Sensor device

Abstract

To provide a sensor device capable of ensuring high detection precision even under an ultra-low-rate film formation condition.SOLUTION: A sensor device according to one embodiment of the present invention has a piezoelectric vibrator and a support. The piezoelectric vibrator includes: a vibrator body; first and second front electrode sections formed on the surface of the vibrator body; and first and second rear electrode sections formed on the back of the vibrator body and respectively opposing the first and second front electrode sections. The support includes: a hollow section for exposing the surface of the vibrator body; a support surface for supporting the piezoelectric vibrator such that it can be vibrated; and a shielding plate for exposing the first front electrode section to the hollow section and shielding the second front electrode section from the hollow section. The shielding plate is composed of a material having a transmittance of 40% or higher relative to infrared rays within a range of 0.5 times or more and 3 times of less of its peak wavelength from among infrared rays impinging on the hollow section.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a sensor device that measures the amount of attached material in a vacuum or in the atmosphere from the amount of change in the resonance frequency of a quartz oscillator, and calculates the mass of the attached material, film thickness, film formation rate, etc. [Background technology]

[0002] Conventionally, in film-forming equipment such as vacuum deposition equipment, a technique called QCM (Quartz Crystal Microbalance) that uses a quartz oscillator to measure minute changes in mass has been used to measure the thickness and deposition rate of a film formed on a substrate. This method utilizes the fact that the resonant frequency of a quartz oscillator placed in a chamber decreases due to an increase in mass caused by the adhesion of a deposition material. Therefore, it is possible to measure the thickness and deposition rate of a film by measuring the change in the resonant frequency of the quartz oscillator.

[0003] For example, Patent Document 1 discloses a detection device including a quartz crystal resonator having excitation electrodes formed on both the front and back sides of a quartz crystal substrate, an excitation means for applying a voltage between the front excitation electrode and the back excitation electrode to excite the quartz crystal resonator, and a detection means for detecting impurities from the change in the resonant frequency of the quartz crystal resonator. The front excitation electrode has a first electrode portion and a second electrode portion that are isolated from each other, and a cover body is arranged on the front side of the quartz crystal substrate to shield the first electrode portion from the vacuum atmosphere and to allow the passage of heat rays emitted from components in the vacuum chamber, and the detection means is configured to detect impurities from the difference between a first change in the resonant frequency detected by applying a voltage between the first electrode portion and the back excitation electrode and a second change in the resonant frequency detected by applying a voltage between the second electrode portion and the back excitation electrode. This makes it possible to accurately detect deposits on the surface of the quartz crystal resonator without being affected by temperature drift of the resonant frequency of the quartz crystal resonator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-190455 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the detection device described in Patent Document 1, the amount of heat rays incident on the first electrode and the second electrode varies depending on the heat ray transmission characteristics of the cover body that shields the first electrode, which may prevent highly accurate film thickness detection. This problem is more likely to occur under film formation conditions in which the mass increase rate per unit time is extremely small, such as during ultra-low rate film formation in which the film formation rate is extremely low.

[0006] In view of the above circumstances, an object of the present invention is to provide a sensor device that can ensure high detection accuracy even under ultra-low rate film formation conditions. [Means for solving the problem]

[0007] A sensor device according to an embodiment of the present invention includes a piezoelectric vibrator and a support. The piezoelectric vibrator has a vibrator body, first and second surface electrode portions formed on a surface of the vibrator body, and first and second back surface electrode portions formed on a back surface of the vibrator body and facing the first and second surface electrode portions, respectively. The support body has a hollow portion that exposes the surface of the vibrator body, a support surface that supports the piezoelectric vibrator so that it can vibrate, and a shielding plate that exposes the first surface electrode portion to the hollow portion and shields the second surface electrode portion from the hollow portion. The shielding plate is made of a material having a transmittance of 40% or more for infrared rays in a wavelength range of 0.5 to 3 times the peak wavelength of the infrared rays incident on the hollow portion.

[0008] When a first change amount is a time change in the resonant frequency of the piezoelectric vibrator when an AC voltage is applied between the first surface electrode portion and the first back electrode portion, and a second change amount is a time change in the resonant frequency of the piezoelectric vibrator when an AC voltage is applied between the second surface electrode portion and the second back electrode portion, it is preferable that a ratio of the second change amount to the first change amount when infrared light is incident on the hollow portion is 40% or more.

[0009] A ratio of the second amount of change to the first amount of change may be 60% or more.

[0010] The shielding plate is, for example, a silicon plate having a thickness of 0.5 mm or less. Effect of the Invention

[0011] According to the present invention, high detection accuracy can be ensured even under ultra-low rate film formation conditions. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing a film forming apparatus including a sensor device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing an example of the configuration of a measurement unit in the film forming apparatus. [Diagram 3] 2 is a typical equivalent circuit of the above sensor device. [Figure 4] FIG. 2 is a schematic cross-sectional view showing a configuration of the sensor device. [Diagram 5] FIG. 2 is an exploded cross-sectional view of the sensor device. [Figure 6] FIG. 2 is an enlarged cross-sectional view of a main part of the sensor device. [Figure 7] 3 is a top view of a piezoelectric vibrator in the sensor device. FIG. [Figure 8] FIG. 4 is a bottom view of the support as viewed from the piezoelectric vibrator side. [Figure 9] FIG. 2 is a top view of the piezoelectric vibrator as viewed from the support side. [Figure 10]1 shows an experimental result showing the change in frequency of a piezoelectric vibrator over time (rate conversion value) when the temperature of the deposition source is increased stepwise. [Figure 11] FIG. 11 is a conceptual diagram showing the lower limit of measurement in the film formation apparatus used in the experiment of FIG. 10, in which the horizontal axis represents the deposition source temperature and the vertical axis represents the film formation rate. [Figure 12] FIG. 1 is a diagram showing the infrared transmission characteristics of Si, Ge, ZnS, and ZnSe. [Figure 13] 13 is an experimental result showing the change in the resonant frequency of a piezoelectric vibrator over time due to differences in the constituent material and thickness of the shielding plate. [Figure 14] 13 is an experimental result showing the time change in the ratio ΔF0 of the second change amount to the first change amount when the shielding plate is a quartz plate having a thickness of 1 mm and 0.062 mm, respectively. [Figure 15] The figure shows experimental results showing the change in ΔF0 over time when the shielding plate 63 is a Si plate having a thickness of 0.5 mm, 0.05 mm, and 0.06 mm. [Figure 16] 13 is a cross-sectional view of a sensor device showing a modified example of the configuration of the shielding plate. FIG. [Figure 17] 13 is a cross-sectional view of a sensor device showing another modified example of the configuration of the shielding plate. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a thickness sensor for a film forming apparatus will be described as an example of the sensor device.

[0014] 1 is a schematic cross-sectional view showing a film formation apparatus including a sensor device according to the present embodiment. In the present embodiment, a vacuum deposition apparatus will be taken as an example of the film formation apparatus 10. First, a basic configuration of the film formation apparatus 10 will be described.

[0015] [Film forming equipment] The film forming apparatus 10 includes a vacuum chamber 11 which is a film forming chamber, a deposition source 12 arranged inside the vacuum chamber 11, a stage 13 facing the deposition source 12, a sensor head 14 arranged inside the vacuum chamber 11, a vacuum pump 15 which maintains the inside of the vacuum chamber 11 at a predetermined vacuum atmosphere, and a measurement unit 17 which measures a film forming rate based on an output of the sensor head 14 as a sensor device and is configured to be able to control the deposition source 12. The sensor head and the measurement unit 17 constitute a film thickness monitoring device 20 for the film forming apparatus.

[0016] The deposition source 12 is configured to be capable of generating vapor (particles) of the film-forming material. In this embodiment, the deposition source 12 is electrically connected to a power supply unit 18, and constitutes an evaporation source that heats and evaporates the film-forming material to release deposition particles. The type of evaporation source is not particularly limited, and various methods such as a resistance heating type, an induction heating type, and an electron beam heating type can be applied. The film-forming material may be an organic material, a metal material, a metal compound material (e.g., a metal oxide, a metal nitride, a metal carbide, etc.), etc.

[0017] The stage 13 is configured to be capable of holding a substrate W, which is a target for film formation, such as a semiconductor wafer or a glass substrate, facing the deposition source 12.

[0018] As described later, the sensor head 14 has a built-in quartz crystal oscillator having a predetermined fundamental frequency (natural frequency). The surface of the quartz crystal oscillator is disposed in a position facing the deposition source 12, and is typically disposed in the vicinity of the stage 13.

[0019] The output of the sensor head 14 is supplied to a measurement unit 17. The measurement unit 17 is configured as a measurement device that measures the mass of the deposit (deposit) on the quartz crystal oscillator in a time series manner based on a change in the resonance frequency (resonance point) of the quartz crystal oscillator. The measurement unit 17 is further configured to measure the deposition rate of the deposition film and to control the deposition source 12 via a power supply unit 18 so that the deposition rate becomes a predetermined value.

[0020] The film forming apparatus 10 further includes a shutter 16. The shutter 16 is disposed between the deposition source 12 and the stage 13, and is configured to be capable of opening or closing an incident path of deposition particles from the deposition source 12 to the stage 13 and the sensor head 14.

[0021] The opening and closing of the shutter 16 is controlled by a control unit (not shown). Typically, the shutter 16 is closed at the start of deposition until the emission rate of the deposition particles from the deposition source 12 stabilizes. Then, when the emission rate of the deposition particles stabilizes, the shutter 16 is opened. This allows the deposition particles from the deposition source 12 to reach the substrate W on the stage 13, and a film formation process on the substrate W is started. At the same time, the deposition particles from the deposition source 12 reach the sensor head 14, and the thickness and film formation rate of the deposited film on the substrate W are monitored by the measurement unit 17.

[0022] [Measurement unit] 2 is a block diagram showing an example of the configuration of the measurement unit 17. The measurement unit 17 includes an oscillation circuit 41, a measurement circuit 42, a control unit 43, and a storage unit 44. The measurement unit 17 is configured to measure the mass of a substance (film material) attached to the quartz oscillator 140 by using the correlation between transmission to the quartz oscillator 140 and reception from the quartz oscillator 140 corresponding to the transmission, obtained by electrically sweeping around the resonant frequency of the quartz oscillator 140.

[0023] The oscillation circuit 41 and the measurement circuit 42 function as a network analyzer. The oscillation circuit 41 transmits, i.e., inputs, a sine wave signal of a predetermined frequency to the crystal oscillator 140 of the sensor head 14, thereby oscillating the crystal oscillator 140. The measurement circuit 42 is configured to receive an output signal from the crystal oscillator 140 and an input signal output from the oscillation circuit 41, and based on this, measures electrical characteristics such as the resonant frequency and phase of the crystal oscillator 140, and outputs the measured results to the control unit 43.

[0024] When a film is formed on the substrate W, the film material from the deposition source 12 also adheres to the surface of the quartz oscillator 140. The film material adhering to the surface of the quartz oscillator 140 changes the vibration frequency of the quartz oscillator 140 as a newly added mass at any time interval. The mass of the deposit on the surface of the quartz oscillator 140 correlates with the density of the deposit. In other words, by measuring the change in the vibration frequency of the quartz oscillator 140, the thickness (film thickness) of the film of the film material adhering to the surface of the quartz oscillator 140 can be obtained. The measurement unit 17 vibrates the quartz oscillator 140 by transmitting a signal, and indirectly measures the film thickness from the vibration waveform resulting from the vibration.

[0025] The measurement unit 17 uses a sinusoidal signal of a predetermined frequency as an emission signal to perform excitation. The excited quartz crystal oscillator 140 responds as a system including deposits attached to the surface. The measurement unit 17 receives the response of the quartz crystal oscillator 140, including a mechanical vibration phenomenon, as an electrical vibration waveform via the piezoelectric effect of the quartz crystal oscillator 140. The measurement unit 17 stores the waveform that is the received result, and analyzes the stored waveform. The vibration waveform of the quartz crystal oscillator 140 is stored in the memory unit 44. The measurement unit 17 extracts and outputs the film thickness included in the analysis result of the waveform.

[0026] The storage unit 44 is composed of a storage device such as a semiconductor memory, a hard disk drive, etc. The storage unit 44 stores a frequency response from the detection system including a vibration waveform of the crystal oscillator 140 when a sine wave signal of a predetermined frequency transmitted by the oscillation circuit 41 is input to the sensor head 14. The storage unit 44 further stores control programs for various processes executed by the control unit 43 described later, various parameters required for calculations, and the like.

[0027] FIG. 3 is a typical equivalent circuit of the sensor head 14. As shown in the figure, the quartz crystal unit 140 is shown as a parallel circuit of a series resonant circuit consisting of a motional capacitance C1, a motional inductance L1, and a series equivalent resistance R1, and a static capacitance C0. The series resonant circuit is an equivalent circuit including the mechanical vibration element of the quartz crystal unit 140. The static capacitance C0 includes, for example, the capacitance between the electrodes formed on the front and back surfaces of the quartz crystal unit 140, and the parasitic capacitance of a holder that holds the quartz crystal unit 140. The series equivalent resistance R1 indicates the loss components of vibration such as internal friction, mechanical loss, and acoustic loss when the quartz crystal unit 140 vibrates. In general, the higher the series equivalent resistance R1, the more difficult it is for the quartz crystal unit 140 to vibrate.

[0028] Methods for measuring the resonant frequency of the quartz crystal resonator 140 by excitation from the oscillator circuit 41 include a method for measuring the frequency at which the phase becomes zero, a method for measuring the frequency at which the susceptance, which is the imaginary component of the admittance, becomes zero, and a method for measuring the frequency at which the reactance, which is the imaginary component of the impedance, becomes zero.

[0029] [Sensor head] Next, the sensor head 14 as the sensor device of this embodiment will be described in detail. Fig. 4 is a schematic cross-sectional view showing the configuration of the sensor head 14, Fig. 5 is an exploded cross-sectional view thereof, and Fig. 6 is an enlarged cross-sectional view of a main portion thereof.

[0030] The sensor head 14 of the present embodiment includes a piezoelectric vibrator 50, a ring-shaped support 60, a connection terminal group 70, a cover member 80, and a base member 90.

[0031] (Piezoelectric vibrator) The piezoelectric vibrator 50 corresponds to the quartz crystal vibrator 140. The piezoelectric vibrator 50 has a vibrator body 51, a front electrode 52, a rear electrode 53, a front electrode terminal portion 520, and a rear electrode terminal portion 530, as shown in FIG.

[0032] The vibrator body 51 is a disk-shaped piezoelectric substrate made of quartz or the like. The vibrator body 51 has a front surface which is the upper surface side in FIG. 6 and a back surface which is the lower surface side. The front surface electrode 52 is formed on the front surface of the vibrator body 51. The back surface electrode 53 is formed on the back surface of the vibrator body 51.

[0033] The material constituting the vibrator body 51 is, for example, a piezoelectric element such as an AT-cut crystal vibrator, an SC-cut crystal vibrator, an IT-cut crystal vibrator, an FC-cut crystal vibrator, or an RC-cut crystal vibrator. The fundamental frequency of the vibrator body 51 is, for example, 3 MHz or more and 40 MHz or less, and is 15 MHz in this embodiment. When the attached mass is minute, the fundamental frequency of the crystal vibrator is set to a high value in order to increase the detection sensitivity of the mass. For example, when detecting a minute mass present in the air, a crystal vibrator having a fundamental frequency of, for example, several tens of MHz is selected.

[0034] The front electrode 52 and the back electrode 53 are excitation electrodes that vibrate the vibrator body 51 at its resonant frequency, and are typically made of a metal film such as Au, Ag, Pt, or Al. Metal films such as Au and Pt have better corrosion resistance than Al and the like, and can protect the front electrode 52 and the back electrode 53 from a corrosive environment. The front electrode 52 is patterned into an arbitrary shape on the surface of the vibrator body 51. The back electrode 53 is disposed at a position opposite the front electrode 52 across the vibrator body 51, and is patterned into a shape corresponding to the shape of the front electrode 52.

[0035] The surface electrode terminal portion 520 is formed on the surface of the vibrator body 51, and is connected to the surface electrode 52 via a connecting wire 52c. The surface electrode terminal portion 520 is typically formed at a predetermined position on the periphery of the surface of the vibrator body 51. The connecting wire 52c is formed linearly on the surface of the vibrator body 51 so as to connect between the surface electrode 52 and the surface electrode terminal portion 520. The surface electrode terminal portion 520 and the connecting wire 52c are formed of the same material and with the same thickness as the surface electrode 520.

[0036] The rear electrode terminal portion 530 is formed on the surface of the vibrator body 51, and is connected to the rear electrode 53 via a connecting wire 53c. The rear electrode terminal portion 530 is typically formed at a predetermined position on the periphery of the surface of the vibrator body 51. The connecting wire 53c is formed by folding back at the edge of the vibrator body 51 on the front and rear surfaces of the vibrator body 51 so as to connect between the rear electrode 53 and the rear electrode terminal portion 530. The rear electrode terminal portion 530 and the connecting wire 53c are formed of the same material and with the same thickness as the rear electrode 530.

[0037] The front electrode 52 and the back electrode 53 are each composed of a plurality of electrodes. In the piezoelectric vibrator 50 of this embodiment, two front electrodes 52 and two back electrodes 53 are arranged on the front and back surfaces of the vibrator body 51, as shown in FIG.

[0038] 7 is a top view of the piezoelectric vibrator 50. The surface electrode 52 has a first surface electrode portion 521 and a second surface electrode portion 522. The first surface electrode portion 521 and the second surface electrode portion 522 are disposed apart from each other and are formed in a symmetrical shape with the same area. A surface electrode terminal portion 520 is provided for each of the first surface electrode portion 521 and the second surface electrode portion 522, and each is disposed at a different position on the periphery of the surface of the vibrator body 51.

[0039] The back electrode 53 has a first back electrode portion 531 and a second back electrode portion 532. The first back electrode portion 531 is disposed at a position facing the first front electrode portion 521 across the vibrator body 50, and the second back electrode portion 532 is disposed at a position facing the second front electrode portion 522 across the vibrator body 50. The first back electrode portion 531 and the second back electrode portion 532 are formed to have the same area and a shape symmetrical to the first front electrode portion 521 and the second front electrode portion 522. The back electrode terminal portion 530 is provided for each of the first back electrode portion 531 and the second back electrode portion 532, or is provided in common with the first back electrode portion 531 and the second back electrode portion 532.

[0040] (Support) The support 60 is a circular plate member having a hollow portion 61, and is made of an electrically insulating material such as a ceramic material (e.g., quartz). By making the support 60 out of quartz, it is possible to reduce the difference in thermal expansion coefficient with the piezoelectric vibrator 50 (vibrator body 51) made of quartz.

[0041] The hollow portion 61 is a circular through-hole formed in the center of the support 60, and its inner diameter is smaller than the diameter of the piezoelectric vibrator 50. The support 60 is disposed opposite the surface of the piezoelectric vibrator 50, and has a support surface 62 that supports the peripheral portion of the surface of the piezoelectric vibrator 50. The support surface 62 supports the piezoelectric vibrator 50 so that it can vibrate via a connection terminal group 70. Note that it is preferable that the support 60 supports the piezoelectric vibrator 50 so as not to damage the symmetry of the first and second surface electrode portions 521, 522.

[0042] The support 60 exposes the surface electrode 52 of the piezoelectric vibrator 50 to the outside through the hollow portion 61. In this embodiment in which the surface electrode 52 is divided into a plurality of electrode portions, the support 60 is configured so that only the first surface electrode portion 521 is exposed to the outside through the hollow portion 61.

[0043] In this embodiment, the support 60 has a shielding plate 63 for shielding the second surface electrode portion 522, as shown in Fig. 4. The shielding plate 63 is a plate-shaped member fixed to the inner circumferential surface of the hollow portion 61, and is disposed in parallel to the second surface electrode portion 522 at a position facing the second surface electrode portion 522 of the piezoelectric vibrator 50 supported by the support member 60 (see Figs. 4 and 9). The shielding plate 63 is made of a material that allows the transmission of heat rays emitted from the deposition source 12, and the details thereof will be described later. The shielding plate 63 is not limited to being provided in the hollow portion 62, and may be provided on the support surface 62 or on the upper surface of the support 60 opposite to the support surface 62, for example.

[0044] The support 60 further has a fitting portion 64 (see FIG. 5) into which a tip portion of a holding pin 83 for holding the support in a housing portion 81 of a cover member 80 described later fits. The fitting portion 64 is formed as a bottomed hole portion (recess), and at least one fitting portion 64 is provided on the outer circumferential surface of the support 60. This allows the support 60 to be stably held in the housing portion 81 of the cover member 80, and allows the support 60 and the piezoelectric vibrator 50 to be positioned in the circumferential direction relative to the cover member 80.

[0045] (Connection terminal group) The connection terminal group 70 is disposed between the support surface 62 of the support 60 and the peripheral portion of the front surface of the vibrator body 50. The connection terminal group has a first conductor layer 71 and a second conductor layer 72. The first conductor layer 71 is electrically and elastically connected to the front surface electrode terminal portion 520. The second conductor layer 72 is electrically and elastically connected to the back surface electrode terminal portion 530.

[0046] 6, the first conductor layer 71 has a first metallic land portion 711 formed on the support surface 62 of the support 60, and a conductive first elastic portion 712 provided between the first land portion 711 and the front surface electrode terminal portion 520. The second conductor layer 72 has a second metallic land portion 721 formed on the support surface of the support 60, and a conductive second elastic portion 722 provided between the second land portion 721 and the back surface electrode terminal portion 530.

[0047] The first land portion 711 and the second land portion 721 are made of a metal foil such as a copper foil or an aluminum foil. From the viewpoint of improving corrosion resistance, the land portions 711 and 721 are preferably made of a metal film such as Au or Pt. The first land portion 711 and the second land portion 721 are formed by patterning the metal foil formed on the support surface 62 of the support body 60 into a predetermined shape.

[0048] Fig. 8 is a bottom view of the support 60 as viewed from the piezoelectric vibrator 50. Fig. 9 is a top view of the piezoelectric vibrator 50 as viewed from the support 60.

[0049] In this embodiment, the front electrode 52 has first and second front electrode portions 521 and 522, and two front electrode terminal portions 520 corresponding thereto. The back electrode 53 has first and second back electrode portions 531 and 532, and two back electrode terminal portions 530 corresponding thereto. For this reason, as shown in FIG. 8, the first land portion 711 is provided at two locations corresponding to each front electrode terminal portion 520, and the second land portion 721 is provided at two locations corresponding to each back electrode terminal portion 530. These first land portion 711 and second land portion 721 are arranged at equal angular intervals on the support surface 62 along the circumferential direction of the support 60 as shown in the same figure.

[0050] The first elastic portion 712 and the second elastic portion 722 are composed of a conductive resin material, a metal coil, etc. The first elastic portion 712 is provided between the first land portion 711 and each of the front surface electrode terminal portions 520, and the second elastic portion 722 is provided between the second land portion 721 and each of the rear surface electrode terminal portions 530. The first elastic portion 712 and the second elastic portion 722 electrically and elastically connect the piezoelectric vibrator 50 to the support body 60 so as to be able to vibrate.

[0051] In determining the elastic modulus of the first elastic part 712 and the second elastic part 722, it is desirable to measure the temperature drift of the resonance frequency (for example, the first resonance frequency) and experimentally determine it so that the required measurement accuracy can be obtained, but it may also be determined by computer simulation. In either case, there is no problem as long as the stress applied to the piezoelectric vibrator 50 is dominated by the voltage (electric field) generated between the front and back electrodes 52, 53. In other words, the elastic modulus should be determined so that the effect of the mechanical stress (thermal stress) is, for example, 1 / 100 or less of the alternating electric field. If the elastic modulus is determined in this manner, errors caused by thermal stress can be suppressed even in an environment with temperature changes, and the required measurement accuracy can be achieved.

[0052] If the elastic modulus of each of the elastic parts 712, 722 is extremely low or if the elastic modulus of each of the elastic parts 712, 722 differs, stable resonance may not occur (a sudden transition of the resonance point may occur), and this may need to be avoided. In such a case, it is sufficient to provide three or more elastic parts, and to provide the elastic parts symmetrically (line symmetrically or equally angularly divided from the center of the piezoelectric vibrator 50). In this case, since the elastic parts represent a mechanical configuration, there is no need to ensure electrical continuity.

[0053] (Cover material) The cover member 80, together with a base member 90 described later, is configured as an exterior member of the sensor head 14. The sensor head 14 is placed in the vacuum chamber 11 with the cover member 80 facing the deposition source 12. The cover member 80 is, for example, a disk-shaped metal part, and has an accommodation portion 81 that accommodates the support 60, and an opening portion 82 that communicates with the hollow portion 61 of the support 60 accommodated in the accommodation portion 61.

[0054] The accommodation portion 81 is a circular recess capable of accommodating the support 60. The depth of the accommodation portion 81 is not particularly limited, and in this embodiment, as shown in FIG.

[0055] The cover member 80 further has a retaining pin 83 for retaining the support 60 in the accommodation portion 81. The retaining pin 83 is inserted into an insertion hole 85 (see FIG. 5) that penetrates a part of the cover member 80 in the radial direction. The tip of the retaining pin 83 protrudes into the accommodation portion 81 and fits into a fitting portion 64 formed on the outer circumferential surface of the support 60 accommodated in the accommodation portion 81. The retaining pin 83 is constantly biased toward the accommodation portion 81 by a spring member 84 installed on the outer circumferential portion of the cover member 80. This allows the support 60 to be stably held in the accommodation portion 81. The number of retaining pins 83 is not limited to one, and may be provided in multiple locations.

[0056] The opening 82 is a through hole formed to communicate with a part of the bottom of the storage section 81, and communicates with the hollow section 61 of the support 60. The opening 82 has an inner diameter smaller than the outer shape of the support 60, and in this embodiment, is formed with a diameter substantially equal to the inner diameter of the hollow section 61. The opening 82 guides the deposition particles incident from the deposition source 12 to the piezoelectric vibrator 50 through the hollow section 61. The outer surface of the opening 82 is formed with a tapered surface 82a as shown in FIG. 4 in order to increase the incidence efficiency of the deposition material.

[0057] (Base material) The base member 90 is, for example, a disk-shaped synthetic resin (for example, PEEK (polyether ether ketone)) part having an upper surface 93 that abuts against the lower surface 86 of the case member 80, and is configured to be attachable to and detachable from the case member 80 by a ball plunger or a clamp member (not shown). The base member 90 has a bottomed recess 91 capable of accommodating the piezoelectric vibrator 50, and a plurality of metal contacts 92 that penetrate the bottom of the recess 91. The base member 90 may be configured as a metal part, in which case, an insulating coating is applied to the outer circumferential region of each contact 92 that contacts the recess 91 of the base member 90 (the outer circumferential region other than the tip portion).

[0058] The recess 91 forms a space large enough to accommodate the piezoelectric vibrator 50 supported on the support surface 62 of the support 60. In this embodiment, the recess 91 is formed to a size such that the entire support surface 62 of the support 60 held by the cover member 80 is exposed within the recess 91.

[0059] The multiple contacts 92 are inserted into insertion holes 94 that penetrate the bottom of the recess 91 in the thickness direction. The multiple contacts 92 include a first contact 921 and a second contact 922. The first contact 921 abuts against the first land portion 711 of the first conductor portion 71, and the second contact 922 abuts against the second land portion 721 of the second conductor portion 72.

[0060] As described above, in this embodiment, two each of the first conductor layers 71 and the second conductor layers 72 are provided corresponding to the first and second front surface electrode portions 521, 522 and the first and second back surface electrode portions 531, 532. Therefore, two each of the first contactors 921 and the second contactors 922 are also provided, for a total of four contactors arranged at equal angular intervals on the periphery of the piezoelectric vibrator 50 as shown in Fig. 8. Each contactor 92 is connected to the oscillation circuit 41 (Fig. 2) of the measurement unit 17.

[0061] A pogo pin equipped with a spring member 75 is used for each contactor 92. The spring member 95 biases the contactor 92 toward the piezoelectric vibrator 50. When the base member 90 is attached to the cover member 80 as shown in FIG. 4, each contactor 92 is pressed against the first and second land portions 711, 721 by the biasing force of the spring member 95. This electrically connects each electrode portion 521, 522, 531, 532 of the piezoelectric vibrator 50 to the oscillation circuit 41 of the measurement unit 17.

[0062] Each contactor 92 is desirably in the shape of a probe pin, for example. This is because the tip is needle-shaped (point-shaped on the contact surface) and the contact area is extremely small, so that electrical continuity can be ensured with a desired contact pressure with a small biasing force, and each contactor 92 is not constrained (microscopic slippage can be expected) even if thermal expansion occurs in the support 60 or base member 90. As a result, the piezoelectric vibrator 50 is similarly not affected, and a stable film formation rate and stable film thickness measurement can be achieved.

[0063] Furthermore, according to this embodiment, the support 60 that supports the piezoelectric vibrator 50 is arranged with its support surface 62 facing the base member 90, and therefore the following advantageous effects are obtained compared to a structure in which the support surface 62 is arranged on the cover member 80 side (hereinafter also referred to as the comparative example). First, since the contactors 921, 922 contact the conductor layers 71, 72 (land portions 711, 721) formed on the support surface 62 of the support body 60, the wiring length between the contactors 921, 922 and each surface electrode portion 521, 522 of the piezoelectric vibrator 50 can be made shorter than in the comparative example, thereby suppressing the inclusion of noise in the detection signal from the piezoelectric vibrator 50. Secondly, since the deposition particles reach the surface (first surface electrode portion 521) of the piezoelectric vibrator 50 through the hollow portion 61 of the support 60, the hollow portion 61 can achieve a collimator function for the deposition particles incident on the piezoelectric vibrator 50. Thirdly, since a shielding plate 63 for blocking the incidence of deposition particles on the second surface electrode portion 522 can be arranged on the support 60, there is no need to adopt a redundant configuration when installing the shielding plate 63, as compared to the comparative example.

[0064] [Thickness monitoring device operation] Next, the operation of the film thickness monitoring device equipped with the sensor head 14 configured as above will be described.

[0065] When starting a film formation process by the film formation apparatus 10, the control unit 43 oscillates the piezoelectric vibrator 50 (quartz crystal vibrator 140) of the sensor head 14. At this time, the oscillation circuit 41 of the measurement unit 17 alternately applies a voltage of a predetermined frequency between the first front electrode portion 521 and the first back electrode portion 531 and between the second front electrode portion 522 and the second back electrode portion 532, and excites the piezoelectric vibrator 50 by the potential difference.

[0066] When the film formation process on the substrate W starts, the shutter 16 is opened, and deposition particles of the film formation material are incident from the deposition source 12 toward the substrate W. At the same time, the deposition particles emitted from the deposition source 12 are incident on the sensor head 14 and adhere to the surface of the piezoelectric vibrator 50 through the opening 82 of the cover member 80 and the hollow portion 61 of the support 60. The deposition particles that have entered the opening 82 are prevented from reaching the second surface electrode portion 522 by the shielding plate 63, so that they adhere only to the first surface electrode portion 521.

[0067] The measurement circuit 42 measures the resonance frequency (hereinafter also referred to as the first resonance frequency) of the piezoelectric vibrator 50 when a voltage of the predetermined frequency is applied between the first front electrode portion 521 and the first back electrode portion 531. The measurement circuit 42 also measures the resonance frequency (hereinafter also referred to as the second resonance frequency) of the piezoelectric vibrator 50 when a voltage of the predetermined frequency is applied between the second front electrode portion 522 and the second back electrode portion 532. Since deposition particles are deposited on the first front electrode portion 521 and deposition particles are not deposited on the second front electrode portion 522, the amount of change in the first resonance frequency due to the deposited mass becomes larger over time than the second resonance frequency.

[0068] On the other hand, during the film formation, the piezoelectric vibrator 50 is subjected to thermal radiation from the deposition source 12. Since the quartz crystal vibrator (vibrator body 51) constituting the piezoelectric vibrator 50 has temperature characteristics, the resonant frequency tends to shift due to temperature drift caused by changes in the amount of heat input. Therefore, the changes in the first and second resonant frequencies include not only those caused by mass changes due to the adhesion of deposition particles, but also frequency changes caused by the temperature characteristics of the piezoelectric vibrator 50 due to thermal radiation from the deposition source 12. In other words, the first resonant frequency includes two changes, namely, the amount of change caused by the deposited mass and the frequency change caused by the temperature characteristics of the piezoelectric vibrator 50 due to thermal radiation, while the change in the second resonant frequency is not caused by the above-mentioned mass change, and the frequency change caused by the temperature characteristics of the piezoelectric vibrator 50 is dominant. In addition, as described above, since the first surface electrode portion 521 and the second surface electrode portion 522 are configured to maintain a geometric similarity relationship to the extent possible, it is considered that the frequency change caused by the temperature characteristics of the piezoelectric vibrator 50 is the same for the first surface electrode portion 521 and the second surface electrode portion 522.

[0069] Therefore, the control unit 43 calculates a first change amount, which is the amount of change per unit time of the first resonance frequency, and a second change amount, which is the amount of change per unit time of the second resonance frequency, and detects the film thickness of the deposit (evaporation film) deposited on the surface of the piezoelectric vibrator 50 from the difference between the first change amount and the second change amount. At this time, since the first change amount and the second change amount are equally affected by the temperature of the piezoelectric vibrator 50, the influence of the temperature is cancelled by taking the difference between the two. As a result, it is possible to calculate only the amount of change in the resonance frequency based on the mass change, and therefore it is possible to detect only the amount of change in the resonance frequency based on the mass change of the piezoelectric vibrator 50 with high accuracy.

[0070] Furthermore, since the effect of the temperature of the piezoelectric vibrator 50 is cancelled by taking the difference between the first change amount and the second change amount, it is possible to detect only the change amount of the resonance frequency based on the change in mass of the piezoelectric vibrator 50 with high accuracy without requiring a compensation circuit for compensating for changes in the environmental temperature. Moreover, not only for the piezoelectric vibrator 50, but also for devices such as the oscillation circuit 41 and the measurement circuit 42 that are subject to fluctuations in the environmental temperature, it is possible to perform highly accurate film thickness measurement or rate measurement without having to consider temperature compensation for these.

[0071] [Details of the shielding plate] Here, depending on the heat ray transmission characteristics of the shielding plate 63 that shields the second surface electrode portion 522, there may be variations in the amount of heat rays incident on the first surface electrode portion 521 and the second surface electrode portion 522, which may prevent highly accurate film thickness detection. This problem is more likely to occur under film formation conditions in which the rate of mass increase per unit time is extremely small, such as during ultra-low rate film formation in which the film formation rate is extremely low.

[0072] Specifically, when the variation in the film formation rate (mass increase rate) caused by the amount of incident heat rays reaches about 1 / 100 to 1 / 10 of the film formation rate during ultra-low rate film formation, the measurement accuracy required for a sensor device for measuring the film formation rate may not be achieved. In other words, when measuring ultra-low rate film formation, the variation caused by the amount of incident heat rays is noted as a technical issue that should be removed as background noise.

[0073] 10 shows an experimental result showing the time change (rate conversion value) of the frequency of the piezoelectric vibrator 50 when the temperature of the deposition source 12 is increased stepwise (in a step input manner or a ramp input manner). In this experiment, no film forming material is loaded into the deposition source 12, and only radiant heat is incident on the piezoelectric vibrator 50 from the deposition source 12. Therefore, the fluctuation of the rate conversion value depends solely on the temperature characteristics of the piezoelectric vibrator 50.

[0074] In this experimental example, it is ideal that the rate conversion value remains stable at 0 regardless of the temperature. However, when the deposition source temperature is 200°C, the rate conversion value remains stable at 0, whereas when the temperature is increased to 400°C, 600°C, and 700°C, the rate conversion value fluctuates significantly, and the higher the temperature, the more significant the problem becomes. In addition, even after one hour at a temperature of 400°C or higher, the rate conversion value does not return to 0. For this reason, the temperature characteristics of the piezoelectric vibrator 50 cannot be canceled during actual film formation, and the rate conversion value appears to shift due to the effect of radiant heat from the deposition source 12.

[0075] What should be noted here is that the value shifts in an impulse response manner during the temperature rise, i.e., in the time domain where the incidence of heat rays increases, and then in the subsequent time domain, the value shifts in a time-lag manner, and it can be seen that the problem becomes more pronounced when the incidence of heat rays increases. In other words, from the viewpoint of performing continuous measurements as a sensor device for measuring the deposition rate, the phenomenon of impulse response shifts should be removed with priority over time-lag shifts. One of the reasons for this is that time-lag value fluctuations can be dealt with by numerical calculation processing, compared to impulse response fluctuations.

[0076] FIG. 11 is a conceptual diagram showing the lower limit of measurement in the deposition apparatus used in the experiment of FIG. 10, where the horizontal axis is the deposition source temperature and the vertical axis is the deposition rate. In this experimental example, the deposition rate is 0.01 Å / s or more when the deposition source temperature is 400° C. or less, 0.015 Å / s or more when the deposition source temperature is 600° C., and 0.04 Å / s or more when the deposition source temperature is 700° C. In other words, the rate range below the lower limit of measurement at each temperature includes the influence of radiant heat from the deposition source by 10% or more, so it is difficult to stably perform high-precision rate measurement in the rate range. In other words, the measurement environment when performing rate measurement with the required accuracy is a condition in which the ratio of background noise caused by radiant heat, i.e., the amount of incident heat rays, is high, so that the measurement accuracy required for a sensor device for measuring a deposition rate may not be achieved.

[0077] One of the reasons why the rate conversion value is affected by the temperature characteristics of the piezoelectric vibrator 50 is the infrared transmission characteristics of the material that constitutes the shielding plate 63. In general, quartz has a very high transmittance of 80% or more for infrared rays with wavelengths of approximately 4 μm or less, but the infrared transmittance tends to drop sharply in wavelength bands exceeding 4 μm.

[0078] On the other hand, heat radiated from a heat source such as a deposition source contains infrared rays in a wide range of wavelengths, and the peak wavelength shifts to the shorter wavelength side as the temperature of the heat source increases (Wien's Displacement Law). For example, when the temperature of the heat source is 427°C (700K), the peak wavelength of the radiant heat from the heat source is about 4μm, and the wavelength band of the radiant heat from the heat source has a spread of about 1 / 3 of the peak wavelength on the short wavelength side and about 5 times the peak wavelength on the long wavelength side.

[0079] Thus, the quartz shielding plate 63 has a high transmittance for infrared rays of the peak wavelength and its shorter wavelength side, but has a very low transmittance for infrared rays of the band longer than the peak wavelength. For this reason, the radiant heat contained in the infrared band of the longer wavelength side that should reach the piezoelectric vibrator 50 is absorbed by the shielding plate 63, causing a transmission loss, and as a result, a difference in the amount of heat input between the vibrator area shielded by the shielding plate 63 and the vibrator area that is not shielded occurs, which is thought to have a significant effect on the rate conversion value. In particular, when the incidence of heat rays increases, the low transmittance for infrared rays of the longer wavelength side band is thought to cause the shielding plate 63 to become a resistance element in the thermal circuit, causing an impulse response shift phenomenon.

[0080] Therefore, in this embodiment, the shielding plate 63 is made of a material having a transmittance of 40% or more for infrared rays (radiant heat) in a wavelength range of 0.5 to 3 times the peak wavelength of the infrared rays incident on the hollow portion 61 of the support 60. As such a material, for example, a material having a transmittance of 40% or more for infrared rays in a wavelength range of about 0.8 μm to about 13 μm is preferable, and examples thereof include Si (silicon), Ge (germanium), ZnS (zinc sulfide), and ZnSe (zinc selenide). FIG. 12 shows the infrared transmission characteristics of Si, Ge, ZnS, and ZnSe. In this embodiment, Si is used as the constituent material of the shielding plate 63.

[0081] The thickness of the shielding plate 63 is not particularly limited, but is preferably as thin as possible to enhance the infrared transmission characteristics, for example, 0.5 mm or less. The shielding plate 63 is also preferably thick enough to ensure a suitable rigidity (self-supporting property) to maintain flatness, for example, 0.05 mm or more. By adopting the above-mentioned embodiment, the heat transmission, i.e., the thermal resistance, of the shielding plate 63 can be made to have the desired characteristics, so that it is possible to reduce the difference when the incidence of heat rays increases.

[0082] 13 shows the results of an experiment showing the time change in the resonance frequency of the piezoelectric vibrator 50 depending on the material and thickness of the shielding plate 63. In this experiment, the pressure in the vacuum chamber 11 was set to 1.0×10 -5 The vapor deposition source 12, which was not charged with a film forming material, was heated to 700° C. The shielding plate 63 used was a quartz (qtz) plate having a thickness of 1 mm and 0.06 mm, and a Si plate having a thickness of 0.5 mm and 0.06 mm.

[0083] As shown in FIG. 13, when the piezoelectric vibrator 50 is irradiated with radiant heat from the deposition source 12 at time 0, the rise of the change in the resonant frequency of the piezoelectric vibrator 50 due to the temperature characteristics is delayed by just under one minute when the shielding plate is a quartz plate with a thickness of 1 mm, and the amount of change in frequency is small, compared to when there is no shielding plate. This is considered to be because the transmission loss of infrared rays on the longer wavelength side than the peak wavelength of the radiant heat is very large in the quartz shielding plate. For this reason, the deposition rate of the deposition film cannot be stably detected during heating, i.e., when the temperature increases (especially when the temperature rise is not continuous and the rate of change is specific). The reason for the delay in the rise is considered to be that the shielding plate absorbs the radiant heat once, the temperature of the shielding plate itself rises as a result of the absorption, and the radiation from the shielding plate with the increased temperature is given to the piezoelectric vibrator. This indicates that the heat capacity of the shielding plate is a factor in the delay (the thickness of the shielding plate 63 is considered to be a factor in the delay).

[0084] In contrast, when the shielding plate was a quartz plate with a thickness of 0.06 mm, and a Si plate with a thickness of 0.5 mm and 0.06 mm, the frequency change was confirmed at the same timing as when there was no shielding plate. It was also confirmed that the amount of change in the resonant frequency caused by the temperature characteristics of the piezoelectric vibrator 50 was larger than in the case of a quartz plate with a thickness of 1 mm. This is thought to be because the shielding plate 63 made of these materials has good transmission characteristics for infrared rays with wavelengths longer than the peak wavelength of the radiant heat. It was also confirmed that the Si plate has better transmission characteristics for radiant heat than the quartz plate, even with the same thickness of 0.06 mm.

[0085] In this embodiment, when the amount of change over time in the resonant frequency of the piezoelectric vibrator 50 when an AC voltage is applied between the first surface electrode portion 521 and the first back electrode portion 522 is defined as a first change amount (amount of change in resonant frequency when there is no shielding plate) and the amount of change over time in the resonant frequency of the piezoelectric vibrator 50 when the above AC voltage is applied between the second surface electrode portion 522 and the second back electrode portion 532 is defined as a second change amount (amount of change in resonant frequency when there is a shielding plate), the shielding plate 63 is configured so that the ratio (ΔF0) of the second change amount to the first change amount when infrared light is incident on the hollow portion 61 is 40% or more, more preferably 60% or more.

[0086] 14A and 14B show the change in ΔF0 over time when the shielding plate 63 is a quartz plate with a thickness of 1 mm and 0.062 mm, respectively. As shown in the figures, for both quartz plates, ΔF0 at the beginning of the incidence of radiant heat is less than 40%, so the deposition rate of the evaporated film cannot be stably detected at the start of deposition.

[0087] 15A to 15C show the change in ΔF0 over time when the shielding plate 63 is a Si plate with a thickness of 0.5 mm, 0.05 mm, and 0.06 mm, respectively. As shown in the figures, for all of the quartz plates, ΔF0 is 40% or more from the beginning of the incidence of radiant heat, making it possible to stably and accurately detect the deposition rate of the evaporated film from the start of deposition.

[0088] In this embodiment, a Si plate having a thickness of 0.5 mm or less is used as the shielding plate 63. This increases the transmittance of almost the entire wavelength range of the radiant heat incident on the shielding plate 63, and makes it possible to reduce the difference in the amount of heat rays incident on the first surface electrode portion 521 and the second surface electrode portion 522. This enables stable and highly accurate rate detection even under film formation conditions in which the mass increase rate per unit time is extremely small, such as during ultra-low rate film formation in which the film formation rate is extremely low.

[0089] The shielding plate 63 may be a Si plate having a thickness of 0.03 mm to 1 mm. This allows the ratio ΔF0 to be 40% or more. In addition, since such a shielding plate 63 has a rigidity that allows it to maintain flatness, it can be stably installed so as to be parallel to the surface of the piezoelectric vibrator 50.

[0090] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made thereto.

[0091] For example, in the above embodiment, an example has been described in which the sensor device according to the present invention is applied as a film thickness sensor for a vacuum deposition apparatus, but the application is not limited to vacuum deposition apparatuses, and the sensor device can also be applied as a film thickness sensor for other film forming apparatuses such as a sputtering apparatus or a CVD apparatus.

[0092] In the above embodiment, the shielding plate 63 is arranged parallel to the surface of the piezoelectric vibrator 50, but this is not limited thereto. For example, as shown in Fig. 16, one end of the shielding plate 63 located on the center side of the hollow portion 61 may be inclined so as to approach the piezoelectric vibrator 50. In this way, it is possible to prevent the deposition particles from getting around to the second surface electrode portion 522. The shielding plate 63 is not limited to a plate-shaped member, and may be formed in an L-shaped cross section by bending one end of the shielding plate 63 located on the center side of the hollow portion 61 toward the piezoelectric vibrator 50 as shown in Fig. 17, thereby obtaining the same effect as the configuration example shown in Fig. 16.

[0093] Here, in the case of the configuration example of FIG. 16, since the transmission path of the heat rays is extended, it is more preferable to make the cross section L-shaped as shown in FIG. 17. In the configuration example shown in FIG. 17, the shielding plate portion on the opening 82 side of the cover member 80 may function as a support for supporting the shielding plate 63 in the hollow portion 61 without considering the transmission of heat rays. In this case, even if the shielding plate 63 is thin, unexpected damage of the shielding plate 63 is prevented, which is better, and a thinner shielding plate 63 that is more easily transmitted can be used. Furthermore, the bent end of the shielding plate 63 may reach the support surface 62 of the support body 60, or may protrude toward the piezoelectric vibrator 50 from the support surface 62 to the extent that it does not contact the piezoelectric vibrator 50. This enhances the effect of preventing the deposition particles from wrapping around the second surface electrode portion 522.

[0094] Furthermore, the present invention is not limited to a film thickness sensor to which particles adhere in the gas phase, such as for a film forming apparatus, but can also be applied to a sensor device that measures a change in resonance frequency based on the adhesion (or adsorption) of a specific component in a solution (in the liquid phase) to detect the concentration of the component in the solution. Furthermore, the present invention can be applied to detection of minute particles and contaminants. The present invention can also be applied to a sensor device that detects the concentration of a specific gas component in the gas phase. In this case, a SAW element, an FBAR element, or the like can be applied as the piezoelectric vibrator.

[0095] Furthermore, in the above embodiment, the fitting portion 64 into which the retaining pin 83 fits is formed on the outer circumferential surface of the support 60, but the formation of the fitting portion 64 may be omitted. In this case, the restraining force of the retaining pin 83 on the support 60 is reduced, so that the thermal stress acting on the support 60 can be alleviated. [Explanation of symbols]

[0096] 10…Film deposition equipment 11…Vacuum chamber 12...evaporation source 14...Sensor head (sensor device) 17…Measuring unit 20...Film thickness monitor 41...Oscillation circuit 42…Measurement circuit 43...Control section 50...Piezoelectric vibrator 51... Transducer body 52…Surface electrode 53…Back electrode 60...Support 61...Hollow part 62…support surface 63…shielding plate 70...Connection terminals 71...first conductor layer 72...Second conductor layer 80...Cover member 81…Storage section 82…Opening 83…Retaining pin 90...Base material 92...Contact 140...Crystal resonator 520…Terminal section for surface electrode 521...first surface electrode portion 522...second surface electrode portion 530...Terminal section for back electrode 531...first back electrode portion 532...second back electrode portion 711…First Land Section 712...First elastic portion 721…Second Land Section 722...Second elastic portion 921…First contact 922…Second contact

Claims

1. a piezoelectric vibrator having a vibrator body, first and second surface electrode portions formed on a surface of the vibrator body, and first and second back surface electrode portions formed on a back surface of the vibrator body and facing the first and second surface electrode portions, respectively; a support body having a hollow portion exposing a surface of the vibrator body, a support surface supporting the piezoelectric vibrator so as to be able to vibrate, and a shielding plate exposing the first surface electrode portion to the hollow portion and shielding the second surface electrode portion from the hollow portion; Equipped with The shielding plate is made of a material having a transmittance of 40% or more for infrared rays in a wavelength range of 0.5 to 3 times the peak wavelength of the infrared rays incident on the hollow portion. Sensor device.

2. The sensor device according to claim 1 , a first change amount is a time change amount of the resonant frequency of the piezoelectric vibrator when an AC voltage is applied between the first front electrode portion and the first back electrode portion, and a second change amount is a time change amount of the resonant frequency of the piezoelectric vibrator when the AC voltage is applied between the second front electrode portion and the second back electrode portion, and a ratio of the second change amount to the first change amount in a state in which infrared rays are incident on the hollow portion is 40% or more. Sensor device.

3. The sensor device according to claim 2, The ratio of the second change amount to the first change amount is 60% or more. Sensor device.

4. The sensor device according to any one of claims 1 to 3, The shielding plate is a silicon plate having a thickness of 0.5 mm or less. Sensor device.

Images