JP2005159715A - Micro-resonator, manufacturing method thereof and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro-resonator having a desired resonant frequency among a plurality of resonant frequencies, a method of manufacturing the micro-resonator capable of manufacturing the micro-resonator without entirely changing a manufacturing process, and an electronic equipment provided with this micro-resonator. <P>SOLUTION: The micro-resonator 10 has a configuration in which a resonator 40 is disposed between a fixed electrode 22 having a comb tooth part 21 and a fixed electrode 32 having a comb tooth part 31. The resonator 40 has a movable electrode 24 disposed so that a comb tooth part 23 is engaged with the comb tooth part 21 of the fixed electrode 22 and a movable electrode 34, so that a comb tooth part 33 is engaged with the portion 31 of the fixed electrode 32. The resonator 40 is supported by a supporting portion 42 extending in a Y direction, and out of beams 42a-42c formed in the supporting portion 42, any one of combinations among all the beams 42a-42c and beams 42b or 42, or only the beam 42c is fixed, corresponding to the resonant frequency. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a microresonator including a resonator that vibrates minutely at a specific resonance frequency, a manufacturing method thereof, and an electronic device including the microresonator.

  In recent years, research and development for manufacturing ultra-compact and ultra-high-performance electronic components using MEMS (Micro Electro Mechanical System) technology has been actively conducted. There are a wide variety of electronic components using MEMS technology, and one type is a microresonator. In the microresonator, for example, an insulating film made of an oxide film is formed on a substrate such as a silicon substrate, and the comb teeth of the comb-shaped fixed electrode and the comb teeth of the comb-shaped movable electrode are formed on the insulating film. It is the structure formed so that it might mesh | engage in parallel with respect to.

  The comb-shaped movable electrode is coupled to a support portion having a spring property supported on a silicon substrate, and the comb-shaped fixed electrode and the comb-shaped movable electrode are engaged with each other. One set is arranged on each side of the support portion. The comb-shaped movable electrode and the support portion constitute a resonator. Further, two electrode terminals connected to each of the comb-shaped fixed electrodes and an electrode terminal as a ground electrode common to these two electrode terminals are provided on the insulating film. The comb-shaped fixed electrode, the comb-shaped movable electrode, the support portion, and the electrode terminal are formed using, for example, a polysilicon film formed on the insulating film.

  Such a microresonator applies an alternating voltage between the electrode terminal of one of the comb-shaped fixed electrodes and the electrode terminal as a ground electrode, thereby moving the comb-shaped fixed electrode and the comb-shaped movable electrode. An electrostatic attractive force is generated between the electrodes, and the electrostatic attraction force causes the comb-like movable electrode to vibrate by being pushed and pulled planarly in the comb-tooth engagement direction (the comb tooth length direction). This vibration is transmitted to a support portion having a spring property integrated with the comb-shaped movable electrode, and the other comb-shaped movable electrode which is in the meshed state is vibrated planarly.

Resonance determined by the spring constant determined by the structure of the movable electrode and the mass of the movable electrode and the structure of the spring support, generated between the comb-shaped fixed electrode on the input side and the comb-shaped movable electrode A resonance phenomenon occurs when the frequency matches, and the resonance frequency is taken out from the electrode terminal of the other comb-shaped fixed electrode on the output side. The microresonator having such a configuration is used as an oscillator that oscillates an electric signal having a specific frequency or a filter that filters an electric signal having a specific frequency from an electric signal including a plurality of frequencies. For details of the microresonator, see, for example, Patent Documents 1 and 2 below.
US Pat. No. 5,025,346 (column 3, line 37-column 6, line 2, column 6, line 55-column 7, line 52, FIGS. 1-4) US Pat. No. 5,537,083 (column 4, line 43 to column 10, line 33, FIGS. 4 to 8)

  By the way, the resonance frequency of the microresonator described above is determined by the mass of the resonator and the spring constant of the support portion. Therefore, the resonance frequency of the microresonator is almost determined by the designed structure, except for variations due to manufacturing errors. For this reason, in order to obtain microresonators having different resonance frequencies, it is necessary to design microresonators having different structures for each resonance frequency.

  However, if the structure of the micro-resonator is changed for each resonance frequency, there is a problem in that cost increases due to the long time required for design. In addition, if the structure of the microresonator is different, it is necessary to create a mask according to the structure of the microresonator in the photolithography process at the time of manufacture, and it is necessary to establish a process according to the structure. There is a problem that it also causes a rise.

  The present invention has been made in view of the above circumstances, and a microresonator having a desired resonance frequency among a plurality of resonance frequencies, and manufacture of the microresonator capable of manufacturing the microresonator without substantially changing the manufacturing process. It is an object to provide a method and an electronic device including the microresonator.

In order to solve the above problems, a method for manufacturing a microresonator of the present invention includes a silicon substrate, a stacked portion including at least an insulating film formed on the silicon substrate, a movable electrode provided on the stacked portion, and A method of manufacturing a microresonator including a fixed electrode, the step of supporting the movable electrode and forming a support portion provided with a plurality of beams together with the movable electrode and the fixed electrode, and a target resonance A step of fixing at least one of the beams formed on the support member on the laminated portion according to the frequency.
According to this invention, a plurality of beams are provided to form a support member that supports the movable electrode together with the movable electrode and the fixed electrode, and at least one of the plurality of beams is fixed on the stacked portion. Without changing the structure of the movable electrode and the support member at all (without changing their manufacturing process), changing the beam constant fixed on the laminated part and changing the spring constant of the support part, it is determined according to the position of the beam A microresonator having a desired resonance frequency among a plurality of resonance frequencies to be manufactured can be manufactured.
In the method for manufacturing a microresonator of the present invention, the plurality of beams are formed in different areas.
here. The plurality of beams are preferably formed so that the area increases as the distance from the movable electrode increases.
According to these inventions, since the plurality of beams are formed in different areas, it is easy to perform a step of fixing at least one desired beam on the stacked portion from among the plurality of beams provided.
The method for manufacturing a microresonator according to the present invention is characterized in that, when the movable electrode is formed, a large number of holes that penetrate the movable electrode are formed.
According to this invention, the laminated part located under the movable electrode can be etched easily and in a short time.
In the method for manufacturing a microresonator of the present invention, at least one of the beams is separated by separating the movable electrode and the support portion from the stacked portion without separating at least one of the beams from the stacked portion. One is fixed on the laminated portion.
According to the present invention, the support portion is fixed on the stack portion by the beams that are not separated from the stack portion, and the movable electrode and the support portion are supported by the support portion in a state of being separated from the stack portion.
Here, in the method for manufacturing the microresonator of the present invention, it is preferable that the stacked portion positioned below the movable electrode and the support portion is etched to separate the movable electrode and the support portion from the stacked portion. .
The method for manufacturing a microresonator according to the present invention is characterized in that the beam to be separated from the stacked portion and the beam to be fixed on the stacked portion are changed by changing the etching time.
According to the present invention, the beam to be separated from the laminated portion and the beam to be fixed on the laminated portion can be changed only by changing the etching time for separating the movable electrode and the support portion from the laminated portion. The spring constant of the support can be changed with almost no change in the manufacturing process. As a result, a microresonator having a desired resonance frequency among a plurality of resonance frequencies determined according to the position of the beam can be manufactured with almost no change in the manufacturing process.
Here, as the etching time elapses, it is preferable that the beams are separated from the stacked portion in order from a beam close to the movable electrode.
In order to solve the above problems, a microresonator of the present invention includes a silicon substrate, a stacked portion including at least an insulating film formed on the silicon substrate, a movable electrode and a fixed electrode provided on the stacked portion, The at least one microresonator includes a plurality of beams fixed on the stacked portion, and a support portion that supports the movable electrode.
According to this invention, since at least one of the plurality of beams formed on the support portion that supports the movable electrode is fixed on the stacked portion, the resonance frequency corresponding to the fixed position of the beam on the stacked portion is set. The microresonator having is obtained.
Here, it is preferable that the plurality of beams are formed so that an area increases as the distance from the movable electrode increases.
In the microresonator of the present invention, it is preferable that the movable electrode has a large number of holes that penetrate the upper surface and the bottom surface.
In addition, an electronic apparatus according to the present invention includes a microresonator manufactured using any one of the above-described microresonator manufacturing methods, or a microresonator described above.
According to the present invention, since a microresonator having a desired resonance frequency can be formed on a silicon substrate by using a technique for manufacturing a semiconductor element, a filter, an oscillator, and the like using the microresonator are incorporated in a semiconductor chip. It can be integrated. As a result, for example, an ultra-small and ultra-high performance semiconductor element such as a semiconductor element in which a receiving circuit including an oscillator, a filter, an amplifier, a mixer, a detector, and the like is integrated into one chip is provided.

  Hereinafter, a microresonator, a manufacturing method thereof, and an electronic device according to embodiments of the present invention will be described in detail with reference to the drawings.

[Micro Resonator]
FIG. 1 is a plan view showing a microresonator according to an embodiment of the present invention. 2 is a cross-sectional arrow view along the line AA in FIG. 1, and FIG. 3 is a cross-sectional arrow view along the line BB in FIG. The microresonator 10 shown in FIGS. 1 to 3 is configured as a filter having the same function as a transversal SAW (Surface Acoustic Wave) filter. In the following description, if necessary, an XYZ orthogonal coordinate system is set in the drawing, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system in FIGS. 1 to 3 is set so that the X axis and the Y axis are parallel to the surface of the silicon substrate 50, and the Z axis is set to a direction orthogonal to the surface of the silicon substrate 50. Has been.

  A microresonator 10 shown in FIG. 1 includes a transmission-side IDT (Inter Digital Transducer) 20 and a reception-side IDT 30 arranged along the X direction on an insulating film 51 including an oxide film formed on the surface of a silicon substrate 50. In this configuration, the resonator 40 is disposed between them. The transmission-side IDT 20, the reception-side IDT 30, and the resonator 40 are formed using, for example, a polysilicon (p-SiO) film formed on the silicon substrate 50. Alternatively, it is formed using a silicon layer crystallized on an insulating film of an SOI (Silicon On Insulator) substrate.

  The transmission-side IDT 20 includes a fixed electrode 22 having a comb tooth portion 21 and a movable electrode 24 having a comb tooth portion 23. The fixed electrode 22 of the transmission side IDT 20 is connected to the electrode terminal 26 via the lead wire 25. Similarly, the receiving side IDT 30 includes a fixed electrode 32 having a comb tooth portion 31 and a movable electrode 34 having a comb tooth portion 33. The fixed electrode 32 of the receiving side IDT 30 is connected to the electrode terminal 36 via a lead wire 35. Note that reference numeral 38 in FIG. 1 denotes an electrode terminal as a ground electrode that is set in common with respect to the electrode terminals 26 and 36.

  The movable electrode 24 and the movable electrode 34 are connected by a connecting beam 41 extending in the X direction. As shown in FIG. 1, the movable electrode 24, the movable electrode 34, and the connection beam 41 are formed with holes H that penetrate the front surface and the back surface. Although details will be described later, the hole H is a sacrifice located below the movable electrode 24, the movable electrode 34, and the coupling beam 41 in the sacrifice layer 52 (see FIGS. 2 and 3) formed on the insulating film 51. Provided to etch layer 52 within a predetermined time. The sacrificial layer 52 is a layer formed in a manufacturing process when the comb-tooth portions of the comb-shaped fixed electrodes 22 and 32 and the movable electrodes 24 and 34 are formed in a configuration that floats parallel to the substrate surface. .

  The resonator 40 includes a connection beam 41 and movable electrodes 24 and 34. The resonator 40 is configured so that the comb tooth portion 23 of the movable electrode 24 connected to the end portion in the −X direction of the connection beam 41 meshes with the comb tooth portion 21 of the fixed electrode 22 in a plane and + X of the connection beam 41. The comb teeth 33 of the movable electrode 34 connected to the end in the direction are arranged between the fixed electrode 22 and the fixed electrode 32 so as to mesh with the comb teeth 31 of the fixed electrode 32 in a plane.

  The comb teeth 21 of the fixed electrode 22 and the comb teeth 23 of the movable electrode 24 each have a plurality of comb teeth meshing in parallel with the surface of the silicon substrate 50 with a predetermined plane gap (comb gap). ing. Similarly, the comb tooth portion 31 of the fixed electrode 32 and the comb tooth portion 33 of the movable electrode 34 have a plurality of comb teeth meshing in parallel with the surface of the silicon substrate 50 with a gap on a predetermined plane.

  The movable electrodes 24 and 34 are integrally formed with a support portion 42 that supports the movable electrodes 24 and 34. The support portion 42 includes a pair of column portions extending in the Y direction and three beams 42a to 42c extending between the column portions and extending in the X direction, and both ends of the movable electrodes 24 and 34 in the Y direction. It is integrally formed with the part. At least one of the beams 42a to 42c (all of the beams 42a to 42c, the beams 42b and 42c, or only the beam 42c) of the support portion 42 is fixed to the sacrificial layer 52, and the resonator 40 is supported by each support portion 42. Cantilevered.

  By changing the beam fixed to the sacrificial layer 52 among the beams 42 a to 42 c formed on the support portion 42, the length of the column portion from the fixed beam to the resonator 40 is changed. As a result, the spring constant of the support portion 42 is changed, so that the resonance frequency of the resonator 40 can be changed. For example, when the beam 42a is fixed, a resonance frequency of 80 kHz is obtained, when the beam 42b is fixed without fixing the beam 42a, a resonance frequency of 60 kHz is obtained, and when only the beam 42c is fixed without fixing the beams 42a and 42b. A resonance frequency of 40 kHz is obtained. The spring constant of the support portion 42 is expressed as a function of the length of the column portion from the fixed beam to the resonator 40 when the cross-sectional area of the column portion of the support portion 42 is constant. In the microresonator 10 shown in FIG. 1, all of the beams 42a to 42c are fixed to the sacrificial layer 52, and the resonance frequency is 80 kHz.

  The areas of the beams 42a to 42c are different from each other. In the example shown in FIG. 1, the area of the beam 42c is the largest, the area of the beam 42b is the largest, and the area of the beam 42a is the smallest. The reason why the areas of the beams 42 a to 43 c are made different in this way is to control which of the beams 42 a to 42 c of the support portion 42 is fixed to the sacrificial layer 52 in the manufacturing process of the microresonator 10. Further, since the beam 42c formed on the support portion 42 is electrically connected to the electrode terminal 38 serving as a ground electrode, the potential of the resonator 40 becomes substantially the ground potential.

  As shown in FIGS. 2 and 3, the coupling beam 41 is supported in a state of being lifted in parallel to the substrate surface above the surface of the insulating film 51 of the silicon substrate 50 (+ Z direction). Accordingly, the comb-like movable electrodes 24 and 34 connected to both ends of the connection beam 41 are also arranged in a state of floating in parallel to the substrate surface. Further, the comb-shaped fixed electrodes 22 and 32 meshing with the movable electrodes 24 and 34 are also supported in a state where the comb-shaped portions are lifted in parallel to the substrate surface. The flying height of the movable electrodes 24 and 34 and the fixed electrodes 22 and 32, that is, the distance from the insulating film 51 formed on the silicon substrate 50 is about 2 to 3 μm.

  Further, as shown in FIG. 3, the support portion 42 is also lifted in parallel to the substrate surface, like the movable electrodes 24, 34, etc., but the sacrificial layer 52 below the beams 42a to 42c (−Z direction) is formed. The beams 42a to 42c are fixed to the sacrificial layer 52 that is not removed. In FIG. 3, the microresonator 10 in which the resonance frequency of the resonator 40 is set to 80 kHz is illustrated. However, when the resonance frequency of the resonator 40 is set to 60 kHz, the sacrifice below the beam 42a is illustrated. When the layer 52 is removed and the resonance frequency of the resonator 40 is set to 40 kHz, the sacrificial layer 52 below the beam 42a and the beam 42b is removed.

  When the microresonator 10 having the above-described configuration is used as an oscillator, for example, an AC voltage is applied between the electrode terminal 26 of the comb-like fixed electrode 22 and the electrode terminal 38 as a ground electrode. When an alternating voltage is applied between these electrode terminals, an electrostatic attractive force is generated between the comb tooth portion 21 of the fixed electrode 22 and the comb tooth portion 23 of the movable electrode 24. As a result, the movable electrode 24 is pulled and vibrated through the support portion 42 having a spring property in the meshing direction of the comb teeth (the length direction of the comb teeth, that is, the X direction). Incidentally, the vibration node of the resonator 40 in the microresonator 10 whose resonance frequency is set to 80 kHz is the position of the beam 42a. This vibration is transmitted to a support portion 42 having a spring property integrated with the movable electrode 24, and the movable electrode 34 including the comb tooth portion 33 that is in mesh with the comb tooth portion 31 of the fixed electrode 32 is X in the same manner as the other. Vibrate in the direction.

When the vibration generated between the one comb-shaped fixed electrode 22 on the input side and the movable electrode 24 reaches the natural frequency of the resonator 40, the resonator 40 resonates at that frequency. When the resonator 40 resonates, an electric signal having an oscillation frequency corresponding to the natural frequency is output from the electrode terminal 36 connected to the fixed electrode 32 having the other comb tooth portion 31. The oscillation frequency (resonance frequency) is determined by the mass of the resonator 40 including the movable electrodes 24 and 34 and the restoring force against the displacement determined by the spring constant of the support portion 42 (elastic force of the support portion 42). Here, assuming that the mass of the resonator 40 is m and the spring constant of the support portion 42 is k, the oscillation frequency f ₀ of the electric signal output from the fixed electrode 32 is expressed by the following equation (1).
f ₀ = (1 / (2 · π)) · (k / m) ^1/2 (1)

Further, when the microresonator 10 is used as a filter, as shown in FIG. 4, the microresonator 10 is used as a filter having a passband width of a resonance width W centered on the natural frequency f ₀ of the resonator 40. FIG. 4 is a diagram illustrating an example of pass characteristics when the microresonator 10 is used as a filter. When the microresonator 10 is used as a filter, an AC voltage is applied between the electrode terminal 26 of the comb-like fixed electrode 22 and the electrode terminal 38 as a ground electrode.

  If the frequency of the alternating voltage applied between these electrode terminals is a frequency included in the bandwidth W shown in FIG. 4, the resonator 40 vibrates in the X direction by electrostatic force, and an electric signal having the frequency Is output from the electrode terminal 36. On the other hand, when an AC voltage having a frequency not included in the bandwidth W is input, the resonator 30 does not resonate. As a result, that frequency is removed. With this operation, the microresonator 10 is used as a filter.

  In the microresonator 10 according to the embodiment of the present invention described above, the resonator 40 includes the movable electrode 24 having the comb-tooth portion 23 and the movable electrode 34 having the comb-tooth portion 33 so that the movable electrodes 24 and 34 are sandwiched therebetween. The fixed electrode 22 having the comb tooth portion 21 and the fixed electrode 32 having the comb tooth portion 31 are arranged, and the movable electrodes 24 and 34 are supported by the support portion 42. As a form of the resonator of the microresonator 10, a form of a beam (disk) shape or a disk shape can be adopted in addition to such a form.

[Manufacturing Method of Micro Resonator]
5 to 7 are process diagrams showing a method for manufacturing a microresonator according to an embodiment of the present invention. In the present embodiment, the case where the microresonator 10 having a resonance frequency of 80 kHz is manufactured will be described as an example. 5-7, the same code | symbol is attached | subjected to the member same as the member shown in FIGS. 1-3.

First, as shown in FIG. 5A, an oxide film 51a made of silicon dioxide (SiO ₂ ) is formed on a silicon substrate 50. The silicon substrate 50 is polished on both sides and has a thickness of about 500 μm. The oxide film 51a is formed by using a low pressure vapor phase growth (low pressure CVD (Chemical Vapor Deposition)) method, and its thickness is about 0.1 μm.

Next, a nitride film (Si ₃ N ₄ ) 51b having a thickness of about 0.5 μm is formed on the oxide film 51a. This nitride film 51b is also formed by using a low pressure CVD method. The insulating film 51 shown in FIGS. 1 and 2 is formed from the oxide film 51a and the nitride film 51b. When the nitride film 51b is formed, a step of forming a sacrificial layer 52 made of SiO ₂ and having a thickness of about 2 μm is next performed on the nitride film 51b. The laminated part of this invention is comprised by these layers. The microresonator 10 shown in FIG. 2 is also provided with the nitride film 51b, but is not shown in FIG.

  When the above steps are completed, a photoresist (not shown) is applied over the entire upper surface of the sacrificial layer 52, and an exposure process and a development process are performed on the photoresist to form a resist pattern having a predetermined shape. Next, an etching process is performed on the sacrificial layer 52 using the resist pattern as a mask, so that the portions to be the fixed electrodes 22 and 32 and the portions to be the support portions 44 (see FIG. 1), as shown in FIG. The sacrificial layer 52 is removed.

  When the etching process is completed and the resist pattern formed on the sacrificial layer 52 is peeled off, the thickness over the entire surface of the sacrificial layer 52 and the exposed nitride film 51b is increased as shown in FIG. A step of forming a polysilicon (p-SiO) film 60 of about 2.0 μm is performed. When the formation of the polysilicon film 60 is completed, a photoresist (not shown) is applied over the entire upper surface of the polysilicon film 60, and an exposure process and a development process are performed on the photoresist to form a resist pattern having a predetermined shape. Form.

  When the resist pattern is formed, the polysilicon film 60 is etched, and finally the fixed electrodes 22 and 32, the resonator 40 (the coupling beam 41, the movable electrodes 24 and 34, and the support portion 42), and the cantilever beam. 43, the portions to be the electrode terminals 26, 36, and 38 and the lead portions 25 and 35 are left, and the other portions are removed. In this step, a hole H is formed in the movable electrodes 24 and 23 and the connection beam 41. When the etching process is finished and the resist pattern formed on the polysilicon film 60 is removed, the state shown in FIG. When this process is completed, the cross section taken along line BB in FIG. 1 is in the state shown in FIG. 7, and the support portion 42 having the beams 42 a to 42 c is formed on the sacrificial layer 52 together with the connection beam 41. Is done.

  When the above steps are completed, the comb tooth portion 21 of the fixed electrode 22, the comb tooth portion 31 of the fixed electrode 32, the resonator 40 (movable electrodes 24 and 34, the connection beam 41), and the lower portion of the support portion 42 (beams 42 a to 42-). The sacrificial layer 52 is removed by etching. Such etching is possible by controlling the etching time. By performing such etching, as shown in FIGS. 6C and 2, the resonator 40 is formed on the silicon substrate 50 (on the nitride film 51 b) in a state of being levitated with an interval of about 2 to 3 μm. Can do.

  As described above, the case of manufacturing the microresonator 10 having the resonance frequency of 80 kHz has been described as an example. However, the case of manufacturing the microresonator having the resonance frequency of 60 kHz and the case of manufacturing the microresonator having the resonance frequency of 40 kHz. In either case, the same process is performed up to the process of manufacturing the resonator 40 and the like. That is, the same processes as those shown in FIGS. 5A to 6A are performed.

  Manufacture of microresonators having different resonance frequencies is performed by changing the etching time of the sacrificial layer 52 performed after the resonator 40 and the like are formed. That is, when a microresonator having a resonance frequency of 40 kHz is manufactured, an etching time is set so as not to remove the sacrificial layer 52 located below the beams 42a to 42c formed on the support portion 42 as shown in FIG. It had been.

  In the case of manufacturing a microresonator having a resonance frequency of 60 kHz, the sacrificial layer 52 located below the beam 42a is removed, and in the case of manufacturing a microresonator having a resonance frequency of 80 kHz, the beams 42a and 42b. The etching time is set so that the sacrificial layer 52 located below is removed.

  As described above, the beams 42a to 42c have different areas, the beam 42c has the largest area, the beam 42b has the largest area, and the beam 42a has the smallest area. Therefore, as the etching time becomes longer, the sacrificial layer positioned below the beam 42a, the sacrificial layer positioned below the beam 42b, and finally the sacrificial layer positioned below the beam 42c are removed. If the sacrificial layer located below the beam 42c is removed, the resonator 40 and the support portion 42 are removed, so the etching time is set shorter than the time required to remove the sacrificial layer located below the beam 42c. Is done.

  FIG. 8 is a cross-sectional view taken along line BB in FIG. 1, where (a) is a cross-sectional view of a microresonator having a resonance frequency of 60 kHz, and (b) is a microresonator having a resonance frequency of 40 kHz. It is sectional drawing. As shown in FIG. 8A, in the microresonator having a resonance frequency of 60 kHz, the sacrificial layer 52 below the beam 42a is removed from the beams 42a to 42c formed on the support portion 42. For this reason, the support portion 42 of the microresonator whose resonance frequency is set to 60 kHz is fixed to the sacrificial layer 52 at the positions of the beams 42b and 42c, and the vibration node of the resonator 40 is positioned at the position of the beam 42b.

  Further, as shown in FIG. 8B, the sacrificial layer 52 below the beam 42a and the beam 42b is removed from the beams 42a to 42c formed in the support portion 42 of the microresonator having a resonance frequency of 40 kHz. . For this reason, the support part 42 of the microresonator whose resonance frequency is set to 40 kHz is fixed to the sacrificial layer 52 at the position of the beam 42c, and the vibration node of the resonator 40 is located at the position of the beam 42c. Thus, by changing the beam fixed to the sacrificial layer 52, the length of the column portion of the support portion 42 from the mover 40 to the fixed beam changes, and thereby the spring constant of the support portion 42 changes. . For this reason, micro resonators having the same structure and different resonance frequencies can be manufactured by substantially the same manufacturing process.

  In the above embodiment, the insulating film 51 made of the oxide film 51a and the nitride film 51b is formed on the silicon substrate 50, the sacrificial layer 52 is formed on the insulating film 51, and the polysilicon is further formed on the sacrificial layer 52. The film 60 is formed, and the resonator 40 and the fixed electrodes 22 and 32 are formed on the polysilicon film 60. However, these can also be formed using an SOI substrate. When an SOI substrate is used, the resonator 40, the fixed electrodes 22 and 32, etc. are formed using a crystallized silicon layer on the edge film formed on the SOI substrate, and the insulating film is used as the sacrificial layer. By etching in the same manner as in 52, the resonator 40 and the fixed electrodes 22 and 32 can be floated with respect to the silicon substrate.

  In the microresonator 10 according to the embodiment of the present invention described above, the resonator 40 includes the movable electrode 24 having the comb-tooth portion 23 and the movable electrode 34 having the comb-tooth portion 33 so that the movable electrodes 24 and 34 are sandwiched therebetween. The fixed electrode 22 having the comb tooth portion 21 and the fixed electrode 32 having the comb tooth portion 31 are arranged, and the weight 45 is formed on the connection beam 41 that connects the movable electrodes 24 and 34. As a form of the resonator of the microresonator 10, a form of a beam (disk) shape or a disk shape can be adopted in addition to such a form. Even when these forms are adopted, a microresonator having a different resonance frequency is manufactured by integrally forming a support portion having a plurality of beams with respect to the resonator and changing the position where the beams are fixed. be able to.

〔Electronics〕
FIG. 9 is a perspective view showing an appearance of a wristwatch as an electronic apparatus according to an embodiment of the present invention. The wristwatch 100 shown in FIG. 9 includes the microresonator 10 described above as an oscillator. The oscillation frequency of the microresonator 10 is set to about 32 kHz, for example. Currently, wristwatches that are generally provided include a quartz (crystal) oscillator as an oscillator, but the wristwatch 100 can be further reduced in size and weight by using the microresonator 10 as an oscillator.

  FIG. 10 is a perspective view showing an appearance of a mobile phone as an electronic apparatus according to another embodiment of the present invention. A cellular phone 200 shown in FIG. 10 includes an antenna 201, a receiver 202, a transmitter 203, a liquid crystal display unit 204, an operation button unit 205, and the like. The microresonator 10 described above is used as an oscillator for realizing a time measuring function provided in the mobile phone 200.

  In the above-described embodiment, the microresonator 10 whose resonance frequency is set in the range of several tens to hundreds of kHz has been described. However, by changing the structure of the resonator, the microresonator having an oscillation frequency of several hundreds of MHz can do. Also in this microresonator, the transmission frequency of the microresonator can be appropriately set by changing the fixing position of the beam formed on the support column that supports the resonator.

  A microresonator having an oscillation frequency of several hundred MHz is provided in the transmission / reception circuit of the mobile phone 200 shown in FIG. 10, for example. FIG. 11 is a block diagram showing an electrical configuration of an electronic circuit provided in the mobile phone 200 shown in FIG. The electronic circuit shown in FIG. 11 shows the basic configuration of an electronic circuit provided in the mobile phone 200, and includes a transmitter 210, a transmission signal processing circuit 211, a transmission mixer 212, a transmission filter 213, a transmission power amplifier 214, and a transmission / reception amount. It includes a waver 215, antennas 216 a and 216 b, a low noise amplifier 217, a reception filter 218, a reception mixer 219, a reception signal processing circuit 220, a receiver 221, a frequency synthesizer 222, a control circuit 223, and an input / display circuit 224. The In addition, since the cellular phone currently in practical use performs frequency conversion processing a plurality of times, its circuit configuration is more complicated.

  The transmitter 210 is realized by, for example, a microphone that converts sound waves into an electrical signal, and corresponds to the transmitter 203 in FIG. The transmission signal processing circuit 211 is a circuit that performs processing such as D / A conversion processing and modulation processing on the electrical signal output from the transmitter 210. The transmission mixer 212 uses the signal output from the frequency synthesizer 222 to mix the signal output from the transmission signal processing circuit 211. The frequency of the signal supplied to the transmission mixer 212 is about 380 MHz, for example. The transmission filter 213 passes only a signal having a frequency that requires an intermediate frequency (IF) and cuts a signal having an unnecessary frequency. The signal output from the transmission filter 213 is converted into an RF signal by a conversion circuit (not shown). The frequency of this RF signal is, for example, about 1.9 GHz. The transmission power amplifier 214 amplifies the power of the RF signal output from the transmission filter 213 and outputs it to the transmission / reception duplexer 215.

  The transmitter / receiver demultiplexer 215 outputs the RF signal output from the transmission power amplifier 214 to the antennas 216a and 216b and transmits the RF signal from the antennas 216a and 216b in the form of radio waves. The duplexer 215 demultiplexes the received signal received by the antennas 216 a and 216 b and outputs the demultiplexed signal to the low noise amplifier 217. The frequency of the reception signal output from the transmitter / receiver demultiplexer 215 is, for example, about 2.1 GHz. The low noise amplification 117 amplifies the reception signal from the transmission / reception duplexer 215. The signal output from the low noise amplifier 217 is converted into an intermediate signal (IF) by a conversion circuit (not shown).

  The reception filter 218 passes only a signal having a required frequency of an intermediate frequency (IF) converted by a conversion circuit (not shown) and cuts a signal having an unnecessary frequency. The reception mixer 219 uses the signal output from the frequency synthesizer 222 to mix the signal output from the transmission signal processing circuit 211. The intermediate frequency supplied to the reception mixer 219 is about 190 MHz, for example. The reception signal processing circuit 220 is a circuit that performs processing such as A / D conversion processing and demodulation processing on the signal output from the reception mixer 219. The receiver 221 is realized by, for example, a small speaker that converts an electrical signal into a sound wave, and corresponds to the receiver 202 in FIG.

  The frequency synthesizer 222 is a circuit that generates a signal to be supplied to the transmission mixer 212 (for example, a frequency of about 380 MHz) and a signal to be supplied to the reception mixer 219 (for example, a frequency of 190 MHz). The frequency synthesizer 222 includes a PLL circuit that oscillates at an oscillation frequency of 760 MHz, for example, divides a signal output from the PLL circuit to generate a signal having a frequency of 380 MHz, and further divides the frequency to 190 MHz. Generate a signal. The control circuit 223 controls the overall operation of the mobile phone by controlling the transmission signal processing circuit 211, the reception signal processing circuit 220, the frequency synthesizer 222, and the input / display circuit 224. The input / display circuit 224 is for displaying the state of the device to the user of the mobile phone 200 and inputting an instruction from the operator. For example, the liquid crystal display unit 204 and the operation button unit shown in FIG. This corresponds to 205.

  In the electronic circuit having the above-described configuration, the above-described micro-resonator (a micro-resonator whose oscillation frequency is set to about several hundred MHz) is used as the transmission filter 213 and the reception filter 218. The frequencies filtered by the transmission filter 213 and the reception filter 218 (passed frequency band) are transmitted according to the frequency required in the signal output from the transmission mixer 212 and the frequency required by the reception mixer 219. These are set individually for the filter 213 and the reception filter 218.

  Further, the above-described micro-resonator (a micro-resonator whose oscillation frequency is set to about several hundred MHz) is used as a part of the PLL circuit provided in the frequency synthesizer 222. Note that the above-described microresonator is also used in a conversion circuit (not shown) provided between the transmission filter 213 and the transmission power amplifier 214 and between the low noise amplifier 217 and the reception filter 218.

  Since conventional components corresponding to the transmission filter 213, the reception filter 218, the frequency synthesizer 222, and the like could not be integrated with the reception mixer 219 or the like, they are separated from the integrated reception mixer 219 or the like on the substrate. It was mounted on. On the other hand, in the electronic circuit shown in FIG. 11, since a microresonator is used for the transmission filter 213, the reception filter 218, the frequency synthesizer 222, etc., it can be integrated together with the reception mixer 219, etc. Thus, the mobile phone 200 can be reduced in size and weight.

  The microresonator, the manufacturing method thereof, and the electronic device according to the embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. For example, in the above-described embodiment, a mobile phone and a wristwatch have been described as examples of electronic devices. However, the electronic device of the present invention is not limited to a mobile phone and a wristwatch, and includes various electronic devices such as a computer having a timekeeping function, a radio timepiece, a digital camera, and various home appliances.

  Further, not only electronic devices having portability such as mobile phones but also communication devices used in a stationary state such as tuners that receive BS broadcasts and CS broadcasts are included. Furthermore, not only communication devices that use radio waves propagating in the air as communication carriers, but also electronic devices such as HUBs that use high-frequency signals propagating in coaxial cables or optical signals propagating in optical cables. In these electronic devices, a microresonator is used for filtering a predetermined frequency and for realizing a clocking function.

It is a top view which shows the microresonator by one Embodiment of this invention. It is a cross-sectional arrow view along the AA line in FIG. It is a cross-sectional arrow view along the BB line in FIG. It is a figure which shows an example of the passage characteristic in the case of using the microresonator 10 as a filter. It is process drawing which shows the manufacturing method of the microresonator by one Embodiment of this invention. It is process drawing which shows the manufacturing method of the microresonator by one Embodiment of this invention. It is process drawing which shows the manufacturing method of the microresonator by one Embodiment of this invention. It is sectional drawing along the BB line in FIG. 1, (a) is sectional drawing of the microresonator whose resonance frequency is 60 kHz, (b) is sectional drawing of the microresonator whose resonance frequency is 40 kHz. . It is a perspective view which shows the external appearance of the wristwatch as an electronic device by one Embodiment of this invention. It is a perspective view which shows the external appearance of the mobile telephone as an electronic device by other embodiment of this invention. It is a block diagram which shows the electric constitution of the electronic circuit provided in the inside of the mobile telephone 200 shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Micro-resonator 22 ... Fixed electrode 24 ... Movable electrode 32 ... Fixed electrode 34 ... Movable electrode 42 ... Support part 42a-42c ... Beam 50 ... Silicon substrate 51 ... Insulating film (lamination part)
51a …… Oxide film (lamination)
51b ... Nitride film (lamination)
52 …… Sacrificial layer (lamination)
H …… hole

Claims (12)

A method of manufacturing a microresonator comprising a silicon substrate, a stacked portion including at least an insulating film formed on the silicon substrate, and a movable electrode and a fixed electrode provided on the stacked portion,
Supporting the movable electrode and forming a support portion provided with a plurality of beams together with the movable electrode and the fixed electrode;
A step of fixing at least one of the beams formed on the support member on the laminated portion in accordance with a target resonance frequency.   The method of manufacturing a microresonator according to claim 1, wherein the plurality of beams are formed in different areas.   The method of manufacturing a microresonator according to claim 2, wherein the plurality of beams are formed so as to increase in area as they move away from the movable electrode.   The method for manufacturing a microresonator according to any one of claims 1 to 3, wherein when the movable electrode is formed, a large number of holes that penetrate the movable electrode are formed.   At least one of the beams is fixed on the stacked portion by separating the movable electrode and the support portion from the stacked portion without separating at least one of the beams from the stacked portion. The method for producing a microresonator according to any one of claims 1 to 4.   6. The method of manufacturing a microresonator according to claim 5, wherein the stacked portion positioned below the movable electrode and the support portion is etched to separate the movable electrode and the support portion from the stacked portion.   7. The method of manufacturing a microresonator according to claim 6, wherein the beam to be separated from the stacked portion and the beam to be fixed on the stacked portion are changed by changing the etching time.   The method for manufacturing a microresonator according to claim 7, wherein the microresonator is separated from the stacked portion in order from a beam close to the movable electrode as the etching time elapses. A microresonator comprising a silicon substrate, a laminated portion including at least an insulating film formed on the silicon substrate, and a movable electrode and a fixed electrode provided on the laminated portion,
A microresonator comprising at least one of a plurality of beams fixed on the stacked portion and a support portion for supporting the movable electrode.   The microresonator according to claim 9, wherein the plurality of beams are formed so as to increase in area as they move away from the movable electrode.   The micro-resonator according to any one of claims 8 to 10, wherein the movable electrode includes a plurality of holes penetrating the upper surface and the bottom surface thereof. A microresonator manufactured using the method for manufacturing a microresonator according to any one of claims 1 to 8, or the microresonator according to any one of claims 9 to 11. Electronic equipment characterized by

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