocatalytic effect of the thin films 11 and 21 is exhibited, and the organic substances and the like adhering to the surfaces 10a and 20a of the Si wafers 10 and 20 are almost completely decomposed to create a superhydrophilic state.

【0021】

Immediately after that, the surfaces 10a and 20a are bonded to each other as shown in Fig. (3), and then the Si wafers 10 and 20 are weighted and heated as shown in Fig. (4). The force applied in this load is, for example, 500 g / cm.²It is said to be a degree. The heating condition is, for example, 300 ° C for 1 hour.

【0022】

After that, the wafer bonding is completed by cooling and removing the load. When the bonding strength of the bonded Si wafers 10 and 20 was confirmed with a push-pull gauge, it was 2 kg / cm.²It was confirmed that the above high bonding strength was obtained.

【0023】

Next, a second embodiment of the present invention will be described. In the present embodiment, the substrate materials are a mirror-finished quartz glass plate having a refractive index of 1.45 at a wavelength of 550 nm and a thickness of 300 μm, and a mirror-finished LiNbO having a refractive index of 2.25 and a thickness of 500 μm at a wavelength of 550 nm.₃Wafers are used. And this quartz glass plate and LiNbO₃High refraction material TiO on each surface of the wafer₂And low refraction material SiO₂, MgF, etc. are laminated to form a film that serves as an antireflection film with respect to their refractive indexes when the two are laminated.

【0024】

At this time, this quartz glass plate and LiNbO₃The outermost surface of the wafer is TiO₂Design and form a thin film. Then those TiO₂When the surface of the thin film is irradiated with ultraviolet light with a wavelength of 380 nm or less, TiO₂The photocatalytic effect of the thin film is exhibited, and the quartz glass plate and LiNbO₃Organic substances and the like adhering to each surface of the wafer are almost completely decomposed to create a superhydrophilic state.

【0025】

Immediately after that, the above surfaces were pasted together, and the quartz glass plate and LiNbO₃The wafer is weighted and heated. In this case as well, the force applied during loading is, for example, 500 g / cm.²It is said to be a degree. The heating condition is, for example, 300 ° C for 1 hour.

【0026】

After that, the wafer bonding is completed by cooling and removing the load. Joined quartz glass plate and LiNbO₃When the bonding strength of the wafer was confirmed with a push-pull gauge, it was 2 kg / cm.²It was confirmed that the above high bonding strength was obtained.

【0027】

Also, quartz glass plate and LiNbO₃When the optical reflection loss on the bonding surface of the wafer was measured, it was suppressed to 0.2% or less, and TiO₂It was confirmed that the multilayer coat containing the thin film also functions as an antireflection film.

【0028】

Next, a third embodiment of the present invention will be described. In this embodiment, two mirror-finished quartz substrates having a refractive index of 1.45 and a thickness of 300 μm at a wavelength of 550 nm are used as the substrate material. And on each surface of each of these quartz substrates, TiO₂A thin film is formed with a film thickness of 50 nm or less. Then those TiO₂When the surface of the thin film is irradiated with ultraviolet light with a wavelength of 380 nm or less, TiO₂The photocatalytic effect of the thin film is exhibited, and organic substances and the like adhering to each surface of each quartz substrate are almost completely decomposed to create a superhydrophilic state.

【0029】

Immediately after that, the above surfaces are bonded to each other, and both quartz substrates are weighted and heated. In this case as well, the force applied during loading is, for example, 500 g / cm.²It is said to be a degree. The heating condition is, for example, 300 ° C for 1 hour.

【0030】

After that, the wafer bonding is completed by cooling and removing the load. When the bonding strength of the bonded quartz substrate was confirmed with a push-pull gauge, it was 2 kg / cm.²It was confirmed that the above high bonding strength was obtained.

【0031】

In addition, no scattering loss was observed at the joint surface of the quartz substrate. Generally, the above TiO₂If the film thickness of a functional film such as a thin film is 50 nm or less, it can be optically ignored.

【0032】

Although the embodiment of joining two substrate materials has been described above, the present invention can be similarly applied to the case of joining three or more substrate materials.

[Simple explanation of drawings]

[Figure 1]

The schematic which shows the manufacturing process of the composite substrate material by one Embodiment of this invention. [Explanation of symbols]

10 Si wafer Surface of 10a Si wafer 11 TiO₂Thin film 20 Si wafer 20a Si wafer surface 21 TiO₂Thin film 30 UV light