JP5122888B2 - OSCILLATOR, METHOD FOR MANUFACTURING OSCILLATOR, AND OSCILLATOR - Google Patents

Description

  The present invention relates to an oscillator having a structure for correcting a change in resonance frequency due to temperature, and a method for manufacturing the oscillator.

  Conventionally, crystal oscillators using crystal oscillators have been used for clock pulse generation in digital devices and wireless devices. However, silicon oscillators that use silicon, which is more mass-productive and easier to design frequencies, are used. Attempts have been made to manufacture oscillators.

  The silicon oscillator utilizes a resonance mode of a cantilever beam or a doubly supported beam held so as to be swingable. Since the resonance frequency is defined by the cross-sectional size and length of the beam, the design is easy. In addition, since elements can be collectively formed on a large-diameter silicon substrate, mass productivity is high, and it is also possible to manufacture using a conventional CMOS IC manufacturing line.

  However, the silicon oscillator has a drawback that the resonance frequency varies greatly with temperature. Therefore, as shown in Patent Document 1, an oscillator incorporating a circuit for correcting temperature characteristics is provided.

  FIG. 15 is a block diagram showing an outline of a conventional oscillator. The oscillator 30 includes an oscillator 31, a drive circuit 32, a PLL circuit 33, a temperature sensor 34, a temperature characteristic correction circuit 35, and a correction data memory 36.

  The oscillator 31 is resonated by a signal from the drive circuit 32, and the resonance signal is output to the PLL circuit 33. A temperature sensor 34 is provided in the vicinity of the oscillator 31 and outputs a signal corresponding to the measured temperature to the temperature characteristic correction circuit 35. The correction data of the resonance frequency at each temperature of the oscillator 31 is stored in the correction data memory 36, and the temperature characteristic correction circuit 35 stores the correction data from the correction data memory 36 based on the temperature received from the temperature sensor 34. Read and output to the PLL circuit 33. The PLL circuit 33 modulates the frequency of the resonance signal input from the oscillator 31 based on the correction data, and outputs it to the outside.

The drive circuit 32, PLL circuit 33, temperature sensor 34, temperature characteristic correction circuit 35, and correction data memory 36 can be integrated as a single CMOS IC chip.
JP 2004-23634

  However, the oscillator 30 configured as described above has the following drawbacks. That is, the oscillator 30 must be equipped with a PLL circuit 33, a temperature sensor 34, a temperature characteristic correction circuit 35, and a correction data memory 36 in order to correct the temperature characteristic. The temperature characteristics are not always within the correctable range, and the temperature characteristics of each oscillator 31 are different. Therefore, there is a possibility that the temperature characteristics cannot be corrected efficiently.

  Further, in the method of modulating the frequency by the PLL circuit, since the temperature characteristic correction data is digitally processed, the fluctuation of the frequency output to the outside is steep and there is a possibility that the temperature characteristic cannot be corrected efficiently.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an oscillator and a method of manufacturing the oscillator in which temperature characteristics are efficiently corrected.

  The present invention provides the following means in order to solve the above problems.

  An oscillator according to the present invention includes at least two or more anchors arranged at a predetermined interval, a vibration unit connected to the anchor and held so as to be swingable, and a predetermined interval from the vibration unit. A drive electrode arranged to be opposed to the gap, a detection electrode arranged to be opposed to the vibrating section at a predetermined interval, and a material connected to the anchor and more heat than the material constituting the vibrating section. And a temperature characteristic correction substrate made of a material having a small expansion coefficient.

  In the resonator according to the present invention, the resonance frequency of the vibration part tends to change due to a change in temperature, but the temperature characteristic correction substrate is made of a material having a smaller thermal expansion coefficient than the material constituting the vibration part. Since an internal stress is applied to the oscillator, it is possible to obtain an oscillator that corrects the change in the resonance frequency of the vibration part due to a change in temperature.

  The resonator according to the present invention is the above-described resonator according to the present invention, wherein the number of the anchors is two, the vibrating portion is linear, and both ends are connected to the anchor. Is.

  In the resonator according to the present invention, since the vibration part is linear, the internal stress of the vibration part generated due to the difference in the thermal expansion coefficient between the vibration part and the temperature characteristic correction substrate is only in the axial direction. Thus, it is possible to obtain an oscillator that efficiently corrects the change in the resonance frequency of the vibration part due to the above.

  The resonator according to the present invention is the above-described resonator according to the present invention, wherein the vibrating portion is made of silicon, and the temperature characteristic correction substrate is any one material of quartz, silicon nitride, diamond, and invar. It is characterized by comprising.

  In the resonator according to the present invention, it is possible to correct a change in the resonance frequency of the vibration part due to a change in temperature, and the vibration part is made of silicon, so that the shape is formed by using a processing technique conventionally used in semiconductor manufacturing or micromachine manufacturing. Therefore, it is possible to obtain an oscillator with high resonance frequency accuracy.

  The resonator according to the present invention is the above-described resonator according to the present invention, wherein the vibrating section includes an active layer made of silicon, a buried oxide film layer made of silicon oxide, and a support layer made of silicon. It is formed from an active layer of a substrate.

  In the resonator according to the present invention, it is possible to correct a change in the resonance frequency of the vibration part due to a change in temperature, and the vibration part is formed from the active layer of the Silicon On Insulator substrate, so that the thickness can be processed with high accuracy. And an accurate oscillator can be obtained.

  Further, the method for manufacturing an oscillator according to the present invention includes at least two or more anchors arranged at a predetermined interval, a vibrating part connected to the anchor and held swayably, A vibrating part forming step of forming a driving electrode arranged to face the gap and a detection electrode arranged to face the vibrating part with a predetermined gap; and configuring the vibrating part And a bonding step of bonding a temperature characteristic correction substrate made of a material having a smaller thermal expansion coefficient than the material to the anchor.

  In the method for manufacturing an oscillator according to the present invention, the resonance frequency of the vibration part tends to change due to a change in temperature, but the temperature characteristic correction substrate is made of a material having a smaller thermal expansion coefficient than the material constituting the vibration part. Since an internal stress is applied to the vibration part, it is possible to manufacture an oscillator that corrects the change in the resonance frequency of the vibration part due to a change in temperature.

  The method for manufacturing an oscillator according to the present invention is the method for manufacturing an oscillator according to the present invention, wherein, in the vibration part forming step, the vibration part, the anchor, the drive electrode, and the detection electrode are formed from silicon. In the bonding step, a temperature characteristic correction substrate made of any one of quartz, silicon nitride, diamond, and invar is bonded to the anchor.

  In the method for manufacturing an oscillator according to the present invention, it is possible to correct a change in the resonance frequency of the vibrating part due to a change in temperature, and since the vibrating part is made of silicon, a processing technique conventionally used in semiconductor manufacturing or micromachine manufacturing is used. Thus, the shape can be formed, and a highly accurate oscillator can be manufactured.

  The method for manufacturing an oscillator according to the present invention is the method for manufacturing an oscillator according to the present invention, wherein the anchor and the temperature characteristic correction substrate are bonded in the bonding step when the anchor and the temperature characteristic correction substrate are bonded. A surface activated bonding method is used in which a surface of a temperature characteristic correction substrate is activated by irradiating the surface of the temperature characteristic correction substrate with plasma or an ion beam, and the anchor and the temperature characteristic correction substrate are contacted and bonded. It is.

  In the method for manufacturing an oscillator according to the present invention, the anchor and the temperature characteristic correction substrate are bonded using the surface activated bonding method. Therefore, bonding can be performed at a temperature from room temperature to about 400 ° C. Since the stress is small, the temperature characteristic can be easily corrected by the stress applied to the vibration part.

  Further, in the method for manufacturing an oscillator according to the present invention, a film forming step of forming a sacrificial layer on a temperature characteristic correction substrate and a device layer made of a material having a larger thermal expansion coefficient than the temperature characteristic correction substrate, The device layer is selectively removed and at least two or more anchors arranged at a predetermined interval, a vibration part connected to the anchor and held swayably, and the vibration part and the predetermined part And a vibration part forming step of forming a drive electrode arranged to face the gap and a detection electrode arranged to face the vibration part with a predetermined gap. It is a feature.

  In the resonator manufacturing method according to the present invention, since the vibration part is formed directly on the temperature characteristic correction substrate, the thickness of the device can be reduced.

  A method for manufacturing an oscillator according to the present invention is the method for manufacturing an oscillator according to the present invention, wherein the temperature characteristic correction substrate is any one of quartz, silicon nitride, diamond, and invar in the film forming step. The sacrificial layer is made of silicon oxide, and the device layer is made of silicon.

  In the method for manufacturing an oscillator according to the present invention, since the vibration part is directly formed on the temperature characteristic correction substrate, the thickness of the device can be reduced and the vibration part is made of silicon. In addition, the shape can be formed by using a processing technique used for manufacturing a micromachine, and a highly accurate oscillator can be manufactured.

  The method for manufacturing an oscillator according to the present invention selectively removes the active layer of a silicon on insulator substrate including an active layer made of silicon, a buried oxide film layer made of silicon oxide, and a support layer made of silicon. And at least two or more anchors arranged at a predetermined interval, a vibration part connected to the anchor and held so as to be swingable, and arranged to face the vibration part at a predetermined interval A vibration part forming step of forming the drive electrode and the detection electrode arranged to face the vibration part with a predetermined interval; and the vibration part, the anchor, the drive electrode, and the detection electrode. Bonding to the transfer substrate, removing the support layer, and replacing the buried oxide film layer with a portion other than the region in contact with the anchor, the drive electrode, and the detection electrode The transfer step to be removed, the temperature characteristic correction substrate made of a material having a smaller thermal expansion coefficient than silicon, and the buried oxide film layer left in the region of the anchor, the drive electrode, and the detection electrode are joined, and And a bonding step for removing the substrate.

  In the method for manufacturing an oscillator according to the present invention, since the vibration part is formed from the active layer of the silicon on insulator substrate, the thickness can be processed with high accuracy, and an accurate oscillator can be obtained. In addition, since it is bonded to the temperature characteristic correction substrate after bonding to the transfer substrate and the support layer is removed, it is possible to correct a change in the resonance frequency of the vibration part due to a change in temperature and to reduce the thickness of the device.

  The method for manufacturing an oscillator according to the present invention is the method for manufacturing an oscillator according to the present invention, wherein, in the transfer step, the vibrator, the anchor, the drive electrode, the detection electrode, and the transfer substrate Are bonded with an adhesive resin that loses its bonding strength when irradiated with ultraviolet rays, and the transfer substrate is removed by losing the bonding force of the adhesive resin with irradiation of ultraviolet rays in the bonding step.

  In the method for manufacturing an oscillator according to the present invention, since the vibration part is formed from the active layer of the silicon on insulator substrate, the thickness can be processed with high accuracy, and an accurate oscillator can be obtained. In addition, since it is bonded to the temperature characteristic correction substrate after bonding to the transfer substrate and the support layer is removed, it is possible to correct a change in the resonance frequency of the vibration part due to a change in temperature and to reduce the thickness of the device. Furthermore, in the transfer step, the vibration part, anchor, drive electrode and detection electrode are joined to the transfer substrate with an adhesive resin that loses the binding force when irradiated with ultraviolet rays, so that the transfer substrate can be easily removed.

  The method for manufacturing an oscillator according to the present invention is the method for manufacturing an oscillator according to the present invention, wherein, in the joining step, the buried oxide remaining in the region of the anchor, the drive electrode, and the detection electrode is provided. When bonding the film layer and the temperature characteristic correction substrate, the surface of the buried oxide film layer and the temperature characteristic correction substrate is activated by irradiating plasma or ion beam, and the buried oxide film layer It is characterized by using a surface activated bonding method in which the temperature characteristic correction substrate is bonded in contact.

  In the method for manufacturing an oscillator according to the present invention, since the vibration part is formed from the active layer of the silicon on insulator substrate, the thickness can be processed with high accuracy, and an accurate oscillator can be obtained. In addition, since it is bonded to the temperature characteristic correction substrate after bonding to the transfer substrate and the support layer is removed, it is possible to correct a change in the resonance frequency of the vibration part due to a change in temperature and to reduce the thickness of the device. In addition, since the buried oxide film layer and the temperature characteristic correction substrate are bonded using the surface activation bonding method, bonding can be performed at a temperature of about 400 ° C. from room temperature, and the residual stress due to bonding is small. The temperature characteristics can be easily corrected by the stress applied to the.

  An oscillator according to the present invention includes the above-described oscillator according to the present invention and a drive circuit that inputs a drive signal to a drive electrode of the oscillator.

  Since the oscillator according to the present invention has the oscillator having the temperature characteristic correction substrate, the temperature characteristic can be corrected efficiently.

  According to the resonator according to the present invention and the method for manufacturing the resonator according to the present invention, the resonance frequency of the vibration part is corrected by the difference in thermal expansion coefficient between the vibration part and the temperature characteristic correction substrate. An efficient oscillator can be obtained.

(First embodiment)
Hereinafter, the first embodiment according to the present invention will be described with reference to FIGS. 1 to 7, taking as an example an oscillator 1 having a vibrating portion 2 that is connected to two anchors 3 at both ends and is swingably held. To explain.

  FIG. 1 is a plan view of an oscillator 1 according to the first embodiment, and FIG. 2 is a cross-sectional view of the oscillator 1 taken along the line AA ′ of FIG. For simplicity, the temperature characteristic correction substrate 5 is omitted in FIG. 1, and the drive electrode 4 and the detection electrode 14 are omitted in FIG.

  In the first embodiment, an SOI (Silicon On Insulator) substrate 6 made of silicon is selected as a material for forming the oscillator 1, and the oscillator 1 is formed using the active layer 7 of the SOI substrate 6. It was formed.

  The oscillator 1 includes two anchors 3, a vibration part 2 that is connected to the anchors 3 at both ends and is swingably held, and a drive electrode 4 that is provided to face the vibration part 2 at a predetermined interval. And a detection electrode 14 provided so as to face the vibration part 2 at a predetermined interval, and a material bonded to the anchor 3 and having a smaller thermal expansion coefficient than silicon, which is a material forming the vibration part 2. And a temperature characteristic correction substrate 5.

  The anchor 3, the drive electrode 4, and the detection electrode 14 are fixed to the support layer 9 of the SOI substrate 6 through the buried oxide film layer 8 of the SOI substrate 6.

  FIG. 3 is a block diagram showing the oscillator 20. The oscillator 20 includes an oscillator 1 and a drive circuit 21.

  A drive signal having a predetermined frequency generated by the drive circuit 21 is input to the drive electrode 4 of the oscillator 1. The vibration part 2 vibrates according to this drive signal. An electric signal is extracted from the vibration of the vibration unit 2 as a change in capacitance between the vibration unit 2 and the detection electrode 14 and output to the outside. The resonance frequency of the vibration unit 2 is determined by Equation 1.

  Here, f0 is the resonance frequency of the vibration part 2, L is the length of the vibration part 2, W is the width of the vibration part 2, ESi is the Young's modulus of silicon, a is a coefficient determined by the shape of the vibration part 2, and αSi is silicon Is a first-order coefficient obtained by Taylor expansion of the Young's modulus with temperature, σ is an internal stress in the axial direction of the vibrating portion 2, and ΔT is a temperature change from a predetermined reference temperature. Since the Young's modulus depends on temperature, the resonance frequency f0 changes with temperature.

  In order to correct the change in the resonance frequency f0 due to the temperature, the internal stress σ may be changed so that the inside of the square root of Equation 1 is only ESi. Σ at this time is expressed by Equation 2.

  Since the vibration part 2 and the temperature characteristic correction substrate 5 are respectively connected to the anchor 3, they are integrally deformed when the temperature changes. Since the temperature characteristic correction substrate 5 has a smaller thermal expansion coefficient than that of the vibration part 2, the vibration part 2 is less elongated than when the temperature characteristic correction board 5 is not connected to the anchor 3, and the axial compressive stress is increased. And its magnitude σ is expressed by Equation 3.

  Here, EX is the Young's modulus of the material that forms the temperature characteristic correction substrate 5, CSi is the thermal expansion coefficient of silicon that is the material that forms the vibration part 2, and CX is the thermal expansion coefficient of the material that forms the temperature characteristic correction substrate 5 It is.

  Therefore, in order to correct the change in the resonance frequency f0 due to the temperature, the material of the temperature characteristic correction substrate 5 and the vibration part so that the internal stress magnitude σ of the vibration part 2 represented by Expression 2 and Expression 3 are matched. The length L and the width W of 2 may be determined.

  Since the thermal expansion coefficient of silicon is approximately 3.3 × 10 ^ −6 / K, as a material for the temperature characteristic correction substrate 5, for example, quartz having a thermal expansion coefficient CX = 0.5 × 10 ^ −6 / K, CX = Silicon nitride with 3.1 × 10 ^ -6 / K, Diamond with CX = 1.1 × 10 ^ -6 / K, Invar with CX = 2 × 10 ^ -6 / K, etc. Can do.

  For each of the above materials as the material of the temperature characteristic correction substrate 5, the relationship of the internal stress σ of the vibration part 2 with respect to the length L when the width W of the vibration part 2 is assumed to be 10 micrometers is expressed by Expressions 2 and 3 Plotted according to 4 shows quartz, FIG. 5 shows silicon nitride, FIG. 6 shows diamond, and FIG. 7 shows invar. There is a length L of the vibration part 2 in which the stresses of the expressions 2 and 3 are equal. When the resonator 1 is actually designed, the lengths L and W of the vibration unit 2 are selected so that a predetermined resonance frequency is obtained and σ in the expressions 2 and 3 are equal.

  Next, a method for manufacturing the resonator 1 according to the first embodiment configured as described above will be described with reference to FIGS. 8 and 9 correspond to cross-sectional views taken along the line AA 'in FIG. In addition, the oscillator 1 can be formed with a large number of oscillators 1 on the same substrate. However, in this embodiment, it is assumed that one of the many oscillators 1 is extracted for simplicity. To do.

  The manufacturing method of the first embodiment is a method of manufacturing by appropriately performing the vibration part forming step and the joining step.

  First, a vibration part formation process is performed.

  As shown in FIG. 8A, an SOI substrate 6 made of silicon is prepared.

  Next, as shown in FIG. 8B, a predetermined region of the active layer 7 is selectively removed by a predetermined depth to form a movable gap 10. Various methods can be selected as a method for selectively removing a predetermined position of the active layer 7. For example, a mask is formed on the surface of the active layer 7 by using a lithography technique, and TMAH (Tetramethyl Ammonium Hydroxide) is used. A predetermined region is selectively removed by selecting a method such as wet etching using a strong alkaline etchant such as an aqueous solution or an aqueous potassium hydroxide solution, or dry etching using RIE (Reactive Ion Etching) using SF6 plasma. The depth of the movable gap 10 may be such that the vibrating part 2 is held in a swingable manner without contacting the temperature characteristic correction substrate 5, and may be, for example, about 1 micrometer or more.

  Next, as shown in FIG. 8C, a predetermined region of the active layer 7 is selectively removed to form the vibrating portion 2, the anchor 3, the drive electrode 4 (not shown), and the detection electrode 14 (not shown). As a method for selectively removing the predetermined region, wet etching using a strong alkaline etchant, dry etching using RIE, or the like can be selected as in the case of forming the movable gap 10. In addition, when the Deep RIE technique using the Bosch process is used, etching can be performed while maintaining a high aspect ratio and the angle of the side wall close to vertical. In this embodiment, since the SOI substrate 6 is used, the buried oxide film layer 8 can be used as an etching stop.

  Next, as shown in FIG. 9A, the buried oxide film layer 8 existing between the vibrating portion 2 and the support layer 9 is selectively removed, and the vibrating portion 2 is held swingably by the anchor 3. To the state. As a method for removing the buried oxide film layer 8, wet etching using a hydrogen fluoride aqueous solution, dry etching using hydrogen fluoride gas, or the like can be selected.

  At this time, it is necessary to prevent the buried oxide film layer 8 existing between the anchor 3 and the drive electrode 4 and the detection electrode 14 and the support layer 9 from being removed. For this purpose, the area and width of the anchor 3, the drive electrode 4, and the detection electrode 14 are relatively larger than those of the vibration part 2, and a number of fine holes through which the hydrogen fluoride etchant can pass are formed in the vibration part 2. The method can be selected.

  Next, a joining process is performed.

  In the bonding process, first, a temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than silicon, such as quartz, silicon nitride, diamond, or invar, is prepared.

  Next, as shown in FIG. 9B, the temperature characteristic correction substrate 5 is bonded to the anchor 3 to form the oscillator 1. Various methods can be selected for joining.

  For example, in the case of using the anodic bonding method, the bonding surface of the anchor 3 is made of silicon or aluminum, and a borosilicate glass thin film containing alkali metal ions such as sodium is formed on the surface of the temperature characteristic correction substrate 5 and is about 200 ° C. or higher. When a voltage of 200 V to 1000 V is applied using the anchor 3 as an anode and the temperature characteristic correction substrate 5 as a cathode, the anchor 3 and the temperature characteristic correction substrate 5 are firmly bonded by an anodic bonding reaction.

  Further, when the gold-silicon eutectic bonding method is used, the bonding surface of the anchor 3 is made of silicon, and a gold thin film is formed on the temperature characteristic correction substrate 5. Next, when the anchor 3 and the temperature characteristic correction substrate 5 are brought into contact with each other by heating to a temperature equal to or higher than the eutectic point of gold and silicon, for example, 350 ° C. or higher, the gold and silicon are melted by a eutectic reaction and firmly bonded. The

  Further, when the gold-tin eutectic bonding method or the silver-tin eutectic bonding method is used, a thin film of an alloy made of gold and tin or an alloy made of silver and tin is formed on at least one of the anchor 3 and the temperature characteristic correction substrate 5. When the film 3 is heated to a temperature equal to or higher than the eutectic point of gold and tin or the eutectic point of silver and tin and the anchor 3 and the temperature characteristic correction substrate 5 are brought into contact with each other, an alloy thin film made of gold and tin or silver and tin is formed. Are melted by the eutectic reaction and firmly bonded. The eutectic point of gold and tin is about 270 ° C., and the eutectic point of silver and tin is about 250 ° C. In addition, a thin film made of gold or silver is formed on one of the anchor 3 and the temperature characteristic correction substrate 5, and a thin film made of tin is formed on the other. Then, the anchor 3 and the temperature characteristic are heated by heating above the eutectic point. The correction substrate 5 may be brought into contact.

  In addition, when the surface activated bonding method is used, the surface of the anchor 3 and the temperature characteristic correction substrate 5 is irradiated with a plasma or ion beam of argon, oxygen, nitrogen, etc., and the surface is modified with an active functional group or dangling on the surface. After the ring bond is formed, when the anchor 3 and the temperature characteristic correction substrate 5 are brought into contact with each other by heating from room temperature to about 400 ° C., the contact surfaces are chemically bonded and firmly bonded.

  Alternatively, the anchor 3 and the temperature characteristic correction substrate 5 may be bonded and bonded using an epoxy resin or a polyimide resin.

  As described above, in the first embodiment according to the present invention, the temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than that of silicon that is the material of the vibration unit 2 is connected to both ends of the vibration unit 2. Since the stress is generated in the vibrating part 2 due to the difference in thermal expansion coefficient between the vibrating part 2 and the temperature characteristic correction substrate 5 when the temperature of the oscillator 1 changes, 3 can correct the temperature change of the resonance frequency of the vibration unit 2 according to the relationship shown in FIG.

(Second Embodiment)
Next, a second embodiment according to the present invention will be described with reference to FIGS. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 10 is a plan view of the resonator 1 according to the second embodiment, and FIG. 11 is a cross-sectional view of the resonator 1 taken along the line BB ′ of FIG. For simplicity, the drive electrode 4 and the detection electrode 14 are omitted in FIG.

  The oscillator 1 includes two anchors 3, a vibration part 2 that is connected to the anchors 3 at both ends and is swingably held, and a drive electrode 4 that is provided to face the vibration part 2 at a predetermined interval. And a temperature characteristic correction substrate 5 made of a material having a thermal expansion coefficient smaller than that of silicon which is bonded to the anchor 3 and forms the vibrating portion 2.

  The anchor 3 and the drive electrode 4 are fixed to the temperature characteristic correction substrate 5 via the sacrificial layer 12.

  The temperature characteristic correction substrate 5 is made of a material having a smaller temperature expansion coefficient than the material of the vibration unit 2. For example, when silicon is selected as the material of the vibration unit 2, the thermal expansion coefficient of silicon is approximately 3.3 × 10 ^ −6 / K. Therefore, as the material of the temperature characteristic correction substrate 5, for example, the thermal expansion coefficient CX = 0.5 Quartz with × 10 ^ -6 / K, silicon nitride with CX = 3.1 × 10 ^ -6 / K, diamond with CX = 1.1 × 10 ^ -6 / K, CX = 2 × 10 An invar such as ^ -6 / K can be selected.

  In addition, any one of germanium, silicon carbide, silicon nitride, and metal can be selected as the material of the vibration unit 2. In this case, a material having a smaller thermal expansion coefficient than these materials must be selected as the material for the temperature characteristic correction substrate 5.

  As in the case of the first embodiment, the resonance frequency of the vibration unit 2 varies with temperature change according to Equation 1. In order to cancel the fluctuation of the resonance frequency, a stress in the axial direction represented by the expression 2 may be applied to the vibration unit 2.

  By the way, since the temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than that of the vibration part 2 is connected to the anchor 3, the axial compressive stress expressed by Expression 3 acts on the vibration part 2 due to the difference in the thermal expansion coefficient. . Therefore, the material may be selected so that the magnitudes of the stresses in the axial direction expressed by Expression 2 and Expression 3 are equal, and the length L and width W of the vibration unit 2 may be selected.

  Next, a method for manufacturing the resonator 1 according to the second embodiment configured as described above will be described with reference to FIG. FIG. 12 corresponds to a cross-sectional view taken along the line BB ′ of FIG. In addition, the oscillator 1 can be formed with a large number of oscillators 1 on the same substrate. However, in this embodiment, it is assumed that one of the many oscillators 1 is extracted for simplicity. To do.

  The manufacturing method of the second embodiment is a method of manufacturing by appropriately performing a film forming process and a vibration part forming process.

  First, a film forming process is performed.

  As shown in FIG. 12A, a temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than silicon, such as quartz, silicon nitride, diamond, or invar, is prepared.

  Next, as shown in FIG. 12B, a sacrificial layer 12 having a predetermined thickness is formed. The sacrificial layer 12 is for removing the vibrating part 2 so that the vibrating part 2 can swing in a vibrating part forming step described later. Accordingly, it is desirable that the thickness be thinner in order to prepare the removal process. However, in order to make the vibration part 2 swingable, it is necessary to prevent the vibration part 2 from coming into contact with the temperature characteristic correction substrate 5, so that the thickness of the sacrificial layer 12 is about 0.5 μm, for example. The meter should be about 2 micrometers.

  As the material of the sacrificial layer 12, a silicon oxide film formed by plasma CVD (Chemical Vapor Deposition) technology or the like is usually used. However, in order to remove the silicon oxide film, it is necessary to use a hydrogen fluoride aqueous solution or hydrogen fluoride gas. Therefore, when quartz or silicon nitride is used as the material of the temperature characteristic correction substrate 5, the temperature characteristic correction substrate 5 is In order not to be etched, it is necessary to form a protective film such as a silicon thin film on the surface of the temperature characteristic correction substrate 5 and to stack the sacrificial layer 12 thereon.

  Next, as shown in FIG. 12C, a device layer 13 having a predetermined thickness is formed. The device layer 13 often uses a silicon thin film formed by LPCVD (Low Pressure Chemical Vapor Deposition) technology or plasma CVD technology in consideration of ease of processing, mass productivity, and vibration characteristics of the vibration part. When a material other than silicon is selected to form the device layer 13, it is necessary to select a material for the temperature characteristic correction substrate 5 having a smaller thermal expansion coefficient than that of the device layer 13.

  Next, a vibration part formation process is performed.

  First, as shown in FIG. 12D, a predetermined region of the device layer 13 is selectively removed to form the vibrating portion 2, the anchor 3, the drive electrode 4 (not shown), and the detection electrode 14 (not shown). As a method for selectively removing a predetermined region, when a silicon thin film is selected as the material of the device layer 13, wet etching using a strong alkaline etchant or dry etching using RIE is selected as in the manufacturing method of the first embodiment. can do. In addition, when the Deep RIE technique using the Bosch process is used, etching can be performed while maintaining a high aspect ratio and the angle of the side wall close to vertical. If a silicon oxide film is selected as the material for the sacrificial layer 12, the sacrificial layer 12 can be used as an etching stop.

  Next, as shown in FIG. 12 (e), the sacrificial layer 12 existing between the vibration part 2 and the temperature characteristic correction substrate 5 is selectively removed, and the vibration part 2 is swingably held by the anchor 3. To the state. As a method for removing the sacrificial layer 12, when the sacrificial layer 12 is made of a silicon oxide film, wet etching using a hydrogen fluoride aqueous solution, dry etching using hydrogen fluoride gas, or the like can be selected.

  At this time, it is necessary to prevent the sacrificial layer 12 existing between the anchor 3 and the drive electrode 4 and the detection electrode 14 and the support layer 9 from being removed. For this purpose, the area and width of the anchor 3, the drive electrode 4, and the detection electrode 14 are relatively larger than those of the vibration part 2, and a number of fine holes through which the hydrogen fluoride etchant can pass are formed in the vibration part 2. The method can be selected.

  As described above, in the second embodiment according to the present invention, the temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than that of silicon that is the material of the vibration unit 2 is connected to both ends of the vibration unit 2. Since the stress is generated in the vibrating part 2 due to the difference in thermal expansion coefficient between the vibrating part 2 and the temperature characteristic correction substrate 5 when the temperature of the oscillator 1 changes, 3 can correct the temperature change of the resonance frequency of the vibration unit 2 according to the relationship shown in FIG.

  Unlike the case of the first embodiment, since the vibration part 2 is formed on the temperature characteristic correction substrate 5, the total thickness is reduced, the device can be miniaturized, and the manufacturing process can be simplified.

(Third embodiment)
Next, the manufacturing method of 3rd Embodiment based on this invention is demonstrated with reference to FIG.13 and FIG.14. Since the configuration of the third embodiment is the same as that of the second embodiment, a detailed description of the configuration and functions is omitted. Moreover, in the manufacturing method of this 3rd Embodiment, about the part same as the component in the manufacturing method of 1st Embodiment and the manufacturing method of 2nd Embodiment, the same code | symbol is attached | subjected and the detailed description is given. Omitted.

  The manufacturing method of the third embodiment is a method of manufacturing by appropriately performing a vibration part forming step, a transfer step, and a joining step.

  First, a vibration part formation process is performed.

  As shown in FIG. 13A, an SOI substrate 6 made of silicon is prepared.

  Next, as shown in FIG. 13B, a predetermined region of the active layer 7 is selectively removed to form the vibrating portion 2, the anchor 3, the drive electrode 4 (not shown), and the detection electrode 14 (not shown). As a method for selectively removing the predetermined region, wet etching using a strong alkaline etchant, dry etching using RIE, or the like can be selected as in the case of forming the movable gap 10. In addition, when the Deep RIE technique using the Bosch process is used, etching can be performed while maintaining a high aspect ratio and the angle of the side wall close to vertical. In this embodiment, since the SOI substrate 6 is used, the buried oxide film layer 8 can be used as an etching stop.

  Next, a transfer process is performed.

  In the transfer step, first, as shown in FIG. 13C, the vibrating portion 2, the anchor 3, the drive electrode 4 (not shown), and the detection electrode 14 (not shown) are joined to the transfer substrate 11.

  The material of the transfer substrate 11 is not particularly limited, but it is desirable that the transfer substrate 11 is not damaged even if the support layer 9 described later is polished or the buried oxide film layer 8 is removed. A substrate made of a material such as silicon, quartz, or borosilicate glass is preferably selected.

  Various methods can be selected as a method for joining the vibration unit 2, the anchor 3, the drive electrode 4, and the detection electrode 14 to the transfer substrate 11, but the polishing process of the support layer 9 and the removal process of the buried oxide film layer 8 It must be ensured that no peeling occurs. On the other hand, it is necessary that the transfer substrate 11 can be easily peeled off finally in the bonding step described later. In recent years, various methods have been developed for such a temporary bonding technique. For example, a resin that loses the bonding force by irradiation with ultraviolet rays has been proposed.

  Next, as shown in FIG. 14A, the support layer 9 is removed, and the buried oxide film layer 8 is exposed. As a method for removing the support layer 9, a method such as mechanical polishing, a CMP (Chemical Mechanical Polishing) technique, or dry etching by RIE or Deep RIE may be used alone or in combination.

  Next, as shown in FIG. 14B, the buried oxide film 8 other than the region of the anchor 3, the drive electrode 4 (not shown), and the detection electrode 14 (not shown) is selectively removed. As a method for selectively removing the buried oxide film 8, a mask may be formed in a region not to be removed using a lithography technique, and then wet etching using hydrofluoric acid or dry etching using RIE may be used.

  Further, in the present embodiment, the method of removing the buried oxide film 8 after forming the vibrating portion 2, the anchor 3, the drive electrode 4, and the detection electrode 14, bonding to the transfer substrate 11, and removing the support layer 9 has been described. After forming the vibrating portion 2, the anchor 3, the drive electrode 4 and the detection electrode 14, the buried oxide film layer other than the region sandwiched between the anchor 3 and the drive electrode 4 and the detection electrode 14 and the support layer 9 is wetted with hydrofluoric acid. It may be removed by etching or dry etching such as RIE and bonded to the transfer substrate 11. With this configuration, when the support layer 9 is removed, the buried oxide film 8 remains only in the portions of the anchor 3 and the drive electrode 4, and the buried oxide film layer 8 is strong as shown in FIG. It will not remain small. Therefore, the buried oxide film 8 can be easily left selectively at the anchor 3, the drive electrode 4, and the detection electrode 14.

  Next, a joining process is performed.

  First, a temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than silicon is prepared. Next, as shown in FIG. 14C, the buried oxide film layer 8 left connected to the anchor 3, the drive electrode 4 (not shown), and the detection electrode 14 (not shown) and the temperature characteristic correction substrate 5 are bonded.

  When the gold-tin eutectic bonding method or the silver-tin eutectic bonding method is used as the bonding method, at least one of the buried oxide film layer 8 left on the surfaces of the anchor 3 and the drive electrode 4 and the temperature characteristic correction substrate 5 is used. A thin film of an alloy made of gold and tin or an alloy made of silver and tin is formed on the substrate and heated to a temperature equal to or higher than the eutectic point of gold and tin or the eutectic point of silver and tin. When the characteristic correction substrate 5 is brought into contact, an alloy thin film made of gold and tin or silver and tin is melted by a eutectic reaction and is firmly bonded. The eutectic point of gold and tin is about 270 ° C., and the eutectic point of silver and tin is about 250 ° C. In addition, a thin film made of gold or silver is formed on one of the buried oxide film layer 8 and the temperature characteristic correction substrate 5, and a thin film made of tin is formed on the other. The film layer 8 and the temperature characteristic correction substrate 5 may be brought into contact with each other.

  When the surface activated bonding method is used, the surface of the buried oxide film layer 8 and the temperature characteristic correction substrate 5 is irradiated with a plasma or ion beam of argon, oxygen, nitrogen or the like to modify the surface with active functional groups. After the dangling bond is formed on the surface, when the buried oxide film layer 8 and the temperature characteristic correction substrate 5 are brought into contact with each other by heating from room temperature to about 400 ° C., the contact surfaces are chemically bonded and firmly To be joined.

  Alternatively, the buried oxide film layer 8 and the temperature characteristic correction substrate 5 may be bonded and bonded using an epoxy resin or a polyimide resin.

  Finally, as shown in FIG. 14D, the transfer substrate 11 is removed, and the oscillator 1 is obtained.

  As described above, in the third embodiment according to the present invention, the temperature characteristic correction substrate 5 made of a material having a smaller thermal expansion coefficient than that of silicon that is the material of the vibration unit 2 is connected to both ends of the vibration unit 2. Since the stress is generated in the vibrating part 2 due to the difference in thermal expansion coefficient between the vibrating part 2 and the temperature characteristic correction substrate 5 when the temperature of the oscillator 1 changes, 3 can correct the temperature change of the resonance frequency of the vibration unit 2 according to the relationship shown in FIG.

  Unlike the case of the first embodiment, since the vibration part 2 is formed on the temperature characteristic correction substrate 5, the total thickness is reduced, the device can be miniaturized, and the manufacturing process can be simplified.

  Moreover, since the vibration part 2, the anchor 3, the drive electrode 4, and the detection electrode 14 can be manufactured using an SOI substrate, the vibration part 2, the anchor 3, and the drive can be easily performed as compared with the case of the second embodiment. The thickness of the electrode 4 and the detection electrode 14 can be controlled.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 is a plan view of an oscillator according to a first embodiment of the invention. FIG. 2 is a cross-sectional view taken along line AA ′ of the oscillator shown in FIG. 1. 1 is a block diagram of an oscillator according to a first embodiment of the present invention. In the resonator according to the first embodiment of the present invention, the internal stress required for frequency correction of the vibration part 2 when the vibration part 2 is made of silicon and the temperature characteristic correction substrate 5 is made of quartz, the vibration part 2 and the temperature characteristic. 6 is a graph showing internal stress due to a difference in thermal expansion coefficient with the correction substrate 5. In the resonator according to the first embodiment of the present invention, the internal stress necessary for frequency correction of the vibration part 2 when the vibration part 2 is made of silicon and the temperature characteristic correction substrate 5 is made of silicon nitride, the vibration part 2 and the temperature. 6 is a graph showing internal stress due to a difference in thermal expansion coefficient with the characteristic correction substrate 5. In the resonator according to the first embodiment of the present invention, the internal stress necessary for frequency correction of the vibration part 2 when the vibration part 2 is made of silicon and the temperature characteristic correction substrate 5 is diamond, the vibration part 2 and the temperature characteristic. 6 is a graph showing internal stress due to a difference in thermal expansion coefficient with the correction substrate 5. In the resonator according to the first embodiment of the present invention, the internal stress necessary for frequency correction of the vibration part 2 when the vibration part 2 is made of silicon and the temperature characteristic correction substrate 5 is made of invar, the vibration part 2 and the temperature characteristic. 6 is a graph showing internal stress due to a difference in thermal expansion coefficient with the correction substrate 5. It is sectional drawing which shows the manufacturing method of the oscillator of 1st Embodiment which concerns on this invention. It is sectional drawing which shows the manufacturing method of the oscillator of 1st Embodiment which concerns on this invention. It is a top view of the oscillator of a 2nd embodiment concerning the present invention. It is sectional drawing in the BB 'line | wire of the oscillator shown in FIG. It is sectional drawing which shows the manufacturing method of the oscillator of 2nd Embodiment which concerns on this invention. It is sectional drawing which shows the manufacturing method of the oscillator of 3rd Embodiment which concerns on this invention. It is sectional drawing which shows the manufacturing method of the oscillator of 3rd Embodiment which concerns on this invention. It is a block diagram which shows the conventional oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Oscillator 2 Vibrating part 3 Anchor 4 Drive electrode 5 Temperature characteristic correction board | substrate 6 SOI board | substrate 7 Active layer 8 Embedded oxide film layer 9 Support layer 10 Movable gap 11 Transfer board | substrate 12 Sacrificial layer 13 Device layer 14 Detection electrode 20 Oscillator 21 Drive circuit DESCRIPTION OF SYMBOLS 30 Conventional oscillator module 31 Oscillator 32 Drive circuit 33 PLL circuit 34 Temperature sensor 35 Temperature characteristic correction circuit 36 Correction data memory

Claims (11)

At least two anchors arranged at predetermined intervals; and
A fixing portion connected to the bottom surface of the anchor and fixing the anchor;
A vibrating part connected to the anchor and held swingably;
A drive electrode arranged to face the vibrating portion with a predetermined interval;
A detection electrode arranged to face the vibrating portion with a predetermined interval;
A temperature characteristic correction substrate made of a material connected to the anchor and having a smaller coefficient of thermal expansion than the material constituting the vibrating section ;
The temperature characteristic correcting substrate is connected to a surface of the anchor facing the fixed portion . There are two anchors,
The oscillator according to claim 1, wherein the vibrating portion is linear and both ends are connected to the anchor. The vibrating part is made of silicon,
3. The oscillator according to claim 1, wherein the temperature characteristic correction substrate is made of any one of quartz, silicon nitride, diamond, and invar. The vibration part is formed of an active layer of a silicon on insulator substrate including an active layer made of silicon, a buried oxide film layer made of silicon oxide, and a support layer made of silicon , and the fixed part is made of the oxide film layer and the support layer oscillator of claim 3, wherein Rukoto is formed from. At least two or more anchors arranged at a predetermined interval, a vibration part connected to the anchor and held so as to be swingable, and a drive arranged to face the vibration part at a predetermined interval A vibrating part forming step of forming an electrode and a detection electrode arranged to face the vibrating part with a predetermined interval;
And a bonding step of bonding a temperature characteristic correction substrate made of a material having a smaller thermal expansion coefficient to the anchor to the anchor. In the vibration part forming step, the vibration part, the anchor, the drive electrode, and the detection electrode are formed of silicon,
The method for manufacturing an oscillator according to claim 5, wherein a temperature characteristic correction substrate made of any one of quartz, silicon nitride, diamond, and invar is bonded to the anchor in the bonding step.   In the bonding step, when the anchor and the temperature characteristic correction substrate are bonded, the surface of the anchor and the temperature characteristic correction substrate is activated by irradiating plasma or an ion beam, and the anchor and the temperature are corrected. The method for manufacturing an oscillator according to claim 5 or 6, wherein a surface activated bonding method is used in which the substrate is bonded to a temperature characteristic correction substrate. The active layer of the silicon on insulator substrate having an active layer made of silicon, a buried oxide film layer made of silicon oxide, and a support layer made of silicon is selectively removed, and at least 2 disposed at a predetermined interval. One or more anchors, a vibration part connected to the anchors and held swingably, a drive electrode arranged to face the vibration part with a predetermined gap, and the vibration part with a predetermined gap A vibrating part forming step of forming a detection electrode disposed so as to be opposed to each other,
The vibration portion, the anchor, the drive electrode, and the detection electrode are joined to a transfer substrate, the support layer is removed, and the buried oxide film layer is a portion other than a region that is in contact with the anchor, the drive electrode, and the detection electrode. A transfer process for removing
A bonding step of bonding the temperature characteristic correction substrate made of a material having a smaller thermal expansion coefficient than silicon and the buried oxide film layer left in the region of the anchor, the drive electrode, and the detection electrode, and removing the transfer substrate. And a method of manufacturing an oscillator. In the transfer step, the vibrating portion, the anchor, the drive electrode and the detection electrode, and the transfer substrate are joined by an adhesive resin that loses the binding force by irradiation with ultraviolet rays,
9. The method of manufacturing an oscillator according to claim 8 , wherein the transfer substrate is removed by losing the bonding force of the adhesive resin by irradiation of ultraviolet rays in the bonding step. In the bonding step, when the buried oxide film layer and the temperature characteristic correction substrate left in the region of the anchor, the drive electrode, and the detection electrode are bonded to the temperature characteristic correction substrate, the buried oxide film layer and the temperature characteristic correction substrate A surface activated bonding method is used in which the surface is activated by irradiating the surface of the substrate with plasma or an ion beam, and the buried oxide film layer and the temperature characteristic correction substrate are brought into contact with each other and bonded. 10. A method for manufacturing an oscillator according to 8 or 9 . The oscillator according to any one of claims 1 to 4,
An oscillator comprising: a drive circuit that inputs a drive signal to a drive electrode of the oscillator.

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