阅读说明：本技术 接合体及弹性波元件 (Bonded body and elastic wave element ) 是由 鹈野雄大 后藤万佐司 多井知义 于 2019-08-23 设计创作，主要内容包括：提供一种接合体,将压电性材料基板经由包含氧比率低的硅氧化物的接合层牢固且稳定地接合于包含金属氧化物的支撑基板上。接合体(5、5A)具备：支撑基板(1),其包含金属氧化物；压电性材料基板(4、4A)；接合层(2B),其设置于支撑基板与压电性材料基板之间,且组成为Si-((1－x))O-x(0.008≤x≤0.408)；以及非晶质层(10),其设置于接合层与支撑基板之间。非晶质层(10)中的氧比率比支撑基板(1)中的氧比率高。(Provided is a bonded body wherein a piezoelectric material substrate is firmly and stably bonded to a support substrate comprising a metal oxide via a bonding layer comprising a silicon oxide having a low oxygen content. The junction body (5, 5A) is provided with: a support substrate (1) comprising a metal oxide; a piezoelectric material substrate (4, 4A); a bonding layer (2B) arranged between the support substrate and the piezoelectric material substrate and composed of Si (1－x) O x (x is more than or equal to 0.008 and less than or equal to 0.408); and an amorphous layer (10) provided between the bonding layer and the support substrate. The oxygen ratio in the amorphous layer (10) is higher than the oxygen ratio in the support substrate (1).)

1. A joined body is characterized by comprising:

a support substrate comprising a metal oxide;

a piezoelectric material substrate;

a bonding layer arranged between the support substrate and the piezoelectric material substrate and composed of Si_(1－x)O_xWhereinX is more than or equal to 0.008 and less than or equal to 0.408; and

an amorphous layer disposed between the bonding layer and the support substrate,

the oxygen ratio in the amorphous layer is higher than the oxygen ratio in the support substrate.

2. The junction body according to claim 1,

the metal oxide is selected from the group consisting of sialon, sapphire, cordierite, mullite, and alumina.

3. The junction body according to claim 1 or 2,

the piezoelectric material substrate is selected from the group consisting of lithium niobate, lithium tantalate, and a lithium niobate-lithium tantalate solid solution.

4. The junction body according to any one of claims 1 to 3,

the bonded body includes an intermediate layer provided between the bonding layer and the piezoelectric material substrate.

5. An elastic wave element characterized in that,

the disclosed device is provided with: the junction body according to any one of claims 1 to 4, and an electrode provided on the piezoelectric material substrate.

Technical Field

The present invention relates to a bonded body of a piezoelectric material substrate and a support substrate containing a metal oxide.

Background

Known are: elastic surface wave devices that can function as optical filter elements and oscillators used in mobile phones and the like, lamb wave devices using piezoelectric films, and elastic wave devices such as Film Bulk Acoustic Resonators (FBARs). As such an elastic wave device, there are known: an elastic wave device in which a support substrate is bonded to a piezoelectric substrate on which a surface acoustic wave propagates, and a comb-shaped electrode capable of exciting a surface acoustic wave is provided on the surface of the piezoelectric substrate. By thus bonding the support substrate having a smaller thermal expansion coefficient than the piezoelectric substrate to the piezoelectric substrate, the change in size of the piezoelectric substrate when the temperature changes is suppressed, and the change in frequency characteristics as the surface acoustic wave device is suppressed.

Known are: when bonding a piezoelectric substrate and a silicon substrate, a silicon oxide film is formed on the surface of the piezoelectric substrate, and the piezoelectric substrate and the silicon substrate are directly bonded via the silicon oxide film (patent document 1). In this bonding, the surface of the silicon oxide film and the surface of the silicon substrate are irradiated with a plasma beam to activate the surfaces, and direct bonding is performed (plasma activation method).

In addition, there are known: the surface of the piezoelectric substrate is made rough, a filler layer is provided on the rough surface and planarized, and the filler layer is bonded to the silicon substrate via an adhesive layer (patent document 2). In this method, an epoxy-based or acrylic resin is used for the filling layer and the adhesive layer, and the bonding surface of the piezoelectric substrate is roughened, whereby reflection of bulk waves is suppressed and spurious signals are reduced.

In addition, there are known: a direct bonding method of the FAB (fast Atom Beam) system (patent document 3). In this method, each bonding surface is activated by irradiating it with a neutralized atomic beam at normal temperature, and direct bonding is performed.

On the other hand, patent document 4 describes: the piezoelectric material substrate is directly bonded to a support substrate including ceramics (alumina, aluminum nitride, silicon nitride) via an intermediate layer, instead of being directly bonded to the silicon substrate. The intermediate layer is made of silicon, silicon oxide, silicon nitride or aluminum nitride.

Documents of the prior art

Patent document

Patent document 1: U.S. Pat. No. 7213314B2

Patent document 2: japanese patent No. 5814727

Patent document 3: japanese patent laid-open No. 2014-086400

Patent document 4: japanese patent No. 3774782

Patent document 5: PCT/JP2018/011256

Disclosure of Invention

Depending on the application of the joined body, it is desired to improve the insulation property by increasing the resistance in the joining layer. For example, in the case of an acoustic wave device, noise and loss can be reduced by improving the insulating property of the bonding layer. Accordingly, the applicant of the present application discloses: the composition of the bonding layer is silicon oxide with a low oxygen ratio, whereby a bonding layer with high insulation properties is formed (patent document 5).

However, it is sometimes difficult to firmly and stably bond the piezoelectric material substrate to the support substrate including the metal oxide via the bonding layer including the silicon oxide having a low oxygen content, and peeling may occur when the piezoelectric material substrate is subjected to a process such as polishing.

The present invention addresses the problem of firmly and stably bonding a piezoelectric material substrate to a support substrate comprising a metal oxide via a bonding layer comprising a silicon oxide having a low oxygen content.

The present invention is characterized by comprising:

a support substrate comprising a metal oxide;

a piezoelectric material substrate;

a bonding layer arranged between the support substrate and the piezoelectric material substrate and composed of Si_(1－x)O_x(x is more than or equal to 0.008 and less than or equal to 0.408); and

an amorphous layer disposed between the bonding layer and the support substrate,

the oxygen ratio in the amorphous layer is higher than the oxygen ratio in the support substrate.

The present invention also relates to an elastic wave element characterized in that,

the disclosed device is provided with: the bonded body, and an electrode provided on the piezoelectric material substrate.

Effects of the invention

According to the present invention, the piezoelectric material substrate can be firmly and stably bonded to the support substrate including the metal oxide via the bonding layer including the silicon oxide having a low oxygen content.

Drawings

In fig. 1, (a) shows a state in which the bonding layer 2 is provided on the piezoelectric material substrate 4, (b) shows a state in which the surface 2b of the bonding layer 2A is activated by the neutral beam a, and (c) shows a state in which the surface 1a of the support substrate 1 is activated by the neutral beam a.

In fig. 2, (a) shows a state in which the piezoelectric material substrate 4 and the support substrate 1 are bonded to each other, (b) shows a state in which the piezoelectric material substrate 4A is thinned by processing, and (c) shows a state in which the electrode 6 is provided on the piezoelectric material substrate 4A.

In fig. 3, (a) shows a state in which the intermediate layer 11 and the bonding layer 2 are provided on the piezoelectric material substrate 4, (b) shows a state in which the surface 2b of the bonding layer 2A is activated by the neutral beam a, and (c) shows a state in which the surface 1a of the support substrate 1 is activated by the neutral beam a.

In fig. 4, (a) shows a state in which the piezoelectric material substrate 4 and the support substrate 1 are bonded to each other, (b) shows a state in which the piezoelectric material substrate 4A is thinned by processing, and (c) shows a state in which the electrode 6 is provided on the piezoelectric material substrate 4A.

Detailed Description

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as appropriate.

Fig. 1 and 2 are schematic views for explaining a manufacturing example in which a support substrate is directly bonded to a piezoelectric material substrate.

As shown in fig. 1(a), the bonding layer 2 is formed on the main surface 4a of the piezoelectric material substrate 4. 4b is a main surface on the opposite side of the piezoelectric material substrate 4. Next, as shown in fig. 1(b), the surface 2a of the bonding layer 2 is irradiated with a neutral beam as indicated by an arrow a to activate the surface of the bonding layer 2 to form an activated surface 2 b. On the other hand, as shown in fig. 1(c), the main surface 1a of the support substrate 1 is irradiated with a neutral beam a and activated, thereby obtaining the support substrate 1 having an activated surface. 1b is a main surface on the side opposite to the activated surface.

Next, as shown in fig. 2(a), the activated surface of the bonding layer and the activated surface 1a of the support substrate 1 are directly bonded to each other, thereby obtaining a bonded body 5. Here, by controlling the output of the neutral beam a, the irradiation time, or the like, the amorphous layer 10 can be generated along the bonding interface between the active surface 1a of the support substrate 1 and the bonding layer 2B.

In a preferred embodiment, the surface 4b of the piezoelectric material substrate 4 of the bonded body 1 is further polished to reduce the thickness of the piezoelectric material substrate 4A as shown in fig. 2(b), thereby obtaining a bonded body 5A. And 4c is a grinding surface.

In fig. 2(c), an elastic wave element 7 is produced by forming a predetermined electrode 6 on the polished surface 4c of the piezoelectric material substrate 4A.

In the embodiment of fig. 3 and 4, an intermediate layer 11 is provided between the piezoelectric material substrate 4 and the bonding layers 2, 2A, and 2B.

That is, as shown in fig. 3(a), the intermediate layer 11 and the bonding layer 2 are formed in this order on the main surface 4a of the piezoelectric material substrate 4. Next, as shown in fig. 3(b), the surface 2A of the bonding layer 2 is irradiated with a neutral beam as indicated by an arrow a to activate the surface of the bonding layer 2A, thereby forming an activated surface 2 b. On the other hand, as shown in fig. 3(c), the main surface 1a of the support substrate 1 is irradiated with a neutral beam a and activated, thereby obtaining the support substrate 1 having an activated surface. 1b is a main surface on the side opposite to the activated surface.

Next, as shown in fig. 4(a), the activated surface of the bonding layer and the activated surface 1a of the support substrate 1 are directly bonded to each other, thereby obtaining a bonded body 15. Here, by controlling the output of the neutral beam a, the irradiation time, or the like, the amorphous layer 10 can be generated along the bonding interface between the active surface 1a of the support substrate 1 and the bonding layer 2B.

In a preferred embodiment, the surface 2b of the piezoelectric material substrate 2 of the bonded body 1 is further polished to reduce the thickness of the piezoelectric material substrate 4A as shown in fig. 4(b), thereby obtaining a bonded body 15A. And 4c is a grinding surface.

In fig. 4(c), an elastic wave element 17 is produced by forming a predetermined electrode 9 on the polished surface 4c of the piezoelectric material substrate 4A.

In the present invention, the support substrate includes a metal oxide. The metal oxide may be an oxide of a single metal, or may be a composite oxide of a plurality of metals. The metal oxide is preferably selected from the group consisting of sialon, sapphire, cordierite, mullite and alumina. The alumina is preferably a light-transmitting alumina.

From the viewpoint of bonding strength, the relative density of the supporting substrate is preferably 95.5% or more, and may be 100%. Relative density was determined using archimedes' method. The method for producing the supporting substrate is not particularly limited, and a sintered body is preferable.

The sialon is a ceramic obtained by sintering a mixture of silicon nitride and aluminum oxide, and has the following composition.

Si_6－zAl_zO_zN_8－z

That is, sialon has a composition in which silicon nitride is mixed with alumina, and z represents a mixing ratio of alumina. z is more preferably 0.5 or more. Further, z is more preferably 4.0 or less.

The sapphire is of Al₂O₃The aluminum oxide is Al₂O₃A polycrystal of the composition (1). Cordierite is 2 MgO.2 Al₂O₃·5SiO₂A ceramic of the composition (1). Mullite of 3Al₂O₃·2SiO₂～2Al₂O₃·SiO₂A ceramic having a composition in the range of (1).

The material of the piezoelectric material substrate is not limited as long as it has desired piezoelectricity, and is preferably LiAO₃OfAnd (4) crystallizing. Here, a is one or more elements selected from the group consisting of niobium and tantalum. Thus, LiAO₃The lithium niobate may be lithium niobate, lithium tantalate, or lithium niobate-lithium tantalate solid solution.

The present invention comprises: a bonding layer arranged between the support substrate and the piezoelectric material substrate and composed of Si_(1－x)O_x(0.008≤x≤0.408)。

The composition is as follows: with SiO₂(corresponding to x being 0.667), the oxygen ratio is greatly reduced. If silicon oxide Si containing the composition is used_(1－x)O_xThe piezoelectric material substrate is bonded to the support substrate via the bonding layer of (2), whereby the insulating property in the bonding layer can be improved.

In Si constituting the bonding layer_(1－x)O_xIn the composition (2), if x is less than 0.008, the resistance in the bonding layer decreases, and the desired insulation property cannot be obtained. Therefore, x is 0.008 or more, preferably 0.010 or more, more preferably 0.020 or more, and particularly preferably 0.024 or more. Further, if x is greater than 0.408, the bonding strength decreases, and peeling of the piezoelectric material substrate is likely to occur, so x is set to 0.408 or less, more preferably 0.225 or less.

The resistivity of the bonding layer is preferably 4.8 × 10³Omega cm or more, more preferably 5.8X 10³Omega cm or more, particularly preferably 6.2X 10³Omega cm or more. On the other hand, the resistivity of the bonding layer is usually 1.0 × 10⁸Omega cm or less.

The thickness of the bonding layer is not particularly limited, but is preferably 0.01 to 10 μm, and more preferably 0.01 to 0.5 μm from the viewpoint of production cost.

The method for forming the bonding layer is not limited, and examples thereof include: sputtering (sputtering), Chemical Vapor Deposition (CVD), and vapor deposition. Here, it is particularly preferable that the oxygen ratio (x) of the bonding layer be controlled by adjusting the amount of oxygen flowing into the chamber when the sputtering target is reactive sputtering of Si.

The specific manufacturing conditions of the bonding layer depend on the chamber specifications and are therefore suitably selected, in the preferred embodiment,the total pressure is 0.28 to 0.34Pa, and the oxygen partial pressure is 1.2X 10^―3～5.7×10^－2Pa, and the film forming temperature is set to be normal temperature. Further, as the Si target, Si doped with B can be exemplified. As described later, the amount of B (boron) as an impurity in the interface between the bonding layer and the supporting substrate 1 was controlled to 5 × 10¹⁸atoms/cm³～5×10¹⁹atoms/cm³Left and right. This can more reliably ensure the insulation property in the bonding layer.

In a preferred embodiment, the active surface of the bonding layer and the active surface of the support substrate are directly bonded. In other words, a bonding interface is provided along the interface between the bonding layer and the support substrate. In this case, the arithmetic average roughness Ra of the active surface of the bonding layer is preferably 1nm or less, and more preferably 0.3nm or less. The arithmetic average roughness Ra of the active surface of the support substrate is preferably 1nm or less, and more preferably 0.3nm or less. This further improves the bonding strength between the support substrate and the bonding layer.

The joined body of the present invention further comprises: and an amorphous layer formed between the bonding layer and the supporting substrate, wherein the amorphous layer has a higher oxygen ratio than the supporting substrate. That is, although the amorphous layer is generated along the active surface of the support substrate, it was found that: since oxygen diffusion occurs in the amorphous layer, the oxygen ratio in the amorphous layer may be higher than the oxygen ratio of the metal oxide constituting the support substrate. Also, it was found that: in the case where oxygen is diffused in this manner, the bonding strength of the piezoelectric material substrate to the support substrate is improved, and for example, even when the piezoelectric material substrate is thinned by processing, peeling of the piezoelectric material substrate is less likely to occur.

In a preferred embodiment, the composition of the amorphous layer includes a metal constituting the support substrate, oxygen (O), and argon (Ar) as main components. In the case where the supporting substrate comprises a sialon ceramic, the amorphous layer has a composition containing silicon (Si), aluminum (Al), nitrogen (N), oxygen (O), and argon (Ar) as main components. "as a main component" means: when the total atomic ratio is 100 atomic%, the total atomic ratio is 95 atomic% or more, and more preferably 97 atomic% or more. In particular, the amorphous layer preferably has the same composition as the material of the support substrate, has an oxygen ratio higher than that of the material of the support substrate, and contains argon.

In the present invention, the oxygen ratio in the amorphous layer is higher than the oxygen ratio in the support substrate. From the viewpoint of enhancing the bonding strength, the difference in the oxygen ratio is preferably 0.5 atomic% or more, and more preferably 1.0 atomic% or more. In practice, the difference in oxygen ratio is preferably 7.0 atomic% or less.

In addition, from the viewpoint of improving the bonding strength, the atomic ratio of argon (Ar) in the amorphous layer is preferably 1.0 atomic% or more, and more preferably 1.5 atomic% or more. The atomic ratio of argon (Ar) in the amorphous layer is preferably 5.0 atomic% or less, and more preferably 4.8 atomic% or less.

The material of the intermediate layer is not particularly limited as long as it is bonded to the bonding layer and the piezoelectric material substrate, and is preferably SiO₂、Ta₂O₅、TiO₂、ZrO₂、HfO₂、Nb₂O₃、Bi₂O₃、Al₂O₃、MgO、AlN、Si₃N₄。

In particular, when the antenna is used for high frequencies (e.g., in the frequency band of 5G communication of 3.5 to 6 GHz), the frequency of the elastic wave needs to be increased. The sound velocity of the high sound velocity material is preferably 6000m/s or more, and more preferably 10000m/s or more. The upper limit of the sound velocity of the material of the intermediate layer is not particularly limited, and it is practically difficult to exceed 30000m/s, so the upper limit is 30000m/s or less, and in many cases 25000m/s or less. As the high sound velocity material, AlN and Si can be exemplified₃N₄. The sound velocity of the material was calculated from the density (JIS C2141), the young's modulus (JIS R1602), and the poisson's ratio (JIS R1602) measured by the JIS method.

In addition, when the antenna is used at a high frequency (e.g., in a frequency band for 5G communication of 3.5 to 6 GHz), a signal having a large power is input, and thus it is necessary to improve heat dissipation. In this case, the material of the intermediate layer is preferably a high heat conductive material.The thermal conductivity of the high thermal conductive material is preferably 100W/(mK) or more, more preferably 900W/(mK) or more, and particularly preferably 1000W/(mK). The upper limit of the thermal conductivity of the material of the intermediate layer is not particularly limited, and it is practically difficult to exceed 5000W/(m.K), and therefore the upper limit is 5000W/(m.K) or less, and is often 3000W/(m.K) or less. As the high heat conductive material, AlN and Si can be exemplified₃N₄. The thermal conductivity of the material was measured according to JIS R1611.

Hereinafter, each constituent element of the present invention will be further described.

The use of the joined body of the present invention is not particularly limited, and for example, the joined body can be preferably applied to an elastic wave device and an optical device.

As elastic wave devices, there are known: surface acoustic wave devices, lamb wave devices, thin film resonators (FBARs), and the like. For example, in a surface acoustic wave device, an IDT (inter digital transducer) electrode (also referred to as a comb electrode or a curtain electrode) on the input side for exciting a surface acoustic wave and an IDT electrode on the output side for receiving a surface acoustic wave are provided on the surface of a piezoelectric material substrate. When a high-frequency signal is applied to the IDT electrode on the input side, an electric field is generated between the electrodes, and a surface acoustic wave is excited and propagates on the piezoelectric material substrate. The propagating surface acoustic wave can be output as an electric signal from the IDT electrode on the output side provided in the propagation direction.

The piezoelectric material substrate may have a metal film on a bottom surface thereof. When a lamb wave device is manufactured as an acoustic wave device, the metal film serves to increase the electromechanical coupling coefficient in the vicinity of the back surface of the piezoelectric material substrate. In this case, the lamb wave element has the following structure: comb electrodes are formed on the surface of the piezoelectric material substrate, and the metal film of the piezoelectric material substrate is exposed by the cavity provided in the support substrate. Examples of the material of such a metal film include: aluminum, aluminum alloys, copper, gold, and the like. In the case of manufacturing a lamb wave device, a composite substrate including a piezoelectric material layer having no metal film on the bottom surface may be used.

In addition, the piezoelectric material substrate may have a metal film and an insulating film on the bottom surface thereof. When the thin film resonator is manufactured as an elastic wave device, the metal film functions as an electrode. In this case, the thin film resonator has the following structure: electrodes are formed on the front and back surfaces of the piezoelectric material substrate, and the insulating film is used as a cavity, whereby the metal film of the piezoelectric material substrate is exposed. Examples of the material of such a metal film include: molybdenum, ruthenium, tungsten, chromium, aluminum, and the like. Further, as the material of the insulating film, for example, there can be mentioned: silicon dioxide, phosphosilicate glass, borophosphosilicate glass, and the like.

Further, as the optical element, there can be exemplified: an optical switching element, a wavelength conversion element, and an optical modulation element. In addition, a periodic polarization reversal structure can be formed in the piezoelectric material substrate.

The present invention is directed to an elastic wave element, and when the material of the piezoelectric material substrate is lithium tantalate, it is preferable to use a piezoelectric material substrate that is rotated from the Y axis to the Z axis by 36 to 47 ° (for example, 42 °) around the X axis, which is the propagation direction of the elastic surface wave, because the propagation loss is small. When the piezoelectric material substrate contains lithium niobate, it is preferable to use a piezoelectric material substrate that is rotated from the Y axis to the Z axis by 60 to 68 ° (for example, 64 °) about the X axis, which is the propagation direction of the elastic surface wave, because the propagation loss is small. Further, the size of the piezoelectric material substrate is not particularly limited, and for example, the diameter is 50 to 150mm and the thickness is 0.2 to 60 μm.

In order to obtain the joined body of the present invention, the following method is preferred.

First, the surface of the bonding layer and the surface of the support substrate (bonding surface) are planarized to obtain a flat surface. Here, methods for planarizing each surface include lapping (lap) polishing, Chemical Mechanical Polishing (CMP), and the like. The flat surface preferably has Ra < 1nm, more preferably 0.3nm or less.

Next, the surfaces of the bonding layer and the supporting substrate are cleaned to remove the residue of the polishing agent and the affected layer. The surface cleaning method includes wet cleaning, dry cleaning, and brushing is preferred in order to obtain a clean surface easily and efficiently. In this case, it is particularly preferable that: sunwash LH540 was used as a cleaning liquid, and then, cleaning was performed using a scrubber using a mixed solution of acetone and IPA.

Next, the surface of the bonding layer and the surface of the supporting substrate are irradiated with a neutral beam to activate the respective flat surfaces.

When surface activation is performed by using a neutral beam, it is preferable to generate a neutral beam and irradiate the neutral beam using the apparatus described in patent document 3. That is, as the beam source, a saddle-domain type high-speed atomic beam source is used. Then, an inert gas is introduced into the chamber, and a high voltage is applied to the electrode from a direct current power supply. Thus, electrons e move by a saddle-domain electric field generated between the electrode (positive electrode) and the case (negative electrode), and a beam of atoms and ions generated by the inert gas is generated. In the beam that reaches the grid, the ion beam is neutralized in the grid, and therefore a beam of neutral atoms is emitted from the high-speed atom beam source. The atomic species constituting the beam are preferably inert gases (argon, nitrogen, etc.).

The voltage for activation by beam irradiation is preferably 0.5 to 2.0kV, and the current is preferably 50 to 200 mA.

Next, the activated surfaces are brought into contact with each other and joined in a vacuum atmosphere. The temperature at this time is room temperature, specifically, preferably 40 ℃ or lower, and more preferably 30 ℃ or lower. The temperature at the time of bonding is particularly preferably 20 ℃ to 25 ℃. The pressure during bonding is preferably 100 to 20000N.

Examples

(examples 1, 2 and 3 and comparative examples 1 and 2)

The bonded bodies 5 and 5A of the respective examples shown in tables 1 and 2 were prepared by the method described with reference to fig. 1 and 2.

Specifically, the following are used: a lithium tantalate substrate (LT substrate) having an OF part and a diameter OF 4 inches and a thickness OF 250 μm was used as the piezoelectric material substrate 4. The LT substrate used: a46 DEG Y cut X-propagation LT substrate is formed on a cut plate having a cut angle of Y rotation and a propagation direction of a Surface Acoustic Wave (SAW) as X. The surface 4a of the piezoelectric material substrate 4 was mirror-polished so that the arithmetic average roughness Ra became 0.3 nm. Wherein Ra was measured in a field of view of 10. mu. m.times.10 μm by an Atomic Force Microscope (AFM).

Next, the bonding layer 2 is formed on the surface 4a of the piezoelectric material substrate 4 by a dc sputtering method. The target uses Si doped with boron. Further, oxygen gas was introduced as an oxygen source. At this time, the total pressure and the oxygen partial pressure of the atmosphere in the chamber are changed by changing the oxygen introduction amount, thereby changing the oxygen ratio of the bonding layer 2. The thickness of the bonding layer 2 is set to 100 to 200 nm. The arithmetic average roughness Ra of the surface 2a of the bonding layer 2 is 0.2 to 0.6 nm. Then, the bonding layer 2 is subjected to Chemical Mechanical Polishing (CMP) to a film thickness of 80 to 190nm and an Ra of 0.08 to 0.4 nm.

On the other hand, as the support substrate 1, prepared were: a support substrate 1 comprising a silicon-aluminum-nitrogen-containing ceramic (z: 2.5) having an Orientation Flat (OF) portion, a diameter OF 4 inches, and a thickness OF 500 μm. The surfaces 1a, 1b of the support substrate 1 were finished by Chemical Mechanical Polishing (CMP) so that each arithmetic average roughness Ra was 0.2 nm.

Next, the flat surface 2b of the bonding layer 2A and the surface 1a of the support substrate 1 are cleaned to remove dirt, and then introduced into a vacuum chamber. Vacuumizing until 10^-6After several pascals, the bonding surfaces 1a and 2b of the substrates were irradiated with a high-speed atomic beam (acceleration voltage 1kV, Ar flow rate 27sccm) for 120 sec. Next, the beam irradiation surface (active surface) 2b of the bonding layer 2A and the active surface 1a of the support substrate 1 were brought into contact, and then, they were pressed at 10000N for 2 minutes to bond them (see fig. 2 (a)). Next, the joined body 5 of each example thus obtained was heated at 100 ℃ for 20 hours.

Next, the surface 4b of the piezoelectric material substrate 4 is ground and polished so that the thickness is changed from the first 250 μm to 1 μm (see fig. 2 (b)).

The obtained joined bodies 5 and 5A of the respective examples were evaluated for the following characteristics.

(confirmation of amorphous layer)

The presence of an amorphous layer was observed as follows.

A measuring device:

the microstructure was observed using a transmission electron microscope (Hitachi high tech H-9500).

The measurement conditions were as follows:

the sample thinned by the FIB (focused ion beam) method was observed at an acceleration voltage of 200 kV.

(ratio of oxygen atoms and argon atoms in the bonding layer, supporting substrate, and amorphous layer)

Elemental analysis was performed by EDS (energy dispersive X-ray spectrometer) using the following apparatus, and the ratios of oxygen atoms and argon atoms in the bonding layer, the supporting substrate, and the amorphous layer were measured.

A measuring device:

elemental analysis was carried out using an elemental analysis apparatus (Japanese Electron JEM-ARM 200F).

The measurement conditions were as follows:

the sample thinned by the FIB (focused ion beam) method was observed at an acceleration voltage of 200 kV.

(bonding Strength)

The joint strength of each of the joint bodies 5 and 5A was measured by a crack propagation method. Wherein, when the bonding strength exceeds 1.75J/m²In this case, peeling does not occur near the bonding layer 2B, and the bonded bodies 5 and 5A are subject to main body failure.

[ Table 1]

[ Table 2]

In comparative examples 1 and 2, the oxygen ratio in the amorphous layer was slightly lower than that in the support substrate, and the bonding strength was low.

In examples 1, 2, and 3, the oxygen ratio in the amorphous layer was higher than that in the support substrate, the bonding strength was significantly improved, and peeling did not occur even when the piezoelectric material substrate was polished.

(example 4, comparative example 3)

In example 1, the material of the support substrate was changed to sapphire, and the FAB irradiation dose was also changed. Except for this, joined bodies 5 and 5A were produced in the same manner as in example 1, and the oxygen ratio, argon ratio, and joining strength of each portion were measured. The results are shown in Table 3.

[ Table 3]

In comparative example 3, the oxygen ratio in the amorphous layer was slightly lower than that in the support substrate, and the bonding strength was low.

In example 4, the oxygen ratio in the amorphous layer was higher than that in the support substrate, the bonding strength was significantly improved, and peeling did not occur even when the piezoelectric material substrate was polished.

(example 5, comparative example 4)

In example 1, the material of the support substrate was changed to cordierite, and the FAB irradiation dose was also changed. Except for this, joined bodies 5 and 5A were produced in the same manner as in example 1, and the oxygen ratio, argon ratio, and joining strength of each portion were measured. The results are shown in Table 4.

[ Table 4]

In comparative example 4, the oxygen ratio in the amorphous layer was the same as that in the support substrate, and the bonding strength was low.

In example 5, the oxygen ratio in the amorphous layer was higher than that in the support substrate, the bonding strength was significantly improved, and peeling did not occur even when the piezoelectric material substrate was polished.

(example 6, comparative example 5)

In example 1, the material of the support substrate was changed to mullite, and the FAB irradiation amount was also changed. Except for this, joined bodies 5 and 5A were produced in the same manner as in example 1, and the oxygen ratio, argon ratio, and joining strength of each portion were measured. The results are shown in Table 5.

[ Table 5]

In comparative example 5, the oxygen ratio in the amorphous layer was slightly lower than that in the support substrate, and the bonding strength was low.

In example 6, the oxygen ratio in the amorphous layer was higher than that in the support substrate, the bonding strength was significantly improved, and peeling did not occur even when the piezoelectric material substrate was polished.

(example 7, comparative example 6)

In example 1, the material of the support substrate was changed to translucent alumina, and the FAB irradiation dose was also changed. Except for this, joined bodies 5 and 5A were produced in the same manner as in example 1, and the oxygen ratio, argon ratio, and joining strength of each portion were measured. The results are shown in Table 6.

[ Table 6]

In comparative example 6, the oxygen ratio in the amorphous layer was slightly lower than that in the support substrate, and the bonding strength was low.

In example 7, the oxygen ratio in the amorphous layer was higher than that in the support substrate, the bonding strength was significantly improved, and peeling did not occur even when the piezoelectric material substrate was polished.