JP2011187867A - Bonding method and crystal element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bonding method in which crystal is bonded with higher strength without requiring heating etc., nor producing gas during manufacture and in an in-use environment. <P>SOLUTION: After a sputtering method is used to start forming a substance layer 102 on a bonding surface of a crystal substrate 101 and to start forming a substance layer 102 on a bonding surface of a crystal substrate 111, the bonding surface of the crystal substrate 101 and the bonding surface of the crystal substrate 111 where the substance layers 102 of 0.2 to <1 nm in layer thickness are formed respectively are bonded together with the substrate layer 102 interposed. The two substrates are bonded before the layer thicknesses of the substance layers 102 reach 1 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bonding method and a crystal element for bonding crystals.

  Elements using quartz include quartz piezoelectric elements that use the piezoelectric effect of quartz, quartz optical elements that use the optical characteristics of quartz, and the like. Many crystal piezoelectric elements are manufactured by fixing a crystal piece processed into a desired shape inside a container and sealing the container. For fixing the crystal piece, for example, an organic adhesive having conductivity is used. In sealing the container, in a vacuum exhaust state or an inert gas atmosphere, local fusion bonding such as electron beam welding, seam welding, laser welding, solder bonding, eutectic bonding such as Au-Sn, Au-Ge, Alternatively, a bonding method such as glass bonding is used.

  However, the above-described bonding method has a problem that the original characteristics of the quartz crystal are impaired by gas generated in the manufacturing process or use environment, heat stress, and the like.

  In addition, the quartz optical element is often used by bonding a plurality of crystal pieces and glass pieces, and in these bondings, an organic adhesive such as acrylic is used. However, the organic adhesive is inferior in light transmittance in the short wavelength region and the long wavelength region (including the infrared region) when the visible region is the center, and is decomposed by ultraviolet rays to cause a change with time. There is a problem that the wavelength range that can be handled is limited.

  For the joining method having the above-described problems, there is a joining technique called direct joining. Direct bonding includes anodic bonding, fusion bonding, and surface activated bonding using an ion beam.

  As is well known, anodic bonding is a technique in which the polished surfaces of a glass substrate and a silicon substrate are brought into contact with each other, and a voltage is applied while heating. In anodic bonding, alkali ions in glass are moved by a direct current electric field and bonded by causing a covalent bond between them.

  In fusion bonding, first, a bonding surface of a substrate such as silicon or silicon oxide is polished, and a hydroxyl group is attached to the polished surface by acting nitric acid. These are superposed and bonded weakly by hydrogen bonding, and then heat treatment (about 1000 ° C.) is performed to remove moisture, thereby bonding strongly by Si—O—Si bonding. In fusion bonding, no voltage is applied unlike anodic bonding. There is also a technique for reducing the heating temperature by bonding after surface treatment with plasma. In order to increase surface hydroxyl groups due to plasma, the heating temperature is said to be lowered, and it is also possible to bond in the air after plasma activation.

  In surface activated bonding, surface activated bonding uses an ion beam to etch away a surface layer that hinders bonding, and directly bonds the bonds of atoms on the surface to form a strong bond. The surface after the etching process is in a state where it easily reacts with surrounding gas molecules, and the process is performed inside a container evacuated to a high vacuum.

  However, the direct bonding technique described above has the following problems.

  First, in anodic bonding, heating at 400 ° C. or higher is required to promote the movement of alkali ions, and stress due to thermal strain is generated. In addition, oxygen is generated from the glass by an electrochemical reaction. The generation of these thermal stresses and the generation of oxygen has a problem of adversely affecting the characteristics as a vibrator, for example.

  Also, in fusion bonding, heating is required, and hydrogen is generated, which has a problem of adversely affecting the characteristics as a vibrator.

  On the other hand, in the surface activated bonding described above, there is no heating and no generation of oxygen or hydrogen. However, when an oxide crystal such as quartz is etched by an ion gun or the like, there is a problem that the surface becomes rough and difficult to join. When the surface is rough, strong bonding strength cannot be obtained and the stability is lacking.

  As a technique for solving the above problems, a film of metal or various compounds is formed in a film thickness range of 1 nm to 10 μm by a vacuum film forming method, and the film is covered while maintaining the vacuum during or after the film formation. A technique has been proposed in which the surfaces of the coatings formed on the bonding surface of the bonding material are overlapped at room temperature and the coatings are diffused to join each other (see Patent Document 1).

JP 2008-207221 A

  However, higher bonding strength has been demanded for crystal bonding.

  The present invention has been made to solve the above-described problems, and does not require heating or the like, and does not generate gas in the manufacturing or use environment, and the crystal is bonded with stronger strength. The purpose is to be able to.

  In the bonding method according to the present invention, the formation of a material layer by the vacuum film formation method is started on the bonding surface of the first substrate and the bonding surface of the second substrate made of quartz in the processing chamber of the film formation apparatus by the vacuum film formation method. And bonding the bonding surface of the first substrate and the bonding surface of the second substrate, each of which is formed with a material layer having a thickness of 0.2 nm or more and less than 1 nm, through the material layer in the processing chamber. At least a second step of bonding the first substrate and the second substrate at each bonding surface, and the bonding surface of the first substrate and the bonding surface of the second substrate have an average surface roughness of less than 1 nm. .

  In the above bonding method, the second step may be performed after the formation of the material layer by the vacuum film formation method is stopped.

  In the bonding method, the first substrate is made of quartz. Moreover, the vacuum film-forming method should just be the method selected from the sputtering method and the ion plating method. Moreover, the substance layer should just be comprised from the metal or semiconductor material.

  The crystal element according to the present invention is manufactured by the above-described bonding method. For example, the crystal element may be an optical element in which a first substrate and a second substrate made of crystal are bonded via a material layer. The crystal element includes a piezoelectric element mounted on the first substrate and a second substrate having a recess formed corresponding to the piezoelectric element. The piezoelectric element is interposed between the material layers. The first substrate and the second substrate bonded together may be sealed inside the recess.

  As described above, in the present invention, the material layer is formed by the vacuum film forming method on the bonding surface of the first substrate and the bonding surface of the second substrate made of quartz in the processing chamber of the film forming apparatus by the vacuum film forming method. The bonding surface of the first substrate and the bonding surface of the second substrate on which the material layers having a layer thickness of 0.2 nm or more and less than 1 nm were respectively formed were attached via the material layer. As a result, according to the present invention, it is possible to obtain an excellent effect that the crystal can be bonded with a stronger strength without the need for heating or the like and without generating gas at the time of manufacture or use environment.

It is process drawing for demonstrating the joining method in Embodiment 1 of this invention. It is process drawing for demonstrating the joining method in Embodiment 1 of this invention. It is process drawing for demonstrating the joining method in Embodiment 1 of this invention. It is a characteristic view showing the relationship between the layer thickness of the material layer and the bonding strength (tensile strength). It is process drawing for demonstrating the joining method in Embodiment 2 of this invention. It is process drawing for demonstrating the joining method in Embodiment 2 of this invention. It is process drawing for demonstrating the joining method in Embodiment 2 of this invention. It is process drawing for demonstrating the joining method in Embodiment 2 of this invention. It is sectional drawing which shows the structure of the crystal element in Embodiment 2 of this invention. It is a correlation diagram which shows the relationship between the layer thickness of the substance layer which consists of metals, and film resistance value. It is sectional drawing which shows the structure of the crystal element in Embodiment 3 of this invention. It is a characteristic view which shows the relationship between the material and layer thickness of the substance layer used for joining, and the transmittance | permeability of an optical element. It is a characteristic view which shows the relationship between the material and layer thickness of the substance layer used for joining, and the transmittance | permeability of an optical element. It is a characteristic view which shows the relationship between the material and layer thickness of the substance layer used for joining, and the transmittance | permeability of an optical element. It is a characteristic view which shows the relationship between the material and layer thickness of the substance layer used for joining, and the transmittance | permeability of an optical element. It is a characteristic view which shows the relationship between the material and layer thickness of the substance layer used for joining, and the transmittance | permeability of an optical element. It is a characteristic view which shows the change by the wavelength of the optical loss rate at the time of using an organic adhesive for joining, and the case where a substance layer is used. It is a characteristic view which shows the change by the wavelength (2.5-5 micrometers) of the optical transmittance at the time of using an organic type adhesive agent for joining. It is a characteristic view which shows the change by the wavelength (2.5-5 micrometers) of the optical transmittance at the time of using a substance layer for joining.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the present invention will be described. 1A to 1C are process diagrams for explaining a bonding method according to Embodiment 1 of the present invention. 1A to 1C show partial cross sections of the quartz crystal substrate 101 and the quartz crystal substrate 111 to be bonded.

  First, as shown in FIG. 1A, a quartz substrate (first substrate) 101 and a quartz substrate (second substrate) 111 are prepared. The bonding surface of the quartz substrate 101 and the bonding surface of the quartz substrate 111 are set to a surface roughness of less than 1 nm by well-known polishing or the like. Next, the quartz substrate 101 and the quartz substrate 111 are carried into a processing chamber 131 of a film forming apparatus (sputtering apparatus) using a vacuum film forming method (for example, sputtering method).

  Next, as shown in FIG. 1B, the formation of the material layer 102 by the vacuum film formation method is started on the bonding surface of the quartz substrate 101 and the bonding surface of the quartz substrate 111. For example, the formation of the material layer 102 on the bonding surface of the quartz substrate 101 and the formation of the material layer 102 on the bonding surface of the quartz substrate 111 are started by a well-known sputtering method.

For example, a magnetron sputtering apparatus is used as the film forming apparatus, and first, the inside of the processing chamber 131 into which the quartz substrate 101 and the quartz substrate 111 are carried is evacuated to a pressure of about 10 ⁻⁶ Pa. Next, argon gas is introduced into the processing chamber 131 as a sputtering gas, and plasma power is input to generate plasma in the processing chamber, thereby starting sputtering film formation. Here, an inert gas such as argon is used as the sputtering gas. In addition, a material forming the material layer 102 is used for the target. For example, the target is Cr. In this case, a Cr layer is formed as the material layer 102.

  As described above, after starting the formation of the material layer 102 in the processing chamber 131, the bonding surface of the crystal substrate 101 on which the material layer 102 having a layer thickness of 0.2 nm or more and less than 1 nm is formed, and the crystal substrate 111. The bonding surface is attached via the material layer 102. In this attachment, it is not necessary to apply pressure. For example, a jig (not shown) for holding and abutting two substrates may be disposed inside the processing chamber 131 and attached using this jig (see Patent Document 1). Bonding is possible with the weight of the substrate.

  As described above, as shown in FIG. 1C, the crystal substrate 101 and the crystal substrate 111 are bonded to each other through the material layer 102. The bonding of the quartz substrate 101 and the quartz substrate 111 may be performed after (after) the sputtering state described above after the material layer 102 having a layer thickness of 0.2 nm or more and less than 1 nm is formed, It may be performed while the sputtering state is continued. It is important to attach the two substrates before the thickness of the material layer 102 reaches 1 nm.

  In addition, the material layer 102 can also be comprised from metals, such as Ti, Ta, Cu, and Al other than Cr. Hereinafter, the relationship between the thickness of the material layer 102 and the bonding strength (tensile strength) when Ti, Cr, and Ta are used for the material layer 102 will be described.

  FIG. 2 is a characteristic diagram showing the relationship between the thickness of the material layer 102 and the bonding strength (tensile strength). As a result, bonding (attachment) is performed 30 seconds after film formation. In the figure, white squares show the results of the material layer 102 made of Ti, white circles show the material layer 102 made of Cr, and white triangles show the material layer made of Ta. . Here, the “layer thickness” represents the thickness of the material layer 102 formed on one substrate. As is clear from FIG. 2, regardless of the material, the tensile strength (bonding force) when the layer thickness of the substance layer 102 is less than 1 nm is about 25 MPa or more, and the layer thickness of the substance layer 102 is less than 1 nm. Strong joint strength is obtained. Note that since the thickness of the material layer 102 is less than 1 nm, it is important that the surface roughness of the substrate is less than 1 nm.

Here, it will be described that stronger bonding strength can be obtained by setting the thickness of the material layer to less than 1 nm. In the bonding method in the present embodiment described above, first, a very thin material layer is formed on the bonding surface of the substrate in a clean environment without oxygen in a high vacuum state, and the diffusion phenomenon of the material constituting this material layer It can be considered that two substrates are bonded using the above. In this bonding method, the state of the incomplete layer before the material layer becomes a uniform film is more active and has a higher diffusion rate. Therefore, it is considered that higher bonding strength can be obtained. Here, if the inside of the processing chamber in which the bonding is performed is set to a pressure (vacuum degree) of 10 ⁻⁶ Pa or less, the formation of the natural oxide film is suppressed and the environment becomes sufficiently clean, and the above-described bonding can be performed. The results are known. For example, the pressure in the processing chamber may be set to 10 ⁻⁶ Pa or less in the initial stage before starting sputtering. Alternatively, after sputter is stopped, the supply of the sputtering gas is stopped to obtain a higher degree of vacuum, and then attachment may be performed for bonding. In the case where a noble metal such as Au, Pt, or Ag or a metal that is difficult to oxidize such as dynamic is used as the material layer, the above-described bonding can be performed even if the internal pressure of the processing chamber for bonding is about 10 ⁻⁴ Pa.

  According to this bonding method, since etching for exposing an active surface to the bonding surface of the substrate is not performed, stable bonding can be performed even with a substrate having etching anisotropy such as quartz. In addition, since this bonding method does not require heat treatment or the like, even a substrate with low heat resistance can be easily applied, and the process cost by heating can be reduced.

  In addition, by setting the material layer 102 to a layer thickness of less than 1 nm (0.2 nm or more), first, in the case of a quartz optical element, the light transmission characteristics of the quartz substrate are not impaired. Such a thin layer has almost no absorption in the visible light range and can be used without any problem as various optical elements. In the case of a crystal piezoelectric element, a crystal substrate on which various wirings are formed is a target to be bonded. Even in such a case, even if the material layer 102 is made of a metal material, the material layer 102 is thin and has a high resistance of less than 1 nm. Don't be. As is well known, high insulation can be obtained if the metal layer has a thickness of 2 nm or less.

  As described above, according to the present embodiment, since the thickness of the material layer is set to 0.2 nm or more and less than 1 nm, the two substrates through the material layer can be bonded with more sufficient bonding strength. Become. In addition, since a material layer interposed between two bonded substrates is very thin, optical characteristics are not deteriorated even when used as an optical element. In addition, since the material layer is very thin and a high insulating state is obtained in the material layer, a short circuit or the like is not caused even when applied to a piezoelectric element. Further, it is not heated to a high temperature, and breakage due to generation of stress can be suppressed.

[Embodiment 2]
Next, a second embodiment of the present invention will be described. In the second embodiment, a piezoelectric element (quartz element) is described as an example, and in particular, sealing of a piezoelectric element is described as an example.

  First, as shown in FIG. 3A, the piezoelectric element 301 is mounted (mounted) on a support substrate 302 made of quartz. As is well known, the piezoelectric element 301 is a crystal resonator configured by forming a predetermined electrode 304 and a wiring 305 on a piezoelectric substrate 303 such as a crystal. In addition, the support substrate 302 is connected to the wiring 305 to support and fix the end of the piezoelectric element 301. The support 306 has conductivity, the wiring 307 connected to the wiring 305 through the support 306, the via wiring 308, and An external terminal 309 is formed. The piezoelectric element 301 is mounted on the support substrate 302 by the support portion 306.

  Next, as shown in FIG. 3B, a sealing substrate 311 made of quartz is prepared. A recess 312 is formed in the sealing substrate 301 corresponding to the portion of the piezoelectric element 301.

  Next, the support substrate 301 and the sealing substrate 311 are carried into a processing chamber of a film forming apparatus (sputtering apparatus) using a vacuum film forming method (for example, sputtering method). Note that the film forming apparatus and the processing chamber are not shown. Subsequently, as shown in FIGS. 3C and 3D, the surface (film formation surface) on which the piezoelectric element 301 of the support substrate 302 is mounted and the surface (film formation) on which the recess 312 of the sealing substrate 311 is formed. Surface), the formation of the material layer 321 by the vacuum film formation method is started. For example, formation of the material layer 321 on the film formation surface of the support substrate 301 and formation of the material layer 321 on the film formation surface of the sealing substrate 311 are started by a well-known sputtering method. For example, a magnetron sputtering apparatus may be used as the film forming apparatus, and formation of the material layer 321 made of Al may be started using aluminum (Al) as a target.

  As described above, after the deposition of the material layer 321 is started in the processing chamber, the bonding surface of the support substrate 301 on which the material layer 321 having a layer thickness of 0.2 nm or more and less than 1 nm is formed and the bonding of the sealing substrate 311 are performed. The surface is attached via the material layer 321. In this attachment, it is not necessary to apply pressure.

  As described above, as illustrated in FIG. 3E, when the support substrate 301 and the sealing substrate 311 are bonded to each other through the material layer 321, the piezoelectric element 301 is bonded to the support substrate 301 and the sealing substrate 311. A quartz crystal element sealed in a container is obtained. The piezoelectric element 301 is sealed inside the recess 312 by the support substrate 301 and the sealing substrate 311 bonded via the material layer 321. Here, when the material layer 321 having a layer thickness of 0.2 nm or more and less than 1 nm is formed, the above-described sputtering state is stopped, and then (immediately after) the bonding between the support substrate 301 and the sealing substrate 311 is performed. Alternatively, it may be performed while the sputtering state is continued. It is important to attach the two substrates before the thickness of the material layer 321 reaches 1 nm.

  Here, the material layer 321 is formed over the entire area of the support substrate 301, for example. For this reason, for example, the material layer 321 is formed over the plurality of wirings 307 formed on the support substrate 301. When the material layer 321 is made of a metal such as Al, the wirings 307 are connected by the metal layer. However, since the material layer 321 is as thin as less than 1 nm, it has a high insulating property and does not cause an electrical short circuit between the wirings 307. As shown in FIG. 4, for example, in the case of a metal such as Au or Ti, if the layer thickness is less than 1 nm, the film resistance value is high, and sufficient insulation can be secured.

[Embodiment 3]
Next, a third embodiment of the present invention will be described. In Embodiment 3, an optical element will be described as an example, and in particular, an optical element manufactured by bonding will be described as an example.

  In the optical element (quartz element) manufactured by the bonding method in the present embodiment, for example, as shown in FIG. 5, a quartz substrate 501 and a quartz substrate 502 are bonded via a material layer 503. The quartz substrate 501 has an average surface roughness Ra <1 nm, and the quartz substrate 502 has an average surface roughness Ra of 0.3 nm.

  For example, the quartz substrate 501 and the quartz substrate 502 are carried into a processing chamber of a film forming apparatus (sputtering apparatus) using a vacuum film forming method (for example, sputtering method). Subsequently, formation of the material layer 503 by the vacuum film formation method is started on the bonding surface of the support substrate 302 and the bonding surface of the quartz substrate 502. For example, the formation of the material layer 503 on the bonding surface of the quartz substrate 501 and the formation of the material layer 503 on the bonding surface of the quartz substrate 502 are started by a well-known sputtering method. For example, a magnetron sputtering apparatus may be used as the film formation apparatus, and formation of the material layer 503 made of Al may be started using aluminum (Al) as a target.

  As described above, after the deposition of the material layer 503 is started in the processing chamber, the bonding surface of the quartz substrate 501 and the bonding surface of the quartz substrate 502 on which the material layer 503 having a layer thickness of 0.2 nm or more and less than 1 nm is formed. Are attached via the material layer 503. For example, when a 0.4 nm material layer 503 is formed on each bonding surface, adhesion is performed. In this attachment, it is not necessary to apply pressure.

  As described above, the quartz crystal substrate 501 and the quartz crystal substrate 502 are bonded to each other through the material layer 503. The bonding of the quartz substrate 501 and the quartz substrate 502 may be performed after (after) the sputtering state described above after the material layer 503 having a thickness of 0.2 nm or more and less than 1 nm is formed. It may be performed while the sputtering state is continued. It is important to attach the two substrates before the thickness of each of the material layer 503 formed on the bonding surface of the crystal plate 501 and the material layer 503 formed on the bonding surface of the crystal plate 502 becomes 1 nm. It is.

  Here, the characteristic evaluation result of the optical element in this Embodiment mentioned above is demonstrated. The transmitted wavefront aberration was measured for the optical element in the present embodiment and the optical element bonded with a conventional organic adhesive, and the PV (Peak-Valley) values were compared. The transmitted wavefront aberration is measured by a Fizeau interferometer, the measurement wavelength is 632.8 nm, and the measurement region is a circular region having a diameter of 13 mm at the center of the region connected by the material layer 503. As a result of the measurement, the PV value of the optical element bonded with the conventional organic adhesive is 1 wave or more, whereas the PV value of the optical element in the present embodiment is 0.1 wave or less. In particular, good characteristics were confirmed.

  The thickness of the organic adhesive is 10 μm or more, and non-uniformity occurs in the thickness of the adhesive layer at the time of bonding and fixing, and non-uniform refractive index due to partial stress at the time of bonding is caused by the organic adhesive. It is considered that the transmission wavefront in the bonded optical element is deteriorated. On the other hand, the optical element bonded by the bonding method according to the present embodiment has a very good transmitted wavefront because the total layer thickness of the material layer 503 to be a bonded portion is very thin and uniform, less than 2 nm. Is considered to be obtained.

  Note that the material layer 503 is not limited to Al, and may be a metal such as Au, Ti, Ta, Cu, or Cr, or a semiconductor material such as Si.

  By the way, in an optical element, it is important that a desired transmittance (high transparency) is obtained. As described above, the thickness of the material layer formed on one bonding surface is less than 1 nm. If there is, it does not affect transparency.

  For example, as shown in FIGS. 6 and 7, in the case of Cr and Si, when the thickness of the material layer formed on one joint surface is 0.2 nm or 0.4 nm, it is approximately 75% or more. The transmittance is obtained. Further, as shown in FIGS. 8 and 9, in the case of Cu, Ti, and Ta, if the thickness of the material layer formed on one bonding surface is 0.2 nm, a transmittance of approximately 75% or more is obtained. It has been. In the case of Ta, when the layer thickness is 0.4 nm, the transmittance in the wavelength region near 0.2 μm is about 70%.

  On the other hand, when the thickness of the material layer formed on one bonding surface exceeds 1 nm, the transmittance decreases as shown in FIG. In particular, in the case of Cu, when the thickness of the material layer formed on one bonding surface is 5 nm, the transmittance in the wavelength region near 2.5 μm is about 20%. In addition, as shown in FIG. 11, according to the optical element in the present embodiment, a decrease in the optical loss rate in the ultraviolet region is significantly suppressed as compared with the case where an organic adhesive is used for bonding. Will come to be. The loss rate is determined by the amount of light P transmitted through only two crystal substrates without using a material layer or an adhesive, and the amount of light P ′ transmitted through one crystal substrate bonded with a material layer or an adhesive. The loss rate (%) = {(PP ′) / P} × 100. In addition, the result of FIG. 11 has shown the result at the time of using Cu and Ti for a material layer.

  Next, the measurement result of the transmittance in a longer wavelength region (wavelength 2.5 to 5 μm) will be described. First, when an organic adhesive is used for bonding (bonding), as shown in FIG. 12, the absorption corresponding to the component contained in the adhesive is confirmed.

  In contrast to the above results, in the case of bonding using the material layer in the present embodiment, a higher transmittance is obtained as compared with the case where an organic adhesive is used, as shown in FIG.

  It should be noted that the present invention is not limited to the embodiment described above, and that many modifications can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, the material layer may be formed not only by the sputtering method but also by a known ion plating method. These are vacuum film formation methods in which film formation is performed under generation of plasma. Moreover, other vacuum film-forming methods, such as a vacuum evaporation method, may be used.

  In addition, when the substrates to be bonded are warped, a load may be applied between the two substrates so that the bonding surfaces come into contact with each other. In the above description, experimental results using Ti, Cr, and Ta have been described. However, the material layer is not limited to these materials, and other metal materials such as Au, Cu, and Al may be used. Not too long. The substance layer may be made of a semiconductor material such as Si or Ge.

  In the above description, the case where the quartz substrate is bonded to the quartz substrate has been described as an example. However, the present invention is not limited to this, and one substrate is a substrate made of another material such as glass or silicon. Can be joined in the same manner. In the above description, the quartz resonator is taken as an example of the piezoelectric element. However, the present invention is not limited to this, and the same applies to a well-known surface acoustic wave (SAW) element.

  DESCRIPTION OF SYMBOLS 101 ... Quartz substrate, 102 ... Material layer, 111 ... Quartz substrate, 131 ... Processing chamber.

Claims (8)

A first step of starting the formation of the material layer by the vacuum film formation method on the bonding surface of the first substrate and the bonding surface of the second substrate made of quartz in the processing chamber of the film formation apparatus by the vacuum film formation method;
In the processing chamber, the bonding surface of the first substrate and the bonding surface of the second substrate on which the material layers each having a layer thickness of 0.2 nm or more and less than 1 nm are formed are attached and bonded via the material layer. A second step of bonding the first substrate and the second substrate at each bonding surface; and
An average surface roughness of the bonding surface of the first substrate and the bonding surface of the second substrate is less than 1 nm. The joining method according to claim 1,
The bonding method, wherein the second step is performed after the formation of the material layer by the vacuum film-forming method is stopped. The joining method according to claim 1 or 2,
The bonding method according to claim 1, wherein the first substrate is made of quartz. In the joining method according to any one of claims 1 to 3,
The vacuum deposition method is a method selected from a sputtering method and an ion plating method. In the joining method according to any one of claims 1 to 4,
The bonding method according to claim 1, wherein the material layer is made of a metal or a semiconductor material.   A crystal element produced by the bonding method according to claim 1. The crystal element according to claim 6, wherein
The quartz crystal element is an optical element in which the first substrate and the second substrate made of quartz are bonded via the material layer. The crystal element according to claim 6, wherein
The crystal element includes a piezoelectric element mounted on the first substrate, and the second substrate including a recess formed corresponding to the piezoelectric element,
The piezoelectric element is sealed inside the recess by the first substrate and the second substrate bonded through the material layer.

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