JP2016065817A - Ultra-small mass detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultra-small mass detection device highly accurately calculating a mass of a detected mass body with mass detection means capable of controlling a resonance frequency with electrostatic attraction.SOLUTION: An ultra-small mass detection device 100 includes: mass detection means 110 oscillating integrally with a detected mass body; AC voltage application means 120 exciting the mass detection means 110; small oscillation measurement means 130 measuring small oscillation of the mass detection means 110; detected side DC voltage application means 140 generating electrostatic attraction to the mass detection means 110; resonance frequency control means 160 making the resonance frequency of the detected side DC voltage application means 140 consistent with the resonance frequency of a detection reference side small mechanical oscillator; and mass calculation means 170 calculating the mass of the detected mass body on the basis of DC voltage applied by the detected side DC voltage application means 140.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultra-small mass detection device using mass detection means capable of controlling a resonance frequency by electrostatic attraction, and in particular, a detected-side micromechanical vibrator that vibrates integrally with a detected mass body. And an ultra-micro mass detection device using mass detection means in which a detection sight-side micro mechanical vibrator that is arranged in parallel and vibrates separately is coupled (that is, vibrates in an interconnected state). is there.

As a conventional mass sensor, there is a mass sensor using a carbon nanotube as a cantilever-like vibrator. In this mass sensor, an additional mass is obtained by measuring a change amount of a resonance frequency of the vibrator (for example, Non-patent document 1).
The following formula shows the relationship between the change amount Δf of the resonance frequency and the additional mass Δm.
Note that f is the resonance frequency of the vibrator before mass is added, and m is the mass of the vibrator before mass is added.
[Formula 1]
Δf = (Δm / 2m) × f

  In such a mass sensor, in order to increase the amount of change in the resonance frequency that occurs when the mass to be detected adheres, the mass of the sensor itself can be reduced, or resonance can be achieved, as is apparent from Equation 1 above. The frequency itself is increased.

K. Jensen et al., “An atomic-resolution nanomechanical mass sensor”, Nature Nanotechnology, 2008, 3, pp.533-537

  However, because carbon nanotubes are used as the sensor material, the weight reduction of the sensor itself has already reached its limit, and the resonance frequency has already reached a high resonance frequency of several hundred MHz to GHz due to its high Young's modulus, Higher resonance frequencies are physically difficult.

  Therefore, the present invention solves the problems of the prior art as described above, that is, the object of the present invention is to detect the natural frequency of the detected micromechanical vibrator and the detection aiming micromechanical vibrator. It is an object of the present invention to provide an ultra-small mass detection device that calculates the mass of a mass to be detected with high accuracy based on a DC voltage when matching the natural frequency with electrostatic attraction.

According to the first aspect of the present invention, a cantilever-like micromechanical vibrator in a cantilever shape that vibrates integrally with a mass to be detected and a cantilever that vibrates separately in parallel with the micromachine vibrator to be detected. The beam-shaped detection aiming side micromechanical vibrator, the detected side micromechanical vibrator, and the detection aiming side micromechanical vibrator are cross-linked to each other at the intermediate connection portion of the detection side micromechanical vibrator and the detection aiming side. Mass detecting means having a bridging connector that vibrates in a state where the micro mechanical vibrators are connected to each other, and an AC voltage for exciting the detected micro mechanical vibrator and the detection aiming micro mechanical vibrator of the mass detecting means An application unit; a microvibration measuring unit that measures a resonance frequency of microvibration generated in each of the detected micromachined vibrator and the detection aiming micromachined vibrator of the mass detecting unit; and a detected side micromachined of the mass detecting unit Mechanical vibrator Detected DC voltage applying means for generating an attractive force, and detecting resonance frequency of the detected micro mechanical vibrator measured by the minute vibration measuring means by controlling the DC voltage of the detected DC voltage applying means. Resonance frequency control means for matching the resonance frequency of the side micro mechanical vibrator, and mass calculation means for calculating the mass of the detected mass body based on the DC voltage applied by the detected DC voltage application means. Thus, the above-described problems are solved.
Here, the “mass of the mass to be detected” referred to in the present invention means an ultra-fine mass of the mass to be detected such as a rare gas, protein, or heavy element.

  In the invention according to claim 2, in addition to the configuration according to claim 1, the detection-side micromechanical vibrator and the detection aiming-side micromechanical vibrator of the mass detection unit are formed on the insulating layer on the silicon substrate. Between the detected ground electrode and the detected-side counter electrode and the detection-target-side counter electrode formed on the insulating layer so as to be opposed to and separated from the ground electrode, respectively. It is a solution.

  The invention according to claim 3 includes, in addition to the configuration according to claim 1 or claim 2, a beam from the free end portion of the detection-side micromechanical vibrator and the detection aiming-side micromechanical vibrator to the bridge connector. The length of the free end of the beam to the intermediate connection site is determined from the length of the beam base end from the ground electrode connection site of the detected micromechanical transducer to be detected and the detection aiming side micromechanical transducer to the beam intermediate connection site with the bridge connector. Further, the above-described problem is further solved by forming the long film.

  According to a fourth aspect of the present invention, in addition to the configuration according to any one of the first to third aspects, a detected-side micromechanical vibrator and a detection-target-side micromechanical vibrator of the mass detection unit, The above-described problems are caused by the detection-side counter electrode terminal and the detection-side counter electrode terminal in a cantilever shape facing each other in the same cross-sectional shape projecting from the detection-side counter electrode and the detection aim-side counter electrode, respectively. Is a further solution.

  In the invention according to claim 5, in addition to the configuration according to claim 4, the length of the beam free end side of the detection-side micromechanical vibrator and the detection aiming-side micromechanical vibrator is the detection-side counter electrode. The above-described problems are further solved by forming the terminal and the detection aiming side counter electrode terminal longer than the protruding length of the beam.

  The invention according to claim 6 is characterized in that, in addition to the configuration according to any one of claims 1 to 5, the resonance frequency of the detected micromachined vibrator on the detection side and the micromachined vibrator on the detection aiming side is set. The initial adjustment DC voltage applying means that is corrected and matched at the initial setting before mass detection is electrostatic attraction on at least one of the detected side micro mechanical vibrator and the detection aim side micro mechanical vibrator of the mass detecting means. The above-described problems are further solved by being connected so as to apply.

  According to the ultra-small mass detection device of the present invention, the mass detection unit, the AC voltage application unit, the micro vibration measurement unit, the detected side DC voltage application unit, the resonance frequency control unit, and the mass calculation unit are provided. By providing at least, the minute vibration measuring means measures the minute vibration generated in each of the detected micro mechanical vibrator and the detection aiming micro mechanical vibrator of the mass detecting means vibrated by the AC voltage applying means, In order for the resonance frequency control means to match the resonance frequency of the detection-side micromechanical vibrator to which the electrostatic attraction force is applied by the detection-side DC voltage application means, the detection-side DC voltage Based on the DC voltage applied by the applying means, the mass of the detected mass body can be calculated by the mass calculating means.

  According to the ultra-small mass detector of the invention according to claim 2, in addition to the effect of the invention according to claim 1, the detected-side micro-mechanical vibrator and the detection-sight-side micro-mechanical vibrator of the mass detecting means However, a micro-vibration can be freely made between a ground electrode formed on an insulating layer on a silicon substrate and a detection-side counter electrode and a detection aiming-side counter electrode formed on the insulating layer so as to face and separate from the ground electrode. Since it is possible to apply electrostatic attraction force separately to the detected-side micromechanical vibrator and the detection-targeting-side micromechanical vibrator, respectively, the detected-side micromechanical vibrator and the detection aiming are arranged. Each resonance frequency of the side micro mechanical vibrator can be controlled separately.

  According to the ultra-small mass detection device of the invention of claim 3, in addition to the effect of the invention of claim 1 or claim 2, the detected-side micromechanical vibrator and the detection aiming-side micromechanical vibrator The length of the free end of the beam from the free end of the beam to the intermediate link of the bridge to the bridge connector is determined from the ground electrode connection site of the detected micromechanical transducer to be detected and the detection aiming micromechanical transducer to the bridge coupler. Since it is possible to increase the amplitude of the beam free end by making it longer than the beam base end side length to the beam intermediate connection part, even if it is a minute vibration at the time of mass detection, Mass can be detected with high sensitivity.

  According to the ultra-small mass detection device of the invention according to claim 4, in addition to the effect exerted by the invention according to any one of claims 1 to 3, the detected-side micro mechanical vibration of the mass detection means The detection-side counter electrode terminal and the detection-side counter electrode terminal in the form of a cantilever arranged opposite to each other in the same cross-sectional shape as the child and the detection-sight-side micro mechanical vibrator are respectively connected to the detection-side counter electrode and the detection aim-side counter electrode. By projecting, the detection side micro-mechanical vibrator and detection aiming side micro-mechanical vibrator of the mass detection means and the detection side counter electrode terminal on the detection side counter electrode side and the detection aiming side on the detection aiming side counter electrode side Since AC voltage and DC voltage are reliably applied between the counter electrode terminals, the microscopic vibration due to resonance and the restoring force due to electrostatic attraction are surely generated, making the mass of the detected mass more ultra-high accuracy. Can detect Kill.

  According to the ultra-small mass detection device of the invention according to claim 5, in addition to the effect of the invention according to claim 4, the free end of the beam of the detection-side micro mechanical vibrator and the detection aiming micro-mechanical vibrator Since the side length is longer than the beam protruding length of the detected side counter electrode terminal and the detection aiming side counter electrode terminal, the restoring force due to electrostatic attraction is opposed to the detected side counter electrode terminal and the detection aiming side. The resonance frequency can be reliably controlled because the detection side micro mechanical vibrator and the detection aim side micro mechanical vibrator are generated relative to the electrode terminal.

  According to the ultra-small mass detection device of the invention according to claim 6, in addition to the effect exerted by the invention according to any one of claims 1 to 5, the detected-side micro mechanical vibrator and the detection aim DC voltage application means for initial adjustment for correcting and matching the resonance frequency with the side micro mechanical vibrator at the time of initial setting before mass detection is the detected micro mechanical vibrator and the detection aiming side micro mechanical vibrator of the mass detecting means The electrostatic attraction force is applied to at least one of the detection-side micromechanical vibrator and the detection-targeting micromechanical vibrator of the mass detection means. Because it is possible to correct the operating error between the detected micro-mechanical transducer and the detection aiming micro-mechanical transducer at the initial setting before mass detection, the initial setting work before mass detection is reduced and the detected error is detected. Mass of mass It can be detected more ultrahigh precision.

1 is a block diagram showing the overall configuration of an ultra-small mass detector that is an embodiment of the present invention. The perspective view of the mass detection means which is one Example of this invention. The top view of the mass detection means which is one Example of this invention.

  The ultra-small mass detection device of the present invention is a cantilever-like micromachined vibrator that can be vibrated integrally with a mass to be detected, and the micromachined vibrator that is to be detected is arranged in parallel to vibrate separately. The detection-side micromechanical vibrator and the detection can be performed by cross-linking each other at a beam intermediate connection portion of the cantilever-shaped detection aiming-side micromechanical vibrator, the detected-side micromechanical vibrator, and the detection-targeting micromechanical vibrator. Mass detecting means having a bridging connector that vibrates in a state where the sighting side micro mechanical vibrators are connected to each other, and the detected side micro mechanical vibrator and the detection aiming side micro mechanical vibrator of the mass detecting means are vibrated. AC voltage application means, micro vibration measuring means for measuring micro vibrations respectively generated in the detection side micro mechanical vibrator and the detection aiming side micro mechanical vibrator of the mass detection means, and the detection side micro machine of the mass detection means Electrostatic attraction to vibrator Detected side DC voltage applying means for generating the detection side, and detecting the resonance frequency of the detected side micro mechanical vibrator measured by the minute vibration measuring means by controlling the DC voltage of the detected side DC voltage applying means. Resonance frequency control means for matching the resonance frequency of the mechanical vibrator, and mass calculation means for calculating the mass of the detected mass body based on the DC voltage applied by the DC voltage application means on the detected side As long as the mass of the mass to be detected is calculated by the mass calculating unit based on the DC voltage applied by the side DC voltage applying unit, the specific embodiment thereof may be any.

Here, examples of the specific mass to be detected that can be detected by the ultra-small mass detector of the present invention include dilute gas, protein, heavy element, and the like. Even if it is a detection mass body, it does not matter.
In other words, the detection target of the ultra-small mass detection device of the present invention is a substance having a mass on the order of zg (10 ^ (− 24) kg).
In addition, as for the attachment position of the detected mass body with respect to the detection-side micro mechanical vibrator, the attachment position in the width direction may be anywhere as long as it is the tip of the detection-side micro mechanical vibrator.

  The specific form of the mass detection means used in the ultra-small mass detection apparatus of the present invention includes a cantilever-like micromachined vibrator on the detection side that vibrates integrally with the mass to be detected, and the detection-side micromachine. Cantilever-shaped detection aiming-side micromechanical vibrators that are arranged in parallel with the mechanical vibrator and vibrate separately from each other at the beam intermediate connection part of the detected-side micromechanical vibrator and the detection-targeting micromechanical vibrator It is only necessary to have a bridging connector that vibrates in a state where the detected micromachine vibrator and the detection-side micromechanical oscillator are connected to each other. Regarding the specific cross-sectional shape of the detection-side counter electrode terminal, the cross-sectional shape of the detection-side micro mechanical vibrator and the detection aiming-side micro mechanical vibrator is the same as the cross-sectional shape of the detection-side counter electrode terminal and the detection aiming-side counter electrode terminal. Rectangular if identical Cross, no problem at all be of any cross-sectional shape such as circular cross section, oval cross section.

  Furthermore, as the micro vibration measurement means used in the ultra-small mass detection apparatus of the present invention, an optical heterodyne micro vibration measurement apparatus that generates measurement light having a spot diameter of measurement light of about 5.0 μm may be used. In order to measure the amplitudes of the detection-side micro-mechanical vibrator and the detection-sight-side micro-mechanical vibrator with higher accuracy, it is preferable to use a micro-vibration measuring device having a measurement area smaller than 5.0 μm.

  In addition, each dimension of the mass detection means described in the following embodiments is merely an example for explaining the present invention, and a mass to be detected is generated by surely generating a micro vibration due to resonance or a restoring force due to electrostatic attraction. As long as the mass can be detected, it is not limited to each dimension.

  Hereinafter, an ultra-small mass detection apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing the overall configuration of an ultra-small mass detection apparatus 100 that is an embodiment of the present invention.
The ultra-small mass detection apparatus 100 according to the present embodiment includes a mass detection unit 110 that measures a minute mass of a mass M to be detected, and an AC power source that is an AC voltage application unit that applies an AC voltage to the mass detection unit 110. 120, the detected-side DC power supply 140 which is a detected-side DC voltage applying means for applying a DC voltage to the mass detecting means 110, and the initial detection of the mass detecting means 110 by applying a DC voltage to the mass detecting means 110. And an initial adjustment DC power supply 150 which is an initial adjustment DC voltage application means to be performed.
Further, the ultra-small mass detection device 100 includes an optical heterodyne micro vibration measurement device 130 that is a micro vibration measurement unit that measures the vibration of the micro mechanical vibrator included in the mass detection unit 110, and the optical heterodyne micro vibration measurement device 130. Resonance frequency control means 160 for calculating a control amount C for controlling the detected DC power source 140 based on the obtained vibration information Iv, and the detected side applied to the mass detecting means 110 from the detected DC power supply 140 Mass calculating means 170 for calculating the mass based on the detected side applied DC voltage amount I (V-DC) of the applied DC voltage V (DC-T) is provided.

First, the mass detector 110 used in the ultra-small mass detector 100 of the present embodiment will be described in detail with reference to FIGS.
As shown in FIG. 2, the mass detection unit 110 is formed on an SOI (Silicon On Insulator) substrate having an insulating layer I between the silicon layer S1 and the silicon layer S2.

In the silicon layer S1, the silicon layer S11, the silicon layer S12, and the silicon layer S13 are separated from each other by etching, and the silicon layer S12 and the silicon layer S13 are separated from each other.
A ground electrode Eb made of chromium and gold is formed on the silicon layer S11, and a detection-side counter electrode Et made of chromium and gold is formed on the silicon layer S12. Is formed with a detection aiming side counter electrode Es made of chromium and gold.

Further, the positive electrode side of the AC power source 120 and the positive electrode side of the detected DC power source 140 are connected to the detected counter electrode Et.
The positive electrode side of the AC power source 120 and the positive electrode side of the initial adjustment DC power source 150 are connected to the detection aiming side counter electrode Es.
The ground electrode Eb is connected to the negative electrode side of the AC power source 120, the negative electrode side of the detected DC power source 140, and the negative electrode side of the initial adjustment DC power source 150.

The mass detection means 110 is formed on the ground electrode Eb, the detection-side counter electrode terminal 114 protrudes from the detection-side counter electrode Et, and the detection-sight-side counter electrode Es The detection aiming side counter electrode terminal 115 protrudes.
Thus, the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 of the mass detection means 110 described later, the detection-side counterelectrode terminal 114 on the detection-side counterelectrode side, and the detection-targeting counterelectrode side An AC voltage or a DC voltage is reliably applied to the detection aiming side counter electrode terminal 115.

Furthermore, a cantilever-like detection-side counter electrode terminal 114 and a detection-sight-side counter electrode terminal 115 that are arranged opposite to each other in the same cross-sectional shape as the detection-side micro mechanical vibrator 111 and the detection aim-side micro mechanical vibrator 112 Projecting from the detection side counter electrode Et and the detection aiming side counter electrode Es.
As a result, an AC voltage or a DC voltage is reliably applied between the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 and the detected side counter electrode terminal 114 and the detection aiming side counter electrode terminal 115. Is done.

A detailed structure of the mass detection unit 110 will be described with reference to FIG. 3 which is a plan view of the mass detection unit 110.
A detection-side micromechanical vibrator 111 having a length of about 6.0 μm and a detection aiming-side micromechanical vibrator 112 having a length of about 6.0 μm protrude separately from the ground electrode Eb. The micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 are cross-linked by a cross-linking connector 113 having a length of about 2.0 μm at a beam intermediate connection portion.
Thereby, the resonance of the detected micromechanical vibrator 111 and the detection aiming micromechanical vibrator 112 can be used, and in particular, the primary resonance frequency and resonance mode with the best energy efficiency can be used. .

The aforementioned detected micromechanical vibrator 111 and the detection aiming micromechanical oscillator 112 are cross-linked by a cross-linking connector 113 at a beam intermediate connecting portion.
Accordingly, the first vibration mode in which the vibration mode in the primary resonance of the detected micromechanical vibrator 111 and the vibration mode in the primary resonance of the detection aiming micromechanical vibrator 112 vibrate in the same phase, A vibration mode in the primary resonance of the mechanical vibrator 111 and a second vibration mode in which the vibration mode in the primary resonance of the detection aiming side micro mechanical vibrator 112 vibrates in opposite phases appear.

The rectangular cross-sectional shape of the detection-side micromechanical vibrator 111 has a thickness of about 0.2 μm and a terminal width of about 0.2 μm, and is the same as the cross-sectional shape of the detection-side counter electrode terminal 114.
The rectangular cross-sectional shape of the detection aiming side micro mechanical vibrator 112 has a thickness of about 0.2 μm and a terminal width of about 0.2 μm, and is the same as the cross-sectional shape of the detection aiming-side counter electrode terminal 115. is there.

Furthermore, the beam free end side length L1 (about 4.0 μm) from the free end portion of the above-described detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 to the intermediate beam connecting portion with the bridge connector 113. ) Is based on the beam base end side length L2 (about 2.0 μm) from the ground electrode connecting portion of the detected side micro mechanical vibrator 111 and the detecting aiming side micro mechanical vibrator 112 to the intermediate connecting portion of the beam with the bridge connector 113. Is also formed long.
Thereby, it is possible to increase the amplitude of the beam free end portion in the mass detection means 110.

Further, the length L1 (about 4.0 μm) of the beam free end side of the detected side micromechanical vibrator 111 and the detection aiming side micromechanical vibrator 112 is the detected side counter electrode terminal 114 and the detection aiming side counter electrode terminal 115. This is longer than the beam projection length L3 (about 0.5 μm). The beam free ends of the detected-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 are approximately 0.3 μm from the beam protruding ends of the detected-side counter electrode terminal 114 and the detection aiming-side counter electrode terminal 115. Are opposed to each other at an interval of.
As a result, the restoring force due to the electrostatic attractive force is detected by the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 relative to the detected side counter electrode terminal 114 and the detection aiming side counter electrode terminal 115. It has come to occur.

Returning to FIG. 1, the configuration of the ultra-small mass detection apparatus 100 other than the mass detection unit 110 will be described.
The optical heterodyne microvibration measuring device 130 used in this embodiment is capable of generating measuring light having a measuring light spot diameter of about 5.0 μm. The tip 111a of the mechanical vibrator 111 and the tip 112a of the detection aiming side micro mechanical vibrator 112 are irradiated, and the vibrations of the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 are measured.

  The detected DC power supply 140 used in this embodiment changes the resonance frequency of the detected micromechanical vibrator 111 based on a control amount C calculated by a resonance frequency control means 160 described later, and has a mass. The detection means 110 is connected so as to apply an electrostatic attractive force to the detected micromechanical vibrator 111.

The initial adjustment DC power supply 150 used in the present embodiment corrects and matches the resonance frequencies of the detected micromechanical vibrator 111 and the detection aiming micromechanical oscillator 112 at the time of initial setting before mass detection. Thus, it is connected so as to apply an electrostatic attractive force to the detection aiming side micro mechanical vibrator 112 of the mass detection means 110.
The initial adjustment DC power supply 150 generates an electrostatic attractive force in the mass detection means 110 and the detection aiming-side micromechanical vibrator 112, and at the initial setting before mass detection, the detected-side micromechanical vibrator 111 and the detection aiming-side micromachinement The operation error with the mechanical vibrator 112 is corrected.

  Next, the behavior of the ultra-small mass detection apparatus 100 according to the first embodiment of the present invention in a state where the detected mass body M is not attached will be described.

First, the AC power supply 120 applies the detected-side applied AC voltage V (AC-T) between the detected-side counter electrode Et and the ground electrode Eb, and between the detection-sight-side counter electrode Es and the ground electrode Eb. The detection aiming side applied AC voltage V (AC-S) is applied.
As a result, the periodic electrostatic attractive force F (dT) between the detection-side micromechanical vibrator 111 and the detection-side counter electrode terminal 114 causes the detection aiming-side micromechanical vibrator 112 and the detection aiming-side counter electrode terminal. A periodic electrostatic attraction force F (dS) works with 115.
That is, electrostatic attraction is separately applied to the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112.
Due to such separate periodic electrostatic attractive force F (dT) and electrostatic attractive force F (dS), a periodic restoring force acts on the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112. The to-be-detected micro mechanical vibrator 111 and the detection aiming micro mechanical vibrator 112 freely vibrate.

  Here, the beam free end side length L1 of the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 is the beam protruding length of the detected side counter electrode terminal 114 and the detection aiming side counter electrode terminal 115. By being formed longer than L3, the restoring force due to the electrostatic attractive force is relatively detected with respect to the detected counter electrode terminal 114 and the detection aiming counter electrode terminal 115, and the detected micro mechanical vibrator 111 and the detection aiming. It occurs in the side micro mechanical vibrator 112.

Furthermore, the frequencies of the detected side applied AC voltage V (AC-T) and the detected aiming side applied AC voltage V (AC-S) applied to the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112. To sweep.
Accordingly, the frequency of the detected side applied AC voltage V (AC-T) and the detection aiming side applied AC voltage V (AC-S) and the characteristics of the detected side micromechanical vibrator 111 and the detection aiming side micromechanical vibrator 112 are unique. When the frequencies coincide with each other, the detected micromechanical vibrator 111 and the detection aiming micromechanical oscillator 112 resonate.

Then, the measurement light is irradiated from the optical heterodyne microvibration measuring device 130 to the tip 111a of the detected micromechanical vibrator 111 that vibrates as described above, and the vibration of the detected micromechanical vibrator 111 is detected. The detected-side micromechanical vibrator vibration information I (v−T) is obtained.
The optical heterodyne micro vibration measuring device 130 can also irradiate the tip 112a of the detection aiming side micro mechanical vibrator 112 with the measurement light, and the detection aiming side micro mechanical vibrator vibration of the detection aiming side micro mechanical vibrator 112. Information I (v-S) can also be obtained.

  Here, when the physical properties and dimensions of the to-be-detected micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 completely match, only the first vibration mode appears. This is called a fully coupled state.

  Subsequently, the ultra-small mass detection apparatus 100 according to the first embodiment of the present invention in the case where the physical properties and dimensions of the detected-side micro mechanical vibrator 111 and the detection aiming-side micro mechanical vibrator 112 are completely the same. A mass detection method using the above will be described.

  First, the detected mass body M having an extremely small mass is attached to the detected-side micro mechanical vibrator 111 of the mass detecting means 110.

  Then, the AC power supply 120 applies the detection-side applied AC voltage V (AC-T) between the detection-side counter electrode Et and the ground electrode Eb while sweeping the frequency, and the detection-sight-side counter electrode Es and the ground. A detection aiming side applied AC voltage V (AC-S) is applied to the electrode Eb while sweeping the frequency.

Then, by irradiating the measurement light from the optical heterodyne microvibration measurement device 130, the detection-side micromechanical vibrator vibration information I (v-T) of the detection-side micromechanical vibrator 111 is acquired, and the vibration such as the frequency spectrum is obtained. Convert to information Iv.
At this time, if the detected mass M is attached to the detected micro mechanical vibrator 111, the second vibration mode appears in addition to the first vibration mode.

  Then, with respect to the obtained vibration information Iv, the control amount C is calculated so that the resonance frequency control means 160 cancels the second vibration mode.

The detected side DC power supply 140 is connected to the resonance frequency control means 160.
Then, the detected side DC power supply 140 applies the detected side applied DC voltage V (DC-T) between the detected side counter electrode Et and the ground electrode Eb according to the control amount C.
As a result, a static electrostatic attractive force F (sT) acts between the detected micromechanical vibrator 111 and the detected counter electrode terminal 114.

When a static electrostatic attraction force F (sT) is applied to the detected-side micromechanical vibrator 111, a static restoring force is applied to the detected-side micromechanical oscillator 111, and the detected-side micromechanical oscillator 111 is unique. The frequency changes.
Thereby, the frequency spectrum of the to-be-detected micromechanical vibrator 111 changes, and only the first vibration mode appears.

  At this time, the detected-side applied DC voltage amount I (V) of the detected-side DC power supply 140 applied to make the resonant frequency of the detected-side micromechanical vibrator 111 coincide with the resonant frequency of the detected aiming-side micromechanical vibrator 112. -DC), the mass calculation means 170 calculates the mass of the detected mass M and completes the detection operation.

The operation of the ultra-small mass detection apparatus 100 described above is an operation in a state in which the physical properties and dimensions of the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 completely coincide with each other. The physical properties and dimensions of the side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 do not match.
Therefore, a case where the physical properties and dimensions of the detected micromechanical vibrator 111 and the detection aiming micromechanical vibrator 112 do not completely match will be described below.

When the physical properties and dimensions of the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 do not completely match, the natural vibrations of the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 The numbers do not match.
That is, in this case, not only the first vibration mode but also the second vibration mode appears although the detected mass body M is not attached to the detected-side micro mechanical vibrator 111.

Therefore, before the detected mass body M is attached to the detected-side micro mechanical vibrator 111, it is necessary to perform an initial setting so that only the first vibration mode appears.
For this reason, in the ultra-small mass detection device 100 of the present embodiment, at the initial setting before mass detection, the resonance frequencies of the detected micro-mechanical transducer 111 and the detection-target micro-mechanical transducer 112 are corrected and matched. For this purpose, an initial adjustment DC power supply 150 is used.

  Therefore, in the ultra-small mass detection apparatus 100 of the present embodiment, by using the initial adjustment DC power supply 150, a DC voltage is applied between the detection aiming-side counter electrode Es and the earth electrode Eb, thereby detecting the detection aiming side. A static electrostatic attractive force F (sS) acts between the micro mechanical vibrator 112 and the detection aiming-side counter electrode terminal 115, and the restoring force applied to the detection aiming micro-mechanical vibrator 112 is increased. Errors in physical properties and dimensions of the micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 are corrected.

  The ultra-small mass detection apparatus 100 according to one embodiment of the present invention thus obtained includes the mass detection means 110, the AC power supply 120, the optical heterodyne micro vibration measurement apparatus 130, the detected DC power supply 140, and the initial adjustment. DC power supply 150, resonance frequency control means 160, and mass calculation means 170 are provided, so that the mass calculation means 170 calculates the mass of the detected mass M based on the DC voltage applied by the detected DC power supply 140. Can be calculated.

  Then, the detected micro mechanical vibrator 111 and the detection aiming micro mechanical vibrator 112 of the mass detecting unit 110 are opposed to the ground electrode Eb formed on the insulating layer on the silicon substrate and the ground electrode Eb. Between the detected side counter electrode Et and the detection aiming side counter electrode Es formed on the insulating layer I, they are arranged so as to be capable of minute vibration, respectively, and the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 are The detection-side counter electrode terminal 114 and the detection aiming-side counter electrode terminal 115 that are cantilevered and arranged opposite to each other in the same cross-sectional shape protrude from the detection-side counter electrode Et and the detection aiming-side counter electrode Es, respectively. The resonance frequency of each of the detected side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112 can be controlled separately. It is possible to detect the mass of the restoring force is reliably generated by the detection mass body M by the small vibrations or electrostatic attraction More ultrahigh precision.

  Further, an initial adjustment DC power source 150 that corrects and matches the resonance frequencies of the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 at the time of initial setting before mass detection is provided by the mass detection unit 110. By being connected so as to apply an electrostatic attractive force to at least one of the detection side micro mechanical vibrator 111 and the detection aiming side micro mechanical vibrator 112, the detected side micro mechanical vibrator 111 of the mass detection unit 110. In addition, an electrostatic attractive force is generated in at least one of the detection aiming-side micromechanical vibrator 112 and the detection-side micromechanical vibrator 111 and the detection aiming-side micromechanical vibrator 112 operate at the initial setting before mass detection. Since the error can be corrected, the initial setting work before mass detection can be reduced, and the mass of the detected mass M can be detected with ultra-high accuracy. It is enormous.

DESCRIPTION OF SYMBOLS 100 ... Ultra-small mass detection apparatus 110 ... Mass detection means 111 ... Detected side micro mechanical vibrator 111a ... Detected side micro mechanical vibrator free end 112 ... Detection sighting side micro machine Vibrator 112a ... Detection sight side micro mechanical vibrator free end 113 ... Bridging connector 114 ... Detected side counter electrode terminal 115 ... Detection sight side counter electrode terminal 120 ... AC power supply (AC Voltage application means)
130 ... Optical heterodyne microvibration measuring device (microvibration measuring means)
140 ... Detected side DC power supply (Detected side DC voltage application means)
150 ... DC power supply for initial adjustment (DC voltage application means for initial adjustment)
160 ・ ・ ・ Resonance frequency control means 170 ・ ・ ・ Mass calculation means C ・ ・ ・ Control amount Eb ・ ・ ・ Earth electrode Et ・ ・ ・ Detected counter electrode Es ・ ・ ・ Detection aiming counter electrode F (dT), F (dS) ... Periodic electrostatic attraction F (sT), F (sS) ... Static electrostatic attraction L1 ... Beam free end side length L2 ... Beam base end side length L3 ... Beam protrusion length S1, S11, S12, S13, S2 ... Silicon layer M ... Mass to be detected I ... Insulating layer Iv ... Vibration information I (V-DC) ... Detected-side applied DC voltage amount I (v-T) ... detected-side micromechanical vibrator vibration information I (v-S) ... detection aiming-side micromechanical vibrator vibration information V (AC-T)・ ・ Detected side applied AC voltage V (DC-T) ・ ・ ・ Detected side applied DC voltage V (AC-S) ・ ・ ・ Detected Aiming side applied AC voltage V (DC-S) ··· detect sight side applied DC voltage

Claims (6)

A cantilever-like micromechanical vibrator in the form of a cantilever that vibrates integrally with the mass to be detected and a cantilever-like micromechanical vibration in the form of a cantilever that vibrates separately in parallel with the micromachine vibrator to be detected The detection-side micromechanical transducer and the detection-target-side micromechanical transducer are connected to each other by cross-linking at the intermediate connection portion of the beam, the detection-side micromechanical transducer, and the detection-target-side micromechanical transducer. A mass detection means having a bridging connector that vibrates in a state;
AC voltage applying means for exciting the detected micromechanical vibrator and the detection aiming micromechanical vibrator of the mass detecting means;
Micro-vibration measuring means for measuring a resonance frequency of micro-vibration generated in each of the detected micro-mechanical vibrator and the detection aiming-side micro mechanical vibrator of the mass detecting means;
Detected side DC voltage applying means for generating electrostatic attraction on the detected side micro mechanical vibrator of the mass detecting means,
Resonance frequency control for controlling the DC voltage of the detected DC voltage applying means to match the resonant frequency of the detected micromechanical vibrator measured by the microvibration measuring means with the resonant frequency of the detecting aiming micromechanical vibrator Means,
An ultra-small mass detector comprising at least mass calculating means for calculating the mass of the detected mass body based on the DC voltage applied by the detected DC voltage applying means.   The detected micro mechanical vibrator and the detection aiming micro mechanical vibrator of the mass detecting means are formed on the insulating layer so as to be opposed to and separated from the ground electrode formed on the insulating layer on the silicon substrate and the ground electrode, respectively. 2. The ultra-small mass detection device according to claim 1, wherein the ultra-small mass detection device is arranged so as to be capable of minute vibration between the detection-side counter electrode and the detection aiming-side counter electrode.   The length of the beam free end from the free end portion of the detected side micro mechanical vibrator and the detection aiming side micro mechanical vibrator to the beam intermediate connection portion with the bridge connector is determined by the detected side micro mechanical vibrator and the detection. 3. The ultra-fine structure according to claim 1, wherein the length is longer than the length of the beam base end side from the ground electrode connecting portion of the aiming side micro mechanical vibrator to the beam intermediate connecting portion with the bridge connector. Mass detector.   The detection-side counter electrode terminal and the detection-side counter electrode terminal in the form of a cantilever arranged opposite to each other in the same cross-sectional shape as the detection-side micro-mechanical vibrator and detection-sight-side micro-mechanical vibrator of the mass detection means are The ultra-small mass detector according to any one of claims 1 to 3, wherein each of the ultra-small mass detectors protrudes from the detection side counter electrode and the detection aiming side counter electrode.   The beam free end side lengths of the detected side micro mechanical vibrator and the detection aiming side micro mechanical vibrator are formed to be longer than the beam protruding lengths of the detected side counter electrode terminal and the detection aiming side counter electrode terminal. The ultra-small mass detection apparatus according to claim 4.   DC voltage application means for initial adjustment for correcting and matching the resonance frequencies of the detected micromachine vibrator and the detection aiming micromachine vibrator at the time of initial setting before mass detection is the detected side of the mass detection means. 6. The device according to claim 1, wherein an electrostatic attractive force is applied to at least one of the micro mechanical vibrator and the detection aiming side micro mechanical vibrator. Ultra-small mass detector.