JP2014187105A - Apparatus and method for inspecting variable capacitance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for inspecting a variable capacitance element that inspects whether a sticking phenomenon due to a factor other than charge-up occurs.SOLUTION: A computation unit 202 repeats application of a voltage in a triangular wave shape a predetermined number of times to measure the variation of the difference value between a pull-in voltage and a pull-out voltage. A good element shows little variation in the pull-in voltage and the pull-out voltage even when the application of a voltage is repeated. In contrast, a bad element shows a large decrease in the pull-out voltage in comparison with the pull-in voltage when the application of a voltage is repeated. Therefore, the computation unit 202 determines that an element which shows no variation in the difference value between the pull-in voltage and the pull-out voltage is good and an element for which the variation of the difference value between the pull-in voltage and the pull-out voltage is equal to a reference value or greater when the application of a voltage is repeated is bad.

Description

  The present invention relates to an inspection apparatus, and more particularly to an inspection apparatus for a variable capacitance element that can change an RF (Radio Frequency) capacity by using an electrostatically driven actuator that is driven by an electrostatic force.

  Patent Document 1 shows an example of a variable capacitance element including an electrostatic drive type actuator using MEMS (Micro Electro Mechanical Systems).

FIG. 1 is a diagram illustrating a configuration example of a conventional electrostatic drive actuator 101 that forms a variable capacitance element as disclosed in Patent Document 1. In FIG.
As shown in FIG. 1, the electrostatic drive actuator 101 includes a semiconductor substrate 102, an elastic member 103, a lower drive electrode 104A, an upper drive electrode 104B, a lower capacitive electrode 105A, and an upper capacitive electrode 105B. And a film 106.

  The elastic member 103 is a movable part made of an insulating material, and one end is fixed to the semiconductor substrate 102. The lower drive electrode 104A and the lower capacitor electrode 105A are formed on the semiconductor substrate 102 adjacent to each other. The insulating film 106 is formed so as to cover the lower drive electrode 104A and the lower capacitor electrode 105A. The upper drive electrode 104B is formed on the elastic member 103 so as to face the lower drive electrode 104A. The upper capacitor electrode 105B is formed on the elastic member 103 so as to face the lower capacitor electrode 105A.

  The electrostatic drive type actuator 101 is driven by applying a drive voltage (DC voltage) between the lower drive electrode 104A and the upper drive electrode 104B. Specifically, a drive capacitance is formed between the lower drive electrode 104A and the upper drive electrode 104B by a drive voltage applied between the lower drive electrode 104A and the upper drive electrode 104B. The elastic member 103 is attracted to the semiconductor substrate 102 by the electrostatic attractive force in the drive capacitor, and the upper capacitor electrode 105B contacts the insulating film 106. As a result, a first capacitor is formed between the upper capacitor electrode 105B and the lower capacitor electrode 105A. Further, when the electrostatic drive type actuator 101 is not driven, a gap space is formed between the upper capacitive electrode 105B and the insulating film 106. Therefore, a second capacitor having a capacitance value smaller than that of the first capacitor is formed between the upper capacitor electrode 105B and the lower capacitor electrode 105A. Thus, the electrostatic drive type actuator 101 functions as a variable capacitance element.

  In such an electrostatic drive type actuator, a phenomenon called a sticking phenomenon may occur. Specifically, when the electrostatic drive actuator is driven, when the upper capacitive electrode comes into contact with the insulating film, the upper drive electrode also comes into contact with the insulating film. At this time, a charge may be injected into the insulating film due to a potential difference between the upper drive electrode and the lower drive electrode, and the charge may be trapped in the insulating film, and the insulating film may be charged up (charged). Even if the application of the drive voltage is stopped, the upper drive electrode is attracted to the insulating film due to the charge-up of the insulating film. Due to such factors, the phenomenon in which the elastic member stops moving from the state of being attracted to the semiconductor substrate is the sticking phenomenon. When the sticking phenomenon occurs, the electrostatic drive actuator cannot be controlled, which becomes a problem.

  In view of this, for example, a drive voltage is alternately applied to the upper drive electrode and the lower drive electrode to prevent the insulating film from being charged up.

JP 2001-143595 A

  However, in the variable capacitance element, the sticking phenomenon may occur due to factors other than the charge-up. For example, there may be a case where charging due to repeated physical contact and peeling at the contact point with the insulating film or adhesion force due to surface conditions such as van der Waals force occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a variable capacitance element inspection apparatus for inspecting whether or not a sticking phenomenon due to factors other than charge-up occurs.

  The variable capacitance element inspection apparatus of the present invention includes a fixed electrode, a movable electrode facing the fixed electrode, an insulating layer provided between the fixed electrode and the movable electrode, the fixed electrode, and the movable electrode. An inspection device for inspecting a variable capacitance element comprising: a drive unit that changes capacitance by applying a voltage therebetween; and capacitance measuring means for measuring a change in capacitance of the variable capacitance element; A calculation means for measuring a pull-in voltage that is a voltage at which the electrostatic capacitance shifts to a maximum state, and a pull-out voltage that is a voltage at which the electrostatic capacitance is released from the maximum state; the fixed electrode and the movable electrode A voltage that continuously changes in between is repeatedly applied a predetermined number of times, and the pull-in voltage and the pull-out voltage after the continuously changing voltage is applied and the continuously changing voltage are applied. Based on the amount of variation between the pull-in voltage and the pull-out voltage prior to, characterized by comprising a determination unit to which the variable capacitance element checks whether it is defective element.

  More specifically, the determination unit repeatedly applies a continuously changing voltage a predetermined number of times, and a difference value between the pull-in voltage and the pull-out voltage after the continuously changing voltage is applied, A variable capacitance element having an amount of change between a difference value between the pull-in voltage and the pull-out voltage before the continuously changing voltage is applied is determined to be a defective element.

  When a voltage is repeatedly applied to defective products, the pull-out voltage fluctuates greatly as compared to the pull-in voltage. Therefore, an element in which the difference value between the pull-in voltage and the pull-out voltage does not change even when voltage application is repeated is determined as a non-defective product, and an element in which the change amount in the difference value between the pull-in voltage and the pull-out voltage is equal to or higher than a reference value is determined as a defective product. Thus, it is possible to inspect whether or not the element causes a sticking phenomenon. Note that if sticking due to charge-up occurs, the pull-in voltage and pull-out voltage change in the same manner, so that the difference value does not change depending on the presence or absence of sticking due to charge-up. Therefore, in the inspection apparatus of the present invention, it is possible to accurately inspect whether or not the element causes a sticking phenomenon due to factors other than charge-up.

  According to the present invention, it is possible to inspect whether or not the sticking phenomenon due to factors other than charge-up occurs.

It is a figure explaining the structural example of the conventional electrostatic drive type actuator. It is a figure explaining the structural example of the electrostatic drive type actuator which comprises a variable capacitance element. It is a circuit diagram which shows the structure of a variable capacitance element and an inspection apparatus. It is a figure explaining the time when RF capacity | capacitance is the maximum in a variable capacitance element. It is a figure explaining the time when RF capacity is the minimum in a variable capacity element. It is a figure which shows the relationship between the pull-in voltage in a good quality element, and a pull-out voltage. It is a figure which shows the relationship between the pull-in voltage and pull-out voltage in a defective element. It is a flowchart which shows operation | movement of an inspection apparatus.

  FIG. 2A is a cross-sectional view (XZ plane cross-sectional view) of the electrostatic drive actuator 11 constituting the variable capacitance element 1 according to the present embodiment. FIG. 2B is a perspective view of the movable portion 3 </ b> A constituting the electrostatic drive actuator 11. 2A and 2B, the thickness direction of the movable beam 3 of the electrostatic drive actuator 11 is the Z-axis direction, the main axis direction of the movable beam 3 is the X-axis direction, and the width direction of the movable beam 3 is the same. Is attached with an XYZ axis in a rectangular coordinate form with Y in the Y-axis direction.

  The variable capacitance element 1 includes an electrostatic drive actuator 11. The electrostatic drive actuator 11 includes a housing 2, a movable beam 3, a lower drive electrode 5A, a lower drive electrode 5B, an RF capacitor electrode 6, an upper drive electrode 7A, an upper drive electrode 7B, an upper drive electrode 7C, and a lower equipotential electrode. 8A, a lower equipotential electrode 8B, a lower equipotential electrode 8C, an upper equipotential electrode 9A, an upper equipotential electrode 9B, an upper equipotential electrode 9C, an external connection electrode 10, an insulating film 12A, and an insulating film 12B.

  The housing 2 includes a lower fixed substrate 2A, an upper fixed substrate 2B, and a frame 2C. The housing 2 has a space hermetically sealed inside. The space hermetically sealed inside the housing 2 has a reduced pressure atmosphere (for example, about 1000 Pa).

  Each of the lower fixed substrate 2A and the upper fixed substrate 2B is an insulating substrate made of glass, sapphire, or the like, and has a rectangular shape when viewed in plan. Alternatively, the lower fixed substrate 2A and the upper fixed substrate 2B may be semiconductor substrates made of, for example, silicon.

  The frame 2C is made of a metal such as Cu and has a rectangular ring shape when viewed in plan. The lower fixed substrate 2A and the upper fixed substrate 2B are joined to each other with the frame 2C interposed therebetween. Thereby, the housing | casing 2 is comprised.

  The movable beam 3 is made of a metal such as Cu and is housed inside the housing 2. The movable beam 3 includes a movable part 3A and an anchor part 3B. One end of the movable portion 3A is supported by the anchor portion 3B. The anchor portion 3B is a columnar portion joined to the lower fixed substrate 2A and the upper fixed substrate 2B. The movable portion 3A faces both the lower fixed substrate 2A and the upper fixed substrate 2B with a space therebetween.

  The external connection electrode 10 is formed on the lower surface of the lower fixed substrate 2 </ b> A and is used for mounting the electrostatic drive actuator 11. Each external connection electrode 10 is connected to each electrode inside the housing 2 and the movable beam 3 through a through electrode provided on the lower fixed substrate 2A.

  The movable portion 3A includes a capacitance forming portion 3A1, a capacitance forming portion 3A2, and a capacitance forming portion 3A3 that are thick portions (for example, about 10 μm). The capacitance forming portion 3A1, the capacitance forming portion 3A2, and the capacitance forming portion 3A3 are sequentially arranged from the movable end side (X-axis positive direction side) to the fixed end side (X-axis negative direction side). 3 [mu] m).

  The capacitor forming portion 3A1 is provided with a protruding portion 13A on the surface facing the lower fixed substrate 2A. The capacitor forming portion 3A2 is provided with a protruding portion 13B on the surface facing the lower fixed substrate 2A. The capacitor forming portion 3A3 is provided with a protruding portion 13C on the surface facing the lower fixed substrate 2A.

  The lower drive electrode 5A, the lower drive electrode 5B, the RF capacitor electrode 6, the lower equipotential electrode 8A, the lower equipotential electrode 8B, and the lower equipotential electrode 8C are on the surface of the lower fixed substrate 2A facing the movable beam 3. Is formed.

  The lower drive electrode 5A, the lower drive electrode 5B, the RF capacitor electrode 6, the lower equipotential electrode 8A, the lower equipotential electrode 8B, and the lower equipotential electrode 8C are covered with an insulating film 12A. The insulating film 12A is made of SiN, SiO2, or the like. The insulating film 12A is short-circuited when the lower drive electrode 5A, the lower drive electrode 5B, the RF capacitor electrode 6, the lower equipotential electrode 8A, the lower equipotential electrode 8B, and the lower equipotential electrode 8C are in direct contact with the movable portion 3A. This is provided to prevent this and protect each electrode. However, the insulating film may be provided on each projection (projection 13A, projection 13B, and projection 13C) side.

  The lower drive electrode 5A is provided at a position facing the capacitance forming portion 3A1. The lower drive electrode 5B is provided at a position facing the capacitance forming portion 3A3. The RF capacitor electrode 6 is provided at a position facing the capacitor forming portion 3A2.

  When a DC voltage is applied between the movable part 3A and the lower drive electrode 5A and the lower drive electrode 5B, an electrostatic capacity is formed between the movable part 3A and the lower drive electrode 5A and the lower drive electrode 5B. The movable portion 3A is displaced toward the lower fixed substrate 2A side by electrostatic attraction due to the capacitance. Then, the protruding portion 13A, the protruding portion 13B, and the protruding portion 13C are in contact with the insulating film 12A. For this reason, the distance between the movable portion 3A and the RF capacitive electrode 6 is the shortest, and the RF capacitance formed between the movable portion 3A and the RF capacitive electrode 6 is maximized.

  At this time, regions formed on the lower drive electrode 5A, the lower drive electrode 5B, and the RF capacitor electrode 6 in the insulating film 12A do not come into contact with the movable portion 3A. Therefore, it is possible to prevent the regions formed on the lower drive electrode 5A, the lower drive electrode 5B, and the RF capacitor electrode 6 in the insulating film 12A from being charged up.

  A lower equipotential electrode 8A is provided at a position facing the protrusion 13A, a lower equipotential electrode 8B is provided at a position facing the protrusion 13B, and a position facing the protrusion 13C is A lower equipotential electrode 8C is provided. The lower equipotential electrode 8A, the lower equipotential electrode 8B, and the lower equipotential electrode 8C are electrodes having the same potential as the movable beam 3. The lower equipotential electrode 8A, the lower equipotential electrode 8B, and the lower equipotential electrode 8C are not indispensable structures, but by providing these equipotential electrodes, the potentials between these protrusions and the equipotential electrodes are the same. In the insulating film 12A, it is possible to prevent the regions formed on the lower equipotential electrode 8A, the lower equipotential electrode 8B, and the lower equipotential electrode 8C from being charged up.

  On the other hand, the upper drive electrode 7A, the upper drive electrode 7B, the upper drive electrode 7C, the upper equipotential electrode 9A, the upper equipotential electrode 9B, and the upper equipotential electrode 9C are on the side of the upper fixed substrate 2B facing the movable beam 3. Formed on the surface.

  The upper drive electrode 7A is provided at a position facing the capacitance forming portion 3A1. The upper drive electrode 7B is provided at a position facing the capacitance forming portion 3A2. The upper drive electrode 7C is provided at a position facing the capacitance forming portion 3A3.

  The upper equipotential electrode 9A, the upper equipotential electrode 9B, and the upper equipotential electrode 9C are electrodes having the same potential as that of the movable beam 3. The upper equipotential electrode 9A is provided so as to face both end portions in the X-axis direction of the capacitance forming portion 3A1. The upper equipotential electrode 9B is provided so as to face both end portions in the X-axis direction of the capacitance forming portion 3A2. The upper equipotential electrode 9C is provided so as to face both ends of the capacitance forming portion 3A3 in the X-axis direction.

  In addition, insulating films 12B are provided at both end portions in the X-axis direction of the capacitor forming portion 3A1, both end portions in the X-axis direction of the capacitor forming portion 3A2, and both end portions in the X-axis direction of the capacitor forming portion 3A3. The insulating film 12B is made of SiN, SiO2, or the like. The insulating film 12B is short-circuited when the upper drive electrode 7A, the upper drive electrode 7B, the upper drive electrode 7C, the upper equipotential electrode 9A, the upper equipotential electrode 9B, and the upper equipotential electrode 9C are in direct contact with the movable portion 3A. To prevent that. However, the insulating film may be provided on the upper fixed substrate 2B side so as to cover each electrode.

  When a voltage is applied between the movable part 3A and the upper drive electrode 7A, the upper drive electrode 7B, and the upper drive electrode 7C, the movable part 3A, the upper drive electrode 7A, the upper drive electrode 7B, and the upper drive electrode 7C. A capacitance is formed between the movable portion 3A and the movable portion 3A is displaced to the upper fixed substrate 2B side by electrostatic attraction caused by the capacitance. The insulating film 12B is in contact with the upper equipotential electrode 9A, the upper equipotential electrode 9B, and the upper equipotential electrode 9C. For this reason, the distance between the movable portion 3A and the RF capacitive electrode 6 is the longest, and the RF capacitance formed between the movable portion 3A and the RF capacitive electrode 6 is minimized.

  At this time, the region formed under the upper drive electrode 7A, the upper drive electrode 7B, and the upper drive electrode 7C does not come into contact with the movable portion 3A. As a result, it is possible to prevent the region formed under the upper drive electrode 7A, the upper drive electrode 7B, and the upper drive electrode 7C from being charged up.

  Further, the upper equipotential electrode 9A, the upper equipotential electrode 9B, and the upper equipotential electrode 9C are not indispensable configurations, but by providing these equipotential electrodes, the movable portion 3A and the equipotential electrodes have the same potential. Therefore, it is possible to prevent the regions formed under the upper equipotential electrode 9A, the upper equipotential electrode 9B, and the upper equipotential electrode 9C in the insulating film 12B from being charged up.

  Next, the circuit configuration of the variable capacitance element 1 including the equivalent circuit of the electrostatic drive actuator 11 and the configuration of the inspection device for the variable capacitance element 1 will be described.

  FIG. 3 is a circuit diagram of the variable capacitance element 1 and a block diagram showing a configuration of an inspection apparatus 100 for inspecting the variable capacitance element 1.

  The inspection apparatus 100 is connected to an RF signal input terminal RF-In and an RF signal output terminal RF-OUT of the variable capacitance element 1, and is a network analyzer (corresponding to the capacity measuring means of the present invention) 201 that measures the RF capacity. And an arithmetic unit 202 connected to the network analyzer 201 and the DC power source (V), and a determination unit 203 connected to the arithmetic unit 202.

  The upper drive electrode 7A, the upper drive electrode 7B, and the upper drive electrode 7C are connected to the switch SW via the RF cut resistor R1. The lower drive electrode 5A and the lower drive electrode 5B are connected to the switch SW via the RF cut resistor R2. 3 A of movable parts are connected to DC power supply via RF cut resistance R3. The switch SW selectively connects the RF cut resistor R1 or the RF cut resistor R2 to the DC power source. The RF capacitor electrode 6 is connected to the RF signal input terminal RF-IN, and the movable portion 3A is connected to the RF signal output terminal RF-OUT. A network analyzer 201 is connected to the RF signal input terminal RF-In and the RF signal output terminal RF-OUT. The network analyzer 201 measures the RF capacitance formed between the RF capacitance electrode 6 and the movable portion 3A. The measured RF capacitance value is output to the calculation unit 202.

  The RF cut resistor R1, the RF cut resistor R2, and the RF cut resistor R3 each have a resistance value of, for example, 200 kΩ, and are provided to prevent the RF signal from leaking to the DC power source side.

  FIG. 4 is a diagram illustrating a case where the RF capacitance of the variable capacitance element 1 is maximum. FIG. 4A is a partial enlarged cross-sectional view showing the internal space of the housing 2 in a state where the movable portion 3A is displaced toward the lower fixed substrate 2A. FIG. 4B is a circuit diagram in a state where the movable portion 3A is displaced toward the lower fixed substrate 2A.

  As shown in FIG. 4B, when the switch SW is connected to the RF cut resistor R2, a DC voltage (for example, DC 30V) is applied between the lower drive electrode 5A, the lower drive electrode 5B, and the movable portion 3A. Is done. Then, as shown in FIG. 4A, a capacitance is formed between the lower drive electrode 5A and the lower drive electrode 5B and the movable portion 3A, and the movable portion 3A is generated by electrostatic attraction due to this capacitance. Is displaced toward the lower fixed substrate 2A. As a result, the distance between the movable portion 3A and the RF capacitive electrode 6 is the shortest, and the RF capacitance formed between the movable portion 3A and the RF capacitive electrode 6 is maximized.

  FIG. 5 is a diagram for explaining a case where the RF capacity is minimum. FIG. 5A is a partial enlarged cross-sectional view showing the internal space of the housing 2 in a state where the movable portion 3A is displaced toward the upper fixed substrate 2B. FIG. 5B is a circuit diagram in a state where the movable portion 3A is displaced toward the upper fixed substrate 2B.

  As shown in FIG. 5B, when the switch SW is connected to the RF cut resistor R1, a DC voltage is applied between the upper drive electrode 7A, the upper drive electrode 7B, the upper drive electrode 7C, and the movable portion 3A. (For example, DC30V) is applied. Then, as shown in FIG. 5A, an electrostatic capacity is formed between the upper drive electrode 7A, the upper drive electrode 7B, the upper drive electrode 7C, and the movable portion 3A. The movable part 3A is displaced toward the upper fixed substrate 2B by the electric attractive force. As a result, the distance between the movable portion 3A and the RF capacitive electrode 6 is the longest, and the RF capacitance formed between the movable portion 3A and the RF capacitive electrode 6 is minimized.

  Note that the polarity of the applied voltage is preferably switched at a constant period. By reversing the polarity at a constant period, the insulating film is maintained while maintaining the state where the movable portion 3A is displaced toward the lower fixed substrate 2A or while maintaining the state where the movable portion 3A is displaced toward the upper fixed substrate 2B. By reversing the direction of the electric field acting on 12A and insulating film 12B at a constant period, it is possible to prevent charges from being trapped in insulating film 12A and insulating film 12B, and to prevent sticking phenomenon due to charge-up. Can do.

  However, the sticking phenomenon occurs due to factors other than charge-up. For example, there may be a case where charging due to repeated physical contact and peeling at the contact portion between the insulating film and the movable part and adhesion force due to surface conditions such as van der Waals force occur. Therefore, the inspection apparatus 100 according to the present embodiment inspects whether or not sticking due to factors other than charge-up occurs.

  6 and 7 are diagrams showing an outline of the inspection method, and FIG. 8 is a flowchart of the inspection method. FIG. 6A is a diagram illustrating the relationship between the pull-in voltage and the pull-out voltage. The inspection apparatus 100 according to the present embodiment applies a voltage that continuously changes in a triangular waveform from 0 V to a maximum value (for example, 30 V) between the lower drive electrode 5A and the lower drive electrode 5B and the movable portion 3A. When the applied voltage is gradually increased from 0 V, the movable portion 3A is displaced toward the lower fixed substrate 2A at a predetermined timing and comes into contact with the insulating film 12A, and the RF capacitance is rapidly increased. The applied voltage at the timing when the RF capacitance value suddenly increases (for example, when the differential value of the RF capacitance value exceeds a predetermined threshold value) is defined as a pull-in voltage. That is, this pull-in voltage is a voltage at which the electrostatic capacitance shifts to the maximum state.

  Further, when the applied voltage is gradually reduced from the maximum value, the movable portion 3A is separated from the insulating film 12A at a predetermined timing, and the RF capacitance is rapidly reduced. The applied voltage at the timing when the RF capacitance value rapidly decreases (for example, the timing when the differential value of the RF capacitance value becomes less than a predetermined threshold value) is defined as the pull-out voltage. That is, this pull-out voltage is a voltage that is released from a state where the electrostatic capacitance is maximum.

  As shown in FIG. 3, the RF capacitance value measured by the network analyzer 201 is input to the calculation unit 202. The calculation unit 202 inputs the voltage value of the power supply (V) at the timing when the RF capacitance value input from the network analyzer 201 suddenly increases, and measures this voltage value as a pull-in voltage. In addition, the calculation unit 202 inputs a voltage value of the power supply (V) at a timing when the RF capacitance value input from the network analyzer 201 rapidly decreases, and measures this voltage value as a pull-out voltage.

  Then, the inspection apparatus 100 repeats such a continuous voltage fluctuation due to the triangular wave a predetermined number of times (for example, 1000 times), and the arithmetic unit 202 measures the amount of change in the difference value between the pull-in voltage and the pull-out voltage. As shown in FIG. 6B, the non-defective element has almost no change in the pull-in voltage and the pull-out voltage even when the voltage fluctuation is repeated a predetermined number of times. On the other hand, as shown in FIGS. 7A and 7B, when a voltage is repeatedly applied to defective devices, the pull-out voltage is greatly reduced as compared with the pull-in voltage.

  Therefore, the determination unit 203 determines that an element in which the difference value between the pull-in voltage and the pull-out voltage does not change even when voltage application is repeated is an acceptable product, and an element in which the amount of change in the difference value between the pull-in voltage and the pull-out voltage is equal to or greater than a reference value. Is determined to be defective. Thereby, it is possible to inspect whether or not the element has a sticking phenomenon. Note that even if sticking due to charge-up occurs during inspection, the pull-in voltage and pull-out voltage change in the same manner, so that the difference value does not change depending on the presence or absence of sticking due to charge-up. Therefore, the inspection apparatus of the present invention can accurately inspect whether or not the sticking phenomenon due to factors other than charge-up occurs.

  The timing for setting the pull-in voltage and the pull-out voltage is not limited to the timing at which the RF capacitance value suddenly changes.

  FIG. 8 is a flowchart showing the operation of the inspection apparatus 100. As an initial operation, the inspection apparatus 100 repeats a continuous voltage fluctuation due to a triangular wave a predetermined number of times (for example, about 100 times) (s11). Then, the inspection apparatus 100 measures ΔV1 (ΔV1 = pull-in voltage−pull-out voltage), which is an initial value of the difference between the pull-in voltage and the pull-out voltage, in the arithmetic unit 202 (s12).

  Thereafter, the inspection apparatus 100 repeats the continuous voltage fluctuation due to the triangular wave a predetermined number of times (for example, about 1000 times) (s13). Then, the inspection apparatus 100 measures ΔV2 (ΔV2 = pull-in voltage−pull-out voltage), which is a difference value between the pull-in voltage and the pull-out voltage after being driven a predetermined number of times in the arithmetic unit 202 (s14). The determination unit 203 determines whether or not the value of ΔV2−ΔV1, which is a change in the difference value, is less than a predetermined reference value (s15). When the determination unit 203 determines that the value of ΔV2−ΔV1 is less than a predetermined reference value, the pull-in voltage and the pull-out voltage hardly change even after the voltage fluctuation is repeated a predetermined number of times. Determine (s16). On the other hand, if the value of ΔV2−ΔV1 is equal to or greater than a predetermined reference value, it is determined that the product is defective because the pull-out voltage has changed greatly as a result of repeating the voltage fluctuation a predetermined number of times (s16).

  As described above, the inspection apparatus 100 can inspect whether or not the element causes a sticking phenomenon due to a factor other than charge-up.

  In the above example, the mode in which the voltage is continuously changed in a triangular wave shape is shown, but other driving waveforms such as changing the voltage in a sine wave shape can also be used.

  Further, the number of repetitions and the speed of voltage change (drive frequency) are not limited to the above example.

SW ... Switch 1 ... Variable capacitance element 3A ... Movable part 5A, 5B ... Lower drive electrode 6 ... RF capacitance electrode 7A, 7B, 7C ... Upper drive electrode 8A, 8B, 8C ... Lower equipotential electrodes 9A, 9B, 9C ... Upper Drive electrode 100 ... Inspection device 201 ... Network analyzer 202 ... Calculation unit 203 ... Determination unit

Claims (4)

A fixed electrode;
A movable electrode facing the fixed electrode;
An insulating layer provided between the fixed electrode and the movable electrode;
A drive unit that changes a capacitance by applying a voltage between the fixed electrode and the movable electrode;
An inspection device for inspecting a variable capacitance element comprising:
Capacitance measuring means for measuring a change in capacitance of the variable capacitance element;
A calculation means for measuring a pull-in voltage that is a voltage at which the electrostatic capacity shifts to a maximum state and a pull-out voltage that is a voltage at which the electrostatic capacity is released from the maximum state;
A voltage that continuously changes between the fixed electrode and the movable electrode is repeatedly applied a predetermined number of times, and the pull-in voltage and the pull-out voltage after the continuously changing voltage is applied are continuously changed. Determination means for inspecting whether or not the variable capacitance element is a defective element based on a variation amount between the pull-in voltage and the pull-out voltage before voltage is applied;
A variable capacitance element inspection device comprising:   The determination means repeatedly applies a continuously changing voltage a predetermined number of times, and the difference value between the pull-in voltage and the pull-out voltage after the continuously changing voltage is applied, and the continuously changing voltage. 2. The variable capacitor according to claim 1, wherein a variable capacitor having a change amount between a difference value between the pull-in voltage and the pull-out voltage before a voltage is applied is determined to be a defective device. Element inspection equipment. A fixed electrode;
A movable electrode facing the fixed electrode;
An insulating layer provided between the fixed electrode and the movable electrode;
A drive unit that changes a capacitance by applying a voltage between the fixed electrode and the movable electrode;
An inspection method for inspecting a variable capacitance element comprising:
A capacitance measuring step for measuring a change in capacitance of the variable capacitance element;
A calculation step of measuring a pull-in voltage that is a voltage at which the electrostatic capacity shifts to a maximum state and a pull-out voltage that is a voltage at which the electrostatic capacity is released from the maximum state;
A voltage that continuously changes between the fixed electrode and the movable electrode is repeatedly applied a predetermined number of times, and the pull-in voltage and the pull-out voltage after the continuously changing voltage is applied are continuously changed. A determination step of inspecting whether or not the variable capacitance element is a defective element based on a variation amount between the pull-in voltage and the pull-out voltage before voltage is applied;
A method for inspecting a variable capacitance element, comprising:   In the determination step, a continuously changing voltage is repeatedly applied a predetermined number of times, the difference value between the pull-in voltage and the pull-out voltage after the continuously changing voltage is applied, and the continuously changing voltage. 4. The variable capacitor according to claim 3, wherein a variable capacitor having an amount of change between a difference value between the pull-in voltage and the pull-out voltage before a voltage is applied is determined to be a defective device. Element inspection method.

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