JP5274462B2 - Composite substrate and functional device using composite substrate, and composite substrate and functional device manufacturing method - Google Patents

Description

  The present invention relates to a composite substrate in which a substrate on which a functional element is provided and a substrate made of glass ceramics are bonded, a functional device using the composite substrate, and a composite substrate and a method for manufacturing the functional device.

  A semiconductor substrate made of a semiconductor material such as silicon (Si) is widely used in various electronic devices. However, since the semiconductor substrate has low electrical insulation, there are problems such as generation of leakage current and deterioration of high frequency characteristics, and the semiconductor substrate may be used by being bonded to an insulating substrate such as glass or ceramics.

  In addition, another substrate such as a piezoelectric substrate provided with a surface acoustic wave (SAW) element may be used by being bonded to another substrate from the viewpoint of mechanical strength. In this case, a ceramic substrate may be used for reasons such as excellent rigidity and chemical resistance.

  Such a substrate made of a semiconductor or a piezoelectric material and a ceramic substrate can be bonded by, for example, interposing an inorganic bonding layer such as frit glass between two substrates and melting it.

  However, when the two substrates are bonded via frit glass, there is a problem that partial bonding failure is likely to occur due to the effects of unevenness and warpage on the bonding surfaces of the two substrates. As a result, there is a problem that the strength at the joint between the two substrates becomes weak.

  Therefore, there is a need for a composite substrate having a high strength at the joint between the two substrates to be joined, and a method for manufacturing such a composite substrate.

The functional device of the present invention includes a composite substrate having a first substrate on which a functional element is provided and a second substrate made of glass ceramics bonded to the first substrate by fusion, and a functional element provided on the first substrate. Have Crystallized glass exists at the interface between the first substrate and the second substrate. The second substrate has a crystallinity of 70% or more and is a glass ceramic laminate in which a plurality of glass ceramic layers are laminated. The composite substrate includes wiring provided in the glass ceramic laminate. The functional element includes a flow path. The wiring acts as a heater for heating the fluid in the flow path.

The functional device manufacturing method of the present invention includes a preparation step of preparing at least one glass ceramic green sheet and a first substrate, a step of bringing the glass ceramic green sheet and the first substrate into close contact by thermocompression, and integrating them. Firing a first substrate and a glass ceramic green sheet to form a composite substrate having a second substrate made of glass ceramics and the first substrate; and forming a functional element on the first substrate of the composite substrate; An application step of preparing a plurality of the glass ceramic green sheets in a preparation step, and applying a conductive paste to at least one of the plurality of glass ceramic green sheets before the adhesion step; and a plurality of glass ceramics Laminating a green sheet by thermocompression bonding to form a ceramic green laminate, In the step of preparing a semiconductor substrate on which a sacrificial layer has been formed in advance as a single substrate and bringing them into close contact and integrating them, the sacrificial layer is formed in the step of bringing the ceramic green laminate and the first substrate into close contact to form a functional element. Remove.

The composite substrate by the 1st Embodiment of this invention is shown, (a) is a side view, (b) is typical sectional drawing. It is a figure which shows the manufacturing method of the composite substrate of FIG. The functional device by the 2nd Embodiment of this invention is shown, (a) is a top view, (b) is sectional drawing in the straight line AA of (a), (c) has shown the bottom view. It is a figure for demonstrating an example of the method of forming the beam-like structure which consists of a silicon crystal on a ceramic laminated body. It is a figure which shows the manufacturing method of the functional device by the 2nd Embodiment of this invention. It is a figure which shows the manufacturing method of the functional device by the 2nd Embodiment of this invention. It is a figure which shows the structural example of the functional device by the 3rd Embodiment of this invention, (a) is a top view, (b) is sectional drawing in the straight line BB of (a). It is a side view which shows the structural example of the functional device by the 4th Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
(First embodiment)
As shown in FIG. 1, the composite substrate according to the first embodiment of the present invention includes a semiconductor substrate 2 and a ceramic substrate 3. The ceramic substrate 3 is directly bonded to the semiconductor substrate 2 by fusion. In the composite substrate 1 according to the present embodiment, the semiconductor substrate 2 is a silicon substrate, and the ceramic substrate 3 is made of glass ceramics (a sintered body of a mixture of crystallized glass and a ceramic filler). In the composite substrate 1, crystallized glass exists at the interface between the semiconductor substrate 2 and the ceramic substrate 3 as shown in FIG.

  Below, the manufacturing method of this composite substrate 1 is demonstrated using FIG. First, as shown in FIG. 2A, a semiconductor substrate 2 and a plurality of ceramic green sheets (hereinafter also referred to as “green sheets”) 4a to 4c are prepared. Here, the ceramic green sheet is made by mixing glass powder and ceramic powder with an organic binder, an organic solvent, a plasticizer, etc. to form a slurry, and the slurry is formed into a sheet by, for example, a doctor blade method or a calendar roll method. What you did.

  Examples of the ceramic powder include alumina, cordierite, β-quartz, and mullite. Examples of the glass powder include SiO 2 -B 2 O 3, SiO 2 -B 2 O 3 -Al 2 O 3, or SiO 2 -B 2 O 3 -Al 2 O 3 -MgO. The system etc. are mentioned.

  As the organic binder, those conventionally used in ceramic green sheets can be used. For example, acrylic, polyvinyl butyral, polyvinyl alcohol, polypropylene carbonate, or cellulose-based homopolymer or copolymer Coalescence is mentioned.

  As an organic solvent used in a slurry for forming a green sheet, the organic solvent, glass powder, ceramic powder, and an organic binder are kneaded so that a slurry having a viscosity suitable for forming a green sheet can be obtained. Those composed of hydrocarbons, ethers, esters, ketones, alcohols or the like are used.

  Next, as shown in FIG. 2 (b), the ceramic green laminate 4 is formed by thermocompression bonding the plurality of ceramic green sheets 4 a to 4 c at a pressure of 3 to 20 MPa and a temperature of 50 to 80 ° C.

  Next, as shown in FIG.2 (c), the ceramic raw laminated body 4 and the semiconductor substrate 2 are closely_contact | adhered and integrated by thermocompression bonding. For example, the thermocompression bonding is performed by combining the ceramic raw laminate 4 and the semiconductor substrate 2 and applying a pressure of 3 to 10 MPa at a temperature of 50 to 80 ° C.

  Furthermore, as shown in FIG. 2 (d), the ceramic raw laminate 4 integrated with the semiconductor substrate 2 is fired to obtain the composite substrate 1. In this case, for example, baking is performed at a temperature of 800 to 1000 ° C. in the atmosphere.

  Here, in the process of firing the ceramic raw laminate 4, if the firing temperature is equal to or higher than the glass transition temperature of the glass component of the green sheet, the glass component flows. At this time, the glass component fills the void gap inside the green sheet. And when a calcination temperature exceeds a glass transition point, crystallized glass will start crystallization. Since this crystallized glass precipitates from the contact interface between the glass component and the ceramic filler and from the contact interface between the glass component and the semiconductor substrate 2, in the composite substrate 1 after firing, the semiconductor substrate 2 and the ceramic laminate 3 There are glass microcrystals at the interface.

  In the method of manufacturing the composite substrate 1 according to the present embodiment, the ceramic green sheet of the ceramic raw laminate 4 has flexibility when the ceramic raw laminate 4 and the semiconductor substrate 2 are thermocompression bonded. Surface irregularities and warpage can be easily absorbed. Therefore, in the composite substrate 1 after firing, it is possible to reduce the bonding failure at the bonding interface between the semiconductor substrate 2 and the ceramic sintered body 3.

  Further, in the method for manufacturing the composite substrate 1 according to the present embodiment, the semiconductor substrate 2 suppresses the shrinkage of the ceramic raw laminate 4 in the planar direction, and the ceramic raw laminate 4 shrinks in the thickness direction (stacking direction). To do. That is, the semiconductor substrate 2 restrains the shrinkage of the ceramic raw laminate 4 in the planar direction. Therefore, the dimensional accuracy of the ceramic sintered body 3 can be increased, and as a result, the dimensional accuracy of the composite substrate 1 can be increased.

  Furthermore, in the composite substrate 1 obtained by the above-described manufacturing method, crystals precipitated in the firing process exist at the interface between the ceramic substrate 3 and the semiconductor substrate 2. For example, when the ceramic substrate 3 and the semiconductor substrate 2 are bonded via frit glass, the semiconductor substrate 2 and the ceramic substrate 3 are bonded by cooling the glass liquid phase in the frit glass and solidifying the glass. Is done. In that case, since the glass component present at the bonding interface between the semiconductor substrate 2 and the ceramic substrate 3 is amorphous glass, there is no crystal phase at the bonding interface. In the composite substrate 1 according to the present embodiment, since crystals exist at the interface between the semiconductor substrate 2 and the ceramic substrate 3, the strength at the joint between the silicon substrate and the ceramic sintered body is further increased.

  In the above description, the semiconductor substrate 2 and the ceramic substrate 3 are bonded as the composite substrate 1, but instead of the semiconductor substrate 2, for example, quartz, lead zirconate titanate (PZT), or lithium tantalate. A piezoelectric substrate made of (LiTaO3) or the like, a dielectric substrate made of barium titanate (BaTiO3) or the like, a magnetic substrate such as a ferrite substrate, or a sapphire substrate may be used. Even when these substrates are used as substrates to be bonded to the ceramic substrate (hereinafter also referred to as “first substrate”), it is possible to reduce bonding defects at the bonding interface between the first substrate and the ceramic substrate 3. At the same time, the dimensional accuracy of the composite substrate 1 can be increased.

  Further, even when a substrate other than the semiconductor substrate 2 is used, glass crystals are precipitated in the firing process at the interface between the first substrate and the ceramic substrate, so that the strength at the joint between the first substrate and the ceramic substrate is increased. Becomes stronger.

(Second Embodiment)
Next, a functional device using the composite substrate 1 according to the first embodiment will be described. In FIG. 3A, the lid 17 is omitted for simplification of illustration.

  As shown in FIG. 3, the microstructure device 11 according to the second embodiment of the present invention has a composite substrate 14A in which a semiconductor substrate 12 and a ceramic substrate 13 are bonded. The ceramic substrate 13 is a ceramic laminate composed of a plurality of ceramic layers.

  A microstructure 15 is formed on the surface of the semiconductor substrate 12. The microstructure 15 is a structure obtained by processing the semiconductor substrate 12 using a so-called semiconductor micromachining process, and has a size of about 100 nm to several hundred μm, for example. Here, the micro structure 15 will be described by taking a micro electro mechanical mechanism (hereinafter referred to as “MEMS”) as an example. MEMS is an electromechanical system composed of minute parts (microscale devices) fabricated by making full use of semiconductor microfabrication technology. The microstructure device 11 including a MEMS is, for example, an optical sensor such as an RF-MEMS that switches high-speed RF signals, various sensors such as an acceleration sensor or a Gyro sensor, or a micromirror device in which a fine mirror body is movably formed. It is a device.

  A multilayer wiring layer 16 is formed inside the ceramic laminate 13. Further, the microstructure device 11 includes a lid 17 (sealing body) that protects the microstructure 15 and performs hermetic sealing. The lid 17 can prevent the microstructure 15 from being contaminated by dust from the outside.

  The composite substrate 14A is a substrate in which a semiconductor substrate 12 made of silicon crystal and a ceramic layer constituting the ceramic laminate 13 are laminated and integrated. The composite substrate 14A can be formed by attaching a ceramic green sheet to the semiconductor substrate 12 and sintering the ceramic green sheet. Here, the ceramic green sheet is made into a slurry by mixing glass powder and ceramic powder with an organic binder, an organic solvent, a plasticizer, and the like, and the slurry is formed into a sheet by, for example, a doctor blade method or a calendar roll method. Say things. In this case, the glass substrate contained in the ceramic layer is fused to the semiconductor substrate 12 by firing, so that the semiconductor substrate 12 and the ceramic laminate 13 are integrated.

  The semiconductor substrate 12 is, for example, a single crystal or polycrystalline silicon substrate using a silicon wafer. The semiconductor substrate 12 may partially have a silica layer, a polysilicon layer, or a metal layer in accordance with the design of the microstructure 15.

  Electrode pads 18 that electrically connect the multilayer wiring layer 16 to an external wiring substrate are formed on the lower surface of the composite substrate 14A.

  Hereinafter, as in the microstructure device 11 shown in FIG. 3, a processing process when forming a beam-like structure made of silicon crystal on the ceramic laminate 13 will be described with reference to FIGS. Will be described.

  First, as shown in FIGS. 4A and 4B, a multilayer substrate is obtained in which a ceramic multilayer body 13 is bonded to a semiconductor substrate 12 having a sacrificial layer 19. Here, FIG. 4A is a cross-sectional view of the multilayer substrate, and FIG. 4B is a plan view of the multilayer substrate. In this laminated substrate, a groove pattern having a desired pattern shape is applied to the semiconductor substrate 12, a metal film such as gold (Al), which becomes the sacrificial layer 19, is embedded in the groove portion, and a ceramic green sheet is adhered to the semiconductor substrate 12 Obtained by sintering the ceramic green sheet.

  4 (c) and 4 (d) are partially formed by forming a resist made of a metal film having a desired shape on the semiconductor substrate 12 shown in FIGS. 4 (a) and 4 (b) and using dry etching. The structure of the laminated substrate when the silicon crystal is removed is shown.

  4E and 4F show the configuration of the laminated substrate when the sacrificial layer 19 is removed using a dry etching process with respect to the laminated substrate shown in FIGS. 4C and 4D. Show. By removing the sacrificial layer 19 in this way, a beam structure made of silicon can be formed.

  The thickness of the semiconductor substrate 12 is desirably 0.05 to 0.5 mm. When the thickness of the semiconductor substrate 12 is set to 0.05 mm or more, the thickness of the microstructure 15 can be ensured. Therefore, the strength of the microstructure 15 is strong and fatigue failure due to operation can be suppressed.

  Furthermore, since the thickness of the semiconductor substrate 12 is 0.5 mm or less, the removal amount in the etching process of the semiconductor micromachining process is not excessive, and the aspect ratio of the microstructure 15 is reduced, and the microstructure 15 The increase in the formation cost of can be suppressed.

  In this way, by bonding the ceramic laminate 13 to the semiconductor substrate 12 on which the microstructure 15 is formed so as to cover the semiconductor substrate 12, in particular, the microstructure 15 has a high frequency such as RF-MEMS. In the case of driving with the above, it is possible to manufacture the microstructure device 11 that is resistant to power supply or ground noise and external electromagnetic noise.

  Moreover, since the ceramic laminate 13 is made of a glass ceramic sintered body, a low resistance metal conductor mainly composed of Ag, Cu, Au, AgPd, or AgPt can be used as the multilayer wiring layer 16. Electric loss in the multilayer wiring layer 16 can be suppressed. This is particularly preferable when the microstructure 15 is an RF-MEMS.

  The glass ceramic sintered body desirably has a low coefficient of thermal expansion and a high degree of crystallinity. Preferably, the coefficient of thermal expansion is 2.5 to 3.5 × 10 −6 / ° C., and the degree of crystallinity is 70%. It is good to be the above. In order to obtain such a glass ceramic sintered body, for example, crystallized glass on which cordierite, β-quartz, or β-spodumene is precipitated as glass powder, low thermal expansion such as cordierite or mullite as ceramic powder Each filler may be used.

  When the thermal expansion coefficient of the ceramic layer is 2.5 to 3.5 × 10 −6 / ° C., the thermal expansion coefficients of the ceramic layer and the semiconductor substrate 12 are close enough to be generated between the ceramic layer and the semiconductor substrate 12. Thermal stress can be reduced. Therefore, warpage of the semiconductor substrate 12 and the ceramic layer and occurrence of cracks in the semiconductor substrate 12 can be suppressed.

  The ceramic laminate 13 is preferably made of a material having a crystallinity of 70% or more. In this case, damage to the ceramic layer from the processing etching gas or etching liquid used in the semiconductor micromachining process can be sufficiently suppressed, and corrosion of the ceramic laminate 13 can be suppressed. As a result, degranulation from the ceramic layer can be suppressed, and failure of the microstructure 15 due to adhesion of dust (degranulation) to the microstructure 15 can be suppressed.

  The multilayer wiring layer 16 is disposed inside the ceramic laminate 13 and is formed using a known green sheet lamination method. The green sheet lamination method includes the following steps. First, a hole processing is performed on a ceramic green sheet using a known technique such as punching or laser processing, and the hole is filled with a paste made of metal powder made of Ag or Cu. Thereafter, a conductor layer is formed on the green sheet by a known method such as screen printing. A plurality of these green sheets are laminated and fired.

  The multilayer wiring layer 16 functions as an electrical conduction path between the microstructure 15 and an external substrate such as a printed wiring board. Since the multilayer wiring layer 16 can route the wiring inside the ceramic laminate 13, the electrode pad 18, that is, the secondary mounting electrode pad 18 is provided at a desired position on one main surface of the composite substrate 14A. However, electrical connection between the microstructure 15 formed on the other main surface and the secondary mounting electrode pad 18 can be performed. As a result, the degree of freedom in designing the arrangement of the secondary mounting electrode pads 18 is increased, and the mounting reliability can be improved.

  In addition, by using ceramic multilayer wiring technology, compared with the case where a via conductor is provided on a glass substrate, the adhesion between the via conductor disposed inside the insulating substrate and the insulating substrate is kept good, and the via It is possible to suppress leakage from the conductor. In particular, when the via conductor of each ceramic layer has a non-perpendicular structure, the hermetic reliability can be further improved.

  The multilayer wiring layer 16 preferably has a wiring that forms at least a part of a drive circuit that drives the microstructure 15. Since at least a part of the drive circuit for driving the microstructure 15 is included in the ceramic laminate 13, it is not necessary to form the entire drive circuit on the surface of the semiconductor substrate 12. And since a drive circuit and the microstructure 15 can be arrange | positioned three-dimensionally, the design freedom of the microstructure device 11 can be raised and the microstructure device 11 can be reduced in size. Therefore, in the method of forming a plurality of microstructures 15 on one wafer and manufacturing a plurality of microstructure devices 11 from one wafer, the number of microstructure devices 11 that can be formed per wafer increases. There is an effect that the cost per unit price of the microstructure device 11 can be reduced.

  Further, when the microstructure 15 is an electrostatic drive type MEMS, an electrode (hereinafter referred to as “upper electrode”) is formed on one main surface of the semiconductor substrate 12 on which the MEMS is formed. By using the lower electrode as the part, a switching device for driving the movable part of the electrostatically driven MEMS can be formed by using an electric field generated when a voltage is applied between the upper electrode and the lower electrode. it can.

  When the lower electrode is disposed inside the ceramic laminate 13, unlike the case where the lower electrode is formed on the semiconductor substrate 12 on which the MEMS is formed, the semiconductor substrate 12 is not affected by the position and area of the lower electrode. Since other configurations such as electrostatic drive MEMS and wiring can be provided on the semiconductor device, the degree of freedom in placement of the electrostatic drive MEMS and the process design freedom in the semiconductor micromachining process can be increased, and the microstructure device 11 can be reduced in size. Further, unlike the case where the lower electrode is formed on the semiconductor substrate on which the MEMS is formed, it is not necessary to provide an insulating layer on the lower electrode and to provide other structures such as electrostatic drive type MEMS and wiring on the insulating layer. Therefore, it is possible to form the electrostatic drive type MEMS and the wiring without being affected by the unevenness of the lower electrode. Therefore, it is possible to increase the degree of freedom of arrangement of the electrostatic drive type MEMS and wiring, and the degree of freedom of process design of the semiconductor micromachining process.

  When the microstructure 15 is a magnetic field drive type MEMS, a part of the multilayer wiring layer 16 is formed in a coil shape as a drive circuit, and the magnetic field drive type MEMS is generated by a magnetic field generated by a current flowing through the coil pattern. The working electrode can be driven.

  When the driving coil pattern is arranged inside the ceramic laminate 13, unlike the case where the driving coil and the magnetic field driving type MEMS are formed together on the semiconductor substrate 12, the driving coil pattern is interposed on the driving coil via another layer. Since it becomes unnecessary to form the magnetic field drive type MEMS, it is possible to form the magnetic field drive type MEMS, wiring, and the like without being affected by the unevenness of the drive coil. Therefore, it is possible to increase the degree of freedom of arrangement of the magnetic field driven MEMS and wiring, and the degree of process design of the semiconductor micromachining process. In addition, in order to secure a magnetic field, even if the wiring length of the spiral wiring serving as the driving coil is increased, other wiring can be three-dimensionally arranged, so that the size of the microstructure device 11 is increased. As a result, it is possible to suppress a decrease in the number of microstructure devices 11 that can be formed per wafer and an increase in cost per unit price of the microstructure devices 11.

  The lid 17 hermetically seals the microstructure 15 and suppresses intrusion of dust and moisture from the outside. The lid 17 can be mounted on the composite substrate 14 using a brazing material such as AuSn, solder such as SnAgCu solder, or glass frit. The lid 17 is preferably made of Pyrex (registered trademark) glass or silicon in order to reduce thermal stress with the composite substrate 14.

  Next, a method for manufacturing such a microstructure device 11 will be described with reference to FIGS.

  First, as shown in FIG. 5A, a plurality of glass ceramic green sheets 20 are prepared. This ceramic green sheet is formed by adding a glass powder and ceramic powder to an organic binder, organic solvent, plasticizer, etc. to make a slurry, and forming the slurry into a sheet using the doctor blade method or the calender roll method. Can be obtained.

  Examples of the ceramic powder include alumina, cordierite, β-quartz, and mullite. Examples of the glass powder include SiO 2 -B 2 O 3, SiO 2 -B 2 O 3 -Al 2 O 3, or SiO 2 -B 2 O 3 -Al 2 O 3 -MgO. The system etc. are mentioned. Here, when cordierite is selected as the ceramic powder and crystallized glass in which 70% or more of cordierite is precipitated as the glass powder, the thermal expansion coefficient of the obtained glass ceramic sintered body is 2.5 to 3.5. × 10 −6 / ° C. The crystallinity is 70% or more, which is more suitable as the microstructure device 11.

  As the organic binder, those conventionally used in ceramic green sheets can be used. For example, acrylic, polyvinyl butyral, polyvinyl alcohol, polypropylene carbonate, or cellulose-based homopolymer or copolymer Coalescence is mentioned.

  The organic solvent used in the slurry for forming the green sheet is, for example, carbonized so that a slurry having a viscosity suitable for green sheet forming can be obtained by kneading the organic solvent, glass powder, ceramic powder, and organic binder. Those made of hydrogen, ethers, esters, ketones, alcohols, or the like are used.

  Next, as shown in FIG. 5 (b), the glass ceramic green sheet 20 produced in FIG. 5 (a) is subjected to mechanical processing such as die processing, laser processing, micro drilling, or punching as necessary. A through hole is formed. A well-known technique such as screen printing is applied to the conductor paste 21 for forming a wiring conductor in which a metal powder such as Ag, Cu, Ag-Pt, or Ag-Pd and a glass powder are mixed with an appropriate organic binder and solvent. Fill with.

  Next, as shown in FIG. 5 (c), metal powder such as Ag, Cu, Ag-Pt, or Ag-Pd and an appropriate organic binder and solvent are added to the surface of the glass ceramic green sheet 20. The mixed wiring conductor paste 22 is applied to a glass ceramic green sheet by screen printing or the like to form the multilayer wiring layer 16.

  Next, as shown in FIG.5 (d), the glass ceramic green sheet in which the multilayer wiring layer 16 was formed is thermocompression-bonded by the pressure of 3-20 MPa and the temperature of 50-80 degreeC, and the ceramic raw laminated body 23 is produced. . At this time, it is desirable that the glass ceramic green sheet used for the uppermost layer of the ceramic raw laminate 23, that is, the layer bonded to the semiconductor substrate 12, contains a melting component that melts when heated during adhesion.

  Next, as shown in FIG.5 (e), the semiconductor substrate 12 and the ceramic raw laminated body 23 are thermocompression-bonded by the pressure of 3-10 MPa, and the temperature of 50-80 degreeC. In this manufacturing method, the electrode 24 is formed on the surface of the semiconductor substrate 12 in contact with the ceramic raw laminate 23. Here, when the uppermost layer of the ceramic raw laminate 23 contains a melting component that is melted by the heat at the time of adhesion, the semiconductor substrate 12 and the ceramic raw laminate 23 can be satisfactorily adhered with low pressure. The sacrificial layer 19 may be partially formed on the semiconductor substrate 12 in advance.

  Next, as shown in FIG. 6A, the ceramic raw laminate 23 heat-pressed to the semiconductor substrate 12 is fired to form a composite substrate 14B including a plurality of microstructure devices. Here, when the multilayer wiring layer 16 is made of Ag, Ag-Pt, Ag-Pd or the like, firing is performed in the air, and when the multilayer wiring layer 16 is made of Cu, firing is performed in a nitrogen atmosphere. . The firing temperature is in the range of 800 to 1000 ° C.

  At this time, since the shrinkage of the ceramic raw laminate 23 in the planar direction is suppressed by the semiconductor substrate 12, the ceramic raw laminate 23 contracts only in the laminating direction, and the dimensional accuracy in the planar direction can be kept high.

  Next, as shown in FIGS. 6B and 6C, a plurality of MEMS is formed as the microstructure 15 on the semiconductor substrate 12 of the composite substrate 14B. Hereinafter, a case where the semiconductor substrate 12 is made of silicon single crystal and the sacrificial layer 19 is made of silica will be described as an example.

  The MEMS can be formed by protecting a desired portion of the semiconductor substrate 12 with a resist or the like and removing the non-protected portion by etching or the like. For example, KOH or tetramethylammonium hydroxide aqueous solution (TMAH) can be used for etching the silicon single crystal. When the sacrificial layer 19 (SiO 2) is etched using hydrofluoric acid or the like after the silicon single crystal is etched, the etching rate of the silicon single crystal and the silica layer are greatly different. Therefore, only the silica layer is etched, and the MEMS 15 made of the silicon single crystal Can be configured in a state where a part of the substrate is floated from the ceramic laminate.

  Next, as shown in FIG. 6D, a substrate (hereinafter referred to as “sealing substrate”) 26 having a plurality of lid portions corresponding to each MEMS 15 is prepared. The sealing substrate 26 is, for example, a silicon wafer in which a concave portion is formed in a portion corresponding to the MEMS of the composite substrate 14B. This silicon wafer can be formed, for example, by protecting a region other than the region corresponding to the concave portion of the silicon wafer with a resist and etching the silicon wafer with a KOH solution. For example, after the glass frit material is formed on the sealing substrate 26 in a desired pattern shape, the sealing substrate 26 and the composite substrate 14B are applied to the sealing substrate 26 and the composite substrate 14B at a predetermined temperature and pressure. It can join by pressing. In addition to joining the sealing substrate 26 and the composite substrate 14B with frit glass, for example, a frame-like conductor pattern is formed on each joint surface of the sealing substrate 26 and the composite substrate 14B, and the conductor patterns are connected to each other. You may join using an AuSn brazing material or SnAgCu solder.

  Next, as shown in FIG. 6E, the sealing substrate 26 and the composite substrate 14B are separated into individual pieces by dicing or the like for each MEMS 15 and for each 17 parts of the lid, so that a single microstructure device 11 is obtained. Can be formed. In FIGS. 5A to 5E and FIGS. 6A to 6D, in order to understand the unit configuration of the microstructure device, it is necessary to separate each microstructure device. Although the cutting line is shown, until the step of FIG. 6D, the sealing substrate 26 and the composite substrate 14B are one substrate.

  Further, as shown in FIG. 6C, after the sacrificial layer 19 is removed, the microstructure 15 is provided on the surface of the semiconductor substrate 12 facing the ceramic laminate, and the portion removed by etching is then removed by polysilicon. In the case of filling with a thin film such as, it is not necessary to provide the lid 17.

  In the method of manufacturing the composite substrate 1 according to the present embodiment, the ceramic green sheet of the ceramic raw laminate 23 has flexibility when the ceramic raw laminate 23 and the semiconductor substrate 12 are thermocompression bonded. Surface irregularities and warpage can be easily absorbed. Therefore, in the composite substrate 14B after firing, it is possible to reduce the bonding failure at the bonding interface between the semiconductor substrate 12 and the ceramic sintered body.

  Further, in the method for manufacturing the composite substrate 11 according to the present embodiment, the semiconductor substrate 12 suppresses the shrinkage of the ceramic green laminate 23 in the planar direction, and the ceramic green laminate 23 shrinks in the thickness direction. That is, the semiconductor substrate 12 restrains the shrinkage of the ceramic green laminate 23 in the planar direction. Therefore, the dimensional accuracy of the ceramic sintered body can be increased, and as a result, the dimensional accuracy of the composite substrate 11 can be increased.

  Further, in the above-described method for manufacturing a microstructure device, since the ceramic green sheet that is in close contact with the semiconductor substrate 12 contains a melting component that melts during heating at the time of close contact, the semiconductor substrate 12 and the glass ceramic green sheet are reduced. It can be adhered by pressure. As a result, cracking of the semiconductor substrate 12 can be suppressed when the semiconductor substrate 12 and the ceramic green sheet are brought into close contact with each other by applying pressure.

  In the above description, the semiconductor substrate 12 and the ceramic substrate made of the ceramic laminate 13 are integrated to form the composite substrate 14B. However, the semiconductor substrate 12 and the ceramic substrate made of a single ceramic layer are integrated. The composite substrate 14B may be formed.

(Third embodiment)
Next, another functional device using the composite substrate 1 according to the first embodiment will be described with reference to FIG. In FIG. 7, the same components as those of the microstructure device 11 of FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

  The microstructure device 31 shown in FIG. 7 is different from the microstructure device 11 of FIG. 3 in that the microstructure 15 has a flow path 32 and the fluid flowing through the flow path 32 in the composite substrate 14A. This is a point having an action part 33 that performs a predetermined action. Here, the microstructure 15 is a variety of sensors such as a microchemical system or a gas sensor including a minute flow path manufactured by making full use of a semiconductor microfabrication technique.

  In the case of the microstructure device 31 according to the present embodiment, a microchannel that three-dimensionally intersects the microchannel 32 formed by processing the semiconductor substrate 12 can be formed inside the ceramic laminate 13. Accordingly, the degree of freedom in designing the microstructure device 31 can be increased, and the microstructure device 31 can be reduced in size. Further, by providing an opening leading to the flow path on the main surface other than the main surface bonded to the semiconductor substrate 12 in the ceramic laminate 13, the reagent can be input and discharged from the opening, so that the fluid can be easily supplied and discharged. Can be done.

In addition, the microstructure device 31 according to the present embodiment can be provided with an action portion 33 such as a micro valve or a micro pump. Examples of the action unit 33 include an actuator that operates based on a difference in thermal expansion coefficient such as a thermal bimorph actuator, a micropump such as an electroosmotic flow pump that uses electroosmotic flow, or a heater. These action portions 33 may be provided on the semiconductor substrate 12 in the composite substrate 14 or may be provided on the ceramic laminate 13. When provided on the semiconductor substrate 12, it can be formed by a semiconductor micromachining process.

The microvalve or micropump formed on the semiconductor substrate 12 is electrically connected to the electrode pad 18 provided on the other main surface of the ceramic laminate 13 using the multilayer wiring layer 16 formed inside the ceramic laminate 13. Since they can be connected, power can be easily supplied from the outside.

  Further, as shown in FIG. 7B, a heater for heating the fluid in the flow path 32 may be provided inside the ceramic laminate 13 as the action portion 33. The heater can be formed by using a green sheet lamination method as with the multilayer wiring layer 16.

  When the microstructure 15 is μTAS, in order to seal the flow path 32, Pyrex (registered trademark) glass may be bonded to the semiconductor substrate 12 by anodic bonding so as to cover the flow path 32. desirable. Voltage application to the semiconductor substrate 12 during anodic bonding can be performed by applying a voltage to the silicon substrate from the bonding electric supply unit provided on the other main surface of the ceramic laminate 13.

  The microstructure device 31 according to the present embodiment can form a flow path that is three-dimensionally intersected with the fine flow path obtained by processing the semiconductor substrate 12 inside the ceramic laminate 13, so that the flow path is formed only in the two-dimensional direction. The degree of freedom in design can be increased as compared with a microstructure device (such as μTAS). As a result, the microstructure device 31 can be reduced in size.

  Further, a conduction path for supplying power from the outside to the action portion 33 such as a microvalve or micropump formed on the semiconductor substrate 12 or the action portion 33 such as a heater formed inside the ceramic laminate 13. Can be formed using the multilayer wiring layer 16 inside the ceramic laminate 13, the degree of freedom in designing the microstructure device 31 can be increased, and the microstructure device 31 can be reduced in size. Further, the degree of freedom in designing the arrangement of the secondary mounting electrode pads 18 is increased, and the mounting reliability can be improved.

  A channel 32 is provided on the surface facing the ceramic substrate by providing a sacrificial layer in advance on the surface of the semiconductor substrate 12 facing the ceramic substrate, and then removing only the sacrificial layer 19 by wet etching or the like. Can do. In such a case, there is no need to provide Pyrex (registered trademark) glass for sealing the flow path 32.

(Fourth embodiment)
Next, another functional device using the composite substrate 1 according to the fourth embodiment will be described with reference to FIG.

  As shown in FIG. 8, the functional device 41 according to the fourth embodiment of the present invention is a surface acoustic wave device, and includes a composite substrate 44 in which a piezoelectric substrate 42 and a ceramic substrate 43 are bonded. A comb-shaped electrode 45 is formed on the surface of the piezoelectric substrate 42. Here, the two comb-shaped electrodes 45 are shown, but the electrodes used in the device using the surface acoustic wave are not limited to this, and can be arbitrarily designed according to the application. The piezoelectric substrate 42 is made of, for example, quartz, lead zirconate titanate (PZT), or lithium tantalate.

  By bonding the piezoelectric substrate 42 to the ceramic substrate 43 in this way, the strength is maintained by the ceramic substrate 42, and thus the thickness of the piezoelectric substrate 42 can be reduced. This facilitates processing of the comb-shaped electrode 45 formed on the surface of the piezoelectric substrate 42.

  The manufacturing method of the functional device 41 according to the present embodiment is the same as the manufacturing method of the functional device 11 according to the second embodiment when the semiconductor substrate 2 is the piezoelectric substrate 42. In the method of manufacturing the functional device 11, the MEMS 15 is formed by processing the semiconductor substrate 2 of the composite substrate 14A. However, in the method of manufacturing the functional device 41 according to the present embodiment, the semiconductor device 2 is adhered to the piezoelectric substrate 42. After the glass ceramic green sheet is fired to form the composite substrate 44, a comb-shaped electrode 45 is formed by forming a conductor film on the piezoelectric substrate 42 and patterning it, for example.

  According to the composite substrate 41 according to the present embodiment, it is possible to reduce the bonding failure at the bonding interface between the piezoelectric substrate 42 and the ceramic substrate 43 and to increase the dimensional accuracy of the composite substrate 41. Further, since glass crystals are deposited at the interface between the piezoelectric substrate 42 and the ceramic substrate 43 in the firing process, the strength at the joint between the piezoelectric substrate 42 and the ceramic substrate 43 is further increased.

  Note that the functional element provided on the first substrate bonded to the ceramic substrate is not only a structure body partially formed on the first substrate such as a MEMS or a crystal resonator, but also the comb electrode 45 described above. And a structure that includes the entire first substrate, such as a piezoelectric element having a piezoelectric substrate 42.

  Note that the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. For example, a sapphire substrate and a ceramic substrate may be bonded as a composite substrate. In that case, a thin film may be formed on the sapphire substrate of the composite substrate by various epitaxial growth methods, and thereafter an electrical functional element or an optical functional element such as various electronic devices may be provided.

Claims (7)

Glass having a first substrate on which a functional element is provided and a second substrate made of glass ceramics bonded to the first substrate by fusion bonding, and crystallized at an interface between the first substrate and the second substrate And the second substrate is a composite substrate having a crystallinity of 70% or more ,
A functional element provided on the first substrate,
The composite substrate includes wiring provided in the glass ceramic laminate,
The second substrate is a glass ceramic laminate in which a plurality of glass ceramic layers are laminated,
The functional element includes a flow path;
The wiring is a functional device that acts as a heater for heating the fluid in the flow path . Before SL wiring function device of claim 1 wherein forming at least a part of the driving circuit for driving the functional element. The functional device of Claim 1 or Claim 2 provided with the sealing body which covers and seals the said functional element. A preparation step of preparing at least one glass ceramic green sheet and a first substrate;
An adhesion step for bringing the glass ceramic green sheet and the first substrate into close contact with each other by thermocompression bonding; and
Firing the glass ceramic green sheet integrated with the first substrate to form a composite substrate having a second substrate made of glass ceramics and the first substrate ;
A functional element forming step of forming a functional element on the first substrate of the composite substrate ,
In the preparation step, preparing a plurality of the glass ceramic green sheets,
Before the adhesion step,
An application step of applying a conductor paste to at least one of the plurality of glass ceramic green sheets;
A laminating step of laminating the plurality of glass ceramic green sheets by thermocompression bonding to form a ceramic green laminate;
Have
In the adhesion step, the ceramic raw laminate and the first substrate are adhered to each other,
In the preparation step, a semiconductor substrate on which a sacrificial layer is formed in advance is prepared as the first substrate,
In the functional element forming step, the sacrificial layer is removed.
A method of manufacturing a functional device . In the preparation step, preparing the glass ceramic green sheet prepared by mixing an organic binder with glass powder and ceramic filler,
The method for producing a functional device according to claim 4 , wherein in the adhesion step, the organic binder in the glass ceramic green sheet is melted. The manufacturing method of the functional device of Claim 4 provided with the connection process of connecting the sealing body which covers and seals the said functional element on the said composite substrate after the said functional element formation process. Prior Symbol functional device forming step, forming a plurality of functional elements to the first substrate of the composite substrate,
The method of manufacturing a functional device according to claim 4 , further comprising: dividing the composite substrate into individual functional elements to obtain a plurality of functional devices.

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