JP2005159620A - Micro-resonator, manufacturing method thereof and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro-resonator having a desired resonant frequency, a method of manufacturing the micro-resonator by which the micro-resonator can be manufactured with high yield, and an electronic apparatus equipped with the 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-shaped tooth 23 is engaged with the comb tooth part 21 of the fixed electrode 22, and a movable electrode 34 disposed so that a comb tooth part 33 is engaged with the comb tooth part 31 of the fixed electrode 32, and a weight 45 is formed on a coupling beam 41 for coupling these movable electrodes 24, 34. The weight 45 is provided to adjust at least any one of the resonant frequency and the resonant mode of the resonator 40. <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 movable electrode (strictly speaking, the mass of the movable electrode and the support portion) and the spring constant of the support portion. The above-described movable electrodes and support portions are formed on the substrate using a photolithography technique widely used in the manufacture of semiconductor elements and the like, but a plurality of movable electrodes and support portions are formed as designed values. It is difficult, and the mass and spring constant of the manufactured movable electrode and supporting part often vary. For this reason, the resonance frequency of the manufactured microresonator also varies, and there is a problem that it is difficult to manufacture a plurality of microresonators having the same resonance frequency.

  Also, in the manufacture of microresonators, there are cases where a plurality of microresonators having a single resonance frequency are manufactured, or microresonators having the same structure but different resonance frequencies within the same resonance frequency band are manufactured. In some cases. In the case of manufacturing the latter microresonator, if there are variations in the manufacturing of the microresonator, it is likely that a product having a desired resonance frequency is obtained, but the yield greatly depends on the manufacturing conditions. There was a problem.

  The present invention has been made in view of the above circumstances, a microresonator having a desired resonance frequency, a method of manufacturing a microresonator capable of manufacturing the microresonator with a high yield, and an electronic apparatus including the microresonator. The purpose is to provide.

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, and a resonator provided on the stacked portion. A method of manufacturing a microresonator comprising: a weight forming step of forming a weight on the top of the resonator; and an adjusting step of adjusting the weight of the weight.
According to the present invention, since the weight is formed on the top of the resonator and the weight of the resonator is adjusted by adjusting the weight of the weight, there is a manufacturing error of the resonator or the like. However, the weight of the resonator can be adjusted. As a result, a microresonator having a desired resonance frequency can be manufactured at a high yield and at a low cost. In addition, since a microresonator having a desired resonance frequency can be manufactured by adjusting the weight of the weight, microresonators having different resonance frequencies can be easily manufactured at a high yield even with the same structure. be able to.
In the method for manufacturing a microresonator of the present invention, the weight forming step includes a step of forming a conductive layer that forms the resonator on the stacked portion, and a step of forming the resonator of the conductive layer. The method includes a step of forming the weight on an upper portion and a step of patterning the conductive layer into a predetermined shape to form the resonator on the substrate.
According to the present invention, the conductive layer for forming the resonator is formed on the laminated portion, the weight is formed on the conductive layer and the portion where the resonator is to be formed, and then the conductive layer is formed in a predetermined shape. Since the resonator is formed on the substrate by patterning, the weight can be formed on the resonator without hindering the vibration of the resonator configured to vibrate on the substrate. In addition, since a plurality of weights can be formed at a time, the weights can be formed on the plurality of resonators without causing a decrease in throughput.
In the method of manufacturing a microresonator according to the present invention, the weight forming step is a step of forming a plurality of weights on the resonator.
According to the present invention, since a plurality of weights are formed on the top of the resonator, the microresonator is appropriately set by appropriately setting the shape of the weight, the arrangement of the weights on the resonator, and the number of weights on the resonator. The resonance frequency and resonance mode can be arbitrarily set.
Further, in the method for manufacturing a microresonator of the present invention, the adjusting step is a step of adjusting the weight of the weight by selectively transpiration of the weight by irradiating the weight with a laser. It is a feature.
According to the present invention, the weight formed on the resonator is irradiated with a laser to selectively evaporate the weight, so that the weight can be adjusted in a short time with high accuracy. As a result, a microresonator having a desired resonance frequency can be manufactured without causing a decrease in throughput.
In the method for manufacturing a microresonator of the present invention, the adjusting step is a step of adjusting the weight of the weight while measuring the resonance frequency of the resonator while vibrating the resonator. .
According to the present invention, since the weight of the weight is adjusted while measuring the resonance frequency of the resonator while vibrating the resonator, the resonance frequency of the microresonator can be reliably adjusted to a desired resonance frequency. Therefore, a microresonator having a desired resonance frequency can be manufactured with a high yield.
Further, in the method for manufacturing a microresonator of the present invention, the adjustment step includes a step of removing a predetermined weight among the plurality of weights formed on the resonator according to a target resonance frequency of the resonator. It is characterized by being.
According to the present invention, a plurality of weights having a predetermined weight corresponding to the target resonance frequency are formed, and a predetermined weight among the plurality of weights formed according to the target resonance frequency is removed. Therefore, the frequency of the microresonator can be set to a desired frequency in a short time. In addition, when manufacturing a microresonator having a different resonance frequency, it is only necessary to remove the weight corresponding to the resonance frequency, so that a microresonator having a desired resonance frequency can be manufactured in a short time without changing the production line. can do.
Further, the microresonator manufacturing method of the present invention is characterized in that the predetermined weight is removed by irradiating the weight with a laser to evaporate the predetermined weight.
According to the present invention, since the weight is removed by laser irradiation as in the case of adjusting the weight of the weight, a microresonator having a desired resonance frequency is manufactured in a short time without changing the manufacturing line. be able to.
In the method for manufacturing a microresonator of the present invention, the adjustment step is a step of adjusting the resonance frequency of the resonator without changing the resonance mode of the resonator by adjusting the weight of the weight. It is characterized by that.
Alternatively, the adjusting step is a step of adjusting a resonance frequency of the resonator while changing a resonance mode of the resonator by adjusting a weight of the weight.
According to these inventions, the resonance frequency can be adjusted without changing the resonance mode, or the resonance frequency can be changed while changing the resonance frequency, so that the setting range of the resonance frequency of the microresonator is widened. be able to. Moreover, a microresonator having a high Q value can be obtained, or a microresonator having a low Q value can be obtained.
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, and a resonator provided on the stacked portion. A microresonator is characterized in that a weight for adjusting the weight of the resonator is provided above the resonator.
According to the present invention, since the weight for adjusting the weight of the resonator is provided above the resonator, the weight of the resonator can be made constant even if the weight of the resonator itself varies. As a result, a constant resonance frequency can be obtained. Even if there is a factor causing a change in the resonance frequency other than the variation in the weight of the resonator, a constant resonance frequency can be obtained by changing the weight of the resonator by adjusting the weight of the weight.
Here, the weight is preferably formed of any one of gold (Au), platinum (Pt), copper (Cu), and aluminum (Al).
Since these metals are also used for forming wirings of semiconductor elements, a manufacturing process has been established and sufficient adhesion to the resonator can be obtained. In particular, if the weight is formed using gold (Au) or platinum (Pt), the resonator or the like can be formed without changing the formation process of the resonator or the like.
In the microresonator of the present invention, the weight is formed in a desired shape and in a desired position on the resonator in a desired shape.
According to the present invention, by appropriately changing the shape of the weight, the position of the weight on the resonator, and the number of weights on the resonator, the setting range of the resonance frequency of the microresonator can be widened, and the high Q It can be a microresonator having a value or a microresonator having a low Q value.
In the microresonator of the present invention, the resonator has two pairs of comb-like electrodes provided on the stacked portion.
According to the present invention, it is possible to obtain a resonance mode such as vibration in the longitudinal direction of the comb teeth, or torsion of the resonator or vibration due to the rotation of the resonator, which is suitable for widening the setting range of the resonance frequency of the micro resonator It is. Of course, with such a configuration, a single resonance frequency can be obtained. However, the present invention is not intended to limit the resonator to a shape having a comb-like electrode. In addition to the shape having a comb-like electrode, the beam (beam) shape or disk A shape can also be adopted.
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, 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.

  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 as a conductive layer 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. 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 in the resonator 40, the longitudinal vibration of the comb-tooth portions 23, 33, or the 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 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. In FIG. 2, electrode terminals 26 and 36 formed of polysilicon or the like and a layer 52 between the lead portions 25 and 35 and the insulating film 51 include comb-like fixed electrodes 22 and 32 and a movable electrode 24, 34 is a sacrificial layer provided in the manufacturing process when the comb-tooth portion with 34 is formed so as to float parallel to the substrate surface.

  As shown in FIGS. 1 and 2, the microresonator 10 of the present embodiment includes a plurality of weights 45 on a connection beam 41 that forms part of the resonator 40. These weights 45 are for adjusting at least one of the resonance frequency and the resonance mode of the resonator 40. In the example shown in FIGS. 1 and 2, the longitudinal direction of the connection beam 41 ( Four are provided along the (X direction).

  The resonance frequency of the resonator 40 changes due to variations in the weight of the resonator 40 itself or variations in the spring constant of the beam portion 42 that forms a part of the resonator 40. The weight 45 is used to adjust the change in the resonance frequency of the resonator 40 regardless of the cause of the change in the resonance frequency. Further, for example, the resonance mode can be adjusted by making the arrangement of the weight 45 with respect to the center of gravity of the resonator 40 symmetric or asymmetric.

  The weight 45 is made of metal such as gold (Au), platinum (Pt), copper (Cu), and aluminum (Al). These metals are also used for forming wirings of semiconductor elements and the like, and are easy to form because the manufacturing process has been established. In addition, sufficient adhesion to the resonator can be obtained. In addition, the shape of the weight 45, the position on the connection beam 41, and the number can be set to a desired shape and a desired position according to the resonance frequency and resonance mode of the target resonator 40, and its weight. Can be adjusted according to at least one of the resonance frequency and resonance mode of the target resonator 40. By performing such adjustment, the setting range of the resonance frequency of the resonator 40 can be widened, and the resonator 40 can have a high Q value or a low Q value. .

  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 alternating 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 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 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 types are employed, the resonance frequency of the resonator can be adjusted by forming a weight on the resonator and adjusting the weight of the weight.

[Manufacturing Method of Micro Resonator]
4 and 5 are process diagrams showing a method for manufacturing a microresonator according to an embodiment of the present invention. 4 and 5, the same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals. First, as shown in FIG. 4A, 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, by performing an etching process on the sacrificial layer 52 using this resist pattern as a mask, as shown in FIG. 4B, the portions to be the fixed electrodes 22 and 32 and the portions to be the support portions 44 (FIG. 1). 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 as a conductive layer of about 2.0 μm is performed. When the formation of the polysilicon film 60 is completed, a process of forming a metal film 61 over the entire surface of the polysilicon film 60 is performed as shown in FIG. Here, the metal film 61 is formed of any one of gold (Au), platinum (Pt), copper (Cu), and aluminum (Al), and is formed using, for example, a vapor deposition method or a sputtering method. The thickness of the metal film 61 is appropriately set according to the weight of the weight 45 shown in FIGS.

  Next, a photoresist (not shown) is applied over the entire upper surface of the metal film 61, and an exposure process and a development process are performed on the photoresist to form a resist pattern having a predetermined shape. Next, by etching the metal film 61 using this resist pattern as a mask, as shown in FIG. 5A, the portion to be the coupling beam 41 of the resonator 40 (if necessary, the movable electrode 24). , 34), the weight 45 is formed on the upper part. It is preferable that the weight 45 is designed and formed to be slightly heavier than the weight capable of obtaining a target resonance frequency in consideration of variations in the weight of the resonator 45.

  When the formation of the weight 45 is completed, the photoresist used for the formation of the weight 45 is peeled off, and then a photoresist (not shown) is applied again on the polysilicon film 60, and the photoresist is exposed and developed. To form a resist pattern having a predetermined shape. 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 beam 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. When the etching process is finished and the resist pattern formed on the polysilicon film 60 is removed, the state 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 coupling beam 41, and the beam portion 42), and the cantilever 43 The sacrificial layer 52 below is removed by etching. Such etching is possible by controlling the etching time. By performing such etching, as shown in FIG. 5C, the resonator 40 can be formed on the silicon substrate 50 (on the nitride film 51b) in a state of being levitated with an interval of about 2 to 3 μm.

  As described above, in the present embodiment, the polysilicon film 60 as the conductive layer is formed, and the portion to be the coupling beam 41 of the resonator 40 (the portion to be the movable electrodes 24 and 34 if necessary). After the weight 45 is formed on the upper part of the silicon substrate 60, the polysilicon film 60 is patterned into a predetermined shape and the sacrificial layer 52 is etched to form the resonator 40. By forming the resonator 40 by such a method, the weight 45 can be formed on the resonator 40 without hindering the vibration of the resonator 40.

  Further, since a plurality of weights 45 can be formed at a time, even when the weights 45 are formed on the plurality of resonators 40, the weights 45 can be formed without causing a decrease in throughput. On the other hand, even when a plurality of weights 45 are formed on the resonator 40, a plurality of weights 45 can be formed at a time. Further, the shape of the weight 45, the arrangement of the weight 45 on the resonator 40, and the number of the weights 45 on the resonator 40 can be set as appropriate. For this reason, the resonance frequency and resonance mode of the resonator 40 can be arbitrarily set.

  In the above description, the metal film 61 is formed over the entire surface of the polysilicon film 60 and the weight 45 is formed by etching. However, the formation of the weight 45 is not limited to this formation method. . For example, when metal is deposited on the polysilicon film 60 by vapor deposition or sputtering, a weight 45 is formed by vapor-depositing metal on a portion to be the coupling beam 41 of the resonator 40 using a mask. Also good. When such a forming method is used, after the resonator 40 is formed, that is, after the polysilicon film 60 is patterned and the sacrificial layer 52 below the portion to be the resonator 40 is etched, A weight 45 can also be formed on the substrate.

  When the formation of the resonator 40 having the weight 45 on the upper portion is completed, the step of adjusting the weight of the weight 45 is performed next. FIG. 6 is a diagram illustrating a process of adjusting the weight of the weight 45. As shown in FIG. 6, the weight of the weight 45 is adjusted by irradiating the weight 45 with laser light emitted from the laser 70 and selectively evaporating the weight 45. The adjustment amount of the weight of the weight 45 changes according to the variation in the weight of the formed resonator 40 and the spring constant of the cantilever 43. For this reason, in this embodiment, the weight of the weight 45 is adjusted while measuring the resonance frequency of the resonator 40 while vibrating the resonator 40.

  In order to measure the resonance frequency of the resonator 40 while vibrating the resonator 40, a measuring device including an amplifier 71, a sensor head 72, a laser Doppler vibrometer 73, and a frequency analyzer 74 is used as shown in FIG. The amplifier 71 amplifies an AC signal having a predetermined frequency (resonant frequency of the resonator 40 or a frequency in the vicinity thereof) output from the signal output terminal (signal) of the frequency analyzer 74 with a predetermined amplification factor, and supplies it to the electrode terminal 36. Give.

  The sensor head 72 includes a light source such as a He—Ne laser, and irradiates the comb tooth portion 23 of the movable electrode 24 provided on the resonator 40 with laser light emitted from the light source, and reflects the reflected light. It receives the interference light obtained by interfering with the reference light and outputs a light reception signal obtained by photoelectric conversion. The intensity of the laser light emitted from the sensor head 72 is set to be much lower than the intensity of the laser light emitted from the laser 70, and the weight of the movable electrode 24 changes due to the irradiation of the laser light. Does not have any effect.

  The laser Doppler vibrometer 73 outputs a detection signal obtained by detecting the vibration frequency / vibration speed of the resonator 40 by frequency-modulating the light reception signal output from the sensor head 72. The frequency analyzer 74 outputs an AC signal having a variable frequency, a detection signal output from the laser Doppler vibrometer 73 and input to the input terminal (ch1), and an output output from the signal output terminal (signal). The resonance frequency of the resonator 40 is obtained using the AC signal input to the end (ch2), and the result is visually displayed on a display device 75 such as a CRT (Cathod Ray Tube) or a liquid crystal display device.

  In the above configuration, the weight of the weight 45 on the resonator 40 is adjusted, for example, according to the following procedure. First, the resonance frequency of the resonator 40 is measured without irradiating the weight 45 with the laser light from the laser 70. For this measurement, an electric signal having a predetermined frequency is output from the signal output terminal (signal) of the frequency analyzer 74 and amplified by the amplifier 71 and then applied to the electrode terminal 36. Further, laser light is irradiated from the sensor head 72 to the comb teeth portion 23 of the movable electrode 24 provided on the resonator 40.

  If the frequency of the electrical signal applied to the electrode terminal 36 is a frequency away from the resonance frequency of the resonator 40, the amplitude of the resonator 40 is small, and therefore vibration of the detection signal output from the laser Doppler vibrometer 73. The value of the signal indicating the speed is small. On the other hand, if the frequency of the electric signal applied to the electrode terminal 36 approaches the resonance frequency of the resonator 40, the amplitude of the resonator 40 increases, and therefore the vibration speed of the detection signal output from the laser Doppler vibrometer 73. The value of the signal indicating becomes larger.

  Such measurement is performed while changing the frequency of the electrical signal output from the signal output terminal of the frequency analyzer 74. Thereby, the resonance frequency of the resonator 40 in a state where the weight of the weight 45 is not adjusted is measured. As described above, since the weight 45 is formed slightly heavier than the weight at which the target resonance frequency is obtained, the resonance frequency obtained by the above measurement is lower than the target resonance frequency.

  Next, in a state where an electrical signal from the signal output terminal of the frequency analyzer 74 is applied to the electrode terminal 36, the weight 45 is irradiated with laser light emitted from the laser 70, and the weight 45 is selectively evaporated. At this time, the laser light from the sensor head 72 is irradiated to the comb teeth portion 23 of the movable electrode 24 provided on the resonator 40 to constantly measure the resonance frequency of the resonator 40. Note that it takes time to measure the resonance frequency of the resonator 40 because it is necessary to change the frequency of the electrical signal from the frequency analyzer 74. For this reason, it is desirable to stop the irradiation of the laser 70 until the measurement is completed. Of course, if the evaporation of the weight 45 is small, the resonance frequency can be measured while irradiating the laser 70.

  In this way, the operation of measuring the resonance frequency of the resonator 40 while irradiating the weight 45 with the laser light from the laser 70 and selectively evaporating the weight 45 is repeated, and the resonance frequency of the resonator 40 to be measured is the target. When the resonance frequency becomes high, the laser light irradiation from the laser 70 is stopped. As a result, the microresonator 10 including the resonator 40 having the target resonance frequency is obtained.

  When adjusting the weight of the weight 45, each weight 45 may be irradiated with laser light to adjust the weight of each weight 45, or only a specific weight 45 may be irradiated with laser light to Only the weight may be adjusted. In particular, when the resonance frequency is changed in a state where the resonance mode of only the vibration in the longitudinal direction of the comb teeth portions 23 and 33 is generated, the weight 45 is arranged symmetrically with respect to the center of gravity of the resonator 40, and It is desirable to adjust the weight of the weight 45 symmetrically.

  On the other hand, when it is desired to obtain a resonance mode by twisting or rotation of the resonator 40, the weight 45 is formed asymmetrically with respect to the center of gravity of the resonator 40, or the weight of only a specific weight 45 of the plurality of weights 45 is formed. Adjust the height. Since the resonance frequency changes when the resonance mode changes, the resonance frequency of the resonator 45 can be increased or decreased. As described above, in this embodiment, the resonance frequency can be adjusted without changing the resonance mode, or the resonance frequency can be changed while changing the resonance frequency. Therefore, the resonance frequency of the microresonator 10 can be set. The range can be widened. Moreover, a microresonator having a high Q value can be obtained, or a microresonator having a low Q value can be obtained.

  As described above, when the microresonator 10 is used as an oscillator, a predetermined frequency such as 16 kHz, 32 kHz, 72 kHz, or the like is used as a design target value of the oscillation frequency. For this reason, the weight 45 for obtaining each oscillation frequency is obtained at the design stage, the weight 45 is formed on the resonator 40, and the specific weight 45 is removed from the resonator 45 to obtain a specific weight. It is preferable to obtain an oscillation frequency close to the oscillation frequency.

  By doing so, the microresonator 10 having the same structure but different oscillation frequencies can be manufactured in a short time. Here, if the weight 45 is removed by laser light irradiation, the weight 45 can be removed without changing the production line at all. Further, by irradiating the remaining weight 45 with this laser light, the weight of the weight 45 can be finely adjusted, and the oscillation frequency of the resonator 45 can be set to a target oscillation frequency.

  According to the method of manufacturing the microresonator of the present embodiment described above, the weight 45 is formed on the top of the resonator 40, and the weight of the weight 40 is adjusted to adjust the weight of the resonator 40. Therefore, the weight of the resonator 40 can be adjusted even when there is a variation in weight due to a manufacturing error of the resonator 40 or the like. As a result, the microresonator 10 having the target resonance frequency can be manufactured at a high yield and at a low cost.

  The weight 45 is adjusted by irradiating the weight 45 formed on the resonator 40 with a laser to selectively evaporate the weight 45. As a result, the microresonator 10 having the target resonance frequency can be manufactured without causing a decrease in throughput. Furthermore, since the weight of the weight 45 is adjusted while measuring the resonance frequency of the resonator 40 while vibrating the resonator 40, the resonance frequency of the microresonator can be reliably adjusted to the target resonance frequency. . Thereby, the microresonator 10 having the target resonance frequency can be manufactured with a high yield. The manufacturing method described above can be similarly applied to manufacturing a microresonator having a beam-shaped or disk-shaped resonator.

  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 and the fixed electrodes 22 and 32 are formed using a crystallized silicon layer on the insulating 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 types are employed, the resonance frequency of the resonator can be adjusted by forming a weight on the resonator and adjusting the weight of the weight.

  Further, in the above embodiment, the sensor head 72, the laser Doppler vibrometer 73, and the frequency analyzer 74 are used to measure the resonance frequency of the resonator 40. In order to measure the resonance frequency of the resonator 40 with high accuracy, it is desirable to perform measurement using these. However, the method for measuring the resonance frequency of the resonator 40 is not limited to this. For example, the change in the capacitance between the fixed electrode 22 and the movable electrode 24 caused by the vibration of the resonator 40 or the change in the capacitance between the fixed electrode 32 and the movable electrode 34 is detected. The resonance frequency can also be measured.

〔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 sound waves into an electrical 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 the 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 a figure which shows the mode of the process of adjusting the weight of the weight. 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 24 …… Moving electrode (comb-like electrode)
34 …… Moveable electrode (comb-like electrode)
40 …… Resonator 45 …… Weight 50 …… Silicon substrate 51 …… Insulating film (laminated part)
51a …… Oxide film (lamination)
51b ... Nitride film (lamination)
52 …… Sacrificial layer (lamination)
60 …… Polysilicon film (conductive layer)

Claims (14)

A method of manufacturing a microresonator comprising a silicon substrate, a laminated portion including at least an insulating film formed on the silicon substrate, and a resonator provided on the laminated portion,
A weight forming step of forming a weight on top of the resonator;
An adjustment step of adjusting the weight of the weight. A method for manufacturing a microresonator. The weight forming step includes forming a conductive layer that forms the resonator on the stacked portion;
Forming the weight above the portion of the conductive layer where the resonator is to be formed;
The method for manufacturing a microresonator according to claim 1, further comprising: patterning the conductive layer into a predetermined shape to form the resonator on the substrate.   3. The method of manufacturing a microresonator according to claim 1, wherein the weight forming step is a step of forming a plurality of weights on the resonator.   The adjusting step is a step of adjusting a weight of the weight by irradiating the weight with a laser and selectively evaporating the weight. A method for producing a microresonator according to claim 1.   The adjusting step is a step of adjusting the weight of the weight while measuring the resonance frequency of the resonator while vibrating the resonator. A method for producing a microresonator as described in 1. above.   4. The adjusting step according to claim 3, wherein the adjusting step is a step of removing a predetermined weight among the plurality of weights formed on the resonator in accordance with a target resonance frequency of the resonator. Manufacturing method of a microresonator.   7. The method of manufacturing a microresonator according to claim 6, wherein the removal of the predetermined weight is performed by irradiating the weight with a laser to evaporate the predetermined weight.   The adjusting step is a step of adjusting a resonance frequency of the resonator without changing a resonance mode of the resonator by adjusting a weight of the weight. The manufacturing method of the microresonator as described in any one of these.   8. The adjusting step according to claim 1, wherein the adjusting step is a step of adjusting a resonance frequency of the resonator while changing a resonance mode of the resonator by adjusting a weight of the weight. The manufacturing method of the microresonator as described in any one. A microresonator comprising a silicon substrate, a stacked portion including at least an insulating film formed on the silicon substrate, and a resonator provided on the stacked portion,
A microresonator comprising a weight for adjusting a weight of the resonator at an upper portion of the resonator.   11. The microresonator according to claim 10, wherein the weight is formed of any one of gold (Au), platinum (Pt), copper (Cu), and aluminum (Al).   The microresonator according to claim 10 or 11, wherein the weight is formed in a desired shape and a desired number on the resonator in a desired shape.   The microresonator according to any one of claims 10 to 12, wherein the resonator has two pairs of comb-like electrodes provided on the stacked portion. A microresonator manufactured using the method for manufacturing a microresonator according to any one of claims 1 to 9, or the microresonator according to any one of claims 10 to 13. Electronic equipment characterized by

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