WO2012114655A1 - Mems共振器 - Google Patents
Mems共振器 Download PDFInfo
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- WO2012114655A1 WO2012114655A1 PCT/JP2012/000616 JP2012000616W WO2012114655A1 WO 2012114655 A1 WO2012114655 A1 WO 2012114655A1 JP 2012000616 W JP2012000616 W JP 2012000616W WO 2012114655 A1 WO2012114655 A1 WO 2012114655A1
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- intermediate layer
- mems resonator
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- vibrator
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/24—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive
- H03H9/2405—Constructional features of resonators of material which is not piezoelectric, electrostrictive, or magnetostrictive of microelectro-mechanical resonators
- H03H9/2447—Beam resonators
- H03H9/2463—Clamped-clamped beam resonators
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
- H03H9/02259—Driving or detection means
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
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- H03H2009/02488—Vibration modes
- H03H2009/02496—Horizontal, i.e. parallel to the substrate plane
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- H—ELECTRICITY
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- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02244—Details of microelectro-mechanical resonators
- H03H9/02338—Suspension means
Definitions
- the present invention relates to a resonator used as a timing device in an electronic device or the like, and more particularly to a MEMS (Micro-Electro Mechanical Systems) resonator.
- MEMS Micro-Electro Mechanical Systems
- FIG. 16 is a perspective view showing a conventional MEMS resonator 100 formed using an SOI (Silicon On On Insulator) substrate.
- SOI Silicon On On Insulator
- the uppermost Si layer of the SOI is etched to form a beam-type vibrator 101, an input electrode 102, and an output electrode 103.
- a part of a BOX (Buried Oxide) layer is etched to form a vibrator 101 with both ends supported, and the vibrator 101 is in a state where it can vibrate.
- the support portion 104, the input electrode 102, and the output electrode 103 at both ends of the vibrator 101 are tethered to the silicon substrate 105 through the buried oxide film 110 by the remaining BOX layer.
- FIG. 17 is a diagram schematically showing a cross section taken along line AA of the conventional MEMS resonator shown in FIG.
- the conventional MEMS resonator 100 has a configuration in which electrodes 102 and 103 are arranged on both side surfaces of the vibrator 101 via a gap. One electrode is the input electrode 102 and the other electrode is the output electrode 103.
- a configuration in which a direct current potential difference is applied between the input electrode 102 and the vibrator 101 and a direct current potential difference is also applied between the output electrode 103 and the vibrator 101 applies the direct current voltage Vp to the vibrator 101 as a specific example. Is realized.
- the MEMS resonator 100 when an AC voltage is applied to the input electrode 102, an excitation force derived from an electrostatic force is applied to the vibrator 101 due to a potential difference between the input electrode 102 and the vibrator 101.
- the frequency of the AC voltage applied to the input electrode 102 matches the mechanical resonance frequency of the vibrator 101, the vibrator 101 vibrates greatly, and a displacement current associated with the vibration is output from the output electrode 103. This is the operating principle of the MEMS resonator 100.
- the vibrator 101 shown in FIG. 16 has a doubly-supported beam shape in which both ends are fixed and the center portion is held in a hollow state.
- an electrostatic force is applied to the vibrator 101, the beam undergoes flexural vibration.
- the resulting flexural vibration mode is excited.
- Non-Patent Document 1 As a manufacturing method of the MEMS resonator using the SOI as described above, for example, there is a general method shown in “Non-Patent Document 1” described later. Further, “Patent Document 1” to be described later shows a vibrator having a disk shape. As a resonance mode excited by the vibrator, in addition to the flexural vibration mode, for example, there is a torsional vibration mode described in “Patent Document 2” described later even when the vibrator has a beam shape.
- the size of the vibrator is generally a micrometer or less and is fine.
- the minimum mass detection capability is proportional to the -2.5 power of the resonance frequency. Therefore, a vibrator having a high mechanical resonance frequency is preferable for detecting a small amount of mass. That is, the size of the vibrator is preferably a micrometer or less, and a fine one is suitable.
- Non-Patent Document 1 As a method of manufacturing a resonator using such a fine vibrator, a semiconductor such as the resonator shown in the above-mentioned “Non-Patent Document 1,” “Patent Document 1,” and “Patent Document 2” is used. It is a common method to form on a silicon substrate using a process. Therefore, a semiconductor material is used as a material for the vibrator and the electrode (including silicide).
- FIG. 17 schematically shows the operation of the conventional MEMS resonator.
- the structure shown in the cross-sectional views of FIGS. 18 and 19 is obtained.
- 18 schematically shows a cross section taken along the line AA of the MEMS resonator 100 shown in FIG. 16
- FIG. 19 schematically shows a cross section taken along the line BB of the MEMS resonator 100 shown in FIG. Show.
- the cross section taken along the line AA of the MEMS resonator 100 shown in FIG. 16 refers to a cross section obtained by cutting the MEMS resonator 100 shown in FIG. 16 along a vertical plane including the AA line.
- the vibrator 101, the input electrode 102, and the output electrode 103 are all n-type semiconductors.
- Metal layers 106, 107, and 108 are formed on the input electrode 102, the output electrode 103, and the support portion 104, respectively.
- An AC voltage Vi (AC) is input to the input electrode 102, and an AC current Io (AC) is output from the output electrode 103.
- a bias DC voltage Vp is applied to the vibrator 101 via the support portion 104.
- the junction between the metal layer and the n-type semiconductor in addition to the junction between the metal layer and the n-type semiconductor (metal-n junction) shown in FIGS. 18 and 19, the junction between the metal layer and the p-type semiconductor (metal-p junction). , Pn junction, pnp junction, and npn junction may exist. A barrier serving as a barrier is also formed at these bonding interfaces.
- FIG. 20 is a graph showing an example of the VI characteristic at the junction interface between the metal layer and the p-type semiconductor.
- the horizontal axis represents the potential difference (V) on both sides of the bonding interface, and the vertical axis represents the direct current (I) penetrating the bonding interface.
- the direct current between the input electrode 102 and the output electrode 103 is caused by the capacitor (Ci) between the vibrator 101 and the input electrode 102 and the capacitor (Co) between the vibrator 101 and the output electrode 103. Is blocked. For the same reason, a direct current from the direct current power source Vp does not flow through the support portion 104 in the vibrator 101.
- FIG. 21 is a circuit diagram showing an equivalent circuit of the ideal MEMS resonator of FIG.
- the capacitance Ci and the capacitance Co are assumed to be equivalent values, and C is set in the equivalent circuit of FIG. m is the mass of the vibrator 101, k is the spring force of the vibrator 101, and Qm is the Q value related to mechanical vibration.
- the elements in the broken line represent a mechanical spring-mass-damper resonance system.
- Vp is a bias DC voltage applied to the vibrator 101.
- ⁇ is an electro-mechanical conversion coefficient, and is a value obtained by multiplying the change ⁇ C / ⁇ x of the vibrator 101 and the interelectrode capacitance C accompanying the unit shift amount ⁇ x of the vibrator 101 by the bias DC voltage Vp.
- Zb is the internal impedance of the power supply for the bias DC voltage Vp.
- FIG. 22 shows an equivalent circuit in the case where a resistance ri exists on the input side, a resistance ro on the output side, and a resistance rb on the bias DC voltage supply path to the vibrator 101 due to the barrier existing in the actual device in the MEMS resonator.
- Qe which is the Q value as the entire electric element does not become the Q value (Qm) related to the original mechanical vibration because there is an electrical resistance loss due to the barrier, and Qe is smaller than Qm.
- Qm the Q value related to the original mechanical vibration because there is an electrical resistance loss due to the barrier
- Qe is smaller than Qm.
- a resonator having a high Q factor improves the minimum detection performance, for example, as a mass detector, and enables low phase noise as an oscillator. For this reason, in order to realize a high-performance device using various resonators, it is necessary to suppress degradation of the Q value due to resistance loss to the minimum.
- the present invention has been made in view of the above circumstances, and provides a MEMS resonator in which deterioration of Q value due to unnecessary resistance is reduced in order to maximize the Q value related to mechanical vibration of the MEMS resonator.
- the purpose is to do.
- the present inventor has conducted various experiments, and as a result, when a junction interface (barrier) such as a pn junction exists in the input / output system of the alternating current of the vibrator and the electrode in the MEMS resonator, It was found that the resistance loss applied to the alternating current can be reduced by flowing the direct current together with the alternating current.
- a junction interface such as a pn junction
- the MEMS resonator includes: A vibrator that mechanically vibrates when an electrostatic force is applied; A support portion for supporting the vibrator so as to vibrate; And at least one electrode having a surface facing the vibrator through a gap, One of the support or the electrode is an input electrode, and the other one of the support or the electrode is an output electrode, The vibrator is excited by an electrostatic force generated by an AC signal applied via an input terminal connected to the input electrode, and an electric current generated by vibration of the vibrator is output to an output terminal connected to the output electrode.
- a MEMS resonator that outputs via The current path between the input terminal and the input electrode or the current path between the output electrode and the output terminal includes a pn junction, a pp junction, an nn junction, a metal-n junction, and a metal-p junction. At least one of the bonding interfaces is formed, A DC bias circuit is provided for constantly supplying a DC current to the junction interface.
- the MEMS resonator according to the first aspect of the present invention configured as described above has a high Q value comparable to the mechanical Q value by suppressing electrical resistance loss unnecessarily associated with the MEMS resonator. Can be realized.
- a MEMS resonator includes a vibrator that mechanically vibrates when an electrostatic force is applied; A support portion for supporting the vibrator so as to vibrate; And at least two electrodes having a surface facing the vibrator via a gap, One of the at least two electrodes is an input electrode and the other one of the at least two electrodes is an output electrode; The vibrator is excited by an electrostatic force generated by an AC signal applied via an input terminal connected to the input electrode, and an electric current generated by vibration of the vibrator is output to an output terminal connected to the output electrode.
- a MEMS resonator that outputs via A bias terminal is connected to the support portion formed integrally with the vibrator, and a current path between the bias terminal and the support portion includes a pn junction, a pp junction, an nn junction, and a metal- a junction interface of at least one of an n junction and a metal-p junction is formed;
- a DC bias circuit is provided for constantly supplying a DC current to the junction interface.
- a MEMS resonator includes, in the first aspect, a first intermediate layer disposed on a surface of the input electrode, The bonding interface is formed between the input electrode and the first intermediate layer; The input terminal is connected to the input electrode through the first intermediate layer;
- the DC bias circuit includes: A first impedance element having one end connected to one of a DC power supply or a common electrode and the other end connected to the first intermediate layer; A second impedance element having one end connected to a region other than the region where the first intermediate layer is formed on the surface of the input electrode, and the other end connected to the other of the DC power supply or the common electrode; Including The first impedance element includes an inductor or a resistor; The second impedance element has an inductor or a resistor; One of the first impedance element and the second impedance element may have a resistance.
- the MEMS resonator according to the third aspect of the present invention configured as described above allows a DC current to flow simultaneously with an AC current when a junction interface (barrier) exists in the input / output system of the AC current of the input electrode. Thus, it is possible to reduce the resistance loss applied to the alternating current.
- a MEMS resonator according to a fourth aspect of the present invention is the second intermediate layer according to the third aspect, which is disposed on the surface of the input electrode and is spaced apart from the first intermediate layer. Have The second impedance element may be connected to the input electrode through the second intermediate layer.
- the MEMS resonator according to the fourth aspect of the present invention configured as described above can reduce the resistance loss applied to the AC current by simultaneously flowing the DC current together with the AC current.
- a MEMS resonator includes, in the first aspect, a first intermediate layer disposed on the surface of the output electrode, The bonding interface is formed between the output electrode and the first intermediate layer; The output terminal is connected to the output electrode via the first intermediate layer;
- the DC bias circuit includes: A first impedance element having one end connected to one of a DC power supply or a common electrode and the other end connected to the first intermediate layer; A second impedance element having one end connected to a region other than the region where the first intermediate layer is formed on the surface of the output electrode, and the other end connected to the other of the DC power supply or the common electrode; Including The first impedance element includes an inductor or a resistor; The second impedance element has an inductor or a resistor; One of the first impedance element and the second impedance element may have a resistance.
- the MEMS resonator according to the fifth aspect of the present invention configured as described above allows a direct current to flow simultaneously with an alternating current when a junction interface (barrier) exists in the alternating current input / output system of the output electrode. Thus, it is possible to reduce the resistance loss applied to the alternating current.
- a MEMS resonator according to a sixth aspect of the present invention is the second intermediate layer according to the fifth aspect, wherein the second intermediate layer is disposed on the surface of the output electrode and spaced apart from the first intermediate layer.
- Have The second impedance element may be connected to the output electrode through the second intermediate layer.
- the MEMS resonator according to the sixth aspect of the present invention configured as described above can simultaneously reduce the resistance loss applied to the AC current by causing the DC current to flow simultaneously with the AC current.
- a MEMS resonator includes the first intermediate layer disposed on the surface of the support portion in the second aspect, The bonding interface is formed between the support portion and the first intermediate layer, The bias terminal is connected to the support portion via the first intermediate layer by a first wiring,
- the DC bias circuit includes: A region other than the region where the first intermediate layer is formed on the surface of the support portion, and a second wiring that connects the common electrode, It is good also as a structure which has a resistance element in the middle of either one of the said 1st wiring or the said 2nd wiring.
- the MEMS resonator according to the seventh aspect of the present invention configured as described above allows a direct current to flow simultaneously with an alternating current when a junction interface (barrier) exists in the alternating current input / output system of the support portion. Thus, it is possible to reduce the resistance loss applied to the alternating current.
- the support part in the second aspect includes a first support part and a second support part that support both ends of the vibrator, A first intermediate layer disposed on a surface of the first support portion;
- the bonding interface is formed between the first support portion and the first intermediate layer;
- the bias terminal is connected to the first support portion via the first intermediate layer by a first wiring;
- the DC bias circuit is It is good also as a structure provided with the 2nd wiring which connects a said 2nd support part and a common electrode.
- the MEMS resonator according to the eighth aspect of the present invention configured as described above allows a direct current to flow simultaneously with an alternating current when a junction interface (barrier) exists in the alternating current input / output system of the support portion. Thus, it is possible to reduce the resistance loss applied to the alternating current.
- a MEMS resonator according to a ninth aspect of the present invention is arranged on the surface of the second support portion in the seventh or eighth aspect, and is connected to the first intermediate layer via the vibrator. Having a second intermediate layer spaced apart, The second wiring may be configured to connect the second support portion and the common electrode via the second intermediate layer.
- the impedance element is also used by the vibrator. It is possible to reduce the resistance loss applied to the alternating current with a small number of components.
- the MEMS resonator according to a tenth aspect of the present invention is the alternating current in which the impedance of the first impedance element or the second impedance element is input to the input terminal in the third to sixth aspects.
- the signal current is set to a value that does not flow to the DC power supply or the common electrode.
- the MEMS resonator according to the tenth aspect of the present invention configured as described above can allow a direct current to flow simultaneously with an alternating current.
- the MEMS resonator according to the eleventh aspect of the present invention may be configured such that, in the third or fifth aspect, the first intermediate layer includes a metal layer.
- the MEMS resonator according to the twelfth aspect of the present invention may have a configuration in which the second intermediate layer includes a metal layer in the fourth or sixth aspect.
- the MEMS resonator according to the thirteenth aspect of the present invention may be configured such that, in the third or fifth aspect, the first intermediate layer is formed by laminating a mediation layer and a metal layer.
- a MEMS resonator according to a fourteenth aspect of the present invention may be configured such that, in the fourth or sixth aspect, the first intermediate layer is formed by laminating an intermediate layer and a metal layer.
- a resonator having a high Q value comparable to a mechanical Q value is realized by reducing the loss of an AC signal due to the resistance of a barrier existing at the junction interface between a metal and a semiconductor layer in the MEMS resonator. I can do it.
- FIG. 1 is a plan view of the MEMS resonator according to the first embodiment shown in FIG. Sectional drawing shown typically for operation
- FIG. 3 is a perspective view showing a basic configuration of a MEMS resonator according to a second embodiment of the present invention.
- movement description of the MEMS resonator of Embodiment 2 Sectional drawing which showed typically the vibrator end part vicinity (a support part is included) in the MEMS resonator of Embodiment 2.
- FIG. A perspective view showing a basic composition of a MEMS resonator according to a third embodiment of the present invention. Sectional drawing shown typically for operation
- FIG. 16 is a cross-sectional view taken along line AA of the conventional MEMS resonator of FIG. 16 taken along line BB.
- the graph which shows an example of the VI characteristic curve in the junction interface of a metal layer and a p-type semiconductor A circuit diagram showing an equivalent circuit of the ideal resonator of FIG. Circuit diagram showing an equivalent circuit in consideration of a barrier existing in an actual device in a MEMS resonator
- the MEMS resonator of the present invention is not limited to the resonator having the configuration described in the following embodiment, but the technical idea equivalent to the technical idea described in the following embodiment and the present technology. It includes a MEMS resonator configured based on common technical knowledge in the field.
- the thickness, size, shape, and the like are exaggerated in order to show the structure of a micromechanism called a MEMS resonator.
- FIG. 1 is a perspective view showing a basic configuration of the MEMS resonator according to the first embodiment of the present invention.
- FIG. 2 is a plan view of the MEMS resonator according to the first embodiment shown in FIG. 3 and 4 are cross-sectional views schematically shown for explaining the operation of the MEMS resonator according to the first embodiment.
- FIG. 3 shows a cross section taken along the line CC of the MEMS resonator in FIG.
- FIG. 4 shows a cross section taken along line DD of the MEMS resonator of FIG.
- FIG. 4 shows the vicinity of one end of the vibrator.
- the MEMS resonator according to the first embodiment is manufactured using an SOI (Silicon On On Insulator) substrate.
- the top layer Si of the SOI substrate is etched to face the beam-type vibrator 1 and the vibrator 1.
- an input electrode 2 and an output electrode 3 are formed.
- the vibrator 1 is formed in a double-supported beam shape by etching a part of a BOX (BurieduriOxide) layer. That is, both ends of the vibrator 1 are supported by the support portion 4, and the vibrator 1 is in a state where it can bend and vibrate.
- the support portions 4 at both ends of the input electrode 2, the output electrode 3, and the vibrator 1 are tethered to the silicon substrate 5 via the buried oxide film 6 by the remaining BOX layer.
- the input electrode 2 and the output electrode 3 are arranged on both side surfaces of the vibrator 1 via a gap, and by applying a DC voltage Vp to the vibrator 1, A direct current potential difference is applied between the input electrode 2 and the vibrator 1 and between the output electrode 3 and the vibrator 1.
- the vibrator 1, the input electrode 2, and the output electrode 3 are all n-type semiconductors.
- Two metal layers are formed on each of the input electrode 2, the output electrode 3, and the support portion 4 of the vibrator 1.
- a first input side metal layer 7 and a second input side metal layer 8 are spaced apart from each other on the surface of the input electrode 2.
- a first output side metal layer 11 and a second output side metal layer 12 are disposed on the surface of the output electrode 3 so as to be separated from each other.
- the first support side metal layer 9 and the second support side metal layer 10 are arranged on the surface of one support portion 4 at both ends of the vibrator 1 so as to be separated from each other.
- each of the first input side metal layer 7 and the second input side metal layer 8 is an intermediate layer disposed on the surface of the input electrode 2, and the first output side metal layer 11.
- the second output-side metal layer 12 are intermediate layers arranged on the surface of the output electrode 3, and the first support-side metal layer 9 and the second support-side metal layer 10 are each the support portion 4. It is an intermediate
- the MEMS resonator when an AC voltage is applied to the input electrode 2, the potential difference between the input electrode 2 and the vibrator 1 fluctuates and the vibrator 1 vibrates.
- the frequency of the AC voltage applied to the input electrode 2 and the mechanical resonance frequency of the vibrator 1 coincide with each other, the vibrator 1 vibrates greatly, and a displacement current associated with the vibration is output from the output electrode 3 It is.
- an AC voltage Vi is input from the input terminal 20 via the first input-side metal layer 7 and the input electrode 2, and the output terminal 21 is configured to output an alternating current Io (AC) via the output electrode 3 and the second output-side metal layer 11.
- a bias DC voltage Vp is applied to the vibrator 1 via the support portion 4.
- the electrical signal path from the input terminal 20 to the output terminal 21 has a barrier at the junction interface where the metal layer and the n-type semiconductor are joined. They are electrically coupled at the bonding interface.
- a direct current is passed through the junction interface between the metal layer and the n-type semiconductor, and the direct current flows to the common potential source through the direct current bias circuit.
- the DC bias circuit is a circuit that allows only an injected DC current to escape without passing an AC signal, and is common to an element having a high impedance with respect to an AC signal in a frequency band near the resonance frequency of the vibrator 1.
- a potential source Specifically, for example, a coil element or a resistance element whose one end is grounded is used.
- the coil element or resistance element of the DC bias circuit is set to a value of 100 k ⁇ or more to prevent the AC signal from flowing into the DC bias circuit. is doing.
- FIG. 3 the role of the bypass resistor 14 which is an impedance element in the DC bias circuit 22 provided on the signal input side will be described.
- An AC voltage Vi (AC) of an AC signal is applied to the input terminal 20.
- a DC voltage Vi (DC) from a DC power source is applied to the first input side metal layer 7 to which the input terminal 20 is connected via the coil 33. Therefore, a voltage in which the direct current voltage Vi (DC) and the alternating current voltage Vi (AC) are superimposed is applied to the first input side metal layer 7.
- the alternating current Ii passes through the first input-side metal layer 7 and the input electrode 2 (n-type), and passes through the capacitance (Ci) of the input-side facing portion 25, thereby the vibrator 1 (n-type).
- the input side facing portion 25 is a capacitance portion constituted by the surfaces of the input electrode 2 and the vibrator 1 facing each other.
- the alternating current Ii (AC) flows from the vibrator 1 through the support portion 4 to the ground potential serving as a common potential source via the first support-side metal layer 9.
- an alternating current Ii (AC) flows in the direction of the bias power source 15 having an internal resistance value lower than that of the support side bypass resistor 16.
- the DC current Ii (DC) by the DC voltage Vi (DC) passes through the first input side metal layer 7 and the input electrode 2 (n-type), and the second And flows through the input metal layer 8 to the ground potential as a common potential source via the bypass resistor 14.
- the value of the input-side bypass resistor 14 is set larger than the impedance of the capacitance (Ci) of the input-side facing portion 25. For this reason, the amount of the alternating current Ii (AC) flowing into the bypass resistor 14 can be ignored.
- a DC voltage Vo (DC) is applied to the first output-side metal layer 11 connected to the output terminal 21.
- This direct-current voltage Vo (DC) is applied via the coil 18 having a high impedance with respect to the frequency of the alternating-current signal flowing in the MEMS resonator.
- the direct current Io (DC) by the direct current voltage Vo (DC) passes through the first output side metal layer 11, the output electrode 3 (n-type), and the second output side metal layer 12 through the bypass resistor 19. It flows into the ground potential that becomes the common potential source.
- the output alternating current Io (AC) generated by the change in the capacitance (Co) of the output-side facing portion 26 due to the vibration of the vibrator 1 is obtained from the ground potential shown in FIG. It flows to the support unit 4 and the vibrator 1.
- the output-side facing portion 26 is a capacitance portion constituted by the facing surfaces of the vibrator 1 and the output electrode 3. 3 is followed by an electric signal path from the vibrator 1 to the capacitance (Co) of the output-side facing portion 26, the output electrode 3, the first output-side metal layer 11, and the output terminal 21, and the output alternating current Io ( AC) is output.
- the bias voltage Vp of the bias power supply 15 is applied to the first support-side metal layer 9.
- the direct current Ip (DC) generated by the bias voltage Vp passes through the first support side metal layer 9 and the support part 4, and then passes through the second support side metal layer 10 and the bypass resistor 16 to the common potential source. Flows into the ground potential.
- the first support side metal layer 9 is connected to the bias power source 15 via the bias terminal.
- the direct current Ii (DC) flows simultaneously when the input alternating current Ii (AC) passes through the junction interface between the first input side metal layer 7 and the input electrode 2. Similarly, when the output AC current Io (AC) passes through the junction interface between the output electrode 3 and the first output side metal layer 11, the DC current Io (DC) flows simultaneously.
- FIG. 5 shows the S parameter S21 indicating the input / output relationship of the AC signal.
- the horizontal axis represents the frequency [MHz]
- the vertical axis represents the transfer characteristic S21 [dB].
- the MEMS resonator has a resonance frequency of about 20 MHz.
- the loss due to the resistance is reduced, and the peak of the resonance waveform is sharp as shown in FIG. That is, the configuration of the MEMS resonator of the first embodiment is improved so as to show a high Q value.
- Qm purely mechanical Q value
- the sharpness of resonance is shown. It can be seen that the degree approaches the ideal value Qm.
- a MEMS resonator having a high Q value improves the minimum detection quality, for example, as a mass detector, and enables low phase noise as an oscillator.
- the bypass resistors (14, 16, 19) used in the DC bias circuit should be used as long as they have a function of blocking AC frequency signal components near the resonance frequency. It is possible to use an element having a high impedance in a coil, a semiconductor resistance element, or the like.
- the coil 18 provided in the output side bias circuit 24 may be a resistance element or a semiconductor resistance element as long as it has a function of blocking an AC frequency signal component near the resonance frequency.
- FIG. 6 is a perspective view showing a basic configuration of the MEMS resonator according to the second embodiment of the present invention.
- 7 and 8A are cross-sectional views schematically shown for explaining the operation of the MEMS resonator according to the second embodiment.
- 7 shows a cross section taken along line EE of the MEMS resonator of FIG. 6
- FIG. 8 shows a cross section taken along line FF of the MEMS resonator of FIG.
- FIG. 8A the vicinity of one end of the vibrator (including the support portion 4) is shown.
- the MEMS resonator of the second embodiment is different from the configuration of the MEMS resonator of the first embodiment described above in that an intermediary layer is provided between the metal layer and the input / output electrode.
- Other configurations are the same as those of the MEMS resonator of the first embodiment, and are formed by the same manufacturing method. Therefore, in the MEMS resonator according to the second embodiment, the same reference numerals are given to components having the same functions and configurations as those of the MEMS resonator according to the first embodiment, and the description of the first embodiment is applied to the description.
- the intermediate layer is configured by the metal layer and the mediation layer.
- a metal layer is formed on each of the n-type semiconductor input electrode 2, the output electrode 3, and the support portion 4 via the mediation layer of two p-type semiconductor layers.
- the role of the mediating layer which is a p-type semiconductor layer, is used as a spacer for forming a surface higher than the height of the vibrator 1.
- a closed space is formed around the vibrator 1 to block dust and the like from entering the cavity from the outside. Protects against inhibitors.
- the cavity can be kept in a vacuum to obtain a resonance characteristic with high sharpness from which the viscosity of air is eliminated.
- a junction interface between the metal and the p-type semiconductor and a pn junction interface exist in the electrical signal path, and these junction interfaces form a barrier.
- the electric signal path from the input terminal 20 to the output terminal 21 has a junction interface (junction interface) where the metal layer and the p-type semiconductor, and the p-type semiconductor and the n-type semiconductor are joined.
- a barrier is interposed and is electrically coupled at the junction interface.
- a direct current is passed through the junction interface between the metal layer and the p-type semiconductor and between the p-type semiconductor and the n-type semiconductor, and the direct current passes through the direct-current bias circuit. It was set as the structure which flows into.
- the DC bias circuit is the same as the DC bias circuit in the first embodiment described above, and is a circuit that allows only an injected DC current to escape without passing an AC signal, and a frequency band near the resonance frequency of the vibrator 1. Are composed of an element having a high impedance with respect to the AC signal and a common potential source.
- an intermediate layer composed of a laminate of the first input-side mediating layer 27 (p-type) and the first input-side metal layer 7 is provided on the surface of the input electrode 2.
- An intermediate layer composed of a laminate of the second input-side mediating layer 28 (p-type) and the second input-side metal layer 8 is spaced apart.
- An intermediate layer composed of a laminate of 32 (p-type) and the second output-side metal layer 12 is spaced apart.
- the intermediate layer formed of a layered body and a laminate of the second support-side mediating layer 30 (p-type) and the second support-side metal layer 10 are arranged apart from each other.
- the role of the bypass resistor 14 in the DC bias circuit 22 provided on the signal input side is the same as that of the bypass resistor 14 described in the first embodiment.
- An AC voltage Vi (AC) of an AC signal is applied to the input terminal 20.
- a DC voltage Vi (DC) from a DC power source is applied to the first input side metal layer 7 to which the input terminal 20 is connected via the coil 33. Therefore, a voltage in which the direct current voltage Vi (DC) and the alternating current voltage Vi (AC) are superimposed is applied to the first input side metal layer 7.
- the alternating current Ii passes through the first input-side metal layer 7, the first input-side mediating layer 27 (p-type), and the input electrode 2 (n-type), and the capacitance ( It flows to the vibrator 1 (n-type) via Ci).
- the alternating current Ii (AC) passes from the vibrator 1 through the support portion 4 and passes through the first support-side mediating layer 29 and the first support-side metal layer 9 to the common potential. It flows into the ground potential as the source.
- an alternating current Ii (AC) flows in the direction of the bias power source 15 having an internal resistance value lower than that of the bypass resistor 16.
- the DC current Ii (DC) by the DC voltage Vi (DC) is applied to the first input side metal layer 7 and the first input side mediating layer 27 (p-type). , Passes through the input electrode 2 (n-type), passes through the second input-side mediating layer 28 (p-type) and the second input-side metal layer 8 and flows to the ground potential via the bypass resistor 14.
- the value of the input-side bypass resistor 14 is set larger than the impedance of the capacitance (Ci) of the input-side facing portion 25. For this reason, the amount of the alternating current Ii (AC) flowing into the bypass resistor 14 can be ignored.
- a DC voltage Vo (DC) is applied to the first output-side metal layer 11 connected to the output terminal 21.
- This direct-current voltage Vo (DC) is applied via the coil 18 having a high impedance with respect to the frequency of the alternating-current signal flowing in the MEMS resonator.
- the direct current Io (DC) by the direct current voltage Vo (DC) passes through the first output side metal layer 11, the first output side mediating layer 31 (p-type), the output electrode 3 (n-type), and the second Through the output-side mediating layer 32 (p-type) and the second output-side metal layer 12, and flows through the bypass resistor 19 to the ground potential which is a common potential source.
- the output alternating current io (AC) generated by the change in the capacitance of the output-side facing portion 26 due to the vibration of the vibrator 1 is the first support-side metal layer 9 and the first support from the ground potential shown in FIG. 8A. It flows to the side mediating layer 29, the support 4, and the vibrator 1. Then, electricity from the vibrator 1 shown in FIG. 7 to the capacitance (Co) of the output side facing portion 26, the output electrode 3, the first output side mediating layer 31, the first output side metal layer 11, and the output terminal 21. Following the signal path, an output alternating current Io (AC) is output.
- the bias voltage Vp of the bias power supply 15 is applied to the first support-side metal layer 9. Therefore, the direct current Ip (DC) generated by the bias voltage Vp passes through the first support side metal layer 9, the first support side mediation layer 29, the support portion 4, and the second support side mediation layer 30. It flows into the ground potential via the second support side metal layer 10 and the bypass resistor 16.
- the first support side metal layer 9 is connected to the bias power source 15 via the bias terminal.
- the input alternating current Ii (AC) and the output alternating current Io (AC) are applied to the first support side metal layer 9, the first support side mediating layer 29, and the support part 4.
- a direct current Ip (DC) flows simultaneously. That is, a DC current is superimposed on an AC current at a metal-semiconductor (metal-n junction, metal-p junction) junction interface or a p-type n-type semiconductor (pn junction, pp junction, nn junction) junction interface. ing.
- the operating point can be moved, the load resistance applied to the AC current can be reduced, and the resistance when no DC current is passed.
- the resistance value r ′ (see FIG. 20) can be made smaller than the value r. Therefore, the electrical energy loss of alternating current can be significantly reduced.
- the second embodiment is not limited to the configuration shown in FIG. 8A, and may be configured as shown in FIGS. 8B to 8E, for example.
- the configuration shown in FIG. 8B shows a cross-sectional view similar to FIG. 8A, except that the first support-side metal layer 9 is connected to the bias power source 15 via the bias terminal and the bypass resistor 16, and the second The support-side metal layer 10 is connected to the ground potential.
- FIGS. 8C to 8E are cross-sectional views showing the configuration of the double-supported beam type vibrator 1 with the intermediate portion omitted, and the vibrator 1 is provided with an intermediate layer on each of the support portions 4A and 4B on both sides. 1 is configured to pass a direct current. That is, the first support portion 4A is provided with the first intermediate layer composed of the first support side metal layer 9 and the first support side mediating layer 29, and the second support portion 4B is provided with the second support side. A second intermediate layer composed of the metal layer 10 and the second support-side mediating layer 30 is provided.
- the first support-side metal layer 9 of the first intermediate layer formed on the first support portion 4A is connected to the bias power source 15 via the bias terminal, and the second support portion.
- the second support side metal layer 10 of the second intermediate layer formed on 4B is connected to the ground potential via the bypass resistor 16.
- the first support-side metal layer 9 of the first intermediate layer formed on the first support portion 4A is connected to the bias power source 15 via the bias terminal and the bypass resistor 16
- the second support side metal layer 10 of the second intermediate layer formed on the second support portion 4B is connected to the ground potential.
- the first support-side metal layer 9 of the first intermediate layer formed on the first support portion 4A is connected to the bias power source 15 via the bias terminal, and the second support portion The second support side metal layer 10 of the second intermediate layer formed on 4B is connected to the ground potential.
- no impedance element is provided in the DC bias circuit, but the vibrator 1 is included in the current path of the DC bias circuit, and the vibrator itself has impedance. No further impedance element is required.
- the peak of the resonance waveform becomes sharp and high as shown in FIG. 5 in the same manner as the MEMS resonator according to the first embodiment. Improved to show Q value.
- the same reference numerals are given to those having the same function and configuration as those of the MEMS resonator of the second embodiment, and the description of the second embodiment is applied to the description.
- the intermediate layer is configured by the metal layer and the mediation layer.
- FIG. 9 is a perspective view showing a basic configuration of the MEMS resonator according to the third embodiment of the present invention.
- 10 and 11 are cross-sectional views schematically shown for explaining the operation of the MEMS resonator according to the third embodiment.
- FIG. 10 shows a cross section taken along line GG of the MEMS resonator in FIG.
- FIG. 11 shows a cross section taken along line HH of the MEMS resonator of FIG.
- FIG. 11 shows the vicinity of one end of the vibrator.
- the first support-side metal layer 9 formed on the support portion 4 is connected to the ground potential via the bypass resistor 19.
- the second support-side metal layer 10 is connected so that the bias voltage Vp is input via the coil 18.
- the second support side metal layer 10 is connected to the output terminal 21.
- the configuration on the input electrode side is the same as that of the second embodiment. Therefore, in the MEMS resonator according to the third embodiment, the support unit 4 supports both the vibrators 1 and has a function as an output electrode. Therefore, also in the configuration of the third embodiment, the electrical signal path includes a junction interface between the metal and the p-type semiconductor and a junction interface of the pn junction interface, and these junction interfaces serve as barriers.
- the input alternating current Ii passes through each junction interface of the first input-side metal layer 7, the first input-side mediating layer 27, and the input electrode 2.
- a direct current Ii flows.
- Io AC current
- the output AC current Io AC
- the second support-side mediating layer 30, and the second support-side metal layer 10 the DC current is simultaneously applied.
- Ip DC
- Ip DC
- a DC current is superimposed on an AC current at a metal-semiconductor junction interface or a p-type n-type semiconductor junction interface.
- the operating point can be moved, the load resistance applied to the AC current can be reduced, and the resistance when no DC current is passed.
- the resistance value r ′ can be made smaller than the value r. Therefore, the electrical energy loss of alternating current can be reduced.
- the peak of the resonance waveform becomes sharper and higher as shown in FIG. 5 in the same manner as the MEMS resonator according to the first embodiment. Improved to show Q value.
- the structure of the vibrator is not limited to the double-supported beam type, but may be a cantilever type.
- various shapes such as a disc (disk) type, a ring (annular) type, and a square (rectangular) type as described in the above-mentioned "Patent Document 1" can be used. It can respond, and is not limited to the beam type. Therefore, the resonance mode excited by the vibrator is not limited to the flexural vibration. For example, even when the vibrator is a beam type, a torsional vibration mode in which the vibrator performs torsional vibration can be used for the MEMS resonator of the present invention.
- the MEMS resonator according to the fourth embodiment of the present invention is an example of a MEMS resonator having a configuration in which a vibrator in a torsional vibration mode is provided.
- the vibrator is a triangular prism having a triangular cross section, and an input electrode and an output electrode are formed so as to face each surface constituting two sides of the triangle.
- Other configurations are the same as those of the MEMS resonator of the second embodiment. Therefore, in the MEMS resonator shown in FIGS.
- the intermediate layer is configured by the metal layer and the mediation layer.
- FIG. 12 is a perspective view showing a basic configuration of the MEMS resonator according to the fourth embodiment of the present invention.
- 13 and 14 are cross-sectional views schematically shown for explaining the operation of the MEMS resonator according to the fourth embodiment.
- 13 shows a cross section taken along line JJ of the MEMS resonator shown in FIG. 12
- FIG. 14 shows a cross section taken along line KK of the MEMS resonator shown in FIG.
- FIG. 14 shows the vicinity of one end of the vibrator.
- the vibrator 1A in the MEMS resonator according to the fourth embodiment has a beam shape with a triangular cross section, and the material is made of single crystal silicon.
- the reason why the cross section of the vibrator 1A is triangular is that it is surrounded by two planes of crystal orientation plane ⁇ 111 ⁇ and ⁇ 100 ⁇ 1 plane.
- a torsional vibration is excited by applying a moment of electrostatic force from the input electrode 2A to the triangular cross section 1A. Torsional vibration is generated in the vibrator 1A, and a current generated by the torsional vibration is output from the output electrode 3A.
- the facing surface of the input electrode 2A is formed so as to face one surface constituting the triangle of the vibrator 1A.
- the facing surface of the output electrode 3A is formed so as to face the other surface constituting the triangle of the vibrator 1A.
- the input-side facing portion 25A is a capacitance portion (Ci) formed by the surfaces facing the input electrode 2A and the vibrator 1A
- the output-side facing portion 26A is a surface facing the vibrator 1A and the output electrode 3A. It is a capacity part (Co) comprised by these.
- the height of the input electrode 2A and the output electrode 3A (symbol h in FIG. 13) is set to the height of the vibrator 1A in order to output the current generated by the torsional vibration. This is set to about 1 ⁇ 2 of (Symbol H in FIG. 13). Further, the input electrode 2A and the output electrode 3A are arranged such that the bottom surfaces of the input electrode 2A and the output electrode 3A are in the same plane. In the MEMS resonator according to the fourth embodiment, other configurations, functions, and operations such as a metal layer, a mediation layer, and a bypass resistor are the same as those of the MEMS resonator according to the second embodiment.
- the input alternating current Ii (AC) is applied to each of the first input side metal layer 7, the first input side mediating layer 27, and the input electrode 2A.
- a direct current Ii (DC) flows simultaneously.
- the output AC current Io (AC) passes through the junction interfaces of the output electrode 3A, the first output-side mediating layer 31, and the first output-side metal layer 11, the DC current Io (DC) is simultaneously generated. Is flowing.
- the input alternating current Ii (AC) and the output alternating current Io (AC) are the first support side metal layer 9 and the first support side.
- Direct current Ip (DC) flows simultaneously when passing through each interface of the mediation layer 29 and the support portion 4. That is, a DC current is superimposed on an AC current at a metal-semiconductor junction interface or a p-type n-type semiconductor junction interface.
- the VI characteristic curve shown in FIG. 20 the operating point can be moved, the load resistance applied to the AC current can be reduced, and the resistance when no DC current is passed.
- the resistance value r ′ can be made smaller than the value r. Therefore, the electrical energy loss of alternating current can be reduced.
- the MEMS resonator of the fourth embodiment configured as described above has a sharp resonance waveform peak as shown in FIG. 5 and exhibits a high Q value. Has been improved.
- the DC operating point defined in the VI (voltage-current) characteristics accompanying the barrier at the junction interface in the metal layer, the mediating layer, the input electrode, the output electrode, etc. is the reverse bias region in the characteristic curve shown in FIG. You can also use it. In particular, the effect obtained by using the reverse bias region becomes significant in a state where an avalanche breakdown exists in the reverse bias region in the VI characteristic curve shown in FIG. By setting the bias direct current in the avalanche breakdown region where the slope of the VI characteristic curve is large, the resistance r 'to the alternating current signal can be significantly reduced.
- connection position between the DC power supply and the common potential source has been specified and described.
- the connection position between the DC power supply and the common potential source is not specified. Even if the connection is reverse to the configuration, the same effect is obtained.
- the DC bias circuit on the input side and the output side only needs to have a configuration having impedance in the DC bias circuit, and does not specify the position where the impedance element is disposed.
- the inductance elements provided in the DC bias circuit on the input side and output side are connected so that the signal that has passed through the junction interface is separated into a DC signal and an AC signal, and only the AC signal flows from the input terminal to the output terminal.
- the present invention is not limited to the configurations described in the above embodiments.
- the MEMS resonator according to the present invention has a filter circuit that utilizes the improvement of the electrical passage characteristics between the input and output electrodes only at a specific frequency, that is, in the vicinity of the resonance frequency of the vibrator, temperature, stress applied to the vibrator, and vibration.
- a filter circuit that utilizes the improvement of the electrical passage characteristics between the input and output electrodes only at a specific frequency, that is, in the vicinity of the resonance frequency of the vibrator, temperature, stress applied to the vibrator, and vibration.
- the MEMS resonator of the present invention As described above, in the MEMS resonator of the present invention, the loss of the AC signal due to the resistance due to the barrier existing on the joint surface of the metal or semiconductor layer is reduced, and the resonance characteristic having a high Q value is exhibited. Therefore, according to the present invention, the minimum detection mass is improved as a mass detector, and low phase noise is enabled as an oscillator, and other filter circuits, gyroscopes, pressure sensors, and optical scanners using resonance are used. It can be used for a wide range of industrial applications such as mass detection elements.
- the MEMS resonator of the present invention can be widely used in various fields in order to reduce the loss of alternating current signal due to the resistance due to the barrier existing on the joint surface of the metal or semiconductor layer and to exhibit a resonance characteristic having a high Q value. it can.
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Abstract
Description
図20は、メタル層とp型半導体との接合界面におけるV-I特性の一例を示すグラフである。図20において、横軸は接合界面の両側の電位差(V)、縦軸は接合界面を貫通する直流電流(I)である。
静電力が印加されて機械的に振動する振動子と、
前記振動子を振動可能に支持する支持部と、
空隙を介して前記振動子と対向する面を有する少なくとも1つの電極と、を有し、
前記支持部または前記電極のうちの1つが入力電極であり、前記支持部または前記電極のうちの他の1つが出力電極であり、
前記入力電極に接続された入力端子を介して印加される交流信号により生じる静電力によって前記振動子を励振させて、前記振動子の振動により発生する電流を前記出力電極に接続された出力端子を介して出力するMEMS共振器であって、
前記入力端子と前記入力電極との間の電流経路、または前記出力電極と前記出力端子との間の電流経路には、pn接合、pp接合、nn接合、メタル-n接合、メタル-p接合の少なくともいずれかの接合界面が形成されており、
前記接合界面に定常的に直流電流を流すための直流バイアス回路を備える。このように構成された本発明に係る第1の態様のMEMS共振器は、MEMS共振器に不要に付随する電気的抵抗損失を抑えて、メカニカルなQ値と遜色のない高いQ値を有する共振器を実現することができる。
前記振動子を振動可能に支持する支持部と、
空隙を介して前記振動子と対向する面を有する少なくとも2つの電極と、を有し、
前記少なくとも2つの電極のうちの1つが入力電極であり、前記少なくとも2つの電極のうちの他の1つが出力電極であり、
前記入力電極に接続された入力端子を介して印加される交流信号により生じる静電力によって前記振動子を励振させて、前記振動子の振動により発生する電流を前記出力電極に接続された出力端子を介して出力するMEMS共振器であって、
前記振動子と一体的に形成された前記支持部にはバイアス端子が接続されており、前記バイアス端子と前記支持部との間の電流経路には、pn接合、pp接合、nn接合、メタル-n接合、メタル-p接合の少なくともいずれかの接合界面が形成されており、
前記接合界面に定常的に直流電流を流すための直流バイアス回路を備える。このように構成された本発明に係る第2の態様のMEMS共振器は、MEMS共振器に不要に付随する電気的抵抗損失を抑えて、メカニカルなQ値と遜色のない高いQ値を有する共振器を実現することができる。
前記接合界面は、前記入力電極と前記第1の中間層との間に形成され、
前記入力端子は、前記第1の中間層を介して前記入力電極に接続され、
前記直流バイアス回路は、
一端が直流電源または共通電極の一方に接続され、他端が前記第1の中間層に接続された第1のインピーダンス素子と、
一端が前記入力電極の表面における前記第1の中間層が形成された領域以外の領域に接続され、他端が前記直流電源または前記共通電極の他方に接続された第2のインピーダンス素子と、を含み、
前記第1のインピーダンス素子はインダクタまたは抵抗を有し、
前記第2のインピーダンス素子はインダクタまたは抵抗を有し、
前記第1のインピーダンス素子および前記第2のインピーダンス素子のいずれか一方は抵抗を有する構成としてもよい。このように構成された本発明に係る第3の態様のMEMS共振器は、入力電極の交流電流の入出力系統に接合界面(バリア)が存在する場合において、交流電流と共に直流電流を同時に流すことにより、交流電流に加わる抵抗損失を低減することができる。
前記第2のインピーダンス素子は、前記第2の中間層を介して前記入力電極に接続された構成としてもよい。このように構成された本発明に係る第4の態様のMEMS共振器は、交流電流と共に直流電流を同時に流して、交流電流に加わる抵抗損失を低減することができる。
前記接合界面は、前記出力電極と前記第1の中間層との間に形成され、
前記出力端子は、前記第1の中間層を介して前記出力電極に接続され、
前記直流バイアス回路は、
一端が直流電源または共通電極の一方に接続され、他端が前記第1の中間層に接続された第1のインピーダンス素子と、
一端が前記出力電極の表面における前記第1の中間層が形成された領域以外の領域に接続され、他端が前記直流電源または前記共通電極の他方に接続された第2のインピーダンス素子と、を含み、
前記第1のインピーダンス素子はインダクタまたは抵抗を有し、
前記第2のインピーダンス素子はインダクタまたは抵抗を有し、
前記第1のインピーダンス素子および前記第2のインピーダンス素子のいずれか一方は抵抗を有する構成としてもよい。このように構成された本発明に係る第5の態様のMEMS共振器は、出力電極の交流電流の入出力系統に接合界面(バリア)が存在する場合において、交流電流と共に直流電流を同時に流すことにより、交流電流に加わる抵抗損失を低減することができる。
前記第2のインピーダンス素子は、前記第2の中間層を介して前記出力電極に接続された構成としてもよい。このように構成された本発明に係る第6の態様のMEMS共振器は、交流電流と共に直流電流を同時に流して、交流電流に加わる抵抗損失を低減することができる。
前記接合界面は、前記支持部と前記第1の中間層との間に形成され、
前記バイアス端子は、第1の配線により、前記第1の中間層を介して前記支持部に接続され、
前記直流バイアス回路は、
前記支持部の表面における前記第1の中間層が形成された領域以外の領域と、共通電極とを接続する第2の配線、を備え、
前記第1の配線または前記第2の配線のいずれか一方の途中に抵抗素子を有する構成としてもよい。このように構成された本発明に係る第7の態様のMEMS共振器は、支持部の交流電流の入出力系統に接合界面(バリア)が存在する場合において、交流電流と共に直流電流を同時に流すことにより、交流電流に加わる抵抗損失を低減することができる。
前記第1の支持部の表面に配置された第1の中間層を有し、
前記接合界面が、前記第1の支持部と前記第1の中間層との間に形成され、
前記バイアス端子が、第1の配線により、前記第1の中間層を介して前記第1の支持部に接続され、
前記直流バイアス回路が、
前記第2の支持部と共通電極とを接続する第2の配線、を備える構成としてもよい。このように構成された本発明に係る第8の態様のMEMS共振器は、支持部の交流電流の入出力系統に接合界面(バリア)が存在する場合において、交流電流と共に直流電流を同時に流すことにより、交流電流に加わる抵抗損失を低減することができる。
前記第2の配線は、前記第2の中間層を介して、前記第2の支持部と前記共通電極とを接続するよう構成してもよい。このように構成された本発明に係る第9の態様のMEMS共振器は、第1の中間層と第2の中間層が振動子を介して接続されているため、インピーダンス素子を振動子が兼用することが可能となり、少ない構成要素で交流電流に加わる抵抗損失を低減することができる。
図1は本発明に係る実施の形態1のMEMS共振器の基本構成を示す斜視図である。図2は図1に示した実施の形態1のMEMS共振器の平面図である。図3および図4は、実施の形態1のMEMS共振器の動作を説明するために模式的に示した断面図であり、図3は図1のMEMS共振器のC-C線による断面を示しており、図4は図1のMEMS共振器のD-D線による断面を示している。なお、図4においては、振動子の一方の端部近傍を示している。
入力端子20に対しては、交流信号の交流電圧Vi(AC)が印加されている。また、入力端子20が接続されている第1の入力側メタル層7には、コイル33を介して直流電源からの直流電圧Vi(DC)が印加されている。したがって、第1の入力側メタル層7には直流電圧Vi(DC)と交流電圧Vi(AC)が重畳した電圧が印加されている。このとき、交流電流Ii(AC)は第1の入力側メタル層7、入力電極2(n型)を通り、入力側対向部25の容量(Ci)を介して、振動子1(n型)に流れる。ここで入力側対向部25とは、入力電極2と振動子1の対向する面により構成された容量部分である。
以下、本発明に係る実施の形態2のMEMS共振器について添付の図面を参照して説明する。
図6は本発明に係る実施の形態2のMEMS共振器の基本構成を示す斜視図である。図7および図8Aは、実施の形態2のMEMS共振器の動作を説明するために模式的に示した断面図である。図7は図6のMEMS共振器のE-E線による断面を示しており、図8は図6のMEMS共振器のF-F線による断面を示している。なお、図8Aにおいては、振動子の一方の端部近傍(支持部4を含む)を示している。
また、出力電極3上の表面においては、第1の出力側仲介層31(p型)と第1の出力側メタル層11の積層体で構成された中間層と、第2の出力側仲介層32(p型)と第2の出力側メタル層12の積層体で構成された中間層が離間して配置されている。
さらに、振動子1の両端部分にある一方の支持部4上の表面においては、第1の支持側仲介層29(p型)と第1の支持側メタル層9の積層体で構成された中間層と、第2の支持側仲介層30(p型)と第2の支持側メタル層10の積層体で構成された中間層が離間して配置されている。
入力端子20に対しては、交流信号の交流電圧Vi(AC)が印加されている。また、入力端子20が接続されている第1の入力側メタル層7には、コイル33を介して直流電源からの直流電圧Vi(DC)が印加されている。したがって、第1の入力側メタル層7には直流電圧Vi(DC)と交流電圧Vi(AC)が重畳した電圧が印加されている。このとき、交流電流Ii(AC)は第1の入力側メタル層7、第1の入力側仲介層27(p型)、入力電極2(n型)を通り、入力側対向部25の容量(Ci)を介して、振動子1(n型)に流れる。
図8Bに示す構成は、図8Aと同様の断面図を示しているが、第1の支持側メタル層9がバイアス端子およびバイパス抵抗16を介してバイアス電源15に接続されており、第2の支持側メタル層10が接地電位に接続された構成である。
以下、本発明に係る実施の形態3のMEMS共振器について添付の図面を参照して説明する。
前述の実施の形態2の構成においては、「入力電極」、「振動子(支持部)」および「出力電極」の3つの構成部を有する例で説明したが、実施の形態3のMEMS共振器は「振動子(支持部)」が「出力電極」を兼ねた構成である。実施の形態3のMEMS共振器の構成において、その他の構成は、実施の形態2のMEMS共振器と同じであり、同じ製造方法により形成される。したがって、実施の形態3のMEMS共振器において、実施の形態2のMEMS共振器と同じ機能、構成を有するものには同じ符号を付してその説明は実施の形態2の説明を適用する。なお、実施の形態3の構成においては、メタル層と仲介層により中間層が構成されている。
したがって、実施の形態3の構成においても、電気信号経路には、メタルとp型半導体との接合界面およびpn接合界面の接合界面が存在し、これらの接合界面が障壁となるバリアとなる。
以下、本発明に係る実施の形態4のMEMS共振器について添付の図12から図14を参照して説明する。
本発明のMEMS共振器においては、振動子の構成として両持ち梁型に限定されるものではなく、片持ち梁型でもよい。また。本発明のMEMS共振器における振動子としては、前述の「特許文献1」に示されているようなディスク(円盤)型、リング(円環)型、スクエア(矩形)型などの多様な形状に対応できるものであり、梁型に限定されるものではない。したがって、振動子に励起される共振モードもたわみ振動に限定されるものではない。例えば、振動子が梁型の場合でも振動子がねじり振動を行うねじり振動モードを本発明のMEMS共振器に利用することができる。
2 入力電極
3 出力電極
4 支持部
5 シリコン基板
6 埋め込み酸化膜
7 第1の入力側メタル層
8 第2の入力側メタル層
9 第1の支持側メタル層
10 第2の支持側メタル層
11 第1の出力側メタル層
12 第2の出力側メタル層
13 入力側直流電源
14 入力側バイパス抵抗
15 支持側バイアス電源
16 支持側バイパス抵抗
17 出力側直流電源
18 出力側コイル
19 出力側バイパス抵抗
20 入力端子
21 出力端子
22 入力側直流バイアス回路
23 支持側直流バイアス回路
24 出力側直流バイアス回路
25 入力側対向部
26 出力側対向部
27 第1の入力側仲介層
28 第2の入力側仲介層
29 第1の支持側仲介層
30 第2の支持側仲介層
31 第1の出力側仲介層
32 第2の出力側仲介層
Claims (14)
- 静電力が印加されて機械的に振動する振動子と、
前記振動子を振動可能に支持する支持部と、
空隙を介して前記振動子と対向する面を有する少なくとも1つの電極と、を有し、
前記支持部または前記電極のうちの1つが入力電極であり、前記支持部または前記電極のうちの他の1つが出力電極であり、
前記入力電極に接続された入力端子を介して印加される交流信号により生じる静電力によって前記振動子を励振させて、前記振動子の振動により発生する電流を前記出力電極に接続された出力端子を介して出力するMEMS共振器であって、
前記入力端子と前記入力電極との間の電流経路、または前記出力電極と前記出力端子との間の電流経路には、pn接合、pp接合、nn接合、メタル-n接合、メタル-p接合の少なくともいずれかの接合界面が形成されており、
前記接合界面に定常的に直流電流を流すための直流バイアス回路を備えるMEMS共振器。 - 静電力が印加されて機械的に振動する振動子と、
前記振動子を振動可能に支持する支持部と、
空隙を介して前記振動子と対向する面を有する少なくとも2つの電極と、を有し、
前記少なくとも2つの電極のうちの1つが入力電極であり、前記少なくとも2つの電極のうちの他の1つが出力電極であり、
前記入力電極に接続された入力端子を介して印加される交流信号により生じる静電力によって前記振動子を励振させて、前記振動子の振動により発生する電流を前記出力電極に接続された出力端子を介して出力するMEMS共振器であって、
前記振動子と一体的に形成された前記支持部にはバイアス端子が接続されており、前記バイアス端子と前記支持部との間の電流経路には、pn接合、pp接合、nn接合、メタル-n接合、メタル-p接合の少なくともいずれかの接合界面が形成されており、
前記接合界面に定常的に直流電流を流すための直流バイアス回路を備えるMEMS共振器。 - 前記入力電極の表面に配置された第1の中間層を有し、
前記接合界面は、前記入力電極と前記第1の中間層との間に形成され、
前記入力端子は、前記第1の中間層を介して前記入力電極に接続され、
前記直流バイアス回路は、
一端が直流電源または共通電極の一方に接続され、他端が前記第1の中間層に接続された第1のインピーダンス素子と、
一端が前記入力電極の表面における前記第1の中間層が形成された領域以外の領域に接続され、他端が前記直流電源または前記共通電極の他方に接続された第2のインピーダンス素子と、を含み、
前記第1のインピーダンス素子はインダクタまたは抵抗を有し、
前記第2のインピーダンス素子はインダクタまたは抵抗を有し、
前記第1のインピーダンス素子および前記第2のインピーダンス素子のいずれか一方は抵抗を有する請求項1に記載のMEMS共振器。 - 前記入力電極の表面に配置され、前記第1の中間層とは離間して配置された第2の中間層を有し、
前記第2のインピーダンス素子は、前記第2の中間層を介して前記入力電極に接続されている請求項3に記載のMEMS共振器。 - 前記出力電極の表面に配置された第1の中間層を有し、
前記接合界面は、前記出力電極と前記第1の中間層との間に形成され、
前記出力端子は、前記第1の中間層を介して前記出力電極に接続され、
前記直流バイアス回路は、
一端が直流電源または共通電極の一方に接続され、他端が前記第1の中間層に接続された第1のインピーダンス素子と、
一端が前記出力電極の表面における前記第1の中間層が形成された領域以外の領域に接続され、他端が前記直流電源または前記共通電極の他方に接続された第2のインピーダンス素子と、を含み、
前記第1のインピーダンス素子はインダクタまたは抵抗を有し、
前記第2のインピーダンス素子はインダクタまたは抵抗を有し、
前記第1のインピーダンス素子および前記第2のインピーダンス素子のいずれか一方は抵抗を有する請求項1に記載のMEMS共振器。 - 前記出力電極の表面に配置され、前記第1の中間層とは離間して配置された第2の中間層を有し、
前記第2のインピーダンス素子は、前記第2の中間層を介して前記出力電極に接続されている請求項5に記載のMEMS共振器。 - 前記支持部の表面に配置された第1の中間層を有し、
前記接合界面は、前記支持部と前記第1の中間層との間に形成され、
前記バイアス端子は、第1の配線により、前記第1の中間層を介して前記支持部に接続され、
前記直流バイアス回路は、
前記支持部の表面における前記第1の中間層が形成された領域以外の領域と、共通電極とを接続する第2の配線、を備え、
前記第1の配線または前記第2の配線のいずれか一方の途中に抵抗素子を有する請求項2に記載のMEMS共振器。 - 前記支持部は、前記振動子の両端を支持する第1の支持部および第2の支持部を有し、
前記第1の支持部の表面に配置された第1の中間層を有し、
前記接合界面は、前記第1の支持部と前記第1の中間層との間に形成され、
前記バイアス端子は、第1の配線により、前記第1の中間層を介して前記第1の支持部に接続され、
前記直流バイアス回路は、
前記第2の支持部と共通電極とを接続する第2の配線、を備える請求項2に記載のMEMS共振器。 - 前記第2の支持部の表面に配置され、前記第1の中間層とは前記振動子を介して離間して配置された第2の中間層を有し、
前記第2の配線は、前記第2の中間層を介して、前記第2の支持部と前記共通電極とを接続する請求項7または請求項8に記載のMEMS共振器。 - 前記第1のインピーダンス素子または前記第2のインピーダンス素子のインピーダンスは、前記入力端子に入力された交流信号の電流が前記直流電源または前記共通電極に流れない値に設定される請求項3乃至6のいずれか1項に記載のMEMS共振器。
- 前記第1の中間層は、メタル層を有して構成された請求項3または5に記載のMEMS共振器。
- 前記第2の中間層は、メタル層を有して構成された請求項4または6に記載のMEMS共振器。
- 前記第1の中間層は、仲介層とメタル層が積層されて構成された請求項3または5に記載のMEMS共振器。
- 前記第1の中間層は、仲介層とメタル層が積層されて構成された請求項4または6に記載のMEMS共振器。
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