JP2005323039A - Micro-resonator and manufacturing method thereof, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a micro-resonator whereby decrease in the strength of a fixed part on a substrate is not incurred, the micro-resonator manufactured by the manufacturing method, and an electronic apparatus provided with the micro-resonator. <P>SOLUTION: The micro-resonator includes: a resonator including a movable electrode 34 configured movable on a silicon substrate 50; a fixed electrode 32 fixed on an insulation film 51 formed on the silicon substrate 50; lead wires 35; and connection terminals 36 or the like. In the case of movably forming the resonator including the movable electrode 34 on the silicon substrate 50, after forming a protection resin 67 around the fixed electrode 32 fixed on the insulation film 51, the lead wires 35, and the connection terminals 36 or the like in advance, the insulation film 51 under the resonator and including the movable electrode 34 is removed by etching. <P>COPYRIGHT: (C)2006,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 above-described comb-shaped fixed electrode, comb-shaped movable electrode, support portion, and electrode terminal are formed on, for example, a polysilicon film formed on the above-described insulating film or an insulating film of an SOI (Silicon On Insulator) substrate. It is formed using a crystallized silicon layer.

  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.
U.S. 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, in the manufacture of the above-described microresonator, a movable part such as a resonator including a movable electrode is formed on the substrate so as to be able to resonate, and fixed parts such as a fixed electrode and an electrode terminal are fixed on the substrate. It is necessary to form in the state. For this reason, first, a movable electrode, a fixed electrode, an electrode terminal, and the like are formed using a polysilicon film formed on the insulating film or a silicon layer crystallized on the insulating film of the SOI substrate, and then fixed. A process of removing only the insulating film below the movable part such as the resonator without removing the insulating film below the fixed part such as the electrode and the electrode terminal and forming only the movable part on the substrate so as to be able to resonate (release) Etching) must be performed.

  In the above-described release etching, it is necessary to start removal from the exposed portion of the insulating film on the substrate using an etchant such as hydrofluoric acid and gradually remove the portion below the movable portion. Since the etching solution is not supplied only to the lower part of the movable part but also to the lower part of the fixed part to remove the insulating film isotropically, it is difficult to remove only the insulating film below the movable part. In addition, the insulating film below the fixed portion is also removed. If the area of the fixed part is sufficiently larger than the area of the movable part formed on the insulating film, since all of the insulating film below the movable part is removed first, the movable part is formed on the substrate so as to be able to resonate. In addition, the fixing portion can be formed in a fixed state on the substrate.

  However, since the size of the microresonator is about 100 μm square and the resistance values of the movable electrode and the fixed electrode are high, the output current from the microresonator is on the order of nA (nano-on-pair) and is extremely small. Further, since the microresonator is required to be as small as possible, the output current tends to become smaller. Furthermore, parasitic capacitance between a structure including a resonator and a fixed electrode including a movable electrode formed on a substrate and a substrate made of a semiconductor contributes to a decrease in the output current of the microresonator. In order to reduce the capacity, the structure on the substrate tends to be formed as small as possible. For this reason, when the release etching is performed, the etching amount of the insulating film below the fixing portion is increased, the strength of the fixing portion is lowered, and the fixing portion is detached from the substrate with a slight impact.

  The present invention has been made in view of the above circumstances, and includes a method for manufacturing a microresonator that does not cause a decrease in strength of a fixed portion on a substrate, a microresonator manufactured by the method, and the microresonator. An object is to provide electronic equipment.

In order to solve the above-described problem, a method for manufacturing a microresonator of the present invention includes a silicon substrate, a sacrificial layer formed on the silicon substrate, a fixing portion provided on the sacrificial layer, and the silicon substrate. A movable portion provided on the sacrificial layer, the first step of forming the fixed portion and the movable portion on the sacrificial layer, and at least on the sacrificial layer around the fixed portion A second step of forming a protective resin in part, and a third step of removing the sacrificial layer below the movable portion while protecting the sacrificial layer below the fixed portion with the protective resin. Yes.
According to this invention, after forming the fixed portion and the movable portion on the sacrificial layer, the protective resin is formed on at least a part of the sacrificial layer around the fixed portion, and the sacrificial layer below the fixed portion is protected with the protective resin. However, the sacrificial layer below the movable part is removed, and when the sacrificial layer below the movable part is removed, the sacrificial layer below the fixed part is not removed or there is little undercut of the sacrificial layer, so the strength of the fixed part is reduced. There is no invitation. In addition, since the undercut below the fixed portion is small, the fixed portion can be reduced in size, and the performance of the microresonator can be prevented from being deteriorated due to parasitic capacitance.
In the method for manufacturing a microresonator of the present invention, the first step includes a conductive layer forming step of forming a conductive layer on a sacrificial layer formed on the silicon substrate, and etching the conductive layer into a predetermined shape. And a structure forming step for forming the fixed portion and the movable portion.
According to the present invention, since the conductive layer is formed on the sacrificial layer of the silicon substrate and the conductive layer is etched into a predetermined shape to form the fixed portion and the movable portion, it can be efficiently performed without complicating the manufacturing process. A fixed part and a movable part can be formed on the sacrificial layer.
Further, in the method for manufacturing a microresonator of the present invention, the structure forming step is a step of forming the movable portion in a circular shape, a beam shape, or a shape having a comb-tooth shape in part. Yes.
According to the present invention, the shape of the resonator can be formed in a circular shape, a beam shape, or a shape having a comb-tooth shape in part instead of a predetermined fixed shape, so that the frequency band to pass through Accordingly, the shape of the resonator can be set. For example, if the shape of the resonator is set to a shape having a comb-teeth shape, a passing characteristic that allows an electrical signal having a frequency of several tens of KHz to pass is obtained, and if the shape is set to a beam shape, the frequency is set to several MHz to several tens of MHz. A pass characteristic that allows an electric signal to pass through is obtained, and a pass characteristic that allows an electric signal having a frequency of several hundreds of MHz to be passed when set in a circular shape.
In the method for manufacturing a microresonator according to the present invention, the fixed portion includes a fixed electrode and a connection terminal connected to the fixed electrode, and the movable portion moves relative to the fixed electrode. It is desirable to include a movable electrode configured to be capable.
In the method for manufacturing a microresonator of the present invention, the second step includes a step of applying a protective resin to the entire surface of the sacrificial layer including the fixed portion and the movable portion, and the applied protective resin is predetermined. And forming the protective resin on at least a part of the sacrificial layer around the fixed portion by etching back the protective resin formed in a predetermined shape. .
According to the present invention, the protective resin is applied to the entire surface of the sacrificial layer including the fixed portion and the movable portion, and after the formed protective resin is formed into a predetermined shape, the protective resin is etched back to sacrifice the sacrificial layer around the fixed portion. Since the protective resin is formed on at least a part of the upper portion, the protective resin can be efficiently formed at an arbitrary position around the fixed portion.
In the method for manufacturing a microresonator of the present invention, the sacrificial layer is silicon oxide, and the third step uses the hydrofluoric acid or buffered hydrofluoric acid to form the sacrificial layer below the movable part. It is desirable that it is a process to remove.
The method for manufacturing a microresonator of the present invention includes a step of removing the protective resin by heat treatment after removing the sacrificial layer below the movable part.
According to the present invention, since the protective resin formed around the fixed portion is removed by removing the sacrificial layer below the movable portion, the protective resin enters, for example, between the movable portion and the substrate. Therefore, it is possible to prevent defects such as hindering the operation of the movable part.
The microresonator of the present invention is characterized by being manufactured using any of the microresonator manufacturing methods described above.
According to the present invention, since the microresonator is manufactured by using the above manufacturing method, an inexpensive microresonator having high strength with respect to the substrate, high yield and high reliability can be obtained.
An electronic apparatus according to the present invention includes the microresonator described above.
According to the present invention, since a microresonator having a desired resonance frequency can be formed on a silicon substrate 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.

  FIG. 1 is a plan view showing a microresonator according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG. The microresonator 10 shown in FIGS. 1 and 2 is configured as a filter that functions in the same manner 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 and 2 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 in a direction orthogonal to the surface of the silicon substrate 50. Has been.

  The microresonator 10 shown in FIG. 1 has a configuration in which a transmission side IDT (Inter Digital Transducer) 20 and a reception side IDT 30 are arranged along the X direction on a silicon substrate 50, and a resonator 40 is arranged therebetween. is there. The transmission side IDT 20, the reception side IDT 30, and the resonator 40 are formed using, for example, a silicon layer (active 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. The resonator 40 includes the connection beam 41, the movable electrodes 24 and 34, and a beam portion 42 formed of a rectangular frame described later. 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. Since the movable electrode 24 having the comb-tooth portion 23 and the movable electrode 34 having the comb-tooth portion 33 are provided on the resonator 40, vibrations in the longitudinal direction of the comb-tooth portions 23, 33, or twist or rotation of the resonator 40. This is suitable for widening the setting range of the resonance frequency. Of course, with such a configuration, a single resonance frequency can be obtained.

  The frame-shaped beam portion 42 formed integrally with the movable electrodes 24 and 34 is supported by a cantilever beam 43 coupled to the beam portion 42, and the support portion 44 of the cantilever beam 43 is a silicon substrate. The structure is fixed on 50. Since the support portion 44 is electrically connected to the electrode terminal 38 as a ground electrode, the potential of the resonator 40 is almost equal to the ground potential. The outer shape of the beam portion 42 is not particularly limited to a square shape, and can be set to an arbitrary shape such as a circular shape, an oval shape, or a spindle shape.

  As shown in FIG. 2, the coupling beam 41 is supported in a state of being lifted in parallel to the substrate surface above the surface 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 surface of the silicon substrate 50 is about 2 to 3 μm. The resonator 40 including the movable electrodes 24 and 34, the fixed electrodes 22 and 32, the lead wires 25 and 35, and the electrode terminals 26 and 36 are insulated as sacrificial layers formed on the SOI substrate 60 (see FIG. 4). The film 51 and the silicon layer (active layer) 52 are used.

  The fixed electrodes 22 and 32, the lead wires 25 and 35, the electrode terminals 26 and 36, and the support portion 44 described above are fixed portions that are fixed on the silicon substrate 50. On the other hand, the resonator 40 including the connection beam 41, the movable electrodes 24 and 34, and the beam portion 42, and the cantilever beam 43 are movable portions configured to be movable on the silicon substrate 50.

  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 beam portion 42 having spring properties in the meshing direction of the comb teeth (the length direction of the comb teeth, that is, the X direction). This vibration is transmitted to a beam portion 42 having a spring property integrated with the movable electrode 24, and the movable electrode 34 having the comb tooth portion 33 in mesh with the comb tooth portion 31 of the fixed electrode 32 is X similarly. 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 beam portion 42 (elastic force of the beam portion 42).

Here, when the mass of the resonator 40 is m and the spring constant of the beam 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)
When the microresonator 10 shown in FIGS. 1 and 2 is used as an oscillator, for example, 16 kHz, 32 kHz, 72 kHz or the like is set as a design target value of the oscillation frequency.

In the case of using the micro-resonator 10 as a filter, as shown in FIG. 3, it is used as a filter having a pass band width of the resonance width W centered on the natural frequency f ₀ of the resonator 40. FIG. 3 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 AC voltage applied between these electrode terminals is a frequency included in the bandwidth W shown in FIG. 3, the resonator 40 vibrates in the X direction by electrostatic force, and an electric signal having that 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 weight 45 is formed on the connection beam 41 that connects the movable electrodes 24 and 34. As the form of the resonator of the microresonator 10, a form of a beam (beam) shape or a disk shape can be adopted in addition to such a form.

[Manufacturing Method of Micro Resonator]
4 to 6 are process diagrams showing a method for manufacturing a microresonator according to an embodiment of the present invention. 4 to 6, the same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals. Further, in the following description, the case where the microresonator 10 is manufactured using the SOI substrate 60 will be described as an example. However, by forming an insulating film and a polysilicon (p-Si) film on the silicon substrate 50, the following description will be given. The microresonator 10 can be manufactured through substantially the same process as when the SOI substrate 60 is used.

In this embodiment, as shown in FIG. 4A, an insulating film 51 made of silicon dioxide (SiO ₂ ) as a sacrificial layer and a low pressure vapor deposition (low pressure CVD (Chemical Vapor Deposition)) method are used on a silicon substrate 50. An SOI substrate 60 in which a silicon layer 52 as a conductive layer formed in this order is sequentially formed is used. The silicon substrate 50 is polished on both sides and has a thickness of about 500 μm. The insulating film 51 is formed with a thickness of about 0.1 μm, and the silicon layer 52 is formed with a thickness of about 10-20 μm. When the microresonator 10 is manufactured, a process for manufacturing an SOI substrate may be provided as one of the manufacturing processes, or a commercially available SOI substrate may be used without the process for manufacturing the SOI substrate.

  First, a photoresist (not shown) is applied over the entire upper surface of the silicon layer 52 formed on the SOI substrate 60 shown in FIG. 4A, and an exposure process and a development process are performed on the photoresist. A resist pattern having a predetermined shape is formed. The resist pattern formed by this process includes the resonator 40 including the movable electrodes 24 and 34 and the beam portion 42, the cantilever 43, the support portion 44, the fixed electrodes 22 and 32, the lead wires 25, 35 and 38, and the connection. Openings are formed at positions other than the positions where the structures such as the terminals 26 and 36 should be formed.

  Next, the silicon layer 52 of the SOI substrate 60 is etched using this resist pattern as a mask, and the fixed electrodes 22 and 32, the resonator 40 (the coupled beam 41, the movable electrodes 24 and 34, and the beam are formed on the insulating film 51. Part 42), cantilever 43, support part 44, electrode terminals 26, 36, 38 and lead wires 25, 35 are formed. Etching methods used to form these structures include RIE (Reactive Ion Etching), ICP (Inductively Coupled Plasma) etching, or D-RIE (Deep Reactive Ion Etching). There is a law. When this step is finished, all the structures are fixed on the insulating film 51 as shown in FIG.

  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 connecting beam 41, and the beam portion 42), and the cantilever are then performed. A step of removing the insulating film 51 below the beam 43 by etching (release etching step) is performed. However, in this embodiment, when the insulating film 51 below these structures is removed, below the fixed electrode 22 excluding the comb tooth portion 21, below the fixed electrode 32 excluding the comb tooth portion 31, the lead A protective resin is formed in advance so that the insulating film 51 below the lines 25 and 35, below the electrode terminals 26 and 36, and below the support portion 44 is not removed. For this reason, a process of forming a protective resin is performed before the insulating film 51 is etched.

  FIG. 5A is an enlarged view of the movable electrode 34, the fixed electrode 32, the lead wire 35, and the electrode terminal 36 formed on the insulating film 51 shown in FIG. 4B. In forming the protective resin, first, as shown in FIG. 5B, a photoresist 65 is applied over the entire surface of the insulating film 51 including each structure on the insulating film 51. Next, an exposure process and a development process are performed on the photoresist 65 to make the photoresist 65 into a resist pattern 66 having a predetermined shape. In the example shown in FIG. 5C, a resist pattern 66 is formed on the insulating film 51 on the side of the fixed electrode 32 toward the movable electrode 34 (−X direction) and on the right side of the electrode terminal 36 (+ X direction). .

  Note that the resist pattern 66 is desirably formed along the entire periphery of the fixed portion in the XY plane. That is, the resist pattern 66 is formed around the fixed electrodes 22 and 32 excluding the comb-tooth portions 23 and 33, around the lead wires 25 and 35, around the electrode terminals 26 and 36, and around the support portion 44. desirable. In this embodiment, the case where the resist pattern 66 is formed along the entire periphery of the fixed portion will be described as an example. However, it is not always necessary to form the resist pattern along the entire fixed portion. The resist pattern 66 may be formed only at a location (where the etching of the insulating film 51 is to be prevented).

  When the formation of the resist pattern 66 is completed, the resist pattern 66 formed on the insulating film 51 is etched back by, for example, a dry process using RIE or the like, a wet process, or ashing using oxygen plasma. When this process is performed, only the resist pattern 66 at the end portion where the insulating film 51 and the fixing portion are joined remains, and the protective resin 67 is formed. In the example shown in FIG. 6A, the protective resin 67 is formed on the left side (−X direction) of the fixed electrode 32 (excluding the comb tooth portion 31) and on the right side (+ X direction) of the connection electrode 36. When the resist pattern 66 is formed around the fixed electrodes 22 and 32 excluding the comb teeth portions 23 and 33, around the lead wires 25 and 35, around the electrode terminals 26 and 36, and around the support portion 44, A protective resin 67 is formed around these.

When the formation of the protective resin 67 is completed, the comb tooth portion 21 and the fixed electrode 32 of the fixed electrode 22 using hydrofluoric acid or a BHF (buffered hydrofluoric acid) solution (HF: NH ₄ F = 1: 6). The step of removing the comb-teeth portion 31, the resonator 40 (movable electrodes 24 and 34, the connecting beam 41 and the beam portion 42), and the insulating film 51 below the cantilever beam 43 by etching is performed. At this time, since the protective resin 67 is formed on the insulating film 51 around the fixed portion such as the fixed electrodes 22 and 32 excluding the comb-tooth portions 21 and 31, the insulating film 51 around the fixed portion is hardly etched. As a result, the insulating film 51 below the fixed portion is also difficult to be etched. On the other hand, since the protective resin 67 is not formed around the movable portion such as the movable electrode 34, the insulating film 51 around the movable portion is easily etched, and as a result, the insulating film below the movable portion is also easily formed. Etched.

  Therefore, as shown in FIG. 6B, in this etching process, the insulating film 51 below the movable electrode 34 is etched, but below the fixed electrode 32 (except under the comb tooth portion 31), the lead wire 35 The insulating film 51 below and below the electrode terminal 36 is hardly etched and undercut is extremely small. When the above steps are completed, for example, ashing using oxygen plasma is performed, and the protective resin 67 formed around the fixed portion is removed. If the protective resin 67 swells and peels off at the final stage of the etching process on the insulating film 51 below the movable part, the ashing process using oxygen plasma can be omitted. However, since the peeled protective resin 67 may enter between the resonator 40 and the silicon substrate 50 and cause a defect such as preventing the operation of the resonator 40, the ashing process is performed to remove the protective resin 67. It is desirable to do.

  When the above steps are completed, as shown in FIGS. 6C and 4, the resonator 40 in a state of floating on the silicon substrate 50 with an interval of about 2 to 3 μm can be formed. Further, the fixed electrodes 22 and 32 excluding the comb-tooth portions 21 and 31, the lead wires 25 and 35, the electrode terminals 26 and 36, and substantially the entire lower surface of the support portion 44 are bonded to the insulating film 51. Can do.

  According to the microresonator manufacturing method of the present embodiment described above, the fixed electrodes 22 and 32, the lead wires 25 and 35, the electrode terminals 26 and 36, the support portion 44, and the like are fixed on the insulating film 51 as a sacrificial layer. The protective resin is formed on at least a part of the insulating film 51 around the fixed portion after the movable portion such as the resonator 40 and the resonator 40 is formed, and the sacrificial layer below the fixed portion is protected with the protective resin and below the movable portion. The sacrificial layer is removed, and when the sacrificial layer below the movable part is removed, the sacrificial layer below the fixed part is not removed or there is little undercut of the sacrificial layer, so that the strength of the fixed part is not reduced. In addition, since the undercut below the fixed portion is small, the fixed portion can be reduced in size, and the performance of the microresonator can be prevented from being deteriorated due to parasitic capacitance.

  Further, the formation of the fixed portion and the movable portion on the silicon substrate 50 is performed by etching the silicon film 52 as a conductive layer formed on the insulating film 51 into a predetermined shape, which complicates the manufacturing process. The fixed portion and the movable portion can be formed on the sacrificial layer efficiently. In addition, the shape of the resonator can be formed in a circular shape, a beam shape, or a shape having a comb-tooth shape in part instead of a predetermined shape, so that the resonator can be formed according to the frequency band to be passed. Can be set. For example, if the shape of the resonator is set to a shape having a comb-teeth shape, a passing characteristic that allows an electrical signal having a frequency of several tens of KHz to pass is obtained, and if the shape is set to a beam shape, the frequency is set to several MHz to several tens of MHz. A pass characteristic that allows an electric signal to pass through is obtained, and a pass characteristic that allows an electric signal having a frequency of several hundreds of MHz to be passed when set in a circular shape. The manufacturing method described above can be similarly applied to the case of manufacturing a microresonator having a beam-shaped or disk-shaped resonator.

  In the above embodiment, the resonator 40, the fixed electrodes 22 and 32, and the like are formed using the SOI substrate 60 in which the insulating film 51 and the silicon layer 52 are formed on the silicon substrate 50. However, it is also possible to use a substrate in which an insulating film made of an oxide film and a nitride film is formed on a silicon substrate, a sacrificial layer is formed on the insulating film, and a polysilicon film is further formed on the sacrificial layer. Moreover, although the case where the microresonator 10 was manufactured was mentioned as an example in the said embodiment, this invention is the structure which should be manufactured using a MEMS technique, and the needle | mover and board | substrate which were comprised so that movement was possible on a board | substrate In the case of forming a stator fixed on top, it can be applied in general.

〔Electronics〕
FIG. 7 is a perspective view showing an appearance of a mobile phone as an electronic apparatus according to an embodiment of the present invention. A cellular phone 100 illustrated in FIG. 7 includes an antenna 101, a receiver 102, a transmitter 103, a liquid crystal display unit 104, an operation button unit 105, and the like. FIG. 8 is a block diagram showing an electrical configuration of an electronic circuit provided in the mobile phone 100 shown in FIG.

  The electronic circuit shown in FIG. 8 shows a basic configuration of an electronic circuit provided in the mobile phone 100, and includes a transmitter 110, a transmission signal processing circuit 111, a transmission mixer 112, a transmission filter 113, a transmission power amplifier 114, and a transmission / reception amount. It includes a wave filter 115, antennas 116a and 116b, a low noise amplifier 117, a reception filter 118, a reception mixer 119, a reception signal processing circuit 120, a receiver 121, a frequency synthesizer 122, a control circuit 123, and an input / display circuit 124. 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 110 is realized by, for example, a microphone that converts a sound wave into an electric signal, and corresponds to the transmitter 103 in FIG. The transmission signal processing circuit 111 is a circuit that performs processing such as D / A conversion processing and modulation processing on the electrical signal output from the transmitter 110. The transmission mixer 112 uses the signal output from the frequency synthesizer 122 to mix the signal output from the transmission signal processing circuit 111. The frequency of the signal supplied to the transmission mixer 112 is, for example, about 380 MHz. The transmission filter 113 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 113 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. Transmission power amplifier 114 amplifies the power of the RF signal output from transmission filter 113 and outputs the amplified signal to transmission / reception demultiplexer 115.

  The transmitter / receiver demultiplexer 115 outputs the RF signal output from the transmission power amplifier 114 to the antennas 116a and 116b, and transmits the RF signal from the antennas 116a and 116b in the form of radio waves. Further, the transmitter / receiver demultiplexer 115 demultiplexes the received signals received by the antennas 116 a and 116 b and outputs the demultiplexed signals to the low noise amplifier 117. The frequency of the reception signal output from the transmission / reception duplexer 115 is, for example, about 2.1 GHz. The low noise amplification 117 amplifies the reception signal from the transmission / reception duplexer 115. The signal output from the low noise amplifier 117 is converted into an intermediate signal (IF) by a conversion circuit (not shown).

  The reception filter 118 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 119 mixes the signal output from the transmission signal processing circuit 111 using the signal output from the frequency synthesizer 122. The intermediate frequency supplied to the reception mixer 119 is about 190 MHz, for example. The reception signal processing circuit 120 is a circuit that performs processing such as A / D conversion processing and demodulation processing on the signal output from the reception mixer 119. The receiver 121 is realized by, for example, a small speaker that converts an electrical signal into a sound wave, and corresponds to the receiver 102 in FIG.

  The frequency synthesizer 122 is a circuit that generates a signal to be supplied to the transmission mixer 112 (for example, a frequency of about 380 MHz) and a signal to be supplied to the reception mixer 119 (for example, a frequency of 190 MHz). The frequency synthesizer 122 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 123 controls the overall operation of the mobile phone by controlling the transmission signal processing circuit 111, the reception signal processing circuit 120, the frequency synthesizer 122, and the input / display circuit 124. The input / display circuit 124 is for displaying the state of the device to the user of the mobile phone 100 and inputting an instruction from the operator. For example, the liquid crystal display unit 104 and the operation button unit shown in FIG. This corresponds to 105.

  In the electronic circuit having the above configuration, the above-described microresonator is used as the transmission filter 113 and the reception filter 118. The frequencies filtered by the transmission filter 113 and the reception filter 118 (frequency bands to be passed) are transmitted according to the required frequency in the signal output from the transmission mixer 112 and the frequency required by the reception mixer 119. These are set individually for the filter 113 and the reception filter 118.

  Further, the above-described microresonator is used as a part of the PLL circuit provided in the frequency synthesizer 122. Since the PLL circuit provided in the frequency synthesizer 122 is a circuit that oscillates at a specific frequency as described above, the microresonator provided as a part of the PLL circuit resonates in a single resonance mode, and the above specific The Q value is set to be higher at the frequency of. Note that the above-described microresonator is also used in a conversion circuit (not shown) provided between the transmission filter 113 and the transmission power amplifier 114 and between the low noise amplifier 117 and the reception filter 118.

  Since conventional components corresponding to the transmission filter 113, the reception filter 118, the frequency synthesizer 122, and the like cannot be integrated with the reception mixer 119, etc., they are separated from the integrated reception mixer 119, etc. on the substrate. It was mounted on. On the other hand, in the electronic circuit shown in FIG. 8, since the microresonator is used for the transmission filter 113, the reception filter 118, the frequency synthesizer 122, etc., it can be integrated together with the reception mixer 119, etc. Thus, the mobile phone 100 can be reduced in size and weight.

  FIG. 9 is a perspective view showing an appearance of a wristwatch as an electronic apparatus according to another embodiment of the present invention. A wristwatch 200 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. However, by using the microresonator 10 as an oscillator, the wristwatch 200 can be further 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 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 a perspective view which shows the external appearance of the mobile telephone as an electronic device by one 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 100 shown in FIG. It is a perspective view which shows the external appearance of the wristwatch as an electronic device by other embodiment of this invention.

Explanation of symbols

10 …… Microresonator 22 …… Fixed electrode (fixed part)
24 …… Moving electrode (moving part)
25 …… Lead wire (fixed part)
26 …… Connection terminal (fixed part)
32 …… Fixed electrode (fixed part)
34 …… Moving electrode (moving part)
35 …… Lead wire (fixed part)
36 …… Connection terminal (fixed part)
40 …… Resonator (movable part)
41 …… Linked beam (movable part)
42 …… Beam part (movable part)
43 …… Cantilever (movable part)
44 …… Supporting part (fixing part)
50 …… Silicon substrate 51 …… Insulating film (sacrificial layer)
52 …… Silicon layer (conductive layer)
65 …… Photoresist (protective resin)
67 …… Protective resin

Claims (9)

A method for manufacturing a microresonator, comprising: a silicon substrate; a sacrificial layer formed on the silicon substrate; a fixed portion provided on the sacrificial layer; and a movable portion provided on the silicon substrate. ,
A first step of forming the fixed portion and the movable portion on the sacrificial layer;
A second step of forming a protective resin on at least a portion of the sacrificial layer around the fixed portion;
And a third step of removing the sacrificial layer below the movable portion while protecting the sacrificial layer below the fixed portion with the protective resin. The first step includes a conductive layer forming step of forming a conductive layer on a sacrificial layer formed on the silicon substrate;
The method of manufacturing a microresonator according to claim 1, further comprising: a structure forming step of etching the conductive layer into a predetermined shape to form the fixed portion and the movable portion.   3. The method of manufacturing a microresonator according to claim 2, wherein the structure forming step is a step of forming the movable portion into a circular shape, a beam shape, or a shape having a comb tooth shape in part. The fixed portion includes a fixed electrode and a connection terminal connected to the fixed electrode,
The method of manufacturing a microresonator according to any one of claims 1 to 3, wherein the movable part includes a movable electrode configured to be movable relative to the fixed electrode. The second step is a step of applying a protective resin to the entire surface of the sacrificial layer including the fixed portion and the movable portion;
Forming the applied protective resin into a predetermined shape;
5. The method includes: etching back the protective resin formed in a predetermined shape to form the protective resin on at least a part of the sacrificial layer around the fixed portion. The manufacturing method of the microresonator as described in any one of these. The sacrificial layer is silicon oxide;
The said 3rd process is a process of removing the said sacrificial layer under the said movable part using hydrofluoric acid or a buffered hydrofluoric acid, The any one of Claims 1-5 characterized by the above-mentioned. A method for producing a microresonator as described in 1. above.   The method for manufacturing a microresonator according to any one of claims 1 to 6, further comprising a step of removing the protective resin by heat treatment after removing the sacrificial layer below the movable portion. .   A microresonator manufactured using the method for manufacturing a microresonator according to any one of claims 1 to 7. An electronic apparatus comprising the microresonator according to claim 8.

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