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DESCRIPTION JPWO2017068711

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DESCRIPTION JPWO2017068711
Abstract: MEMS devices with high sensitivity are easily destroyed by strong acoustic and
vibration inputs, so there is a problem that it is difficult to realize a wide dynamic range MEMS
sensor that can handle from low input to high input. The solution means for that is as follows.
The output signal 120 of a less sensitive element having a plurality of elements with different
operating sensitivities allows the more sensitive element to detect in advance the large amplitude
or high speed input of the strength leading to the destruction, and makes the element more
sensitive. On the other hand, the electrical output 124 is provided in the direction that inhibits
the movement of the element to suppress the movement of the vibration system which causes
the more sensitive element to break down.
MEMS device
[0001]
The present invention relates to a MEMS device, and more particularly to a high dynamic range
MEMS device, to a Micro Electro Mechanical Systems (MEMS) device having a thin film type
vibrator and a vibration or acoustic signal detection device using the same.
[0002]
In recent years, the effectiveness of detecting characteristic vibration waveforms or acoustic
signals in many fields, such as failure prediction of mechanical devices, detection of natural
disaster precursors, resource exploration, etc., has been examined, and high sensitivity for this
application Sensing system is required.
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As a sensor used for such a system, a MEMS type sensor which can mass-produce a highprecision sensor inexpensively by applying semiconductor manufacturing technology has been
developed.
[0003]
There are various operation principles and structures of the MEMS type sensor, but the MEMS
type sensor provided with a thin film type vibrator (membrane) is enhanced in sensitivity by
increasing the thickness of the vibrator and high frequency of the detection vibration frequency
Is relatively easy.
[0004]
When the sensor sensitivity is enhanced by thinning the vibrator, the amplitude of the vibrator
becomes excessive when a strong signal is input unexpectedly, and the possibility of breakage is
increased.
In order to prevent this, a method of utilizing elastic deformation of a flexible substrate holding a
sensor chip (Patent Document 1), a method of providing a mechanical stopper (Patent
Documents 2 and 3), a method by electrical means (Patent Document 4) , 5) is disclosed.
[0005]
JP-A-5-164775 JP-A-2008-30182 JP Patent No. 4373994 JP-A-2014-153136 JP-A-2014153363
[0006]
When the sensitivity of the sensor is increased and the above-described destruction prevention
measures are implemented, there arises a problem that the signal can not be accurately detected
even if the sensor does not break when a strong signal is input.
In the configuration described in Patent Document 1, the signal waveform of the sensor is
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distorted because the substrate is elastically deformed by the strong signal input. In the
configurations described in Patent Documents 2 and 3, when the diaphragm is mechanically
pressed, signal detection becomes impossible. Further, in the configuration described in Patent
Document 4, accurate signal detection also becomes difficult because signals of opposite phases
are electrically added in order to suppress movement of the diaphragm. In the configuration
described in Patent Document 5, changing the stiffness of the spring by applying a spring
softening voltage is used as a protection means, but in this method, the stiffness changing means
by voltage application is applied to a part of the integrated spring. There is a problem that the
range of sensitivity change is small because of only giving, and the design of each operation
mode with different sensitivity can not be optimized.
[0007]
An object of the present invention is to provide a MEMS type sensor that enables accurate signal
measurement with high sensitivity and without being destroyed at the time of strong signal input.
[0008]
The above and other objects and novel features of the present invention will be apparent from
the description of the present specification and the accompanying drawings.
[0009]
The outline of typical ones of the inventions disclosed in the present application will be briefly
described as follows.
[0010]
The MEMS type sensor according to the present invention has a configuration in which a
plurality of MEMS elements having different sensor sensitivities are integrated.
For example, in the case of using a membrane type MEMS element, the sensitivity can be
enhanced by means such as reducing the thickness of the membrane or widening the distance
between the fixing portions for holding the membrane.
Conversely, it is possible to increase the resistance to breakage (reduce the sensitivity) by
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increasing the thickness of the membrane, adding a reinforcing beam structure to the membrane,
or narrowing the distance between the fixed parts holding the membrane. is there.
In general, in the MEMS manufacturing process to which the silicon integrated circuit
manufacturing process is applied, the fabrication of the MEMS elements as described above is
possible in a single wafer process. Therefore, it is easy to fabricate a plurality of MEMS elements
on a single silicon wafer as described above. Note that the present invention does not exclude a
method of integrating a plurality of types of MEMS elements manufactured by different wafer
processes in the mounting stage.
[0011]
In the MEMS type sensor in which a plurality of MEMS elements are integrated as described
above, means for increasing sensitivity and resistance to breakage will be described. Here, the
case where two types of MEMS elements are integrated with high sensitivity and low sensitivity
will be described. It goes without saying that combining three or more types of MEMS elements
is also possible in the same manner.
[0012]
The two types of MEMS elements independently detect signals. When the signal input is small,
high sensitivity characteristics are realized by mainly using the output signal of the high
sensitivity element. At the same time, the signal detection operation is also performed in the low
sensitivity element, and the trigger signal is generated promptly when the low sensitivity element
detects a signal input slightly smaller than the high sensitivity element causing a risk of
destruction. Let The trigger signal is connected to the high sensitivity element, and a constant DC
voltage is applied to the electrode of the high sensitivity element in response to the trigger signal
to apply a constant force to the high sensitivity element membrane, and the external force is
high. It acts to protect the membrane against vibrational input.
[0013]
When the signal input drops again to such an extent that the high sensitivity element does not
break down, the trigger signal is quickly released. As for the signal output from the MEMS
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sensor, the output signal of the low sensitivity element is adopted in the time zone in which the
trigger signal is generated, and the output signal of the high sensitivity element is adopted in the
other time zones. Signal synthesis is performed by using an electronic circuit. The electronic
circuit processing described above can be realized in both analog circuits and digital circuits.
[0014]
The effects obtained by typical ones of the inventions disclosed in the present application will be
briefly described as follows.
[0015]
According to the MEMS sensor according to the present invention, high sensitivity and high
accuracy signal detection becomes possible by the high sensitivity MEMS element in minute
signal input, and it is powerful (or excessive).
same as below. The low sensitivity MEMS element enables signal detection at the signal input. In
the case of further strong signal input, a protective means for the highly sensitive MEMS element
is provided. This enables signal detection with a wide dynamic range that can not be realized
with conventional single MEMS elements, from minute signals to strong signals.
[0016]
It is a principal part sectional view and a circuit diagram symbol of a MEMS sensor concerning
Example 1 of the present invention. It is a time-series graph which shows the operation state of
the MEMS sensor concerning Example 1 of the present invention. It is a flow chart explaining
operation of a MEMS sensor concerning Example 1 of the present invention. It is a circuit
diagram of a MEMS sensor concerning Example 1 of the present invention. It is a circuit diagram
of a MEMS sensor concerning Example 2 of the present invention. It is explanatory drawing of
the switch circuit which concerns on Example 3 of this invention. It is principal part sectional
drawing of the transistor used for the switch circuit which concerns on Example 3 of this
invention. It is a circuit diagram of a MEMS sensor concerning Example 4 of the present
invention. It is a graph which shows the frequency characteristic of the high sensitivity element
concerning the Example 5 of this invention, and a low sensitivity element. It is principal part
sectional drawing explaining the mechanical protection of the high sensitivity element which
concerns on Example 6 of this invention. It is principal part sectional drawing of a MEMS sensor
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containing the Helmholtz-type acoustic filter which concerns on Example 7 of this invention.
[0017]
In the following embodiments, when it is necessary for the sake of convenience, it will be
described by dividing into a plurality of sections or embodiments, but they are not unrelated to
each other unless specifically stated otherwise, one is the other And some or all of the variations,
details, and supplementary explanations.
[0018]
Further, in the following embodiments, when referring to the number of elements (including the
number, numerical value, quantity, range, etc.), it is particularly pronounced and clearly limited
to a specific number in principle. It is not limited to the specific number except for the number,
and may be more or less than the specific number.
[0019]
Furthermore, in the following embodiments, the constituent elements (including element steps
and the like) are not necessarily essential unless explicitly stated or considered to be obviously
essential in principle. Needless to say.
[0020]
Similarly, in the following embodiments, when referring to the shape, positional relationship, etc.
of components etc., unless specifically stated otherwise and in principle not considered otherwise
in principle, etc., It includes those that are similar or similar to the shape etc.
The same applies to the above numerical values and ranges.
[0021]
Further, in all the drawings for describing the embodiments, the same reference numeral is
attached to the same member in principle, and the repetitive description thereof will be omitted.
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In order to make the drawings easy to understand, hatching may be attached even to a plan view.
[0022]
A MEMS sensor according to a first embodiment of the present invention will be described with
reference to the drawings.
FIG. 1 is a cross-sectional view of an essential part of the MEMS sensor in the first embodiment.
To form a capacitive MEMS device using a standard silicon CMOS integrated circuit fabrication
process, as shown in FIG. 1 (a), forming a groove 102 on a silicon substrate 101, lower electrode
to the bottom of the groove A membrane is formed on the upper side of the groove, and the
formation of 103. Here, the membrane is composed of two types of film thickness, and comprises
a membrane 106 corresponding to the high sensitivity element 104 and a membrane 107
corresponding to the low sensitivity element 105. An upper electrode 108 is formed on a portion
of the upper surface of each of the membrane 106 and the membrane 107 so as to be opposed
to the lower electrode 103. Here, for example, a tungsten film is used for the lower electrode
103, a polycrystalline silicon film is used for the membranes 106 and 107, and an aluminum film
is used for the upper electrode 108, for example. Note that the lead wires from the lower
electrode 103 and the upper electrode 107 or the contact portions leading thereto are omitted in
this cross-sectional view.
[0023]
The high sensitivity element 104 and the low sensitivity element 105 do not necessarily have to
be manufactured in a single integrated circuit manufacturing wafer process. As shown in FIG. 1B,
chips of corresponding elements may be cut out from a plurality of wafers on which MEMS
elements manufactured by different processes are mounted, and these may be mounted on a
mounting substrate 109.
[0024]
If the above-mentioned MEMS element is described by the symbol (symbol) of a circuit diagram,
it will be like FIG.1 (c) and (d). The high sensitivity element 104 has a lower electrode terminal
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110 and an upper electrode terminal 111, and the low sensitivity element 105 has a lower
electrode terminal 112 and an upper electrode terminal 113. In the usual case, the lower
electrode terminals 110 and 112 are often grounded, so the ground symbol is used in FIG. 1 (c).
It is also possible to use the high sensitivity element 104 and the low sensitivity element 105 in a
floating state regardless of the description of this figure.
[0025]
The operation of the MEMS sensor according to the first embodiment of the present invention
will be described with reference to FIG. 2 and FIG. In FIG. 2, the input signal waveform 120 is the
horizontal axis (this horizontal axis is the time axis). It is shown in the graph of the time 121 of
and the amplitude 122 of the vertical axis. In the figure, the dashed dotted line indicates the
trigger level 123 which is set to a value slightly smaller than the amplitude at which the high
sensitivity element 104 may break down. Here, the trigger level of the positive potential is
defined as 123a, and the trigger level of the negative potential is defined as 123b. In the figure,
the signal input exceeding the trigger level 123 occurs over two time zones. At this time, the
electronic circuit connected to the low sensitivity element 105 quickly generates a trigger signal.
In response to this, the high sensitivity element 104 generates a high sensitivity element
protection voltage 124 as shown in FIG. The above operation is shown in the flowchart of FIG. In
the normal state, it is measured by the high sensitivity element 104, and the absolute value of the
output voltage is equal to or higher than the trigger level 123 or lower than the trigger level 123
constantly or at a constant cycle in the low sensitivity element 105. It is judged whether or not it
is. When this determination is YES, that is, when the absolute value of the output voltage is less
than the trigger level 123, the signal of the low sensitivity element 105 is output, and when NO,
that is, the absolute value of the output voltage is more than the trigger level 123 If so, the signal
of the high sensitivity element 104 is processed to be output.
[0026]
Next, the operation of the electronic circuit will be described with reference to FIG. Although FIG.
4 is divided into (a), (b) and (c), the terminals with the same name are connected to each other,
and constitute one circuit as a whole. The upper electrode terminal 113 of the low sensitivity
element 105 is connected to the input terminal 131 of the low sensitivity element capacitancevoltage converter 130 shown in FIG. 4A, and the signal of the low sensitivity element 105 is an
analog signal output of the low sensitivity element. It is converted and output as 132. This signal
is simultaneously connected to the positive voltage comparator 133 and the negative voltage
comparator 134. A positive reference voltage 135 and a negative reference voltage 136 are
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applied to these comparators, respectively. These reference voltages can be adjusted, for
example, to have an arbitrary reference voltage value after element fabrication depending on the
breakdown resistance of the high sensitivity element 104. Therefore, even if some characteristic
variations occur in the manufacturing process, it can be corrected by this function. The outputs
of comparators 133 and 134 generate trigger signal 138 via OR circuit 137. The function of the
OR circuit 137 is that it is necessary to generate a trigger signal 138 for the protection function
for the sensitive element 104, whether the signal amplitude exceeds the reference voltages 135
to 136 in either positive or negative direction.
[0027]
The trigger signal 138 is led to two sets of switch circuits 139 and 140 as shown in FIG. 4 (b).
Switch circuits 139 and 140 generate constant voltages equal to one another when trigger signal
input 138 is generated. The outputs of the two switch circuits 139 and 140 are led to the
differential input terminal of the high sensitivity device capacitance-voltage converter 141. When
the trigger input 138 is generated, the high sensitivity element analog signal output voltage
value 142 becomes zero because the same voltage is applied to the differential input. On the
other hand, when the trigger signal 138 is not generated, the output of the switch circuit 139 is
fixed to the ground potential, and the output terminal of the switch circuit 140 is in the open
state. The output terminal 142 is connected to the output terminal 111 of the high sensitivity
element 104. Since the output terminal of switch circuit 140 is in the open state and the
differential input terminal of capacitor-voltage converter 141 for the high sensitivity element is
also in the high impedance state, the output of high sensitivity element 104 is for loss without
loss Guided to a capacitance-to-voltage converter 141, an accurate sensitive element analog
signal output 142 is obtained.
[0028]
Next, as shown in FIG. 4C, the low sensitivity element analog signal output 132 and the high
sensitivity element analog signal output 142 are independently converted to digital signals by
the low sensitivity element AD converter 143 and the high sensitivity element AD converter 144,
respectively. It is converted. These digital outputs are led to the digital signal processor 145, and
in response to the trigger input 138, the signals of a plurality of elements having different
sensitivities are synthesized to correspond to the flow chart shown in FIG.
[0029]
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The total delay time of the capacitance-voltage converter 130, the positive voltage comparator
133, the negative voltage comparator 134, the OR circuit 137, and the switch circuit 140 is the
inverse of the maximum frequency component of the signal handled by the MEMS sensor. Design
to less than half of. This is necessary to prevent the high sensitivity element 104 from being
destroyed by a high speed signal input that does not meet the response time of the circuit.
[0030]
This embodiment shows another configuration of the electronic circuit shown in the first
embodiment. Descriptions of common parts are omitted.
[0031]
The output terminal 113 of the low sensitivity element 105 is connected to the low sensitivity
element AD converter 143 from the low sensitivity element capacitance-voltage converter 130
shown in FIG. 5A and converted into a digital signal. Further, the low sensitivity element digital
signal processor 147 corrects the frequency response characteristic of the low sensitivity
element and performs noise removal processing to obtain the low sensitivity element digital
output 148, and further to the digital signal processor 145 shown in FIG. It is led. In this
processor, a logic control signal 149 corresponding to the trigger signal 138 shown in the first
embodiment is obtained by digital processing.
[0032]
The circuit configuration shown in FIG. 5B has many points in common with FIG. 4B, and the
trigger signal 138 may be replaced with the logic control signal 149. The circuit configuration of
the high sensitivity device capacitance-voltage converter 141 and the subsequent circuits is the
same as that for the low sensitivity device in FIG. 5A, and passes through the high sensitivity
device AD converter 144 and the high sensitivity device digital signal processor 150. Thus, a
high sensitivity element digital output 151 is obtained. This output 151 is led to the digital signal
processor 145 of FIG. 5C to obtain the combined output 146 in the same manner as in the first
embodiment. The request for the delay time of this circuit is also the same as in the first
embodiment.
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[0033]
The present example illustrates one mode of the switch circuit 140 shown in the first example
and the second example. When the trigger signal 138 is not generated, the output terminal of the
switch circuit needs to be in the open state. This requirement can be easily realized by using the
p-channel MOSFET 152 in the output stage of the switch circuit. The power supply voltage VDD
is applied to the source electrode (S) of the p-channel MOSFET 152, and the trigger signal 138 or
a signal obtained by appropriately converting the signal level is applied to the gate electrode.
First, since the p-channel MOSFET 152 is turned on in the state where the trigger signal 138 is
generated, a voltage substantially equivalent to the power supply voltage VDD is supplied to the
drain electrode (D) via the upper electrode terminal 111 and a high sensitivity element Is applied
to the upper electrode 108 of the In the normal case, since the lower electrode 103 is at the
ground potential, attraction of the membrane 106 to the lower electrode 103 is generated by
voltage application to suppress vibration of the membrane, thereby preventing breakage. It is
needless to say that an appropriate voltage is applied so that this attraction does not cause
stiction (sticking of the membrane to the lower electrode).
[0034]
Next, the p-channel MOSFET 152 is turned off when the trigger signal 138 is not generated. At
this time, the upper electrode terminal 111 viewed from the upper electrode 108 is in an open
state in terms of direct current. However, since this MOSFET also serves as a capacitive load for
the high sensitivity element 104, the sensitivity is reduced unless the capacitive load is reduced.
One means for solving this is illustrated in FIG. In a normal MOSFET, as shown in FIG. 7A, the
capacitance between the gate electrode 160 and the drain diffusion layer 161 is relatively large.
In particular, in a conventional MOSFET, the diffusion layer 161 has a so-called diffusion layer
overlap 162 structure in which the diffusion layer 161 extends to the lower part of the gate
electrode. Therefore, the gate-drain capacitance is increased. In order to solve this, as shown in
FIG. 7B, the load capacity as viewed from the high sensitivity element 104 is significantly
reduced by the diffusion layer non-overlap 163 structure. Such a transistor can be easily
manufactured by using an offset sidewall 164 in contact with the gate electrode 160.
[0035]
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This embodiment is another embodiment of acquisition of the trigger signal 138 shown in
Embodiment 1 and is illustrated with reference to FIG. The circuit diagram of FIG. 8 shares many
points in common with the circuit diagram of FIG. 4A, and a differentiating circuit 170 is inserted
between the output of the low sensitivity element capacitor-to-voltage converter 130 and the
positive voltage comparator 133. There is. In the circuit of the first embodiment, when a signal
with a very sharp rise and a large amplitude is input, there is also a possibility that the risk of
breakage of the high sensitivity element may increase despite the design conditions shown in the
first embodiment. Therefore, the risk can be mitigated by detecting the sharp rise of the signal by
the differentiation circuit as shown in this embodiment and generating the trigger signal 138.
When the trigger output 138 is generated, it is also effective to configure a 4-input OR circuit by
combining not only the OR circuit shown in FIG. 8 but also the OR circuit shown in FIG.
[0036]
Furthermore, in the case of digital processing of the second embodiment, the logic control signal
149 can be more accurately acquired by differentiating the digital signal.
[0037]
The frequency characteristics of the high sensitivity and low sensitivity elements which are
desirable from the viewpoint of the performance function of the MEMS sensor shown in the first
and second embodiments will be described with reference to FIG.
In general, a membrane type MEMS device has a device-specific self-resonant frequency, and the
response characteristic (sensitivity) sharply drops at frequencies higher than this. In the MEMS
sensor of the present invention, the output of the low sensitivity element is configured to obtain a
trigger output for preventing breakage of the high sensitivity element. Therefore, it is required
that the frequency band of the low sensitivity element be wider. FIG. 9 exemplifies the sensitivity
characteristic 180 of the high sensitivity element and the sensitivity characteristic 181 of the low
sensitivity element. This graph shows the relative value of the output signal level of each element
to a fixed acoustic vibration input level. Here, both sensitivities differ by about 20 dB, that is, by
about 10 times. The frequency to be the self resonance point 182 of the high sensitivity element
is lower than the frequency to be the self resonance point 183 of the low sensitivity element.
[0038]
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In the second embodiment, digital signal processors 147 and 150 perform correction of
frequency characteristics, that is, removal of peak characteristics. The dotted line in FIG. 9
indicates the frequency characteristic 184 corrected by the digital processing. Needless to say,
the same processing can be performed by the digital signal processor 145 also in the first
embodiment.
[0039]
According to the configurations shown in the first to fifth embodiments, it is possible to
effectively destroy the high sensitivity element 104 in a state in which the electronic circuits
connected to the high sensitivity element 104 and the low sensitivity element 105 are energized
and operated normally. Can be prevented. However, in a state where the MEMS sensor is not
functioning, for example, vibration during transportation or installation may destroy the high
sensitivity element. In the present embodiment, means for preventing this destruction will be
described with reference to FIG.
[0040]
First, an easily conceivable method is to always generate a trigger signal 138 in a nonfunctioning state of the MEMS sensor, that is, when measurement is not performed, and to
continue applying a voltage to the upper electrode 108 of the high sensitivity element 104. is
there. This may be provided with a circuit that automatically generates a trigger signal 138 when
the measurement of the MEMS sensor is stopped. In addition, at the time of transportation or the
like, power may be constantly supplied by a backup battery.
[0041]
As another method shown in the present embodiment as another method, as shown in FIG. 10A,
the pressing plate 190 is installed on the upper electrode 108 of the high sensitivity element and
driven by the piezoelectric actuator 191 to hold the pressing plate 190. By contacting the upper
electrode 108, the membrane is protected from breakage. At this time, driving of the piezo
actuator 191 is performed through the control circuit 192 operated by power supply from the
backup battery 193. As shown in FIGS. 10 (b) and 10 (c), in the specific operation, the piezo
actuator 191 expands to bring the pressure plate 190 into contact with the upper electrode 108
at the time of stop. In this case, a piezo actuator of a type that expands when a positive voltage is
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applied may be used. In operation, i.e., in measurement, no voltage is applied to the piezo
actuator 191, and the pressure plate 190 does not inhibit the movement of the upper electrode
108 and the membrane 106.
[0042]
However, in the above method, it is necessary to keep supplying power at the time of shutdown.
In the method illustrated in FIGS. 10 (d) and 10 (e), a piezo actuator of a type that contracts when
a positive voltage is applied is used. Then, the positional relationship between the pressure plate
190 and the upper electrode 108 is adjusted so that the pressure plate 190 contacts the upper
electrode 108 in a state where power is not supplied to the piezoelectric actuator. In such a state,
the power supply is supplied to the piezoelectric actuator during operation to contract, and the
pressure plate 190 does not inhibit the movement of the upper electrode 108 and the membrane
106.
[0043]
According to still another method, as illustrated in FIGS. 10 (f) and 10 (g), a piezo actuator 191 of
a type that expands when a positive voltage is applied is used to press the plate 108 (and a
member for holding the same). ) And the substrate 101. Further, the positional relationship
between the pressure plate 190 and the upper electrode 108 is adjusted so that the pressure
plate 190 contacts the upper electrode 108 in a state where power is not supplied to the
piezoelectric actuator 191. In such a state, the power supply is supplied to the piezo actuator
during operation to be extended, and the pressure plate 190 does not inhibit the movement of
the upper electrode 108 and the membrane 106.
[0044]
In any of the above methods, it is possible to take measures to prevent the breakage of the high
sensitivity element at the time of stopping without impairing the function as the MEMS sensor
described in the first to fifth embodiments.
[0045]
According to the configurations shown in the first to fifth embodiments, even when a high
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frequency and large amplitude signal is input to the MEMS sensor, accurate measurement can be
performed while preventing destruction of the high sensitivity element.
In some applications, it may be desirable that the acoustic signal in a particular frequency range
is very strong and it is desirable to attenuate it in advance and measure it with a MEMS sensor. In
the present embodiment, a configuration corresponding to such a case will be described with
reference to FIG. Helmholtz resonators are used to attenuate acoustic signals in a specific
frequency range. The configuration shown in FIG. 11 is intended to attenuate signals of two types
of frequency ranges, and includes two types of Helmholtz resonators 200 and 201 having
different resonance frequencies. A cylindrical acoustic conduit is provided in the sensor cavity
202 surrounding the high sensitivity element 104 and the low sensitivity element 105, and an
acoustic signal for measurement is input from an acoustic signal inlet 203 on the upper side.
Then, when passing through the acoustic conduit, the Helmholtz resonators 200 and 201
provided on the inner wall attenuate the acoustic signal of the specific frequency range and
prevent the acoustic signal of excessive amplitude from being input to the MEMS sensor. Can.
Since the attenuation characteristics can be measured in advance, it is possible to correct the
frequency characteristics as shown in the second and fifth embodiments without any problem.
[0046]
101 silicon substrate 102 groove 103 lower electrode 104 high sensitivity element 105 low
sensitivity element 106 membrane corresponding to high sensitivity element 107 membrane
corresponding to low sensitivity element 108 upper electrode 109 mounting substrate 110 high
Lower electrode terminal of sensitivity element 111: upper electrode terminal of high sensitivity
element 112: lower electrode terminal of low sensitivity element 113: upper electrode terminal
of low sensitivity element 120: input signal waveform 121: time 122: amplitude 123: trigger
level 124 ... High sensitivity element protection voltage 130 ... Capacitance-voltage converter for
low sensitivity element 131 ... Input terminal of capacitance-voltage converter for low sensitivity
element 132 ... Low sensitivity element analog signal output 133 ... Comparator for positive
voltage 134 ... For negative voltage Comparator 135 ... positive reference voltage 136 ... negative
reference voltage 137 ... OR circuit 138 ... trigger signal 139 Switch circuit 140 ... Switch circuit
141 ... Capacitance-voltage converter for high sensitivity element 142 ... High sensitivity element
analog signal output 143 ... AD converter for low sensitivity element 144 ... AD converter for high
sensitivity element 145 ... Digital signal processing processor 146 ... Synthesis Output 147 Digital
signal processor for low sensitivity element 148 Low sensitivity element digital output 149 Logic
control signal 150 Digital signal processor for high sensitivity element 151 High sensitivity
element digital output 152 p channel MOSFET 160 Gate electrode 161 drain Diffusion layer 162:
Diffusion layer overlap 163: Diffusion layer non overlap 164: Offset sidewall 170: Differential
circuit 180: Sensitivity characteristics of high sensitivity element 181: Sensitivity characteristics
of low sensitivity element 182: Self-resonant point of high sensitivity element 18 3 Self-
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resonance point of low sensitivity element 184 Frequency characteristic corrected by digital
processing 190 Suppression plate 191 Piezo actuator 192 Control circuit 193 Backup battery
200 Helmholtz resonator 201 Helmholtz resonator 202 Sensor cavity 203 ... Sound signal
entrance
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