Sensor module and measuring system

Abstract

This sensor module comprises a first piezoelectric vibrator having a first electrode, a second piezoelectric vibrator having a second electrode, an electrode cover covering one of the first electrode and the second electrode, an oscillation circuit for causing the first piezoelectric vibrator and the second piezoelectric vibrator to oscillate, and a storage circuit for storing initial oscillation frequency information relating to both the first piezoelectric vibrator and a second oscillation frequency, wherein, when at least the piezoelectric vibrator, among the first piezoelectric vibrator and the second piezoelectric vibrator, of which the electrode is not covered by the electrode cover is driven by the oscillation circuit, the piezoelectric vibrator oscillates at a frequency corresponding to the thickness of a deposit accumulated on the surface of the electrode that is exposed without being covered by the electrode cover.

Description

Sensor module and measurement system

[0001] The present invention relates to a sensor module and a measurement system.

[0002] Conventionally, a quartz crystal microbalance (QCM) sensor using a quartz crystal oscillator is known. The QCM sensor can detect the presence or absence of a substance based on the difference between the resonant frequency of a reference quartz crystal oscillator and the resonant frequency of a detection quartz crystal oscillator to which the substance adheres (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2018-080947

[0004] Such a sensor can be installed in a material deposition device, such as a semiconductor manufacturing device, and used to detect the thickness of deposited material based on changes in the resonant frequency of the oscillator as the material accumulates. However, as the amount of material deposited on the oscillator increases, the oscillator's oscillation limit is exceeded, and the semiconductor manufacturing device may no longer be able to function as a sensor while the material is being deposited.

[0005] The present invention has been made in consideration of these points, and aims to make it possible to identify the lifespan of an oscillator mounted in a sensor that uses an oscillator to detect the amount of deposits.

[0006] In a first aspect of the present invention, there is provided a sensor module comprising: a first piezoelectric vibrator having a first electrode; a second piezoelectric vibrator having a second electrode; an electrode cover that covers one of the first electrode and the second electrode; an oscillation circuit that drives each of the first piezoelectric vibrator and the second piezoelectric vibrator to oscillate; and a memory circuit that stores, as initial oscillation frequency information, information corresponding to a first oscillation frequency measured by oscillating the first piezoelectric vibrator when shipping the first piezoelectric vibrator, and a second oscillation frequency measured by oscillating the second piezoelectric vibrator when shipping the second piezoelectric vibrator, wherein at least one of the first piezoelectric vibrator and the second piezoelectric vibrator, whose electrode is not covered by the electrode cover, oscillates at a frequency corresponding to the thickness of deposits that have accumulated on the surface of the exposed electrode that is not covered by the electrode cover, when driven by the oscillation circuit.

[0007] The storage circuit may further store information on vibrator identification numbers for identifying the first piezoelectric vibrator and the second piezoelectric vibrator.

[0008] The electrode cover is switchable between a state covering the first electrode and a state covering the second electrode, and when driven by the oscillation circuit, the first piezoelectric vibrator oscillates at a frequency corresponding to the thickness of deposits accumulated on the surface of the first electrode, and when driven by the oscillation circuit, the second piezoelectric vibrator oscillates at a frequency corresponding to the thickness of deposits accumulated on the surface of the second electrode, and the electrode cover may expose the first electrode when covering the second electrode to prevent deposits from accumulating on the surface of the second electrode, and may expose the second electrode when covering the first electrode to prevent deposits from accumulating on the surface of the first electrode.

[0009] When the electrode cover switches to a state covering the first electrode after the first piezoelectric vibrator is driven by the oscillation circuit, the memory circuit may store the oscillation frequency measured by oscillating the first piezoelectric vibrator as final oscillation frequency information.

[0010] The sensor module may include a plurality of combinations of the first piezoelectric vibrator and the second piezoelectric vibrator, the electrode cover being configured as a movable plate that covers the plurality of first electrodes and the plurality of second electrodes, the electrode cover having a first opening for exposing one of the first electrodes and a second opening for exposing one of the second electrodes, the first opening being arranged so that as the electrode cover moves, it moves sequentially to a plurality of positions corresponding to the plurality of first electrodes, exposing the plurality of first electrodes one by one, the second opening being arranged so that as the electrode cover moves, it moves sequentially to a plurality of positions corresponding to the plurality of second electrodes, exposing the plurality of second electrodes one by one, and the sensor module may further include a moving unit that moves the electrode cover.

[0011] The plurality of first piezoelectric vibrators are arranged along the circumference of a first circle of a predetermined radius on the upper surface of a fixed substrate, and the plurality of second piezoelectric vibrators are arranged along the circumference of a second circle concentric with the first circle on the upper surface of the fixed substrate, the electrode cover is rotatably provided while covering the plurality of first piezoelectric vibrators and the plurality of second piezoelectric vibrators, the first opening in the electrode cover is provided on the circumference of a circle that coincides with the first circle in a planar view, and the second opening is provided on the circumference of a circle that coincides with the second circle in a planar view, and the moving unit may expose one of the plurality of first electrodes and the plurality of second electrodes from the first opening or one of the second electrodes from the second opening by rotating the electrode cover around an axis that passes perpendicularly through the center of the first circle in a planar view.

[0012] In a second aspect of the present invention, there is provided a measurement system comprising the sensor module of the first aspect and a control device connected to the sensor module, wherein the control device has: a memory control unit capable of accessing the memory circuit of the sensor module and reading information stored in the memory circuit; a frequency measurement unit that measures the oscillation frequencies of the first piezoelectric vibrator and the second piezoelectric vibrator based on the oscillation frequency signal output by the oscillation circuit; a thickness determination unit that determines the thickness of the deposit deposited on the surface of the electrode that is exposed and not covered by the electrode cover, of the first electrode of the first piezoelectric vibrator and the second electrode of the second piezoelectric vibrator, based on the measurement result of the frequency measurement unit; and a lifetime determination unit that determines the lifetime of the piezoelectric vibrator that has the electrode that is exposed and not covered by the electrode cover, of the first piezoelectric vibrator and the second piezoelectric vibrator, based on the initial oscillation frequency information read out from the memory circuit by the memory control unit and the measurement result of the frequency measurement unit.

[0013] The life determination unit may determine the life of the first piezoelectric vibrator in response to the absolute value of the differential frequency between the oscillation frequency of the first piezoelectric vibrator and the oscillation frequency of the second piezoelectric vibrator becoming greater than or equal to a first threshold value based on the initial oscillation frequency information.

[0014] The memory circuit of the sensor module may further store information about the first threshold value based on the initial oscillation frequency information.

[0015] The memory circuit of the sensor module may further store information on a second threshold value having an absolute value smaller than the first threshold value, and the life determination unit may determine that the life of the first piezoelectric vibrator is nearing the end when the absolute value of the differential frequency between the oscillation frequency of the first piezoelectric vibrator and the oscillation frequency of the second piezoelectric vibrator becomes equal to or greater than the second threshold value.

[0016] In a third aspect of the present invention, there is provided a measurement system comprising the sensor module of the first aspect and a control device connected to the sensor module, wherein the control device has: a memory control unit capable of accessing the memory circuit of the sensor module and reading information stored in the memory circuit; an instruction unit that instructs the sensor module to switch the electrode cover; a frequency measurement unit that measures the oscillation frequencies of the first piezoelectric vibrator and the second piezoelectric vibrator based on an oscillation frequency signal output by the oscillation circuit; a thickness identification unit that identifies a thickness of the deposit deposited on a surface of an electrode that is exposed at the instruction of the instruction unit, of the first electrode of the first piezoelectric vibrator and the second electrode of the second piezoelectric vibrator, based on a measurement result by the frequency measurement unit; and a lifetime identification unit that identifies a lifetime of the piezoelectric vibrator that has an electrode that is exposed at the instruction of the instruction unit, of the first piezoelectric vibrator and the second piezoelectric vibrator, based on initial oscillation frequency information read out from the memory circuit by the memory control unit and the measurement result by the frequency measurement unit.

[0017] In a fourth aspect of the present invention, there is provided the sensor module of the first aspect and a control device connected to the sensor module, wherein the control device includes a memory control unit that can access the memory circuit of the sensor module and read information stored in the memory circuit, an instruction unit that instructs movement of the electrode cover so that the first opening is located at a position corresponding to the first piezoelectric vibrator of one combination of a plurality of first piezoelectric vibrators and second piezoelectric vibrators, or so that the second opening is located at a position corresponding to the second piezoelectric vibrator of one combination, and a control unit that performs the above-mentioned operation based on an oscillation frequency signal output by the oscillation circuit. Provided is a measurement system having: a frequency measurement unit that measures the oscillation frequency of one combination of the first piezoelectric vibrator and the second piezoelectric vibrator; a thickness determination unit that determines the thickness of the deposit deposited on the surface of one of the first electrodes of the first piezoelectric vibrator and the second electrode of the second piezoelectric vibrator that is exposed by instruction from the instruction unit, based on the measurement result of the frequency measurement unit; and a lifetime determination unit that determines the lifetime of one of the first piezoelectric vibrator and the second piezoelectric vibrator that has an electrode exposed by instruction from the instruction unit, based on the initial oscillation frequency information read out from the memory circuit by the memory control unit and the measurement result of the frequency measurement unit.

[0018] According to the present invention, it is possible to determine the life of an oscillator mounted in a sensor that uses an oscillator to detect the amount of deposits.

[0019] 1 shows an example of application of the measurement system S according to this embodiment to a semiconductor manufacturing apparatus 1. FIG. 1 shows a first configuration example of the sensor module 10 according to this embodiment. FIG. 2 shows a configuration example of the control device 100 according to this embodiment. FIG. 3 shows an operation flow of the control device 100 according to this embodiment. FIG. 4 shows a second configuration example of the sensor module 10 according to this embodiment. FIG. 5 shows an example of rotating the electrode cover 35 of the sensor module 40 of the fourth configuration example shown in FIG. 7. FIG. 6 shows a fifth configuration example of the sensor module 10 according to this embodiment.

[0020] 1 shows an example of a case where the measurement system S according to this embodiment is applied to a semiconductor manufacturing apparatus 1. The semiconductor manufacturing apparatus 1 is an apparatus for stacking semiconductor materials on a semiconductor wafer W. The semiconductor manufacturing apparatus 1 includes a chamber 2, a stage 3, and a film forming apparatus 4.

[0021] The chamber 2 is a container that seals a predetermined space. The chamber 2 is, for example, a vacuum chamber that can maintain a low air pressure in the sealed space. The stage 3 is provided inside the chamber 2 and mounts a semiconductor wafer W. The stage 3 may be configured to be movable within the chamber 2 while the semiconductor wafer W is mounted thereon.

[0022] The film forming apparatus 4 is an apparatus for depositing a material such as a metal, an insulator, or a semiconductor on the surface of the semiconductor wafer W. The film forming apparatus 4 is, for example, an apparatus for depositing a material by a liquid phase method or a vapor phase method, an apparatus for applying a material, or the like. Since various types of film forming apparatus 4 are known, a detailed description thereof will be omitted here. By using such a film forming apparatus 4, a semiconductor material is deposited on the surface of the semiconductor wafer W to form a thin film.

[0023] In such a semiconductor manufacturing apparatus 1, the thickness of the semiconductor material deposited on the semiconductor wafer W can be estimated by using, for example, the film formation conditions and film formation time of the film formation apparatus 4. However, there are cases where it is desired to measure the thickness of the semiconductor material actually deposited on the semiconductor wafer W. In particular, there are cases where it is desired to measure the thickness of the semiconductor material in real time while the semiconductor material is being formed. Therefore, the measurement system S according to this embodiment measures the thickness of the semiconductor material deposited on the surface of such a semiconductor wafer W.

[0024] The measurement system S includes a sensor module 10, a connection cable 30, and a control device 100. The sensor module 10 is installed inside the chamber 2. Like the semiconductor wafer W, the sensor module 10 is provided in an area where the film forming device 4 can deposit material, and measures the thickness of the material deposited on the sensor module 10 itself. The sensor module 10 and the control device 100 will be described later.

[0025] The connection cable 30 connects the sensor module 10 in the chamber 2 to the control device 100 outside the chamber 2. The connection cable 30 connects the sensor module 10 to the control device 100 via, for example, a connector 5. In this case, the connector 5 is provided in the chamber 2 and is configured to be able to send and receive electrical signals while maintaining the airtightness of the chamber 2. Next, the sensor module 10 of the measurement system S will be described.

[0026] <First Configuration Example of Sensor Module 10> Fig. 2 shows a first configuration example of the sensor module 10 according to this embodiment. Fig. 2 schematically shows a cross section of the sensor module 10. In Fig. 2, three orthogonal axes are defined as the X-axis, the Y-axis, and the Z-axis. The sensor module 10 includes a substrate 11, a piezoelectric vibrator 12, a heater circuit 14, an oscillation circuit 15, a memory circuit 16, a base member 17, a coupling socket 18, a temperature sensor 19, and a cover 20.

[0027] The substrate 11 is a substrate for fixing the piezoelectric vibrator 12. The substrate 11 is, for example, a ceramic substrate such as a low temperature co-fired ceramics (LTCC) substrate.

[0028] The piezoelectric vibrator 12 has electrodes 13, and when driven by the oscillation circuit 15, oscillates at a frequency corresponding to the thickness of deposits accumulated on the surface of the electrodes 13. The piezoelectric vibrator 12 is, for example, a quartz crystal vibrator, a ceramic vibrator, a langasite vibrator, or the like. In this embodiment, an example will be described in which the piezoelectric vibrator 12 is a two-electrode type quartz crystal vibrator formed on a quartz crystal substrate composed of a single quartz crystal piece.

[0029] One electrode 13a of the piezoelectric vibrator 12 is provided on the opposite side of the substrate 11 and is exposed to the outside. The other electrode 13b of the piezoelectric vibrator 12, which is different from the electrode 13a, is provided in a position that is not exposed to the outside. As a result, when the film forming device 4 of the semiconductor manufacturing apparatus 1 starts depositing the semiconductor material, the semiconductor material is deposited on the surface of the electrode 13a of the piezoelectric vibrator 12.

[0030] The heater circuit 14 adjusts the temperature of the piezoelectric vibrator 12 via the substrate 11. The heater circuit 14 has, for example, a heater that heats the piezoelectric vibrator 12. The heater is, for example, a Peltier element, a resistor, a heating wire, or the like. The heater may be provided on the surface of the substrate 11 opposite to the piezoelectric vibrator 12, or alternatively, may be provided in an inner layer of the substrate 11.

[0031] The heater circuit 14 has a function of adjusting the amount of heat based on the temperature of the substrate 11 measured by the temperature sensor 19. The heater circuit 14 has a circuit that adjusts the power supplied to the heater so as to maintain the temperature of the substrate 11 at a predetermined temperature or within a predetermined temperature range. The heater circuit 14 functions as a heating control unit that controls the amount of heat from the heater based on, for example, the difference between the temperature measured by the temperature sensor 19 and a target temperature.

[0032] The oscillator circuit 15 has a circuit for driving the piezoelectric vibrator 12 to oscillate in response to a control signal from the control device 100. If the sensor module 10 has multiple vibrators, the oscillator circuit 15 has a circuit for oscillating each of the multiple vibrators. The oscillator circuit 15 outputs a signal oscillated by the piezoelectric vibrator 12 as an oscillation frequency signal. The oscillation frequency signal output by the oscillator circuit 15 is input to the control device 100 via the connector 5 and the connection cable 30. The oscillator circuit 15 is formed on a predetermined circuit board.

[0033] The storage circuit 16 stores, as initial oscillation frequency information, the oscillation frequency measured by oscillating the piezoelectric vibrator 12 before shipping the piezoelectric vibrator 12. The storage circuit 16 is a nonvolatile memory. The storage circuit 16 is preferably a memory that can be read and rewritten by an electrical signal.

[0034] The memory circuit 16 is configured to be able to update information by overwriting previously stored information in a memory area. As a result, when the memory area of ​​the memory circuit 16 becomes full of information, the old memory area can be overwritten with the latest information. The memory circuit 16 may be formed on the circuit board on which the oscillator circuit 15 is formed, or alternatively, on another circuit board.

[0035] The base member 17 is a member for fixing the oscillator circuit 15. The coupling socket 18 is a member for electrically connecting the oscillator circuit 15 and the piezoelectric vibrator 12. For example, a pin (not shown) that is electrically connected to the piezoelectric vibrator 12 and protrudes from the substrate 11 is inserted into the coupling socket 18. Since the piezoelectric vibrator 12 is connected to the oscillator circuit 15 via the pin and the coupling socket 18, even if heating by the heater circuit 14 causes a wide range of temperature changes and expansion and contraction in various parts, the coupling socket 18 can absorb the stress caused by the expansion and contraction.

[0036] The temperature sensor 19 measures the surface temperature of the substrate 11 on which the piezoelectric vibrator 12 is provided. The temperature sensor 19 is, for example, a resistance temperature detector using platinum or the like, a thermocouple, a thermistor, or the like. The temperature sensor 19 is preferably attached in contact with the substrate 11. Alternatively, the temperature sensor 19 may be attached in contact with the piezoelectric vibrator 12.

[0037] The cover 20 covers the sensor module 10 except for the electrode 13 a, and has a through hole that exposes the electrode 13 a. When the sensor module 10 is installed inside the chamber 2 so that the electrode 13 a faces the film deposition device 4 of the semiconductor manufacturing apparatus 1, the same material as that deposited on the semiconductor wafer W by the film deposition device 4 is deposited on the electrode 13 a to the same thickness as that deposited on the semiconductor wafer W.

[0038] When a substance is deposited on the electrode 13a of the piezoelectric vibrator 12, the resonant frequency of the piezoelectric vibrator 12 changes depending on the thickness of the deposited substance. Therefore, the control device 100 of the measurement system S determines the thickness of the substance deposited on the electrode 13a by measuring such a change in the resonant frequency of the piezoelectric vibrator 12. Such a control device 100 will now be described.

[0039] 3 shows an example of the configuration of the control device 100 according to this embodiment. The control device 100 includes an input unit 110, an interface 120, a power supply unit 130, a frequency measurement unit 140, a storage unit 150, a display unit 160, and a control unit 170.

[0040] The input unit 110 receives operations, instructions, and the like from the user of the control device 100. The input unit 110 is a part that allows the user to input measurement conditions for measuring the thickness of deposits accumulated on the sensor module 10. The input unit 110 has one or more input devices such as a keyboard, a mouse, a touch panel, and a voice input device.

[0041] The interface 120 is connected to the connection cable 30 and is connected to the sensor module 10. The interface 120 is a part for exchanging electrical signals with the sensor module 10. The interface 120 exchanges electrical signals between the heater circuit 14, the oscillation circuit 15, the memory circuit 16, and the temperature sensor 19 and the control device 100, for example.

[0042] The power supply unit 130 supplies power to the sensor module 10. The power supply unit 130 functions as a power source for the circuits and heaters provided in the sensor module 10. The power supply unit 130 may change the power it supplies based on the control operation of the control unit 170.

[0043] The frequency measurement unit 140 receives the oscillation frequency signal output from the oscillation circuit 15 via the interface 120. Then, the frequency measurement unit 140 measures the oscillation frequency of the piezoelectric vibrator 12 based on the oscillation frequency signal. The frequency measurement unit 140 has, for example, a frequency counter or the like, and measures the oscillation frequency of the oscillation frequency signal.

[0044] The frequency measurement unit 140 continuously measures the oscillation frequency of the oscillation frequency signal at least during a deposition period from the start to the end of the deposition operation of the semiconductor material by the film formation device 4 of the semiconductor manufacturing apparatus 1. The frequency measurement unit 140 measures the oscillation frequency of the oscillation frequency signal at predetermined time intervals during the deposition period, for example. The frequency measurement unit 140 supplies the measurement result to the control unit 170. It is preferable that the frequency measurement unit 140 supplies the measurement result to the control unit 170 every time it measures the oscillation frequency.

[0045] The storage unit 150 is a storage medium including a read-only memory (ROM) and a random access memory (RAM). The storage unit 150 may also include a large-capacity storage device such as a hard disk drive (HDD) and / or a solid state drive (SSD). For example, when a computer or the like functions as at least a part of the control device 100, the storage unit 150 may store information such as an operating system (OS) that causes the computer to function, and programs. The storage unit 150 may also store various information including a database that is referenced when a program is executed.

[0046] The storage unit 150 may also store intermediate data, calculation results, thresholds, reference values, parameters, and the like that are generated (or used) by the control device 100 during operation. For example, the storage unit 150 may store information that the control device 100 acquires from the sensor module 10, or may store information to be written to the storage circuit 16 of the sensor module 10. The storage unit 150 may also supply the stored data to a request source in response to a request from each unit within the control device 100.

[0047] The display unit 160 displays information related to the measurement of the thickness of the deposit. The display unit 160 may display, for example, the measurement conditions, the measurement results, the connection status with the sensor module 10, information about the sensor module 10, etc. The display unit 160 may also function as a display for displaying the OS, the execution status of applications, etc. The display unit 160 may have a touch panel function and operate as at least a part of the input unit 110.

[0048] The control unit 170 controls each unit of the control device 100 and the sensor module 10. The control unit 170, for example, reads out information stored in the storage unit 150. The control unit 170 may also cause the storage unit 150 to record information. The control unit 170, for example, transmits a control signal to the oscillation circuit 15 for driving the oscillation circuit 15, causing the oscillation circuit 15 to drive the piezoelectric vibrator 12. The operation of the control unit 170 will be described in more detail below.

[0049] The control unit 170 is, for example, a CPU (Central Processing Unit). The control unit 170 has an acquisition unit 171, a memory control unit 172, a thickness determination unit 173, a lifespan determination unit 174, and a display control unit 175. In other words, the CPU executes a program stored in the storage unit 150 to function as the control unit 170 having the acquisition unit 171, the memory control unit 172, the thickness determination unit 173, the lifespan determination unit 174, and the display control unit 175.

[0050] The acquisition unit 171 acquires the measurement results of the oscillation frequency measured by the frequency measurement unit 140. The acquisition unit 171 also acquires the measurement results of the temperature of the substrate 11 by the temperature sensor 19. The acquisition unit 171 supplies the acquired measurement results of the oscillation frequency and the temperature to the thickness determination unit 173 and the life determination unit 174.

[0051] The memory control unit 172 is configured to be able to access the memory circuit 16 of the sensor module 10 and read information stored in the memory circuit 16. The memory control unit 172, for example, reads and acquires initial oscillation frequency information stored in the memory circuit 16. The memory control unit 172 supplies the acquired initial oscillation frequency information to the life specification unit 174. The memory control unit 172 may be configured to be able to access the memory circuit 16 of the sensor module 10 and write predetermined information to the memory circuit 16.

[0052] The thickness determination unit 173 determines the thickness of the deposit deposited on the surface of the electrode 13 a of the piezoelectric vibrator 12 based on the oscillation frequency measured by the frequency measurement unit 140. The piezoelectric vibrator 12 oscillates at a resonance frequency corresponding to the thickness of the deposit deposited on the surface of the electrode 13 a. Therefore, when the measurement result of the oscillation frequency at the start of the semiconductor material deposition operation by the film formation device 4 of the semiconductor manufacturing apparatus 1 is denoted as f1 and the measurement result of the oscillation frequency after a predetermined time t has elapsed since the start of the deposition operation is denoted as f2, the thickness determination unit 173 can determine the thickness of the deposit after the predetermined time t has elapsed based on the difference in oscillation frequencies Δf = f2 - f1.

[0053] The resonant frequency of the piezoelectric vibrator 12 also changes depending on the temperature. Therefore, it is desirable that the thickness determination unit 173 temperature-compensates the measurement result of the oscillation frequency measured by the frequency measurement unit 140 using the temperature measurement result of the temperature sensor 19. The temperature characteristics of the resonant frequency of the piezoelectric vibrator 12 may be measured and determined in advance, or alternatively, if data is publicly available as specifications of the piezoelectric vibrator 12, the publicly available data may be acquired. It is desirable that the temperature characteristics of the resonant frequency of the piezoelectric vibrator 12 be stored in the storage unit 150.

[0054] The thickness determination unit 173 determines the thickness dd of the deposit based on, for example, the oscillation frequency difference Δf' = f2' - f1' calculated from corrected frequencies f1', f2' obtained by temperature-correcting the oscillation frequency measurement results f1, f2. The relational expression between the oscillation frequency difference and the deposit thickness may be determined by pre-measurement or, alternatively, may be determined from a theoretical formula or the like. The determined relational expression is preferably stored in the storage unit 150. If the heater circuit 14 of the sensor module 10 maintains the temperature of the piezoelectric vibrator 12 at a constant temperature, the temperature correction of the oscillation frequency measurement results f1, f2 may be omitted.

[0055] It is desirable that the thickness specifying unit 173 specifies the thickness of the deposit each time the frequency measuring unit 140 measures the oscillation frequency, thereby enabling the measurement system S to measure the thickness dd of the deposit deposited on the semiconductor wafer W almost in real time.

[0056] The lifespan determination unit 174 determines the lifespan of the piezoelectric vibrator 12 based on the initial oscillation frequency information read by the memory control unit 172 from the memory circuit 16 of the sensor module 10 and the oscillation frequency measured by the frequency measurement unit 140. The piezoelectric vibrator 12 will no longer be able to oscillate when the thickness of deposits accumulated on the surface of the electrode 13a reaches a predetermined thickness. The lifespan determination unit 174 determines the range that can be measured before the piezoelectric vibrator 12 will no longer be able to oscillate as the lifespan.

[0057] The thickness dx of the deposit at which the piezoelectric vibrator 12 becomes inoperable may be measured and specified in advance, or alternatively, if data is publicly available as specifications of the piezoelectric vibrator 12, the publicly available data may be acquired. The thickness dx of the deposit at which the piezoelectric vibrator 12 reaches the end of its life is preferably stored in the memory unit 150. Alternatively, the thickness dx of the deposit at which the piezoelectric vibrator 12 reaches the end of its life may be stored in the memory circuit 16 of the sensor module 10.

[0058] The life specifying unit 174 specifies the life of the piezoelectric vibrator 12 by comparing the initial oscillation frequency information with a corrected frequency obtained by correcting the oscillation frequency measured by the frequency measurement unit 140 based on the surface temperature of the substrate 11. For example, when the initial oscillation frequency information is f0, the life specifying unit 174 specifies the thickness dn of the deposit accumulated from the initial state of the electrode 13a based on the difference Δf0' = f2' - f0 between the initial oscillation frequency information and the oscillation frequency. The formula used by the life specifying unit 174 to calculate the thickness of the deposit from the difference in oscillation frequency is the same as the formula used by the thickness specifying unit 173 to calculate the thickness of the deposit.

[0059] There may be a case where the heater circuit 14 of the sensor module 10 maintains the temperature of the piezoelectric vibrator 12 at the temperature at which the initial oscillation frequency information of the piezoelectric vibrator 12 was measured. In this case, the life determination unit 174 may omit temperature correction of the oscillation frequency measurement result f2.

[0060] When the piezoelectric vibrator 12 in its initial state after shipment is mounted on the sensor module 10 and the thickness determination unit 173 determines the thickness of the deposit for the first time, the thickness dn of the deposit deposited from the initial state of the electrode 13a is equal to the thickness dd of the deposit determined by the thickness determination unit 173. Furthermore, when one or more measurements have been taken prior to the current measurement of the thickness of the deposit, the thickness obtained by adding the thickness dd of the deposit deposited in the current measurement to the thickness of the deposit deposited up to the immediately preceding measurement is equal to the thickness dn of the deposit deposited from the initial state of the electrode 13a.

[0061] The lifespan specifying unit 174 calculates the difference Δd=dx−dn between the thickness dx of the deposit at which the piezoelectric vibrator 12 reaches the end of its lifespan and the specified thickness dn of the deposit. The difference Δd is the thickness of the deposit that can be measured by the piezoelectric vibrator 12. The lifespan specifying unit 174 specifies, for example, the measurable thickness Δd of the deposit as the lifespan. Alternatively, or in addition, the lifespan specifying unit 174 may calculate a difference Δfx in the oscillation frequency corresponding to the measurable thickness Δd of the deposit, and specify the difference Δfx as the lifespan.

[0062] The life specifying unit 174 may also calculate an estimated life corresponding to the measurable thickness Δd of the deposit. For example, the life specifying unit 174 divides the thickness of the deposit specified based on the measurement results of two oscillation frequencies measured by the frequency measurement unit 140 at two different times by the time interval between the two different times, and sets the value to the estimated deposition rate vv. Then, the life specifying unit 174 sets the value to the estimated life vt by dividing the measurable thickness Δd of the deposit by the estimated deposition rate vv.

[0063] For example, when the life specifying unit 174 specifies the thickness dd of the deposit after a predetermined time t has elapsed, it sets the estimated deposition rate vv to dd / t and calculates the estimated life time vt as Δd / vv = Δd·t / dd. The life specifying unit 174 may specify the estimated life time vt calculated in this way as the life. In this way, the life specifying unit 174 can specify the time until the piezoelectric vibrator 12 reaches its measurement limit when deposition proceeds at the same deposition rate as the life.

[0064] It is desirable that the life specification unit 174 specifies the life of the piezoelectric vibrator 12 each time the frequency measurement unit 140 measures the oscillation frequency. This allows the measurement system S to measure the life of the piezoelectric vibrator 12 of the sensor module 10 almost in real time.

[0065] The display control unit 175 displays the thickness of the deposit identified by the thickness identification unit 173 and the lifetime of the piezoelectric vibrator 12 identified by the lifetime identification unit 174 on the display unit 160 as the measurement results of the measurement system S. This allows a user of the measurement system S to understand the thickness of the deposited semiconductor material and the lifetime of the piezoelectric vibrator 12 of the sensor module 10 while depositing the semiconductor material on the semiconductor wafer W using the semiconductor manufacturing apparatus 1. This allows the user to understand the appropriate time to replace the sensor module 10.

[0066] For example, after the film forming device 4 of the semiconductor manufacturing apparatus 1 has completed depositing a semiconductor material, the life of the piezoelectric vibrator 12 identified by the life identifying unit 174 indicates the measurement limit at which the measurement system S can measure the thickness of the next deposit. Therefore, the user can easily determine whether to continue the next operation of the semiconductor manufacturing apparatus 1 or to replace the sensor module 10 and then resume operation.

[0067] The control device 100 may measure the life of the piezoelectric vibrator 12 immediately after powering on and becoming ready to measure the thickness of the deposit. Alternatively, the control device 100 may measure the life of the piezoelectric vibrator 12 in response to the user inputting measurement conditions into the input unit 110. This allows the user to easily determine whether or not to replace the sensor module 10 before starting operation of the semiconductor manufacturing apparatus 1. The operation of such a control device 100 will now be described.

[0068] <Operation Flow of the Control Device 100> Figure 4 shows the operation flow of the control device 100 according to this embodiment. First, the input unit 110 accepts measurement conditions input by the user (S51). The measurement conditions may include information on the thickness of the semiconductor material to be deposited on the semiconductor wafer W. Next, the memory control unit 172 accesses the memory circuit 16 of the sensor module 10 and reads and acquires the initial oscillation frequency information stored in the memory circuit 16 (S52). Next, the control unit 170 causes the oscillation circuit 15 to drive the piezoelectric vibrator 12 (S53).

[0069] Next, the control unit 170 measures the thickness of the deposit accumulated on the piezoelectric vibrator 12 (S54). In this case, the frequency measurement unit 140 measures the oscillation frequency of the piezoelectric vibrator 12, and the acquisition unit 171 acquires the oscillation frequency measurement result and the temperature measurement result of the temperature sensor 19. Then, the thickness identification unit 173 measures the thickness of the deposit accumulated on the piezoelectric vibrator 12 based on the oscillation frequency measurement result and the temperature measurement result. The display control unit 175 displays the identified thickness of the deposit on the display unit 160.

[0070] Next, the control unit 170 identifies the life of the piezoelectric vibrator 12 (S55). In this case, the life identification unit 174 identifies the life of the piezoelectric vibrator 12 based on the oscillation frequency measurement results, the temperature measurement results, and the initial oscillation frequency information. The display control unit 175 displays the identified life of the piezoelectric vibrator 12 on the display unit 160. This allows the user to understand the information about the piezoelectric vibrator 12 before the semiconductor material is deposited on the semiconductor wafer W.

[0071] Next, the input unit 110 receives a command from the user to start measurement (S56). Here, the user inputs a command to start measurement into the input unit 110, for example, when the film formation device 4 of the semiconductor manufacturing equipment 1 starts depositing semiconductor material. Alternatively, if the measurement conditions input by the user include a measurement start time, the control unit 170 may start measurement when the measurement start time arrives. Furthermore, the control device 100 may be connected via a network or the like to a control device that controls the operation of the semiconductor manufacturing equipment 1. In this case, the control device 100 may receive a start signal to start measurement from the control device of the semiconductor manufacturing equipment 1.

[0072] The control device 100 measures the thickness of the deposit (S57) in the same manner as in S54, and determines the life of the piezoelectric vibrator 12 in the same manner as in S55 (S58). The control device 100 repeats the operations of S57 and S58 until the input unit 110 receives a signal indicating the end of the measurement (S59: Yes) (S59: No). Here, the user inputs a command to end the measurement into the input unit 110, for example, when the film forming device 4 of the semiconductor manufacturing apparatus 1 finishes depositing the semiconductor material. Alternatively, if the measurement conditions input by the user include a measurement end time, the control unit 170 may end the measurement when the measurement end time arrives. The control device 100 may also receive an end signal to end the measurement from the control device of the semiconductor manufacturing apparatus 1.

[0073] According to the measurement system S of this embodiment described above, by storing the initial oscillation frequency information of the piezoelectric vibrator 12 in the memory circuit 16 of the sensor module 10, the memory control unit 172 of the control device 100 can read out the initial oscillation frequency information and identify the life of the piezoelectric vibrator 12. As a result, when the semiconductor manufacturing apparatus 1 deposits a semiconductor material on a semiconductor wafer W, it is possible to measure the life of the piezoelectric vibrator 12 while measuring the thickness of the deposited semiconductor material almost in real time.

[0074] Therefore, the user can replace the sensor module 10 at an appropriate time, and can prevent the piezoelectric vibrator 12 from becoming inoperable while the semiconductor manufacturing apparatus 1 is depositing semiconductor material. Furthermore, when the sensor module 10 is replaced, the control device 100 can determine the lifespan of the replaced piezoelectric vibrator 12 by reading out the initial oscillation frequency information stored in the memory circuit 16 of the replaced sensor module 10.

[0075] <Other Configurations> In the measurement system S according to the present embodiment described above, an example has been described in which the user replaces the sensor module 10 before the piezoelectric vibrator 12 stops working, but the present invention is not limited to this. The user may also replace the piezoelectric vibrator 12 of the sensor module 10. When the user replaces the piezoelectric vibrator 12 of the sensor module 10, the measurement system S may update the initial oscillation frequency information of the piezoelectric vibrator 12 before replacement in the memory circuit 16 to the initial oscillation frequency information of the piezoelectric vibrator 12 after replacement.

[0076] In this case, for example, the frequency measurement unit 140 measures the oscillation frequency of the replaced piezoelectric vibrator 12, and the memory control unit 172 writes the measurement result of the frequency measurement unit 140 as initial oscillation frequency information into the memory circuit 16. This allows the measurement system S to identify the lifespan of the replaced piezoelectric vibrator 12.

[0077] The measurement system S according to the present embodiment has been described above as an example in which the initial oscillation frequency information of the piezoelectric vibrator 12 is stored in the memory circuit 16 of the sensor module 10, but is not limited to this. In addition, the memory circuit 16 may store information on at least one of a first identification number for identifying the piezoelectric vibrator 12 and a second identification number for identifying the sensor module 10.

[0078] When the first identification number and / or the second identification number are stored in the memory circuit 16, the memory control unit 172 may read out the first identification number and / or the second identification number when reading out the initial oscillation frequency information. In this case, the display control unit 175 displays the read out first identification number and / or the second identification number on the display unit 160. This allows the user to know information identifying the sensor module 10 and / or the piezoelectric vibrator 12 used for measurement, which can be useful for maintenance, management, etc. of the sensor module 10 and / or the piezoelectric vibrator 12.

[0079] In the measurement system S according to the present embodiment, an example has been described in which the storage circuit 16 stores the oscillation frequency measured by oscillating the piezoelectric vibrator 12 before shipping the piezoelectric vibrator 12 as initial oscillation frequency information, but the present invention is not limited to this. The storage circuit 16 only needs to be able to record information for identifying the lifespan of the piezoelectric vibrator 12.

[0080] For example, the memory circuit 16 may store, as initial oscillation frequency information, the oscillation frequency measured by oscillating the piezoelectric vibrator 12 when the measurement system S is installed. For example, when the frequency measurement unit 140 measures the oscillation frequency of the piezoelectric vibrator 12 after the input unit 110 receives a predetermined operation indicating that the measurement system S has been installed, the memory control unit 172 updates the initial oscillation frequency information stored in the memory circuit 16 to information about the measured oscillation frequency of the piezoelectric vibrator 12.

[0081] As a result, for example, when the measurement system S is applied to the semiconductor manufacturing equipment 1 to construct a semiconductor manufacturing system, the memory circuit 16 can reliably store the initial value of the piezoelectric vibrator 12 actually mounted on the sensor module 10. The memory circuit 16 may also store information on the environmental temperature when the initial oscillation frequency information is measured. Note that although an example in which the measurement system S according to this embodiment is applied to the semiconductor manufacturing equipment 1 has been described, this is merely one example. The measurement system S can be applied to any device that deposits deposits, not just the semiconductor manufacturing equipment 1.

[0082] In the above embodiment, an example in which the sensor module 10 has one piezoelectric vibrator 12 has been described, but the present invention is not limited to this. The sensor module 10 may have a plurality of piezoelectric vibrators 12. Therefore, a sensor module 10 having two piezoelectric vibrators 12 will be described next.

[0083] <Second Configuration Example of Sensor Module 10> Figure 5 shows a second configuration example of the sensor module 10 according to this embodiment. In the sensor module 10 of the second configuration example, components that operate in substantially the same manner as those of the sensor module 10 of the first configuration example shown in Figure 2 are designated by the same reference numerals, and redundant explanations will be omitted. The sensor module 10 of the second configuration example further includes a first piezoelectric vibrator 31, a second piezoelectric vibrator 33, and an electrode cover 35.

[0084] The first piezoelectric vibrator 31 has a first electrode 32. The second piezoelectric vibrator 33 has a second electrode 34. The first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 are elements similar to the piezoelectric vibrator 12 described in FIG. 2. For example, the first electrode 32 and the second electrode 34 are two-electrode electrodes, and one electrode 32a and one electrode 34a are provided on the opposite side of the substrate 11, with the electrode surface facing the outside of the sensor module 10. The other electrodes 32b and one electrode 34b of the first electrode 32 and the second electrode 34 facing the substrate 11 are provided in positions that are not exposed to the outside.

[0085] As such, since electrode 32b (electrode 34b) is not exposed to the outside, when electrode 32a is exposed to the outside, it may be expressed as "the first electrode 32 (second electrode 34) is exposed," when electrode 32a is covered with electrode cover 35, it may be expressed as "the first electrode 32 (second electrode 34) is covered with electrode cover 35," and when deposits accumulate on electrode 32a, it may be expressed as "deposits have accumulated on the first electrode 32 (second electrode 34)."

[0086] The electrode cover 35 covers one of the first electrode 32 and the second electrode 34. Fig. 5 shows an example in which the electrode cover 35 is part of the cover 20 and covers the second electrode 34 of the second piezoelectric vibrator 33 so as not to be exposed to the outside. The cover 20 covers the first piezoelectric vibrator 31 except for the first electrode 32. In other words, the cover 20 and the electrode cover 35 expose the first electrode 32 to the outside.

[0087] The heater circuit 14 adjusts the temperatures of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 via the substrate 11. The oscillation circuit 15 drives each of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 to oscillate. The memory circuit 16 stores a first oscillation frequency (hereinafter, f １ 0), and a second oscillation frequency (hereinafter, f ２ 0) is stored as the initial oscillation frequency information.

[0088] The memory circuit 16 may further store information on vibrator identification numbers for identifying the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33. The memory circuit 16 may also store information indicating which of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 has an exposed electrode (or is not exposed), in association with the vibrator identification number.

[0089] Since the first electrode 32 of the first piezoelectric vibrator 31 is exposed to the outside, for example, when the sensor module 10 is provided inside the film forming apparatus 4, deposits of semiconductor material or the like accumulate on the first electrode 32. When the first piezoelectric vibrator 31 is driven by the oscillation circuit 15, it oscillates at a frequency corresponding to the thickness of the deposits accumulated on the surface of the electrode 32a that is exposed and not covered by the electrode cover 35. In other words, of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33, the piezoelectric vibrator whose electrode is not covered by the electrode cover 35 operates as a detection piezoelectric vibrator like the piezoelectric vibrator 12 described in FIG. 2 .

[0090] On the other hand, since the second electrode 34 of the second piezoelectric vibrator 33 is not exposed to the outside, even if the sensor module 10 is installed inside the film formation apparatus 4, deposits of semiconductor material or the like do not accumulate on the second electrode 34. Therefore, the second piezoelectric vibrator 33 oscillates at a frequency corresponding to the initial state of the second piezoelectric vibrator 33 when shipped. In other words, the second piezoelectric vibrator 33 operates as a reference piezoelectric vibrator that serves as a standard for a state where no deposits have accumulated. Therefore, the control device 100 of the measurement system S uses the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 to determine the thickness of the material deposited on the first electrode 32.

[0091] <Operation of control device 100 using sensor module 10 of second configuration example> The control device 100 shown in Fig. 3 can also use the sensor module 10 of the second configuration example. In this case, the control device 100 is also connected to the sensor module 10 of the second configuration example via the interface 120.

[0092] The frequency measurement unit 140 receives the oscillation frequency signals of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 output from the oscillation circuit 15 via the interface 120. The frequency measurement unit 140 measures the oscillation frequencies of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 based on the oscillation frequency signals output by the oscillation circuit 15. The frequency measurement unit 140 supplies the measurement results to the control unit 170.

[0093] The memory control unit 172 of the control unit 170 reads and acquires the initial oscillation frequency information of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 stored in the memory circuit 16. Then, the thickness determination unit 173 of the control unit 170 determines the thickness of the deposits accumulated on the surface of the electrode (first electrode 32 in this example) that is exposed and not covered by the electrode cover 35, of the first electrode 32 of the first piezoelectric vibrator 31 and the second electrode 34 of the second piezoelectric vibrator 33, based on the result of measurement by the frequency measurement unit 140.

[0094] The thickness determination unit 173 may determine the thickness of the deposit in the same manner as the operation described with reference to FIG. 3. For example, the thickness determination unit 173 may determine the thickness of the deposit by determining the measurement result of the oscillation frequency of the first piezoelectric vibrator 31 at the start of the deposition operation of the semiconductor material by the film forming device 4 of the semiconductor manufacturing apparatus 1 as f １1. The measurement result of the oscillation frequency of the second piezoelectric vibrator 33 is f ２ 1. The measurement result of the oscillation frequency of the first piezoelectric vibrator 31 after a predetermined time t has elapsed since the start of the deposition operation is set to f １ 2, and the measurement result of the oscillation frequency of the second piezoelectric vibrator 33 after a predetermined time t has elapsed since the start of the deposition operation is f ２ The thickness specifying unit 173 determines, for example, the difference in oscillation frequency Δf1=f １ 2-f １ 1, the thickness dd of the deposit after a given time t can be determined.

[0095] Instead, the thickness determination unit 173 determines the measurement result f of the oscillation frequency of the second piezoelectric vibrator 33 at the start of the deposition operation. ２ The difference in oscillation frequency using 1 is Δf2 = f １ 2-f ２ 1, the thickness dd of the deposit after a predetermined time t has elapsed may be determined. In addition, the thickness determination unit 173 may determine the difference frequency Δf2 between Δf2 and the start frequency Δf2 ０ = f １ 1-f ２ Difference from 1 Δf2-Δf2 ０ The thickness dd of the deposit may be determined based on

[0096] In addition, even after the predetermined time t has elapsed, no material accumulates on the second piezoelectric vibrator 33, so ideally, f ２ 1=f ２ However, due to changes in the ambient temperature of the second piezoelectric vibrator 33, ２ 1 ≠ f ２ 2. Therefore, the thickness specifying unit 173 determines whether f ２ f instead of 1 ２ 2, Δf2″=f １ 2-f ２ 2, the thickness dd of the deposit after a predetermined time t has elapsed. In addition, the thickness specifying unit 173 may specify the difference frequency Δf2″ and the difference frequency Δf2 ０ = f １ 1-f ２ Difference from 1 Δf2″−Δf2 ０ The thickness dd of the deposit may be determined based on

[0097] Furthermore, the thickness determination unit 173 determines the measurement result f of the oscillation frequency １ 1. f １ 2. f ２ 1. f ２ 2 is temperature-corrected １ 1', f １ 2', f ２ 1', f ２ The difference in oscillation frequency using Δf1′=f １ 2'-f １ 1', Δf2'=f １ 2'-f ２ 1', or Δf2'''=f １ 2'-f ２ Based on 2', the thickness dd of the deposit may be determined.

[0098] The life specifying unit 174 specifies the life of the piezoelectric vibrator having an electrode (first electrode 32 in this example) that is exposed and not covered by the electrode cover 35, out of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33, based on the initial oscillation frequency information read out by the memory control unit 172 from the memory circuit 16 and the measurement result by the frequency measurement unit 140. The life specifying unit 174 may specify the life of the deposit in the same manner as the operation described with reference to FIG.

[0099] Furthermore, the life specification unit 174 determines the oscillation frequency f １ 2 and the oscillation frequency f of the second piezoelectric vibrator 33 ２ 1 (or f ２ The life of the first piezoelectric vibrator 31 is determined when the absolute value |Δf2| (or |Δf2″|) of the difference frequency between the oscillation frequency f １ 2 is the initial frequency f １ Here, the frequency 95 kHz, which indicates the index of the end of the life of the first piezoelectric vibrator 31, is defined as f ｔ１ In this case, the first threshold is f ｔ１ may be set to

[0100] The first frequency f, which is the initial frequency of the first piezoelectric vibrator 31, １0 and the second frequency f which is the initial frequency of the second piezoelectric vibrator 33. ２ 0 may not match due to individual differences in the vibrator. In this case, the first threshold value is set to the first frequency f １ 0 and the second frequency f ２ The difference from 0 is f ｔ１ For example, the difference between the initial frequencies of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 (f ２ 0-f １ 0) is 5 kHz. In this case, the first threshold value is f ｔ１ +(f ２ 0-f １ 0) is set to 100 kHz.

[0101] As described above, the life specification unit 174 determines the oscillation frequency f １ 2 and the oscillation frequency f of the second piezoelectric vibrator 33 ２ 1 (or f ２ 2), the life of the first piezoelectric vibrator 31 can be determined. １ 2 and the oscillation frequency f of the second piezoelectric vibrator 33 ２ 1 (or f ２ 2) may be compared after temperature correction. Alternatively, if the temperature characteristics of the two piezoelectric vibrators are almost the same, the lifespan determination unit 174 may not need to perform temperature correction of the oscillation frequency. In this way, the lifespan determination unit 174 can more easily determine the lifespan of the first piezoelectric vibrator 31.

[0102] The memory circuit 16 of the sensor module 10 may further store information about a first threshold value based on the initial oscillation frequency information, thereby enabling the control device 100 to quickly acquire information used to determine the lifespan of the piezoelectric vibrator even if, for example, the connected sensor module 10 is replaced.

[0103] Furthermore, the memory circuit 16 of the sensor module 10 may further store information on a second threshold value having an absolute value smaller than the first threshold value. For example, the life determination unit 174 determines that the life of the first piezoelectric vibrator 31 is nearing the end when the absolute value of the difference frequency between the oscillation frequency of the first piezoelectric vibrator 31 and the oscillation frequency of the second piezoelectric vibrator 33 becomes equal to or greater than the second threshold value.

[0104] This allows the user to know when it is soon time to replace the sensor module 10. For example, if there are plans to deposit a semiconductor material with a thicker film thickness, the user can consider replacing the sensor module 10 early, thereby reducing the possibility that the sensor module 10 will be unable to function as a sensor while the semiconductor manufacturing equipment is depositing material.

[0105] In the above second configuration example of the sensor module 10, one of the two piezoelectric vibrators is used as a detection piezoelectric vibrator and the other is used as a reference piezoelectric vibrator, but this is not limited to this. In addition, the sensor module 10 may use the piezoelectric vibrator used for detection as a reference piezoelectric vibrator, and the piezoelectric vibrator used for reference as a detection piezoelectric vibrator. Such a sensor module 10 will now be described.

[0106] <Third Configuration Example of Sensor Module 10> Fig. 6 shows a third configuration example of the sensor module 10 according to this embodiment. In the sensor module 10 of the third configuration example, parts that operate in substantially the same manner as the sensor module 10 of the second configuration example shown in Fig. 5 are assigned the same reference numerals, and redundant explanations will be omitted.

[0107] The sensor module 10 of the third configuration example is configured so that the electrode cover 35 can be switched between covering the first electrode 32 and covering the second electrode 34. Fig. 6 shows an example in which the electrode cover 35 is a plate-shaped member that slides to switch between covering the first electrode 32 and covering the second electrode 34. Alternatively, the electrode cover 35 may be an openable and closable lid-like member, door-like member, shutter-like member, or the like that is provided on the cover 20.

[0108] The electrode cover 35 preferably has an actuator or the like and is configured to be switchable by an electric signal between a state covering the first electrode 32 and a state covering the second electrode 34. Alternatively, the electrode cover 35 may be configured to be manually switched.

[0109] For example, when the electrode cover 35 covers the second electrode 34 to prevent deposits from accumulating on the surface of the second electrode 34, the electrode cover 35 exposes the first electrode 32. In this case, when the first piezoelectric vibrator 31 is driven by the oscillation circuit 15, it oscillates at a frequency corresponding to the thickness of the deposits accumulated on the surface of the first electrode 32, and operates as a detection piezoelectric vibrator that detects the thickness of the deposits. The second piezoelectric vibrator 33 operates as a reference piezoelectric vibrator.

[0110] Furthermore, when the electrode cover 35 covers the first electrode 32 to prevent deposits from accumulating on the surface of the first electrode 32, the electrode cover 35 exposes the second electrode 34. In this case, when the second piezoelectric vibrator 33 is driven by the oscillation circuit 15, it oscillates at a frequency corresponding to the thickness of the deposits accumulated on the surface of the second electrode 34, and operates as a detection piezoelectric vibrator that detects the thickness of the deposits. The first piezoelectric vibrator 31 operates as a reference piezoelectric vibrator.

[0111] The first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 may operate as detection piezoelectric vibrators, and then operate as reference piezoelectric vibrators after deposits have accumulated on the electrodes. In this case, the reference frequency of the first piezoelectric vibrator 31 or the second piezoelectric vibrator 33 corresponds to the thickness of the deposits accumulated on the surface of the electrodes. This allows the sensor module 10 to be used by switching between the detection piezoelectric vibrator and the reference piezoelectric vibrator, thereby extending its lifespan.

[0112] For example, when the electrode cover 35 switches to a state in which it covers the first electrode 32 after the first piezoelectric vibrator 31 is driven by the oscillation circuit 15, the memory circuit 16 of the sensor module 10 in the third configuration example desirably stores, as final oscillation frequency information, the oscillation frequency measured by oscillating the first piezoelectric vibrator 31. This allows the control device 100 to quickly obtain information about the reference frequency when using the first piezoelectric vibrator 31 as a reference piezoelectric vibrator.

[0113] The memory circuit 16 may also store information indicating whether the first piezoelectric vibrator 31 and / or the second piezoelectric vibrator 33 is a detection piezoelectric vibrator or a reference piezoelectric vibrator. The memory circuit 16 may also store information indicating that when the first piezoelectric vibrator 31 and / or the second piezoelectric vibrator 33 operates as a detection piezoelectric vibrator and reaches the end of its life, it cannot be used as a detection piezoelectric vibrator. This allows the control device 100 to quickly determine which of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 is to be used as a detection (reference) vibrator, even when, for example, a sensor module 10 that is in use is connected.

[0114] <Operation of control device 100 using sensor module 10 of third configuration example> The control device 100 shown in Fig. 3 can also use the sensor module 10 of the third configuration example. In this case, the control device 100 is connected to the sensor module 10 of the third configuration example via the interface 120. Note that the operations of the frequency measurement unit 140 and the memory control unit 172 may be the same as those of the control device 100 using the sensor module 10 of the second configuration example, and therefore a description thereof will be omitted here.

[0115] It is preferable that the control unit 170 further includes an instruction unit that instructs the sensor module 10 to switch the electrode cover. Thus, when the electrode cover 35 of the sensor module 10 is configured to be switchable between a state covering the first electrode 32 and a state covering the second electrode 34 by an electrical signal, the control device 100 can supply a control signal instructing the switching operation to the sensor module 10 to switch the electrode cover 35.

[0116] The thickness determination unit 173 determines the thickness of the deposit deposited on the surface of the electrode of the detection piezoelectric vibrator out of the first electrode 32 of the first piezoelectric vibrator 31 and the second electrode 34 of the second piezoelectric vibrator 33, based on the result of measurement by the frequency measurement unit 140. For example, when the information read out from the memory circuit 16 by the memory control unit 172 includes information about the detection piezoelectric vibrator, the thickness determination unit 173 determines the thickness of the deposit deposited on the surface of the electrode of the detection piezoelectric vibrator.

[0117] Alternatively, information about the detection piezoelectric vibrator may be stored in the memory unit 150 of the control device 100. In this case, the thickness determination unit 173 determines the thickness of deposits accumulated on the surfaces of the electrodes of the detection piezoelectric vibrator based on the information read from the memory unit 150. Furthermore, for example, when the instruction unit instructs the sensor module 10 to switch the electrode cover, the thickness determination unit 173 determines the thickness of deposits accumulated on the surfaces of the electrodes exposed by the instruction from the instruction unit. The operation of determining the thickness of deposits by the thickness determination unit 173 is similar to the operation of the control device 100 using the sensor module 10 of the second configuration example, and therefore will not be described here.

[0118] The lifespan specifying unit 174 specifies the lifespan of the detection piezoelectric vibrator based on the initial oscillation frequency information read out by the memory control unit 172 from the memory circuit 16 and the measurement result by the frequency measurement unit 140. For example, if the reference piezoelectric vibrator has not been used as a detection piezoelectric vibrator in the past, the lifespan specifying unit 174 specifies the lifespan of the detection piezoelectric vibrator in the same manner as the operation of the lifespan specifying unit 174 of the control device 100 using the sensor module 10 of the second configuration example. As described above, the lifespan specifying unit 174 specifies the detection piezoelectric vibrator based on the information read out from the memory circuit 16 of the sensor module 10 or the information read out from the memory unit 150 of the control device 100.

[0119] Furthermore, when the instruction unit instructs the sensor module 10 to switch the electrode cover, the lifespan determination unit 174 determines the lifespan of the piezoelectric vibrator having the electrode exposed by the instruction from the instruction unit, out of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33. In this case, the lifespan determination unit 174 does not use the first threshold value based on the initial oscillation frequency information described above, because the reference piezoelectric vibrator has been used as a detection piezoelectric vibrator in the past. Instead, the lifespan determination unit 174 uses a threshold value based on the final oscillation frequency, which is the oscillation frequency of the reference piezoelectric vibrator.

[0120] For example, the first piezoelectric vibrator 31 is a reference piezoelectric vibrator that has been used as a detection piezoelectric vibrator in the past, and the final oscillation frequency is f １ In other words, for example, the first piezoelectric vibrator 31 has a frequency |f １ 3-f ２ 1 | (or |f １ 3-f ２ 2|) is equal to or greater than the first threshold, the life specification unit 174 specifies that the detection piezoelectric vibrator has reached the end of its life, and the instruction unit switches the vibrator to a reference piezoelectric vibrator.

[0121] In this case, the measurement result of the oscillation frequency of the second piezoelectric vibrator 33 used as the vibrator for detection is f ２ The life specification unit 174 determines the oscillation frequency f of the second piezoelectric vibrator 33 for detection. ２ 3 and the oscillation frequency f of the first piezoelectric vibrator 31 １ 3 (final oscillation frequency) ２ 3-f １ 3) becomes equal to or less than the third threshold based on the initial oscillation frequency information, the life of the second piezoelectric vibrator 33 is determined. Note that the oscillation frequency of the first piezoelectric vibrator 31 for reference may change depending on the ambient temperature, etc. Therefore, the oscillation frequency of the first piezoelectric vibrator 31 for reference is further measured to determine the life of the second piezoelectric vibrator 33. １ It may also be 3.

[0122] For example, the second piezoelectric vibrator 33 has an oscillation frequency f ２ 3 is the initial frequency f ２Here, the frequency 97 kHz, which indicates the index of the end of the life of the second piezoelectric vibrator 33, is defined as f ｔ２ In this case, the third threshold is f ｔ２ and a frequency f that indicates the end of the life of the first piezoelectric vibrator 31. ｔ１ The difference f ｔ１ -f ｔ２ (=-2 Hz).

[0123] The first frequency f, which is the initial frequency of the first piezoelectric vibrator 31, １ 0 and the second frequency f which is the initial frequency of the second piezoelectric vibrator 33. ２ 0 may not match due to individual differences in the vibrator. In this case, the third threshold value is set to the first frequency f １ 0 and the second frequency f ２ The difference from 0 is f ｔ１ -f ｔ２ For example, the difference between the initial frequencies of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 (f ２ 0-f １ 0) is 5 kHz. In this case, the first threshold value is f ｔ１ -f ｔ２ +(f ２ 0-f １ 0) is set to 3 kHz.

[0124] As described above, the life specification unit 174 determines the oscillation frequency f １ 3 and the oscillation frequency f of the second piezoelectric vibrator 33 ２ 3, the life of the first piezoelectric vibrator 31 can be determined. １ 3 and the oscillation frequency f of the second piezoelectric vibrator 33 ２ 3 may be compared after temperature correction. Alternatively, if the temperature characteristics of the two piezoelectric vibrators are almost the same, the lifespan determination unit 174 may not need to perform temperature correction of the oscillation frequency. This allows the lifespan determination unit 174 to more easily determine the lifespan of the first piezoelectric vibrator 31.

[0125] Although the sensor module 10 of the present embodiment has been described above as an example having two piezoelectric vibrators, the present invention is not limited to this. Alternatively, a module having a plurality of sensor modules 10 may be used as the sensor module. Such a module will be described next.

[0126] <Fourth Configuration Example of Sensor Module> Fig. 7 shows a fourth configuration example of the sensor module according to this embodiment as a sensor module 40. The sensor module 40 of the fourth configuration example is a module including a plurality of the sensor modules 10 of the third configuration example shown in Fig. 6. The sensor module 40 of the fourth configuration example further includes a fixed substrate 41 and a moving section 42.

[0127] 7A shows a planar configuration example of the sensor module 40 with the electrode cover 35 removed. The sensor module 40 of the fourth configuration example has a plurality of sensor modules 10 of the third configuration example provided on a fixed substrate 41. The fixed substrate 41 is a plate-shaped member on which the sensor modules 10 are arranged. The fixed substrate 41 may be formed integrally with the substrate 11 of the sensor module 10.

[0128] 7A, four modules, namely, sensor module 10a, sensor module 10b, sensor module 10c, and sensor module 10d, are the sensor modules 10 of the third configuration example. In other words, the sensor module 40 of the fourth configuration example includes a plurality of combinations of first piezoelectric vibrators 31 and second piezoelectric vibrators 33.

[0129] For example, the first electrodes 32 of the multiple first piezoelectric vibrators 31 are arranged along the circumference of a first circle having a predetermined radius on the upper surface of the fixed substrate 41. Fig. 7(a) shows an example in which four first electrodes 32 are arranged at approximately equal angular intervals (90-degree intervals) on the circumference of the first circle. Similarly, the second electrodes 34 of the multiple second piezoelectric vibrators 33 are arranged along the circumference of a second circle concentric with the first circle on the upper surface of the fixed substrate 41. Fig. 7(a) shows an example in which four second electrodes 34 are arranged at approximately equal angular intervals (90-degree intervals) on the circumference of the second circle.

[0130] Fig. 7B shows a planar configuration example of a sensor module 40 equipped with an electrode cover 35. In Fig. 7B, the portion of the sensor module 10a covered by the electrode cover 35, the first circle, and the second circle are indicated by dotted lines. The electrode cover 35 of the sensor module 40 of the fourth configuration example is provided as a single cover common to a combination of a plurality of first piezoelectric vibrators 31 and second piezoelectric vibrators 33.

[0131] The moving unit 42 moves the electrode cover 35. The moving unit 42 has an actuator or the like, and moves the electrode cover 35 based on a control signal received from outside the sensor module 40 (for example, from an instruction unit of the control device 100, etc.). In other words, the electrode cover 35 is configured in a movable plate shape while covering the plurality of first electrodes 32 and the plurality of second electrodes 34. Figure 7(b) shows an example in which the electrode cover 35 is formed in a disk shape and is provided rotatably by the moving unit 42 while covering the plurality of first piezoelectric vibrators 31 and the plurality of second piezoelectric vibrators 33. The electrode cover 35 has a first opening 43 and a second opening 44.

[0132] The first opening 43 is an opening for exposing one of the plurality of first electrodes 32. The first opening 43 is arranged so that, as the electrode cover 35 moves, it moves sequentially to a plurality of positions corresponding to the plurality of first electrodes 32, exposing the plurality of first electrodes 32 one by one.

[0133] In the electrode cover 35, the first opening 43 is provided on the circumference of a circle that coincides in plan view with the first circle of the fixed substrate 41. The moving unit 42 rotates the electrode cover 35 about an axis that passes perpendicularly through the center of the first circle in plan view, thereby exposing one of the multiple first electrodes 32 from the first opening 43. Figure 7(b) shows an example in which the first opening 43 exposes the first electrode 32a of the sensor module 10a.

[0134] The second opening 44 is an opening for exposing one of the plurality of second electrodes 34. The second opening 44 is arranged so that, as the electrode cover 35 moves, it moves sequentially to a plurality of positions corresponding to the plurality of second electrodes 34, exposing the plurality of second electrodes 34 one by one.

[0135] In the electrode cover 35, the second opening 44 is provided on the circumference of a circle that coincides in plan view with the second circle of the fixed substrate 41. The moving unit 42 rotates the electrode cover 35 about an axis that passes through the center of the first circle in plan view, thereby exposing one of the multiple second electrodes 34 from the second opening 44.

[0136] The first opening 43 is arranged to move to a position that does not expose the first electrode 32 when the second opening 44 moves to a position that exposes the second electrode 34. Similarly, the second opening 44 is arranged to move to a position that does not expose the second electrode 32 when the first opening 43 moves to a position that exposes the first electrode 32. When the moving unit 42 rotates the electrode cover 35, the electrode cover 35 exposes one first electrode 32 from the first opening 43 or one second electrode 34 from the second opening 44, among the multiple first electrodes 32 and multiple second electrodes 34.

[0137] 7B shows an example in which the first electrode 32a of the sensor module 10a is exposed through the first opening 43, and none of the electrodes is exposed through the second opening 44. In the sensor module 40 in this state, the first piezoelectric vibrator 31a of the sensor module 10a can function as a detection piezoelectric vibrator, and the second piezoelectric vibrator 33a of the sensor module 10a can function as a reference piezoelectric vibrator.

[0138] Figure 8 shows an example in which the electrode cover 35 of the sensor module 40 of the fourth configuration example shown in Figure 7 is rotated. Figure 8(a) shows an example in which the electrode cover 35 of the sensor module 40 shown in Figure 7(b) is rotated 45 degrees. Here, the rotation angle of the electrode cover 35 is half the angle of the interval at which the first electrodes 32 and the second electrodes 34 are arranged on the circumference.

[0139] 8A, it can be seen that the first opening 43 does not expose any electrodes, and the second opening 44 exposes the second electrode 34a of the sensor module 10a. In the sensor module 40 in this state, the first piezoelectric vibrator 31a of the sensor module 10a can operate as a reference piezoelectric vibrator, and the second piezoelectric vibrator 33a of the sensor module 10a can operate as a detection piezoelectric vibrator.

[0140] Figure 8(b) shows an example in which the electrode cover 35 of the sensor module 40 shown in Figure 8(a) is rotated another 45 degrees. From Figure 8(b), it can be seen that the first opening 43 exposes the first electrode 32b of the next sensor module 10b, and the second opening 44 exposes no electrodes. In this state of the sensor module 40, the first piezoelectric vibrator 31b of the sensor module 10b can function as a reference piezoelectric vibrator, and the second piezoelectric vibrator 33b of the sensor module 10b can function as a detection piezoelectric vibrator.

[0141] As described above, the sensor module 40 can sequentially expose the electrodes of the plurality of piezoelectric vibrators one by one, and the piezoelectric vibrators having the exposed electrodes can function as detection piezoelectric vibrators. Note that the reference piezoelectric vibrator may be any piezoelectric vibrator covered by the electrode cover 35, and the plurality of piezoelectric vibrators may be alternately used as reference piezoelectric vibrators one by one, or alternatively, a predetermined piezoelectric vibrator may be used as the reference piezoelectric vibrator.

[0142] In the sensor module 40 of the fourth configuration example, the memory circuit 16 of the sensor module 10 having a piezoelectric vibrator that operates as a detection (and / or reference) piezoelectric vibrator may also store information indicating the detection (and / or reference) piezoelectric vibrator. Furthermore, the memory circuit 16 may store information indicating that the first piezoelectric vibrator 31 and / or the second piezoelectric vibrator 33 can no longer be used as a detection piezoelectric vibrator when the first piezoelectric vibrator 31 and / or the second piezoelectric vibrator 33 has reached the end of its life while operating as a detection piezoelectric vibrator. Furthermore, this information may be stored in the memory unit 150 of the control device 100.

[0143] 3 can also use the sensor module 40 of the fourth configuration example. In this case, the control device 100 is connected to the sensor module 40 of the fourth configuration example via the interface 120. Note that the memory control unit 172 only needs to be able to access the memory circuits 16 of the multiple sensor modules 10 and read the information stored in the memory circuits 16.

[0144] The control unit 170 further has an instruction unit that instructs the movement unit 42 of the sensor module 40 to operate the electrode cover 35. The instruction unit instructs the movement of the electrode cover 35 so that the first opening 43 is located at a position corresponding to the first piezoelectric vibrator 31 of one combination of a plurality of first piezoelectric vibrators 31 and second piezoelectric vibrators 33, or so that the second opening 44 is located at a position corresponding to the second piezoelectric vibrator 33 of one combination.

[0145] Here, one combination of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 is, for example, a combination of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 included in one sensor module 10. Furthermore, one combination of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 may be a combination of the first piezoelectric vibrator 31 included in one sensor module 10 and the second piezoelectric vibrator 33 included in another sensor module 10 different from the one sensor module 10.

[0146] The control unit 170 sends a control signal to the oscillation circuit 15 corresponding to one combination of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 to drive the one combination of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33. The frequency measurement unit 140 measures the oscillation frequency of the one combination of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33 based on the oscillation frequency signal output by the oscillation circuit 15.

[0147] The thickness determination unit 173 determines the thickness of the deposits accumulated on the surface of the electrode of the detection piezoelectric vibrator that is exposed in response to an instruction from the instruction unit, out of the first electrode 32 of the first piezoelectric vibrator 31 and the second electrode 34 of the second piezoelectric vibrator 33, based on the result of measurement by the frequency measurement unit 140. The operation of the thickness determination unit 173 to determine the thickness may be the same as the operation of the control device 100 described above, and therefore a description thereof will be omitted here.

[0148] The life specifying unit 174 specifies the life of the piezoelectric vibrator of the detection piezoelectric vibrator having the electrode exposed in response to an instruction from the instruction unit, out of the first piezoelectric vibrator 31 and the second piezoelectric vibrator 33, based on the initial oscillation frequency information read out by the memory control unit 172 from the storage circuit 16 and the measurement result by the frequency measurement unit 140. The operation of specifying the life of the life specifying unit 174 may be the same as the operation of the control device 100 described above, and therefore a description thereof will be omitted here.

[0149] The control device 100 according to the present embodiment described above can use the sensor module 40 of the fourth configuration example to easily replace the detection piezoelectric vibrator while determining the lifespan of the multiple piezoelectric vibrators mounted on the sensor module 40. Note that, although the sensor module 40 of the fourth configuration example has been described as having the multiple first electrodes 32 and multiple second electrodes arranged concentrically, this is not limiting. The multiple first electrodes 32 and multiple second electrodes may also be arranged linearly.

[0150] <Fifth Configuration Example of Sensor Module> Fig. 9 shows a fifth configuration example of the sensor module 40 according to this embodiment. In the sensor module 40 of the fifth configuration example, parts that operate in substantially the same manner as the sensor module 40 of the fourth configuration example shown in Fig. 7 are assigned the same reference numerals, and redundant explanations will be omitted.

[0151] 9A shows a plan view of a configuration example of the sensor module 40 without the electrode cover 35. The sensor module 40 of the fifth configuration example has a plurality of sensor modules 10 of the third configuration example linearly arranged on a fixed substrate 41.

[0152] 9B shows a planar configuration example of the sensor module 40 with the electrode cover 35 attached. In FIG. 9B, the portion of the sensor module 10a covered by the electrode cover 35 is indicated by a dotted line. The first opening 43 exposes the first electrode 32a of the sensor module 10a, while the second opening 44 exposes none of the electrodes. When the electrode cover 35 moves in the −Y direction and the second opening 44 exposes the second electrode 34a of the sensor module 10a, the first opening 43 is positioned so that none of the electrodes are exposed.

[0153] Furthermore, when the electrode cover 35 is moved in the −Y direction and the first opening 43 exposes the first electrode 32b of the sensor module 10b, the second opening 44 is positioned so as not to expose any of the electrodes. In this way, the sensor module 40 of the fifth configuration example can sequentially expose the electrodes of the multiple piezoelectric vibrators one by one, and the piezoelectric vibrators having the exposed electrodes can operate as piezoelectric vibrators for detection.

[0154] As described above, even in the sensor module 40 of the fifth configuration example, the control device 100 can easily replace the detection piezoelectric vibrator while determining the lifespan of the multiple piezoelectric vibrators mounted on the sensor module 40. In the sensor module 40 according to this embodiment, it is desirable that the memory circuit 16 of at least the piezoelectric vibrator used last stores a second threshold value for determining that the end of life is approaching, in addition to the first threshold value used for determining the lifespan. This allows the user to know that the time to replace the entire sensor module 40 is approaching.

[0155] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments.

[0156] REFERENCE SIGNS LIST 1 semiconductor manufacturing equipment 2 chamber 3 stage 4 film forming equipment 5 connector 10 sensor module 11 substrate 12 piezoelectric vibrator 13 electrode 14 heater circuit 15 oscillation circuit 16 memory circuit 17 base member 18 coupling socket 19 temperature sensor 20 cover 30 connection cable 31 first piezoelectric vibrator 32 first electrode 33 second piezoelectric vibrator 34 second electrode 35 electrode cover 40 sensor module 41 fixed substrate 42 moving unit 43 first opening 44 second opening 100 control device 110 input unit 120 interface 130 power supply unit 140 frequency measurement unit 150 memory unit 160 display unit 170 control unit 171 acquisition unit 172 memory control unit 173 thickness determination unit 174 life determination unit 175 Display control unit

Claims

1. A sensor module comprising: a first piezoelectric vibrator having a first electrode; a second piezoelectric vibrator having a second electrode; an electrode cover covering one of the first electrode and the second electrode; an oscillation circuit that drives each of the first piezoelectric vibrator and the second piezoelectric vibrator to oscillate; and a memory circuit that stores, as initial oscillation frequency information, information corresponding to a first oscillation frequency measured by oscillating the first piezoelectric vibrator when the first piezoelectric vibrator is shipped, and a second oscillation frequency measured by oscillating the second piezoelectric vibrator when the second piezoelectric vibrator is shipped; wherein, when driven by the oscillation circuit, at least one of the first piezoelectric vibrator and the second piezoelectric vibrator, whose electrodes are not covered by the electrode cover, oscillates at a frequency corresponding to a thickness of deposits accumulated on the surfaces of the electrodes that are exposed and not covered by the electrode cover.

2. The sensor module according to claim 1, wherein the memory circuit further stores information on transducer identification numbers for identifying the first piezoelectric transducer and the second piezoelectric transducer.

3. The sensor module described in claim 1, wherein the electrode cover is switchable between a state covering the first electrode and a state covering the second electrode, the first piezoelectric vibrator oscillates at a frequency corresponding to a thickness of deposits accumulated on the surface of the first electrode when driven by the oscillation circuit, and the second piezoelectric vibrator oscillates at a frequency corresponding to a thickness of deposits accumulated on the surface of the second electrode when driven by the oscillation circuit, and the electrode cover exposes the first electrode when covering the second electrode to prevent deposits from accumulating on the surface of the second electrode, and exposes the second electrode when covering the first electrode to prevent deposits from accumulating on the surface of the first electrode.

4. The sensor module described in claim 3, wherein when the electrode cover is switched to a state covering the first electrode after the first piezoelectric vibrator is driven by the oscillation circuit, the memory circuit stores the oscillation frequency measured by oscillating the first piezoelectric vibrator as final oscillation frequency information.

5. A sensor module as described in claim 3, comprising a plurality of combinations of the first piezoelectric vibrators and the second piezoelectric vibrators, the electrode cover being configured in the shape of a movable plate while covering a plurality of the first electrodes and a plurality of the second electrodes, the electrode cover having a first opening for exposing one of the first electrodes and a second opening for exposing one of the second electrodes, the first opening being arranged so as to move sequentially to a plurality of positions corresponding to the plurality of first electrodes as the electrode cover moves, thereby exposing the plurality of first electrodes one by one, the second opening being arranged so as to move sequentially to a plurality of positions corresponding to the plurality of second electrodes as the electrode cover moves, thereby exposing the plurality of second electrodes one by one, and further comprising a moving unit for moving the electrode cover.

6. The sensor module described in claim 5, wherein the multiple first piezoelectric vibrators are arranged along the circumference of a first circle of a predetermined radius on the upper surface of a fixed substrate, the multiple second piezoelectric vibrators are arranged along the circumference of a second circle concentric with the first circle on the upper surface of the fixed substrate, the electrode cover is rotatably provided while covering the multiple first piezoelectric vibrators and the multiple second piezoelectric vibrators, in the electrode cover, the first opening is provided on the circumference of a circle coinciding with the first circle in a planar view, and the second opening is provided on the circumference of a circle coinciding with the second circle in a planar view, and the moving unit exposes one of the multiple first electrodes and the multiple second electrodes from the first opening or one of the multiple first electrodes from the second opening by rotating the electrode cover around an axis that passes perpendicularly through the center of the first circle in a planar view.

7. A measurement system comprising: the sensor module according to any one of claims 1 to 6; and a control device connected to the sensor module, wherein the control device has: a memory control unit capable of accessing the memory circuit of the sensor module and reading information stored in the memory circuit; a frequency measurement unit that measures the oscillation frequencies of the first piezoelectric vibrator and the second piezoelectric vibrator based on an oscillation frequency signal output by the oscillation circuit; a thickness determination unit that determines a thickness of the deposit deposited on a surface of an electrode that is exposed and not covered by the electrode cover, of the first electrode of the first piezoelectric vibrator and the second electrode of the second piezoelectric vibrator, based on a measurement result by the frequency measurement unit; and a lifetime determination unit that determines a lifetime of the piezoelectric vibrator that has an electrode that is exposed and not covered by the electrode cover, of the first piezoelectric vibrator and the second piezoelectric vibrator, based on the initial oscillation frequency information read out from the memory circuit by the memory control unit and the measurement result by the frequency measurement unit.

8. The measurement system described in claim 7, wherein the life determination unit determines the life of the first piezoelectric vibrator in response to an absolute value of a differential frequency between the oscillation frequency of the first piezoelectric vibrator and the oscillation frequency of the second piezoelectric vibrator becoming equal to or greater than a first threshold value based on the initial oscillation frequency information.

9. The measurement system according to claim 8, wherein the memory circuit of the sensor module further stores information of the first threshold value based on the initial oscillation frequency information.

10. The measurement system described in claim 8, wherein the memory circuit of the sensor module further stores information on a second threshold value having an absolute value smaller than the first threshold value, and the life determination unit determines that the first piezoelectric vibrator is nearing the end of its life in response to the absolute value of the difference frequency between the oscillation frequency of the first piezoelectric vibrator and the oscillation frequency of the second piezoelectric vibrator becoming equal to or greater than the second threshold value.

11. A measurement system comprising: the sensor module according to claim 3 or 4; and a control device connected to the sensor module, wherein the control device has: a memory control unit capable of accessing the memory circuit of the sensor module and reading information stored in the memory circuit; an instruction unit for instructing the sensor module to switch the electrode cover; a frequency measurement unit for measuring the oscillation frequencies of the first piezoelectric vibrator and the second piezoelectric vibrator based on an oscillation frequency signal output by the oscillation circuit; a thickness determination unit for determining a thickness of the deposit deposited on a surface of an electrode exposed at the instruction of the instruction unit, of the first electrode of the first piezoelectric vibrator and the second electrode of the second piezoelectric vibrator, based on a result of measurement by the frequency measurement unit; and a lifetime determination unit for determining a lifetime of the piezoelectric vibrator having an electrode exposed at the instruction of the instruction unit, of the first piezoelectric vibrator and the second piezoelectric vibrator, based on initial oscillation frequency information read out from the memory circuit by the memory control unit and the result of measurement by the frequency measurement unit.

12. A sensor module according to claim 5 or 6, comprising: a control device connected to the sensor module, the control device comprising: a memory control unit capable of accessing the storage circuit of the sensor module and reading information stored in the storage circuit; an instruction unit for instructing movement of the electrode cover so that the first opening is located at a position corresponding to the first piezoelectric vibrator of one combination of a plurality of combinations of the first piezoelectric vibrators and the second piezoelectric vibrators, or the second opening is located at a position corresponding to the second piezoelectric vibrator of one combination; a frequency measurement unit for measuring the oscillation frequency of the first piezoelectric vibrator and the second piezoelectric vibrator of the one combination based on an oscillation frequency signal output by the oscillation circuit; and a thickness determination unit for determining a thickness of the deposit deposited on a surface of an electrode exposed by an instruction from the instruction unit, of the first electrode of the first piezoelectric vibrator and the second electrode of the second piezoelectric vibrator, based on a result of measurement by the frequency measurement unit. a lifetime determination unit that determines a lifetime of one of the first piezoelectric vibrator and the second piezoelectric vibrator that has an electrode exposed by instruction from the instruction unit, based on the initial oscillation frequency information read out by the memory control unit from the memory circuit and the result of measurement by the frequency measurement unit.